Re: A big whack that made the moon may have also created continents that move

In alt.astronomy Jim Wilkins <[email protected]> wrote:
> "Mad Hamish"  wrote in message 
> news:[email protected]...
> 
> On Fri, 21 Jun 2024 16:47:23 -0400, "Jim Wilkins"
> <[email protected]> wrote:
> 
>>"a425couple"  wrote in message news:[email protected]...
>>
>>A big whack that made the moon may have also created continents that move
>>
>>------------------------------
>>https://en.wikipedia.org/wiki/Alfred_Wegener
>>
>>In 1912 he presented his theory that continents drift around and were once
>>assembled. After his death the Nazis picked up on and promoted it, which
>>tainted the concept so much that it was buried, and only resurrected when a
>>grad student independently noticed and popularized the proposal and thus
>>freed it from its political stigma.
>>
> 
> A big issue was also that he had absolutely no mechanism for how they
> could have moved
> 
> Then somebody showed that crystals showed changing magnetic fields
> that would happen if the continents had moved as well as sea floor
> observations backing it up
> -----------------------------------
> A mechanism is easy. It had long been known that temperature increases with 
> the depth in a mine.
> From 1869:
> https://www.scientificamerican.com/article/on-the-temperature-of-coal-mines/
> 
> If that was all people knew, linearly projecting an observed 1F rise every 
> ~60 feet would give the temperature of molten iron below 30 miles. 
> Presumably convection cells would moderate the rate of rise below that, and 
> also create horizontal drag against the solid surface. Volcanos prove that 
> at least some of the rock down there is molten.
> 
> A college physics problem had us integrating the net force of gravity with 
> depth, to determine the return time of a weight dropped into a vacuum well 
> through Earth (of uniform density). An unexpected result of the calculus was 
> that gravitational attraction is zero anywhere within a hollow shell (Dyson 
> sphere), only the ball below you attracts.
...

Gauses Theorem (1777-1855).  Applies to spherically symmetric masses. 
May not apply to holes rilled through the earth. :)