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