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kmguru
Staff member
USA TODAY
Maybe time travel could be possible
Q: I believe Einstein's General Relativity Theory mathematically proved that time travel into the past is impossible. Do the recent experiments showing that light can be slowed, then returned to its normal speed, have any theoretical implications for time travel?
Richard Hallock
A time machine model.
A: Yes, according to Ronald Mallett, theoretical physicist and professor at the University of Connecticut, recent experiments slowing light's speed may make time-travel feasible. Mallet thinks he can harness slow-light energy and turn the future into the past.
You're somewhat mistaken, however, about Einstein proving time travel impossible. Instead, his general theory of relativity describes how matter warps space-time. It's theoretically possible to distort the space-time we live in enough to create a time-travel path (called a closed timelike curve). Walking along such a path loop, you would find your watch running forward as normal but you would eventually reach the place-time you started.
Mallett thinks time travel is not merely theoretically possible but doable , given the speed-of-light breakthrough. He and a group of scientists at University of Connecticut are designing the first experiment to test Mallett's ideas. They plan to build a time-travel device.
Matter distorts space and time. Clocks, for example, run slower in Earth's gravitational field than they do in outer space. Get a really massive object, say the Universe, spinning and you can twist space and time into a ring. So time, instead of marching straight ahead in a line from past to future, curves around. The future can meet the past and you, following the ring, can return to a particular moment.
The energy requirements totally rule out this approach. Rotate the Universe? Forget it. Mallett knows, though, he doesn't need mass. He can use light. Light causes space to bend. Last year Mallett published a paper in Physics Letters describing how a circulating laser beam creates a vortex in space within its circle. The bent laser light actually causes space to whirl around like a twister within the circle.
Mallett deduced that, if he adds a second laser beam shining in the opposite direction and increases its intensity enough, he can warp time into a loop. Unfortunately, once again the energy required is out of reach.
Then he saw an answer. His equations show the slower the light moves within the laser circle, the more space and time distort. Bingo. He can get the needed energy from slow-moving light. The whole crazy notion suddenly became maybe, just maybe, feasible.
In February 1999, Lene Hua and a team at Rowland Institute for Science succeeded slowing light to 38 miles per hour-a galloping zebra goes faster. Mallett plans to use their results in his experiment.
However, J. Richard Gott, professor of astrophysical sciences at Princeton University and author of Time Travel in Einstein's Universe , cautions that:
"One has to distinguish between the speed of light in empty space, which is a constant, and through a medium, which can be less. Light travels more slowly through water than through empty space but this does not mean that you age more slowly while scuba diving or that it is easier to twist space-time underwater.
"The experiments done so far don't lower the speed of light in empty space; they just lower the speed of light in a medium and should not make it easier to twist space-time. Thus, it should not take any less mass-energy to form a black hole or a time machine of a given size in such a medium."
William Stwalley (Mallett's department head), Mallett, and a team of cold-atom researchers plan their attack in stages. First they will trap a particle in a light circle and observe its spin. Then they will add the second light beam and observe. Mallett doesn't know what to expect but hopes for some evidence of time travel. Perhaps the spinning particle will be joined by another spinning particle-itself, from the future.
"...maybe backward time travel is possible, but only up to the moment that time travel is invented. We haven't invented it yet, so they can't come to us. They can come to as far back as whatever it would be, say A.D. 2300, but not further back in time." -Carl Sagan, NOVA interview
(Answered by April Holladay, science correspondent, June 20, 2001)
Maybe time travel could be possible
Q: I believe Einstein's General Relativity Theory mathematically proved that time travel into the past is impossible. Do the recent experiments showing that light can be slowed, then returned to its normal speed, have any theoretical implications for time travel?
Richard Hallock
A time machine model.
A: Yes, according to Ronald Mallett, theoretical physicist and professor at the University of Connecticut, recent experiments slowing light's speed may make time-travel feasible. Mallet thinks he can harness slow-light energy and turn the future into the past.
You're somewhat mistaken, however, about Einstein proving time travel impossible. Instead, his general theory of relativity describes how matter warps space-time. It's theoretically possible to distort the space-time we live in enough to create a time-travel path (called a closed timelike curve). Walking along such a path loop, you would find your watch running forward as normal but you would eventually reach the place-time you started.
