Re: Before Now

Damien Broderick (
Fri, 24 Jan 1997 12:39:17 +1000

>From: Eliezer Yudkowsky <>
>> Somebody else says that you actually gain time due to General
>> Relativity, which says that time slows down close to a large mass [i.e.
>> speeds up in an airplane], but I can't calculate that.
Hal comments:

> A commercial jet flying at 10000 m will therefore have a
>speedup due to GR of about 10^-10. This is an order of magnitude more
>than the relativistic slowdown of even the mile per second plane, so
>it will swamp that effect in normal situations.

This has been an empirical issue for many years. A quick hunt of my shelves
does not locate the detailed account, which I recall showed a (very small)
overall loss of time in the airborne clock. Britannica says: `The
clock-paradox effect also has been substantiated by experiments comparing
the elapsed time of an atomic clock on Earth with that of an atomic clock
flown in an airplane. The latter experiments. furthermore, have confirmed a
gravitational contribution to time dilation, as predicted by the theory of
general relativity.' No plus or minus signs, damn it, but presumably if the
joint effect had conformed with Hal's estimate this would have deserved
mention in the EB.

Damien Broderick