Strung up

The recent discovery of two lookalike galaxies has led physicists one step closer to finding the ultimate theory of everything, says Marcus Chown

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.

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 dimensions. 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 Études 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)

Suggested Topics
PROMOTED VIDEO
News
ebookA unique anthology of reporting and analysis of a crucial period of history
Sport
Ray Whelan was arrested earlier this week
Arts and Entertainment
In a minor key: Keira Knightley in the lightweight 'Begin Again'
film
Arts and Entertainment
Celebrated children’s author Allan Ahlberg, best known for Each Peach Pear Plum
books
News
peopleIndian actress known as the 'Grand Old Lady of Bollywood' was 102
News
Wayne’s estate faces a claim for alleged copyright breaches
peopleJohn Wayne's heirs duke it out with university over use of the late film star's nickname
Independent
Travel Shop
the manor
Up to 70% off luxury travel
on city breaks Find out more
santorini
Up to 70% off luxury travel
on chic beach resorts Find out more
sardina foodie
Up to 70% off luxury travel
on country retreats Find out more
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Business Systems Analyst (Retail)

£30000 - £35000 Per Annum Up to 20% bonus: Clearwater People Solutions Ltd: An...

Head of Digital Marketing,London

To £58k Contract 12 months: Charter Selection: Major household name charity se...

Lead Hand - QC

competitive: Progressive Recruitment: Lead Hand - QCProgressive are recruiting...

Technical Manager / Lead - Mechanical.

£43000 - £45000 per annum + competitive: Progressive Recruitment: A leading Br...

Day In a Page

A History of the First World War in 100 Moments: Peace without magnanimity - the summit in a railway siding that ended the fighting

A History of the First World War in 100 Moments

Peace without magnanimity - the summit in a railway siding that ended the fighting
Scottish independence: How the Commonwealth Games could swing the vote

Scottish independence: How the Commonwealth Games could swing the vote

In the final part of our series, Chris Green arrives in Glasgow - a host city struggling to keep the politics out of its celebration of sport
Out in the cold: A writer spends a night on the streets and hears the stories of the homeless

A writer spends a night on the streets

Rough sleepers - the homeless, the destitute and the drunk - exist in every city. Will Nicoll meets those whose luck has run out
Striking new stations, high-speed links and (whisper it) better services - the UK's railways are entering a new golden age

UK's railways are entering a new golden age

New stations are opening across the country and our railways appear to be entering an era not seen in Britain since the early 1950s
Conchita Wurst becomes a 'bride' on the Paris catwalk - and proves there is life after Eurovision

Conchita becomes a 'bride' on Paris catwalk

Alexander Fury salutes the Eurovision Song Contest winner's latest triumph
Pétanque World Championship in Marseilles hit by

Pétanque 'world cup' hit by death threats

This year's most acrimonious sporting event took place in France, not Brazil. How did pétanque get so passionate?
Whelks are healthy, versatile and sustainable - so why did we stop eating them in the UK?

Why did we stop eating whelks?

Whelks were the Victorian equivalent of the donor kebab and our stocks are abundant. So why do we now export them all to the Far East?
10 best women's sunglasses

In the shade: 10 best women's sunglasses

From luxury bespoke eyewear to fun festival sunnies, we round up the shades to be seen in this summer
Germany vs Argentina World Cup 2014: Lionel Messi? Javier Mascherano is key for Argentina...

World Cup final: Messi? Mascherano is key for Argentina...

No 10 is always centre of attention but Barça team-mate is just as crucial to finalists’ hopes
Siobhan-Marie O’Connor: Swimmer knows she needs Glasgow joy on road to Rio

Siobhan-Marie O’Connor: Swimmer needs Glasgow joy on road to Rio

18-year-old says this month’s Commonwealth Games are a key staging post in her career before time slips away
The true Gaza back-story that the Israelis aren’t telling this week

The true Gaza back-story that the Israelis aren’t telling this week

A future Palestine state will have no borders and be an enclave within Israel, surrounded on all sides by Israeli-held territory, says Robert Fisk
A History of the First World War in 100 Moments: The German people demand an end to the fighting

A History of the First World War in 100 Moments

The German people demand an end to the fighting
New play by Oscar Wilde's grandson reveals what the Irish wit said at his trials

New play reveals what Oscar Wilde said at trials

For a century, what Wilde actually said at his trials was a mystery. But the recent discovery of shorthand notes changed that. Now his grandson Merlin Holland has turned them into a play
Can scientists save the world's sea life from

Can scientists save our sea life?

By the end of the century, the only living things left in our oceans could be plankton and jellyfish. Alex Renton meets the scientists who are trying to turn the tide
Richard III, Trafalgar Studios, review: Martin Freeman gives highly intelligent performance

Richard III review

Martin Freeman’s psychotic monarch is big on mockery but wanting in malice