How do does radio signal keep on travelling in space? Shouldn’t it just fade away.
In: Engineering
Astronomer here, there is a signal from the early part of the universe (13 billion years ago) called the cosmic microwave background.
If you were around even a billion years after the signal/imprint was formed, you would see it as more likely the cosmic x-ray or cosmic gamma-ray background. But due to the expansion and accelerated expansion of the universe, the light has redshifted so much it’s wavelength is now in the microwave bands (which is effectively a radio signal).
Light fades via redshifting, aka the wavelength increasing in size as the universe itself increases in size. This is why the most distant stars look redder to us than the closest stars. And stars/any light moving towards us look bluer.
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