The late Carl Sagan once asked this question, “What does it mean for a civilization to be a million years old? We have
had radio telescopes and spaceships for a few decades; our technical civilization is a few hundred years old… an
advanced civilization millions of years old is as much beyond us as we are beyond a bush baby or a macaque.”
Although any conjecture about such advanced civilizations is a matter of sheer speculation, one can still use the laws
of physics to place upper and lower limits on these civilizations. In particular, now that the laws of quantum field
theory, general relativity, thermodynamics, etc. are fairly well-established, physics can impose broad physical bounds
which constrain the parameters of these civilizations.
This question is no longer a matter of idle speculation. Soon, humanity may face an existential shock as the current
list of a dozen Jupiter-sized extra-solar planets swells to hundreds of earth-sized planets, almost identical twins of
our celestial homeland. This may usher in a new era in our relationship with the universe: we will never see the night
sky in the same way ever again, realizing that scientists may eventually compile an encyclopedia identifying the precise
co-ordinates of perhaps hundreds of earth-like planets.
had radio telescopes and spaceships for a few decades; our technical civilization is a few hundred years old… an
advanced civilization millions of years old is as much beyond us as we are beyond a bush baby or a macaque.”
Although any conjecture about such advanced civilizations is a matter of sheer speculation, one can still use the laws
of physics to place upper and lower limits on these civilizations. In particular, now that the laws of quantum field
theory, general relativity, thermodynamics, etc. are fairly well-established, physics can impose broad physical bounds
which constrain the parameters of these civilizations.
This question is no longer a matter of idle speculation. Soon, humanity may face an existential shock as the current
list of a dozen Jupiter-sized extra-solar planets swells to hundreds of earth-sized planets, almost identical twins of
our celestial homeland. This may usher in a new era in our relationship with the universe: we will never see the night
sky in the same way ever again, realizing that scientists may eventually compile an encyclopedia identifying the precise
co-ordinates of perhaps hundreds of earth-like planets.
THE PHYSICS OF EXTRATERRESTRIAL CIVILIZATIONS by Dr. Michio Kaku
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DR. MICHIO KAKU is a
theoretical physicist, best-
selling author, and
popularizer of science. He’
s the co-founder of string
field theory (a branch of
string theory), and
continues Einstein’s
search to unite the four
fundamental forces of
nature into one unified
theory.
Publications
Michio’s new book, Physics
of the Impossible: A
Scientific Exploration of the
World of Phasers, Force
Fields, Teleportation, and
Time Travel has already
hit the NY Times
Bestseller List.
Other Books Include:
Parallel Worlds - 2006
Einstein’s Cosmos - 2005
Visions - 1999
Beyond Einstein - 1995
Hyperspace - 1994
Popularizer of Science
He has appeared on
television (Discovery,
BBC, ABC, Science
Channel, and CNN to
name a few), written for
popular science
publications like Discover,
Wired, and New Scientist,
been featured in
documentaries like Me &
Isaac Newton, and hosted
many of his own including
BBC’s recent series on
Time.
Academics
Theoretical Physicist — Dr.
Michio Kaku is the co-
creator of string field
theory, a branch of string
theory. He received a B.S.
(summa cum laude) from
Harvard University in
1968 where he came first
in his physics class. He
went on to the Berkeley
Radiation Laboratory at
the University of
California, Berkeley and
received a Ph.D. in 1972.
In 1973, he held a
lectureship at Princeton
University.
Michio continues
Einstein’s search for a
“Theory of Everything,”
seeking to unify the four
fundamental forces of the
universe—the strong
force, the weak force,
gravity and
electromagnetism.
He is the author of
several scholarly, Ph.D.
level textbooks and has
had more than 70 articles
published in physics
journals, covering topics
such as superstring
theory, supergravity,
supersymmetry, and
hadronic physics.
Professor of Physics — He
holds the Henry Semat
Chair and Professorship
in theoretical physics at
the City College of New
York, where he has
taught for over 25 years.
He has also been a
visiting professor at the
Institute for Advanced
Study at Princeton, as well
as New York University
(NYU).
His website is
mkaku.org/home/
His email is
mkaku@aol.com
theoretical physicist, best-
selling author, and
popularizer of science. He’
s the co-founder of string
field theory (a branch of
string theory), and
continues Einstein’s
search to unite the four
fundamental forces of
nature into one unified
theory.
