In SUSY we trust: What the LHC is really looking for

AS DAMP squibs go, it was quite a spectacular one. Amid great pomp and ceremony - not to mention dark offstage rumblings that the end of the world was nigh - the Large Hadron Collider (LHC), the world's mightiest particle smasher, fired up in September last year. Nine days later a short circuit and a catastrophic leak of liquid helium ignominiously shut the machine down.

Now for take two. Any day now, if all goes to plan, proton beams will start racing all the way round the ring deep beneath CERN, the LHC's home on the outskirts of Geneva, Switzerland.

Nobel laureate Steven Weinberg is worried. It's not that he thinks the LHC will create a black hole that will engulf the planet, or even that the restart will end in a technical debacle like last year's. No: he's actually worried that the LHC will find what some call the "God particle", the popular and embarrassingly grandiose moniker for the hitherto undetected Higgs boson.

"I'm terrified," he says. "Discovering just the Higgs would really be a crisis."

Why so? Evidence for the Higgs would be the capstone of an edifice that particle physicists have been building for half a century - the phenomenally successful theory known simply as the standard model. It describes all known particles, as well as three of the four forces that act on them: electromagnetism and the weak and strong nuclear forces.

It is also manifestly incomplete. We know from what the theory doesn't explain that it must be just part of something much bigger. So if the LHC finds the Higgs and nothing but the Higgs, the standard model will be sewn up. But then particle physics will be at a dead end, with no clues where to turn next.

Hence Weinberg's fears. However, if the theorists are right, before it ever finds the Higgs, the LHC will see the first outline of something far bigger: the grand, overarching theory known as supersymmetry. SUSY, as it is endearingly called, is a daring theory that doubles the number of particles needed to explain the world. And it could be just what particle physicists need to set them on the path to fresh enlightenment.

So what's so wrong with the standard model? First off, there are some obvious sins of omission. It has nothing whatsoever to say about the fourth fundamental force of nature, gravity, and it is also silent on the nature of dark matter. Dark matter is no trivial matter: if our interpretation of certain astronomical observations is correct, the stuff outweighs conventional matter in the cosmos by more than 4 to 1.

Ironically enough, though, the real trouble begins with the Higgs. The Higgs came about to solve a truly massive problem: the fact that the basic building blocks of ordinary matter (things such as electrons and quarks, collectively known as fermions) and the particles that carry forces (collectively called bosons) all have a property we call mass. Theories could see no rhyme or reason in particles' masses and could not predict them; they had to be measured in experiments and added into the theory by hand.

These "free parameters" were embarrassing loose threads in the theories that were being woven together to form what eventually became the standard model. In 1964,Peter Higgs of the University of Edinburgh, UK, and François Englert and Robert Brout of the Free University of Brussels (ULB) in Belgium independently hit upon a way to tie them up.

That mechanism was an unseen quantum field that suffuses the entire cosmos. Later dubbed the Higgs field, it imparts mass to all particles. The mass an elementary particle such as an electron or quark acquires depends on the strength of its interactions with the Higgs field, whose "quanta" are Higgs bosons.

Fields like this are key to the standard model as they describe how the electromagnetic and the weak and strong nuclear forces act on particles through the exchange of various bosons - the W and Z particles, gluons and photons. But the Higgs theory, though elegant, comes with a nasty sting in its tail: what is the mass of the Higgs itself? It should consist of a core mass plus contributions from its interactions with all the other elementary particles. When you tot up those contributions, the Higgs mass balloons out of control.

The experimental clues we already have suggest that the Higgs's mass should lie somewhere between 114 and 180 gigaelectronvolts - between 120 and 190 times the mass of a proton or neutron, and easily the sort of energy the LHC can reach. Theory, however, comes up with values 17 or 18 orders of magnitude greater - a catastrophic discrepancy dubbed "the hierarchy problem". The only way to get rid of it in the standard model is to fine-tune certain parameters with an accuracy of 1 part in 1034, something that physicists find unnatural and abhorrent.
Three into one

The hierarchy problem is not the only defect in the standard model. There is also the problem of how to reunite all the forces. In today's universe, the three forces dealt with by the standard model have very different strengths and ranges. At a subatomic level, the strong force is the strongest, the weak the weakest and the electromagnetic force somewhere in between.

Towards the end of the 1960s, though, Weinberg, then at Harvard University, showed with Abdus Salam and Sheldon Glashow that this hadn't always been the case. At the kind of high energies prevalent in the early universe, the weak and electromagnetic forces have one and the same strength; in fact they unify into one force. The expectation was that if you extrapolated back far enough towards the big bang, the strong force would also succumb, and be unified with the electromagnetic and weak force in one single super-force (see graph).

