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I bought 1000 meters of wire to settle a physics debate

AlphaPhoenix · Youtube · 437 HN points · 6 HN comments
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Youtube Summary
I constructed the Veritasium electricity thought experiment in real life to test the result.

If you were watching my community posts a month ago, the day that Derek over on Veritasium posted his video about electricity misconceptions, you saw me obsess over that problem a bit too much and immediately use it as the excuse I've been looking for for years to own my own oscilloscope. Instead of two light-seconds of wire, I used about 3 light-microseconds of wire, but it was PLENTY to resolve exactly what is happening in this circuit. I hope you enjoy the analysis!

Thanks to Derek at Veritasium for his blessing to make a real-world version of his gedanken experiment. If you haven't seen his video yet, you might want to go watch that for context, and I also highly recommend ElectroBOOM's video on the topic and EEVBlog's video on the topic. Electroboom's video has some simulated scope traces extremely close to what I saw IRL, and a REALLY fantastic animation (8:27) of him waving an electron around in his hand, shedding magnetic fields as it moves (Even though I ignore magnetic fields in this video - I'm trying to think of a test to find out if they matter).

Veritasium https://youtu.be/bHIhgxav9LY
ElectroBOOM https://youtu.be/iph500cPK28
EEVBlog https://youtu.be/VQsoG45Y_00


Music Credits, etc.:
I Dunno by grapes is licensed under a Creative Commons Attribution license (https://creativecommons.org/licenses/by/3.0/)
http://ccmixter.org/files/grapes/16626
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Hacker News Stories and Comments

All the comments and stories posted to Hacker News that reference this video.
This sounds similar in some ways to the discussion that arose between AlphaPhoenix and Veritasium YouTube channels concerning the speed of electrons along a closed loop of wire.

https://youtu.be/2Vrhk5OjBP8 With a relevant illustration at 9:41 at where I think these topics intersect conceptually.

You might get a kick out of this: “I bought 1000 meters of wire to settle a physics debate” https://m.youtube.com/watch?v=2Vrhk5OjBP8
I believe this is the same video, the author theorized (probably correctly) that it was because there was residual 'power' on the wire, as it acts like a giant capacitor, among other things. this is because the wire that immediately showed up was extremely small and dissipated very quickly. https://www.youtube.com/watch?v=2Vrhk5OjBP8
Jan 13, 2022 · pja on 5.5 mm in 1.25 nanoseconds
His presentation is not very clear & imo the way he answers the question is not actually helpful in actually understanding what’s going on, but he is correct that current will flow in the far side almost immediately. As is made clearer in the documents he shared which contain his discussions with actual physicists, that current will be much smaller than the final current that flows all the way round the circuit, but it is there nevertheless. (In fact that current will initially flow whether or not the two halves of the flat ring are connected - if you think about it things have to work like this, because the middle of the system cannot “know” whether the far ends are connected until light has had time to get there & back. Relativity is absolute.)

Take a look at the video made by YouTuber AlphaPhoenix where he constructs the entire thing on a smaller scale and demonstrates the effect with an oscilloscope: https://www.youtube.com/watch?v=2Vrhk5OjBP8

One way of viewing what’s going on here is to consider the two sides as a pair of large dipole antennas. When the switch (or in AlphaPheonix’s case, a transistor) is turned on, a pulse of electrons is pushed down one antenna, setting up a transient wave in the electromagnetic field around it which induces a current in the opposite direction in the “receiving” antenna on the other side. This happens regardless of whether the wired are connected in a loop or not!

Physics is great.

None
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marcan_42
I found the AlphaPhoenix video a bit disappointing because he didn't clearly explain that the capacitive interaction between both ends is also light speed limited, and very dependent on distance, i.e. the geometry of the test. Had the test been done in a big round loop, current wouldn't start flowing at the far end immediately. Otherwise you'd have made faster than light communications.

I'm also not even sure if his testing methodology is solid; he was getting a ton of common mode junk in the target measurement probes, and subtracting it out in the scope. That works in steady state, but when trying to measure fast transients like this it depends on things like probe skew and more. It's just not clean enough for me to be able to trust the results are caused by the explanation he gave. Measuring subtle phenomena like this with long transmission lines involved with a single ground referenced scope and no true differential probes... ick.

elisbce
He has an upcoming part2 of the video which he listed big round loop as one of the follow-up experiments. We should just wait for that.
pja
>Had the test been done in a big round loop, current wouldn't start flowing at the far end immediately. Otherwise you'd have made faster than light communications.

Yes, this is obviously the case. But it's also not the setup that was being tested.

(Apparently he's editing a part2 which contains many weird & wonderful topological arrangements.)

Honestly though, I'm not sure what your problem is here. His results match very closely what you'd expect theoretically given the experimental setup. Not only that, if you model the setup in software using a suitable electromagnetic modelling code (there are videos on YouTube of people doing this) you get exactly the same result. Common mode noise on both sides is an irrelevance - you can just subtract it away without loss of generality.

marcan_42
You can only subtract common mode noise out if it really is common mode and perfectly equal on both sides of the system. With two discrete probes, that's going to give you a lot worse common mode rejection than with a proper differential probe. He can't even have proper ground references the way he did it (most of his probe ground clips are unconnected). It's just not a good rig. Sure, it might work, and his result might be good, I just don't feel confident about it given the experimental set-up.

If you look at his scope plot, the common mode voltage is kind of a mess and much larger than the actual differential voltage. That doesn't give me a lot of confidence in the final result. I'd like to see a more controlled version of this experiment with better equipment.

Source: I've done the same thing he did, using two probes to measure a differential voltage, and I can tell you it kind of works, but not well. Especially not at higher frequencies.

formerly_proven
The common mode problem can be avoided by making the experiment not differential (which coincidentally saves half the wiring) but even if you do that, you still get a large influence on the result due to the coupling between the twin-lead line and ground. It's actually a pretty good demonstration why using baluns for twin-lead is necessary; only the differential mode of the line works well, because it's not actually a two-conductor line, as it's an open line it is also coupled to ground. In my experiment (with ~6 cm wire spacing, which makes relatively little difference as the impedance of the line is proportional to the log of the spacing) I found that suspending it around a meter above ground gave almost identical differential and common mode impedances. That of course rather significantly reduces the amplitude you're going to see in the experiment.
This guy performed the same experiment using a km long wire and measured the voltage in oscilloscope.

https://www.youtube.com/watch?v=2Vrhk5OjBP8

raverbashing
Yes, and guess what? The bulk of the electricity takes the roundtrip time to start to flow

"Oh but what about that tiny bit!" That's capacitance. Sending "electricity" through air is not new, it's called Radio.

Dec 17, 2021 · 434 points, 229 comments · submitted by indosauros
y04nn
The first signal is a close RF transmission, billions of people rely on it everyday, a current disturbs the electromagnetic field and and an antenna, sometimes thousands of kilometers away, detects a very small variation in the field (-120dbm @ 50Ω = 0.2μV). This is how our cellphones, wifi, GPS, RFID works. So, even if you disconnect the bulb and the switch you can create a current in the bulb by turning on and off the switch.
dehrmann
Ignoring how accurate calling it RF is, so the experiment showed that electrons travel faster through air than through copper, you can see that, and the two delays are what you'd expect them to be?
y04nn
The transmission speed in air would be very close to a vacuum, so the speed of light (c). This depends on the velocity factor [1], for pure copper it's 0.95 c, so 95% the speed of light.

Actually for air, according to this source [2], the velocity factor is 0.999707085823853610892 c.

[1] https://lowpowerlab.com/guide/rf-best-practices/velocity-fac...

[2] https://www.qsl.net/ac5jw/isbp/vf.html

userbinator
I think the important point to note about that is it doesn't necessarily have to be a purpose-built "radio transmitter" to emit RF energy; everything which involves moving charges will radiate an EM field. This becomes especially apparent when you read the century-old books on early experiments with radio, and see the extremely crude circuitry they used to generate those waves.
y04nn
Absolutely, if you turn on and off a light switch while listening an AM radio (even static) you would hear it through your speaker, as in this demonstration [1] (it worth watching the whole video if you are interested).

[1] https://youtu.be/LMxate9gegg?t=104

01100011
I feel like RF is the wrong term. RF is short for radio frequency. That implies an oscillating EM field at a frequency which is practically useful for radio transmissions. This is a transient EM field disturbance. Same mechanism more or less, but it's not really 'radio'. I'm sure many will disagree but that's my opinion on it.
y04nn
Yes I agree with you, RF is not the good term in this case. I wanted to compare it to RF transmissions which are oscillations in the EM field.
soheil
This Veritasium video was the first instance of clickbate 2.0

We're going to see more and more this type of video. Instead of the thumbnail and title of the video being extremely controversial to attract views, the thesis of the video will be controversial to create endless online debate.

spookthesunset
Trolling 2.0?
TempestSA
Why wouldn't a simpler explanation be that the wires produce a radio/electromagnetic wave and that wave gets picked up and induces a current, which is how radio transmitters receivers work?
8bitsrule
What's going on -in time- is a lot more complex than the 'steady-state, Occam's razor' simplicity most of us (outside of EE) were fed. One example: the math you'll see in the analysis of 'skin effect'.

https://en.wikipedia.org/wiki/Skin_effect

I hope one of the outcomes of this discussion is that someone will tackle explaining how AC power gets from source to load, and what 'earth grounds' have to do with that ... and WHY. The usual hand-wavy 'simple' discussions leave out WAY too much.

XorNot
Except the skin effect itself is tiny at scales upto household electrical wiring - you can completely disregard it in analysis.
Jansen312
Most people didn't have EE education at college level. Transmission line or radio wave carrying energy is a concept usually taught much later in ones schooling. Derek basically want to target mass market that receive basic electrical knowledge that actively tells you electric "only" flows in cable. A lot of people replying to his video subsequently demonstrate that Derek is right that these group of people have the not exactly right idea taught at school. Some people replying wishing to show he is wrong completely missed his message.
dylan604
>people have the not exactly right idea taught at school

could it not also be that some of these students didn't actually learn what was being taught, and just squeaked by with minimum grades to not have to take it again?

x0x0
fwiw, I definitely was given the wires and electrons are like a pipe for water somewhere during schooling, and it was interesting to hear a deeper explanation.
dylan604
and during this discussion of electrons flowing, did it now also contain discussion on the fields produced around the wire? did I just have an exceptional teacher (I know my high school physics teacher was one of those teachers and am indebted to him), or did I just pay attention?