Publications
Michio’s new book, Physics
of the Impossible: A
Scientific Exploration of the
World of Phasers, Force
Fields, Teleportation, and
Time Travel has already
hit the NY Times
Bestseller List.
Other Books Include:
Parallel Worlds - 2006
Einstein’s Cosmos - 2005
Visions - 1999
Beyond Einstein - 1995
Hyperspace - 1994
Popularizer of Science
He has appeared on
television (Discovery,
BBC, ABC, Science
Channel, and CNN to
name a few), written for
popular science
publications like Discover,
Wired, and New Scientist,
been featured in
documentaries like Me &
Isaac Newton, and hosted
many of his own including
BBC’s recent series on
Time.
Academics
Theoretical Physicist — Dr.
Michio Kaku is the co-
creator of string field
theory, a branch of string
theory. He received a B.S.
(summa cum laude) from
Harvard University in
1968 where he came first
in his physics class. He
went on to the Berkeley
Radiation Laboratory at
the University of
California, Berkeley and
received a Ph.D. in 1972.
In 1973, he held a
lectureship at Princeton
University.
Michio continues
Einstein’s search for a
“Theory of Everything,”
seeking to unify the four
fundamental forces of the
universe—the strong
force, the weak force,
gravity and
electromagnetism.
He is the author of
several scholarly, Ph.D.
level textbooks and has
had more than 70 articles
published in physics
journals, covering topics
such as superstring
theory, supergravity,
supersymmetry, and
hadronic physics.
Professor of Physics — He
holds the Henry Semat
Chair and Professorship
in theoretical physics at
the City College of New
York, where he has
taught for over 25 years.
He has also been a
visiting professor at the
Institute for Advanced
Study at Princeton, as well
as New York University
(NYU).
His website is
mkaku.org/home/
His email is
mkaku@aol.com
| Copyright © 2009 JFS |
Today, every few weeks brings news of a new
Jupiter-sized extra-solar planet being discovered, the
latest being about 15 light years away orbiting around
the star Gliese 876. The most spectacular of these
findings was photographed by the Hubble Space
Telescope, which captured breathtaking photos of a
planet 450 light years away being sling-shot into
space by a double-star system.
But the best is yet to come. Early in the next decade,
scientists will launch a new kind of telescope, the
interferome try space telescope, which uses the
interference of light beams to enhance the resolving
power of telescopes.
For example, the Space Interferometry Mission (SIM),
to be launched early in the next decade, consists of
multiple telescopes placed along a 30 foot structure.
With an unprecedented resolution approaching the
physical limits of optics, the SIM is so sensitive that it
almost defies belief: orbiting the earth, it can detect
the motion of a lantern being waved by an astronaut
on Mars!
Jupiter-sized extra-solar planet being discovered, the
latest being about 15 light years away orbiting around
the star Gliese 876. The most spectacular of these
findings was photographed by the Hubble Space
Telescope, which captured breathtaking photos of a
planet 450 light years away being sling-shot into
space by a double-star system.
But the best is yet to come. Early in the next decade,
scientists will launch a new kind of telescope, the
interferome try space telescope, which uses the
interference of light beams to enhance the resolving
power of telescopes.
For example, the Space Interferometry Mission (SIM),
to be launched early in the next decade, consists of
multiple telescopes placed along a 30 foot structure.
With an unprecedented resolution approaching the
physical limits of optics, the SIM is so sensitive that it
almost defies belief: orbiting the earth, it can detect
the motion of a lantern being waved by an astronaut
on Mars!
The SIM, in turn, will pave the way for the Terrestrial Planet Finder, to be launched late in the next decade, which
should identify even more earth-like planets. It will scan the brightest 1,000 stars within 50 light years of the earth
and will focus on the 50 to 100 brightest planetary systems.
All this, in turn, will stimulate an active effort to determine if any of them harbor life, perhaps some with civilizations
more advanced than ours.
Although it is impossible to predict the precise features of such advanced civilizations, their broad outlines can be
analyzed using the laws of physics. No matter how many millions of years separate us from them, they still must obey
the iron laws of physics, which are now advanced enough to explain everything from sub-atomic particles to the large-
scale structure of the universe, through a staggering 43 orders of magnitude.
Physics of Type I, II, and III Civilizations
Specifically, we can rank civilizations by their energy consumption, using the following principles:
1) The laws of thermodynamics. Even an advanced civilization is bound by the laws of thermodynamics, especially the
Second Law, and can hence be ranked by the energy at their disposal.
