Grains of sand vs stars. Please post your refutation to my calculations here?

Question

Nick, yes. Like I said. Until the link referenced here, I would have been hard pressed to come up with an estimate for that -- too many factors. So I have not disputed the claim about the beaches. And it is a more colorful, if not sloppy, comparison. I use the volume of desert to make the comparison a little more exact and easier to visualize. As for the number of stars compared to the number of grains of sand *on earth*, I hold my ground and challenge anyone to show otherwise.

Answer 1

You also have to consider just what "visible" means.  Even sticking to the visible spectrum, think of the Hubble Deep Field picture.  It took months of exposure time to get all those galaxies to show up.  So, even if a patch of sky isn't hidden by the Moon, and looks dark, there's still huge amounts of stars to be found--it'll just take awhile. But, yeah, ever since I first heard Sagan say that in Cosmos when I was 8 or so, I thought that's quite a lot of stars since I spent many days at the beach I lived only a mile away from.

Answer 2

Your math looks good. Gave ya a thumbs up. The ones giving you thumbs down are most likely intimidated by your dazzling intellect.  They are usually the kind of people that remain willfully ignorant. Peace out homey.

Answer 3

oh, yeah?

well, buddy, 10x10^22 stars that we guess are in the observable Universe, but how about the ones hidden behind them?

behind the Moon?  bet there's a lot there.

besides, grains of LOOSE sand... the sand underneath is packed into... uh... BRICKS, yeah, BRICKS!

Answer 4

It was Carl Sagan who came up with the comparison in his book and TV series Cosmos.  BUT he compared the number of stars with the number of grains of sand on ALL THE BEACHES of the world.

That is a far cry from including the deserts, but if you go to a large beach and sift sand through your fingers, it is still simply an awesome comparison.  

On the side – desert does not necessarily mean “sand”.  Only about 10% of the Sahara is sandy.  The largest sand desert is the Rub Al Khali (the Empty Quarter) in Saudi Arabia.

Also, forgive me because you went to such efforts, but why not do the calculation in metric.  I know americans have this aversion to it, but since it is based on tens and we count and multiply in tens, it is very much simpler to do this kind of thing.  

cu m = 1 billion cu mm  (1000 x 1000 x 1000)

cu km = 1 billion cu m  (1000 x 1000 x 1000)

So, simple.  

But even so, I would have given you a thumbs up.  

Answer 5

I'll skip the sandy calculation, and just address one detail here.  In your answer, you said that you don't think the universe is infinite.  (I hadn't seen the other question, so I didn't give any thumbs for the answers.)

I read an interview from a couple of years ago with a cosmologist (Joe Silk) who said that it's unknown whether the universe is infinite.  More recently, a Sky and Telescope article about recent results from studies of the cosmic microwave background said that astronomers are now leaning toward an infinite universe.

So the answer is -- who knows? (Aside:  These new Yahoo pop-ups on spelling and punctuation are really annoying.)  If the universe is infinite, the stars win out over the grains of sand, no matter how many sand dunes and ocean bottoms you consider.

It's unclear whether we'll ever know with certainty whether the universe is infinite, so the only reasonable way to approach the stars/sand question is to consider the observable universe.

By the way, the concept of an infinite universe is pretty mind-boggling.  It would seem that anything with a non-zero probability must happen somewhere (in fact, at an infinite number of locations) in an infinite universe.  Even if intelligent life is incredibly rare, there would be an infinite number of planets that have it.  (Of course, the number observable by us would be finite, and might even by zero, not counting whatever intelligence is on this planet.)

Answer 6

Brant, your calculations look good to me.  I didn't bother doing the math on the sand part of it, so I ended up underestimating that end.

Anyways, I think there's an important lesson to be learned here for us all: there's a lot of frickin' sand.

Answer 7

Yes, it might be more in the way you presented the answer.  Those kinds of calculations and the drive to do them can be intimidating.  It seemed like a lot of the people who answered viewed the question less literally; they were almost philosophical about it instead.  It is possible they sensed condescension or superiority in the tone of your answer -- as if they were somehow at fault for not being able to do that type of math.  Sometimes people consider the tone of the answer rather than the answer itself and vote accordingly, which is distressing when you are trying to be honestly helpful.  I wouldn't take it too much to heart -- it's true that not a lot of us can even dream of doing up calculations like yours. :)

Answer 8

Brant,

I didn't give you a thumbs down but consider the piece at the link below by Glen Mackie of Swinburne University.

Answer 9

Work looks good. I gave you a thumbs up.

Note that although all is correct, you had to go with the "visible universe" figure. No choice though. Any other number and you are more into the field of philosophy than science.

bye for now.