To the point, during the time that I was learning fields produced around a wire carrying a current, I was also learning recording studio audio and how hums can be created by running cables in parallel and avoided by crossing them perpendicularly. I had a conversation about it with said physics teacher, and he gave a lecture about it the next day. Yeah, one of those teachers that sets one on a positive course.

x0x0
fields: it was mentioned there were fields :). Nothing as to why one would care; just that fields existed.

Your teacher sounds awesome.

kzrdude
He's just leaving them with a different misconception, now he's told them to ignore the wires completely. I don't think this video helped anyone (for the various reasons stated in this whole topic).
jayd16
It's not a trick question if you explain the trick up front.
zokier
The thing that is most curious in this tempest in a teacup is why didn't Veritasium film this experiment themselves. It isn't particularly complicated or expensive setup, so it seems something that he definitely could have done. Instead he chose to leave the door open for the controversy that followed.
formerly_proven
They didn't film it but

a) it's pretty trivial to do (I did it myself when the video was new because dangit a physicist kept sayin' I was wrong on the internet and that's UNACCEPTABLE)

b) there's a PDF in the description where one of the EE profs he asked did and gets exactly the same results as everyone else and also shows how easy it is to predict behavior of the experiment using line theory.

blamazon
I wouldn’t have even heard about the Veritasium film if not for this response. Smart marketing play.
ehsankia
I was surprised by that too, though it seems like he is actually working on such a video now. Honestly I have a feeling that this kind of science debate style content is becoming more popular. There was the Veritasium vs physic teacher about the faster-than-wind car, and also the Steve Mould vs ElectroBOOM about Mould Effect recently. Maybe he intentionally left it vague to get people to debate with him.
amelius
This is basic transmission line theory.

https://en.wikipedia.org/wiki/Transmission_line

userbinator
I've been partially following the discussions around the original Veritasium video and all that it's caused, and my thought was basically the same: the masses are just rediscovering what was known over a century and a half ago and that theory has found countless applications in communications and power distribution for roughly as long. IMHO that's not a bad thing, but to present it as something novel is.
jjoonathan
In particular, the characteristic impedance of ladder line (air dielectric) is:

Z ≈ 276Ω * log10(2 * separation / diameter)

https://en.wikipedia.org/wiki/Twin-lead#Ladder_line

tgsovlerkhgsel
It may be basic, but just the _existence_ of this field wasn't something that was on my radar, let alone all the details and implications. This was certainly the most interesting and enlightening set of videos I've seen this year.

I particularly like this one because "I want to get an oscilloscope and see what is actually going on" was my first thought, and this video saves me the effort of trying to set up what would be a much more limited version of the experiment. The promised followups also cover exactly what I'd like to see tried next.

naasking
You should watch Electroboom's analysis if you want the full details from an electrical engineer:

https://youtu.be/iph500cPK28

vmilner
The history of transatlantic cable-laying is extraordinary (and didn't work for several attempts because the theory of the field around the cable wasn't properly understood).
toomuchtodo
Great book on the topic:

https://openlibrary.org/works/OL3347773W/A_Thread_Across_the...

https://smile.amazon.com/Thread-Across-Ocean-Heroic-Transatl...

lmilcin
Fun to introduce general population to some interesting physics but please, don't call it "settling physics debate".

There is NO debate. Not physics debate, not even practical debate because that knowledge is in practical everyday use.

We know signals in wires take time to propagate and I have to take this into account when I design my circuits. Things like matching lengths of traces (especially differential pairs) so that critical signals take same time to propagate or matching length of trace and return to improve signal integrity are staple for anybody that is working on anything over couple hundred megahertz.

All of this only because it takes time for signal to actually travel through the length of the wire.

foxfluff
"I have never in my life length matched the two lines of a differential pair, including at 10 GHz. Never." - Rick Hartley

https://youtu.be/QG0Apol-oj0?t=2765

jeffbee
I mean ... he's saying right there on the slide there's less than 1mm of length error budget at 10GHz.
foxfluff
And that's gobs. What's your typical space between the lines in a pair? Five mils? You run them side by side and you'd be hard pressed to make a length error significant enough to matter. Yeah you do need to be aware of it enough to ask whether you're good when you're routing a really weird loop.. but for the vast majority of things and sane routing, you can just eyeball it or don't need to care at all.

Point is, a lot of people seem to think length matching is critical ("for anybody that is working on anything over couple hundred megahertz") and application notes would have you believe as much but the industry experts and theory I've found suggest it's way overstated.

jeffbee
I've always followed Howard Johnson's rule of thumb to match them within 1/10 of the rise time, but it's not like it's a lot of work: the software does it automatically.
lmilcin
It is right if you are only interested in making the damn thing work.

But if you don't want it to broadcast noise like crazy you want it tight and matched as much as possible.

The value of differential pair comes from the fact that they have constant common component. That only works if both components aren't shifted in time. If that happens, you will get strong common signal and say bye to nice quiet differential pair.

foxfluff
Are you saying your differential line is causing EMI if it's not length matched?

Or are you saying that the receiver won't do a good enough job cancelling common mode noise if you're not length matched? For that, I'd like to have a reference. Otherwise I'm not convinced this is more critical than the max skew to keep your crossings in the right region.

lmilcin
Differential pair minimises EMI by having constant common mode potential over the length of the line (and wires close to each other). Meaning if you look at the pair from afar the average of their voltage at any point in the line is constant. Or you might say that the noise from both lines cancels each other. From afar, it looks like there is no signal traveling the length of the line (to an approximation, because there is necessarily some distance between the wires meaning the cancelling is not perfect).

If the signals are shifted in time, though, that is no longer true. From afar you will see places in the line that have different common mode potential. Where one signal edge lags behind the other the average will no longer be the same as for the rest of the line. From afar this looks like high bandwidth signal travelling down the line.

soneil
That's fairly intuitive. The lower current being present before the signal arrives is not intuitive.
sega_sai
I just arrives through the air. The electromagnetic wave will propagate with similar speeds through the air and wire.
soneil
I didn't finish the video (yet, no fault of the video, just bad timing), but I don't think it's EMI - the "pre-current" looked fairly flat, and EM doesn't like flat. I'd expect EMI to show as a spike timed to match the leading edge of the signal.
foxfluff
I think the takeaway is that EMI looks flat for a while if you run half a kilometer of wire next to a half-a-kilometer long source of EMI.

The leading edge isn't there for one nanosecond and then gone, it travels down and continues to induce a current to the adjacent conductor, a current which must continues to flow.

lmilcin
Want something non intuitive? The energy does not travel through the wire but outside of it.
charcircuit
>There is NO debate

I'm guessing you never checked the comment section.

lmilcin
Bring any topic however widely known and thoroughly proven to a large enough general audience and you will always find people with no actual knowledge that will question it.

Try to find a post on HN with a lot of upvotes and comments where everybody would agree on something.

If you want to know if there is "physics debate" ask people who know physics, not commenters on Youtube or HN.

charcircuit
Why are random commenters not allowed to have a debate regarding physics?
BenjiWiebe
They are allowed to.

However, saying the phrase "a <n> debate" -usually- leads people to believe there exists a debate about <n> in the field of <n> between experts who study <n>.

bellyfullofbac
Curious how in the last day or 2 HN front page has 2 links to "hey kids, watch me!" YouTube videos...
AlabasterAxe
It's less "settling a debate" and more "clearing up major misconceptions than most people will come away with from watching Veritasiums video". I've taken several physics and electronics courses in my life and after watching Veritasiums video, I was under the impression that the majority of the current would be flowing through the lightbulb immediately which is not the case. So this video is just demonstrating that there's an initial "residual" current induced in the lightbulb from the electric field but the majority of the current is propagating at the speed of light through the wire.
0xTJ
That Veritasium video is one of the most controversial educational videos I've seen. I think one of the issues with it is that it's a bit pedantic, but also ignores other issues, that invites other people to be pedantic about it.
Laremere
As much as I love Veritasium, I feel the OP video is better than his. Actually doing the experiment is really good, and it honestly feels like he was fishing for another debate like the faster than wind car by giving only a super theoretical and unintuitive explanation. (I don't have any real evidence of that, but it does /feel/ like it.)

I also wonder what would happen if, instead of a setup like this:

  ┏───────light────────┓
  ┕──────battery───────┛
You did something like this:

  ┏──────────────light─┓
  ┃                    ┃
  ┃                    ┃
  ┃                    ┃
  ┃                    ┃
  ┃                    ┃
  ┃                    ┃
  ┃                    ┃
  ┃                    ┃
  ┃                    ┃
  ┕─battery────────────┛ 
  
That is, battery (and switch) and light at opposite corners of a large square, instead of on the middle of a long double-line. Veritasium video implies the current will start flowing at sqrt(2) * width, instead of at 2 * width. Would these effects really work over longer distances like this?
NikolaeVarius
Yeah, this is what im wondering. The proposed mechanism for this is that the wires generate electric fields that influence electrons remotely. Fine.

What happens when they are not close enough for any meaningful electric field interaction?

BHSPitMonkey
He says near the end of the video that a Part 2 video is forthcoming with more exploration of:

- Different sized loops

- Wires closer together / farther apart

- Wires on the ground instead of in air

- Current on both sides of switch

- Wires in two big spread-out loops

- Different strength resistors

jjoonathan
The "fast plateau" is pitiful from a power delivery perspective even under tight coupling. Under looser coupling, it becomes proportionately more pitiful.
rrobukef
When they are not close your circuit will have a large area and a large inductance. Which means that the noise will grow as the capacitance-effect decreases until its effect is unrecognizable.
robscallsign
If they're not connected, then they're just two antennas. What happens when you get far away from your wifi hotspot or a cellphone tower?

The voltage/energy transmitted becomes vanishingly small, and smaller than the thermal noise of the electrons in the other antenna, and undetectable. https://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise

jonas21
Presumably yes, but it would be very hard to measure since the field falls off with r^2.
ghotli
Hey, did you make that ascii art by hand or did you use a tool I don't know about? If it's a tool I'd like to use it :)
Laremere
Just copy pasting from https://en.wikipedia.org/wiki/Box-drawing_character
ghotli
Nice thank you. TIL
UncleOxidant
I think the issue with the square would be that the capacitance would be much, much smaller since the wires are separated by a large distance (square law). The capacitance of the original setup is already quite small, but at least it's noticeable on a decent scope. But I doubt you'd see that effect in the square setup.

