Outer space is a deep, dark place, right? Well, yes and no. Imagine a carrot-colored sky. There was a time when the light emitted by the universe was orange. But as space expanded, the wavelengths stretched and the light emitted changed. Over a few million years, the orange spectrum of light that the universe once emitted changed from red to infrared, which is not perceivable by the human eye and to us just looks dark.
Space Wasn't Always Black
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Key Facts In This Video
The entire universe used to be a shade of orange. 00:00
CMB stands for cosmic microwave background, which is the static you will receive when you point a dish at any point in the sky. 00:29
As space expands, the wavelengths of free streaming light stretched due to cosmological redshift, which is why the apparent color of the universe changed. 04:28