- Email: [email protected]
Ultimate time crystal
Benedict Redgrove/image bank/getty
THIS WEEK
Ultimate time crystal Only a computer made of time crystals, symmetrical in time not in space, could survive the universe’s chilling demise Lisa Grossman, Cambridge, UK
IT IS a chilling prospect. At some point, the universe faces a cold and haunting future. Its entropy, or disorder, is always increasing and when it peaks, energy will no longer be able to flow, making life and almost everything else impossible. By this time, black holes will have evaporated and ever-accelerating expansion will have blown galaxies apart. All that remains will be a uniformly cold, dark, diffuse expanse. According to the laws of 6 | NewScientist | 21 January 2012
thermodynamics, this dismal heat death of the universe lying picture, called the heat death down,” Wilczek says. “We can put of the universe, is unavoidable. up a pretty good fight for a very Now Nobel laureate Frank long time.” Such a device might Wilczek, a theoretical physicist even be able to simulate someone’s at the Massachusetts Institute brain – giving a form of life of Technology, has hatched a extension. survival plan. He reckons a Wilczek came up with this hypothetical device he calls a time bizarre idea while studying crystal could power a computer solid crystals, three-dimensional that would keep on running long structures in which the atoms are after everything else has succumbed to the pull of entropy. “We don’t have to take the heat death of the universe “It’s not the most immediate lying down. We can put up problem in the world, but the a pretty good fight” point is, we don’t have to take the
arranged in regular, repeating patterns. These patterns arise because they cost atoms the least energy to maintain, and so are most comfortable. If you add more energy, the crystal might disappear – ice crystals will melt to liquid water, for instance. Eventually, though, the heat will dissipate and the ice will refreeze in the same pattern. Thanks to Einstein’s special theory of relativity, physicists are used to thinking of time as a dimension, a simple extension to the three dimensions of space. So if you can have crystals in three dimensions, Wilczek wondered, why not in four? He reasoned that the periodic rows of atoms in an ordinary crystal could translate to periodic motion in a time crystal (see diagram, right). Any object that moves in a circle and returns to
In this section n Lethal strain of TB defies drugs, page 8 n Vegetarian apes go carnivore, page 12 n Software will make robots the new PC, page 17
sense,” he says. superconductors have normally It should be possible to build been cooled close to absolute zero, such a device, although Wilczek share the same quantum state admits he doesn’t know how and so flow without resistance. This makes superconductors very difficult it would be. “At present they’re mathematical models,” he efficient at producing huge says. “I don’t have specific designs currents. or proposals.” Wilczek points out that Assuming a time crystal can be superconductors’ lack of resistance made, Wilczek reckons it could be also means that their electrons made into a computer. Because could, in theory, flow forever the time crystal’s charge changes without any energy input – just its position in the loop, it can what is needed to create a time crystal. “A superconductor is close occupy different states that are [to a time crystal], in the sense “We might even upload our that it has currents that flow brains, living on inside the forever, even in its lowest energy computer as the universe state,” he says. “If you add more outside dissolves” energy, it’ll eventually shed that energy and go back to doing what analogous to an ordinary it wants to do.” computer’s 1s and 0s. These In a time crystal, electrons superconducting bits could then will have to flow in a loop not be linked together to form a a line as they do in an ordinary computer. By contrast, an superconductor. What’s more, ordinary superconductor couldn’t they will have to bunch up rather do this because its electrons travel than flowing as a smooth stream. in a continuous stream. This is to ensure that the charge Crucially, such a computer repeats periodically over time, echoing the way that atoms repeat should be perfectly placed to survive the heat death of the in space in an ordinary crystal. universe. For one, it would already At the recent State of the 4In 4D, they’d survive anything Universe symposium convened in be in its lowest energy state, so it wouldn’t need extra energy input Cambridge, UK, to mark Stephen the same spot at regular intervals, Hawking’s 70th birthday, Wilczek to keep on running. “It doesn’t like a planet orbiting a star, has need a power source,” Wilczek showed mathematically that a the same sort of symmetry in says. To boot, superconductors lump of looping charge can zip time that crystals have in space. tend to work only at temperatures around forever in its lowest But to truly count as a time close to absolute zero. So as the energy state. “It is perpetual crystal, that orbit would have to universe gets colder and darker, motion, but not in the forbidden represent the object’s lowest energy state – just as the periodic From From space space to to time time to to computing computing arrangement of atoms in a crystal Crystals needn’t only exist in 3 dimensions. A Crystals needn’t only exist in 3 dimensions. A rotating rotating charge charge is their lowest energy state. has the the same same symmetry symmetry in in time time as as a a conventional conventional crystal crystal has has in in space space