• Question: how long would it take a laser beam to reach the andromeda galaxy?

    Asked by lordofdeadspace2 to Mike, Pip, Tianfu, Tim, Tom on 2 Jul 2012.
    • Photo: Tim Stephens

      Tim Stephens answered on 2 Jul 2012:

      Google tells me that Andromeda is about 2.5 million light years away. A light year is the distance that light can travel in 1 year, so it would take about 2.5 million years.
      This means that if you look through a telescope at Andromeda, you’re actually seeing what it looked like 2.5million years ago.

    • Photo: Philippa Bird

      Philippa Bird answered on 2 Jul 2012:

      Wow.

    • Photo: Tom Lister

      Tom Lister answered on 2 Jul 2012:

      It’s the furthest thing you can see with the naked eye, which means it is the furthest back in time you can see without a telescope.

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