X-Message-Number: 11332
Date: Sun, 28 Feb 1999 10:20:01 EST
Subject: quickies

A couple of quickies:

1. John de Rivaz had some interesting remarks about math vs. reality, with an
example of "- 6 men" as an inadmissible solution to a ditch-digging problem.
Of course, the whole concept of "negative numbers" probably seemed bizarre at
one time--yet we know how useful it is. There aren't any "negative men," but
there is such a thing as subtracting 6 men from 8, say, which can also be
phrased as adding a negative 6 men to a positive 8. And complex numbers are
extremely useful, whether or not there "really" is a square root of negative

John is right about "proving mathematically" that nothing (with positive rest
mass) can reach the speed of light only AFTER assuming (in deriving the
Lorentz transformation) that the speed of light in vacuo is constant in any
inertial system. (I used to go through that in the classroom for my students.)
No conclusion is stronger than its premises, and the premises are often far
weaker than realized or acknowledged. (Worse yet, sometimes the conclusion is
the SAME as the premise, without this being realized, so you think you have
proved something when you have merely restated a postulate.)

2. Thomas Donaldson asked about the Bekenstein Bound, and Mike Perry referred
him to  Tipler's THE PHYSICS OF IMMORTALITY. For those who don't have that
book or time to find the reference, the Bekenstein Bound (slightly
oversimplified) is an upper limit to the number of possible quantum states of
a system with given mass and volume. Using Planck's constant and the
uncertainty principle, one can show that a "point" in phase space must have a
certain minimum volume; thus the number of "points" in the phase space of the
system is finite, and not greater than the BB. It follows that the total
number of people possible, and the total number of human experiences possible,
must be finite (given a fixed maximum mass and volume for the human brain,
say). Thus, if computing power becomes unbounded (as Tipler belives it will),
then our far-future successors could emulate any person who ever lived or
might have lived, at any or every stage of life.    

However! (Good joke coming up.) If computing power becomes unbounded, it seems
to me (Have I goofed?) that the number of creatable people also becomes
unbounded! The BB is based on PHYSICAL people made of real atoms etc.;
Tipler's resurrected people are computer simulations!  Why should a simulated
person (or successors) be restricted to the limits of a physical person of
fixed mass and volume?

Thomas Donaldson has questioned the "right to life" (or the  value to us) of
an imaginary or potential person, as opposed to an historical person. Here
again we get into questions that are usually approached merely on the basis of
preference or comfort, when what we really need is a rigorously derived basis
of value.

Robert Ettinger
Cryonics Institute
Immortalist Society

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