Mallett thinks time travel is not merely theoretically possible but doable , given the speed-of-light breakthrough. He and a group of scientists at University of Connecticut are designing the first experiment to test Mallett's ideas. They plan to build a time-travel device.
Matter distorts space and time. Clocks, for example, run slower in Earth's gravitational field than they do in outer space. Get a really massive object, say the Universe, spinning and you can twist space and time into a ring. So time, instead of marching straight ahead in a line from past to future, curves around. The future can meet the past and you, following the ring, can return to a particular moment.
The energy requirements totally rule out this approach. Rotate the Universe? Forget it. Mallett knows, though, he doesn't need mass. He can use light. Light causes space to bend. Last year Mallett published a paper in Physics Letters describing how a circulating laser beam creates a vortex in space within its circle. The bent laser light actually causes space to whirl around like a twister within the circle.
Mallett deduced that, if he adds a second laser beam shining in the opposite direction and increases its intensity enough, he can warp time into a loop. Unfortunately, once again the energy required is out of reach.
Then he saw an answer. His equations show the slower the light moves within the laser circle, the more space and time distort. Bingo. He can get the needed energy from slow-moving light. The whole crazy notion suddenly became maybe, just maybe, feasible.
In February 1999, Lene Hua and a team at Rowland Institute for Science succeeded slowing light to 38 miles per hour-a galloping zebra goes faster. Mallett plans to use their results in his experiment.
However, J. Richard Gott, professor of astrophysical sciences at Princeton University and author of Time Travel in Einstein's Universe , cautions that:
"One has to distinguish between the speed of light in empty space, which is a constant, and through a medium, which can be less. Light travels more slowly through water than through empty space but this does not mean that you age more slowly while scuba diving or that it is easier to twist space-time underwater.
"The experiments done so far don't lower the speed of light in empty space; they just lower the speed of light in a medium and should not make it easier to twist space-time. Thus, it should not take any less mass-energy to form a black hole or a time machine of a given size in such a medium."
William Stwalley (Mallett's department head), Mallett, and a team of cold-atom researchers plan their attack in stages. First they will trap a particle in a light circle and observe its spin. Then they will add the second light beam and observe. Mallett doesn't know what to expect but hopes for some evidence of time travel. Perhaps the spinning particle will be joined by another spinning particle-itself, from the future.
"...maybe backward time travel is possible, but only up to the moment that time travel is invented. We haven't invented it yet, so they can't come to us. They can come to as far back as whatever it would be, say A.D. 2300, but not further back in time." -Carl Sagan, NOVA interview
(Answered by April Holladay, science correspondent, June 20, 2001)
kmguru
Staff member
Boston Globe
Professor's time travel idea fires up the imagination
By David Abel, Globe Staff, 4/5/2002
Ronald Mallett, a physicist at the University of Connecticut, believes he knows how to build a time machine - an actual device that could send something or someone from the future to the past, or vice versa.
He's not joking.
Unlike other physicists who have pondered the science of time travel, the 57-year-old professor has devised a machine he believes could transport anything from an atom to a person from one time to another.
''I'm not a nut. ... I hope to have a working mockup and start experiments this fall,'' says Mallett, who will detail his ideas about time travel tonight at Boston's Museum of Science. ''I would think I was a crackpot, too, if there weren't other colleagues I knew who were working on it. This isn't Ron Mallett's theory of matter; it's Einstein's theory of relativity. I'm not pulling things out of the known laws of physics.''
But Alan Guth, a physics professor at MIT who has studied the theory of time machines, says he isn't sure it's even theoretically possible to travel through time. As far as whether time travel is a possibility, he says: ''Definitely not within our lifetimes.''
Another physicist, Stanley Deser, a professor at Brandeis University who recently co-authored a paper titled ''Time Travel?,'' says the problem is not the physics, it's the feasibility of making time travel work. ''This is about trying to amass all the matter of the universe in a very small region,'' he says. ''Good luck.''
