I've just finished reading a book concerning star gazing.....

askyourgran | 21:53 Tue 20th Sep 2011 | Science

28 Answers

There was a passage in which someone is looking at the stars and promises on the star to do something. The answer to that was that the starlight she sees takes so many thousands of years to reach us that by the time we see it it may not exist any more. I couldn't quite take that in. I'd never thought about that before and it surprised me. Did everyone else know that? Or do I need to catch up. Any more profound things I should know?

Solitaire

Life on Earth Originated from the Sun?

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bibblebub

even the sun is 8 light minutes away

factor-fiction

I recall the furthest star we can see is around 4500 light years we are seeing it as it was 4500 years ago. But 4500 years is a very small period of time (for example the earth is around 4,500,000,000 years old) so I think it's very unlikely that the star will no longer exist.

bookbinder

It is quite well-known that, when we look at distant stars, we see them as they were hundreds, maybe thousands, of years ago, because their light takes such a long time to reach us. bibblebub is quite right about the sun: if it were to be switched off at, say, 1000 hours, we would not notice that until 1008 hours, so, we do not see even the sun as it is now, only as it was 8 minutes ago.

Buenchico

Even the nearest star to us (excluding the Sun, of course) is so far away that the light takes 4.2 years to get here.

Stars detected by the Hubble space telescope are so far away that we're seeing them now (via Hubble) as they were were 13 billion years ago, because that's how long the light has taken to get here. To put that into context, the Earth is only around 4½ billion years old.

Chris

douglas9401

I knew that Gran but I think it doesn't matter to us mere mortals who gaze in awe and wonder. Everything ends up recycled, we really are stardust.

Buenchico

With regard to the size of the universe, here's a rough estimate which I used when teaching:

Start by imagining a glass full of sand and try to imagine how many grains of sand there are in it. (It would take quite some time to count them all). Now try to think about how many grains of sand there would be in a bucket, or a skip, or a lorry container. (Big numbers, right?). Expand that to think about how many grains of sand there are on a beach. Then expand that to think about how many grains of sand there are on every beach in the world, and on the floor of every sea and ocean as well. Now that you've got that incredibly massive number in your mind, square it (i.e multiply it by itself) to make it vastly bigger.

When you've done all of that, the number you'll end up with might (and only might) be getting close to the number of stars in the universe.

bibblebub

The Andromeda Galaxy is usually the most distant object visible to the naked eye, and you are seeing it as it was about 2 1/2 million years ago.

sidkid

I had similar thoughts as gran when I started this thread a few days ago.......
http://www.theanswerb.../Question1057434.html

askyourgran

Question Author

Thank you for that, I am quite interested in the stars and satellites, I never thought about the real meaning of "light years away". It interesting to think about, pretty awesome really.

askyourgran

Question Author

I missed your thread sidkid, it would have partly explained what I wanted to learn. Coincidence.

NiallsMama

If you're interested in this kind of stuff, watch Prof Brian Cox when he's next on TV! Interesting/confusing stuff put in more easy to understand words without being too condescending!

askyourgran

Question Author

I've head of Brian Cox niallsmama I'll look out for him now.

askyourgran

Question Author

Sorry.......I've even heard of Brian Cox^^