has In other words, the crystal ORDINARY (SPACE) (SPACE) CRYSTAL: CRYSTAL: Atoms Atoms spaced spaced periodically periodically ORDINARY would be able to keep on orbiting forever without needing any extra Atoms Atoms energy. That makes it look “perilously close to a perpetual TIME TIME CRYSTAL: CRYSTAL: Charge Charge rotates rotates periodically periodically motion machine”, Wilczek says. Normally forbidden by thermodynamics, there is at least one instance of perpetual motion that is allowed: the electrons Rotating Rotating charge charge flowing in a superconductor. FUTURE COMPUTER: FUTURE COMPUTER: The The time time crystal’s crystal’s charge charge changes changes its its position, position, Unlike electrons travelling creating different different states states that that could could act act as as the the bits bits of of a a computer computer creating through an ordinary conductive wire, where resistance erodes 0 0 1 1 1 0 0 1 1 1 their flow, those in
and all other processes cease, this computer would simply get more comfortable. “It could dodge the heat death of the universe for a very long time,” he says. Some doubt there would be any point to such a device. “It’s probably not revolutionary,” says Craig Hogan, a physicist at Fermilab in Batavia, Illinois. It’s not hard to dream up some possibilities, though. Like an ultimate time capsule, Wilczek’s computer could store information about the universe’s former life, the only legacy of what the universe once was. More ambitiously, if the right science and technology ever becomes available, humans might upload their brains to the computer, in a sense living on while the universe outside dissolves. It wouldn’t be much of a life. As the computer wouldn’t be able to accept new inputs, it would run the same brain-simulating program on a loop. “My best idea of what we’d want to do is to find some kind of experience that we really like, and program it in, so that experience would happen over and over again,” says Wilczek. Milan Cirkovic, a physicist at the Institute for Ethics and Emerging Technologies, doesn’t relish that repetition. Luckily for him, others have come up with some equally wacky alternatives . Freeman Dyson of the Institute for Advanced Study in Princeton, New Jersey, reckons conscious beings on the verge of a heat death might slow down their sense of subjective time. Andrei Linde of Stanford University in California suggested that if our universe is just one of many in a multiverse, we could tunnel through a black hole to a neighbouring universe that is still warm and humming. The latter appeals to Cirkovic. It’s not clear that we do live in a multiverse, however. So Wilczek remains excited about the time crystal. “If the options were to have pleasant dreams forever, or just fade out, I guess I’d rather have the dreams.” n 21 January 2012 | NewScientist | 7
THIS WEEK
Ultimate time crystal Only a computer made of time crystals, symmetrical in time not in space, could survive the universe’s chilling demise Lisa Grossman, Cambridge, UK
IT IS a chilling prospect. At some point, the universe faces a cold and haunting future. Its entropy, or disorder, is always increasing and when it peaks, energy will no longer be able to flow, making life and almost everything else impossible. By this time, black holes will have evaporated and ever-accelerating expansion will have blown galaxies apart. All that remains will be a uniformly cold, dark, diffuse expanse. According to the laws of 6 | NewScientist | 21 January 2012
thermodynamics, this dismal heat death of the universe lying picture, called the heat death down,” Wilczek says. “We can put of the universe, is unavoidable. up a pretty good fight for a very Now Nobel laureate Frank long time.” Such a device might Wilczek, a theoretical physicist even be able to simulate someone’s at the Massachusetts Institute brain – giving a form of life of Technology, has hatched a extension. survival plan. He reckons a Wilczek came up with this hypothetical device he calls a time bizarre idea while studying crystal could power a computer solid crystals, three-dimensional that would keep on running long structures in which the atoms are after everything else has succumbed to the pull of entropy. “We don’t have to take the heat death of the universe “It’s not the most immediate lying down. We can put up problem in the world, but the a pretty good fight” point is, we don’t have to take the
arranged in regular, repeating patterns. These patterns arise because they cost atoms the least energy to maintain, and so are most comfortable. If you add more energy, the crystal might disappear – ice crystals will melt to liquid water, for instance. Eventually, though, the heat will dissipate and the ice will refreeze in the same pattern. Thanks to Einstein’s special theory of relativity, physicists are used to thinking of time as a dimension, a simple extension to the three dimensions of space. So if you can have crystals in three dimensions, Wilczek wondered, why not in four? He reasoned that the periodic rows of atoms in an ordinary crystal could translate to periodic motion in a time crystal (see diagram, right). Any object that moves in a circle and returns to
In this section n Lethal strain of TB defies drugs, page 8 n Vegetarian apes go carnivore, page 12 n Software will make robots the new PC, page 17
