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I bought 1000 meters of wire to settle a physics debate [video]

434 points by indosauros 5y ago

0xTJ 5y ago
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.
- randyrand 5y ago
  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 5y ago
    I'm not an avid Veritasium viewer but from what I've seen this MO seems to be kinda his shtick.
    - Jansen312 5y ago
      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 5y ago
        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.
        Ostrogodsky 5y ago
        This is the youtube generation. Entertainment, clicks and wow factor first (and money of course), facts a distant second.
        kzrdude 5y ago
        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 5y ago
        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 https://www.youtube.com/watch?v=CM0aohBfUTc
- vexxed-concave 5y ago
  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.
  - GenerocUsername 5y ago
    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.
  - JshWright 5y ago
    > 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".
- paxys 5y ago
  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 5y ago
    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 5y ago
    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.
    - function_seven 5y ago
- jacobolus 5y ago
  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 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.)
  - kongolongo 5y ago
    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 5y ago
      Successful professors can get to the point where they’re no longer interacting much with people who disagree with them.
  - QuantumG 5y ago
    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.
- Laremere 5y ago
  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?
  - systemvoltage 5y ago
    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.
  - teddyh 5y ago
    Once the light and battery are far apart, I have a horrible suspicion that the definition of simultaneity will become problematic.
  - NikolaeVarius 5y ago
    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 5y ago
      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
- leafmeal 5y ago
  Here's the link if you're as curious as me https://www.youtube.com/watch?v=bHIhgxav9LY https://www.youtube.com/watch?v=bHIhgxav9LY
- JshWright 5y ago
  > 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.
  - pclmulqdq 5y ago
    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 5y ago
      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.
  - jarenmf 5y ago
    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 5y ago
      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 5y ago
- 01100011 5y ago
  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.
csense 5y ago
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 5y ago
  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.
- colechristensen 5y ago
  I’m not a fan of the “big leagues” of science YouTube, many seem to have been tainted by the attention algorithm game.
  - frosted-flakes 5y ago
    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.
    - rectang 5y ago
      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...
    - motoxpro 5y ago
      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.
jakogut 5y ago
I wonder if the results of this experiment would be the same with alternating current?
- mikewarot 5y ago
  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.
- deleted 5y ago
  [deleted]
everybodyknows 5y ago
Anyone care to give us a Too Long; Didn't View?
- wdfx 5y ago
  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.
- umvi 5y ago
  200uA of current flows through the lightbulb instantly, but it doesn't reach full current until speed of light delay.
  - nathan_f77 5y ago
    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.
    - jstimpfle 5y ago
      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 5y ago
      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.
    - 5y ago
lmilcin 5y ago
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.
- soneil 5y ago
  That's fairly intuitive. The lower current being present before the signal arrives is not intuitive.
  - deleted 5y ago
    [deleted]
  - sega_sai 5y ago
    I just arrives through the air. The electromagnetic wave will propagate with similar speeds through the air and wire.
    - soneil 5y ago
      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 5y ago
        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.
ctur 5y ago
Well I bought a 1,000 ft spool of CAT6a for nothing... beaten to the punch!
formerly_proven 5y ago
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.
mikewarot 5y ago
I just bought 2 light seconds of 0000 AWG bare copper for no good reason. Fortunately Gallifrey Prime has easy returns. ;-)
nathan_f77 5y ago
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 5y ago
  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 5y ago
  Did you finish the video? He explained that it was capacitive coupling.
- formerly_proven 5y ago
  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.
- deleted 5y ago
TempestSA 5y ago
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?
- jayd16 5y ago
  It's not a trick question if you explain the trick up front.
- Jansen312 5y ago
  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 5y ago
    >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 5y ago
      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 5y ago
        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.
zokier 5y ago
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.
- ehsankia 5y ago
  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.
- blamazon 5y ago
  I wouldn’t have even heard about the Veritasium film if not for this response. Smart marketing play.
- formerly_proven 5y ago
  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.
amelius 5y ago
This is basic transmission line theory. https://en.wikipedia.org/wiki/Transmission_line https://en.wikipedia.org/wiki/Transmission_line
- tgsovlerkhgsel 5y ago
  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 5y ago
    You should watch Electroboom's analysis if you want the full details from an electrical engineer: https://youtu.be/iph500cPK28 https://youtu.be/iph500cPK28
  - vmilner 5y ago
    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 5y ago
      Great book on the topic: https://openlibrary.org/works/OL3347773W/A_Thread_Across_the_Ocean https://openlibrary.org/works/OL3347773W/A_Thread_Across_the... https://smile.amazon.com/Thread-Across-Ocean-Heroic-Transatlantic/dp/0060524464 https://smile.amazon.com/Thread-Across-Ocean-Heroic-Transatl...
- jjoonathan 5y ago
  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 https://en.wikipedia.org/wiki/Twin-lead#Ladder_line
parhamn 5y ago
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- renewiltord 5y ago
  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 5y ago
    Glad you like it! Email me directly at parham@synth.app so I make sure I don't miss it :)
tpush 5y ago
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.
- comex 5y ago
  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 5y ago
  I would echo this sentiment. Did this video not confirm exactly what Veritasium claimed (the small but noticeable "instantaneous" i.e. 1/c current)?
  - ehsankia 5y ago
    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 5y ago
      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?
soheil 5y ago
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 5y ago
  Trolling 2.0?
Flankk 5y ago
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.
MarkusWandel 5y ago
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.
- throw0101a 5y ago
  > 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://www.youtube.com/watch?v=9eyFDBPk4Yw * https://en.wikipedia.org/wiki/Grace_Hopper https://en.wikipedia.org/wiki/Grace_Hopper Full lecture: * https://www.youtube.com/watch?v=ZR0ujwlvbkQ https://www.youtube.com/watch?v=ZR0ujwlvbkQ
- m348e912 5y ago
  >>Light is slow I am going to have to go ahead and disagree with you on that
  - layer8 5y ago
    Most stuff in the universe is moving apart faster than light, so yes it’s quite slow. ;)
    - userbinator 5y ago
      ...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.
yholio 5y ago
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.
y04nn 5y ago
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.
- 01100011 5y ago
  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 5y ago
    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.
- userbinator 5y ago
  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 5y ago
    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 https://youtu.be/LMxate9gegg?t=104
- 5y ago
kazinator 5y ago
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 5y ago
  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.
griffinheart 5y ago
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 5y ago
  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 5y ago
    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 5y ago
      That's correct.
gvv 5y ago
Was expecting a light bulb for the demo? great video but truly TL;DW.
axegon_ 5y ago
Setting the obvious facts aside, I love the subtle cynicism behind buying a 1km cable to prove a point.
thehappypm 5y ago
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.

