Beyond: Our Future in Space (31 page)

An even more exciting capability is self-replication. Eric Drexler talked about it in his prescient 1986 book on nanotechnology,
Engines of Creation
. Even earlier, in lectures at Princeton University, physicist Freeman Dyson described thought experiments involving large-scale replicating machines. In one, spacecraft traveled to Saturn’s small moon Enceladus, mined material to replicate themselves, and also launched spacecraft powered by solar sails to carry ice to Mars and begin to terraform the red planet. As with self-assembly, self-replication has made more progress in the lab than in space.

The RepRap Project began in 2005 with the goal of designing a 3-D printer that could create most of its own components. It started at the University of Bath in England, but the code for computer-aided design and manufacture is open source, so the project has spawned a large developer community. In 2008, the RepRap machine “Darwin” produced all the parts needed to make an identical “child” machine. The project will make its technology freely available to anyone, with the goal of helping people make artifacts for everyday life.
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The ultimate expression of self-replication is a von Neumann probe. This is a spacecraft that could go to a neighboring star system, mine materials to create replicas of itself, and send those out to other star systems. Using fairly conventional forms of propulsion, these probes could spread through a galaxy the size of the Milky Way in less than a few million years. The probes could investigate planetary systems and send information back to us on the home planet.
²³

The concept is named after the Hungarian mathematician and physicist John von Neumann. He was one of the major intellectual figures of the twentieth century, making important contributions to mathematics, physics, computer science, and economics. Noted physicist Eugene Wigner recalled that von Neumann’s unusual mind was like a “. . . perfect instrument whose gears were machined to mesh accurately within a thousandth of an inch.” But he was less perfect in the real world. As a driver, he had numerous accidents and a few arrests, usually because he was distracted or reading. He overate, told off-color jokes, and did his best work in noisy and chaotic environments.

In the 1940s, von Neumann figured out the logical requirements for self-replication. He described a computational “machine” that could make copies of itself, allow for errors, and evolve. This remarkable work preceded computers and anticipated the later discovery of DNA and the mechanisms of life. His work was theoretical, but it created a roadmap for building actual self-replicating machines.
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Perhaps this is the way we will eventually explore the galaxy. Diffusing through interstellar space and exploring distant worlds with a fleet of self-replicating probes sounds fantastical, but it could be achieved with a reasonable extrapolation of our current technology. Which raises the question: Has any other civilization done this?

Warp Drives and Transporters

No fundamental obstacle prohibits the creation of a propulsion system that can accelerate a payload to a significant fraction of the speed of light. The highest speed ever reached by a spacecraft was 165,000 mph or 25 miles per second, when the probe Juno used Earth’s gravity to catapult toward Jupiter. That’s fifty times faster than a bullet, but only 0.01 percent of the speed of light. Reaching the nearest stars in less than fifty years would require speeds a thousand times faster, or 10 percent of the speed of light.

Let’s now venture beyond the bounds of projected capabilities based on well-established science, into the realm of speculation and science fiction.
²⁵

Two staples of science fiction, and routine occurrences on
Star Trek
, are warp drive and teleportation. A warp drive enables faster-than-light travel. Einstein’s theory of special relativity posits the speed of light as an absolute limit for the transmission of matter, energy, or information of any kind. Special relativity is a foundational principle in physics, so that would appear to kill the possibility of a warp drive. Tachyons—fundamental particles that travel faster than light—were hypothesized in 1967, but no evidence for them has ever been seen.
²⁶
In 1994, physicist Miguel Alcubierre proposed a theoretical solution for faster-than-light travel based on negative mass.
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The consensus among physicists is that a warp drive is not possible under the known laws of physics, but the idea got some attention at the 100 Year Starship Symposium at the Johnson Space Center in 2012.

What about teleportation? Imagine this situation. You’re about to step into a device that will deconstruct your atoms into an energy pattern, beam the information to a remote target, and rematerialize you.

In “Realm of Fear,” the 128th episode of the TV series
Star Trek: The Next Generation
, Lieutenant Reginald Barclay develops a fear of the transporter that’s used to beam crew members down to the surface of a planet. He becomes obsessed with all the things that could go wrong when the 10
²⁸
atoms in his body are dismantled and then reassembled.
²⁸
Eventually, his fear becomes debilitating.

There’s no formal term for this condition.

The TV series and subsequent films were sketchy on how transporter technology works. It’s supposed to transport objects accurately at the level of individual atoms, using something called a Heisenberg compensator to remove uncertainty from subatomic measurements. When technical adviser Michael Okuda was asked how it works, he said, “It works very well, thank you.” On the original
Star Trek
show, the special effect for the transporter was created before computer animation existed, so it was low tech: a slow-motion camera was turned upside down and it filmed backlit grains of aluminum powder falling in front of a black background.

Classical teleportation measures every atom in the human body, encoding that information into photons, sending the photons to a remote location, and using the information to reconstruct a perfect replica of the body. That’s just an engineering problem. But with 10
²⁸
atoms to deal with, it’s a very nasty engineering problem.

