Stars & sand

gez · #1 (**permalink**) 05-10-2007, 08:06 PM

Can any one give me a easy way to explain to a work mate why/how there are many more stars than grains of sand. As he just can not get his head around the logic of it all.
thanks gez

Paul mabbott · #2 (**permalink**) 05-10-2007, 08:29 PM

Quote:

Originally Posted by gez

Can any one give me a easy way to explain to a work mate why/how there are many more stars than grains of sand. As he just can not get his head around the logic of it all.
thanks gez

I don't think it's a matter of logic, just of facts.
.... and I suspect the facts are wrong! The usual saying is that there are more stars (and therefore solar systems) than there are grains of sand on a beach .... it's a figure of speech and it's clearly nonsense. Just means that there are a lot more suns than most of us can conceive of - as, indeed, we have difficulty in conceiving of any very large number! At least, I do ....

paulchandler6 · #3 (**permalink**) 05-10-2007, 09:08 PM

The thing is we just dont know for sure. Who knows how many grains of sand there are and how many stars there out there. Maybe some theoretical mathematician has worked it out. Doubt if most of us could get our heads around it anyway.
Maybe one day.

Paul

carlos_dfc · #4 (**permalink**) 05-10-2007, 11:52 PM

yes - it can be worked out.....

I've seen the workings-out for the amount of grains of sand, on an average beach.
By working out the area, multiplied by the average depth of sand - they came up with the volume of sand - then working on an average size for the sand grains (the size they used was the defining line between 'fine' and 'medium' grains)
Figure they came up with was about One Quadrillion (A million, million - 1,000,000,000,000 )

Now for the stars:-
Our galaxy is an average galaxy (the nearby Andromeda galaxy is larger, and the next nearest spiral, M33, is a bit smaller)
In our galaxy, ther are an estimated 100 billion stars (100,000,000,000 )
As you can see, that is already about 10% of the amount of sand grains on a beach
Latest best estimate for the amount of galaxies in the Universe is around 125 billion (125,000,000,000)
Multiply these together, and you get a stupidly high number (12,500,000,000,000,000,000,000) or 1.25 x 10 to the power of 22

This equates to roughly the amount of grains of sand on 12.5 billion beaches
So - as you can see - never mind the amount of sand grains on a beach - there are more stars in the Universe than there are grains of sand on our planet

paulchandler6 · #5 (**permalink**) 05-10-2007, 11:56 PM

I'm impressed. Have you been crew on the Enterprise?

Lets hope Gez can explain that to his work mate.

Paul

carlos_dfc · #6 (**permalink**) 06-10-2007, 01:33 AM

Quote:

Originally Posted by paulchandler6

Have you been crew on the Enterprise?

LOL - I Wish....

But I've been 'into' astronomy for a number of years now - even run my own astronomy forum, and the 'sand-grains' question does come up from newbies pretty regularly, so I made a point of checking out the 'answer' quite a while ago.