2) The laws of stable matter. Baryonic matter (e.g. based on protons and neutrons) tends to clump into three large
groupings: planets, stars and galaxies. (This is a well-defined by product of stellar and galactic evolution,
thermonuclear fusion, etc.) Thus, their energy will also be based on three distinct types, and this places upper limits
on their rate of energy consumption.
3) The laws of planetary evolution. Any advanced civilization must grow in energy consumption faster than the
frequency of life-threatening catastrophes (e.g. meteor impacts, ice ages, supernovas, etc.). If they grow any slower,
they are doomed to extinction. This places mathematical lower limits on the rate of growth of these civilizations.
In a seminal paper published in 1964 in the Journal of Soviet Astronomy, Russian astrophysicist Nicolai Kardashev
theorized that advanced civilizations must therefore be grouped according to three types: Type I, II, and III, which
have mastered planetary, stellar and galactic forms of energy, respectively. He calculated that the energy consumption
of these three types of civilization would be separated by a factor of many billions. But how long will it take to reach
Type II and III status?
Shorter than most realize
Berkeley astronomer Don Goldsmith reminds us that the earth receives about one billionth of the suns energy, and
that humans utilize about one millionth of that. So we consume about one million billionth of the suns total energy. At
present, our entire planetary energy production is about 10 billion billion ergs per second. But our energy growth is
rising exponentially, and hence we can calculate how long it will take to rise to Type II or III status.
Goldsmith says, “Look how far we have come in energy uses once we figured out how to manipulate energy, how to
get fossil fuels really going, and how to create electrical power from hydropower, and so forth; we’ve come up in
energy uses in a remarkable amount in just a couple of centuries compared to billions of years our planet has been
here … and this same sort of thing may apply to other civilizations.”
Physicist Freeman Dyson of the Institute for Advanced Study estimates that, within 200 years or so, we should attain
Type I status. In fact, growing at a modest rate of 1% per year, Kardashev estimated that it would take only 3,200
years to reach Type II status, and 5,800 years to reach Type III status. Living in a Type I,II, or III civilization
For example, a Type I civilization is a truly planetary one, which has mastered most forms of planetary energy. Their
energy output may be on the order of thousands to millions of times our current planetary output. Mark Twain once
said, ”Everyone complains about the weather, but no one does anything about it.“ This may change with a Type I
civilization, which has enough energy to modify the weather. They also have enough energy to alter the course of
earthquakes, volcanoes, and build cities on their oceans.
Currently, our energy output qualifies us for Type 0 status. We derive our energy not from harnessing global forces,
but by burning dead plants (e.g. oil and coal). But already, we can see the seeds of a Type I civilization. We see the
beginning of a planetary language (English), a planetary communication system (the Internet), a planetary economy
(the forging of the European Union), and even the beginnings of a planetary culture (via mass media, TV, rock music,
and Hollywood films).
By definition, an advanced civilization must grow faster than the frequency of life-threatening catastrophes. Since
large meteor and comet impacts take place once every few thousand years, a Type I civilization must master space
travel to deflect space debris within that time frame, which should not be much of a problem. Ice ages may take place
on a time scale of tens of thousands of years, so a Type I civilization must learn to modify the weather within that
time frame.
Artificial and internal catastrophes must also be negotiated. But the problem of global pollution is only a mortal threat
for a Type 0 civilization; a Type I civilization has lived for several millennia as a planetary civilization, necessarily
achieving ecological planetary balance. Internal problems like wars do pose a serious recurring threat, but they have
thousands of years in which to solve racial, national, and sectarian conflicts.
Eventually, after several thousand years, a Type I civilization will exhaust the power of a planet, and will derive their
energy by consuming the entire output of their suns energy, or roughly a billion trillion trillion ergs per second.
With their energy output comparable to that of a small star, they should be visible from space. Dyson has proposed
that a Type II civilization may even build a gigantic sphere around their star to more efficiently utilize its total energy
output. Even if they try to conceal their existence, they must, by the Second Law of Thermodynamics, emit waste
heat. From outer space, their planet may glow like a Christmas tree ornament. Dyson has even proposed looking
specifically for infrared emissions (rather than radio and TV) to identify these Type II civilizations.
Perhaps the only serious threat to a Type II civilization would be a nearby supernova explosion, whose sudden
eruption could scorch their planet in a withering blast of X-rays, killing all life forms. Thus, perhaps the most
interesting civilization is a Type III civilization, for it is truly immortal. They have exhausted the power of a single star,
and have reached for other star systems. No natural catastrophe known to science is capable of destroying a Type III
civilization.
