A massive radio telescope on the moon could unravel the mysteries of the “Cosmic Dark Ages” — if NASA can build it before the lunar surface gets too crowded.
Light is the fastest thing in the universe, moving at a blistering 186,000 miles per second in the vacuum of space, but because space is massive, it can still take a long time for light from distant objects to reach Earth.
That means when you look at something far away in space, what you’re actually seeing is what it looked like deep in the past, when the light first began its journey. Light from the North Star, for example, takes 320 years to reach Earth, so when you look at that star, you’re seeing what it looked like 320 years ago.
Visible light is just one type, and NASA studies light from all along the electromagnetic spectrum to glean as much information about the universe as possible. The Hubble Space Telescope, for example, observes visible light, while the Fermi Gamma-ray Space Telescope detects gamma rays.
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