ATM analogy help - numbers of boxcars, sand, stars, and galaxies

["Bell, Andrew" <AMB2@pge.com>]

> I like using analogies like this, too, although I had never before run
> across this particular one.  I just did a Google search on various
> combinations of "boxcar", "salt" or "sand", "stars", and "galaxies."
> After casting aside miscellaneous odd hits like a long Robert Hunter poem
> ("Voyage of the Marie Hind") and an unrelated passage at the end of first
> chapter of "Dharma Bums" (Kerouac), I came across this kind of interesting
> snippet:
> 
> "Let me give an analogy or a commentary of sorts on the words we read in
> Proverbs 8:
> 
> "If you take a thimble full of sand, the grains of sand in that thimble
> would be approximately equal to the number of stars you can see with your
> naked eye.
> 
> "If you then filled up a wheelbarrow full of sand, that would represent
> about the number of stars you can see with modern telescopes.
> 
> "But if you then filled up boxcars full of that sand, and those boxcars
> went by at the rate of one every two minutes, and those boxcars went by
> for a week without stopping (that's over 5000 box cars), that represents
> the number of stars in the known universe. And God, the almighty God is
> behind all this and more, there is an amazing, overwhelming grandeur and
> mystery about God."
> 
> The full text is from a Trinity Sunday sermon given at a Presbyterian
> church outside of Atlanta, just this past June:
> http://www.northminster-atl.org/sermons/20010610.htm.  Not the usual
> source that I would look to for information like this, but it doesn't
> actually seem to be too wide of the mark.
> 
> If you take a "thimbleful" as being roughly 1 cubic centimeter, and 6,000
> stars as visible to the naked eye, that sounds pretty close for grains of
> sand.  (Salt would usually be even finer.)  I would take a wheelbarrow as
> holding a couple of cubic feet -- about 50,000 cubic centimeters, or
> one-twentieth of a cubic meter.  That would put something like 300 million
> "stars" in the wheelbarrow, which should get you down to somewhere around
> everything visible to the 16th magnitude.
> 
> The usual estimate for number of stars in the entire Milky Way is around
> 100 billion.  So you would only need 300 or so wheelbarrow loads to cart
> off the whole galaxy -- just 15 or so cubic meters.  I would take a
> standard boxcar load as being perhaps 150 cubic meters (e.g., ten meters
> long by three meters wide by five meters high), so there'd be enough room
> just in the first boxcar to pack in the entire Local Group (perhaps 500
> billion stars) with plenty of room to spare.
> 
> The 5,000 boxcar estimate for the whole universe does seem a bit low.
> (And the "train" seems a bit slow, with only one car rumbling by every two
> minutes.)  Relying on a more conventional source for the number of
> galaxies in the universe (e.g.,
> http://hypertextbook.com/facts/TopazMurray.shtml), it seems like 10-100
> billion is a fairly standard estimate.  The Milky Way is a significantly
> larger-than average galaxy.  Using the Local Group as an average-density
> sub-cluster, we might be able to count on loading 100 or so galaxies into
> each boxcar.  So the train might run from a hundred million up to a
> billion boxcars all told -- running past you at two cars per second over a
> good section of track, you could probably watch the whole train over a
> period of somewhere between two and twenty years.
> 
> -- Andrew Bell [who finds analogies like thimbles, wheelbarrows, and
> boxcars much more helpful than the usual "bill-ions and bill-ions"]
> 
> --------------------------------------------------------------------------
> -----------------------------------
> Date: Tue, 02 Oct 2001 17:08:19 -0500
> From: Eric Uthus <eric_uthus@und.nodak.edu>
> Subject: ATM analogy help - somewhat off topic
> 
> Somewhere in my astronomy readings I read an analogy relating the number
> of
> stars in the universe to grains of salt in boxcars and the length of the
> train of boxcars.  I'd like to use this when I have people look through my
> telescope but I can't remember where I read it.  Has anyone else seen this
> and remember where it was printed?  I've looked through my astronomy
> books,
> telescope making books and my past Sky and Telescopes but can't find it.
> Any help pointing me to this would be appreciated.
>