The other issue with the Veritasium "setup" was that he specified that the wires had no resistance. That being the case the RC time constant would be 0 and thus you wouldn't see that initial charging of the capacitance (and associated current flow) because it would happen instantaneously under those assumptions.

Jansen312
As a parent, Veritasium would be way more preferred teacher to inspire students to search for answer. There are many stellar students who scored A* that later in life just dump what they learnt. You'll be surprised how many medical students didn't make it to MD or not a MD anymore a decade later. Having someone that spurs you to work for it is a weight in gold itself than a great tutor helping you score full understanding and get that A*.
systemvoltage
You also need to account for the fact that oscilloscope wires would also be longer going to the light bulb. You can imagine this on the extreme case where light and battery are 1 km apart. Now, you need oscilloscope wires to go 1km far to connect to the light bulb and your timing is off.
charcircuit
The current will always start following after the distance between the switch and bulb divided by the speed of light amount of seconds.
teddyh
Once the light and battery are far apart, I have a horrible suspicion that the definition of simultaneity will become problematic.
JonathonW
The further the battery and switch get away from the light, the less current you'll see at the battery at (sqrt(2)*width)/c s, since the electric and magnetic fields around the battery and wire will drop in strength as you move further away from them.

Put another way, the main reason this effect is observable in the way shown in the video is because the light and battery, and the wires between them, are so close together. Move them further away, and, per the inverse square law, you'll start seeing a much lower induced current-- the effect may still be there, but it won't be measurable over the noise floor of the experiment setup.

junon
This makes more sense and was my first thought watching the video.

Question: At which point does the influence reach actual zero? If it doesn't, does that mean the coffee in front of me is being influenced by Jupiter, however minuscule?

smsm42
In field theory, IIRC, fields (absent special setups, i.e. in space) are never actual zero, but due to reverse square law they become too small to actually care about quite soon. But the quantum model may have some limitations on that, since stuff can't be arbitrarily small there AFAIK. Not sure what happens about the gravity - likely, Jupiter might influence your coffee, even though in an immeasurably small way, since gravity is very weak. We know the Moon influences our oceans quite prominently. But maybe there are minimums there too?
bsder
You're right, but sorta. Which is the big problem here, any simplified analogies break down.

What's happening is that you are straying further and further from the "impedance matched" condition (the inductance per unit length stays the same but the capacitance goes up with the separation--however, being "too close" will also cause similar behavior). Consequently, the energy transmitted per reflection gets smaller and smaller.

Part of the problem in this whole discussion is using a "light" as a "threshold detector" where the threshold is effectively microamps. A microamp threshold detector is not what people think of as a "lamp".

If the original Veritasium video had showed the current flow via meter, oscilloscope, etc. nobody would be terribly surprised as it would show small flows getting bigger upon each reflection until it built up to the full current.

JshWright
> I think one of the issues with it is that it's a bit pedantic, but also ignores other issues, that invites other people to be pedantic about it.

I think the video is intentionally misleading. He got a taste of how "successful" a controversial video can be with the "Wind powered car going faster than the wind" thing, and he's leaning into that. I just don't see any other explanation for how he chose to frame the problem.

jarenmf
That's unfortunate because his content used to be very good and this video seems only seeking engagement at a very shallow level, e.g. doesn't even mention transmission lines.
a9h74j
My early thought was that, at the very least, Poynting Vectors deserve a video but Transmission Lines also deserve a video.

Here's a problem I recall from Jackson which might (or might not) provide a missing link:

Given two parallel conductors of arbitrary shape, prove that the product of capacitance-per-unit-length and inductance-per-unit-length is a constant (i.e., independent of profile and separation).

I remember finding a suitable answer, but I can't for the life of me remember how.

Jansen312
Watch his vid again. Transmission line mentioned. He even use the issue with putting cable across the ocean having issue as a possible example explain his thought experiment. Could it be you used to watch his vids in full and remember and not so much for this one?
Aengeuad
The term 'transmission line theory' (or even 'transmission' for that matter) doesn't appear to have been mentioned in the video at all[0], and this is a complaint that was also raised by Dave Jones[1] in his critique of sorts. The video is fundamentally about transmission line problems and the term is mentioned both in the description and the word document containing further analysis, but its omission does lend some credibility to the complaints in the parent comments that the video style is intentionally pedantic (it is a pure physics vs practical electrical engineering take after all) and presented as a controversy which comes off as a bit shallow as a result.

If one were to put on a tinfoil hat it doesn't seem like much of a stretch to imagine that the plan was to have a follow up video to settle the controversy with the gist of the video being about transmission line theory and concluding with a practical demonstration of the effect.

[0] I don't have the time to carefully watch a 15 minute video to verify this, and demonstrating a lack of evidence seems difficult, but the subtitles for the video can easily be downloaded with youtube-dl and then grepped or opened with a regular text editor. Note that these subtitles are manually written and not auto-generated by youtube, and while it's possible there's some differences in the script and what is said it seems unlikely.

youtube-dl --write-sub --sub-lang en --skip-download https://www.youtube.com/watch?v=bHIhgxav9LY

grep -i 'transmission' 'The Big Misconception About Electricity-bHIhgxav9LY.en.vtt'

[1] https://youtu.be/VQsoG45Y_00?t=1013 (16:53)

pclmulqdq
I completely agree. When I got an EE degree, most of the content was about how electric fields work. It's not a simple concept. That video was reductive to the point that it made me angry. For all practical purposes, he is wrong, and he should admit that.
fouc
Not everyone has an EE degree.. As far as I can tell, the majority of the video seemed like a honest way of explaining the electric field / "flow of electricity" phenomenon to the layperson.
paxys
That video perfectly summarizes online discourse. I personally found it fantastic as a resource. It was the best and most clear explanation of transmission of energy in an electrical circuit that I have seen. It debunked a lot of myths in my head that we were all taught in school.

The thought experiment he proposed was just a hook to keep people interested - and it certainly did the job. Because it is a popular internet video by a popular YouTuber, however, the entire scientific community made it a mission to nitpick every detail of that experiment and show that the conclusion wasn't 100% accurate without a bunch of caveats. Which is fine, I guess, but also missing the point of the whole thing.

spookthesunset
I actually think he intentionally worked with (some of) these other youtubers. I've been enjoying watching all the "regulars" I follow on youtube challenge his assertions.
stormbrew
I'm sorry but no, the original video does clarify some important things that people misunderstand about transmission of electricity, but then it piles on a bunch of other really unclear information with no explanation. It answers a question with about 8 other questions and then offers no help in understanding any of them.

You can't just say "there's electricity at the light bulb nearly immediately! (oh by the way it's not very much electricity but I'm not going to explain why or even how much less, and it's probably not even enough to turn on an LED but I'm not even going to mention that)" and then get pissy when people are like "???!??!?!" It's pretty blatantly deliberately misleading and confusing in order to stir up exactly this controversy.

Especially since the effects he's describing are probably (as mentioned in this video) because of capacitance, and are completely dependent on the 1m distance between the wires across the entire span, a constraint he mentions basically once and then never again, and never says explicitly that it's related to the effect.

This video and electroboom's videos are far more educational, and more importantly don't leave you hanging with a bunch of new questions with no resources provided to answer them.

jacobolus
> because of capacitance

Or we could say they are “because of Maxwell’s equations”, a particular common effect of which we model using the simplified shorthand concept of 'capacitance'.

function_seven
> Especially since the effects he's describing are probably (as mentioned in this video) because of capacitance, and are completely dependent on the 1m distance between the wires across the entire span, a constraint he mentions basically once and then never again, and never says explicitly that it's related to the effect.

YES. This is my biggest gripe with the video. A better shape of wires would be a pair of tangent circles, each one with a circumference of 1 light-second, and a 1-meter section removed at the tangent point. (Hope I'm describing it right. Basically but only the switch and the light bulb 1 meter apart, but get the wires as far apart from each other as possible)

Now would that eliminate capacitance? Or largely so? What amount of current would begin flowing across the bulb at t₀?

After seeing that video and all the reactions, I know more—but not from the original video. My mental model of electricity is still that it "flows along wires", but I now can somewhat separate the movement of charged particles from the energy flux those moving charges propagate. I think.

randyrand
It’s not pedantic.

EMI “teleporting” outside of wires is a real world issue that engineers deal with constantly. FCC certification is almost entirely about this phenomenon.

It’s just told in a confusing controversial way.

formerly_proven
I'm not an avid Veritasium viewer but from what I've seen this MO seems to be kinda his shtick.
Jansen312
Veritasium is the better teacher. The rest is just jumping on the bandwagon to grab viewerships. Think about it, back in your school days, you have an inspirational teacher that challenge or motivate you to pursue something. Rarely that teacher will spoonfed you with all information. I have many great teachers that explain well. But not a single one of them make it to the list of inspirational. I have 1-2 memorable teacher that really inspire me and they don't exactly explain things exceptionally clearly and all-in-one package. Veritasium is the kind of person that moves needles. Electroboom will be the inspired students to follow-up. The fact that he demo that wind car thing correctly and better than the specialist shows that he is the better teacher.
blondin
sorry, veritasium is not / no longer the channel you think it is.

they are not out to teach first.

teaching became second at some point. making views became first and more important. it is totally understandable. (they talk about the team, paying people, etc.) i personally appreciate the honesty. the video they did around the subject should still be around.

kzrdude
They really managed to get a success this time: lots of views for this controversial video! But for me, it feels like a lot of credibility capital was spent. I was probably part of the core audience a few years ago.
runarberg
For me Veritasium lost all his credibility capital by the way he responded to Tom Nicholas’ video about YouTube sponsorships using Veritasium as a case study[1]. In stead of approaching the debate calmly (or better yet, simply ignoring it) he came to the comment section way too defensive, like a lot, basically calling Tom a lair and a bad actor.

Actually that is not quite true, Veritasium lost a bunch of his credibility capital when he made the sponsored content for the self driving cars. I never watched that video as I spotted it was basically and ad and was reluctant to watch his new stuff after that (though I did).

1: https://www.youtube.com/watch?v=CM0aohBfUTc

Ostrogodsky
This is the youtube generation. Entertainment, clicks and wow factor first (and money of course), facts a distant second.
vexxed-concave
True. It’s one of only a handful of YT videos I’ve ever left a comment on. In summary, just because something is “wrong” at one scale doesn’t invalidate useful models and workaday theorems at another.

Also, for such a pedantic video his field lines were wrong.

