Page:Popular Science Monthly Volume 16.djvu/180

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166
THE POPULAR SCIENCE MONTHLY.

sarily be small, whereas it may happen that the original number is so large that its division by a million seems to make little impression on it. According to the best authorities, a bulb of the size of the one before you (13·5 centimetres in diameter) contains more than 1,000000,000000,000000,000000 (a quadrillion) molecules. Now, when exhausted to a millionth of an atmosphere we shall still have a trillion molecules left in the bulb—a number quite sufficient to justify me in speaking of the residue as matter.

To suggest some idea of this vast number, I take the exhausted bulb, and perforate it by a spark from the induction-coil. The spark produces a hole of microscopical fineness, yet sufficient to allow molecules to penetrate and to destroy the vacuum. The inrush of air impinges against the vanes and sets them rotating after the manner of a windmill. Let us suppose the molecules to be of such a size that, at every second of time, a hundred million could enter. How long, think you, would it take for this small vessel to get full of air? An hour? A day? A year? A century? Nay, almost an eternity!—a time so enormous that imagination itself can not grasp the reality. Supposing this exhausted glass bulb, indued with indestructibility, had been pierced at the birth of the solar system; supposing it to have been present when the earth was without form and void; supposing it to have borne witness to all the stupendous changes evolved during the full cycles of geologic time, to have seen the first living creature appear, and the last man disappear; supposing it to survive until the fulfillment of the mathematicians' prediction that the sun, the source of energy, four million centuries from its formation will ultimately become a burned-out cinder;[1] supposing all this—at the rate of filling I have just described, one hundred million molecules a second—this little bulb even then would scarcely have admitted its full quadrillion of molecules,[2]

But what will you say if I tell you that all these molecules, this quadrillion of molecules, will enter through the microscopic hole be-

  1. The possible duration of the sun from formation to extinction has been variously estimated by different authorities at from eighteen million years to four hundred million years. For the purpose of this illustration I have taken the highest estimate.
  2. According to Mr. Johnstone Stoney ("Philosophical Magazine," vol. xsxvi., p. 141), 1 c. c. of air contains about 1000,000000,000000,000000 molecules. Therefore, a bulk 13·5 centims. diameter contains 13·5 X 0·5236 X 1000,000000,000000,000000 or 1,288252,350000,000000,000000 molecules of air at the ordinary pressure. Therefore the bulk, when exhausted to the millionth of an atmosphere, contains 1,288252,350000,000000 molecules, leaving 1,288251,061747,650000,000000 molecules to enter through the perforation. At the rate of 100,000000 molecules a second, the time required for them all to enter will be—

    12882,510617,476500 seconds, or
    214,708510,291275 minutes, or
    3,578475,171521 hours, or
    140103,132147 days, or
    408,501731 years.