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Re: Bulges



At 10:59 AM 3/1/97 -0700, Dave wrote the following:

In the System of the World (Book III of Principia), Newton clearly
indicates that there are two tides per day and draws an ellipse that
represents a cross section of the Earth (showing bulges on both sides).

Yes, he does -- but there is a bit of confusion here, There are TWO
"Systems of the World" -- one is indeed Book III of the Principia, But I
think you are referring to "The System of the World" (not part of the
Principia, but sometimes bound with it (It *is* in the Cajori/UC version.)

I assume you are referring to Pars 49 to 54, where he drills two tunnels
through the center of the Earth (thereby cremating himself and creating the
largest volcano in history). He does not use the term "bulges" nor does he
resort to a Moon/Earth CM, but no matter. He *does* use unintelligible
language. If anyone wants to translate to 20thC American, the physics
community would surely be very grateful indeed.

He talks about the tides in Book I. I need to review that.

I tried to find a CM explanation in the intro books that I have here, but
could not. Any references?????

Jim Green


He goes so far as to explain some unusual occurrences that had been noted
by sailors in Batshaw and the kingdom of Tunquin that, on the day
following the moon's transition from one side of the equator to the
other, there is only one tide per day.

In my quick perusal of this passage, however, I cannot find where he
explains why there must be bulges on opposite sides of the Earth.

Am I wrong in thinking that the usual attribution of TWO tidal bulges is to
Newton? And he did this by recognizing that the Moon/Earth system revolves
about the mutual center of mass. This is certainly the presentation in
various physics texts. But I don't find these thoughts in the Principia.

Can the list help?


Jim Green
JMGreen@sisna.com


It has been my impression that Newton did not understand that his theory
predicts two tides. I have not read the Principia.

Leigh


David J. Hamilton, Ed.D. "And gladly wolde he lerne,
Franklin HS, Portland, OR and gladly teche."
djhamil@teleport.com Geoffrey Chaucer