Confusion about the speed of light

In summary, the speed of light is a fundamental physical constant that represents the speed at which light travels in a vacuum. It is important in many areas of physics and has practical applications in telecommunications and astronomy. According to our current understanding of physics, nothing can travel faster than the speed of light. However, confusion may arise from the fact that the speed of light can vary depending on the medium. According to Einstein's theory of special relativity, the speed of light is the same for all observers, regardless of their relative motion.
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So everyone knows the speed of light is a universal constant. However in many phenomena involving light it is useful to think that light is 'slowing down' like light travels slower in glass/ water then it does in a vacuum. How can this be if it is a universal constant?
 
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  • #2
Speed of light in vacuum is universal constant. Light passing through media interacts with media and slows down.
 
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There is a bit about this in the FAQ;

https://www.physicsforums.com/showthread.php?t=511177 [Broken]
 
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What is the speed of light?

The speed of light is a fundamental physical constant that represents the speed at which light travels in a vacuum. It is approximately 299,792,458 meters per second or 670,616,629 miles per hour.

Why is the speed of light important?

The speed of light plays a crucial role in many areas of physics, including special relativity, quantum mechanics, and electromagnetism. It also has practical applications in fields such as telecommunications and astronomy.

Can anything travel faster than the speed of light?

According to our current understanding of physics, nothing can travel faster than the speed of light. This is known as the cosmic speed limit and is a fundamental principle of the universe.

What is the confusion about the speed of light?

The confusion about the speed of light often arises from the fact that it is sometimes described as a constant, while in reality, it can vary depending on the medium through which light is traveling. In a vacuum, the speed of light is constant, but it can slow down when passing through a different material.

Is the speed of light the same for all observers?

Yes, according to Einstein's theory of special relativity, the speed of light is the same for all observers, regardless of their relative motion. This is one of the fundamental principles of modern physics.

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