Re: Before Now

Eliezer Yudkowsky (
Wed, 22 Jan 1997 20:34:58 -0600

[Hara Ra admonishes Dan Fabulich:]
> One of things I value about this list is the member's love of accuracy
> when it comes to provable facts, in this case Special Relativity (and
> possibly General Relativity). Either learn your math or be respectful of
> those of us who do know it.

One of the things I could only wish I valued about this list is
hospitality to newcomers, especially nervous ones, and not telling them
to shut up even if they do make an error.

One of the things I *do* value about this list is the citation and
explanation of facts instead of standing on your authority.

Special Relativity says that lost time is equal to the 'tau' factor,
/ v^2
/ 1 - ---
\/ c^2

Let's suppose you're in an airplane going one mile per second, around
Mach 5 or 6. This is considerably faster than the Concorde. This
airplane is going around 1/186000 as fast as a ray of light. Now v
over c is squared, so tau here is equal to 1 - 1/(186,000 * 186,000), or
.99999999997 or (1 - 0.0000000000289051)

So if your airplane trip lasted a year, your total loss of time due to
Special Relativity is equal to:
912 microseconds, or just less than one thousandth of a second.

By comparision, I believe that the smallest interval of time perceptible
to a human is between 10 and 20 thousandths of a second. You would thus
have to circle the globe two hundred and fourteen thousand times, over
the course of around seventeen years, before losing an amount of time
large enough to perceive.

(Boy, you don't really appreciate the people who popularize Special
Relativity until you have to strangle yourself to keep from saying
"frame of reference" every six words.)

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.

--       Eliezer S. Yudkowsky

Disclaimer:  Unless otherwise specified, I'm not telling you
everything I think I know.