Register to reply

Naive question about the speed of light

by lavinia
Tags: light, naive, speed
Share this thread:
lavinia
#1
Jan8-11, 08:46 AM
Sci Advisor
P: 1,722
I thought that the idea that the speed of light is a constant in every reference frame came from the Michelson-Morely experiment. But a friend of mine was saying that Einstein supposed that if one could catch up to a light beam then it would no longer be moving and would then not be an electromagnetic wave. This would violate Maxwell's equations. Wouldn't this thought experiment suggest that the speed of light is constant?
Phys.Org News Partner Physics news on Phys.org
New complex oxides could advance memory devices
Nature's designs inspire research into new light-based technologies
UCI team is first to capture motion of single molecule in real time
Janus
#2
Jan8-11, 11:48 AM
Emeritus
Sci Advisor
PF Gold
Janus's Avatar
P: 2,361
The point is that according to Maxwell's equations, if you could move at a different speed than c relative to a light beam(as measured by you), then for you, the electromagnetic wave that the light consists of would vanish.

The practical result of this would be that unless you were perfectly at rest with respect to a light source, you wouldn't be able to see it, car radios wouldn't pick up any stations while driving down the road, etc.

Since none of this happens, we conclude that electromagnetic waves are measured as moving at c in every reference frame.
lavinia
#3
Jan8-11, 11:50 AM
Sci Advisor
P: 1,722
Quote Quote by Janus View Post
The point is that according to Maxwell's equations, if you could move at a different speed than c relative to a light beam(as measured by you), then for you, the electromagnetic wave that the light consists of would vanish.

The practical result of this would be that unless you were perfectly at rest with respect to a light source, you wouldn't be able to see it, car radios wouldn't pick up any stations while driving down the road, etc.

Since none of this happens, we conclude that electromagnetic waves are measured as moving at c in every reference frame.
Ok so why do you need the Michelson Morely experiment?

Meir Achuz
#4
Jan8-11, 02:07 PM
Sci Advisor
HW Helper
PF Gold
P: 2,026
Naive question about the speed of light

Einstein's was a "gedanken experiment".
Physics requires real experiments.
lavinia
#5
Jan8-11, 02:50 PM
Sci Advisor
P: 1,722
Quote Quote by Meir Achuz View Post
Einstein's was a "gedanken experiment".
Physics requires real experiments.
thanks


Register to reply

Related Discussions
Naive question Special & General Relativity 2
Idea for light speed or possibly faster than light speed travel? Quantum Physics 1
Flash Light at the Speed of Light Question Special & General Relativity 4
Naive Question about GUT High Energy, Nuclear, Particle Physics 1
Naive Question General Physics 11