[math-fun] a question of sand
Hello , I read recently that the calculated the approx. amount of stars in the known universe to be 7x10^22, which is according to source, greater than the number of grains of sand in all the deserts and beaches on earth. Well, this is quite big, but as I was explaining this to some people around me, is there a known value of the number of grains of sand in let's say 1 cubic meter of sand ? I know some are very small and others are bigger : does someone has an approximate value ? I tried to find without success and also I have no idea on how to calculate this simple value. Thanks for any answer(!). source : a certain australian study : http://en.wikipedia.org/wiki/Observable_universe best regards and have a nice evening. Simon Plouffe
From: Simon Plouffe <simon.plouffe@gmail.com> To: math-fun <math-fun@mailman.xmission.com> Sent: Mon, November 1, 2010 10:00:46 AM Subject: [math-fun] a question of sand Hello , I read recently that the calculated the approx. amount of stars in the known universe to be 7x10^22, which is according to source, greater than the number of grains of sand in all the deserts and beaches on earth. Well, this is quite big, but as I was explaining this to some people around me, is there a known value of the number of grains of sand in let's say 1 cubic meter of sand ? I know some are very small and others are bigger : does someone has an approximate value ? I tried to find without success and also I have no idea on how to calculate this simple value. Thanks for any answer(!). source : a certain australian study : http://en.wikipedia.org/wiki/Observable_universe best regards and have a nice evening. Simon Plouffe _______________________________________________ How big is a grain of sand? Perhaps 0.1 mm = 10^-4 m. So a cubic meter should contain about 10^12 grains. -- Gene
Some other sources: http://astronomy.swin.edu.au/~gmackie/billions.html http://everything2.com/title/There+are+more+stars+in+the+universe+than+grain s+of+sand+on+earth http://answers.google.com/answers/threadview/id/539329.html -----Message d'origine----- De : math-fun-bounces@mailman.xmission.com [mailto:math-fun-bounces@mailman.xmission.com] De la part de Simon Plouffe Envoyé : lundi 1 novembre 2010 18:01 À : math-fun Objet : [math-fun] a question of sand Hello , I read recently that the calculated the approx. amount of stars in the known universe to be 7x10^22, which is according to source, greater than the number of grains of sand in all the deserts and beaches on earth. Well, this is quite big, but as I was explaining this to some people around me, is there a known value of the number of grains of sand in let's say 1 cubic meter of sand ? I know some are very small and others are bigger : does someone has an approximate value ? I tried to find without success and also I have no idea on how to calculate this simple value. Thanks for any answer(!). source : a certain australian study : http://en.wikipedia.org/wiki/Observable_universe best regards and have a nice evening. Simon Plouffe _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
I calculated this exact same thing using kitchen salt instead of sand. I actually measured out a small volume of salt and counted 1000 grains. The density came out to be about 350,000 grains per cubic inch or, very naively, equivalent to little cubes 1/70 inch on a side filling space. Sand varies much more than ordinary kitchen salt--for example the beach sand here in Santa Monica is somewhat finer. Anyway 7*10^22 (also the number of stars I used) would occupy about 800 cubic miles, enough to cover Los Angeles County to a depth of 1000 feet, or almost enough to fill the Grand Canyon. Beaches are interesting because the total length, average width, and average depth are all hard to estimate. Steve Gray On 11/1/2010 10:00 AM, Simon Plouffe wrote:
Hello ,
I read recently that the calculated the approx. amount of stars in the known universe to be 7x10^22, which is according to source, greater than the number of grains of sand in all the deserts and beaches on earth.
Well, this is quite big, but as I was explaining this to some people around me,
is there a known value of the number of grains of sand in let's say 1 cubic meter of sand ? I know some are very small and others are bigger : does someone has an approximate value ? I tried to find without success and also I have no idea on how to calculate this simple value.
Thanks for any answer(!).
source : a certain australian study : http://en.wikipedia.org/wiki/Observable_universe
best regards and have a nice evening.
Simon Plouffe
_______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
I think it's a close call. Take the average diameter of a grain of sand at 1mm (http://hypertextbook.com/facts/2000/IlanaPrice.shtml) and assume the earth is covered in a layer of sand one meter deep. It's not all that different that the star estimate. Maybe there's not that much sand, but maybe the average diameter is smaller. While is it conceivable that we could count the grains of sand, I don't see how to count the stars, so a one-to-one mapping attempt is infeasible. Hilarie
To: math-fun <math-fun@mailman.xmission.com> From: Simon Plouffe <simon.plouffe@gmail.com> Subject: [math-fun] a question of sand Date: Mon, 01 Nov 2010 18:00:46 +0100
Hello ,
I read recently that the calculated the approx. amount of stars in the known universe to be 7x10^22, which is according to source, greater than the number of grains of sand in all the deserts and beaches on earth.
