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Escape
from the universe
http://prospectmagazine.co.uk/article_details.php.6701.html
February 2005
The universe is destined to end. Before it
does, could an advanced civilisation escape via a "wormhole"
into a parallel universe? The idea seems like science fiction, but it is
consistent with the laws of physics and biology. Here's how to do it
Michio Kaku
The author is professor of theoretical physics at
City University of New York. This article is adapted from his book
"Parallel Worlds" (Allen Lane)
The universe is out of
control, in a runaway acceleration. Eventually all intelligent life will
face the final doomthe big freeze. An advanced civilisation must embark
on the ultimate journey: fleeing to a parallel universe.
In Norse mythology, Ragnarok the fate of the godsbegins when the earth
is caught in the vice-like grip of a bone-chilling freeze. The heavens
themselves freeze over, as the gods perish in great battles with evil
serpents and murderous wolves. Eternal darkness settles over the bleak,
frozen land as the sun and moon are both devoured. Odin, the father of
all gods, finally falls to his death, and time itself comes to a halt.
Does this ancient tale foretell our future? Ever since the work of Edwin
Hubble in the 1920s, scientists have known that the universe is
expanding, but most have believed that the expansion was slowing as the
universe aged. In 1998, astronomers at the Lawrence Berkeley National
Laboratory and the Australian National University calculated the
expansion rate by studying dozens of powerful supernova explosions
within distant galaxies, which can light up the entire universe. They
could not believe their own data. Some unknown force was pushing the
galaxies apart, causing the expansion of the universe to accelerate.
Brian Schmidt, one of the group leaders, said, "I was still shaking
my head, but we had checked everything… I was very reluctant to
tell people, because I truly thought that we were going to get
massacred."
Physicists went scrambling back to their blackboards and realised that
some "dark energy" of unknown origin, akin to Einstein's
"cosmological constant," was acting as an anti-gravity force.
Apparently, empty space itself contains enough repulsive dark energy to
blow the universe apart. The more the universe expands, the more dark
energy there is to make it expand even faster, leading to an exponential
runaway mode.
In 2003, this astonishing result was confirmed by the WMAP (Wilkinson
microwave anisotropy probe) satellite. Orbiting at a million miles from
earth, this satellite contains two telescopes capable of detecting the
faint microwave radiation which bathes the universe. It is so sensitive
that it is able to photograph in exquisite detail the afterglow of the
microwave radiation left over from the big bang, which is still
circulating the universe. The WMAP satellite, in effect, gave us
"baby pictures" of the universe when it was a mere 380,000
years old.
The WMAP satellite settled the long-standing question of the age of the
universe: it is officially 13.7bn years old (to within 1 per cent
accuracy). But more remarkably, the data showed that dark energy is not
a fluke, but makes up 73 per cent of the matter and energy of the entire
universe. To deepen the mystery, the data showed that 23 per cent of the
universe consists of "dark matter," a bizarre form of matter
which is invisible but still has weight. Hydrogen and helium make up 4
per cent, while the higher elements, you and I included, make up just
0.03 per cent. Dark energy and most of dark matter do not consist of
atoms, which means that, contrary to what the ancient Greeks believed
and what is taught in every chemistry course, most of the universe is
not made of atoms at all.
As the universe expands, its energy content is diluted and temperatures
eventually plunge to near absolute zero, where even atoms stop moving.
One of the iron laws of physics is the second law of thermodynamics,
which states that in the end everything runs down, that the total
"entropy" (disorder or chaos) in the universe always
increases. This means that iron rusts, our bodies age and crumble,
empires fall, stars exhaust their nuclear fuel, and the universe itself
will run down, as temperatures drop uniformly to near zero.
Charles Darwin was referring to this law when he wrote: "Believing
as I do that man in the distant future will be a far more perfect
creature than he now is, it is an intolerable thought that he and all
other sentient beings are doomed to complete annihilation after such
long-continued slow progress." And one of the most depressing
passages in the English language was written by Bertrand Russell, who
described the "unyielding despair" he felt when contemplating
the distant future: "No fire, no heroism, no intensity of thought
or feeling, can preserve a life beyond the grave… all the labours
of the ages, all the devotion, all the inspiration, all the noonday
brightness of human genius, are destined to extinction in the vast death
of the solar system; and the whole temple of man's achievement must
inevitably be buried beneath the debris of a universe in ruins."
Russell wrote this passage in an era before space travel, so the death
of the sun does not seem so catastrophic todaybut the death of the
entire universe seems inescapable. So on some day in the far future, the
last star will cease to shine, and the universe will be littered with
nuclear debris, dead neutron stars and black holes. Intelligent
civilisations, like homeless people in rags huddled next to dying
campfires, will gather around the last flickering embers of black holes
emitting a faint Hawking radiation.