For decades, it was thought that teleportation defied physics. Heisenberg’s uncertainty principle says that we can’t simultaneously and accurately measure all the properties of even a single atom, let alone vast numbers of them. Measuring any property of a subatomic particle changes its state. So there’s no way to convey that state to a remote location with high fidelity.

In 1993, physicist Charles Bennett and his team made a breakthrough. They realized that particles at two different locations could be induced into something called
quantum entanglement
, where information about their physical states was shared. The loophole that lets us circumvent Heisenberg’s uncertainty principle involves trying not to know too much. We disturb the particle before we measure it, so we never know its state. Then we can subtract that disturbance at the other end to re-create the original state of the particle (
Figure 52
).
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Think of entanglement as a black box that conceals but connects events at two locations remote from each other. It seems to violate causality because changes at the two locations occur instantly, but there’s a limit to what we can know or measure. Quantum entanglement has been demonstrated using photons, electrons, buckyballs, and even small diamonds. It’s pure quantum weirdness.

Let’s personalize it. Alice wants to teleport something to Bob.
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An entangled pair of photons serves as the intermediary in their experiment. She measures a property of her photon where the outcome depends on the entangled state of the pair. She records her measurement and sends it to Bob. He can’t tell what the state of her photon was, because the entanglement used in the measurement hides the true nature of that state. What Bob can do, however, is use information from Alice to modify the state of his photon. Then he can re-create the exact state of the photon Alice originally measured.

Even though the entangled state spans two separate locations, Bob can’t complete the teleportation until she sends him the result of her measurement. So the special theory of relativity and causality aren’t broken. The process allows information to be copied with perfect fidelity, although teleportation doesn’t literally make a copy; it shifts quantum information from one place to another, destroying the original in the process.

Progress is rapid in this exciting research field. Physicists first demonstrated quantum teleportation in the lab in 1998 over a distance of a meter. In 2012, a research group teleported information between two locations in the Canary Islands 143 kilometers apart. In 2013, worldwide teleportation was demonstrated.
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The reliability of teleportation is also improving dramatically. In 2009, transfer of quantum information over distances of a few meters succeeded only one in 100 million times. In 2014, scientists at Delft University in the Netherlands teleported the quantum state of two entangled electrons with 100 percent reliability.
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The mechanism of quantum entanglement is being used for cryptography and it’s likely to play a role in developing faster computers, but most physicists think it’s unlikely we’ll ever be able to create and interrogate the quantum entangled state of more than a few thousand atoms. So transporters aren’t even on the far horizon.

Star Trek
’s Lieutenant Barclay was only worried about his atoms being scrambled so that he turned into a pile of unrecognizable goo. But he also should have been worried about the philosophical implications of teleportation. You are not your particles. The atoms in your body fall off and get replaced all the time. Toast turns into eyelashes. You and your thoughts and your genetic information are really patterns rather than piles of particles. So when a transporter disassembles you, it kills you; when it reassembles you elsewhere, it gives birth to you. Logically it could do that as many times and at as many locations as it liked. Where would that leave your sense of self?

13

Cosmic Companionship

_______________________

Number of Pen Pals

We’ve seen how hard it is to leave the cradle of Earth, even for a short time. However, enough ingenuity and technology are being applied to the problem that it’s only a matter of time before we spread beyond our planet. This raises a series of questions. Are we the only species to travel in space? Are we the first? If we are not, how would we know? It will spur space exploration if we know we are not the first or the only species to spread our wings beyond the home planet.

The question of cosmic companionship brings us back to the Drake equation and all its embedded uncertainty. Recall that the equation is a multiplicative set of factors incorporating astronomy, biology, and sociology and designed to give an estimate of the number of civilizations that are communicating or traveling through space at a given time.

Exoplanet surveys suggest there are 10 billion Earth-like planets around Sun-like stars. That’s a vast number of “Petri dishes” in the Milky Way: locations with suitable physical conditions and the chemical ingredients for biology. Scientific arguments based on a sample of one are unreliable, but the fact that life formed on Earth as soon as suitable conditions arose is taken as evidence that habitability almost always means actually inhabited. A counterargument is that life only seems to have arisen once on this planet, but that argument is weak because other origination events may have been lost or concealed or outcompeted by the existing form of life. If life is found on Mars, either present or ancient, it will be good evidence that the fraction of habitable planets that host life is close to one. If we assume that for a moment, the Drake equation becomes
N
~
f
_i
x
f
_c
x
L
. Here,
N
is the number of civilizations in our galaxy that are currently able to communicate through space,
f
_i
is the fraction of planets with life that go on to develop intelligent life,
f
_c
is the fraction of those that can communicate through space, and
L
is the length of time that they endure or have such a capability.

At this point, opinions diverge and uncertainty rules. Some biologists argue that
f
_i
is low because only a handful of the hundreds of millions of species on Earth developed intelligence. Others argue that biology has trended toward greater complexity over time, and there may be an evolutionary advantage to the development of brains. The fraction
f
_c
is even more controversial. There are intelligent species on Earth that can’t send signs of their existence into space—elephants, orcas, octopuses, and others. They could have hypothetical counterparts on other worlds. There are also many reasons why a technological civilization may choose not to travel in space, communicate, or somehow reveal its existence. We lose all traction on logic when we enter the realm of alien sociology.
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