• Question: How do scientists know about things in space that happened billions of years ago before earth was even formed?

    Asked by bethenna to Claire on 24 Jun 2013.
    • Photo: Claire Lee

      Claire Lee answered on 24 Jun 2013:

      Good question!

      Space is huge. Crazy, mind-bogglingly huge. In fact, it is so huge that it takes a long LONG time for even light to go across it.

      Light travels fast – 300 000 km per second! But even at that speed, it takes light 8 minutes to get from the sun to us.

      So if you look at the sun, you are not seeing what the sun looks like now. You are seeing what the sun looked like 8 minutes ago!

      The further away you go the farther back in time you look. The nearest star to us is 4.2 light years away – the light you’re seeing left that star 4.2 years ago! and so on and so on until, if you have a telescope sensitive enough you can see back billions of years. Hubble managed to catch a photo of a galaxy, whose light left it 13 billion years ago. That galaxy is probably long gone, perhaps all the stars are burnt out, or it has collided with another galaxy since then.

      So that’s how we can tell what happened long ago – because the further away we look, the farther back in time we are seeing 🙂

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