String theory to the rescue?
Although thermodynamics and cosmology point to the eventual
death of all lifeforms in the universe, there is still one loophole. It
is a law of evolution that, when the environment changes radically, life
must adapt, flee or die. The first alternative seems impossible. The
last is undesirable. This leaves us with one choice: leave the universe.
Although the concept of leaving our dying universe to enter another
seems utterly mad, there is no law of physics forbidding entering a
parallel universe. Einstein's general relativity theory allows for the
existence of "wormholes" or gateways connecting parallel
universes, sometimes called "Einstein-Rosen bridges." But it
is still unknown whether quantum corrections make such a journey
possible or not.
Although once considered a preposterous idea, the concept of the "multiverse"that
our universe coexists with an infinite number of parallel universeshas
recently generated much interest among physicists from several
directions. First, the leading theory consistent with the WMAP data is
the "inflationary" theory, proposed by Alan Guth of MIT in
1979. It postulates a turbo-charged expansion of the universe at the
beginning of time. The inflationary universe idea neatly explains
several stubborn cosmological mysteries, including the flatness and
uniformity of the universe.
But since physicists still do not know what drove this rapid
inflationary process, there remains the chance that it could happen
again, in an endless cycle. This is the chaotic inflationary idea of
Andrei Linde of Stanford University, in which "parent
universes" bud "baby universes" in a continuous,
neverending cycle. Like soap bubbles which split into two smaller
bubbles, universes can constantly sprout from other universes.
But what caused the big bang and drove this inflation? The question
remains unanswered. Since the big bang was so intense, we have to
abandon Einstein's theory of general relativity, which forms the
underlying framework for all of cosmology. Einstein's theory of gravity
breaks down at the instant of the big bang, and hence cannot answer the
deep philosophical and theological questions raised by this event. At
these incredible temperatures, we must incorporate quantum theorythe
other great theory to emerge in the 20th centurywhich governs the
physics of the atom.
Quantum theory and Einstein's relativity theory are opposites. The
former governs the world of the very small, the peculiar subatomic realm
of electrons and quarks. Relativity theory rules the world of the very
largeof black holes and expanding universes. Relativity, therefore, is
not suited to explaining the instant of the big bang, where the universe
was smaller than a subatomic particle. At this moment we would expect
radiation effects to dominate over gravity, and hence we need a quantum
description of gravity. Indeed, one of the greatest challenges facing
physics is to unify these theories into a single, coherent theory of all
the forces in the universe.
Physicists today are groping for this "theory of everything."
Many proposals have been made over the past half century, but all have
been shown to be inconsistent or incomplete. So far, the leadingin fact,
the onlycandidate is string theory.
The latest incarnation of string theory, M-theory, may answer a question
which has dogged advocates of higher dimensions for a century: where are
they? Smoke can expand and fill up an entire room without vanishing into
hyperspace, so higher dimensions, if they exist at all, must be smaller
than an atom. If higher-dimensional space were larger than an atom, then
we should see atoms mysteriously drifting and disappearing into a higher
dimension, which we do not see in the laboratory.
In the older string picture, one had to "curl" or wrap up six
of the ten original dimensions, leaving the four-dimensional universe of
today. These unwanted dimensions were squeezed into a tiny ball (called
a Calabi-Yau manifold) too small to be seen. But M-theory adds a new
twist to this: some of these higher dimensions can be large, or even
infinite, in size. Imagine two parallel sheets of paper. If an ant lived
on each sheet, each would think that its sheet was the entire universe,
unaware that there was another universe close by. In fact, the other
universe would be invisible. Each ant would live out its life oblivious
to the fact that another universe was only a few inches away. Similarly,
our universe may be a membrane floating in 11-dimensional hyperspace,
while we remain oblivious of the parallel universes hovering nearby.
One interesting version of M-theory cosmology is the "ekpyrotic"
(from the Greek for "conflagration") universe, proposed by
Paul Steinhardt, Burt Ovrut and Neil Turok. It assumes that our universe
is a flat, infinite membrane floating in higher-dimensional space. But
occasionally, gravity attracts a nearby membrane. These two parallel
universes race towards each other until they collide, releasing a
colossal amount of energy (the big splat). This explosion creates our
known universe and sends the two parallel universes flying apart in
hyperspace.
Searching for higher dimensions
The intense interest in higher dimensions generated by string
theory has slowly spilled over into the world of experimental physics.
