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starship-design: Other Universes I
I just know I am going to regret forwarding this one, but, it was getting
kind
of slow...
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Other Universes I
by John G. Cramer
Alternate View Column AV-02
Keywords: cosmology, bubble, universe, inflation
Published in the September-1984 issue of Analog Science Fiction & Fact
Magazine;
This column was written and submitted 2/10/84 and is copyrighted ©1984,
John G. Cramer. All rights reserved.
No part may be reproduced in any form without the explicit permission of
the author.
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In the fullness of Creation do other universes, other Worlds, exist? Are
there Worlds where history is different? Where triumphant Nazis rule an
aryan-ized planet? Where Napoleon defeated Wellington and went on to
conquer England? Where the Persians beat the Greeks at Marathon, and
Western Civilization never happened? Where Homo-Sap never made it, and
dinosaur decendants, un-extinguished and evolved over 65 million years, are
the dominant life form?
Are there Worlds where the laws of physics are not quite the same? Where
light travels faster? Where gravity is stronger? Where the nuclear binding
force is weaker? Where electrons have a smaller charge? Where the
Uncertainty Principle is less uncertain?
Are there Worlds which are radically different from ours? Where there are
no chemical elements except hydrogen and helium? Where stars never formed?
Where every atom has a nucleus of anti-protons and anti-neutrons orbited by
positrons? Where time runs backwards? Where the Big Bang never Banged at
all, and space is still crunched up into a single geometrical point? Where
the strong, weak, electromagnetic, and gravitational forces are all the
same force?
These are intrinsically fascinating questions. And a few of them have
provided backdrops for some of the best science fiction written. In this
Alternate View column I want to examine an area of contemporary physics,
the "new inflationary scenario" of cosmology, which has something to tell
us about these questions. And in my next (October) Alternate View column,
we will look at the same questions using the "Other Worlds" interpretation
of quantum mechanics, a very different area of physics which also has much
to say about alternate universes.
GUTs cosmology is a recent development which has come from a joining of the
ideas of Big Bang cosmology (the way the universe evolved from the initial
Big Bang) with GUTS or Grand Unification Theories (see The Alternate View,
Analog, July, 1984). In the 1950's, George Gamow and his students developed
the Big Bang model for describing the initial stages and evolution of our
universe. The theory was neglected (and even ridiculed) by the physics
"mainstream" until 1965, when Penzias and Wilson announced the detection of
cosmic 2.7deg. K microwave radiation produced in an early phase of the Big
Bang. Suddenly, the Big Bang model was an experimentally verified fact. It
became the "standard" cosmological model and revolutionized astrophysics.
But soon physicists began to realize that it did not explain everything
about the evolution of the universe. It became obvious that there were
problems built into the description.
These problems have become known as:
(1) The Problem of Matter: Why is there more matter than antimatter in the
universe?
(2) The Problem of Uniformity: Why is the universe so homogeneous, when its
parts went out of speed-of-light contact very early in the Big Bang and are
only "recently" rejoined?
(3) The Problem of Flatness: Why does the universe have just the right
density of matter in its volume to be precisely on the borderline between
re-collapse and continuous expansion?
(4) The Problem of Monopoles: Why aren't there more magnetic monopoles
around, when the standard model predicts that there should be an enormous
number of them?
A few decades ago these would all have been considered metaphysical
questions, not proper subjects for physical investigations. But
contemporary physicists, emboldened by the recent successes in particle
physics, have found ways of approaching them. And they have made impressive
progress toward answering them through some new ideas arising from the
Grand Unification Theories mentioned above.
The Big Bang + GUTs scenario goes something like this: there are two kinds
of space, which we might call H-space and N-space. Here N stands for
"normal" and H refers to Higgs, the Scottish physicist who first suggested
the possibility that H-space, also called "the false vacuum" might exist.
We live in N-space. We have never experienced H-space directly, but recent
work in particle physics suggests that N-space could be converted to
H-space by pumping enough energy into a small enough region. And perhaps
there is also a tiny region of H-space at the core of each magnetic
monopole, if such particles exist in our universe.
In N-space the three strongest fundamental forces of the universe (the
strong, weak, and electromagnetic interactions) can easily be
distinguished. They have very different strengths, and their change with
distance is very different. But in H-space these forces are all the same
and cannot not be distinguished from one another. In H-space quarks,
electrons, neutrinos, and photons are all the same particles with nothing
to distinguish them.
