## vf321 3 years ago Is information (in classical physics) transferred at light speed? Or is it assumed to be instantaneous? What is actually going on in examples such as: 1) An electron in space is surrounded by a capacitor which is connected to a closed circuit. Microsecond by microsecond, what happens? If I have two perfectly rigid boxes, one behind the other, and I push one on the side on a frictionless floor, when will the other box know it's being pushed?

1. telltoamit

i think its instantaneous

2. vf321

Assumed to be so or is?

3. telltoamit

thats what i think lol

4. 009infinity

yes the information is rtansferred at the speed of light

5. vf321

really? So what would happen in the electron problem? The moment an atom of the metal in the switch touches the other side, the electron moves?

6. 009infinity

first tell which type of current is in the circuit ac or dc

7. vf321

you have a battery (dc) of some EP hooked up to a switch and cap in series. an electron is in the space between the cap plates. You switch it on.

8. 009infinity

electron will move towards +ve terminal

9. 009infinity

instantaneous current will start flowing in circuit

10. vf321

assuming it's a perfect switch of course

11. henpen

You need 'stuff' to transfer information. No thing (no 'stuff') can travel faster than light, so no. AT BEST, information (about ANYTHING) travels AT the speed of light, never above.

12. henpen

That was the relativistic answer. Qunatum mechanics muddies the waters considerably (google quantum entanglement).

13. 009infinity

is information ok

14. vf321

yeah @henpen I heard about that

15. henpen

But rereading the question, as long as you aren't doing electromagnetism you can approximate that it does.

16. vf321

eventually we'll have quantum computers with entangled memories - and finally no lag!

17. vf321

OK. so the current has to reach the capacitor, as I understand it.

18. henpen

19. vf321

But what about the boxes example?

20. 009infinity

other box will start accelerating as soon as ist box starts motion

21. henpen

Are all your questions to do with the original information question?

22. henpen

As in, do we assume that information can't travel faster than for that question?

23. vf321

@henpen I don't understand what you're saying. But I watched the video, and it seems to me that all forces can transfer their information at the speed of light (at most), since that information is transferred through the force's field particles (if I am not mistaken).

24. vf321

Then only quantum entanglement is the instantaneous one. And I'm not going to pretend to know how that works.

25. henpen

Basically, it's impossible to have a totally rigid body. If you have light year long scissors (even really strong), if you close then quickly they will bend.

26. vf321

okay then the stress/microscopic compressions in the first box will delay the force's movement across it by however much.

27. vf321

But is my assumption about the light speed of forces true?

28. henpen

Yes and Yes.

29. vf321

max speed of light speed*

30. vf321

OK. Cool. that answers a lot, thanks!