sense,” he says. superconductors have normally It should be possible to build been cooled close to absolute zero, such a device, although Wilczek share the same quantum state admits he doesn’t know how and so flow without resistance. This makes superconductors very difficult it would be. “At present they’re mathematical models,” he efficient at producing huge says. “I don’t have specific designs currents. or proposals.” Wilczek points out that Assuming a time crystal can be superconductors’ lack of resistance made, Wilczek reckons it could be also means that their electrons made into a computer. Because could, in theory, flow forever the time crystal’s charge changes without any energy input – just its position in the loop, it can what is needed to create a time crystal. “A superconductor is close occupy different states that are [to a time crystal], in the sense “We might even upload our that it has currents that flow brains, living on inside the forever, even in its lowest energy computer as the universe state,” he says. “If you add more outside dissolves” energy, it’ll eventually shed that energy and go back to doing what analogous to an ordinary it wants to do.” computer’s 1s and 0s. These In a time crystal, electrons superconducting bits could then will have to flow in a loop not be linked together to form a a line as they do in an ordinary computer. By contrast, an superconductor. What’s more, ordinary superconductor couldn’t they will have to bunch up rather do this because its electrons travel than flowing as a smooth stream. in a continuous stream. This is to ensure that the charge Crucially, such a computer repeats periodically over time, echoing the way that atoms repeat should be perfectly placed to survive the heat death of the in space in an ordinary crystal. universe. For one, it would already At the recent State of the 4In 4D, they’d survive anything Universe symposium convened in be in its lowest energy state, so it wouldn’t need extra energy input Cambridge, UK, to mark Stephen the same spot at regular intervals, Hawking’s 70th birthday, Wilczek to keep on running. “It doesn’t like a planet orbiting a star, has need a power source,” Wilczek showed mathematically that a the same sort of symmetry in says. To boot, superconductors lump of looping charge can zip time that crystals have in space. tend to work only at temperatures around forever in its lowest But to truly count as a time close to absolute zero. So as the energy state. “It is perpetual crystal, that orbit would have to universe gets colder and darker, motion, but not in the forbidden represent the object’s lowest energy state – just as the periodic From From space space to to time time to to computing computing arrangement of atoms in a crystal Crystals needn’t only exist in 3 dimensions. A Crystals needn’t only exist in 3 dimensions. A rotating rotating charge charge is their lowest energy state. has the the same same symmetry symmetry in in time time as as a a conventional conventional crystal crystal has has in in space space has In other words, the crystal ORDINARY (SPACE) (SPACE) CRYSTAL: CRYSTAL: Atoms Atoms spaced spaced periodically periodically ORDINARY would be able to keep on orbiting forever without needing any extra Atoms Atoms energy. That makes it look “perilously close to a perpetual TIME TIME CRYSTAL: CRYSTAL: Charge Charge rotates rotates periodically periodically motion machine”, Wilczek says. Normally forbidden by thermodynamics, there is at least one instance of perpetual motion that is allowed: the electrons Rotating Rotating charge charge flowing in a superconductor. FUTURE COMPUTER: FUTURE COMPUTER: The The time time crystal’s crystal’s charge charge changes changes its its position, position, Unlike electrons travelling creating different different states states that that could could act act as as the the bits bits of of a a computer computer creating through an ordinary conductive wire, where resistance erodes 0 0 1 1 1 0 0 1 1 1 their flow, those in
and all other processes cease, this computer would simply get more comfortable. “It could dodge the heat death of the universe for a very long time,” he says. Some doubt there would be any point to such a device. “It’s probably not revolutionary,” says Craig Hogan, a physicist at Fermilab in Batavia, Illinois. It’s not hard to dream up some possibilities, though. Like an ultimate time capsule, Wilczek’s computer could store information about the universe’s former life, the only legacy of what the universe once was. More ambitiously, if the right science and technology ever becomes available, humans might upload their brains to the computer, in a sense living on while the universe outside dissolves. It wouldn’t be much of a life. As the computer wouldn’t be able to accept new inputs, it would run the same brain-simulating program on a loop. “My best idea of what we’d want to do is to find some kind of experience that we really like, and program it in, so that experience would happen over and over again,” says Wilczek. Milan Cirkovic, a physicist at the Institute for Ethics and Emerging Technologies, doesn’t relish that repetition. Luckily for him, others have come up with some equally wacky alternatives . Freeman Dyson of the Institute for Advanced Study in Princeton, New Jersey, reckons conscious beings on the verge of a heat death might slow down their sense of subjective time. Andrei Linde of Stanford University in California suggested that if our universe is just one of many in a multiverse, we could tunnel through a black hole to a neighbouring universe that is still warm and humming. The latter appeals to Cirkovic. It’s not clear that we do live in a multiverse, however. So Wilczek remains excited about the time crystal. “If the options were to have pleasant dreams forever, or just fade out, I guess I’d rather have the dreams.” n 21 January 2012 | NewScientist | 7