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everephebe's avatar

Sand vs stars (& how is this quantifiable)?

Asked by everephebe (11537 points ) April 23rd, 2011

Basic the question is, “Is Carl Sagan’s claim true about the number of stars in our universe being greater then the sand on all our beaches?”

I’ve heard that all the sand on all the beaches = or ≠ the amount of stars in our universe. So which is it?

I recently asked an astrophysicist (Laurance Doyle actually, it’s sort of a long story) about this, and he said that all the stars in the universe are much greater in number than all of the sand on this planet. And then something about an order of magnitude of 100.

I really like this idea, but how is it truly quantifiable? And what are some of the maths behind these comparisons? Wouldn’t there be a high margin of error?

I believe it was Carl Sagan who first made this statement. For some it’s just the beaches, and others include all the deserts. Some say all dry sand, excluding wet sand apparently.

‘The total number of stars in the Universe is larger than all the grains of sand on all the beaches of the planet Earth.’
Glen Mackie agrees with Carl Sagan.
Carl Sagan says the stars and sand are equally countless.

Then there are folks like this guy.

How quantifiable is this claim?

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10 Answers

NorbertFish4's avatar

Using estimates and apporximations we can work out (within a reasonable accuracy) how much sand there is on the earth. While this is not exact we can use it to roughly compare with stars. Using ultra-sound models of the universe and advanced telescopes to detect them the normal way we can also work out aproximatley how many galaxies there are. I dont know about all the sand on the earth, but we can see that there are far more galaxies out there than grains of sand on our beaches, and in each galaxy there are billions and billions of stars, so i would definitaly agree that there are more stars than grains of sand on the earth.

gmander's avatar

Using some rough estimates:
Number of stars – 10^24
Mass of a grain of sand – 10^-6 kilograms, or 10^6 grains in a kilogram
Mass of the Earth – 5×10^24 kilograms
The bit that I didn’t get from Google was the mass of sand on the Earth, but I think it is safe to assume that, given it will only be on the surface of the planet, it would be a very small fraction of the total Earth mass.
Seems to me that it is likely that there are more stars than grains of sand on the Earth by a few magnitudes. Possibly could be about equal and seems unlikely that there are more grains of sand than stars. Still, you can’t really be sure and it’s not as though the solution of some great universal mystery relies on knowing the answer!

Actually, looking at the quote again, it restricts the statement to sand on beaches, rather than all the sand on the Earth (like deserts), so I think it is much more likely to be true than I previously suggested.

ETpro's avatar

The real unknown here is how many stars there are. We can observe that there are billions of stars in our own Milky Way Galaxy and billions more in the nearby Andromeda Galaxy, and that these two galaxies are just average size. There are billions of additional galaxies that we can observe from here. So we can extrapolate a number that is greater than 1×10^16.

But we don’t know what lies beyond the Universe we can see. What we see is what is close enough for its light to have reached us traveling at 186,000 miles per second for 13.75 billion years. There could well be much more beyond that range that is unobservable to us.

But the bottom line it, just based on what we see, the starrs greatly outnumber the sands of Earth.

flutherother's avatar

Astronomers have estimated that there are ten times more stars in the visible universe than there are grains of sand in all the world’s beaches and deserts. There are at least 70 sextillion stars that is a 7 followed by 22 zeroes in the observable universe.

YARNLADY's avatar

but there’s only one of me

flutherother's avatar

@YARNLADY That is very true :-)
This is weird but after writing the above I noticed your avatar appearing everywhere on Fluther as if other jellies were using it. Am I hallucinating?

filmfann's avatar

I take it as hyperbole. It is a way to express numbers we cannot fathom.

antimatter's avatar

I think it may be possible that there may be more stars than sand should we consider that the universe is so vast and me been a fan of parallel universes is it safe to say that there is more universes than all the sand on our planet and moon.

YARNLADY's avatar

@flutherother It was a game the up-all-night crowd invented in the chat room. I was really flattered they chose my picture.

flutherother's avatar

@YARNLADY I liked your answer ‘but there’s only one of me’ and right after that there seemed to be about twenty of you with more appearing every minute. Very confusing at first but amusing.

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