Idle dinner-table chatter is being translated into multimillion-dollar
physics experiments.
At the University of Colorado in Denver, the first experiment was
conducted to search for the presence of a parallel universe, perhaps
only a millimetre away. Physicists searched for tiny deviations from
Newton's inverse square law for gravity. The light from a candle is
diluted as it spreads out, decreasing at the inverse square of the
distance of separation. Similarly, according to Newton's law, gravity
also spreads out over space and decreases in the same way. But in a
four-dimensional universe, there is more room for light or gravity to
spread out, so they decrease at the inverse cube of the distance. Hence,
by searching for tiny deviations from the inverse square law, one may
pick up the presence of the fourth dimension.
Newton's inverse square law is so precise that it can guide our space
probes throughout the solar system. But no one knows if it holds down to
the millimetre level. At present, only null results have been found in
these experiments. Other groups are searching for even smaller
deviations. Physicists at Purdue University in Indiana are trying to
test the law down to the atomic level, using nanotechnology.
Other avenues are also being explored. In 2007, the large hadron
collider (LHC), capable of blasting subatomic particles with a colossal
energy of 14 trillion electron volts (10 trillion times the energy found
in a typical chemical reaction) will be turned on outside Geneva. The
world's largest atom smasher, this huge machine, 27km in circumference,
straddling the French-Swiss border, will probe into places 10,000 times
smaller than a proton. Physicists expect to find an entire zoo of new
subatomic particles not seen since the big bang.
Physicists predict that the LHC may create exotic particles like
mini-black holes and supersymmetric particles, dubbed "sparticles,"
which would provide indirect evidence for string theory. In string
theory, every particle has a super-partner. The partner of the electron
is the "selectron," the partner of the quark is the "squark,"
and so on.
Furthermore, around 2012, the space-based gravity wave detector Lisa
(laser interferometer space antenna) will be sent into orbit. Lisa will
be able to detect the gravitational shockwaves emitted less than a
trillionth of a second after the big bang. It will consist of three
satellites circling the sun, connected by laser beams, making a huge
triangle in space 5m km on each side. Any gravitational wave which
strikes Lisa will disturb the lasers, and this tiny distortion will be
picked up by instruments, signalling the collision of two black holes or
the big bang aftershock itself. Lisa is so sensitiveit can measure
distortions a tenth the diameter of an atomthat it may be able to test
many of the scenarios being proposed for the pre-big bang universe,
including string theory.
Steps to leave the universe
Unfortunately, the energy necessary to manipulate these higher
dimensions, rather than just observe them, is far beyond anything
available to us in the foreseeable future: 1019bn
electron volts, or a quadrillion times the energy of the large hadron
collider. To operate here one needs the technology of a super-advanced
civilisation.
In order to organise a discussion of advanced extraterrestrial
civilisations, astrophysicists often use the classification of Type I,
II and III civilisations introduced by Russian astrophysicist Nikolai
Kardashev in the 1960s, who ranked them by their energy consumption.
One might expect that a Type III civilisation, using the full power of
its unimaginably vast galactic resources, would be able to evade the big
freeze. The bodies of its citizens, for example, might be genetically
altered and their organs replaced by computerised implants, representing
a sophisticated merger of silicon and carbon technologies. But even
these superhuman bodies would not survive the big freeze. This is
because we define intelligence as the ability to process information.
According to physics, all machines, whether they are computers, rockets,
locomotives or steam engines, ultimately depend on extracting energy
from temperature differences: steam engines, for example, work by
extracting energy from boiling water. But information-processing, and
hence intelligence, requires energy supplied by machines and motors,
which will become impossible as temperature differences drop to zero.
According to the laws of physics, in a uniformly cold universe where
temperature differences do not exist, intelligence cannot survive.
But since the big freeze is probably billions to trillions of years
away, there is time for a Type III civilisation to plot the only
strategy consistent with the laws of physics: leaving this universe. To
do this, an advanced civilisation will first have to discover the laws
of quantum gravity, which may or may not turn out to be string theory.
These laws will be crucial in calculating several unknown factors, such
as the stability of wormholes connecting us to a parallel universe, and
how we will know what these parallel worlds will look like. Before
leaping into the unknown, we have to know what is on the other side. But
how do we make the leap? Here are some of the ways.
Find a naturally occurring wormhole
An advanced civilisation which has colonised the galaxy may have
stumbled during its past explorations upon exotic, primordial left-overs
from the big bang. The original expansion was so rapid and explosive
that even tiny wormholes might have been stretched and blown up into
macroscopic size. Wormholes, cosmic strings, negative matter, negative
energy, false vacua and other exotic creatures of physics may be relics
left over from creation.
