[DoctorBeaver (OP)]

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 (OP)]

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 ( newbielink:http://www.hawaii.edu/suremath/jsand.html [nonactive]) 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.

[TheoryOfChaos]

They would also have to count the sand that's at the bottom of the oceans and that's way more than we have on the surface lol so if you ask me all we can do is estimate we will never know just how much sand there is it's impossible to count every single grain of sand from every square inch of the planet now here's something to blow your mind Mars is completely covered in sand lol

[alancalverd]

Most commercial sand (for building, filtration, feedstock for glassmaking....) is quarried from ancient river beds. There's probably as much sand under the surface as above it!

[Ethos_]

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

Any suggestions?

Try collecting them in groups of a trillion and then multiply..........

Just having a little fun with you there my friend.

[evan_au]

in a desert...you'd not only need to know the surface area...but also the depth

There have been radar studies of the Sahara - today the Sahara is quite dry, and radar can penetrate through the dry sand until it hits bedrock, revealing ancient riverbeds. This method should allow you to estimate the volume of sand in dry deserts.

[Bored chemist]

According to this
http://en.wikipedia.org/wiki/Sand
"medium" sand is between 0.25 and 0.5 mm diameter.
Call it 0.3 mm
So the radius is 0.15 mm or 1.5E-4 metres
So the volume is 4E-11 cubic metres.

The sand will essentially all be in the Earth's crust which (so Wiki tells me) is less than 1% of the earth's volume.
The Earth's volume is about 10^12 km ^3
That's about 10^21 cubic metres.
of which about 1% i.e. 10^19 cubic metres is crust.

So, if all the Earth's crust were made from sand grains 0.3 mm in diameter, it would be about 3 E 29 grains of sand.

Of course, the real value might be bigger - if the grains are small, or it might be smaller- since not all the crust is made of sand.