Stars versus sand grains

During 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 0.1 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.
What is the latest 'best estimate' please?

And, while it's well OT for this group, does anyone have an estimate
for the sand number? Presumably there must be one, for the assertion
to have been made.

--
Terry, West Sussex, UK

After further googling I've still not found anything that could be
called a 'consensus' for the star number. But say it's 10^22. FWIW,
that's about ten times more than one I've seen mentioned by several
sources, of '100 billion galaxies, each averaging 10 billion stars'.
(Of course, they may each have been quoting the same source...) As
you'll have seen from my follow-up, 1mm was a typo: should have been
0.1mm. And even that's probably far too large. Examined a few grains
under a microscope, and most were more like 0.01 mm. So my current
best guess would be say 0.02 mm. IOW, you could get 50 typical grains
of sand between the 1mm divisions on a ruler.

Using 5*10^14 m^2 as a crude approximation for Earth's surface area
would imply that a sand depth as little as 1 m covering the Earth
would then contain about 6*10^28. That's a million times *more* than
the star number. For the original assertion to be true would imply a
depth of only 0.00016 mm - far less than one grain's diameter!

This is all very crude, but reinforces my suspicion that for all its
familiarity the 'sand/stars' assertion might possibly be exaggerated.
Or, of course, the number of stars is many orders of magnitude larger
than any estimate I've seen so far. Or sand is a *lot* rarer than I'd
imagined.

Note that I've ignored packing limitations. That would reduce the
number of grains possible in any volume to a maximum of about 74% of
the superficially-calculated one; hardly significant for this
question! And needless to say, I'm also ignoring issues like 'the
universe is infinite', or 'there are an infinite number of universes',
or 'it's all in the mind', etc, etc!

Here's a brief summary:

Number in
Grain size Number in 'handfull' Number if covers Earth at:
in mm 1 cubic cm of 100 cm^3 1 metre depth 1 mm depth
---------- ---------- ----------- ------------- -----------
0.10 1.E+06 1.E+08 5.E+26 5.E+23
0.05 8.E+06 8.E+08 4.E+27 4.E+24
0.02 1.E+08 1.E+10 6.E+28 6.E+25

--
Terry, West Sussex, UK

Well its a slow afternoon and speculation is always fun :-)

I think you need to be clearer about what does and doesn't constitute
sand - surely earth doesn't count, so you are left with maybe on average
a few tens of meters worth of sand around coastlines, not including
rocky cliffs etc., plus a few sandpits in back gardens :-) I think this
would substantially reduce your estimate of the number of grains of
sand, maybe by enough to bring the number below the star count.

Regards,

Andrew

Terry Pinnell wrote:
After further googling I've still not found anything that could be
called a 'consensus' for the star number. But say it's 10^22. FWIW,
that's about ten times more than one I've seen mentioned by several
sources, of '100 billion galaxies, each averaging 10 billion stars'.
(Of course, they may each have been quoting the same source...) As
you'll have seen from my follow-up, 1mm was a typo: should have been
0.1mm. And even that's probably far too large. Examined a few grains
under a microscope, and most were more like 0.01 mm. So my current
best guess would be say 0.02 mm. IOW, you could get 50 typical grains
of sand between the 1mm divisions on a ruler.

Using 5*10^14 m^2 as a crude approximation for Earth's surface area
would imply that a sand depth as little as 1 m covering the Earth
would then contain about 6*10^28. That's a million times *more* than
the star number. For the original assertion to be true would imply a
depth of only 0.00016 mm - far less than one grain's diameter!

This is all very crude, but reinforces my suspicion that for all its
familiarity the 'sand/stars' assertion might possibly be exaggerated.
Or, of course, the number of stars is many orders of magnitude larger
than any estimate I've seen so far. Or sand is a *lot* rarer than I'd
imagined.