After 27 years at UConn, Mallett has the confidence of his boss, William Stwalley, chairman of the university's physics department. ''His ideas certainly have merit,'' Stwalley says. ''I think some of his ideas are very interesting and they would make nice tests of general relativity.''
Mallett's plan doesn't require some sort of sleigh, the means of transport in H.G. Wells's ''The Time Machine,'' or reaching 88 miles per hour in a flying DeLorean as in the movie ''Back to the Future.'' His time machine merely uses a ring of light.
According to Einstein's theory of gravity, anything that has mass or energy distorts the space and the passage of time around it, like a bowling ball dropped on a trampoline. Circulating laser beams in the right way, by slowing them down and shooting them through anything from fiber-optic cable to special crystals, might create a similar distortion that could theoretically transport someone through different times, Mallett believes.
The professor and his UConn colleagues plan to build a device to test whether it's possible to transport a subatomic particle, probably a neutron, through time. The energy from a rotating laser beam, Mallett hopes, would warp the space inside the ring of the light so that gravity forces the neutron to rotate sideways. With even more energy, it's possible, he believes, a second neutron would appear. The second particle would be the first one visiting itself from the future.
While Mallett acknowledges that sending a person through time may require more energy than physicists today know how to harness, he sees it merely as ''an engineering problem.'' If it's possible to use light to send a neutron through time, a feat that doesn't require as much energy as sending a human, he believes it wouldn't be long before engineers figure out a way to send a person.
''What we're talking about is at the edge of current technology, not beyond current technology,'' he says.
Since his father, a heavy smoker, died at the age of 33 when Mallett was 10 years old, Mallett has longed for a way to travel back in time to warn him about the dangers of cigarettes.
For most of his career, however, Mallett kept secret that his desire for time travel had drawn him to become a physicist. It wasn't until a few years ago, when he began researching a book on the topic, that he arrived at his idea of how to build a time machine.
If his idea pans out, won't there be a host of potential paradoxes, such as time travelers killing their parents and making it impossible for them to exist? No, he says, explaining that those travelers would continue to exist in a ''parallel universe.''
And what about the ethics of changing history?
There would be government laws to control time travel, he believes.
''Any technology has a potential nefarious side to it,'' he says. ''But I don't think there's a way to stop it. We as a species have always reached out. We've been doing that since the caves. I say let's make it so that we better reality. I think we can bravely do that.''
David Abel can be reached at dabel@globe.com.
Professor's time travel idea fires up the imagination
By David Abel, Globe Staff, 4/5/2002
Ronald Mallett, a physicist at the University of Connecticut, believes he knows how to build a time machine - an actual device that could send something or someone from the future to the past, or vice versa.
He's not joking.
Unlike other physicists who have pondered the science of time travel, the 57-year-old professor has devised a machine he believes could transport anything from an atom to a person from one time to another.
''I'm not a nut. ... I hope to have a working mockup and start experiments this fall,'' says Mallett, who will detail his ideas about time travel tonight at Boston's Museum of Science. ''I would think I was a crackpot, too, if there weren't other colleagues I knew who were working on it. This isn't Ron Mallett's theory of matter; it's Einstein's theory of relativity. I'm not pulling things out of the known laws of physics.''
But Alan Guth, a physics professor at MIT who has studied the theory of time machines, says he isn't sure it's even theoretically possible to travel through time. As far as whether time travel is a possibility, he says: ''Definitely not within our lifetimes.''
Another physicist, Stanley Deser, a professor at Brandeis University who recently co-authored a paper titled ''Time Travel?,'' says the problem is not the physics, it's the feasibility of making time travel work. ''This is about trying to amass all the matter of the universe in a very small region,'' he says. ''Good luck.''
After 27 years at UConn, Mallett has the confidence of his boss, William Stwalley, chairman of the university's physics department. ''His ideas certainly have merit,'' Stwalley says. ''I think some of his ideas are very interesting and they would make nice tests of general relativity.''
Mallett's plan doesn't require some sort of sleigh, the means of transport in H.G. Wells's ''The Time Machine,'' or reaching 88 miles per hour in a flying DeLorean as in the movie ''Back to the Future.'' His time machine merely uses a ring of light.
