Wow! Like an SF novel by Gregory Benford!
> Finding the Ultimate Theory of Everything
> Could two lookalike galaxies, barely a whisker apart in the night sky,
> herald a revolution in our understanding of fundamental physics? Some
> physicists believe that the two galaxies are the same - its image has been
> split into two, they maintain, by a "cosmic string"; a San Andreas Fault
> in the very fabric of space and time.
> If this interpretation is correct, then CSL-1 - the name of the curious
> double galaxy - is the first concrete evidence for "superstring theory":
> the best candidate for a "theory of everything", which attempts to
> encapsulate all the phenomena of nature in one neat set of equations.
> Superstring theory views the fundamental building blocks of all matter -
> the electrons and quarks that make up the atoms in our bodies - as ultra-
> tiny pieces of vibrating "string". And, just as different vibrations of a
> violin string correspond to different musical notes, different vibrations
> of this fundamental string correspond to different fundamental particles.
> The problem with string theory is that the strings are fantastically
> smaller than atoms and, therefore, impossible to detect in any conceivable
> laboratory experiment. But recently, physicists realised that the extreme
> conditions that existed in the early universe could have spawned
> enormously big strings. It is one of these "cosmic superstrings" that some
> believe is passing between the Earth and CSL- 1, and, in the process,
> creating the curious double image of the galaxy.
> The realisation that big strings are possible has come from exploring the
> most esoteric implications of the theory. For instance, the only way
> strings can vibrate in enough different ways to mimic all the known
> fundamental particles is if the strings vibrate in a space-time of 10
> Since we appear to live in a universe with a mere four dimensions - three
> of space and one of time - string theorists have been forced to postulate
> the existence of six extra space dimensions "rolled up" so small we have
> overlooked them.
> The existence of the extra dimensions opens up the possibility of more
> complex objects. In addition to strings, which extend in only one
> dimension, it is possible to have objects with two, three or more
> dimensions. These are dubbed branes, or p-branes, where the "p" denotes
> the number of their dimensions.
> This has raised the possibility that our universe is a three- brane - a
> three- dimensional "island", adrift in a 10-dimensional space. And, if it
> is, it may not be alone. Some have suggested that the big bang was caused
> when another brane collided with our own 13.7 billion years ago (See
> "Highly strung", The Independent, 7 July 2004).
> Crucially, a collision between branes creates strings - both within each
> brane and as a kind of spaghetti connecting the branes. And these can be
> stretched to cosmic dimensions to make cosmic superstrings. "Cosmic
> strings turn out to be pretty much inevitable in the brane scenario," says
> Tom Kibble of Imperial College in London.
> Cosmic superstrings would be under enormous tension, like a geological
> fault in the Earth's crust. But, being free to move, they would attempt to
> relieve the tension by lashing about through space at almost the speed of
> light. But their most interesting property is the effect they have on
> their surroundings. "A string distorts the space around it in a very
> distinctive way," says Kibble.
> One way to visualise this is to imagine a string coming up through this
> page. Imagine cutting from the paper a narrow triangle whose tip is at the
> string, then gluing the paper back together again. The result will be a
> shallow cone centred on the string.
> Because of this distortion of space, if a string passes between us and a
> distant galaxy - a giant collection of stars like our Milky Way - the
> light of the galaxy can come to Earth along two possible routes: one on
> either side of the string. Consequently, there will be two identical
> images of the galaxy only a whisker apart - which is exactly what is seen
> in the case of CSL-1.
> CSL-1 was discovered by a team led by Mikhail Sazhin of Capodimonte
> Astronomical Observatory in Naples and the Sternberg Astronomical
> Institute in Moscow. They christened it Capodimonte- Sternberg Lens
> Candidate 1, which is where the CSL-1 comes from. "It looks like the
> signature of a string to me," says Kibble. "However, it is always possible
> we are seeing two galaxies that just happen to look surprisingly similar."
> This is the view of the sceptics. "CSL- 1 is most likely just a pair of
> galaxies that happened to be close together on the sky," says Abraham Loeb
> of the Harvard-Smithsonian Centre for Astrophysics. "We know of many close
> pairs of galaxies in the local universe, including our own Milky Way and
> Andromeda." But others are keeping their fingers crossed that Loeb is
> wrong. "I am hoping nature won't have played such a trick on us," says
> Tanmay Vachaspati of Case Western Reserve University in Ohio.
> If CSL-1 was the only piece of evidence for a cosmic superstring it might
> be easy to brush it under the carpet. But it isn't. There is the "double
> quasar" Q0957+561A,B. Discovered at Jodrell Bank near Manchester in 1979,
> the two images of a super-bright galaxy, or quasar, are formed by a galaxy
> lying between the quasar and the Earth.
> The gravity of the intervening galaxy bends the light of the quasar so
> that it follows two distinct paths to Earth, creating two images of
> unequal brightness. Crucially, the two light paths are of different
> lengths and so the light takes a different time to travel along each. In
> fact, astronomers find that when one image brightens, the other image
> brightens 417.1 days later.
> But this is not what has been found by a team of astronomers from the US
> and the Ukraine, led by Rudolph Schild of the Harvard- Smithsonian Centre
> for Astrophysics. When they studied the two images, they noticed that,
> between September 1994 and July 1995, the two images brightened and faded
> at the same time - with no time delay The two images did this four times,
> on each occasion for a period of about 100 days.
> The only way Schild and his colleagues can make sense of this behaviour is
> if, between September 1994 and July 1995, something moved across our line
> of sight to the quasar, simultaneously affecting the light coming down
> both paths to the Earth. The only thing that fits the bill, they claim, is
> a vibrating loop of cosmic string moving across the line of sight at about
> 70 per cent of the speed of light.
> To oscillate once every 100 days or so, the loop has to be very small - no
> bigger than 1 per cent of the distance between the Sun and the nearest
> star. And Schild and his colleagues calculate that the string must be
> remarkably close to us - well within our Milky Way galaxy.
> Most physicists remain sceptical about the evidence for cosmic
> superstrings. If the case is to be strengthened, it will be necessary to
> find more candidates like CSL-1 and Q0957+561A,B. Alternatively, it will
> be necessary to detect the "gravitational waves" coming from a string.
> These are ripples in the fabric of space, much like the ripples which
> spread out on a pond from an impacting raindrop.
> Strings are travelling very fast. If they get a kink in them, it is
> possible for this part of the string to crack like a whip. The part
> producing the crack travels at almost the speed of light and should
> produce an intense burst of gravitational waves. As first pointed out by
> Thibault Damour of the Institut des Hautes etudes Scientifiques in Paris
> and Alex Vilenkin of Tufts Institute of Cosmology in the US, such signals
> could be detected in the next few years by Europe's Virgo detector or
> America's Laser Interferometric Gravitational-Wave Observatory.
> String theory has long been criticised as that which makes no observable
> predictions about the universe we live in. If the discovery of cosmic
> superstrings holds up, the theory may finally have connected with reality
> and the critics may at last be silenced.
> Marcus Chown is the author of `The Universe Next Door' (Headline)
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