Immediately after the Big Bang there was so much energy in such a small
volume that all space was H-space. During this period, the universe
expanded far faster than its present expansion rate. But as the universe
expanded and more volume became available for the same amount of energy,
the energy/volume ratio of space fell. About one millionth of a second
after the start of the Big Bang, when the universe had expanded to about
the size of a grapefruit, the energy/volume ratio had fallen to a low
enough value that N-space became possible and H-space became
"supersaturated". Regions of N-space begin to "precipitate out". As such
regions of N-space appeared, the three forces within these regions "split"
from one another, becoming different forces rather than the same force and
the corresponding particles (hadrons, leptons, photons) also became
distinguishable.
This "splitting" is like the change from one state of matter to another,
for example, boiling water changing from liquid to steam. But in this case
it is space itself which "boiled". And, as you might expect of a boiling
medium, "bubbles" formed. But the bubbles which form when space itself
boils are not our ordinary bubbles with gas inside and liquid outside.
These bubbles have N-space inside and H-space outside. Our universe just is
one of these bubbles. We have experienced only N-space because we are stuck
inside it. And there should be very many N-space bubbles in the H-space
"sea".
The boiling of space, the conversion of H-space to N-space, frees a truly
enormous amount of energy. This energy ends up in the walls of each bubble,
causing the walls to move outward from the central region at nearly the
speed of light. So each bubble-universe expands, as ours seems to still be
doing some 4 billion years after the Big Bang.
This revised version of the Big Bang model is called "the New Inflationary
Scenario". It seems to provides solutions to all of the problems mentioned
above of the "standard" Big Bang model. There is an excess of matter over
antimatter in our universe because a "CP violation" occurred during the
boiling phase, producing about .00000002% more protons than antiprotons
(and .00000002% more electrons than positrons). The vast majority of the
matter and antimatter particles from the Big Bang paired off and
annihilated, but this small residue remained to become the protons and
electrons of which our world is made. Uniformity is accounted for because
the chunk of the Big Bang forming our universe was small enough and
expanded fast enough. Flatness comes directly from the way in which the
bubble expands, keeping the balance of matter and expansion speed of the
universe precisely at the balance point between infinite expansion and
eventual recontraction. The monopole number is reduced because the
monopoles from the Big Bang have a large number of bubble-universes in
which to end up, not just one. There is even some reason to suspect that
each bubble-universe contains exactly one magnetic monopole, which is the
"nucleating agent" that caused it to "precipitate" from H-space, like the
dust particle at the heart of every raindrop.
So there are other Worlds! In the new inflationary scenario there are a
very very many other Worlds. But these Worlds are not easy to reach from
here. In the first place, there is just enough mass in our universe to
cause our local space to exactly close on itself. In effect we are barely
trapped in a rapidly expanding black hole. And there seems no way of
leaving our local space to enter the sea of H-space "outside". Perhaps that
is just as well, because the surrounding H-space is probably not compatible
with body chemistry (or with life). On inaccessible other shores of the
H-space sea will be other Worlds, islands of N-space that came from the
same Big Bang which produced ours. They should be similar to our World, but
perhaps they are also different.
But in what way can these other bubble-universes be different from ours? In
N-space the laws of physics (as we know them) should apply. How then,
without changing the laws of physics, might these other Worlds be
different? First, there is no particular reason why the CP violation
mentioned above should always lead to an excess of matter over antimatter.
So perhaps some of the other Worlds are all antimatter. Second, no one
really understands why time in our World runs in the direction it does. So
perhaps some of the other Worlds would have time running in the opposite
direction. Third, when the bubbles formed, they would probably have many
different sizes, each with a different amount of mass-energy trapped
inside. What would that do?
A relatively untested physical idea called Mach's Principle, first proposed
by Ernst Mach (known for the Mach Number of supersonic flight) gives us a
way of answering this question. It asserts that the force of inertia, which
we experience as resistance to acceleration, is the result of the
gravitational pulls of all the other masses in the universe (the Sun, other
stars, and even distant galaxies). If Mach's Principle can be applied to an
individual bubble-universe, then the inertia which an object has (which we
call its inertial mass) should depend directly on how much mass-energy is
contained in that bubble-universe. The gravitational mass (how much pull
due to gravity a massive object experiences) should not depend on this. The
net result is that an object in another bubble-universe would, have a
different ratio of gravitational to inertial mass.
