The telescope, in enabling us to look far out into space, also allows us to look back in time. Light travels at about 186,000 miles per second. When we look up into the daylight sky, we are not seeing the sun as it currently is but as it was about eight minutes ago, since it takes that long for the light radiating from this familiar star to travel 93 million miles to Earth. Similarly, when the Giant Magellan Telescope (GMT) receives light waves from the depths of the universe, those waves will have originated from points as far as 76 sextillion (76,000,000,000,000,000,000,000) miles away. It will have taken those waves some 13 billion years to arrive on earth, meaning they left their source about a million years after the big bang, and roughly nine to ten billion years before Earth even formed.
Richard Kurin, The Smithsonian's History of America in 101 Objects
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