According to Einstein's theory of gravity, anything that has mass or energy distorts the space and the passage of time around it, like a bowling ball dropped on a trampoline. Circulating laser beams in the right way, by slowing them down and shooting them through anything from fiber-optic cable to special crystals, might create a similar distortion that could theoretically transport someone through different times, Mallett believes.
The professor and his UConn colleagues plan to build a device to test whether it's possible to transport a subatomic particle, probably a neutron, through time. The energy from a rotating laser beam, Mallett hopes, would warp the space inside the ring of the light so that gravity forces the neutron to rotate sideways. With even more energy, it's possible, he believes, a second neutron would appear. The second particle would be the first one visiting itself from the future.
While Mallett acknowledges that sending a person through time may require more energy than physicists today know how to harness, he sees it merely as ''an engineering problem.'' If it's possible to use light to send a neutron through time, a feat that doesn't require as much energy as sending a human, he believes it wouldn't be long before engineers figure out a way to send a person.
''What we're talking about is at the edge of current technology, not beyond current technology,'' he says.
Since his father, a heavy smoker, died at the age of 33 when Mallett was 10 years old, Mallett has longed for a way to travel back in time to warn him about the dangers of cigarettes.
For most of his career, however, Mallett kept secret that his desire for time travel had drawn him to become a physicist. It wasn't until a few years ago, when he began researching a book on the topic, that he arrived at his idea of how to build a time machine.
If his idea pans out, won't there be a host of potential paradoxes, such as time travelers killing their parents and making it impossible for them to exist? No, he says, explaining that those travelers would continue to exist in a ''parallel universe.''
And what about the ethics of changing history?
There would be government laws to control time travel, he believes.
''Any technology has a potential nefarious side to it,'' he says. ''But I don't think there's a way to stop it. We as a species have always reached out. We've been doing that since the caves. I say let's make it so that we better reality. I think we can bravely do that.''
David Abel can be reached at dabel@globe.com.
kmguru
Staff member
Angels & Universes
Radical science: did angels create the universe?
A theory that claims that it might be possible to make universes in the laboratory may not be as far-fetched as it sounds, says Marcus Chown
15 March 2002
The ultimate experiment is about to begin. On a cold, lonely moon, shrouded in purple-pink fog, a sentient ocean marshals the energy of a galaxy and focuses it on to a tiny mote of matter. A hundred billion stars flicker and dim. The air above the ocean sizzles and catches fire. Crushed by stupendous energies, the mote twists and bucks and, with a violent shudder, implodes. Elsewhere – in another space, another time – a searing-hot fireball explodes out of nothingness and begins to expand and cool. The ultimate scientific experiment has produced the ultimate experimental result: the birth of a new universe.
Could our universe have been born in such a way? According to Edward Harrison, it's a real possibility. "Our universe could easily be the outcome of an experiment carried out by a superior intelligence in another universe," says Harrison, a British physicist, formerly of the University of Massachusetts at Amherst.
Why suggest such an outlandish thing? Because it sheds light on a deep puzzle: why the laws of physics appear "fine tuned" for our existence. Even slight deviations in the laws would result in a universe devoid of stars and life. If, for instance, the force of gravity were just a few per cent weaker it could not squeeze and heat the matter inside stars to the millions of degrees necessary to trigger sunlight-generating nuclear reactions. If gravity were only a few per cent stronger, however, it would heat up stars, causing them to consume their fuel faster. They would not exist for the billions of years needed for evolution to produce intelligence.
This kind of fine tuning is widespread. One possible explanation is that the universe was "designed" by God. Some scientists accept this, but "unfortunately, it terminates further scientific enquiry", says Harrison. The other possibility is that the universe is the way it is because, if it were not, we would not be here to notice. According to this topsy-turvy reasoning known as the "anthropic principle", it is unsurprising that we find ourselves in a universe that is fine tuned for the existence of galaxies, stars and life. We could hardly have evolved in a universe that was not.
The anthropic principle leads to the idea that our universe is one of countless others. In each universe of this "multiverse", forces like gravity have different strengths. An unavoidable consequence, however, is that most universes lack the special conditions needed for the birth of galaxies, stars, planets and so on. "There will be countless lifeless universes," says Harrison. "This is waste on a truly cosmic scale."
