Galileo and the Dolphins

by Adrian Berry

  Yet the real beauty of the heavens comes from celestial objects that do not yet exist! These are the great clouds of dust and gas - mostly hydrogen - the source material of stars which are yet to be and the relics of stars that once were. One such is the Vela supernova remnant. It exploded about 11,000 years ago and may have inspired our Ice Age ancestors to wonder at the heavens.

  Through a Wormhole to the Stars?

  Through hyperspace, that unimaginable region that was neither space nor time, matter nor energy, something nor nothing, one could traverse the length of the galaxy in the interval between two neighbouring instants of time.

  , The Foundation Trilogy

  Few science fiction novels dealing with interstellar adventure would make much sense without the ‘Jumps’ though ‘hyperspace’ that enable spaceships to treat the cosmos as though it were little more than the London Underground. Until recently, however, physicists have tended to dismiss such journeys as fantasy.

  But how convenient they would be! Defying the rule that forbids faster-than-light journeys, our descendants could travel to the nearest star system to the sun Alpha Centauri, within weeks, and colonize all the habitable planets in our Milky Way galaxy in a few tens of millennia.

  Hyperspace travel may not be fantasy after all. An article in the New Scientist reports that great theoretical progress has been made in the subject since 1989 when two physicists, and Kip Thorne, published a paper that was inspired by an effort to help make his novel Contact sound plausible.

  The keys to the matter are ‘wormholes’ in the structure of space-time, which supposedly link up regions of space in a tunnel-system of unimaginable complexity. According to the equations of ’s 1916 general theory of relativity, space-time has a solid structure. Massive objects such as stars and planets create the space and time that surround them.

  The entrances to these tunnels exist everywhere, but and here is the catch - their diameter is so small that they would make atoms seem as large as planets. They are as tiny as it is physically possible for anything to be, no wider than a billionth of a trillionth of a trillionth of a centimetre.

  There are therefore three ways to imagine hyperspace travel. One is to shrink the spaceship and crew down to this size (and enlarge them again when they re-emerge into ordinary space), which seems a hopeless proposition. The second is to enlarge a wormhole to reasonable size by some exotic mechanism, such as repulsive - as opposed to attractive gravity, which seems very difficult. And the third, proposed by , of Princeton University, and , of Washington State University at Pullman, is to search for reasonable-sized wormholes which may already exist.

  This idea comes from the history of the universe itself. When it was created by the Big Bang some 15 billion years ago, its size was infinitessimal. How, then, did it become so vast? The answer accepted by many physicists is ‘inflation’ which, within a few fractions of a second, used repulsive gravity to expand the cosmos to its present size. This tremendous enlargement, which made everything bigger, might also have enlarged primordial wormholes, from the sub-sub-microscopic size that we today imagine them, to diameters of thousands, if not millions of miles.

  The next step is to find such a wormhole. This requires little extra effort to what many astronomers routinely do to monitor thousands of millions of stars for many years to see if their light fluctuates in a particularly unusual manner.

  Starlight fluctuates in many ways, from many different causes, but believes that a wormhole that passed between a star and ourselves would make the star shine in a highly peculiar way. He calculates that if held apart by repulsive gravity (as a large-sized wormhole would have to be) it would force the light of the star behind it to emit ‘twin spikes’ of light with a dimness in the middle. Existing stellar images could easily enable us to seek such exotically shining stars.

  However, wormhole tunnels, whether large or small, are likely to be extremely complex. Theory predicts that travelling through them will be no easy matter, for they will divide and sub-divide in a manner vastly more intricate than the most cunningly dug catacomb. There will be junction upon junction, loop upon loop, until the chances of not getting lost becomes infinitesimal.

  Nobody, in short, has the slightest idea how one could navigate through such a labyrinth. As far as we can understand wormholes today, there would be no means of knowing not only where we would emerge, but even when.

  Some theories (but not all) predict that the travellers would go backwards in time. They would then have to re-emerge into ordinary space in another universe since it would be impossible to return to the past of this one. Why? Because they would then be able to murder their own parents before they met, creating a forbidden paradox. (See The Tunnel of Time, p. 240.)

  Starship designers will therefore have to decide whether to stick to ordinary space and comparatively slow speeds, or to attempt to exploit a science that may prove prohibitively complex.

  The Biggest Blasts

  For half a century, physicists have been trying to build more destructive nuclear bombs. Their efforts are puny compared with those of nature, which creates explosions that could shatter the Solar System. These are supernovae, the colossal blasts in which certain kinds of stars end their lives, blazing forth for several months with the light of many billions of suns.

  Until a few months ago, astrophysicists had only the most general ideas of why supernovae explode. But now detailed studies with a super-computer, reported recently to the American Astronomical Society, show precisely how these tremendous detonations occur.

  The moment of destruction comes when a star at least eight times more massive than the Sun has exhausted its nuclear fuel. It started off, billions of years before, being largely composed of hydrogen, the lightest of gases. Through the eons, in a series of thermonuclear reactions, the hydrogen is converted into one element after another, each heavier than the last, including diamonds, otherwise known as carbon. Finally only iron remains which, being entirely stable, cannot be converted into anything else.