Faced with a neighboring supernova, it would have several alternatives, such as altering the evolution of dying red
giant star which is about to explode, or leaving this particular star system and terraforming a nearby planetary
system.
However, there are roadblocks to an emerging Type III civilization. Eventually, it bumps up against another iron law of
physics, the theory of relativity. Dyson estimates that this may delay the transition to a Type III civilization by
perhaps millions of years.
But even with the light barrier, there are a number of ways of expanding at near-light velocities. For example, the
ultimate measure of a rockets capability is measured by something called “specific impulse” (defined as the product of
the thrust and the duration, measured in units of seconds). Chemical rockets can attain specific impulses of several
hundred to several thousand seconds. Ion engines can attain specific impulses of tens of thousands of seconds. But
to attain near-light speed velocity, one has to achieve specific impulse of about 30 million seconds, which is far
beyond our current capability, but not that of a Type III civilization. A variety of propulsion systems would be available
for sub-light speed probes (such as ram-jet fusion engines, photonic engines, etc.)
How to Explore the Galaxy
Because distances between stars are so vast, and the number of unsuitable, lifeless solar systems so large, a Type III
civilization would be faced with the next question: what is the mathematically most efficient way of exploring the
hundreds of billions of stars in the galaxy?
In science fiction, the search for inhabitable worlds has been immortalized on TV by heroic captains boldly
commanding a lone star ship, or as the murderous Borg, a Type III civilization which absorbs lower Type II civilization
(such as the Federation). However, the most mathematically efficient method to explore space is far less glamorous:
to send fleets of “Von Neumann probes” throughout the galaxy (named after John Von Neumann, who established
the mathematical laws of self-replicating systems).
A Von Neumann probe is a robot designed to reach distant star systems and create factories which will reproduce
copies themselves by the thousands. A dead moon rather than a planet makes the ideal destination for Von Neumann
probes, since they can easily land and take off from these moons, and also because these moons have no erosion.
These probes would live off the land, using naturally occurring deposits of iron, nickel, etc. to create the raw
ingredients to build a robot factory. They would create thousands of copies of themselves, which would then scatter
and search for other star systems.
Similar to a virus colonizing a body many times its size, eventually there would be a sphere of trillions of Von
Neumann probes expanding in all directions, increasing at a fraction of the speed of light. In this fashion, even a
galaxy 100,000 light years across may be completely analyzed within, say, a half million years.
If a Von Neumann probe only finds evidence of primitive life (such as an unstable, savage Type 0 civilization) they
might simply lie dormant on the moon, silently waiting for the Type 0 civilization to evolve into a stable Type I
civilization. After waiting quietly for several millennia, they may be activated when the emerging Type I civilization is
advanced enough to set up a lunar colony. Physicist Paul Davies of the University of Adelaide has even raised the
possibility of a Von Neumann probe resting on our own moon, left over from a previous visitation in our system
aeons ago.
(If this sounds a bit familiar, that’s because it was the basis of the film, 2001. Originally, Stanley Kubrick began the
film with a series of scientists explaining how probes like these would be the most efficient method of exploring outer
space. Unfortunately, at the last minute, Kubrick cut the opening segment from his film, and these monoliths became
almost mystical entities)
New Developments
Since Kardashev gave the original ranking of civilizations, there have been many scientific developments which refine
and extend his original analysis, such as recent developments in nanotechnology, biotechnology, quantum physics,
etc.
For example, nanotechnology may facilitate the development of Von Neumann probes. As physicist Richard Feynman
observed in his seminal essay, “There’s Plenty of Room at the Bottom,” there is nothing in the laws of physics which
prevents building armies of molecular-sized machines. At present, scientists have already built atomic-sized
curiosities, such as an atomic abacus with Buckyballs and an atomic guitar with strings about 100 atoms across.
Paul Davies speculates that a space-faring civilization could use nanotechnology to build miniature probes to explore
the galaxy, perhaps no bigger than your palm. Davies says, “The tiny probes I’m talking about will be so
inconspicuous that it’s no surprise that we haven’t come across one. It’s not the sort of thing that you’re going to
trip over in your back yard. So if that is the way technology develops, namely, smaller, faster, cheaper and if other
civilizations have gone this route, then we could be surrounded by surveillance devices.”
