Electricity faster than light

[5ky]

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/

[c4757p]

Utter crap being published by Cengage Learning? You don't say.

From what I've seen, they just plain don't have standards.

[Simon]

Utter crap being published by Cengage Learning? You don't say.

From what I've seen, they just plain don't have standards.

Maybe they are a subsidry of ICS Learn 

Surely 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.....

[c4757p]

Surely 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.....

They 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 delay may be 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...

[c4757p]

Here's a simulation.

So the light does "immediately" (for definitions ignoring the smaller tlines in this circuit) conduct current - but not full current, V_battery/(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.

[Circlotron]

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?...

[c4757p]

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. 

Polarity 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 the vast majority 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.

[MatthewEveritt]

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.

[Circlotron]

Obviously a batteriser would make electrons go faster than light.

[mswhin63]

A single obvious typo somewhere

This thread "Electricity is faster than light"

The book " Electricity appears faster than light"

Who got it wrong

Sure 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.

[DimitriP]

A single obvious typo somewhere

This thread "Electricity is faster than light"

The book " Electricity appears faster than light"

Who got it wrong

Sure 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.

I'd like to see light go around the earth 10 times or even once  
I

[timb]

...if a wire were wrapped around Earth 10 times...

It 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

[timb]

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

[DimitriP]

I'd like to see light go around the earth 10 times or even once  

Sino-US Atlantic optical fiber run across half the north hemisphere, so technically a round trip ping packet will travel around the world, in the form of light (optical fiber).

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\Users\User>ping www.baidu.com

Pinging www.a.shifen.com [103.235.46.39] with 32 bytes of data:
Reply from 103.235.46.39: bytes=32 time=238ms TTL=45
Reply from 103.235.46.39: bytes=32 time=230ms TTL=45
Reply from 103.235.46.39: bytes=32 time=232ms TTL=45
Reply from 103.235.46.39: bytes=32 time=237ms TTL=45

Ping statistics for 103.235.46.39:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 230ms, Maximum = 238ms, Average = 234ms

C:\Users\User>

I see what you did there, what I didn't "see" is light

[Simon]

seems communicating across the atlantic is faster than by wifi in my house.

[miguelvp]

Let's see, minimum ping of 230ms and Earth's circumference of 40,075 km gives 174,239,130.5 m/s
compared 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 

[Simon]

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.

[Marco]

Group velocity can be faster than light, but really it's just a curious kind of pulse distortion and semantic confusion.

[wraper]

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?...

Electric current is not always electron flow. It can be positively charged particle flow in opposite direction too, like ions in the batteries.

[han]

Light in Optical cable:
G.652D IOR @ 1310 nm. 1.467  68.17% VF


Electrical in cable
VF%   Transmission line
95-99   Open-wire "Ladder" Line
80   Belden 9085 twin-lead
82   RG-8X Belden 9258 coaxial cable (foamed polyethylene dielectric)
66   RG-213 CXP213 coaxial cable (solid polyethylene dielectric)

[madires]

seems communicating across the atlantic is faster than by wifi in my house.

Higher bit rate and larger latency A 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.

[madires]

I'd like to see light go around the earth 10 times or even once  

Sino-US Atlantic optical fiber run across half the north hemisphere, so technically a round trip ping packet will travel around the world, in the form of light (optical fiber).

Please try a sat link 500+ ms

[SteveLy]

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.

[HighVoltage]

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

[FireFlower]

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.

[tggzzz]

Well speed of the light is accepted theory as fastest unit ever and nothing can surpass it.

As said I failed Modern University physics with advanced relation theory because I didn't pay attention but it is not yet law.

No, and maybe that's the reason your first statement is wrong.

Here is a pretty picture of what happens when things do travel faster than light:
http://i.kinja-img.com/gawker-media/image/upload/s--q8KBrnCw--/c_scale,fl_progressive,q_80,w_800/tjbxqdg3awnwvup1ovva.jpg

FFI, google Cerenkov radiation.

[coppice]

Well speed of the light is accepted theory as fastest unit ever and nothing can surpass it.

As said I failed Modern University physics with advanced relation theory because I didn't pay attention but it is not yet law.

No, and maybe that's the reason your first statement is wrong.

Here is a pretty picture of what happens when things do travel faster than light:
http://i.kinja-img.com/gawker-media/image/upload/s--q8KBrnCw--/c_scale,fl_progressive,q_80,w_800/tjbxqdg3awnwvup1ovva.jpg

FFI, google Cerenkov radiation.

When 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.

[tggzzz]

Well speed of the light is accepted theory as fastest unit ever and nothing can surpass it.

