Naive question about the speed of light

In summary, the conversation discusses the concept of the speed of light being a constant in every reference frame, which originated from the Michelson-Morley experiment. It also touches upon the idea that if one could catch up to a light beam, it would no longer be moving and this would violate Maxwell's equations. However, since this does not happen in reality, it suggests that the speed of light is indeed constant. The conversation also mentions the need for real experiments in physics and how Einstein's thought experiment, while informative, cannot fully replace them.
  • #1
lavinia
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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?
 
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  • #2
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.
 
  • #3
Janus said:
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?
 
  • #4
Einstein's was a "gedanken experiment".
Physics requires real experiments.
 
  • #5
Meir Achuz said:
Einstein's was a "gedanken experiment".
Physics requires real experiments.

thanks
 

What is the speed of light?

The speed of light is a physical constant representing the speed at which electromagnetic radiation travels in a vacuum. It is approximately 299,792,458 meters per second (m/s) or about 670,616,629 miles per hour (mph).

Why is the speed of light important?

The speed of light is important because it is the fastest speed at which energy can travel. It plays a crucial role in many fundamental concepts in physics, such as relativity and quantum mechanics. It also has practical applications in fields such as astronomy, telecommunications, and technology.

Can anything travel faster than the speed of light?

According to Albert Einstein's theory of relativity, no object with mass can travel at or faster than the speed of light. This is known as the "cosmic speed limit." However, it is still a topic of scientific debate and research.

How was the speed of light first measured?

The first successful measurement of the speed of light was conducted by Danish astronomer Ole Rømer in the late 17th century. He observed the moons of Jupiter and noticed that their orbital periods were shorter when Earth was moving towards them, and longer when Earth was moving away. Using this information, he calculated the speed of light to be approximately 220,000 km/s, which is only slightly off from the currently accepted value.

Has the speed of light always been the same?

The speed of light is considered to be a constant in our universe, meaning it does not change over time. However, some theories suggest that the speed of light may have been different in the early stages of the universe's formation. This is still a topic of scientific research and debate.

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