JshWright
> It’s one of only a handful of YT videos I’ve ever left a comment on.

Which was exactly his point— It's called "engagement".

GenerocUsername
Yeah, the assumption that Derek is 3 steps ahead might be wrong and he might just be wrong.

Well played though that the world thinks he knew his wrongness would spur debate.

Speaks to his earned credibility, but not to his infallibility.

01100011
A long, long time ago, before I realized software makes more money than being an EE(albeit with less life satisfaction), I went to school for EE. I like the Veritasium video for the debate it is spurring, but I really hate his impractical assumptions(funny, since 80% of EE is 1st and 2nd order approximations with 10% tolerances, but I digress). I get that he needs to simply things dramatically because of the audience he's trying to reach, but light year long superconducting wires and a light bulb that turns on with infinitesimal current just bother me. I guess normies wouldn't get that interested by talking about transient EM waves... but the video just leaves a bad taste in my mouth and I understand why EEs are making response videos. I wish he at least mentioned that the power reaching the light bulb would be practically useless. Oh well. Hopefully it spurs a few young minds into sacrificing higher pay for a career in EE or physics.
leafmeal
Here's the link if you're as curious as me https://www.youtube.com/watch?v=bHIhgxav9LY
jacobolus
Controversial is fine to the extent the controversy shows people struggling toward clearer understanding and better explanations, and as long as all parties are operating in good faith (i.e. not being deliberately misleading).

Let me highly recommend Mehdi Sadaghdar’s (ElectroBOOM) excellent response video https://www.youtube.com/watch?v=iph500cPK28 which does a great job of empirically investigating and theoretically explaining the subtleties involved, in a polite, respectful, and entertaining way.

I have similarly enjoyed the exchange between Sadaghdar and Steve Mould about the physics of the “chain fountain”.

These kinds of friendly scientific “debates” show viewers (e.g. kids) a bit of how the scientific process and scientific discourse works, in a form that is more accessible and digestible than technical journal papers or history books.

Having a discussion back and forth helps to improve both viewers’ specific knowledge and viewers’ processes for comprehending and interrogating new information, so long as the median viewer actually sees some of the responses. (Someone who only ever saw the first Veritasium video probably ends up with a somewhat wrong mental model.)

QuantumG
Teaching. What a concept.

It warms my heart to see a generation of scientists, engineers and communicators attacking frontiers again.

For a while there it felt like just a few of my friends were fighting for the future and everyone else had written it off to Sci-Fi.

kongolongo
ElectroBOOM's exchange with a retired MIT professor (it was over whether or not KVL always holds) was also very polite, respectful, and entertaining and yet surprisingly the professor who must have received and exchanged feedback before having published many, many times seemed to have a meltdown over a the disagreement.
canjobear
Successful professors can get to the point where they’re no longer interacting much with people who disagree with them.
everybodyknows
Anyone care to give us a Too Long; Didn't View?
wdfx
When you close a switch to initiate an electrical current down some long wires it takes a measurable time before you know what's at the far end of the wire.

Therefore if the wire is either intact or broken at the far end, over a 500m distance the first 1.6us of measurement looks exactly the same.

soheil
Technically there is a very small current that flows through the circuit almost right away due to capacitance and inductance properties of the circuit, so Derek was right technically. That current won't be enough to turn on the light bulb. The rest of the current that actually turns on the light bulb takes some time to reach the bulb because the wire is so long and electrons travel with the speed of light along the wire [0].

[0] actually electrons don't move that much, instead electrons pushing against each other on the wire cause a ripple, it is this wave that moves along the wire and turns on the bulb.

umvi
200uA of current flows through the lightbulb instantly, but it doesn't reach full current until speed of light delay.
nathan_f77
I don't think this is possible. If it were true, then you could add a transistor and an LED on the other side of the 1000M wire, and light up the LED instantly as soon as you press the switch. (Transistors and LEDs only take a few nanoseconds to turn on.) It's not possible to send any kind of signal or information faster than the speed of light.
kreetx
In the video he explains that the "faster than light" effect happens due to the magnetic field traveling through air (because the light bulb is so near by). At least that's how I understood it; and hence my question about changing the position.
function_seven
Parent's use of "instantly" is a bit imprecise. Here "instantly" means after 1 ns, whereas "speed of light delay" means the delay over the full 500m distance out and back.
tsimionescu
The point here is that the LED is 1m away from the source. The signal still reaches it after a light-speed delay, but it doesn't travel along the wires, it travels through the air.
jstimpfle
Watch the video, read the other comments. The "instant" current flow comes from crosstalk. While the resistor and the battery are separate by 500m worth of ire on each side, they are actually located next to each other (so both places can be measured simultaneously).
kreetx
A follow-up question: would there be no tiny change in the graph if the wires exiting the battery were further away from the wires immediately entering the light bulb?
rrobukef
The capacitive effects will decrease and noise created by inductive effects will increase due to a larger area.
bee_rider
Yeah -- nothing mysterious is happening, the electrons coming out of the battery are just causing an electric field, which causes current in the wire near the 'lightbulb.' This electric field obeys the c speed limit, so if the battery terminals were far away from the 'lightbulb,' there'd be a fundamental physics limitation, the current couldn't start until at least d/c (where d is the distance).

More likely the electric field would be too weak to measure, but that's not fundamental -- you would just have trouble finding a sensitive enough 'lightbulb.'

jbjbjbjb
Watch the animation starting at 17mins. The electrons at the light bulb end start moving immediately because of the magnetic field and the electrons at the far ends don’t move. Would have been cool to have oscilloscopes at the far ends and somehow sync them all up to show nothing happens at the far ends.
parhamn
My notes: https://synth.app/s/JeJYQgwxey8
kleer001
roughly : electric power (and resulting work) is transmitted at the speed of light in the form of magnetic waves, not by the movement of the electrons in the wire the current goes through
tsimionescu
Some small part of it is. The vast majority is transmitted along the wires.
ufo
I think the most interesting part is from 16:45 to 18:00
rusbus
Here's a summary, but really you should watch the video, it is great.

Take 1km of wire, a resistor lightbulb, and a power source. Connect oscilliscope around power source. Flip switch.

For 1 light-speed delay, you actually see current going across the lightbulb! After the speed of light delay, current starts flowing normally as expected. (Why? How? Is this spooky action at a distance?)

You're actually seeing cross-talk between the wires where the build-up of electrons on the high side actually moves electrons on the (spatially) adjacent side of the loop!

Then to really complete the puzzle, sever the end of the wire. You still see the exact same behavior up to the speed-of-light time! (Which, how could you not! You need to wait a speed-of-light delay to _discover_ that the wire was severed, so you MUST see the exact same behavior.)

yholio
TLDR: Veritasium is wrong and misleading, current actually flows in wires and is the main way energy is transported from source to the consumer, energy does not generally flow in the space "between" the wires.

Yes, very long wires behave like capacitors/antennas and transmit a certain amount of transient power instantly by coupling, but most useful energy is transferred after the speed of light delay, when steady state is achieved.

Nonetheless, by carefully selecting the AC frequency and the physical configuration of the lines, you can create a situation where most energy is transferred nearly instantly by the electromagnetic field and the far ends of the line are more or less irrelevant. So you obtain the Veritasium effect, but it's a very particular arrangement, not the general case.

csense
I'm a big fan of AlphaPhoenix's content. He deserves to be in the big leagues of science YouTubers with SmarterEveryDay, Veritasium, Mark Rober and 3B1B.
sen
Yeah he’s great, I recently binged his videos and he’s criminally underrated. He’s a really smart dude who’s great at explaining things without dumbing it down too much, and also very entertaining. Plus his excitement and enthusiasm is infectious, he really loves what he’s doing.
enchiridion
Don’t forget Applied Science!
instakill
or The Science Asylum
code_biologist
To add some others:

Physics Explained is great physics channel that doesn't shy away from math, with derivations of many fundamental equations. His most recent one deriving the Chandrasekhar limit on white dwarf stars from relatively basic physics is great!

The Efficient Engineer is a really good one for clear concise explanations of mechanical engineering principles.

slig
Stuff Made Here is awesome too.
colechristensen
I’m not a fan of the “big leagues” of science YouTube, many seem to have been tainted by the attention algorithm game.
Pulcinella
Agreed. I’m especially disappointed with Veritasium because Derek’s originally PhD thesis was how these sort of “controversial,” clickbait-y popular science videos are actually really terrible at teaching anything.
frosted-flakes
Especially Mark Rober. His videos aren't really about science at all, but rather attention-grabbing feats like package thief glitter bombs, squirrel mazes, and chemical volcano explosions—pure entertainment. None of his videos teach you anything like Steve Mould's videos do.
motoxpro
I think the point is to get people excited about science and show what is possible/spark curiosity rather than trying to recreate a classroom. You can see this by all the kids that take his classes. There is space for both to exist.
6nf
Excited about engineering, not really science.
userbinator
I wonder how many of those kids are going to reconsider once they find out that doing "real science" is, in reality, far more boring.
spookthesunset
Same could be said about almost all of the "technology" field most of us work in. I mean think of how many people dream of being a game developer... what a shock that must be.
an1sotropy
Yes, and he might even agree, since he now uses his youtube videos to advertise his $249 creative engineering course on monthly.com.
rectang
Rober is surely an entertainer first, but he claims to be an engineer rather than a scientist. The videos are more about building things which solve specific problems rather than revealing scientific truth.

Off the top of my head, I remember how the pin failed in the automatic placekicker video, how the cameras worked in the moving dartboard, how they had to use different materials to contain the large scale elephant foam...

formerly_proven
It's not really a debate - anyone with basic EE knowledge knows what this experiment does and what few parameters you need to predict the exact behavior.

Of course if you take it literally - superconducting wires, car battery, 12 V light bulb - then it's very likely that the suggested answer is not even technically correct, because the initial pulse amplitude as seen by the lamp is simply too low to light the bulb up. If you take it less literally and match the "light bulb" impedance more or less to the transmission line impedance (~1 kΩ or so in the experiment with the suggested wire spacing and assuming "reasonably thing" wires), then you're getting much closer to the answer he is suggesting.

kazinator
We can make an analogy to trains. Suppose instead of a circuit, we have a long train on a circular track, completely occupying that track. To "turn on" the circuit, we begin to move one of the cars. Now there is slack in their coupling, so a ripple effect occurs: the cars do not all move a the same time, but a wave of motion begins, and this propagates in both directions around the circular track, away from the initially moved car. Eventually, both these ripples reach the opposite side of the circular track where the motion starts to occur and can be used to do some work. Then we can get into a more or less steady state: the cars are moving around the track.