This would change the masses of protons, electrons, etc. in all of the laws
of physics in which the mass in the formula means reaction to inertia (as
it usually does in atomic and nuclear physics). Sizes of atoms, positions
of orbiting electron shells, chemical bonds linking one atom to another,
nuclear structure, and synthesis in supernovae of heavier nuclei from
lighter nuclei would all be altered.
Suppose that we could build a machine, a "Universe-swapper" by which could
transport a Voyager safely across the H-space sea from our World to one of
its bubble-universe siblings. What would we find? If the universe visited
was filled with antimatter the Voyager would probably have an unpleasant
time. All of the matter sent across would be annihilated on contact with
with antimatter on the other side. Our Voyager would have to remain in the
hardest vacuum to avoid a lethal dose of radiation from the random anti-gas
molecules of deep space annihilating on contact with his vehicle or space
suit.
To natives of the time-reversed universes, their universe would appear to
be contracting to a Big Crunch rather than expanding from a Big Bang. The
light from distant stars (if any) would be blue shifted rather than red
shifted, making the sky very bright and perhaps intolerably hot. Our
Voyager, if he retained his own time direction, would perceive the sibling
universe as running backwards. He would watch the Second Law of
Thermodynamics operating in reverse: water would run uphill, the dead would
come to life, food would be produced by un-eating it so that it could be
converted into plants and animals. Or perhaps our Voyager would be swept
along with the time direction of the sibling universe. In that case, he
would find on his return to our universe that he had returned before the
time of his departure. This, as most SF readers already know, can produce
some interesting and paradoxical situations.
But what about the Worlds containing normal matter and having time
proceeding in the proper direction? If Mach's principle works the inertial
masses of objects will be altered, effectively changing the laws of physics
in these Worlds. In a broad class of such universes, no stars or galaxies
would have formed; in another group there would be stars and galaxies, but
no synthesis of elements heavier than helium; in another group there would
be stars, galaxies, and the usual chemical elements, but no planets; and in
a another group there would be planets, but none that would support life.
In only an extremely small fraction of the universes would life be
possible. And it is difficult to say how much variation in the laws of
chemistry would be permitted after the physics worked out to produce
life-supporting planets. Clearly the carbon chemical bond is a subtle
prerequisite to life-as-we-know-it which would not tolerate much tinkering.
So our Voyager, upon entering a sibling bubble-universe, might find that
his body chemistry had gone bonkers, perhaps fatally. And we must also
remember that the operation of solid-state electronics depends on the
accidental placement of a "gap" between the atomic states of semiconductor
materials like silicon and germanium. Our universe-swapper device and its
recording equipment should probably be built with old-fashioned tubes
rather than solid-state electronics in order to be "universe-tolerant" and
behave itself after reaching its destination.
My friend Gene Wolfe has suggested that if our own universe is not all of
Creation but only one bubble out of many in the stream of Time, then
calling it "The Universe" is no longer sufficient. We need a Name for it.
He suggested "Malkuth", which is the Kabbalist name for "world". But I find
Malkuth rather unappealing; it sounds too much like "uncouth" and would
give completely the wrong impression of our Universe to an outsider.
So, in order to correct this Name deficiency, I hereby announce the 1984
ANALOG Name-the-Universe Competition!! The winner will receive a free one
year subscription to this magazine and will, in addition, achieve the true
immortality of having chosen the proper name of an important natural
object, in this case the Universe in which we live. Send your entries (one
per letter please) to me in care of ANALOG, 380 Lexington Avenue, New York,
NY 10017. Include your name and address, your suggestion for the Name of
the Universe, and a brief statement of why you feel the Name is
appropriate. The winning Name and the name of the winner will be announced
in a later AV column (probably in early 1985).
REFERENCES:
D. N. Schramm, Physics Today 36 #4, 27 (April, 1983).
A. H. Guth, Physical Review D 23, 347 (1981).
A. Alberecht and P. J. Steinhardt, Physical Review Letters 48, 1220 (1982).
FIGURE CAPTION:
Bubbles in the Big Bang: some "bubbles" may form antimatter universes; some
may form universes in which time runs backwards, some may resemble our
universe but with altered physical laws.
Lee