In 1974 Weinberg and his colleagues Helen Quinn and Howard Georgi showed that the standard model could indeed make that happen - but only approximately. Hailed initially as a great success, this not-so-exact reunification soon began to bug physicists working on "grand unified theories" of nature's interactions.

It was around this time that supersymmetry made its appearance, debuting in the work of Soviet physicists Yuri Golfand and Evgeny Likhtman that never quite made it to the west. It was left to Julius Wess of Karlsruhe University in Germany and Bruno Zumino of the University of California, Berkeley, to bring its radical prescriptions to wider attention a few years later.

Wess and Zumino were trying to apply physicists' favourite simplifying principle, symmetry, to the zoo of subatomic particles. Their aim was to show that the division of the particle domain into fermions and bosons is the result of a lost symmetry that existed in the early universe.

According to supersymmetry, each fermion is paired with a more massive supersymmetric boson, and each boson with a fermionic super-sibling. For example, the electron has the selectron (a boson) as its supersymmetric partner, while the photon is partnered with the photino (a fermion). In essence, the particles we know now are merely the runts of a litter double the size (see diagram).

The key to the theory is that in the high-energy soup of the early universe, particles and their super-partners were indistinguishable. Each pair co-existed as single massless entities. As the universe expanded and cooled, though, this supersymmetry broke down. Partners and super-partners went their separate ways, becoming individual particles with a distinctive mass all their own.

Supersymmetry was a bold idea, but one with seemingly little to commend it other than its appeal to the symmetry fetishists. Until, that is, you apply it to the hierarchy problem. It turned out that supersymmetry could tame all the pesky contributions from the Higgs's interactions with elementary particles, the ones that cause its mass to run out of control. They are simply cancelled out by contributions from their supersymmetric partners. "Supersymmetry makes the cancellation very natural," says Nathan Seiberg of the Institute of Advanced Studies, Princeton.

That wasn't all. In 1981 Georgi, together with Savas Dimopoulos of Stanford University, redid the force reunification calculations that he had done with Weinberg and Quinn, but with supersymmetry added to the mix. They found that the curves representing the strengths of all three forces could be made to come together with stunning accuracy in the early universe. "If you have two curves, it's not surprising that they intersect somewhere," says Weinberg. "But if you have three curves that intersect at the same point, then that's not trivial."

This second strike for supersymmetry was enough to convert many physicists into true believers. But it was when they began studying some of the questions raised by the new theory that things became really interesting.

One pressing question concerned the present-day whereabouts of supersymmetric particles. Electrons, photons and the like are all around us, but of selectrons and photinos there is no sign, either in nature or in any high-energy accelerator experiments so far. If such particles exist, they must be extremely massive indeed, requiring huge amounts of energy to fabricate.

Such huge particles would long since have decayed into a residue of the lightest, stable supersymmetric particles, dubbed neutralinos. Still massive, the neutralino has no electric charge and interacts with normal matter extremely timorously by means of the weak nuclear force. No surprise then that it is has eluded detection so far.

When physicists calculated exactly how much of the neutralino residue there should be, they were taken aback. It was a huge amount - far more than all the normal matter in the universe.

Beginning to sound familiar? Yes, indeed: it seemed that neutralinos fulfilled all the requirements for the dark matter that astronomical observations persuade us must dominate the cosmos. A third strike for supersymmetry.

Each of the three questions that supersymmetry purports to solve - the hierarchy problem, the reunification problem and the dark-matter problem - might have its own unique answer. But physicists are always inclined to favour an all-purpose theory if they can find one. "It's really reassuring that there is one idea that solves these three logically independent things," says Seiberg.
Supersymmetry solves problems with the standard model, helps to unify nature's forces and explains the origin of dark matter

Supersymmetry's scope does not end there. As Seiberg and his Princeton colleague Edward Witten have shown, the theory can also explain why quarks are never seen on their own, but are always corralled together by the strong force into larger particles such as protons and neutrons. In the standard model, there is no mathematical indication why that should be; with supersymmetry, it drops out of the equations naturally. Similarly, mathematics derived from supersymmetry can tell you how many ways can you fold a four-dimensional surface, an otherwise intractable problem in topology.

All this seems to point to some fundamental truth locked up within the theory. "When something has applications beyond those that you designed it for, then you say, 'well this looks deep'," says Seiberg. "The beauty of supersymmetry is really overwhelming."

Sadly, neither mathematical beauty nor promise are enough on their own. You also need experimental evidence. "It is embarrassing," says Michael Dine of the University of California, Santa Cruz. "It is a lot of paper expended on something that is holding on by these threads."