This steady state of motion is like "drift current", whereas the initial ripple of couplings clattering together an initiating the motion is like the electric field propagating through the circuit.

Of course, EE's know about drift current, transmission line behavior and other topics.

tsimionescu
Your explanation would lead to the 0.5s answer - that's how long it takes for the first signal to ripple through the wires.

To get the 1m/c s answer, for your example you would have to add a seismograph to the opposite end of the train track - while the cart at that far end will only start moving once the ripple goes around the whole track, the seismograph will pick up the movement almost instantly, since the movement of the initial cart will send waves through the earth directly, not following the tracks.

MarkusWandel
Light is slow, not exactly 1 foot per nanosecond but it's a reasonable mnemonic. Think about that, if you had an optical cable running a reasonable (these days) 40 Gbits/second link and it's 3 feet long, that's 120 bits in transit from end to end at any given moment. And that's if it is optical and ignoring the slightly slower speed of lighit in glass; any sort of actual wire is slower.

For a transmission line i.e. one limited by distributed inductance and capacitance, the standard practice is to drive a powerful transient into one end, which then travels along the wire, switching any receivers along the way, and then absorb it in a termination resistor at the other end so it doesn't bounce back and glitch the receivers on the return trip. Again you have to consider an actual traveling wave; there's no such thing as "instant" on a wire of any length.

perlgeek
> Think about that, if you had an optical cable running a reasonable (these days) 40 Gbits/second link and it's 3 feet long, that's 120 bits in transit from end to end at any given moment. And

Since glass[1] has an refractive index of roughly 1.5, speed of light in a glass fiber is roughly 2/3 foot per nanosecond, so you actually have 180 bits in transit.

[1]: at least most kinds of glass used in optical fibers and windows, at the wavelenths typically used in optical communications, which tends to be roughly in the range of 800nm to 1500nm

m348e912
>>Light is slow

I am going to have to go ahead and disagree with you on that

layer8
Most stuff in the universe is moving apart faster than light, so yes it’s quite slow. ;)
userbinator
...and from the perspective of a modern computer and high-speed digital circuits, the speed of light doesn't seem that fast --- light moves only 30cm between each cycle of a 1GHz clock.
throw0101a
> Light is slow, not exactly 1 foot per nanosecond but it's a reasonable mnemonic.

"Admiral Grace Hopper Explains the Nanosecond" is a good illustration of this (segment is only 2m):

* https://www.youtube.com/watch?v=9eyFDBPk4Yw

* https://en.wikipedia.org/wiki/Grace_Hopper

Full lecture:

* https://www.youtube.com/watch?v=ZR0ujwlvbkQ

thehappypm
Ah, transmission lines. I studied these for far too long. It’s how I wound up in software!

Things like Ohm’s law are great tools for understanding circuits. However, the underlying forces that derive these equations are a bit lower level, and relate to charged particles creating electric fields. Every electron flowing is because there’s a net force on it, coming from an electric field caused by other electrons, protons, or magnetic interactions.

Electric fields are kind of hairy to use directly, and a much more easy-to-use concept is voltage. Voltage abstracts the field concept away, and tells you about how much energy will be expended moving charge around.

Turn a circuit on, what happens isn’t that the whole circuit works in lock step. First some charges near the power source will move, inducing new fields that propagate as a wave.

parhamn
I took some notes through the first part here: https://synth.app/s/JeJYQgwxey8 if you're on the go and can't watch.
renewiltord
What in bloody hell is this website? I have wanted this for so long and was going to make a shitty version of this as a weekend project. But this is fucking amazing. Thank you for this.

Bro, if this is your product, it seems fucking cool, dude. Told my buddy and I'm going to request an invitation too.

parhamn
Glad you like it! Email me directly at [email protected] so I make sure I don't miss it :)
griffinheart
I had a question about the veritasium video, at some point they say that the electrons barely move, that confused me since that doesn't match my understanding of amperage, flow of electrons being for example 6.24x10^18 per second.

Anyone care to help me out? Maybe that just isn't much?

Jabbles
Calculate the volume of wire that would contain 6e18 free electrons, assuming 1 electron per atom.

You can intuit it by knowing Avogadro's constant is 6e23.

So 1e-5 mol, 1 mol of (atomic) Copper is 63g, so that's 6e-4g of copper. Density of copper is 9g/cm3 so let's say 1e-4 cm3 = 1e-1 mm3 = 0.1 cubic mm of copper.

So one amp in a copper wire is equivalent to 0.1 cubic mm of that wire's electrons flowing out each second. I'd say that's "barely moving".

(very roughly)

griffinheart
Thank you, that puts it in perspective.

Just to validate then, these barely moving electrons will create a field that induces a current on the electrons on the other side of the wire that is 1m away, which would turn on the bulb, that if the lightbulb was an ideal current detector that ignores all other sources of electric fields?

pelorat
That's correct.
axegon_
Setting the obvious facts aside, I love the subtle cynicism behind buying a 1km cable to prove a point.
mikewarot
I just bought 2 light seconds of 0000 AWG bare copper for no good reason.

Fortunately Gallifrey Prime has easy returns. ;-)

nathan_f77
I don't think it's possible to detect a 200uA current across the resistor immediately after the switch is turned on. If I understand it correctly, then this would mean that information is being sent faster than the speed of light. Surely this small instant current must be caused by some kind of capacitance or interference.
AnotherGoodName
The resistor is next to the switch. So no information is being transmitted faster than light. It still obeys the direct line of sight speed, just not the wire speed.
wyager
Did you finish the video? He explained that it was capacitive coupling.
allemagne
The term "instantly" is being used in the video and in other comments to refer to the time it takes at the speed of light to travel the shortest distance between the switch and the "lightbulb"/resistor. The term "lightspeed" is used for traveling the length of the wire.

I think the idea is that this terminology is supposed to be an obvious simplification in context, but it seemed weird to me too because of how specific the Veritasium video was about when exactly the "lightbulb" would "turn on", and how the point of the thought experiment (and the point of this video that lightbulbs probably can't turn on in practice until the full current goes through the wire) is to show how simplifications can be misleading.

formerly_proven
You can explain this experiment just by utilizing basic transmission line theory (which is not a simplification per se: transmission line theory is just the observation that you can easily derive the behavior of E and M fields for some conductor geometries, like in Veritasium's video).

The long wires act as transmission lines with an easily calculated impedance of ~1 kΩ. When you close the switch, you generate a pulse - a very broadband AC signal - which starts to travel around the circuit. While the pulse is traveling in the line, the line's inputs see the line impedance. So you get the car battery in series with 2x the line impedance in series with the impedance of the light bulb. This directly tells you the amplitude you're going to see near-instantly at the light bulb. Light bulbs are usually low-impedance (e.g. a 10 W, 12 V light has a hot resistance of around 14 Ω), so you're only going to see a tiny pulse on the light bulb. After the pulse has traveled the length of the line and back the impedance seen across the line inputs is the short at the end in series with the conductors resistance of the line itself; in a heavily mismatched setup you're going to see some more reflections going back and forth, this causes the stair-stepped rise over multiple bounces when you do this experiment with "realistic" values.

It's basically a slightly unconventional TDR - time-domain reflectometry - setup.

jakogut
I wonder if the results of this experiment would be the same with alternating current?
pwr-electronics
The topic is about the startup transient, not the steady-state behavior, so it would be the same.
mikewarot
In the AC world, the wire pairs are transmission lines with a characteristic impedance, and this whole thing can be modeled as a bunch of lumped elements.
Flankk
He connected an oscilloscope to the circuit in parallel. The oscilloscope has an unknown level of isolation between probing circuits. It cannot be said that the results are due to anything other than error introduced by the oscilloscope itself without a more rigorous experiment.
ctur
Well I bought a 1,000 ft spool of CAT6a for nothing... beaten to the punch!
gvv
Was expecting a light bulb for the demo? great video but truly TL;DW.
tpush
So, I genuinely do not get the "controversy" over the Veritasium video. AFAIU, the entire point of the video was to show that electricity travels not through wires but via electric fields ("through the air" so to speak).

To illustrate this, he sets up an experiment with parameters such that the conclusion can only mean that some electricity has traveled to the bulb before any could arrive through/around the wires.

He sets up the parameters so that the bulb would turn on by that little electricity; but that is obviously just a visual sign, and his point is valid no matter how much electricity traveled to bulb under whatever different parameters.

It kinda feels like most people are missing the actual point of the video.

GistNoesis
Veritasium's video got my only down-vote of the year because he gave the wrong picture to people.

At first order the bulk of the energy follow the wire like a train on its rails.

Sure you could put a windmill turbine one meter next to the train and the wind from the train passing will make it turn immediately, but no one would argue about that the wind carry most of the energy.

It works this way because the electrons are stuck on the wire like a train is stuck on its rails. The Electro-Magnetic field on the other hand like the wind is free to permeate space. What is important to understand is that electrons and EM-field are two-distinct things that are coupled together.

Derek's video tried to explain transmission line theory, but didn't do the experiment while making grandiose claims about a fictional setup. Kudos to alpha phoenix for doing the experiment.

Given that Derek recently created multiple "debate" videos, and that he is more interested in the way to teach Science and how to reach a lot of people than by Science itself, it feels like he probably has engineered this controversy himself for views as a meta-experiment.

A lot of video responses from unknown youtubers show a better understanding than the original. For example you can see a numerical simulation of the electro magnetic fields (with Ansys) https://youtu.be/aqBDFO1bEs8?t=364 that show how electricity move (the separation distance between the wire there is only a few centimeters).

The problem though is interesting if you try to understand how exactly the energy transfer is happening : Is it capacitive coupling, Is it inductive coupling, Is it EM radiation ? Which one exactly is the dominant term ? Where exactly are the electrons ? How are the electrons interacting with the field ? How can you shield it to isolate and show the various effects (magnetic shielding, electrical shielding) ?

negative_zero
I think the controversy is because that while being technically correct (bar a couple of mistakes) there are two main issues:

1) To get the result presented heavily depends on the experimental setup and this appears to be hand-waved away (or for the cynics: deliberately obscured) as it would detract from the impact of the video.

2) The definition of "ON" in the video is not what anybody would reasonably define as "ON". This is not discussed in the video therefore potentially comes of as deceptive.