Furthermore, the development of biotechnology has opened entirely new possibilities. These probes may act as life-
forms, reproducing their genetic information, mutating and evolving at each stage of reproduction to enhance their
capabilities, and may have artificial intelligence to accelerate their search.
Also, information theory modifies the original Kardashev analysis. The current SETI project only scans a few
frequencies of radio and TV emissions sent by a Type 0 civilization, but perhaps not an advanced civilization. Because
of the enormous static found in deep space, broadcasting on a single frequency presents a serious source of error.
Instead of putting all your eggs in one basket, a more efficient system is to break up the message and smear it out
over all frequencies (e.g. via Fourier like transform) and then reassemble the signal only at the other end. In this way,
even if certain frequencies are disrupted by static, enough of the message will survive to accurately reassemble the
message via error correction routines. However, any Type 0 civilization listening in on the message on one frequency
band would only hear nonsense. In other words, our galaxy could be teeming with messages from various Type II
and III civilizations, but our Type 0 radio telescopes would only hear gibberish.
Lastly, there is also the possibility that a Type II or Type III civilization might be able to reach the fabled Planck energy
with their machines (10^19 billion electron volts). This is energy is a quadrillion times larger than our most powerful
atom smasher. This energy, as fantastic as it may seem, is (by definition) within the range of a Type II or III
civilization.
The Planck energy only occurs at the center of black holes and the instant of the Big Bang. But with recent advances
in quantum gravity and superstring theory, there is renewed interest among physicists about energies so vast that
quantum effects rip apart the fabric of space and time. Although it is by no means certain that quantum physics
allows for stable wormholes, this raises the remote possibility that a sufficiently advanced civilizations may be able to
move via holes in space, like Alice’s Looking Glass. And if these civilizations can successfully navigate through stable
wormholes, then attaining a specific impulse of a million seconds is no longer a problem. They merely take a short-cut
through the galaxy. This would greatly cut down the transition between a Type II and Type III civilization.
Second, the ability to tear holes in space and time may come in handy one day. Astronomers, analyzing light from
distant supernovas, have concluded recently that the universe may be accelerating, rather than slowing down. If this
is true, there may be an anti-gravity force (perhaps Einstein’s cosmological constant) which is counteracting the
gravitational attraction of distant galaxies. But this also means that the universe might expand forever in a Big Chill,
until temperatures approach near-absolute zero. Several papers have recently laid out what such a dismal universe
may look like. It will be a pitiful sight: any civilization which survives will be desperately huddled next to the dying
embers of fading neutron stars and black holes. All intelligent life must die when the universe dies.
Contemplating the death of the sun, the philosopher Bertrand Russel once wrote perhaps the most depressing
paragraph in the English language: “…All the labors 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 Mans achievement must inevitably be buried beneath the debris of a universe in ruins…”
Today, we realize that sufficiently powerful rockets may spare us from the death of our sun 5 billion years from now,
when the oceans will boil and the mountains will melt. But how do we escape the death of the universe itself?
Astronomer John Barrows of the University of Sussex writes, “Suppose that we extend the classification upwards.
Members of these hypothetical civilizations of Type IV, V, VI, … and so on, would be able to manipulate the structures
in the universe on larger and larger scales, encompassing groups of galaxies, clusters, and superclusters of galaxies.”
Civilizations beyond Type III may have enough energy to escape our dying universe via holes in space.
Lastly, physicist Alan Guth of MIT, one of the originators of the inflationary universe theory, has even computed the
energy necessary to create a baby universe in the laboratory (the temperature is 1,000 trillion degrees, which is
within the range of these hypothetical civilizations).
Of course, until someone actually makes contact with an advanced civilization, all of this amounts to speculation
tempered with the laws of physics, no more than a useful guide in our search for extra-terrestrial intelligence. But one
day, many of us will gaze at the encyclopedia containing the coordinates of perhaps hundreds of earth-like planets in
our sector of the galaxy. Then we will wonder, as Sagan did, what a civilization a millions years ahead of ours will look
like…
should identify even more earth-like planets. It will scan the brightest 1,000 stars within 50 light years of the earth
and will focus on the 50 to 100 brightest planetary systems.
All this, in turn, will stimulate an active effort to determine if any of them harbor life, perhaps some with civilizations
more advanced than ours.
Although it is impossible to predict the precise features of such advanced civilizations, their broad outlines can be
analyzed using the laws of physics. No matter how many millions of years separate us from them, they still must obey
the iron laws of physics, which are now advanced enough to explain everything from sub-atomic particles to the large-
scale structure of the universe, through a staggering 43 orders of magnitude.
