[DoctorBeaver]

I've heard the comparison many times that there are more [insert as appropriate] than grains of sand on the Earth.

That got me wondering. How do they know how many grains of sand there are?

Supplemental question - are all grains of sand the same size?

[Alandriel]

Apparantly this calculation tells you how they made up
that there are (aproximately) 700,500,000,000,000,000,000 grains of sand on earth
(or seven quintillion five quadrillion for the likes of me)



What fascinates me though is that there are more atoms that this in your body, an estimated
7,000,000,000,000,000,000,000,000,000

 

edited to fix link...twice 

[DoctorBeaver]

That says they used the length of all beaches in the world. So what about deserts (is there more sand in deserts than on beaches?) and children's sandpits?

[Alandriel]

I don't think they've taken into account any deserts, heck, half the world's
deserts have not even been properly explored let alone studied.
How would you calculate the volume of sand contained in a desert?
You'd not only need to know the surface area - and that changes with the seasons - but also the depth


a lot of digging, that .........................


......... I'd volunteer 

wouldn't mind at all. I LOVE deserts 

[TECHFACTOR]

 As many as there are stars in the galaxy.I heard that somewhere.TECHFACTOR:OUT

[Andrew K Fletcher]

Give or take a grain?

[Mr. Scientist]

Apparantly this calculation tells you how they made up
that there are (aproximately) 700,500,000,000,000,000,000 grains of sand on earth
(or seven quintillion five quadrillion for the likes of me)



What fascinates me though is that there are more atoms that this in your body, an estimated
7,000,000,000,000,000,000,000,000,000

 

edited to fix link...twice 

That's because our bodies on the scale of density, is much more than a body made of sand; a great deal more.

[yor_on]

I've started enumerating those corns of sand.
But I keep loosing count.

Any suggestions?

[Chemistry4me]

Can't somebody invent something that turns the sand back into rocks, that'll make counting (very) slightly easier...

[cercops]

Sand can be various different sizes. Sand is generally the result of weathering of rock, which breaks the large particle (bedrock or boulder) into smaller particles: cobbles, gravels, sand, silt, or clay.  According to the Unified Soil Classification System, sand would be mineral aggregations between 4.75 mm and 75 micrometers.

This brings up a relevant point regarding the number of grains of sand question:  You not only have to count the sand in deserts and beaches and sandboxes, but the sand in the soil across the whole surface of the earth.  Most soil has at least some sand in it; many soil types, such as alluvial soils, have very high percentages of sand.  The 7.5 x 10^19 estimate done by mathematicians at the University of Hawaii (http://www.hawaii.edu/suremath/jsand.html) only counts beaches; I have also seen a 10^20 to 10^24 estimate, but have not seen the justification for that, so I'm not sure if it only counts the sand in beaches and deserts.