Electricity faster than light - Page 1
Forum section: electronics / general

author: 5ky
author_rank: Regular Contributor
timestamp: November 13, 2015, 08:38:25 pm
content: Saw this on reddit and thought that it could make for an interesting video. (make sure you read both the original picture, as well as some of the comments)https://www.reddit.com/r/askscience/comments/3sm2jj/my_textbook_says_electricity_is_faster_than_light/

author: c4757p
author_rank: Super Contributor
timestamp: November 13, 2015, 08:59:41 pm
content: Utter crap being published by Cengage Learning?You don't say.From what I've seen, they just plain don't have standards.

author: Simon
author_rank: Unknown
timestamp: November 13, 2015, 09:02:29 pm
content: Quote from: c4757p on November 13, 2015, 08:59:41 pmMaybe they are a subsidry of ICS LearnSurely it still takes time for the electrons to "push" each other to the point that one is forced out of the other end. surely if this was the case I could reduce my RAM latency and not have my PC crash because I am trying to move charges (electrons) faster than the speed of light.....

author: c4757p
author_rank: Super Contributor
timestamp: November 13, 2015, 09:08:03 pm
content: Quote from: Simon on November 13, 2015, 09:02:29 pmThey went and complicated the problem by running one side of the circuit down a very long transmission line and the other side down a very short one - the propagation delaymaybe closer to that of the short side of the circuit rather than the long side (sure as hell still not faster than light), or somewhere in between - depends on how closely coupled the circuit is to the transmission line's reference plane, which isn't particularly well defined the way they decided to do this...

author: c4757p
author_rank: Super Contributor
timestamp: November 13, 2015, 09:16:52 pm
content: Here's a simulation.So the light does "immediately" (for definitions ignoring the smaller tlines in this circuit) conduct current - but not full current, Vbattery/(2Z0), which depending on the lamp and voltage could be not even enough to make it glow a bit. Then the current steps up to full current a bit at a time as the waves bounce back and forth between the ends of the transmission line. It doesn't even get to 90% of full current until 9.5 times the propagation delay.

author: Circlotron
author_rank: Super Contributor
timestamp: November 13, 2015, 09:20:22 pm
content: At least the book is talking about electron flow, not conventional current flow. 200 years ago they didn't know which direction electric current flowed so they took a guess and they got it wrong. Some people still won't admit it.Maybe conventional current flows faster than light?...

author: c4757p
author_rank: Super Contributor
timestamp: November 13, 2015, 09:24:20 pm
content: Quote from: Circlotron on November 13, 2015, 09:20:22 pmPolarity is arbitrary, positive and negative are just words. We could have renamed electrons "positive" instead of swapping the current direction and everything would have carried on working. And for thevastmajority of things, you don't even care how things flow with respect to the electrons. It's only when you get to the semiconductor physics level that it starts to matter.

author: MatthewEveritt
author_rank: Unknown
timestamp: November 19, 2015, 05:16:01 pm
content: Wow, that is impressively wrong. I particularly like the part where they base the explanation on balls in a tube, neglecting to consider that in interaction of the ball is, like electrons, via an EM field and propagates at or below c.You can see the thinking :Pushes propagate instantaneously (I'VE never seen the delay so OBVIOUSLY the delay is zero! Totally unlike light.)Electrons are basically little balls in tubes (that's how the internet works don't cha'know.)Therefore electricity must go faster than light!Take THAT science!edit: I agree that this could be an interesting video though, explaining what's wrong with the picture and giving an example of what actually happens. Come to think of it, a good long reel of cable would give an easily measurable delay, so you could rig up a bulb / switch / photo-sensor and compare a whole reel to a short length and a bulk equivalent circuit. Could be fun.

author: Circlotron
author_rank: Super Contributor
timestamp: November 20, 2015, 01:49:07 am
content: Obviously a batteriser would make electrons go faster than light.

author: mswhin63
author_rank: Frequent Contributor
timestamp: November 21, 2015, 07:38:19 am
content: A single obvious typo somewhereThis thread "Electricity is faster than light"The book " Electricity appears faster than light"Who got it wrongSure it is complicating a topic on electricity but Chinese whispers make this appear worse than it already is. For simplicity sake "signal" travel close to the speed of light but electron flow is extremely slow. So it seems that everyone got it wrong.

