20.500 matters of scale and imagination

               Humanist Discussion Group, Vol. 20, No. 500.
       Centre for Computing in the Humanities, King's College London
  www.kcl.ac.uk/schools/humanities/cch/research/publications/humanist.html
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         Date: Thu, 08 Mar 2007 06:01:48 +0000
         From: Norman Gray <norman_at_astro.gla.ac.uk>
         Subject: Re: 20.483 matters of scale and imagination

Willard, greetings.

On 2007 Mar 3 , at 09.27, Humanist Discussion Group (by way of
Willard McCarty <willard.mccarty_at_kcl.ac.uk>) wrote:

>I count 3 orders of magnitude (from 10**1 to 10**-1 meters) in a
>scale of 40 without any kind of prosthetic.

I have reasonably good eyesight, so I can see the sea horizon
(probably something like 10km away depending on the weather), and a
hair (something less than 0.1mm across) without prosthetics, so
that's 10^4m -- 10^-4m: eight orders of magnitude purely on earth.

If you look at the moon, however, you're seeing something 3500km
across, and the sun is 10^9m across, both of which you can see with
the naked eye, so that makes 10 to 13 orders of magnitude without
squinting.

>Perhaps someone here can
>provide a count beyond those 3 orders of magnitude of actual images
>we are capable of generating with current physical systems.

If you say `actual images' in order to contrast with the artist's
impressions in the (excellent!) powers-of-ten link, then yes, we can
do a large proportion of the full range.

At the top end, COBE's famous image[1] is indeed an image of the
entire universe (say 10^25 to 10^26m). At the other end, images from
a particle physics detector[2] tend not to reconstruct the tracks
right down to the vertex, so that Matt Jensen's STM image is probably
as far as you can go in that direction (namely atoms, 10^-10m). In
both cases, this is probably about as far as it is possible to go in
principle, since in both cases, you're at the sort of scale where
`how long is this?' becomes an exciting technical question.

It's hard to go beyond the size of the universe even in our
(physical) imagination, though we can go a few more powers of ten
downwards, with the smallest things discussed in physics round about
10^-35m.

Norman

[1] http://en.wikipedia.org/wiki/Image:COBE_cmb_fluctuations.gif
[2] http://cdsweb.cern.ch/record/42317 (this is an image of the
detector-wide tracks, so on the scale of metres)

-- 
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Norman Gray  /  http://nxg.me.uk
eurovotech.org  /  University of Leicester, UK