I am trying to think of a way of explaining how insignificant the earth is in the whole vastness of space but I cannot think of a way of getting across just what a tiny part we are.
Unfortunately, the answer by jake-the-peg is rubbish.
"There are as many stars in the galaxy as grains of sand on a beach."
That's rubbish. There are c.100,000 million stars in the galaxy. Even if you allow for very large granular grains of sand (1 cubic millimetre per grain), 100,000,000,000 grains of sand would only be enough to fill up a football pitch to a depth of half an inch. An average sandy beach is many many times larger than a football pitch.
"If you started to count the stars just in our galaxy one a second it would take you 16 thousand years"
I agree with Bernardo. Most people when asked to imagine a beach imagine one much larger than 22 x 22 x 1m. This is probably due to the large beaches shown in holiday brochures. Using a beach as an analogy for imagining how many stars are in our galaxy would mislead people that the galaxy is much bigger than it really is. A better analogy would be that there is as many stars in our galaxy as there are grains of sand is in a small McDonalds restaurant that has been filled to an average humans waist height with sand.
eh? can't believe we're debating this beach thing. it's hardly as if the number of grains of sand on a beach is any easier to relate to than the number of stars in our galaxy or the universe.
"there's 100 billion stars in our galaxy"
"wow...i just can't picture or relate to that sort of number"
"it's about the same as the number of grains of sand on a beach"
"oh, right, that helps, i once counted all the grains of sand on a beach. took me ages"
The point, RJA, is that not too many of us have wandered about the universe ticking off stars etc as we pass them! However, we've all been on a beach and so can relate, albeit vaguely, to the vastness of the number of sand-grains there just by watching them dribbling through our fingers. Any huge number in any circumstances is "beyond comprehension" for most of us, but the sand-grain concept is one we can at least relate to on a personal level.
If we take the number of grains of sand on a beach to mean those resting on the surface (those seen without digging if I dare be so bold) in comparison to anyone's estimate of the number of stars in our galaxy . . . that's got to be make for one nasty beach!
Now multiply that by the number of galaxies in the universe
and you could cover the Earth in stars.