How Space-Time Works When You Look At The Stars


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How Space-Time Works When You Look At The Stars

How Space-Time Works When You Look At The Stars

We’re used to looking at everything around us unfolding in real time. But when we look at the stars, we’re actually looking at the past. We aren’t seeing the stars, or really anything in the universe, as they currently are. We’re seeing things as they were.

The most important point you need to remember is that light travels at a constant speed, which means that it takes time to get anywhere. So, if you look up at the Big Dipper, the stars are anywhere from 79 to 125 light-years away. That means that what you’re seeing is really the light that left the star 79 or more years ago. When you look up and see the moon, that’s what it looked like 1.3 seconds ago. Same idea with the planets.

It works in reverse too. If you looked at Earth through a super powerful telescope from a galaxy 65 million light years away, you would see Earth as it was 65 million years ago, or around the time that the T-rex went extinct.

Thinking about the speed of light isn’t a new concept. There is some evidence that scholars in fourteenth century India were exploring the speed of sunlight. They thought of light as a sort of wind. And though they couldn’t prove anything concretely, when converted into modern units, the ancient calculation came surprisingly close to the actual speed of light

 


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