  These reactions can be roughly described by my verse:

  Hydrogen to helium will give you a suntan,

  Helium to carbon will make you very rich.

  Carbon to silicon does nothing in particular,

  But silicon to iron will blow you to bits.

  ‘The explosion is triggered within a fraction of a second in a mechanism that has three distinct stages,’ said , of the Los Alamos National Laboratory in New Mexico.

  The first of these comes when the core of the giant star is entirely composed of iron. No longer able to hold itself apart by nuclear ‘burning’, it collapses on itself. The outer layer of the core crashes down upon the inner. No less than 3,000 trillion trillion tons of iron slam together at speeds of 322 million kilometres per hour. Within a tenth of a second, the core has shrunk from a diameter of thousands of kilometres to one of about 20.

  At this stage, the core is still surrounded by an ‘envelope’ of gases left over from previous reactions. Part of the envelope now begins to ‘rain’ down on the core. Within this gaseous rain are almost massless particles, neutrinos and anti-neutrinos. These particles are so tiny that they do not normally collide with atoms at all. In theory, they could travel through a solid wall of lead ten light-years thick without hitting anything. But not so with this super-compressed iron core. It is so dense that a piece of it the size of a sugar cube weighs ten billion tons.

  The anti-neutrinos now collide with iron atoms. Everywhere in the core, are explosions of matter and anti-matter in which ’s equation E=mc works with 100 per cent efficiency. The temperature of the core rises to several hundred billion degrees. But the remainder of the gaseous envelope still surrounds it. The core, bursting with energy, is like a pressure cooker with no safety valve which finally bursts the envelope, and the star explodes with cataclysmic violence.

  Yet supernovae are not entirely destructive. Religiously minded people might think them part of God’s plan. For without them there would be
no chance of life anywhere.

  Only the relatively useless elements of hydrogen and helium are made without them. Supernovae spew out into space all the heavier elements that make up our bodies and needs.

  They give us oxygen to breathe, carbon for our plant life, calcium for our bones, nitrogen for our agriculture, iron for our machines, silicon for our computer chips, neon for our advertizing and nickel for our coins. The next star likely to explode as a supernova is the red giant Betelgeuse, which is at the safe distance of 300 light-years away. ‘For a few months Betelgeuse will be brighter than the full Moon,’ said Herant. ‘It will also be more dangerous to look at than the Moon because so much brilliant light will be concentrated in a single point source.’

  Betelgeuse will not explode in the immediate future. Supernovae explode at a rate of approximately one per galaxy per century. But since there are at least 100 billion galaxies, they must be exploding, far beyond the vision of even our most powerful telescopes, at a rate of about one per second. We may live in a much more violent - and life-producing - universe than we imagine.

  The Tunnel of Time

  Just to conceive of travelling into the past, like the hero of ’s novel, The Time Machine, you have to take leave of your senses.

  Well, your common sense at least. Because to do so you must enter a world of many different realities where, at the end of the day, you bump up against that familiar but terrifying entity called a black hole.

  ‘Common sense may rule out time travel, but the laws of physics do not,’ say and , two Oxford physicists in Scientific American. ‘If it is impossible, then the reason has yet to be discovered. It is incumbent on anyone who still wants to reject the idea to come up with some new scientific argument.’

  There is no great obstacle to travelling into the future. One could put oneself into a super-sophisticated deep-freeze with instructions to be awakened in 100 or 1,000 years, or travel in a spaceship almost at the speed of light, in which time would slow down and where, at the end of the journey, one would be at a period in the future dictated by the speed at which one had travelled. But in no circumstances, so it has been believed until now, could one reverse direction like Wells’s Time Traveller. For that would be travel into the past.

  The rule has been that one can observe the past but that interference with it is forbidden, a rule easily obeyed by watching an old newsreel. Interference with the past, it was said, would create an impossible paradox. A man could go back and murder his parents before they met, in which case he would not only cease to exist but cease ever to have existed. But if he never existed, who committed the murders?

  This is a reason why it is impossible to travel faster than light. The closer a spaceship gets to that speed, the slower time inside it runs. At the speed of light itself, time would stop altogether. Faster than that it would run backwards - a scenario which recalls the verses:

  There was a young lady called Bright,

  Who travelled much faster than light.

  She started one day

  In the relative way

  And returned on the previous night.

  The lady was but not bright,

  And she joined in next day in the flight;

  So then two made the date,

  And then four and then eight,

  And her spouse got the hell of a fright.

  All these exist because each, on returning home, meets an untravelled version of herself. But what happens if the first traveller tells her stay-at-home clone that the journey was disagreeable and she should cancel her ticket? The traveller would both exist and not exist at the same time. Or perhaps the universe, its laws having been violated, would quietly disappear.

  This view correctly represents what Deutsch and Lockwood call the ‘classical view’, which prevailed until 1957, when the late Hugh Everett proposed his famous ‘Many Worlds theorem’ of quantum mechanics, suggesting that at every instant since the birth of the universe, reality has been branching into different realities.