As said I failed Modern University physics with advanced relation theory because I didn't pay attention but it is not yet law.

No, and maybe that's the reason your first statement is wrong.

Here is a pretty picture of what happens when things do travel faster than light:
http://i.kinja-img.com/gawker-media/image/upload/s--q8KBrnCw--/c_scale,fl_progressive,q_80,w_800/tjbxqdg3awnwvup1ovva.jpg

FFI, google Cerenkov radiation.

When 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.

False.

Cherenkov radiation is caused by subatomic particles slowing down to the speed of light. Please do at least a little research by googling for the obvious keyword.

[kony]

False.

Cherenkov radiation is caused by subatomic particles slowing down * to the speed of light. Please do at least a little research by googling for the obvious keyword.

Yes, it is slowing down to a 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?

[coppice]

Well speed of the light is accepted theory as fastest unit ever and nothing can surpass it.

As said I failed Modern University physics with advanced relation theory because I didn't pay attention but it is not yet law.

No, and maybe that's the reason your first statement is wrong.

Here is a pretty picture of what happens when things do travel faster than light:
http://i.kinja-img.com/gawker-media/image/upload/s--q8KBrnCw--/c_scale,fl_progressive,q_80,w_800/tjbxqdg3awnwvup1ovva.jpg

FFI, google Cerenkov radiation.

When 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.

False.

Cherenkov radiation is caused by subatomic particles slowing down to the speed of light. Please do at least a little research by googling for the obvious keyword.

Maybe you need to Google for what phase velocity means and exactly which velocity of light the Cherenkov radiation goes faster than before replying.

[tggzzz]

Well speed of the light is accepted theory as fastest unit ever and nothing can surpass it.

As said I failed Modern University physics with advanced relation theory because I didn't pay attention but it is not yet law.

No, and maybe that's the reason your first statement is wrong.

Here is a pretty picture of what happens when things do travel faster than light:
http://i.kinja-img.com/gawker-media/image/upload/s--q8KBrnCw--/c_scale,fl_progressive,q_80,w_800/tjbxqdg3awnwvup1ovva.jpg

FFI, google Cerenkov radiation.

When 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.

False.

Cherenkov radiation is caused by subatomic particles slowing down to the speed of light. Please do at least a little research by googling for the obvious keyword.

Maybe you need to Google for what phase velocity means and exactly which velocity of light the Cherenkov radiation goes faster than before replying.

If 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 light in water.

Your statement would be correct if you had stated "So far nothing physical (matter or energy) is known to travel faster than light IN 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 spot is travelling faster than light! So yes, that is a "cheat" albeit a real one

[coppice]

Well speed of the light is accepted theory as fastest unit ever and nothing can surpass it.

As said I failed Modern University physics with advanced relation theory because I didn't pay attention but it is not yet law.

No, and maybe that's the reason your first statement is wrong.

Here is a pretty picture of what happens when things do travel faster than light:
http://i.kinja-img.com/gawker-media/image/upload/s--q8KBrnCw--/c_scale,fl_progressive,q_80,w_800/tjbxqdg3awnwvup1ovva.jpg

FFI, google Cerenkov radiation.

When 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.

False.

Cherenkov radiation is caused by subatomic particles slowing down to the speed of light. Please do at least a little research by googling for the obvious keyword.

Maybe you need to Google for what phase velocity means and exactly which velocity of light the Cherenkov radiation goes faster than before replying.

If 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 light in water.

Your statement would be correct if you had stated "So far nothing physical (matter or energy) is known to travel faster than light IN 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 spot is travelling faster than light! So yes, that is a "cheat" albeit a real one

Since 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.

[tggzzz]

False.

Cherenkov radiation is caused by subatomic particles slowing down * to the speed of light. Please do at least a little research by googling for the obvious keyword.

Yes, it is slowing down to a 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?

They are slowing down to the speed 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)

[coppice]

False.

Cherenkov radiation is caused by subatomic particles slowing down * to the speed of light. Please do at least a little research by googling for the obvious keyword.

Yes, it is slowing down to a 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?

They are slowing down to the speed 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)

I have worked at Rutherford Appleton Labs, but on the control systems and not the physics. What's your point?

[tggzzz]

False.

Cherenkov radiation is caused by subatomic particles slowing down * to the speed of light. Please do at least a little research by googling for the obvious keyword.

Yes, it is slowing down to a 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?

They are slowing down to the speed 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)

I have worked at Rutherford Appleton Labs, but on the control systems and not the physics. What's your point?

Que? The point is contained in the quoted conversation.

[Brumby]

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!!!"