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C00002 00002	long[w82,jmc]		the long range future
C00009 00003	How long can humanity survive?
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long[w82,jmc]		the long range future

1. In the long run we are all dead.  However, humanity can last probably
10↑30 years if we are economical with suns.
This makes the present duration of the universe amount to less than
a second in the life of a person.  Nevertheless, the prospect of the
 eventual end of
humanity has psychological effects, no matter how far off
the end is - just as learning about death has psychological effects
on even young children.  People have to adjust themselves to the
prospect of the end of humanity just as
 a person has to
adjust psychologically to the fact of his own death.

Presumably the prospect of the end of humanity spoils some of the
psychological adjustments to individual death.  The new adjustment
must say that humanity can have an interesting life, and that's better
than nothing.

2. Another worry is that life may get dull.  The possibilities of doing
something new may be exhausted long before the physical possibilities of
human life are used up.

3. However, we are but babies compared to the time in store for us
and concentration on the next thousand or even hundred years is
more appropriate for most of our thoughts than looking even a
million years ahead.

4. Indeed from the point of view of policy, perhaps 50 years is the
limit.  Certainly we don't reproach the people of 1882 for not
having solved our problems for us, and our descendants 100 years
from now will not reproach us.  Instead they will marvel at our
ability to endure the primitive conditions - especially the
primitive intellectual conditions - of our lives.  To elaborate this
point slightly, I believe they will recognize that our material
conditions, while far below theirs, are on the whole satisfactory
for most people.  However, our understanding of our possibilities
is scarcely if at all better than that of 1882 and may be worse.

5. These reflections on humanity's long term future are part of
an attempt to improve our psychological condition by giving a
realistic view of human possibilities.

6. First, humanity will be able to expand beyond throughout the
solar system and beyond quite soon.  Indeed the science for
this already exists and the technology can be developed at a
cost of a few hundred billion dollars spread over as many
years as we decide to take.  The big step is to be able to
ship large amounts of material to low earth orbit, and there
are several proposals for doing this with rockets for delicate
things and with various kinds of guns for bulk material.
Beyond low earth orbit, low thrust high specific impulse
rockets such as electrical rockets can be used.

7. As O'Neill, Dyson and others have contended, the most habitable
part of the solar system is interplanetary space itself because of
the ease of collecting energy and building structures and also
because of the freedom of motion provided by the absence of gravity
once we get used to it.

8. Life in interplanetary space may or may not become boring.
I fear that humans require trivial variety but maybe artificial
variety will do.

9. We must take into account the fact that we are recently evolved
from ape like animals and are only socially evolved from primitive
hunters and gatherers (as shown by the fact that primitive hunters
and gatherers can readily adapt to modern society).

10. What we would like our motivations to be must be distinguished
from what they are.  We can re-arrange our lives, and we habitually
do, in order to re-arrange our motivations.  The struggles between
impulse and conscience emphasized in traditional religious thinking
express real problems.  The modern ideology giving priority to
impulse is just another ideology, and the old-fashioned ideology
that took moral questions more seriously  is better.  However,
religion includes false beliefs.  The acceptance of morality
cannot successfully be based on factual belief.  Neither the
hypothesis of God nor the facts of evolution force morality
by argument.  There has to be at least one decision.  If this
decision is sufficiently general, then other decisions follow
from it.
How long can humanity survive?

	The universe contains approximately 10↑80 particles.
The annihilation of a proton produces  10↑(-10) joules of energy,
and a person uses about 100 watts, i.e. joules per second.  Therefore,
a person could survive  10↑68 seconds or 3 x 10↑60 years using up all
the mass of the universe.  This is an upper limit of course, although
we could imagine a human personality embedded in an ultimate micro-computer.
using say 10↑(-15) watts, thus extending the lifetime to 10↑77 years.
Going the other way, 10↑9 people could last a mere 10↑51 years or
10↑40 years if they had only one of the 10↑11 galaxies to convert 
into energy.

	The best way to convert mass into energy is to lower it into
the gravitational field of a black hole.  However, any gravitational
system in orbital motion radiates energy in gravitational waves, and
this radiative energy loss would probably exceed the consumption by
a person or maybe even a civilization.  It seems a matter of invention
to determine the most efficient scheme for making a galaxy or even
a substantial part of the universe into an economical converter of
mass into useful energy.

	For this reason, I'll give the doomsayers another factor
of 10↑10 and ask them to admit that an economical human race can
surely last 10↑30 years.  Now this ratio of 10↑10 is that of a
tenth of a second to a lifetime.  However, in terms of what any
twentieth century person knows about occupying time, there is no
perceptible difference between  10↑30 and 10↑40 years.  Perhaps
it will make a large difference to our much smarter and knowledgable
remote descendants.

	Of course, if we refuse to use new technology the lifetime
of our civilization will be much shorter.  The sun will remain on
the main sequence for only a few times 10↑9 years and then will turn
into a red giant and engulf the earth unless we prevent it somehow.
The uranium and thorium in the earth's crust could provide energy
for a present energy level civilization for only a few times 10↑9
years even assuming we use it all in breeder reactors.  In a few
times 10↑10 years, it will have mostly decayed anyway.  To return
to shorter run considerations, if we simply park junked cars, in
a mere 37,000 years the country would be completely covered with
junked cars.