  There is one reality in which your parents married, and countless others in which they never met. You can travel back to meet them but because, by the very act of meeting them, you can prevent their marriage, they cannot be the parents that gave birth to you. If they were you would not exist. They will be two other people, in another reality, subtly different from this one. Paradox is thus avoided.

  But how is it possible to travel backwards in time into a different reality? It is not just a matter of pressing a few levers on a complicated console like Wells’s hero.

  According to Amos Ori, a physicist at the California Institute of Technology, it can be done only by going through a black hole. He has shown that a spaceship trapped inside a fast-rotating black hole would not be crushed by overwhelming gravitational forces. The ‘singularity’ at the centre of the hole would be opened out by centrifugal force until it resembled a ‘ring’, the gateway to a tunnel through which the spaceship could pass.

  ‘In a black hole, the warping of the fabric of space and time is so intense that the fabric tears itself apart,’ says Deutsch. ‘It rejoins itself, but in a different way, so a spaceship that emerges through that tunnel will travel backwards in time. It will be in another reality.’

  It used to be supposed that no spaceship could make this journey, because the incoming light being trapped from outside the hole would be infinitely strong and would ‘fry’ the spaceship. But Ori has shown that this would not happen. The strength of the pursuing light would be too feeble to harm the spaceship. ‘We are still not sure that our models of the interiors of fast-rotating black holes are correct, and whether they do create navigable ‘rings’. But if they do, then the exits through the tunnel will be exits backward in time and into another reality.’

  So what is the use of time travel? Well, it could make international diplomacy much easier. ‘Suppose,’ says Deutsch, ‘that two rival civilizations were struggling for possession of a galaxy. Instead of going to war, they could agree to go into separate realities and each would then have the galaxy to themselves.’

  Moons Beyond Ours

  Imagine walking on the most slippery ice possible, without dirt or rubble to give your feet a grip. Day and night, the inky black sky is filled with countless stars, while in one direction, just beyond the horizon, rises a curved yellow curtain so huge that it seems to fill the sky.

  The curtain is the edge of the ringed planet Saturn, and we are standing on its moon Enceladus, whose crust seems to be made entirely of very pure ice.

  Enceladus is one of the innumerable moons, planets, comets and asteroids of our Solar System that fill a spectacular paperback picture book, The Grand Tour: A Traveller’s Guide to the Solar System, by Ron Miller and William K. Hartmann.

  ‘What grandeur, desolation, power, silence, resources or loneliness do these places offer?’ ask the authors, presenting us with the vast retinues of worlds and worldlets that orbit Saturn, the ‘lord of the rings’, and its giant companion planets.

  The crew of an alien spacecraft visiting the Solar System would first encounter , normally the Sun’s most distant world, from where the Sun is just a bright star, a pinpoint of light amid the Milky Way’s star-clouds. It would be hard even to realize that the Sun is its parent star.

  , whose years last 248 of ours, is an infinitely lonely place, so cold that its atmosphere is frozen as hard as steel. From its surface, the only large visible body is its moon Charon, so close that it appears in the sky 17 times the apparent size of Earth’s moon.

  Travelling sunwards from , the aliens would next visit and its large moon, Triton. Its icy surface lit with a faint blue light by the far-off Sun, has the mysterious phenomenon - which no other moon or world is known to possess - of thick plumes of smoke shooting out from its interior. Perhaps only visiting astronauts will discover one day what causes them.

  Sunwards again towards Miranda, one of the smallest but by far the most interesting moons of Uranus. The larger moons of Uranus are cratered an
d quite dull, but Miranda, with her parent planet swelling above like a blue-green balloon, has a unique phenomenon of her own, a not quite vertical cliff known as the Great Wall that rises sheer to a height of many kilometres. Great boulders falling down it, say the book’s authors, ‘would take many minutes to reach the bottom, where they would roll on to the valley at the speed of fast trains’.

  Saturn has a moon even stranger than Enceladus. This is Iapetus, the entrance to hyperspace in ’s novel 2001. To telescopes on Earth, it is visible when on one side of Saturn, but vanishes when it passes to the other. This is because it has two ‘faces’. One is permanently icy while the other, which always faces Saturn, is inexplicably black.

  But the most bizarre, and also most violent, world in the Solar System is undoubtedly Jupiter’s moon Io. It experiences two and a half hours of solar eclipse each day as the Sun goes behind Jupiter. With dozens of simultaneously erupting volcanoes, it is literally turning itself inside out, its surface being buried ever deeper beneath debris as new material is spewed out from its interior. These eruptions are caused by the proximity of massive Jupiter - only 100,000 kilometres away - whose gravitational field is perpetually convulsing its interior, creating volcanoes at random.

  What will be the fate of these far-off worlds? once suggested that ice-covered Enceladus might eventually be propelled to Mars so that its water could irrigate that dry planet.

  But smashing up one of the most beautiful of worlds in an infinitely wonderful Solar System may seem to our descendants too great an environmental crime.

  Part Five: STRANGE BELIEFS

  Newton, ‘Rapist’ of the Universe