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SETI – why bother?

People, stars and galaxies

There are more a hundred billion or so stars in our Galaxy, which we call the Milky Way.

Look at this letter:    x

Now try to picture a hundred billion letters. You can’t. You’d find that many letters in a million or so books. They would need a bookshelf more than 20 kilometres long.

That’s in just one galaxy. The Hubble Space Telescope is capable of detecting almost a hundred billion galaxies and there are very likely to be many more that are too faint to see but are within the ‘observable Universe’.


  • There are about 6 billion people on Earth and a hundred billion stars in the Milky Way. How many stars are there for each person?
  • Roughly how many galaxies are there in the Universe, for each person?
  • Roughly how many stars are there in the Universe, for each person?
  • Estimate the length of bookshelf that would be needed to hold books with the same number of letters as there are stars in the observable Universe.

Next: Planets


What's your opinion?

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NOT RATED me=) 25-06-09 09:30
who cares?
it's just The EARTH. but i liked the pun..haha..HOT topic! like me then =)
NOT RATED science dorkkk :) 25-06-09 09:34
the earth is my bffff
but i think it is very selfish that we think we're the only life source and i think it is very stereotypical and judgemental that we think that if there are aliens out there that they're going to try and kill us,
that only happens in movies.
If we found another life source, would we try and kill them all? its the same thing.
Think about that.
NOT RATED holly 08-12-11 13:35
it's ded gud- i luv this lol xx xxx xxxx
NOT RATED addy jay 08-12-11 13:35
i love space<3
NOT RATED ellygeeee 08-12-11 13:36
earth for the win!
NOT RATED Maattthheeeww 05-01-12 13:23
Space is just fab i luv it xoxoxo
NOT RATED megg 06-12-12 10:48
love space xoxooxoxoxoxox
NOT RATED emm 06-12-12 10:48
space is great
NOT RATED 21-06-16 10:04
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