Physics of Type I, II, and III Civilizations
Specifically, we can rank civilizations by their energy consumption, using the following principles:
1) The laws of thermodynamics. Even an advanced civilization is bound by the laws of thermodynamics, especially the
Second Law, and can hence be ranked by the energy at their disposal.
2) The laws of stable matter. Baryonic matter (e.g. based on protons and neutrons) tends to clump into three large
groupings: planets, stars and galaxies. (This is a well-defined by product of stellar and galactic evolution,
thermonuclear fusion, etc.) Thus, their energy will also be based on three distinct types, and this places upper limits
on their rate of energy consumption.
3) The laws of planetary evolution. Any advanced civilization must grow in energy consumption faster than the
frequency of life-threatening catastrophes (e.g. meteor impacts, ice ages, supernovas, etc.). If they grow any slower,
they are doomed to extinction. This places mathematical lower limits on the rate of growth of these civilizations.
In a seminal paper published in 1964 in the Journal of Soviet Astronomy, Russian astrophysicist Nicolai Kardashev
theorized that advanced civilizations must therefore be grouped according to three types: Type I, II, and III, which
have mastered planetary, stellar and galactic forms of energy, respectively. He calculated that the energy consumption
of these three types of civilization would be separated by a factor of many billions. But how long will it take to reach
Type II and III status?
Shorter than most realize
Berkeley astronomer Don Goldsmith reminds us that the earth receives about one billionth of the suns energy, and
that humans utilize about one millionth of that. So we consume about one million billionth of the suns total energy. At
present, our entire planetary energy production is about 10 billion billion ergs per second. But our energy growth is
rising exponentially, and hence we can calculate how long it will take to rise to Type II or III status.
Goldsmith says, “Look how far we have come in energy uses once we figured out how to manipulate energy, how to
get fossil fuels really going, and how to create electrical power from hydropower, and so forth; we’ve come up in
energy uses in a remarkable amount in just a couple of centuries compared to billions of years our planet has been
here … and this same sort of thing may apply to other civilizations.”
Physicist Freeman Dyson of the Institute for Advanced Study estimates that, within 200 years or so, we should attain
Type I status. In fact, growing at a modest rate of 1% per year, Kardashev estimated that it would take only 3,200
years to reach Type II status, and 5,800 years to reach Type III status. Living in a Type I,II, or III civilization
For example, a Type I civilization is a truly planetary one, which has mastered most forms of planetary energy. Their
energy output may be on the order of thousands to millions of times our current planetary output. Mark Twain once
said, ”Everyone complains about the weather, but no one does anything about it.“ This may change with a Type I
civilization, which has enough energy to modify the weather. They also have enough energy to alter the course of
earthquakes, volcanoes, and build cities on their oceans.
Currently, our energy output qualifies us for Type 0 status. We derive our energy not from harnessing global forces,
but by burning dead plants (e.g. oil and coal). But already, we can see the seeds of a Type I civilization. We see the
beginning of a planetary language (English), a planetary communication system (the Internet), a planetary economy
(the forging of the European Union), and even the beginnings of a planetary culture (via mass media, TV, rock music,
and Hollywood films).
By definition, an advanced civilization must grow faster than the frequency of life-threatening catastrophes. Since
large meteor and comet impacts take place once every few thousand years, a Type I civilization must master space
travel to deflect space debris within that time frame, which should not be much of a problem. Ice ages may take place
on a time scale of tens of thousands of years, so a Type I civilization must learn to modify the weather within that
time frame.
Artificial and internal catastrophes must also be negotiated. But the problem of global pollution is only a mortal threat
for a Type 0 civilization; a Type I civilization has lived for several millennia as a planetary civilization, necessarily
achieving ecological planetary balance. Internal problems like wars do pose a serious recurring threat, but they have
thousands of years in which to solve racial, national, and sectarian conflicts.
Eventually, after several thousand years, a Type I civilization will exhaust the power of a planet, and will derive their
energy by consuming the entire output of their suns energy, or roughly a billion trillion trillion ergs per second.
With their energy output comparable to that of a small star, they should be visible from space. Dyson has proposed
that a Type II civilization may even build a gigantic sphere around their star to more efficiently utilize its total energy
output. Even if they try to conceal their existence, they must, by the Second Law of Thermodynamics, emit waste
heat. From outer space, their planet may glow like a Christmas tree ornament. Dyson has even proposed looking
specifically for infrared emissions (rather than radio and TV) to identify these Type II civilizations.