As an electronic engineer I actually initially found the video confusing. I wasn't familiar with Veritasium before and I will admit my initial visceral reaction was "Oh he's just one of THOSE YouTube's and needs his clicks".

It wasn't until I went back through to understand Veritasium's unspoken assumptions, simplifications and a couple of medium mistakes that I could say: yes this is technically correct.

Personally I think with some better choice of wording the pitchforks wouldn't have come out as they have.

Edit: Added word for clarity.

BenFrantzDale
His technical errors include the “correct” multiple-choice answer being that the time to turn on is “1/c s”. That evaluates to 3.3e-9 s^2/m. It’s not even a time. Failing basic dimensional analysis is grossly sloppy.
shukantpal
It should be obvious that the "c" here was used as a magnitude not with units. Saying that's "failing dimensional analysis" is in itself grossly sloppy - since it totally misses the context.
BenFrantzDale
But dimensioned quantities are meaningless without units. are you saying c has a value of 1.803e+12? Or that it has a value of 1? There’s a big difference between using furlongs per fortnight and speed of light as your units for speed. By saying “1/c s” rather than “1 m/c” he was just plain wrong and certainly in no position to be smug about it.
shukantpal
That’s like being a grammar Nazi even when someone writes something otherwise totally clear.

And it’s obvious in this case that the magnitude of c was in metric units.

And how do you know if he was even referring to the speed of light by “c”? I could call that a dumb assumption. Because it’s obvious he was using it in a non standard way “magnitude of the speed of light in m/s”.

Phrodo_00
what? c is never a magnitude without units. It's defined as the speed of light, so it's exactly 299792458 m/s
SAI_Peregrinus
1m/cs is the correct value. Not 1/cs. The meters matters, hiding it makes it less obvious that the wire separation is what matters.
elsjaako
If you're going tot quibble about the units, it should be "1m/c". " 1m/c s" gives a result in s².
Lerc
The correct units would have tipped his hand and led people to realize the 1m separation of the wires is relevant and thus people would reconsider antenna approaches. That would blunt the gotcha effect.

That's not sloppy, it's disingenuous.

notfed
I still don't buy "then yes this is correct". If "ON" is defined as a state where ANY electromagnetic field flows into the lightbulb, then it is "ON" even before you throw the switch, because other photons are already shooting around all over the place, including from the neurons in your body pondering the result just before you throw the switch.

The definition of "ON" is exactly the main controversy with this and not a subtle detail.

Ostrogodsky
Yes but that does not generate clicks,views and that sweet youtube money.Sorry but I cannot stand those kind of guys (he, Mark Robber and the likes). Khan academy is doing something 1000000 times more valuable.
kazinator
"ON" is when the filament of the bulb is hot enough to emit far infra-red rays.
tsimionescu
Even if we also accept the unspoken assumption that there are no other photons/electrical fields outside the experiment, the experiment is still wrong, since the battery will produce a teeny tiny electrical field even if the switch is off. This is much more visible if we assume the switch is at one end of the light-second long cables - throwing the switch has little impact on the experiment as explained.
afiori
In my opinion the video made a couple of mistakes, which I think ElectroBoom's response* addresses nicely.

Also its proof using the pointing vector to show the flow of energy is misleading; In the video Derek shows that the energy flows toward the lamp when the circuit is already in a stable configuration, but the point of the video is to explore what happens before the circuit reaches that configuration.

This is relevant: assume that the right half of the cable is connected to the positive pole of the battery, in a stable configuration every point of the right half of the circuit has a positive charge (creating the poynting vector field as shown in the video) while 1/c seconds after the switch was closed the wire just to the right of the lightbulb will have a negative charge (the cable near it is positively charged from the battery and so the upper cable acts as a the negative half of a capacitor) which changes the direction of the poynting vector.

In the end it felt like it was telling you that its message was that energy travels via the fields but what it actually said what that switches cause electric interference.

*https://www.youtube.com/watch?v=iph500cPK28

tigerlily
I thought it was the Poynting vector? Easy to remember because it points in the direction of power flow :)
wiml
Yup, named after English physicist John H. Poynting (1852-1914).
kzrdude
I think "the point is being missed" in the Veritasium video, because it is obscured. It's obscured to increase the "gotcha and unintuitivity factor". Veritasium more or less makes it sound like all the interesting parts of the circuit goes through the direct line-of-sight path between the battery and the light bulb, and ignores the wire. Which is misleading.

Derek would not have written tweets like this one, if his video had been more direct about what he was talking about:

https://twitter.com/veritasium/status/1462115954775654405

"Basically yes - you can think of it like two antennas"

it_does_follow
> some electricity

I think the key part of the controversy is the word "some".

In the original Veritasium video it pretty strongly implies that enough energy to light the bulb, i.e. virtually all the electricity, is traveling instantaneously a short distance rather than "through" the wire.

A big part of that video is to essentially say you're wrong if you understand electrons moving through the wire as how electricity works.

The video posted here tells a different story which is essentially that the mental model of electrons flowing isn't that far off, but there is a bit of nuance when you take into account fields.

This is sort of a persistent problem with "edutainment". I generally enjoy Veritasium, but this is clearly a case where the education component is weakened in order to increase the "wow!" factor of the video.

iraqmtpizza
>you're wrong if you understand electrons moving through the wire as how electricity works

in direct current, how does charge move from one terminal to another if it's not carried by electrons (which often act as waves)?

tsimionescu
It mostly works that way, but not exclusively: the moving electrons in one circuit create an electro-magnetic field that can induce currents in other nearby conductors that are not part of the same circuit.
naasking
Moving charge isn't how power transfer in electricity mainly works, that's the point. Moving electrons is less than half of the story.
XorNot
This is an oversimplification as well though, because the model for current flow is exactly based on moving electrons and that works just fine to predict results.

The battery in the experiment is explicitly based on chemistry which is exactly described as electrons being moved around.

haberman
If electricity doesn't travel through wires, why do resistors dissipate heat?

I'm having trouble understanding what is even being claimed. Electrons are moving, without the movement of the electrons there is no electricity travel, without the wires there is no flow of electrons, so what does it mean to say that electricity doesn't travel through wires?

Is the claim just that the electricity, by way of fields, travels at a rate much faster than the electrons themselves are traveling? That seems like a reasonable claim. But "electricity doesn't travel through wires" seems rather suspect.

userbinator
Energy transfer can take place via electrons and fields. The latter has a common household example: the microwave oven.
jayknight
This is the best demonstration of EM fields I've seen. It kinda demonstrates what Derek was going for, but with resonant antennas the power transfer is way more that his theoretical setup.

https://youtu.be/lslHtCUSfN4

sannee
"Friction". Mechanically, electrons in a metal conductor behave something like a glass bead in honey. Observe that the microscopic Ohm's law says that the velocity is _proportional_ to the force being applied, the electrons do not accelerate as they would in a uniform electric field in vacuum.
elsjaako
The electrical charge travels through the wires. This causes an electrical field and a magnetic field surrounding the circuit.

The point is that the energy goes through the field, not through the wires.

In your example, the Poynting vector would go towards the resistor, where the energy is turned into heat.

tshaddox
> so what does it mean to say that electricity doesn't travel through wires?

I think it’s specifically that the energy flux has a well-defined vector at every point in an electromagnetic field, and those vectors do not point along the wires.

JPLeRouzic
> If electricity doesn't travel through wires, why do resistors dissipate heat?

Thanks, For me this is the best comment in this thread.

tsimionescu
The video seems to make a point that is entirely wrong: that (all/most) energy in a circuit travels directly between the source and the power sinks.

Now, if you follow it carefully, it makes a different point, that is actually correct: it actually claims that some energy travels this way, since the electric field is not strictly bound to the wires, some part of it radiates out.

What the video is sorely missing is a discussion of the intensity of that field, which is going to be extremely low even 1m away from the wires, for typical batteries. These effects are absolutely important though in high power cases, where even a small fraction of the energy carried along the wire leaking to nearby wires still means you can actually light a lightbulb (or burn many other things).

burnte
> It kinda feels like most people are missing the actual point of the video.

I love his videos, but the reason most people are missing the point is because he only obliquely hits the point. The title and thumb are the clickbaitiest he's ever done, and the content does a wide end-run around the facts, rather than tackling them head on. This is also why there are so many rebuttal videos that agree with him and explain it more clearly: he failed to clearly state his argument/explanation. The circumlocutious explanation does little to edify the audience or clarify the concept.

causi
He sets up the parameters so that the bulb would turn on by that little electricity

That's the bit where he's factually wrong. He's made this illogical world where the tiny amounts of electricity in field lines well outside the wire trigger the lamp but the leakage current and other sources of current don't. If you're going to be pedantic about something you have to be pedantic about the whole thing, damn it. Veritasium's video is like saying "water flowing through pipes is a LIE" because some molecules of water make it through the various seals and diffuse across the outer surface of the pipe.

bagels
Also an absurdly long superconductor.
unbanned
I'd say most of his videos fail in similar ways.
formerly_proven
The experiment can be made to work (light bulb actually lighting up ~instantly at a significant brightness), just not with a 12 V bulb.

> Veritasium's video is like saying "water flowing through pipes is a LIE" because some molecules of water make it through the various seals and diffuse across the outer surface of the pipe.

Not at all.

wodenokoto
My take-away from veritsiums video was:

“What’s the point of the wire?”

- it’s not the length of the wire, it’s the distance between power source and consume that determines how fast power travels (how does power “know” where to go, if not following the wire?)

- since power travels outside the wire, it should be okay not to plug in the power consumer.

I’m pretty sure that’s completely and utterly wrong, but I don’t know what he is trying to say. So the video creates more confusion than it clears up.

> It kinda feels like most people are missing the actual point of the video.

Which raises an age old philosophical question about communication: who’s at fault for the misunderstanding: The sender or the receiver?

I’d say it’s a bad video because it is from a trusted source of science and most people misunderstand it.

larrydag
My limited understanding, according to Veritasium, is that the wire is needed to create the electro-magnetic field. Veritasium's claim is the distance of the wire is irrelevant. It's the distance between the battery (power source) and bulb (resistance) is what is relevant. AlphaPhoenix is disputing that claim saying there is a lightspeed electron "wave" through the wires.

I think this is the most fascinating debate on social media currently.

SAI_Peregrinus
Among EEs that I've seen there are only really three points of controversy: the "any current at all turns the bulb on" bit which he didn't mention in the initial pre-video quiz (but which is super important), that he missed the unit of meters in the `1/c seconds` answer (it should be `1m/c seconds`), and (for the pedants & puzzle solvers) that he ignored the interesting bits about steady state behavior.