author: DimitriP
author_rank: Super Contributor
timestamp: November 21, 2015, 08:04:19 am
content: Quote from: mswhin63 on November 21, 2015, 07:38:19 amI'd like to see light goaroundthe earth 10 times or even onceI

author: timb
author_rank: Super Contributor
timestamp: November 21, 2015, 09:32:26 am
content: QuoteIt would create an electromagnet, causing the earth to either stop spinning or spin faster, flinging us all out into space or crushing us all under immense gravity?Not to mention the impedance of a wire that long would be enormous! Where would you get enough power!?Sent from my Tablet

author: timb
author_rank: Super Contributor
timestamp: November 21, 2015, 09:43:36 am
content: Also, I have a simple question for the author: My oscilloscope has a delay line in it. If electricity (and tennis balls) come out the other end instantaneously it can't very well delay anything, now can it? But it does.Sent from my Tablet

author: DimitriP
author_rank: Super Contributor
timestamp: November 21, 2015, 11:42:09 am
content: Quote from: blueskull on November 21, 2015, 08:18:19 amI see what you did there, what I didn't "see" is light

author: Simon
author_rank: Unknown
timestamp: November 21, 2015, 11:46:08 am
content: seems communicating across the atlantic is faster than by wifi in my house.

author: miguelvp
author_rank: Super Contributor
timestamp: November 21, 2015, 12:12:16 pm
content: Let's see, minimum ping of 230ms and Earth's circumference of 40,075 km gives 174,239,130.5 m/scompared to 299,792,458 m/s that is the speed of light.Still not too shabby, but since you mentioned the northern hemisphere then the path will be shorter.Impressive number anyways

author: Simon
author_rank: Unknown
timestamp: November 21, 2015, 12:14:12 pm
content: That looks about right. there will be some copper there and the speed in copper is about 1/2 plus you have the reaction time of every switch in between so to come up with just over half the speed of light is pretty good.

author: Marco
author_rank: Super Contributor
timestamp: November 21, 2015, 12:53:13 pm
content: Group velocity can be faster than light, but really it's just a curious kind of pulse distortion and semantic confusion.

author: wraper
author_rank: Unknown
timestamp: November 21, 2015, 01:10:06 pm
content: Quote from: Circlotron on November 13, 2015, 09:20:22 pmElectric current is not always electron flow. It can be positively charged particle flow in opposite direction too, like ions in the batteries.

author: han
author_rank: Frequent Contributor
timestamp: November 21, 2015, 01:20:24 pm
content: Light in Optical cable:G.652D IOR @ 1310 nm. 1.467 68.17% VFElectrical in cableVF% Transmission line95-99 Open-wire "Ladder" Line80 Belden 9085 twin-lead82 RG-8X Belden 9258 coaxial cable (foamed polyethylene dielectric)66 RG-213 CXP213 coaxial cable (solid polyethylene dielectric)

author: madires
author_rank: Super Contributor
timestamp: November 21, 2015, 02:21:40 pm
content: Quote from: Simon on November 21, 2015, 11:46:08 amHigher bit rate and larger latencyA single line of an undersea cable would be 10 Gbit/s or 40 Gbit/s (a WDM color), which is a little bit more than your WiFi. But your WiFi has a latency of a few ms. A trans-atlantic line got 80ms.

author: madires
author_rank: Super Contributor
timestamp: November 21, 2015, 02:29:55 pm
content: Quote from: blueskull on November 21, 2015, 08:18:19 amPlease try a sat link500+ ms

author: SteveLy
author_rank: Regular Contributor
timestamp: November 21, 2015, 04:56:20 pm
content: It's the same idea as having a rigid rod and how pushing one end would seem to instantly cause the other end to move. It's wrong. Disturbances never travel faster than the speed of light.Some explanations here:http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html- see section 4 "Rigid Bodies" for a refutation of the mechanical analogue of the the electricity-faster-than-light claim.

author: HighVoltage
author_rank: Super Contributor
timestamp: November 22, 2015, 11:44:31 am
content: I think it was about 20 years ago, when I read a science report on the "Transphasor", a transistor that worked only with light. It was promised that the switching speed of the transphasor would be a 1000 times faster, compared to an electricity transistor. I am not sure what happened to this project

author: FireFlower
author_rank: Regular Contributor
timestamp: November 30, 2015, 10:18:44 pm
content: Well speed of the light is accepted theory as fastest unit ever and nothing can surpass it. If you think out of box, come plausible theory and somebody is able to measure it then we have 100 years of physics a bit wrong here and there.Like original relation theory wasn't able to explain photons but newer one can explain them. Judging on internet is something wrong or true without reading the whole concept and understanding its principles you can pretty much give guess is it true or not. Current accepted theory says electricity is almost able to archive speed of the light but in future we might have something different wrong electricity or light. Maybe we are transferring gravity particles that surpass speed of light?As said I failed Modern University physics with advanced relation theory because I didn't pay attention but it is not yet law.