But if such naturally occurring gateways are not found, then the
civilisation will have to take more complex and demanding steps.
Send a probe through a black hole
Black holes, we now realise, are plentiful; there is one lurking in
the centre of our own milky way galaxy weighing about 3m solar masses.
Probes sent through a black hole may settle some unsolved questions. In
1963, the mathematician Roy Kerr showed that a rapidly spinning black
hole will not collapse into a dot, but rather into a rotating ring,
which is kept from collapsing by centrifugal forces.
All black holes are surrounded by an event horizon, or point of no
return: passing through the event horizon is a one-way trip.
Conceivably, two such black holes would be needed for a return trip. But
to an advanced civilisation fleeing the big freeze, a one-way trip may
be all that is required.
What happens if one falls through the Kerr ring is a matter for debate.
Some believe that the act of entering the wormhole will close it, making
it unstable. And light falling into the black hole would be
blue-shifted, giving rise to the possibility that one might be fried as
one passed into a parallel universe. No one knows for sure, so
experiments must be done. This controversy heated up last year when
Stephen Hawking admitted that he had made a mistake 30 years ago in
betting that black holes gobble up everything, including information.
Perhaps the information is crushed forever by the black hole, or perhaps
it passes into the parallel universe on the other side of the Kerr ring.
Hawking's latest thinking is that information is not totally lost. But
no one believes that the final word on this delicate question has been
spoken.
To gain further data on space-times which are stretched to breaking
point, an advanced civilisation might create a black hole in slow
motion. In 1939, Einstein analysed a rotating mass of stellar debris
which was slowly collapsing under its own gravity. Although Einstein
showed that this rotating mass would not collapse into a black hole, an
advanced civilisation may duplicate this experiment in slow motion by
collecting a swirling mass of neutron stars weighing less than about 3
solar masses and then gradually injecting extra stellar material into
the mass, forcing it to undergo gravitational collapse. Instead of
collapsing into a dot, it will collapse into a ring, and hence allow
scientists to witness the formation of a Kerr black hole in slow motion.
Create negative energy
If Kerr rings prove to be too unstable or lethal, one might also
contemplate opening up wormholes via negative matter/energy. In 1988,
Kip Thorne and his colleagues at the California Institute of Technology
showed that if one had enough negative matter or negative energy, one
could use it to create a transversable wormholeone in which you could
pass freely back and forth between your lab and a distant point in space
(and even time). Negative matter/energy would be sufficient to keep the
throat of the wormhole open for travel.
Unfortunately, no one has ever seen negative matter. In principle, it
should weigh less than nothing and fall up, rather than down. If it
existed when the earth was created, it would have been repelled by the
earth's gravity and drifted off into space.
Negative energy, however, has been seen in the laboratory in the form of
the Casimir effect. Normally, the force between two uncharged parallel
plates should be zero. But if quantum fluctuations outside the plates
are greater than the fluctuations between the plates, a net compression
force will be created. The fluctuations pushing the plates from the
outside are larger than the fluctuations pushing out from within the
plates, so these uncharged plates are attracted to each other.
This was first predicted in 1948 and measured in 1958. However, the
Casimir energy is tinyproportional to the inverse fourth power of the
separation of the plates. To make use of the Casimir effect would
require advanced technology to squeeze these parallel plates to very
small separations. If one were to reshape these parallel plates into a
sphere with a double lining, and use vast amounts of energy to press
these spherical plates together, enough negative energy might be
generated for the interior of the sphere to separate from the rest of
the universe.
Another source of negative energy is laser beams. Pulses of laser energy
contain "squeezed states," which contain negative as well as
positive energy. The problem is separating the negative from the
positive energy within the beam. Although this is theoretically
possible, it is exceedingly difficult. If a sophisticated civilisation
could do this, then powerful laser beams might generate enough negative
energy for the sphere to peel from our universe.
Even black holes have negative energy surrounding them, near their event
horizons. In principle, this may yield vast quantities of negative
energy. However, the technical problems of extracting negative energy so
close to a black hole are extremely tricky.
Create a baby universe
According to inflation, just a few ounces of matter might suffice
to create a baby universe. This is because the positive energy of matter
cancels out the negative energy of gravity. If the universe is closed,
then they cancel out exactly. In some sense, the universe may be a free
lunch, as Guth has emphasised. Strange as it may seem, it requires no
net energy to create an entire universe. Baby universes are in principle
created naturally when a certain region of space-time becomes unstable
and enters a state called the "false vacuum," which
destabilises the fabric of space-time. An advanced civilisation might do
this deliberately by concentrating energy in a single region. This would
require either compressing matter to a density of 1080g/cm3,
or heating it to 1029 degrees kelvin.
