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View Full Version : How many grains of sand are there in the Sahara Desert?



Dewey
Jul 14, 2005, 08:48 PM
Does anyone know?

allison
Jul 14, 2005, 09:29 PM
I was wondering about that, too.

Malcolm
Jul 15, 2005, 12:34 AM
Two words; a lot.

Jimmy Junior
Jul 15, 2005, 01:18 AM
Apparently there are more stars in the sky...

Emrysgirl
Jul 15, 2005, 02:15 AM
3256548954120001236545654878794321548795465
Prove me wrong!:D

arach
Jul 15, 2005, 06:25 AM
If you tell me how large and deep the desert is, and how big the grains of sand are (on the average), i can calculate it for you.

Dewey
Jul 15, 2005, 07:53 AM
Good answers - I cannot disagree with any of those!

Thanks

Jimmy Junior
Jul 16, 2005, 12:29 AM
If you tell me how large and deep the desert is, and how big the grains of sand are (on the average), i can calculate it for you.I think it would be more difficult than that sounds, unless the Sahara desert were perfectly cube-shaped.

arach
Jul 16, 2005, 08:56 AM
Of course it would only be an approximate estimation.

Yesterday, I have made myself a small cube of exactly 1cm³ volumina, have filled it with medium-corned sand and tried to count it. That was pretty hard to do, because there were (approximately!) over 700 grains in that little volumina. Anyway... I don't find any information about how large the areas are which are covered with sand (most of Sahara is out of rock and stone), and how deep the layer of sand (approximately) is.

Pretty sad, it would have been very interesting to compare with other things, like stars in the galaxy, atoms or other things. :(

arach
Jul 16, 2005, 10:26 AM
When we presume that there is sand everywhere in the sahara desert, but the sand layer is only 0,5m thick, we can calculate it easily. (I know that there must be several areas in the desert where the sand layer that is several metres deep, especially in regiones with those huge dunes, but because the sahara's main part is made of stone and rock, I just estimated that percentile... 0,5 metres thick. That must be far enough. If somebody thinks that this is incorrect or not realistic, I can calculate it with other numbers again.)

So here is what I calculated:

In 1 cm³ of my tiny little box were about 700 grains of sand.
1 cm³ is 1x10^-9 km³ - we need that later.

The Sahara desert is around 9 mio km² large. If we assume that there is a continuous sand layer of 0,5m depth (that are 5x10^-4 km), we get a sand layer volumina of
5x10^-4 km x 9000000 km² = 4500 km³ Sand layer.

How many of my 1cm³ boxes fit in there?
4500 : 1x10^-9 = 4,5x10^12 cm³ Sand layer.

1cm³ has about 700 grains, so it's 4,5x10^12 x 700 = 3,15x10^15 or, in other words:
3 150 000 000 000 000 grains!
(for US: 3 quadrillion grains, for europ. countries: 3 thousand billion grains)

Comparison: A average galaxy contains about 10^11 =
100 000 000 000 stars.

:D

Dewey
Jul 16, 2005, 11:04 AM
I'm hugely impressed!

yardgames
Jul 24, 2005, 11:50 AM
@arach, I lost you, but ok. I'll trust you. Take some rep.