• Question: if you put a mirrora really long way away in the universe will you see dinosurs?

    Asked by 10thosamb to Daniela, Hannah, Ian, Jono, Mark on 25 Jun 2013.
    • Photo: Hannah Brotherton

      Hannah Brotherton answered on 25 Jun 2013:

      Hi 10thosamb….
      This is a GREAT question…

      Why???? and why am I getting excited about it..because it already happens. You are talking about seeing the past if we put a mirror far away. Well we see this already, in the stars!!

      Every star in the sky, is either gone or dying, but we see them shining brightly as young stars. Even though light travels fast (186,282 miles per second pretty fast :P), in space it has to travel so far, that we are probably seeing the stars when they were shining about 3000000000millions years ago (not accurate, but a really long time ago). So these stars are gone, but we see them as still here, and this is because light from the stars is slow and by the time it has reached us, we are seeing the past.
      So its light shining a torch into space…….a person far far away, probably wouldn’t see the light from the torch until millions of years later. they are seeing something I did in the past

      So….if we put a mirror or a really really really strong telescope on the other side of space (but we did this when dinosaurs were alive) then by the time the time is reflected back to earth, we would be able to see the earth millions of years ago including seeing dinosaurs.

      So think of this…if there is an alien planet light years away….far far away and they are looking at our planet, because of how slow light is, they will see our earth when it had dinosaurs on it!

      so the further away you are, the slower light travels….the further back in time you can see

      I love this question 😀

    • Photo: Ian Wilson

      Ian Wilson answered on 25 Jun 2013:

      Hi 10thosamb,

      Hmm…if we put the mirror millions of light years away then it’s possible that we could see a prehistoric Earth. We can even work out how far away the mirror would need to be!

      To explain this, think about our Sun. It’s 149,600,000 km away from Earth. Light travels from the Sun at 299,792 km every second (which is the fastest anything can move in the universe!). That means that the light hitting Earth right now was actually produced 8 and a half minutes ago! So when scientists look at the sun they are actually seeing what it looked like in the past.

      The same goes for light reflected by planets. Any distant planet that we see, we are only seeing it in the past. Same with stars – some stars that we see shining might already be dead! But let’s think about Earth and how far away our mirror would need to be to see that far into the past:

      Dinosaurs went extinct about 65 million years ago. So if we divide 65 million years (or 31,556,900,000,000 seconds) by the distance light can cover every second then we can work out how many kilometres away the mirror would need to be to see it happen:

      2,051,198,500,000,000 kilometres away! I think that’s 2 quadrillion kilometres away!

      Unfortunately, the light would need to bounce back to Earth for us to see it so would take another 65 million years for us to see the mirror image….so it’s quite a long term experiment!

      Cheers,

      Ian

    • Photo: Mark Hodson

      Mark Hodson answered on 25 Jun 2013:

      Hi 10thosamb,

      as you can see from Ian and Hannah, the answer is yes, but it’s a tricky experiment to do. Better to watch Jurassic Park!

      cheers

      m

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