author: tggzzz
author_rank: Super Contributor
timestamp: November 30, 2015, 11:11:14 pm
content: Quote from: FireFlower on November 30, 2015, 10:18:44 pmNo, and maybe that's the reason your first statement is wrong.Here is a pretty picture of what happens when thingsdotravel faster than light:http://i.kinja-img.com/gawker-media/image/upload/s--q8KBrnCw--/c_scale,fl_progressive,q_80,w_800/tjbxqdg3awnwvup1ovva.jpgFFI, google Cerenkov radiation.

author: coppice
author_rank: Super Contributor
timestamp: December 01, 2015, 05:55:25 am
content: Quote from: tggzzz on November 30, 2015, 11:11:14 pmWhen you say "things" I assume you include non-physical things, like phase. So far nothing physical (matter or energy) is known to travel faster than light.

author: tggzzz
author_rank: Super Contributor
timestamp: December 01, 2015, 11:42:42 am
content: Quote from: coppice on December 01, 2015, 05:55:25 amFalse.Cherenkov radiation is caused by subatomic particlesslowing downto the speed of light. Please do at least a little research by googling for the obvious keyword.

author: kony
author_rank: Regular Contributor
timestamp: December 01, 2015, 12:12:51 pm
content: Quote from: tggzzz on December 01, 2015, 11:42:42 amYes, it isslowing downtoa speed of light, but not in absolute terms - it speeds down to a velocity of light given by the dielectric properties of the material it propagates in. Compared to speed of light in vacuum in absolute terms trough, the particle velocity is still less, despite it might be farily close.To illustrate more the struggle of accelerating particles to a speeds close to that of photons in vacuum - I'm sure you heard about CERN, did you?

author: coppice
author_rank: Super Contributor
timestamp: December 01, 2015, 12:31:55 pm
content: Quote from: tggzzz on December 01, 2015, 11:42:42 amMaybe you need to Google for what phase velocity means and exactly which velocity of light the Cherenkov radiation goes faster than before replying.

author: tggzzz
author_rank: Super Contributor
timestamp: December 01, 2015, 12:57:11 pm
content: Quote from: coppice on December 01, 2015, 12:31:55 pmIf you look at what you wrote, you will see you didn't mention "phase velocity", only "phase".Speed of light in water ~0.75c. Particles are travelling between 0.75c and c, i.e. faster than the speed of lightin water.Your statementwouldbe correct if you had stated "So far nothing physical (matter or energy) is known to travel faster than lightIN VACUUM". But that wasn't your statement!But even that isn't strictly true as has been observed by astronomers - they have seen the reflections of a light beam travelling across the sky faster than the speed of light. Of course, you can't convey any information that fast, but the the spotistravelling faster than light! So yes, that is a "cheat" albeit a real one

author: coppice
author_rank: Super Contributor
timestamp: December 01, 2015, 01:02:04 pm
content: Quote from: tggzzz on December 01, 2015, 12:57:11 pmSince you started this by saying "Well speed of the light is accepted theory as fastest unit ever and nothing can surpass it. " is incorrect, you seem to be sliding your position.

author: tggzzz
author_rank: Super Contributor
timestamp: December 01, 2015, 01:03:12 pm
content: Quote from: kony on December 01, 2015, 12:12:51 pmThey are slowing down tothespeed of light (in water, as you say!). That, of course, wasn't the original statement.BTW, I have worked at CERN, albeit not on particle physics. It was amusing to sit on the "seat" of an obsolete-but-functional Cray-1, and when I wanted a cup of coffee I had to cross the border and go to a different country (France vs Switzerland)

author: coppice
author_rank: Super Contributor
timestamp: December 01, 2015, 01:04:53 pm
content: Quote from: tggzzz on December 01, 2015, 01:03:12 pmI have worked at Rutherford Appleton Labs, but on the control systems and not the physics. What's your point?

author: tggzzz
author_rank: Super Contributor
timestamp: December 01, 2015, 01:06:36 pm
content: Quote from: coppice on December 01, 2015, 01:04:53 pmQue? The point is contained in the quoted conversation.

author: Brumby
author_rank: Unknown
timestamp: December 05, 2015, 06:37:34 am
content: My thoughts do not encompass anything more than the question: "How did this publication ever become a textbook?"Words fail me. I need a Dave "Aaarrgghhhhh!!!"