Well, this is quite big, but as I was explaining this to some people around me,
is there a known value of the number of grains of sand in let's say 1 cubic meter of sand ? I know some are very small and others are bigger : does someone has an approximate value ? I tried to find without success and also I have no idea on how to calculate this simple value.
Thanks for any answer(!).
source : a certain australian study : http://en.wikipedia.org/wiki/Observable_universe
best regards and have a nice evening.
Simon Plouffe
Simon, Isn't there a power law distribution of some kind with larger and smaller grains intermixed? Compare the definitions of "sand", "silt" and "clay", or look up "sediment grain sizes". Example: http://geology.about.com/od/sediment_soil/a/sedimentsizes.htm On Mon, Nov 1, 2010 at 13:00, Simon Plouffe <simon.plouffe@gmail.com> wrote:
Hello ,
I read recently that the calculated the approx. amount of stars in the known universe to be 7x10^22, which is according to source, greater than the number of grains of sand in all the deserts and beaches on earth.
Well, this is quite big, but as I was explaining this to some people around me,
is there a known value of the number of grains of sand in let's say 1 cubic meter of sand ? I know some are very small and others are bigger : does someone has an approximate value ? I tried to find without success and also I have no idea on how to calculate this simple value.
Thanks for any answer(!).
source : a certain australian study : http://en.wikipedia.org/wiki/Observable_universe
best regards and have a nice evening.
Simon Plouffe
-- Robert Munafo -- mrob.com Follow me at: mrob27.wordpress.com - twitter.com/mrob_27 - youtube.com/user/mrob143 - rilybot.blogspot.com
At last, a use for my copy of The Physics of Blown Sand and Desert Dunes (R.A. Bagnold, Dover reprint) On pg 1 he introduces a partially overlapping continuum of particles (big to small) Pebbles Sand Dust Fog Particles Atmospheric Dust Thin Smoke Haze Pebbles are for him 1mm or greater in diameter. "Sand" occupies the region from 1mm down to 1/50 of a millimeter. You hit the "Dust" boundary there.
From pg 6
"When samples of natural sand are analyzed by sifting, it is found that, in general, grains of one diameter predominate, and that the weights of sand of diameters both larger and smaller fall off rapidly as the diameter departs from the "peak" value. And in the finest wind-blown sands the predominant diameter is never less than .08mm. Usual values, depending on the locality, lie between 0.3 and 0.15mm." On Mon, Nov 1, 2010 at 1:28 PM, Robert Munafo <mrob27@gmail.com> wrote:
Simon,
Isn't there a power law distribution of some kind with larger and smaller grains intermixed?
Compare the definitions of "sand", "silt" and "clay", or look up "sediment grain sizes". Example: http://geology.about.com/od/sediment_soil/a/sedimentsizes.htm
On Mon, Nov 1, 2010 at 13:00, Simon Plouffe <simon.plouffe@gmail.com> wrote:
Hello ,
I read recently that the calculated the approx. amount of stars in the known universe to be 7x10^22, which is according to source, greater than the number of grains of sand in all the deserts and beaches on earth.
Well, this is quite big, but as I was explaining this to some people around me,
is there a known value of the number of grains of sand in let's say 1 cubic meter of sand ? I know some are very small and others are bigger : does someone has an approximate value ? I tried to find without success and also I have no idea on how to calculate this simple value.
Thanks for any answer(!).
source : a certain australian study : http://en.wikipedia.org/wiki/Observable_universe
best regards and have a nice evening.
Simon Plouffe
-- Robert Munafo -- mrob.com Follow me at: mrob27.wordpress.com - twitter.com/mrob_27 - youtube.com/user/mrob143 - rilybot.blogspot.com
math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
-- Thane Plambeck tplambeck@gmail.com http://thaneplambeck.typepad.com/
participants (7)
-
Christian Boyer -
Eugene Salamin -
Hilarie Orman -
Robert Munafo -
Simon Plouffe -
Stephen B. Gray -
Thane Plambeck