Arizona weekly citizen., 1882-03-12
The Origin of Our Mo0n-

 tinguished English scientist, delivered a lecture, recently lu which he incidentally alluded to the probable formation of our moon in the following terms:
 Let us leave the earth for a few minutes, and examine the past history of the moon. We have seen the moon revolves around the earth in an ever widening orbit, and consequently the moon must in ancient times have been nzarer the earth than 1t IS now NOdOubt | the change Is slow. There ls not mach difference between the orbit or the moon a thOusahd year ago and the orblt III which the moon Is now moving. But when We rise to millions of years the difference become very appreclable- ! Thirty or forty millions of years ago tho moon was much closer to the earth than It IS at present; very possibly the moon was then only half lts present distance, We must, however, look stlll earlier, to certain epoch not less than fifty millions of years ago. At that epoch the moon must have been SO close to the earth that the two bodies were almost touching.
 Every body knows that the moon re- wolves now around the earth iu a period of tweuty-seveu days. The period depends upon the distance between the earth and the moon. The time and ths distance are connected together by Onc of Kepler's celebrated laws, 80 that, as the distance shOrteus, SD must the time of re sUlutlOn shorten. In earlier times the month must have been shorter than our present month. Some millions Ot years ago the moon completed Its jour ney in a week instead of taking twenty seven days, as at present. Looking back earlier still, we find the month has dwindled down Co a day, then tO 6 few hours, until at that wOnderUUs spOch vhed the moon WAS almost touching the earth, the moon spun round the eartk once every thres hours.
 We have hitherto been guided by the unerring light of dynauics, but at this mOmentOus epoch dynamics desert us aud we have only probability tO guid.' our ialtering steps. One hint, however, dynamics does give. It reminds Us that a rotation once in three hours IS very close to the quickest rotation which the earth could have without falling G. pieces. DAs the earth was thus disposed tO rupture, 1t Is of extreme interest tO observe that a cause tending to preciPi- tate such rupture was then ready tO hand. It seems not unlikely that we are indebted tO the sun as the occasion Ly which the moon was fractured of from the earth and assumed the dignity of an independent body.
 It must be remembered that the sun produces tides ID the earth as well as the moon, but the solar tides are sO small compared with the lunar tides, that We have hitherto been enabled Co neglect them. There could. however. have been no lunar tides before the moon existed and consequently in the early ages before the moon was detached the earth was disturbed by the sOlar tides. aud by the solar tides alone.
 The p-imEval earth thus rose and fell under the tidal action of the sun. Prob ably there were no oceans then on the earth; but tides do not require oceans or even water for their operation. Tbe primitive tides were manifest as throbs ID the actual body of the earth itself, which was then iu more or less fluid condition.
 At the remote CT och of which We are speaking the solar tides were very small Is they are at present. Yet, small as they are, there was particular cIrcum- stance which may have enormously in- f-tlHttA AAltAL flNfA kAA4NNa Aht InAiAA AN which ] refer can be illustrated very simply We have here a weight of lbs freely suspended, and here l have small wooden nailet which barely weighs half an ounce. yet small as thls mallet is l can make the heavy weight swing by merely giving it blows with the mallet. Let me try. l give the weight blew after blow. hit 1t as hard as l cau, ,r..kk [ har-s. not yet beeu successful. The art ot succeeding Is merely to time the blows properly; this Lam now dOIug, and you see the weight swiugs m an arc which Is steadily augmenting.
 We therefore see that a succession or impules, in themselves small, can yet produce a great effect when they are properly timed. In the present case the impulses should succeed eaeA other at the same interval as this pendulum re- quires for one two-and-frO oscillation The time therefore depends on the body struck, and not at all on the body which gives the impulses.
 Just as this pendulum swings yltf-2 definite period SD the vlbratlOns Of the primRvai earth had a certain peuOd ap- pToprIats tO them. Suppose that the hquid primmyal globe were pressed m on two quadrants and drawn out on the two others, and that the pressures were then released. The globe would akemp; to regain its original form, but this it could not do at once, any more than the pendulum can at once regain it's vertical position; the pTOtruded portions would go in, but they would overshoOt the mark and the globe would thus Oscillate to and fro. Now 1t has been shown that the period of such oscillations in our primitive globe is about an hour and half, or very closely to half the sup posed length of the day at that time. The solar tides, however, also have a period half the length of the day. Here then We have case preci ely analogous to the l4 pound weight have just experiment. cd on. We have a succession of small impulses gwen which are timed to har- mOnize with the natural vibrations. Just a. the small timed impulses raised large vibration in the weight, 30 the small sc- lar tides on the earth threw the earth into large vibration. At first these yi- brations were small but at each succeed ing impulse the amplitude was augu- mented, until at length the cohesion of the molten matter c, uld no longer re- sist; separation took place; one portion consolidated to form our present earth; the other portion consolidated to form the moon.