But in cosmology, as in politics, there may be a third way. According to Harrison, the multiverse could be far from a wasteland. It could be dominated by universes with galaxies and stars and life. The prerequisite is that life-bearing universes have a special ability: the ability to reproduce. Specifically, Harrison is suggesting that intelligent life actually makes new universes. "If so, then in offspring universes which are fit for life, new life evolves to a high level of intelligence, then creates further universes," says Harrison.
In Harrison's scheme, dubbed the "natural selection of universes", the laws of physics most suited for the emergence and evolution of life are naturally selected by life itself. The origin of our universe is explained. It was created by super-intelligent beings living in another universe.
If Harrison is right, the fine tuning of the laws of physics has two possible explanations. New universes could inherit the characteristics of their cosmic parents, as children inherit the characteristics of their parents. Small "genetic variations" in the laws between generations would ensure that new universes were not carbon copies of their predecessors. It follows that since the parent of our universe was fine tuned for life and similar to our own – if it were not, life would never have arisen in it to make our universe – our universe must also be fine tuned. Another possible explanation for the fine tuning is that the makers of our universe actually engineered our universe to have laws that promoted the evolution of intelligent life.
According to Harrison, the mystery of why the universe appears designed for life has a straightforward solution: at a fundamental level it was designed for life. However, and this is Harrison's novel twist, it was designed not by God – a Supreme Being – but by superior beings. Angels, if you like. "Intelligent life takes over universe-making business," says Harrison. "Consequently, the creation of the universe drops out of the religious sphere and becomes amenable to science."
Crucial to Harrison's reasoning is the assumption that it is possible to make a universe. Bizarre as it seems, this is not science fiction. The recipe was discovered independently around 1980 by Alexei Starobinsky in what was then the Soviet Union and Alan Guth in America. In their "inflationary" picture, our Universe "inflated" from a super-dense "seed" of matter, perhaps only a thousandth of a gram. This prompted Guth to suggest that a universe might be made in the laboratory. Simply take a seed of matter and squeeze it to the extraordinary density that once triggered the inflation of our universe. This will make a black hole. According to Guth, the super-dense interior will inflate – not in our universe, but in a bubble-like space-time connected to our own by the "umbilical cord" of the hole. This cord is unstable. When it snaps, a baby universe will be born. "The practical details are not important," says Harrison. "The important thing is that if beings of our limited intelligence can dream up wild, yet seemingly plausible, schemes for making universes, beings of much higher intelligence might know theoretically and technically how to do it."
Recreating the conditions of the first split-second of the universe is way beyond our capabilities. But it may not be impossible. "It's conceivable that more intelligent beings – perhaps even our own descendants in the far future – might possess not only the knowledge, but also the technology to build universes," says Harrison.
But why would they want to? Perhaps, says Harrison, simply to see what happens. There may be beings so advanced that their children make universes in the same way human children make figures out of plasticine. Another possibility, says Harrison, is that an advanced civilisation, out of a spirit of altruism, might make new universes that are ever more hospitable for life.
The observable universe contains about 10 billion galaxies. If, during the lifetime of each, a single civilisation emerges which makes a new universe – a modest figure considering our galaxy has 200 billion suns – then our universe reproduces 10 billion times. Furthermore, if intelligent life in each galaxy of each daughter universe repeats the ultimate experiment just once, the result is 10 billion times 10 billion granddaughter universes. Life-bearing universes could very quickly come to dominate the multiverse.
Einstein famously said: "The most incomprehensible thing about the universe is that it is comprehensible." According to Harrison, the explanation is that it was created by comprehensible beings – beings far in advance of us but basically like ourselves. Intelligent, but also intelligible. They made our universe to be like theirs, and their universe was in turn understandable. After all, they had to have the understanding to manipulate it and make a new universe.
A difficulty with Harrison's vision is that if our universe was created by superior beings in another universe, and theirs in turn was created by superior beings in an earlier universe and so on, who or what created the first universe? One possibility, admits Harrison, is God. But he distinguishes between his idea and the religious view. "In my scheme, God starts things," he says. "Thereafter, superior beings take over the creation of further universes." Another possibility is that in the beginning there was a large ensemble of universes, each with its own random variant of the laws of physics. Most of the universes were dead and uninteresting. But, by chance, the conditions in at least one – the intelligent "mother universe" – were right for life. "Thereafter, intelligent universes come to dominate the ensemble, since they alone reproduce," says Harrison.