434 points by indosauros 5y ago

0xTJ 5y ago

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.

randyrand 5y ago
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 5y ago
  I'm not an avid Veritasium viewer but from what I've seen this MO seems to be kinda his shtick.
  - Jansen312 5y ago
    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 5y ago
      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.
      - Ostrogodsky 5y ago
        This is the youtube generation. Entertainment, clicks and wow factor first (and money of course), facts a distant second.
      - kzrdude 5y ago
        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 5y ago
        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 https://www.youtube.com/watch?v=CM0aohBfUTc
vexxed-concave 5y ago
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.
- GenerocUsername 5y ago
  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.
- JshWright 5y ago
  > 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".
paxys 5y ago
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 5y ago
  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 5y ago
  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.
  - function_seven 5y ago
jacobolus 5y ago
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 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.)
- kongolongo 5y ago
  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 5y ago
    Successful professors can get to the point where they’re no longer interacting much with people who disagree with them.
- QuantumG 5y ago
  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.
Laremere 5y ago
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?
- systemvoltage 5y ago
  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.
- teddyh 5y ago
  Once the light and battery are far apart, I have a horrible suspicion that the definition of simultaneity will become problematic.
- NikolaeVarius 5y ago
  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 5y ago
    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
leafmeal 5y ago
Here's the link if you're as curious as me https://www.youtube.com/watch?v=bHIhgxav9LY https://www.youtube.com/watch?v=bHIhgxav9LY
JshWright 5y ago
> 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.
- pclmulqdq 5y ago
  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 5y ago
    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.
- jarenmf 5y ago
  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 5y ago
    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 5y ago
01100011 5y ago
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.

csense 5y ago

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 5y ago
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.
colechristensen 5y ago
I’m not a fan of the “big leagues” of science YouTube, many seem to have been tainted by the attention algorithm game.
- frosted-flakes 5y ago
  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.
  - rectang 5y ago
    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...
  - motoxpro 5y ago
    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.

jakogut 5y ago

I wonder if the results of this experiment would be the same with alternating current?

mikewarot 5y ago
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.
deleted 5y ago
[deleted]

everybodyknows 5y ago

Anyone care to give us a Too Long; Didn't View?

