Why does the speed of light have to be constant to all observers?

In summary, the conversation discusses the concept of Special Relativity and the principle that the speed of light must be constant for all observers. The question is raised about why this is necessary and whether the universe would still be logically consistent if there was no cosmic speed limit. The conversation also mentions a related FAQ and discusses the possibility of removing the thread.
  • #1
Bobcent
31
0
Hello!

I think I understand the principle of Special Relativity, that because the speed of light has to be constant to all observers, the only solution to the problem is that time slows down or speeds up for different observers who are traveling at different speeds.

But my question is: Why does the speed of light have to be constant to all observers?

If the speed of light wouldn't be constant to all observers, there wouldn't be a cosmic speed limit, right? Because then, if I travel at a certain speed and emit light in front of me, the speed of that light would be my speed + the speed of light.

So if there wouldn't be a cosmic speed limit, would the universe still be logically consistent? If not, in what way wouldn't it be? Would it somehow violate the law of conservation of energy?

Or would the universe actually be logically consistent even if there wouldn't be a cosmic speed limit, just that it turns out that that's not the way our universe works?
 
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  • #2
We have a FAQ about this: https://www.physicsforums.com/showthread.php?t=534862
 
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  • #3
Oh, I didn't notice, thanks! Will remove this thread.
 
  • #4
Hmm, can't find where to do this. Is it possible?
 
  • #5
Bobcent said:
Hmm, can't find where to do this. Is it possible?

Only by hitting "report" and asking a moderator to remove the thread, but thread removal is rarely done.
 

FAQ: Why does the speed of light have to be constant to all observers?

Why is the speed of light considered a universal constant?

The speed of light is considered a universal constant because it has been measured to be the same for all observers, regardless of their relative motion or the direction they are measuring it from. This has been consistently observed and verified through numerous experiments and is a fundamental principle of the theory of relativity.

How is the constancy of the speed of light related to the theory of relativity?

The constancy of the speed of light is a foundational principle of the theory of relativity. It is a key component of Einstein's special theory of relativity, which states that the laws of physics should be the same for all observers in uniform motion. The constancy of the speed of light allows for the existence of a universal frame of reference, which is necessary for the consistency of the theory.

What evidence supports the idea of the constant speed of light?

There is a significant amount of evidence that supports the idea of the constant speed of light. One of the most compelling pieces of evidence is the Michelson-Morley experiment, which showed that the speed of light is the same in all directions. Additionally, the predictions and calculations based on the theory of relativity have been consistently confirmed by experiments and observations.

How does the constant speed of light affect our understanding of space and time?

The constant speed of light has significant implications for our understanding of space and time. It is a key factor in the concept of time dilation, which explains how time passes differently for observers in different frames of reference. It also plays a crucial role in the idea of length contraction, which describes how objects appear to change in length when viewed from different frames of reference.

Is it possible for the speed of light to change?

According to our current understanding, the speed of light is a fundamental constant and cannot be changed. This is supported by the theory of relativity and the extensive evidence that has been gathered through experiments and observations. While it is theoretically possible for the speed of light to change, it would require a significant rethinking of our understanding of the laws of physics and the universe.

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