Note that I've ignored packing limitations. That would reduce the
number of grains possible in any volume to a maximum of about 74% of
the superficially-calculated one; hardly significant for this
question! And needless to say, I'm also ignoring issues like 'the
universe is infinite', or 'there are an infinite number of universes',
or 'it's all in the mind', etc, etc!

Here's a brief summary:

Number in
Grain size Number in 'handfull' Number if covers Earth at:
in mm 1 cubic cm of 100 cm^3 1 metre depth 1 mm depth
---------- ---------- ----------- ------------- -----------
0.10 1.E+06 1.E+08 5.E+26 5.E+23
0.05 8.E+06 8.E+08 4.E+27 4.E+24
0.02 1.E+08 1.E+10 6.E+28 6.E+25

AndrewCockburn wrote:

Well its a slow afternoon and speculation is always fun :-)

I think you need to be clearer about what does and doesn't constitute
sand - surely earth doesn't count, so you are left with maybe on average
a few tens of meters worth of sand around coastlines, not including
rocky cliffs etc., plus a few sandpits in back gardens :-) I think this
would substantially reduce your estimate of the number of grains of
sand, maybe by enough to bring the number below the star count.

What about deserts? And ocean beds, some of which I assume are covered
with sand? And other sub-surface inland deposits?

Even if only 1% of the Earth's surface is sand, that still leaves a
large gap! I reckon a more likely reconciliation (assuming the
assertion is true - which begs the question as to how the two figures
were estimated!) might be a combination of grain size assumption, and
an upward revision of the star number.

--
Terry, West Sussex, UK

Terry Pinnell wrote:
AndrewCockburn wrote:


Well its a slow afternoon and speculation is always fun :-)

I think you need to be clearer about what does and doesn't constitute
sand - surely earth doesn't count, so you are left with maybe on average
a few tens of meters worth of sand around coastlines, not including
rocky cliffs etc., plus a few sandpits in back gardens :-) I think this
would substantially reduce your estimate of the number of grains of
sand, maybe by enough to bring the number below the star count.


What about deserts? And ocean beds, some of which I assume are covered
with sand? And other sub-surface inland deposits?

Yes, deserts, forgot about them ! Ocean beds - well, not sure if they
would count, and sub-surface deposists should be ruled out IMHO, but its
your thread so you make the rules :-)

I think your right, we're still hurting for quite a few stars !

Even if only 1% of the Earth's surface is sand, that still leaves a
large gap! I reckon a more likely reconciliation (assuming the
assertion is true - which begs the question as to how the two figures
were estimated!) might be a combination of grain size assumption, and
an upward revision of the star number.

Terry Pinnell wrote:

After further googling I've still not found anything that could be
called a 'consensus' for the star number. But say it's 10^22. FWIW,
that's about ten times more than one I've seen mentioned by several
sources, of '100 billion galaxies, each averaging 10 billion stars'.
(Of course, they may each have been quoting the same source...) As
you'll have seen from my follow-up, 1mm was a typo: should have been
0.1mm. And even that's probably far too large. Examined a few grains
under a microscope, and most were more like 0.01 mm. So my current
best guess would be say 0.02 mm. IOW, you could get 50 typical grains
of sand between the 1mm divisions on a ruler.

I decided to look at the section on sand in Arthur Holmes's:
"Principles of Physical Geology" which used to be the physical
geologist's bible when I studied geology. Apparently there is
(or was) a British Standard which covered the size of sand
grains. For sand the appropriate sizes a

Coarse: 2 mm - 0.6 mm
Medium: 0.6 mm - 0.2 mm
Fine: 0.2 mm - 0.06 mm

To complete the picture, Gravel is:

Coarse: 60 mm - 20 mm
Medium: 20 mm - 6 mm
Fine: 6 mm - 2 mm

Pebbles are 200 mm to 60 mm and Boulders are 200 mm

At sizes smaller than that of Sand, Silt is defined as:

Coarse: 0.06 mm - 0.02 mm
Medium: 0.02 mm - 0.006 mm
Fine: 0.006 mm - 0.002 mm

Clay or Mud has particle sizes of 0.002 mm.

