Is the speed of light constant with time?

In summary, Professor Brian Cox explains that the universe is constantly expanding, stretching the space we live in from the early universe. This expansion occurs at a rate of 74 km per second / megaparsec. The question of whether the speed of light through vacuum is constant with respect to time is often raised due to the observed redshift or increase in wavelength. However, even if the speed of light is not constant, it is still considered the speed of "gravitational waves".
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vijayst
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In, BBC - Wonders of Universe, Professor Brian Cox explains that universe is stretching and the space that we live in is stretched from the early universe.

If space is stretched as a result of Big Bang, and space is stretched at the speed of 74 km per second / megaparsec. is the speed of light through vacuum constant with respect to time?

[Please close this thread. Due to observed red shift or increase in wavelength, speed of light should be constant, as frequency decreases to counter the increase in space. Even if speed of light is not constant in time, c is the speed of "gravitational waves"]
 
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Space does NOT "stretch". That is an analogy used in pop-science TV shows and has nothing to do with reality. Google "metric expansion" and/or see the link in my signature.
 

What is the speed of light?

The speed of light, denoted by the symbol c, is the speed at which light travels in a vacuum. It is approximately 299,792,458 meters per second.

Is the speed of light constant?

Yes, according to Einstein's theory of relativity, the speed of light is a fundamental constant that does not change with time or space.

Why is the speed of light considered a constant?

The speed of light is considered a constant because it has been measured and observed to be the same in all frames of reference, regardless of the observer's motion or the direction of the light source.

Has the speed of light ever been proven to change with time?

No, there is currently no scientific evidence or observation that suggests the speed of light changes with time.

What implications does a constant speed of light have on our understanding of the universe?

The constant speed of light is a crucial factor in our understanding of the universe and is the basis for many theories and equations in modern physics. It helps explain the behavior of light and other electromagnetic radiation, as well as the concept of time dilation and the relationship between space and time.

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