Re: [OT] Stars versus sand grains

From: Terry Given (the_domes_at_xtra.co.nz)
Date: 06/09/04 

Date: Thu, 10 Jun 2004 01:11:39 +1200

"Terry Pinnell" <terrypinDELETE@THESEdial.pipex.com> wrote in message
news:dledc053p5bl5tjol9ik7kfhkra4ft2q11@4ax.com...
> During one morning of a brief holiday last week I walked a few miles
> along a Dutch beach of fine sand. Not for the first time I was musing
> about the familiar comparison that there are more stars in the
> universe than the number of grains of sand on the Earth. I reckon a
> handful of sand must contain several million grains (10^6 grains of
> say 1 mm diameter even in a 1 cm cube). So, even confining my gaze to
> that short stretch of beach, the numbers quickly become very hard to
> handle. Extrapolating to all beaches and deserts across the planet,
> they become effectively incomprehensible to me.
>
> But my curiosity is aroused now. Some googling turned up several
> estimates of the star number, ranging from roughly 10^19 to 10^24.
> Anyone here know of a latest 'best estimate' please? And an estimate
> for the sand number?
>
> --
> Terry, West Sussex, UK
>

something like 10^60 atoms in the entire universe.

If the earth is a sphere of 12,760km diameter, then the surface area of said
sphere is 4*pi*r^2 = 511*10^12 m^2. A gross over-estimate would be 1km deep
sand over the whole planet, ie volume = 0.5*10^18 m^3.

for a grain of sand 1mm diameter, 1cm * 1cm * 1cm = 10^3 (not 10^6) grains
per cm^3. lets assume this, ie 10^9 grains per m^3.

therefore there are around 10^27 grains of sand on earth - and thats being
pretty bloody generous. This number is likely to be an over-estimate, but
not by more than 2-3 orders of magnitude. So its probably a fair comparison
to the total number of stars in the universe.

on an unrelated note, I tried doing some design calcs at a friends house the
other day (I had an idea :) and borrowed a shitty little calculator. no
sqrt() function, and couldnt handle numbers < 1/1000000. no use to me :)

cheers
Terry

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