--
Mike Humberston
WARNING: Spam trap in operation. Send any e-mail reply to mike, not oblivion.

They should have kept going with the larger gradings. Then we'd really know
if Pluto is a planet!
Ed.

"Mike Humberston" wrote in message
I decided to look at the section on sand in Arthur Holmes's:
"Principles of Physical Geology" which used to be the physical
geologist's bible when I studied geology. Apparently there is
(or was) a British Standard which covered the size of sand
grains. For sand the appropriate sizes a

Coarse: 2 mm - 0.6 mm
Medium: 0.6 mm - 0.2 mm
Fine: 0.2 mm - 0.06 mm

To complete the picture, Gravel is:

Coarse: 60 mm - 20 mm
Medium: 20 mm - 6 mm
Fine: 6 mm - 2 mm

Pebbles are 200 mm to 60 mm and Boulders are 200 mm

At sizes smaller than that of Sand, Silt is defined as:

Coarse: 0.06 mm - 0.02 mm
Medium: 0.02 mm - 0.006 mm
Fine: 0.006 mm - 0.002 mm

Clay or Mud has particle sizes of 0.002 mm.

--
Mike Humberston
WARNING: Spam trap in operation. Send any e-mail reply to mike, not
oblivion.

Mike Humberston wrote:

I decided to look at the section on sand in Arthur Holmes's:
"Principles of Physical Geology" which used to be the physical
geologist's bible when I studied geology. Apparently there is
(or was) a British Standard which covered the size of sand
grains. For sand the appropriate sizes a

Coarse: 2 mm - 0.6 mm
Medium: 0.6 mm - 0.2 mm
Fine: 0.2 mm - 0.06 mm

To complete the picture, Gravel is:

Coarse: 60 mm - 20 mm
Medium: 20 mm - 6 mm
Fine: 6 mm - 2 mm

Pebbles are 200 mm to 60 mm and Boulders are 200 mm

At sizes smaller than that of Sand, Silt is defined as:

Coarse: 0.06 mm - 0.02 mm
Medium: 0.02 mm - 0.006 mm
Fine: 0.006 mm - 0.002 mm

Clay or Mud has particle sizes of 0.002 mm.

Thanks. I found rather similar definitions myself elsewhere yesterday.
Covers quite a range! I suppose the sand I'm thinking of in this
context (like that I was walking on near Leiden, or the stuff in my
garden shed) is 'fine' then. Although must say I'm surprised at that
lower limit of .06 mm. Unless I made a basic error, the grains I
viewed under my microscope (alongside a crude 1 mm scale) were smaller
than that.

--
Terry, West Sussex, UK

Terry Pinnell wrote:

Although must say I'm surprised at that
lower limit of .06 mm. Unless I made a basic error, the grains I
viewed under my microscope (alongside a crude 1 mm scale) were smaller
than that.

I was surprised that your sand grains were so small. My local sand
grains seem much bigger, but I haven't measured them.

Pau
--
http://www.wilderness-wales.co.uk
http://www.wildwales.fsnet.co.uk
http://www.photosig.com/go/users/userphotos?id=118749

"Paul Saunders" wrote:

Terry Pinnell wrote:

Although must say I'm surprised at that
lower limit of .06 mm. Unless I made a basic error, the grains I
viewed under my microscope (alongside a crude 1 mm scale) were smaller
than that.

I was surprised that your sand grains were so small. My local sand
grains seem much bigger, but I haven't measured them.

I wonder if the handling procees, placing a pinch on the slide and
smoothing it to a layer I could illuminate and view, somehow 'crushed'
the grains? I'd sort of assumed they were very hard, impervious to
anything but determined crushing, but maybe I'm wrong.

--
Terry, West Sussex, UK