wdfx 5y ago
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.
umvi 5y ago
200uA of current flows through the lightbulb instantly, but it doesn't reach full current until speed of light delay.
- nathan_f77 5y ago
  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.
  - jstimpfle 5y ago
    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 5y ago
    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.
  - 5y ago

lmilcin 5y ago

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.

soneil 5y ago
That's fairly intuitive. The lower current being present before the signal arrives is not intuitive.
- deleted 5y ago
  [deleted]
- sega_sai 5y ago
  I just arrives through the air. The electromagnetic wave will propagate with similar speeds through the air and wire.
  - soneil 5y ago
    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 5y ago
      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.

ctur 5y ago

Well I bought a 1,000 ft spool of CAT6a for nothing... beaten to the punch!

formerly_proven 5y ago

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.

mikewarot 5y ago

I just bought 2 light seconds of 0000 AWG bare copper for no good reason. Fortunately Gallifrey Prime has easy returns. ;-)

nathan_f77 5y ago

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 5y ago
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 5y ago
Did you finish the video? He explained that it was capacitive coupling.
formerly_proven 5y ago
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.
deleted 5y ago

TempestSA 5y ago

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?

jayd16 5y ago
It's not a trick question if you explain the trick up front.
Jansen312 5y ago
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 5y ago
  >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 5y ago
    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 5y ago
      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.

zokier 5y ago

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.

ehsankia 5y ago
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.
blamazon 5y ago
I wouldn’t have even heard about the Veritasium film if not for this response. Smart marketing play.
formerly_proven 5y ago
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.

amelius 5y ago

This is basic transmission line theory. https://en.wikipedia.org/wiki/Transmission_line https://en.wikipedia.org/wiki/Transmission_line

tgsovlerkhgsel 5y ago
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 5y ago
  You should watch Electroboom's analysis if you want the full details from an electrical engineer: https://youtu.be/iph500cPK28 https://youtu.be/iph500cPK28
- vmilner 5y ago
  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 5y ago
    Great book on the topic: https://openlibrary.org/works/OL3347773W/A_Thread_Across_the_Ocean https://openlibrary.org/works/OL3347773W/A_Thread_Across_the... https://smile.amazon.com/Thread-Across-Ocean-Heroic-Transatlantic/dp/0060524464 https://smile.amazon.com/Thread-Across-Ocean-Heroic-Transatl...
jjoonathan 5y ago
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 https://en.wikipedia.org/wiki/Twin-lead#Ladder_line

parhamn 5y ago

I took some notes through the first part here: https://synth.app/s/JeJYQgwxey8 https://synth.app/s/JeJYQgwxey8 if you're on the go and can't watch.

renewiltord 5y ago
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 5y ago
  Glad you like it! Email me directly at parham@synth.app so I make sure I don't miss it :)

tpush 5y ago

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.

comex 5y ago
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 5y ago
I would echo this sentiment. Did this video not confirm exactly what Veritasium claimed (the small but noticeable "instantaneous" i.e. 1/c current)?
- ehsankia 5y ago
  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 5y ago
    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?

soheil 5y ago

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 5y ago
Trolling 2.0?

Flankk 5y ago

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.

MarkusWandel 5y ago

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.

throw0101a 5y ago
> 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://www.youtube.com/watch?v=9eyFDBPk4Yw * https://en.wikipedia.org/wiki/Grace_Hopper https://en.wikipedia.org/wiki/Grace_Hopper Full lecture: * https://www.youtube.com/watch?v=ZR0ujwlvbkQ https://www.youtube.com/watch?v=ZR0ujwlvbkQ
m348e912 5y ago
>>Light is slow I am going to have to go ahead and disagree with you on that
- layer8 5y ago
  Most stuff in the universe is moving apart faster than light, so yes it’s quite slow. ;)
  - userbinator 5y ago
    ...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.

yholio 5y ago

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.

y04nn 5y ago

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.

01100011 5y ago
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 5y ago
  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.
userbinator 5y ago
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 5y ago
  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 https://youtu.be/LMxate9gegg?t=104
5y ago

kazinator 5y ago

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 5y ago
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.

griffinheart 5y ago

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 5y ago
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 5y ago
  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 5y ago
    That's correct.

gvv 5y ago

Was expecting a light bulb for the demo? great video but truly TL;DW.

axegon_ 5y ago

Setting the obvious facts aside, I love the subtle cynicism behind buying a 1km cable to prove a point.

thehappypm 5y ago

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.