Jason Cawley
Wolfram Science Group
Phoenix, AZ USA
Registered: Aug 2003
Posts: 712 |
Lucretius
As a note this week, I thought I'd discuss two ancient ideas that have always struck me as among the more impressive achieved without the benefit of instruments, or much of the conceptual foundation of modern science, that can be found already in Lucretius by around 100 AD. The NKS book mentions one of these on page 860 in the note "History of Programs and Nature". It is also mentioned again in the note on "Atomism" on page 876.
Lucretius did not come up with the idea of atoms. That is attributed to Leucippus, and was developed further by Democritus, before being adopted as doctrine by Epicurus and his whole school.
But it is in Lucretius that we find the most striking evidence presented in favor of the idea. It may well have been noticed long before him, sometime in the history of the Epicureans, and he may simply be passing it on. The evidence is from an observation rather than an argument, of what may be called "motes in sunbeams".
These are actually visible blood cells on the surface of the human eye. The argument that they are on the surface of the eye is attributed to Leonardo during the renaissance, but it is always hard to tell whether such attributions are apocryphal. One can see them as translucent spots whenever looking in the direction of any bright light. It helps if you deliberately "unfocus" your eyes. It is an extraordinary thing to have noticed, and the reasoning applied to it is likewise beyond expectations.
"...behold whenever
The sun's light and the rays, let in, pour down
Across dark halls of houses: thou wilt see
The many mites in many a manner mixed
Amid a void in the very light of the rays,
And battling on, as in eternal strife,
And in battalions contending without halt,
In meetings, partings, harried up and down."
So clearly, this is what he is talking about, he has seen it and any of us can verify for ourselves what his evidence is. What does he see in it?
"From this thou mayest conjecture of what sort
The ceaseless tossing of primordial seeds
Amid the mightier void...
"...such tumblings are a sign
That motions also of the primal stuff
Secret and viewless lurk beneath, behind.
For thou wilt mark here many a speck, impelled
By viewless blows, to change its little course,
And beaten backwards to return again,
Hither and thither in all directions round."
Centuries upon centuries before "Brownian motion", the basic phenomenon was noticed and described. It is also impressive that Lucretius was well aware he was looking at something that must be much larger than actual atoms, that only appears at a higher level of aggregation.
"... motion ascends from the primevals on,
And stage by stage emerges to our sense,
Until those objects also move which we
Can mark in sunbeams, though it not appears
What blows do urge them."
Well, I call that pretty impressive as a thing to notice without instruments.
There is one further idea in Lucretius that is more directly related to NKS thinking, and is the subject of the two notes about him in the book. It concerns the analogy of human language to natural complexity. The question is how a finite number of types of atoms could create all the various phenomena we see, simply by arrangement. Lucretius appeals to his own writing to illustrate the "how" that might be involved in that.
"...here in these our verses,
Elements many, common to many words,
Thou seest, though yet 'tis needful to confess
The words and verses differ, each from each,
Compounded out of different elements"
"Not since few only, as common letters, run
Through all the words, or no two words are made,
One and the other, from all like elements,
But since they all, as general rule, are not
The same as all. Thus, too, in other things,
Whilst many germs common to many things
There are, yet they, combined among themselves,
Can form new wholes to others quite unlike."
It is interesting to see alphabetical language here given as the paradigm of complex variety from simple underlying components.
Lucretius went on to deduce that the number of basic types or elements must be finite. (Having any size, the number of arrangements possible before getting too large to see is bounded).
No doubt one can also find less sensible things in Lucretius, if one tries. I still find in fascinating that anyone managed to notice such things so long ago. For what it is worth.
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