Has anyone ever proposed in the Annals of Improbable Research or a similar venue that, in addition to undergoing periodic reversals of its magnetic field, Earth is also subject to occasional short-lasting reversals of its gravitational field? Such a phenomenon would handily explain selective extinction of megafauna: a mouse could survive an upward fall for five seconds followed by a downward fall for five seconds followed by an extreme deceleration, but a mastodon would not fare as well. :-) Jim Propp
that this could also drive continental drift. a sphere with positive mass becomes oblate when spinning, while one with negative mass becomes prolate. Cris On Jan 11, 2014, at 8:37 PM, James Propp <jamespropp@gmail.com> wrote:
Has anyone ever proposed in the Annals of Improbable Research or a similar venue that, in addition to undergoing periodic reversals of its magnetic field, Earth is also subject to occasional short-lasting reversals of its gravitational field?
Such a phenomenon would handily explain selective extinction of megafauna: a mouse could survive an upward fall for five seconds followed by a downward fall for five seconds followed by an extreme deceleration, but a mastodon would not fare as well. :-)
Jim Propp _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
Has anyone ever proposed in the Annals of Improbable Research or a similar venue that, in addition to undergoing periodic reversals of its magnetic field, Earth is also subject to occasional short-lasting reversals of its gravitational field?
For Einstein gravity, the equivalence principle holds literally; the sign of m (or of M) doesn't reverse the dynamics. A negative-mass dinosaur will experience an upward force, which will make it fall in a downward direction, still at 1 gee. Joshua
Doesn't the acceleration of gravity reverse when time procedes in a negative direction? --Dan On 2014-01-11, at 7:37 PM, James Propp wrote:
Has anyone ever proposed in the Annals of Improbable Research or a similar venue that, in addition to undergoing periodic reversals of its magnetic field, Earth is also subject to occasional short-lasting reversals of its gravitational field?
Such a phenomenon would handily explain selective extinction of megafauna: a mouse could survive an upward fall for five seconds followed by a downward fall for five seconds followed by an extreme deceleration, but a mastodon would not fare as well. :-)
Jim Propp _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
No, because acceleration is second derivative in time, it remains the same when t is replaced by -t. On the other hand, acceleration is reversed when t is replaced by it. -- Gene
________________________________ From: Dan Asimov <dasimov@earthlink.net> To: math-fun <math-fun@mailman.xmission.com> Sent: Saturday, January 11, 2014 9:07 PM Subject: Re: [math-fun] Big Splat theory
Doesn't the acceleration of gravity reverse when time procedes in a negative direction?
--Dan
On 2014-01-11, at 7:37 PM, James Propp wrote:
Has anyone ever proposed in the Annals of Improbable Research or a similar venue that, in addition to undergoing periodic reversals of its magnetic field, Earth is also subject to occasional short-lasting reversals of its gravitational field?
Such a phenomenon would handily explain selective extinction of megafauna: a mouse could survive an upward fall for five seconds followed by a downward fall for five seconds followed by an extreme deceleration, but a mastodon would not fare as well. :-)
Jim Propp
On 1/11/2014 7:37 PM, James Propp wrote:
Has anyone ever proposed in the Annals of Improbable Research or a similar venue that, in addition to undergoing periodic reversals of its magnetic field, Earth is also subject to occasional short-lasting reversals of its gravitational field?
Since gravity is always attractive, would reversal make any difference. Brent
Such a phenomenon would handily explain selective extinction of megafauna: a mouse could survive an upward fall for five seconds followed by a downward fall for five seconds followed by an extreme deceleration, but a mastodon would not fare as well. :-)
Jim Propp _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
Brent, My intended meaning for "reversal" is that attraction would become repulsion. You're quite right that (as Josh Burton just reminded me) in Einstein's theory of gravity, the sign of the mass of a body doesn't affect the dynamics. I was conceiving of the joke in a Newtonian framework. All comments are welcome, but I'm especially interested in ones that, like Cris Moore's, expand on the scenario in a goofy but scientific way (e.g., invoking the theory to explain how the Moon lost its atmosphere). Jim On Sunday, January 12, 2014, meekerdb wrote:
On 1/11/2014 7:37 PM, James Propp wrote:
Has anyone ever proposed in the Annals of Improbable Research or a similar venue that, in addition to undergoing periodic reversals of its magnetic field, Earth is also subject to occasional short-lasting reversals of its gravitational field?
Since gravity is always attractive, would reversal make any difference.
Brent
Such a phenomenon would handily explain selective extinction of megafauna: a mouse could survive an upward fall for five seconds followed by a downward fall for five seconds followed by an extreme deceleration, but a mastodon would not fare as well. :-)
Jim Propp _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun
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Please omit Marc Abrahams from your distribution lists in posting on this thread. I meant to bcc him and cc'd him instead. Jim Propp On Saturday, January 11, 2014, James Propp wrote:
Has anyone ever proposed in the Annals of Improbable Research or a similar venue that, in addition to undergoing periodic reversals of its magnetic field, Earth is also subject to occasional short-lasting reversals of its gravitational field?
Such a phenomenon would handily explain selective extinction of megafauna: a mouse could survive an upward fall for five seconds followed by a downward fall for five seconds followed by an extreme deceleration, but a mastodon would not fare as well. :-)
Jim Propp
I have now irrevocably peed this idea into the global meme-pool: https://www.youtube.com/watch?v=JeAnr-EJ48M Jim Propp On Sat, Jan 11, 2014 at 10:37 PM, James Propp <jamespropp@gmail.com> wrote:
Has anyone ever proposed in the Annals of Improbable Research or a similar venue that, in addition to undergoing periodic reversals of its magnetic field, Earth is also subject to occasional short-lasting reversals of its gravitational field?
Such a phenomenon would handily explain selective extinction of megafauna: a mouse could survive an upward fall for five seconds followed by a downward fall for five seconds followed by an extreme deceleration, but a mastodon would not fare as well. :-)
Jim Propp
A compelling theory, brilliantly delivered. The best moments, for me and I think the audience too, were those when you had us guessing: where is he going with this? — as in 0.000002 0.000000 -Veit
On Aug 29, 2017, at 5:20 PM, James Propp <jamespropp@gmail.com> wrote:
I have now irrevocably peed this idea into the global meme-pool:
https://www.youtube.com/watch?v=JeAnr-EJ48M
Jim Propp
On Sat, Jan 11, 2014 at 10:37 PM, James Propp <jamespropp@gmail.com> wrote:
Has anyone ever proposed in the Annals of Improbable Research or a similar venue that, in addition to undergoing periodic reversals of its magnetic field, Earth is also subject to occasional short-lasting reversals of its gravitational field?
Such a phenomenon would handily explain selective extinction of megafauna: a mouse could survive an upward fall for five seconds followed by a downward fall for five seconds followed by an extreme deceleration, but a mastodon would not fare as well. :-)
Jim Propp
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participants (7)
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Cris Moore -
Dan Asimov -
Eugene Salamin -
James Propp -
Joshua W. Burton -
meekerdb -
Veit Elser