JF Ptak Science Books Post 2259
In three issues1 of Nature (London) magazine in 1883, William Thomson (Lord Kelvin)--polymath of a great and inquisitive mind--tried to establish a good reference point for the size of atoms, mainly to establish that their size while being incredibly small were not unimaginably so, and that even objects of this minor magnitude could be approximated and studied. And he did so with great ease and in a popular general-audience sort of way.
All told, this was a very good piece of thinking, especially referencing the estimates of Niels Bohr 30 years later, publishing in the Philosophical Magazine (volume 26, pp 1-25, 1913) and calculating the size of an atom at .5 x -10 meters. And even though Thomson is talking about his estimates in terms opf science in a post-Dalton and post-Mendeleyeev world, he is also pre-Stoney, and Roentgen and Curie and Soddy and everyone else, especially pre-atomic-nucleus, and pre-proton (1919/20 with Rutherford and Moseley) and pre-neutron (Chadwick 1932), which are smaller still than the atom. Way smaller. It is difficult to put into understandable terms on how "small" that small is: the atomic nucleus is sort of 1/10,000th of the atom, and a proton or neutron smaller still, and then the quark smaller than that, until perhaps it becomes a Seussian exercise with future discoveries showing that after everything is said and done that it is turtles all the way down.
But Thomson managed to put an understandable assessment on a very difficult visualization, talking in terms of an atom being "1/10,000,000 or from 1/10,000,000 to 1/100,000,000 of a centimetre in diameter", or 1x10-7meters, which is just about the size of a cell nucleus or DNA; that's in the neighborhood, especially if you look at the smaller number which is 10-8 meters, which starts to close in on the size of the massive carbon atom (10-10), but sorta not so close to the electron (10-12) , or carbon atom nucleus (10-14) or proton (10-15). Small, hazy stuff indeed, filled with nothing. On the other hand, if you proceeded in a space vehicle 1014 meters from Earth our Solar System would appear as just another fuzzy splotch in the sky. 1016 meters is about a light year, and then it would taken 10,000 of those "just" to get slightly outside our galaxy. And then there's the rest.
In any event, Thomson did okay. And as it turns out (as I just now learned) there was an earlier Nature article in 1870 (the inaugural year of the journal) by its editor Norman Lockyer who estimated the size of atoms at just about the Thomson scale.
"FOUR lines of argument founded on observation have
led to the conclusion that atoms or molecules are
not inconceivably, not immeasurably small. I u;e the
words " inconceivably" and "immeasurably" advisedly.
That which is measurable is not inconceivable, and there-
fore the two words put together constitute a tautology.
We leave inconceivableness in fact to metaphysicians.
Nothing that we can measure is inconceivably large or
inconceivably small in physical science. It may be diffi-
cult to understand the numbers expressing the magnitude,
but whether it be very large or very small there is nothing
inconceivable in the nature of the thing because of its
greatness or smallness, or in our views and appreciation
and numerical expression of the magnitude. The general
result of the four lines of reasoning to which I have re-
ferred, founded respectively on the undulatory theory of
light, on the phenomena of contact electricity, on capil-
lary attraction, and on the kinetic theory of gases, agrees
in showing that the atoms or molecules of ordinary matter
must be something like the 1/10,000,000, or from the
1/10,000 000 to the 1/100000,000 of a centimetre in dia-
meter."--Thomson, below.
Notes:
1. William Thomson, The Size of Atoms, I pp 203-205, June 28, 1883; Size of Atoms II, pp 250-254, July 12, 1883; Size of Atoms III, pp 274-278, July 19, 1883, earlier presented before the Royal Institution, beginning February 2, 1883.
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