But if a Supreme Being made the first universe, who or what made the Supreme Being? And if everything began with a mostly-dead ensemble of universes containing the intelligent mother universe, how did that come about? "Perhaps the supreme being occupied another universe created by an even higher form of intelligence, and perhaps the initial ensemble consisted of botched and bungled creations by a sorcerer's apprentice in another universe," says Harrison.
One thing follows automatically from Harrison's vision. If humanity avoids destruction and survives into the far future, one day our descendants will have to make an important decision: whether or not to become parents.
The writer's book, 'The Universe Next Door: 12 mind-blowing ideas from the cutting edge of science', is published by Headline, price £14.99
Radical science: did angels create the universe?
A theory that claims that it might be possible to make universes in the laboratory may not be as far-fetched as it sounds, says Marcus Chown
15 March 2002
The ultimate experiment is about to begin. On a cold, lonely moon, shrouded in purple-pink fog, a sentient ocean marshals the energy of a galaxy and focuses it on to a tiny mote of matter. A hundred billion stars flicker and dim. The air above the ocean sizzles and catches fire. Crushed by stupendous energies, the mote twists and bucks and, with a violent shudder, implodes. Elsewhere – in another space, another time – a searing-hot fireball explodes out of nothingness and begins to expand and cool. The ultimate scientific experiment has produced the ultimate experimental result: the birth of a new universe.
Could our universe have been born in such a way? According to Edward Harrison, it's a real possibility. "Our universe could easily be the outcome of an experiment carried out by a superior intelligence in another universe," says Harrison, a British physicist, formerly of the University of Massachusetts at Amherst.
Why suggest such an outlandish thing? Because it sheds light on a deep puzzle: why the laws of physics appear "fine tuned" for our existence. Even slight deviations in the laws would result in a universe devoid of stars and life. If, for instance, the force of gravity were just a few per cent weaker it could not squeeze and heat the matter inside stars to the millions of degrees necessary to trigger sunlight-generating nuclear reactions. If gravity were only a few per cent stronger, however, it would heat up stars, causing them to consume their fuel faster. They would not exist for the billions of years needed for evolution to produce intelligence.
This kind of fine tuning is widespread. One possible explanation is that the universe was "designed" by God. Some scientists accept this, but "unfortunately, it terminates further scientific enquiry", says Harrison. The other possibility is that the universe is the way it is because, if it were not, we would not be here to notice. According to this topsy-turvy reasoning known as the "anthropic principle", it is unsurprising that we find ourselves in a universe that is fine tuned for the existence of galaxies, stars and life. We could hardly have evolved in a universe that was not.
The anthropic principle leads to the idea that our universe is one of countless others. In each universe of this "multiverse", forces like gravity have different strengths. An unavoidable consequence, however, is that most universes lack the special conditions needed for the birth of galaxies, stars, planets and so on. "There will be countless lifeless universes," says Harrison. "This is waste on a truly cosmic scale."
But in cosmology, as in politics, there may be a third way. According to Harrison, the multiverse could be far from a wasteland. It could be dominated by universes with galaxies and stars and life. The prerequisite is that life-bearing universes have a special ability: the ability to reproduce. Specifically, Harrison is suggesting that intelligent life actually makes new universes. "If so, then in offspring universes which are fit for life, new life evolves to a high level of intelligence, then creates further universes," says Harrison.
In Harrison's scheme, dubbed the "natural selection of universes", the laws of physics most suited for the emergence and evolution of life are naturally selected by life itself. The origin of our universe is explained. It was created by super-intelligent beings living in another universe.
If Harrison is right, the fine tuning of the laws of physics has two possible explanations. New universes could inherit the characteristics of their cosmic parents, as children inherit the characteristics of their parents. Small "genetic variations" in the laws between generations would ensure that new universes were not carbon copies of their predecessors. It follows that since the parent of our universe was fine tuned for life and similar to our own – if it were not, life would never have arisen in it to make our universe – our universe must also be fine tuned. Another possible explanation for the fine tuning is that the makers of our universe actually engineered our universe to have laws that promoted the evolution of intelligent life.
