Measuring the Speed of Light from Distant Sources: How Do We Know It's Constant?

In summary, Vernon asks if anyone knows how the speed of light from sources outside the galaxy is measured. Prometheus responds by saying that the speed of light is constant regardless of the location of the light source, and this has been tested through experiments. Vernon asks for references to these experiments, to which Prometheus provides a link to a website discussing the measurement of the speed of light from distant objects.
  • #1
Prometheus
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Does anyone know how the speed of light from sources outside the galaxy is measured, such that we are able to recognize that even from these sources the speed of light is constant?
 
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  • #2
Why would you think the speed of light would depend on the location of the light source? As far as we can tell, whether the light source is a flashlight sitting two feet away from you or the sun 93 million miles away, the speed of light is c.
 
  • #3
Gza, you skipped past the question right into the assumption you thought was behind it [I am guilty of that all too often!] Prometheus: That proposition has been tested by examining light sources from different objects at great distances, using mirrors and interferometers, then comparing them to local sources. There is no measurable diffence in 'c'. A number of experiments, some very recent, have been performed to explore your very good question. I will give references if you like.
 
  • #4
Chronos said:
A number of experiments, some very recent, have been performed to explore your very good question. I will give references if you like.
I would appreciate references.
 
  • #5
http://www.student.oulu.fi/~ktikkane/c-const.html of speed of light from very distant objects. The proceedure looks valid to me.

Keep on chuggin !

Vern
 

What is the speed of light?

The speed of light is a fundamental constant of the universe, and it is the speed at which electromagnetic radiation travels in a vacuum. Its value is approximately 299,792,458 meters per second.

How was the speed of light first measured?

The first successful measurement of the speed of light was done by Danish astronomer Ole Rømer in 1676. He observed the eclipses of Jupiter's moons and noticed that the time between eclipses varied depending on the distance between Earth and Jupiter. This variation was due to the time it took for light to travel from Jupiter to Earth.

How is the speed of light measured today?

Today, the most accurate method for measuring the speed of light is through the use of lasers and mirrors. A laser is directed to a rotating mirror, which reflects the beam back and forth between two stationary mirrors. By measuring the time it takes for the beam to travel back and forth, the speed of light can be calculated.

Why is the speed of light considered a universal constant?

According to Einstein's theory of relativity, the speed of light is the maximum speed at which energy or information can travel. This means that no matter the observer's frame of reference, the speed of light will always appear the same. Thus, it is considered a universal constant.

Why is it important to accurately measure the speed of light?

The speed of light is a crucial factor in many areas of physics and technology. It is used in the fields of astronomy and cosmology to understand the vast distances in the universe. It also plays a role in telecommunications, as the speed of light determines the time it takes for signals to travel through fiber optic cables. Accurate measurements of the speed of light also help validate and refine our understanding of the laws of physics.

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