Perhaps the only serious threat to a Type II civilization would be a nearby supernova explosion, whose sudden
eruption could scorch their planet in a withering blast of X-rays, killing all life forms. Thus, perhaps the most
interesting civilization is a Type III civilization, for it is truly immortal. They have exhausted the power of a single star,
and have reached for other star systems. No natural catastrophe known to science is capable of destroying a Type III
civilization.
Faced with a neighboring supernova, it would have several alternatives, such as altering the evolution of dying red
giant star which is about to explode, or leaving this particular star system and terraforming a nearby planetary
system.
However, there are roadblocks to an emerging Type III civilization. Eventually, it bumps up against another iron law of
physics, the theory of relativity. Dyson estimates that this may delay the transition to a Type III civilization by
perhaps millions of years.
But even with the light barrier, there are a number of ways of expanding at near-light velocities. For example, the
ultimate measure of a rockets capability is measured by something called “specific impulse” (defined as the product of
the thrust and the duration, measured in units of seconds). Chemical rockets can attain specific impulses of several
hundred to several thousand seconds. Ion engines can attain specific impulses of tens of thousands of seconds. But
to attain near-light speed velocity, one has to achieve specific impulse of about 30 million seconds, which is far
beyond our current capability, but not that of a Type III civilization. A variety of propulsion systems would be available
for sub-light speed probes (such as ram-jet fusion engines, photonic engines, etc.)
How to Explore the Galaxy
Because distances between stars are so vast, and the number of unsuitable, lifeless solar systems so large, a Type III
civilization would be faced with the next question: what is the mathematically most efficient way of exploring the
hundreds of billions of stars in the galaxy?
In science fiction, the search for inhabitable worlds has been immortalized on TV by heroic captains boldly
commanding a lone star ship, or as the murderous Borg, a Type III civilization which absorbs lower Type II civilization
(such as the Federation). However, the most mathematically efficient method to explore space is far less glamorous:
to send fleets of “Von Neumann probes” throughout the galaxy (named after John Von Neumann, who established
the mathematical laws of self-replicating systems).
A Von Neumann probe is a robot designed to reach distant star systems and create factories which will reproduce
copies themselves by the thousands. A dead moon rather than a planet makes the ideal destination for Von Neumann
probes, since they can easily land and take off from these moons, and also because these moons have no erosion.
These probes would live off the land, using naturally occurring deposits of iron, nickel, etc. to create the raw
ingredients to build a robot factory. They would create thousands of copies of themselves, which would then scatter
and search for other star systems.
Similar to a virus colonizing a body many times its size, eventually there would be a sphere of trillions of Von
Neumann probes expanding in all directions, increasing at a fraction of the speed of light. In this fashion, even a
galaxy 100,000 light years across may be completely analyzed within, say, a half million years.
If a Von Neumann probe only finds evidence of primitive life (such as an unstable, savage Type 0 civilization) they
might simply lie dormant on the moon, silently waiting for the Type 0 civilization to evolve into a stable Type I
civilization. After waiting quietly for several millennia, they may be activated when the emerging Type I civilization is
advanced enough to set up a lunar colony. Physicist Paul Davies of the University of Adelaide has even raised the
possibility of a Von Neumann probe resting on our own moon, left over from a previous visitation in our system
aeons ago.
(If this sounds a bit familiar, that’s because it was the basis of the film, 2001. Originally, Stanley Kubrick began the
film with a series of scientists explaining how probes like these would be the most efficient method of exploring outer
space. Unfortunately, at the last minute, Kubrick cut the opening segment from his film, and these monoliths became
almost mystical entities)
New Developments
Since Kardashev gave the original ranking of civilizations, there have been many scientific developments which refine
and extend his original analysis, such as recent developments in nanotechnology, biotechnology, quantum physics,
etc.
For example, nanotechnology may facilitate the development of Von Neumann probes. As physicist Richard Feynman
observed in his seminal essay, “There’s Plenty of Room at the Bottom,” there is nothing in the laws of physics which
prevents building armies of molecular-sized machines. At present, scientists have already built atomic-sized
curiosities, such as an atomic abacus with Buckyballs and an atomic guitar with strings about 100 atoms across.