Nothing (except forgetting the units of meters) he said is wrong. It's just a bit uncharacteristic that the video didn't match the initial quiz, and it ignores some of the most interesting bits of the behavior. But it wasn't targeted at EEs who are already familiar with the "simple" transmission line behavior, it was targeted at people who haven't ever learned or dealt with that. So the steady-state behavior would have distracted from the focus of the video IMO.

tsimionescu
There's also the problem of the switch: Derek's arguments still work for the circuit with the switch still off, since the battery doesn't stop producing an electric field just because the switch is off.
patmcc
The way he describes it implies a speed-of-light violation! He's setting up a scenario where he can transfer information (by ON/OFF of a light) at 1/c.

That's the controversy. It's great that he found a fun way to explain transmission theory and how wires are effectively antennas, but he's taking the same thing he initially calls out (how the general understanding most of us have is a lie) and making it even worse in another direction.

comex
Anecdotally, as a novice, I was left really confused by Veritasium’s video, whereas after watching this video I feel (hopefully accurately) like I basically understand the situation. If people are missing the point of Veritasium’s video, maybe that’s because it didn’t make its point very clearly…
allemagne
I would echo this sentiment. Did this video not confirm exactly what Veritasium claimed (the small but noticeable "instantaneous" i.e. 1/c current)?
notfed
The controversy is that it twists the standard definition of "on": the video boldly asserts its shocking answer of 1/d at first, only later to admit (with very little clarity) that the 1/d answer is only true if your definition of "on" is a small electromagnetic spike.

This also means that the "misconception" claim is really just click-bait and really there was never any misconception.

SAI_Peregrinus
It's d/c, not 1/d.
ehsankia
I think the confusion is that Veratisium's original video made it seem like this was the only/main way electricity travels, whereas in reality, there's two separate ways: One of them take's 1/c and the other takes c/2. Also, what most people think of the light bulb going on in the real world would be the c/2 one, not the 1/c one.
georgyo
What is c/2?

1/c was because the distance between the lightbulb and the battery was 1 meter. m / m/s = s

With c as the numerator, I don't even know what the units of that 2 would be? m/s²?

ehsankia
Err, sorry, I mean't 0.5s, which is option A in Veratisium's video, and the time it actually takes for the current to go through the wire.
nialv7
Not answering your questions but I am so glad this "controversy" exists. I've learned so much more about this topic from all these response videos than I could have if there was no controversy.
sp332
What confused me is that the effect does not actually require the circuit to go through the resistor/lightbulb. Instead of thinking in terms of a delay, you could just have the switch and power supply in their own closed circuit, and the resistor alone with maybe an antenna to boost the effect.
Abishek_Muthian
> AFAIU, the entire point of the video was to show that electricity travels not through wires but via electric fields ("through the air" so to speak).

Only that he doesn't context the video with that, But with a 'trick/googly' question. One of the reasonable constructive criticism I came across for this video is from Mehdi(ElectroBOOM)[1] where he explains why the real answer is not in the options offered by Derrick.

Personally I like the quality of Veritasium videos, but I lately feel that the barometer has shifted towards sensationalism rather than scientific education.

[1] https://www.youtube.com/watch?v=iph500cPK28

tdrdt
Medhi Sadaghdar (Electroboom) explains this. Medhi says the video is right but starts with a trick question. That's what the controversy is about.

https://youtu.be/iph500cPK28

cmroanirgo
EEVblog goes into depth about the video, basically calling it out and explaining the how and why the headline is misleading.

https://youtu.be/VQsoG45Y_00

gcommer
There's two bits of controversy:

1) Slander: He claims that the way EE is taught is a "lie" but leaves out the many ways that standard EE models agree with his result.

2) Clickbait / inadequate explanation: he leaves out many details in order to make his experiment seem far more mind-blowing that it really is.*

Critique 1 can be countered by saying he is targeting a lay audience (say, they took 1 high school physics course).

Critique 2 can be countered by saying he is targeting a slightly more advanced audience who would understand those details (say, 1 or 2 college courses).

But no matter who you think he's talking to, at least one of these critiques holds.

* In particular: a) He doesn't explain how "1/c" is derived from the 1m gap. b) He portrays the electrical field as totally detached from the layout of the wires. But if you rearrange his lightsecond-long wires to be a circle, the effect won't happen. c) He leaves out the fact that this experiment works even if you cut the ends of the wires, which would change many people's intuition (think of the wires more like antennas). d) His thought experiment is actually wrong: see Electroboom's video, but basically by Derek's own parameters the light would _always_ be turned on.

helsinkiandrew
Much of electronic engineering is built around ‘lies’ - abstractions and simplifications because that makes sense in the vast majority of cases but are ‘wrong’ at some level.

You don’t need to use Maxwells equations or the underlying semiconductor physics equations when biasing a transistor, or calculating the output of a digital XOR gate because there are abstractions that are far simpler to use and work in just about all practical situations.

And of course those abstractions break down in thought experiments and beyond their limits in the same way that Newtons laws work up to a point and then you need Einstein.

j4yav
Is this the same channel that made that credulous self-driving car video ad for money and passed it off as an educational video? Seems so: https://news.ycombinator.com/item?id=28949327
dkbrk
> He claims that the way EE is taught is a "lie"

The thing is: this is sort of true. Now, all electrical engineers are very familiar with transmission line theory, that's pretty much their bread and butter. And all EEs know that if you're not working with well-defined transmission lines (like coaxial cables), you need to use a field solver. 2D field solvers are often sufficient, but if not 3D field solvers can and will be used.

And then most of those same EEs, despite having just used a field solver which clearly shows that all the power is in the fields, which are in the dielectric space between the conductors, persist in using the mental model that electrical power moves in wires.

This isn't just a pedantic quibble. There are real, practical effects. If you're designing a PCB and you have two signal lines with overlapping fields, those signals are going to couple, which will create common mode current, which will cause an EMI problem. You can stop those signals coupling by making them reference different ground planes, which makes the fields no longer overlap. If you route a signal line from one side of a ground plane to the other, you have to provide a path for the fields to get to the other side of the ground plane (i.e. "route" the dielectric, generally with a ground via), because if you don't, they will find their own path anyway and you won't like the results.

If you persist in thinking that electrical power flows through wires, these sorts of effects are mysterious and only explicable through the magical black box that is a field solver. If, on the other hand, your mental model is that electrical power is in the fields, then -- surprise! -- the results of a field solver won't be so mysterious any more.

And if you have a more accurate mental model, if you can predict more or less how the fields will behave before looking at the results of the field solver, then that means you can design with the fields in mind, rather than just tweaking things until the field solver stops being angry at you, but not actually understanding why the design works in the end.

Don't believe me? Here's Rick Hartley, an extraordinarily experienced PCB designer: https://www.youtube.com/watch?v=QG0Apol-oj0&t=1102s

I found the responses from other EEs on youtube like Electroboom and EEVBlog disappointing. You can quibble about details of how he presented it (like, saying 1/c rather than 1m/c), but Maxwell's equations are the correct description of how electricity works, and Veritasium is absolutely correct in his core point which is that power flows outside the wires. Other models, such as lumped-element and transmission lines can suffice for many purposes but are ultimately wrong. Rather than responding towards him with hostility, perhaps they should have considered if their own mental models weren't quite as accurate as they had thought.

As a final note, the problem as presented by Veritasium can't be accurately modeled by anything less than Maxwell's equations (i.e. a field solver), but you can get most of the way with transmission line theory and tweaking it with some physical common sense. Closing the switch causes electric and magnetic fields to propagate across the gap between the switch and the light bulb, and down the two transmission lines, at the speed of light (modified by the relative permittivity). The current that will initially flow across the light bulb, once the fields reach it, can be calculated from the characteristic impedance of two parallel wires acting as a transmission line. When the signals reach the end of the transmission lines, they will "see" a short and reflect with opposite voltage; when that opposite-voltage signal reaches the switch and light bulb the transmission lines act like a short and from that point on the light-bulb receives the full current. That 1m/c delay, in particular, isn't accounted for by transmission line theory at all. The way you get that (without a field solver) is by knowing that electrical power is in the fields, which propagate at the speed of light. Since transmission line theory can't accurately model the problem in full, I think Veritasium can be forgiven for not mentioning it (especially since he was targeting a general audience).

jktogjfnn
> Maxwell's equations are the correct description of how electricity works

If you want to be really pedantic, QED is the most accurate description, not Maxwell equations.

gcommer
Is there really an epidemic of EE's who know how to use a field solver, but don't know to consider coupling between signal lines? My intuition is the opposite of yours: most EEs actually know the ideas from the Veritasium video. Therefore, the way EE is taught is not a lie, since it includes that knowledge.

(For completeness, the alternate take is that Veritasium was claiming "the way _elementary_ EE is taught is a lie" -- but that still leaves Veritasium having left out critical context for such an audience)

> I found the responses from other EEs on youtube like Electroboom and EEVBlog disappointing. [...] Rather than responding towards him with hostility, perhaps they should have considered if their own mental models weren't quite as accurate as they had thought.

Personally, I didn't get hostility from any of their videos. They were just injecting some engineering sensibility to bridge the gap between most people's EE knowledge and Derek saying "everything you've been taught is a lie."

Also, to my recollection they both absolutely attested that yes Maxwell's equations are the correct description which supports Derek's results (modulo Electroboom's callout about the bulb actually always being on)

dkbrk
> Is there really an epidemic of EE's who know how to use a field solver, but don't know to consider coupling between signal lines?

Now, I'm not an EE myself, just someone who took undergraduate electrodynamics, decided to read up the subject, and found some truly excellent videos on youtube.

But, at 1:00:23 in that same video I linked before (https://youtu.be/QG0Apol-oj0?t=3623), Rick Hartley says this:

> I spend most of my consulting time solving EMI problems because most of the engineers I meet have no clue about any of this. My job is so easy and I make such a ridiculous amount of money doing it. It's just unbelievable; I solve most EMI problems by simply adding returned vias to boards or changing the positions of decoupling caps, I mean the things are so simple and ridiculous it's amazing and if these guys would educate themselves they wouldn't need to hire me.

