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If light is not affected by time, then why does light cool down over time?

  1. Aug 21, 2011 #1
    As space expands objects dilute out and cool, which includes photons; however photons do not slow down like particles of matter instead, when they cool their vibrational frequencies decrease. This means that they change color, they go from violet to blue then to green, yellow, and red. Then they move onto infrared, then to microwave and lastly to radio waves. Since time is the change from one moment to another, light is affected by time because of the change. However according to Einsteins theory of relativity time completely stops at the speed of light. This obviously makes no sense since time, does appear to affect light.
  2. jcsd
  3. Aug 21, 2011 #2


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    Welcome to PhysicsForums, conner!

    Actually, there is no conflict here. You will find a lot of things in Physics are simplified for general discussion purposes. For example, Newton's gravity is just as accurate as Einstein's when conditions warrant. To address your comment: keep in mind that we live in spacetime; i.e. time is not independent of the space we live in. When you take this into account, everything fits nicely. In other words, the expansion of the universe affects the background microwave radiation too.

    Keep reading, and keep asking questions!
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