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CokeDiesel4 t1_j2lg3c5 wrote

Reply to comment by Aseyhe in Is any "movement" visible in the fluctuations of the CMB over time, or does it appear static? by JarasM

>While movement is expected in principle, the cosmic microwave background (CMB) is static over human time scales. > >The light comprising the CMB last scattered at the same time everywhere, when the universe was about 370000 years old. The CMB that we see consists of the light that is just now reaching us. As time goes on, light from more and more distant regions is able to reach us. In this way, the CMB depicts a spherical slice of the 370000-year-old universe (the "last scattering surface") at an ever increasing distance as time goes on.

I just had a stupid thought, since different wavelengths take different amounts of time to reach us does that mean the speed of light varies based on its frequency?

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Aseyhe t1_j2mjzx8 wrote

No, the time light took to reach us only correlates with the amount that the light's frequency is shifted and not with the light's absolute frequency. For example, the CMB is actually a whole spectrum of frequencies. Those frequencies don't take (significantly) different amounts of time to reach us; if they did, the CMB spectrum wouldn't be such a perfect blackbody spectrum.

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CokeDiesel4 t1_j2o8drm wrote

Wow that's incredible! If I understand correctly that means the light being emitted from an object is one long stream and we can access different segments of it by tuning into different frequencies?

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