So I gather that there is a problem. It's not that EEs don't know to consider coupling between signal lines, but because most of them persist in thinking that signals travel in wires, rather than in the fields, they don't understand when coupling will occur and when it won't. Sure, they can look at the result of the field solver and realize they have a problem, but without thinking in terms of fields they don't know how to solve it. So, they fix it either with trial-and-error until the field solver is happy, or by following design patterns that are passed down as an oral tradition, but without actually understanding why it works or what the problem was in the first place.

Here's an example: https://youtu.be/52fxuRGifLU?t=1719

That's simple to understand if you think in terms of fields. Even worse, if you have signal lines that are parallel and on top of one another (on different planes), referencing the same ground plane from the same side, then it doesn't matter how far apart those planes are, they're going to couple strongly since the fields overlap. You can have two traces right next to each other that have virtually zero coupling because they're stripline, or, if you have a stackup with a single ground plane on the bottom layer, a signal line on top of that, and a signal line on layer one parallel and on top of the bottom trace, they're virtually on opposite sides of the board and yet they'll couple strongly. And if you don't think in terms of fields, you'll observe that, whether in simulation or on a circuit board, and have no idea why it happens or how to fix it.

Here's Rick talking about the state of the industry in the 1980s and 1990s: https://youtu.be/ZYUYOXmo9UU?t=4295. It's clear that no, EEs weren't taught this, they didn't understand it. The situation has, I believe, improved somewhat, but only perhaps in the last decade or two. I would guess that even today, most EEs still don't really understand this (or Rick wouldn't be making so much money consulting).

> Personally, I didn't get hostility from any of their videos.

Perhaps "hostility" is the wrong word. I think on reflection "dismissiveness" is better.

Like, "Yes, we know that Maxwell's Equations are the ground truth. We were all taught that and understand it. But that's not the way practicing engineers work -- we use models like transmission lines and lumped-element. It's technically correct, but more of a curiosity than anything. It's not something we really need to think about, and certainly not useful for a general audience -- more likely to confuse them than anything."

That's the general impression I got. And I think, that not only was Veritasium technically correct, but that model is useful, and most EEs don't use it when they probably should.

Most of us here on hn are software developers. I think that most would probably agree that on the whole, we're all pretty terrible at it. Why would you think Electrical Engineering would be different? Because they're "real" engineers, whereas we just sometimes call ourselves "software engineers" (knowing that's pretty much a lie)?

Here's a presentation by Eric Bogatin that reminded me more than a little of the sort of cargo-cult design patterns that pervade software engineering: https://www.youtube.com/watch?v=y4REmZlE7Jg

jacquesm
EEs tend to be pretty practical in the same sense that mechanical engineers are pretty practical: they build stuff in ways that they (think they) understand to give them as good a chance as producing something that works the first time around. But the devil is in the details and mechanical engineers have one huge advantage: they deal with stuff at a scale where getting it wrong will have visible consequences. An electrical engineer getting their assumptions about electric fields emanation wrong is going to have a difficult problem to solve, electric fields don't readily visualize and without a very solid understanding of the theory it is extremely easy to mess this up. This is one reason why people tend to be conservative, if you do it 'like it is usually done' then the chances of discovering new and potentially expensive ways to mess it up go down a bit.

I once - long ago - rebuilt a transmitter that I had designed using 'regular' components in the air on a circuit board. It took 6 tries to get it perfect, and every time I learned about a new assumption that wasn't exactly spelled out anywhere but that really made a huge difference in how the circuit operated.

The electrical schematic was identical every time, the only thing that changed was the topology in space. And the difference between iteration #1 and iteration #6 from a performance point of view was huge, much larger than you would have ever thought could be the consequence of the very subtle changes to the various trace geometries.

No matter how much you know - or don't know - about the way electrical fields interact with each other be prepared to be surprised, this stuff is simply hard when your circuitry goes beyond a minimum level of complexity.

Interesting tidbit: many years later when designing the windmill stator/rotor/coil assembly some of this knowledge came in quite handy.

tda
Did you perhaps mean you changed the geometry instead of topology? Your comment got me wondering if you can change the topology without changing the schematics and I now think you can, as a schematic only defines the electrical connections and the topology is I think also the non electrical relations (what component is next to what). As far as I know topology is strictly dimensionless; size and distance are properties of the geometry. If I were not on HN I would apologise for the pedantry, but here we are
jacquesm
You are right, I should have used geometry.
pwr-electronics
There's nothing deficient about transmission lines or lumped element models for answering the riddle. Distributed element models of transmission lines [1] clearly show a straight line path directly from the battery to the bulb without going through the whole wire.

Electroboom's criticism is that even if you're not misdirected by the setup, there's still a missing assumption required to arrive at the same answer as Veritasium.

[1] https://en.m.wikipedia.org/wiki/File:Line_model_Heaviside.sv...

hex4def6
I think you're correct for the most part. I think us EEs tend to compartmentalize the information we've learned in school; while we may technically have all the "tools", knowing when to apply that knowledge isn't always apparent.

I definitely think there is a lack of applied EE knowledge; PCB layout with an emphasis on signal integrity etc would make an excellent undergrad course in school.

In terms of PCB layout -- Eric & Rick have been absolute goldmines in terms of the knowledge they've put out there. I can also say that both of the FAANG companies I worked with sent us EEs to their training seminars, which were super useful (and shows that there is recognition in the industry that EEs need better training on these sorts of issues). I also think there is a bit of an art to it -- you learn when layout issues are significant or not, and can identify them by eye. This is something you learn by experience. For me, I've found field solvers are a great way to validate / hone my intuition.

jacquesm
> PCB layout with an emphasis on signal integrity etc would make an excellent undergrad course in school.

This is strongly frequency and wave-form dependent. Just the difference between square waves and sine waves and say a few KHz to a few 10's of MHz can have dramatic consequences on how hard it will be to get a circuit to behave in the way you intended it to.

I think one of the bigger insights you can have when designing circuitry is that you may be working on a digital circuit but from an electrical engineering point of view digital simply doesn't exist, that's just a signalling convention, there is only analog.

dkbrk
I think it was in one of Rick Hartley's videos that he talked about designing for analog vs digital. There are a bunch of points I remember, in no particular order:

- the frequency of your circuit, that you need to design for, is determined by the rise and fall time of your ICs, not your clock. (With your square wave, for example, it's impossible for it to actually be square; it has some finite rise and fall time that determines the frequency you need to design to).

- IC manufacturers almost never actually tell you the rise and fall time of their chips. Also, they might do a die shrink at any time, resulting in you having to redesign your circuit to accommodate the higher frequencies from smaller, faster transistors (even if it operates at exactly the same clock frequency as before). If you're lucky, they'll even tell you about the die shrink rather than just letting you find out when suddenly your design stops passing EMI testing.

- high-frequency can be easier than low-frequency; you really need to pay attention to impedance control, but so long as everything is well laid-out the fields will stay closely contained. The lower the frequency, the more the fields will spread and the greater the risk of having problems such as crosstalk.

- Digital is easier than analog. Digital can tolerate a lot of noise before a 0 becomes a 1 or vice versa. Whereas if you're sending a signal to a 24-bit ADC, you might have to go a bit crazy and use a PCB-embedded waveguide, or something, to give it the isolation it needs.

- Even if digital signals are quite resilient from a signal integrity standpoint, you still have to pay close attention to crosstalk because it takes very little common mode current to cause an EMI problem. And you have to pay attention to EMI if you actually want your design to pass emissions testing to be able to sell it.

- Even at high frequencies, anything at a length scale less than (wavelength of maximum frequency)/10 can be treated as a lumped element. So if it's possible to jam two high-frequency ICs right up against one another, with the pads pretty much touching, that's probably actually better than a carefully impedance-controlled transmission line connecting them. That's not really applicable to some monster BGA chip, but if you're designing a switched-mode power supply you can make the node between the inductor and MOSFET a lumped element by placing them as close as possible.

jacquesm
Good stuff this.
charcircuit
Why wouldn't the effect happen with a circle? Shouldn't the same thing happen just with more delay since they are more separated?
wtallis
In the case of a circle, you should still have a radiated signal that arrives before the conducted signal. But it would be far weaker, further compounding the problems with the "light bulb illuminating" way of illustrating that a signal has arrived. In the original experimental design, it was already reckless at best to leave the viewer with the impression that the radiated signal was capable of powering the light bulb rather than merely serving as a trigger for a self-powered light. With a circular setup, I doubt that equipment sensitive enough to detect the arriving radiated signal (and reliably distinguish it from other electromagnetic noise) could even fit into the light bulb's black box.
jonsen
The increased distance between the two points of measurement to be compared would also complicate matters.
lamontcg
The problem is that his video is a mish-mash of two different concepts that were taught perfectly well in my freshman physics course. One is that the electric field travels down a wire at the speed of light while the electrons do not. The other is induced currents by moving charges.

I got the answer "wrong" by watching the video because I didn't consider the tiny amount of current induced in the other wire to be sufficient to turn on the light in any useful manner. If you had replaced the light with a sensitive ammeter and asked me what the first point in time there would be any measurable deflection from zero, then I would have gotten it correct.

Could have also just asked how this works, and the success rate would have gone way up (but he'd have lost all his clickbait):

https://www.amazon.com/Fluke-324-Temperature-Capacitance-Mea...

Ask bad questions, get bad answers. Nothing wrong with how physics/EE is taught.

kzrdude
The video explicitly says that this is wrong: "the electric field travels down a wire".

I don't agree, but that's the confusing claim it makes, that the wire should not be in the statement.

phendrenad2
This is exactly it. If being "right" or "wrong" about something involves subjective facts (is the lamp "lit" by the small amount of electricity induced by cosmic rays too?!?!) and trying to visually inspect an experiment you can't access in-person, then the only thing "wrong" is the video maker.
ReactiveJelly
"Communicating badly and then acting smug when you're misunderstood" https://xkcd.com/169/
BrazzVuvuzela
Let's not forget that Derek's PhD thesis was about the practice of making videos that dunk on unsuspecting members of the general public.
thunderbong
I don't think there is any need to be snarky here.

Link to his PhD thesis (PDF) - https://www.sydney.edu.au/science/physics/pdfs/research/supe...

BrazzVuvuzela
I'm not being snarky, the formula of his videos at the time was 1) Ask somebody in a public park a science question. 2) They get it wrong. 3) Explain why they're wrong. His thesis was about the supposed efficacy of this style of video (which he has since moved on from, to his credit.)
alisonkisk
You should look at the thesis before embarassing yourself further.
Dec 17, 2021 · 3 points, 0 comments · submitted by peterwallhead
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