To create the fantastic conditions necessary to open up a wormhole with
negative energy or to create a false vacuum with positive energy, one
might need a "cosmic atom-smasher." Physicists are attempting
to build "table-top" accelerators that can, in principle,
attain billions of electron volts on a kitchen table. They have used
powerful laser beams to attain an energy acceleration of 200bn electron
volts per metre, a new record. Progress is rapid, with the energy
growing by a factor of ten every five years. Although technical problems
still prevent a true table-top accelerator, an advanced civilisation has
billions of years to perfect these and other devices.
To reach the Planck energy (1028eV)
with this laser technology would require an atom-smasher ten light years
long, beyond the nearest star, which would be well within the
technological capabilities of a Type III civilisation. Since the vacuum
of empty space is better than any vacuum attainable on the earth, the
beam of subatomic particles may not need light years of tubing to
contain it; it could be fired in empty space. Power stations would have
to be placed along the path in order to pump laser energy into the beam,
and also to focus it.
Another possibility would be to bend the path into a circle so that it
fits within the solar system. Gigantic magnets could be placed on
asteroids to bend and focus the beam in a circular path around the sun.
The magnetic field necessary to bend the beam would be so huge that the
surge of power through the coils might melt them, meaning that they
could only be used once. After the beam had passed, the melted coils
would have to be discarded and replaced in time for the next pass.
Build a laser implosion machine
In principle, it might be possible to create laser beams of
limitless power; the only constraints are the stability of the lasing
material and the energy of the power source. In the lab, terawatt
(trillion watt) lasers are now common, and petawatt (quadrillion watt)
lasers are slowly becoming possible (in comparison, a commercial nuclear
power plant generates only a billion watts of continuous power). One can
even envisage an X-ray laser powered by the output of a hydrogen bomb,
which would carry unimaginable power in its beam. At the Lawrence
Livermore National Laboratory, a battery of lasers is fired radially on
a small pellet of lithium deuteride, the active ingredient of a hydrogen
bomb, in order to tame the power of thermonuclear fusion.
An advanced civilisation might create huge laser stations on the
asteroids and then fire millions of laser beams on to a single point,
creating vast temperatures and pressures unimaginable today.
Send a nanobot to recreate civilisation
If the wormholes created in the previous steps are too small, too
unstable, or the radiation effects too intense, then perhaps we could
send only atom-sized particles through a wormhole. In this case, this
civilisation may embark upon the ultimate solution: passing an
atomic-sized "seed" through the wormhole capable of
regenerating the civilisation on the other side. This process is
commonly found in nature. The seed of an oak tree, for example, is
compact, rugged and designed to survive a long journey and live off the
land. It also contains all the genetic information needed to regenerate
the tree.
An advanced civilisation might want to send enough information through
the wormhole to create a "nanobot," a self-replicating
atomic-sized machine, built with nanotechnology. It would be able to
travel at near the speed of light because it would be only the size of a
molecule. It would land on a barren moon, and then use the raw materials
to create a chemical factory which could create millions of copies of
itself. A horde of these robots would then travel to other moons in
other solar systems and create new chemical factories. This whole
process would be repeated over and over again, making millions upon
millions of copies of the original robot. Starting from a single robot,
there will be a sphere of trillions of such robot probes expanding at
near the speed of light, colonising the entire galaxy.
(This was the basis of the movie 2001, probably the most scientifically
accurate fictional depiction of an encounter with an extraterrestrial
lifeform. Instead of meeting aliens in a flying saucer or the USS
Enterprise, the most realistic possibility is that we will make contact
with a robot probe left on a moon from a passing Type III civilisation.
This was outlined by scientists in the opening minutes of the film, but
Stanley Kubrick cut the interviews from the final edit.)
Next, these robot probes would create huge biotechnology laboratories.
The DNA sequences of the probes' creators would have been carefully
recorded, and the robots would have been designed to inject this
information into incubators, which would then clone the entire species.
An advanced civilisation may also code the personalities and memories of
its inhabitants and inject this into the clones, enabling the entire
race to be reincarnated.
Although seemingly fantastic, this scenario is consistent with the known
laws of physics and biology, and is within the capabilities of a Type
III civilisation. There is nothing in the rules of science to prevent
the regeneration of an advanced civilisation from the molecular level.
For a dying civilisation trapped in a freezing universe, this may be the
last hope.
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