According to Harrison, the mystery of why the universe appears designed for life has a straightforward solution: at a fundamental level it was designed for life. However, and this is Harrison's novel twist, it was designed not by God – a Supreme Being – but by superior beings. Angels, if you like. "Intelligent life takes over universe-making business," says Harrison. "Consequently, the creation of the universe drops out of the religious sphere and becomes amenable to science."
Crucial to Harrison's reasoning is the assumption that it is possible to make a universe. Bizarre as it seems, this is not science fiction. The recipe was discovered independently around 1980 by Alexei Starobinsky in what was then the Soviet Union and Alan Guth in America. In their "inflationary" picture, our Universe "inflated" from a super-dense "seed" of matter, perhaps only a thousandth of a gram. This prompted Guth to suggest that a universe might be made in the laboratory. Simply take a seed of matter and squeeze it to the extraordinary density that once triggered the inflation of our universe. This will make a black hole. According to Guth, the super-dense interior will inflate – not in our universe, but in a bubble-like space-time connected to our own by the "umbilical cord" of the hole. This cord is unstable. When it snaps, a baby universe will be born. "The practical details are not important," says Harrison. "The important thing is that if beings of our limited intelligence can dream up wild, yet seemingly plausible, schemes for making universes, beings of much higher intelligence might know theoretically and technically how to do it."
Recreating the conditions of the first split-second of the universe is way beyond our capabilities. But it may not be impossible. "It's conceivable that more intelligent beings – perhaps even our own descendants in the far future – might possess not only the knowledge, but also the technology to build universes," says Harrison.
But why would they want to? Perhaps, says Harrison, simply to see what happens. There may be beings so advanced that their children make universes in the same way human children make figures out of plasticine. Another possibility, says Harrison, is that an advanced civilisation, out of a spirit of altruism, might make new universes that are ever more hospitable for life.
The observable universe contains about 10 billion galaxies. If, during the lifetime of each, a single civilisation emerges which makes a new universe – a modest figure considering our galaxy has 200 billion suns – then our universe reproduces 10 billion times. Furthermore, if intelligent life in each galaxy of each daughter universe repeats the ultimate experiment just once, the result is 10 billion times 10 billion granddaughter universes. Life-bearing universes could very quickly come to dominate the multiverse.
Einstein famously said: "The most incomprehensible thing about the universe is that it is comprehensible." According to Harrison, the explanation is that it was created by comprehensible beings – beings far in advance of us but basically like ourselves. Intelligent, but also intelligible. They made our universe to be like theirs, and their universe was in turn understandable. After all, they had to have the understanding to manipulate it and make a new universe.
A difficulty with Harrison's vision is that if our universe was created by superior beings in another universe, and theirs in turn was created by superior beings in an earlier universe and so on, who or what created the first universe? One possibility, admits Harrison, is God. But he distinguishes between his idea and the religious view. "In my scheme, God starts things," he says. "Thereafter, superior beings take over the creation of further universes." Another possibility is that in the beginning there was a large ensemble of universes, each with its own random variant of the laws of physics. Most of the universes were dead and uninteresting. But, by chance, the conditions in at least one – the intelligent "mother universe" – were right for life. "Thereafter, intelligent universes come to dominate the ensemble, since they alone reproduce," says Harrison.
But if a Supreme Being made the first universe, who or what made the Supreme Being? And if everything began with a mostly-dead ensemble of universes containing the intelligent mother universe, how did that come about? "Perhaps the supreme being occupied another universe created by an even higher form of intelligence, and perhaps the initial ensemble consisted of botched and bungled creations by a sorcerer's apprentice in another universe," says Harrison.
One thing follows automatically from Harrison's vision. If humanity avoids destruction and survives into the far future, one day our descendants will have to make an important decision: whether or not to become parents.
The writer's book, 'The Universe Next Door: 12 mind-blowing ideas from the cutting edge of science', is published by Headline, price £14.99