Paul Davies speculates that a space-faring civilization could use nanotechnology to build miniature probes to explore
the galaxy, perhaps no bigger than your palm. Davies says, “The tiny probes I’m talking about will be so
inconspicuous that it’s no surprise that we haven’t come across one. It’s not the sort of thing that you’re going to
trip over in your back yard. So if that is the way technology develops, namely, smaller, faster, cheaper and if other
civilizations have gone this route, then we could be surrounded by surveillance devices.”
Furthermore, the development of biotechnology has opened entirely new possibilities. These probes may act as life-
forms, reproducing their genetic information, mutating and evolving at each stage of reproduction to enhance their
capabilities, and may have artificial intelligence to accelerate their search.
Also, information theory modifies the original Kardashev analysis. The current SETI project only scans a few
frequencies of radio and TV emissions sent by a Type 0 civilization, but perhaps not an advanced civilization. Because
of the enormous static found in deep space, broadcasting on a single frequency presents a serious source of error.
Instead of putting all your eggs in one basket, a more efficient system is to break up the message and smear it out
over all frequencies (e.g. via Fourier like transform) and then reassemble the signal only at the other end. In this way,
even if certain frequencies are disrupted by static, enough of the message will survive to accurately reassemble the
message via error correction routines. However, any Type 0 civilization listening in on the message on one frequency
band would only hear nonsense. In other words, our galaxy could be teeming with messages from various Type II
and III civilizations, but our Type 0 radio telescopes would only hear gibberish.
Lastly, there is also the possibility that a Type II or Type III civilization might be able to reach the fabled Planck energy
with their machines (10^19 billion electron volts). This is energy is a quadrillion times larger than our most powerful
atom smasher. This energy, as fantastic as it may seem, is (by definition) within the range of a Type II or III
civilization.
The Planck energy only occurs at the center of black holes and the instant of the Big Bang. But with recent advances
in quantum gravity and superstring theory, there is renewed interest among physicists about energies so vast that
quantum effects rip apart the fabric of space and time. Although it is by no means certain that quantum physics
allows for stable wormholes, this raises the remote possibility that a sufficiently advanced civilizations may be able to
move via holes in space, like Alice’s Looking Glass. And if these civilizations can successfully navigate through stable
wormholes, then attaining a specific impulse of a million seconds is no longer a problem. They merely take a short-cut
through the galaxy. This would greatly cut down the transition between a Type II and Type III civilization.
Second, the ability to tear holes in space and time may come in handy one day. Astronomers, analyzing light from
distant supernovas, have concluded recently that the universe may be accelerating, rather than slowing down. If this
is true, there may be an anti-gravity force (perhaps Einstein’s cosmological constant) which is counteracting the
gravitational attraction of distant galaxies. But this also means that the universe might expand forever in a Big Chill,
until temperatures approach near-absolute zero. Several papers have recently laid out what such a dismal universe
may look like. It will be a pitiful sight: any civilization which survives will be desperately huddled next to the dying
embers of fading neutron stars and black holes. All intelligent life must die when the universe dies.
Contemplating the death of the sun, the philosopher Bertrand Russel once wrote perhaps the most depressing
paragraph in the English language: “…All the labors 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 Mans achievement must inevitably be buried beneath the debris of a universe in ruins…”
Today, we realize that sufficiently powerful rockets may spare us from the death of our sun 5 billion years from now,
when the oceans will boil and the mountains will melt. But how do we escape the death of the universe itself?
Astronomer John Barrows of the University of Sussex writes, “Suppose that we extend the classification upwards.
Members of these hypothetical civilizations of Type IV, V, VI, … and so on, would be able to manipulate the structures
in the universe on larger and larger scales, encompassing groups of galaxies, clusters, and superclusters of galaxies.”
Civilizations beyond Type III may have enough energy to escape our dying universe via holes in space.
Lastly, physicist Alan Guth of MIT, one of the originators of the inflationary universe theory, has even computed the
energy necessary to create a baby universe in the laboratory (the temperature is 1,000 trillion degrees, which is
within the range of these hypothetical civilizations).
Of course, until someone actually makes contact with an advanced civilization, all of this amounts to speculation
tempered with the laws of physics, no more than a useful guide in our search for extra-terrestrial intelligence. But one
day, many of us will gaze at the encyclopedia containing the coordinates of perhaps hundreds of earth-like planets in
our sector of the galaxy. Then we will wonder, as Sagan did, what a civilization a millions years ahead of ours will look
like…
| TODAY IS |