Circumstantial evidence for supersymmetry might be found in various experiments designed to find and characterise dark matter in cosmic rays passing through Earth. These include the Cryogenic Dark Matter Search experiment inside the Soudan Mine in northern Minnesota and the Xenon experiment beneath the Gran Sasso mountain in central Italy. Space probes like NASA's Fermi satellite are also scouring the Milky Way for the telltale signs expected to be produced when two neutralinos meet and annihilate.

The best proof would come, however, if we could produce neutralinos directly through collisions in an accelerator. The trouble is that we are not entirely sure how muscular that accelerator would need to be. The mass of the super-partners depends on precisely when supersymmetry broke apart as the universe cooled and the standard particles and their super-partners parted company. Various versions of the theory have not come up with a consistent timing. Some variants even suggest that certain super-partners are light enough to have already turned up in accelerators such as the Large Electron-Positron collider - the LHC's predecessor at CERN - or the Tevatron collider in Batavia, Illinois. Yet neither accelerator found anything.

The reason physicists are so excited about the LHC, though, is that the kind of supersymmetry that best solves the hierarchy problem will become visible at the higher energies the LHC will explore. Similarly, if neutralinos have the right mass to make up dark matter, they should be produced in great numbers at the LHC.

Since the accident during the accelerator's commissioning last year, CERN has adopted a softly-softly approach to the LHC's restart. For the first year it will smash together two beams of protons with a total energy of 7 teraelectronvolts (TeV), half its design energy. Even that is quite a step up from the 1.96 TeV that the Tevatron, the previous record holder, could manage. "If the heaviest supersymmetric particles weigh less than a teraelectronvolt, then they could be produced quite copiously in the early stages of LHC's running," says CERN theorist John Ellis.

If that is so, events after the accelerator is fired up again could take a paradoxical turn. The protons that the LHC smashes together are composite particles made up of quarks and gluons, and produce extremely messy debris. It could take rather a long time to dig the Higgs out of the rubble, says Ellis.

Any supersymmetric particles, on the other hand, will decay in as little as 10-16seconds into a slew of secondary particles, culminating in a cascade of neutralinos. Because neutralinos barely interact with other particles, they will evade the LHC's detectors. Paradoxically, this may make them relatively easy to find as the energy and momentum they carry will appear to be missing. "This, in principle, is something quite distinctive," says Ellis.

So if evidence for supersymmetry does exist in the form most theorists expect, it could be discovered well before the Higgs particle, whose problems SUSY purports to solve. Any sighting of something that looks like a neutralino would be very big news indeed. At the very least it would be the best sighting yet of a dark-matter particle. Even better, it would tell us that nature is fundamentally supersymmetric.

There is a palpable sense of excitement about what the LHC might find in the coming years. "I'll be delighted if it is supersymmetry," says Seiberg. "But I'll also be delighted if it is something else. We need more clues from nature. The LHC will give us these clues."

11 November 2009 by Anil Ananthaswamy

Did a Time-Traveling Bird Sabotage the Collider?

Sometime on Nov. 3, the supercooled magnets in sector 81 of the Large Hadron Collider (LHC), outside Geneva, began to dangerously overheat. Scientists rushed to diagnose the problem, since the particle accelerator has to maintain a temperature colder than deep space in order to work. The culprit? "A bit of baguette," says Mike Lamont of the control center of CERN, the European Organization for Nuclear Research, which built and maintains the LHC. Apparently, a passing bird may have dropped the chunk of bread on an electrical substation above the accelerator, causing a power cut. The baguette was removed, power to the cryogenic system was restored and within a few days the magnets returned to their supercool temperatures.

While most scientists would write off the event as a freak accident, two esteemed physicists have formulated a theory that suggests an alternative explanation: perhaps a time-traveling bird was sent from the future to sabotage the experiment. Bech Nielsen of the Niels Bohr Institute in Copenhagen and Masao Ninomiya of the Yukawa Institute for Theoretical Physics in Kyoto, Japan, have published several papers over the past year arguing that the CERN experiment may be the latest in a series of physics research projects whose purposes are so unacceptable to the universe that they are doomed to fail, subverted by the future. 

The LHC, a 17-mile underground ring designed to smash atoms together at high energies, was created in part to find proof of a hypothetical subatomic particle called the Higgs boson. According to current theory, the Higgs is responsible for imparting mass to all things in the universe. But ever since the British physicist Peter Higgs first postulated the existence of the particle in 1964, attempts to capture the particle have failed, and often for unexpected, seemingly inexplicable reasons.

In 1993, the multibillion-dollar United States Superconducting Supercollider, which was designed to search for the Higgs, was abruptly canceled by Congress. In 2000, scientists at a previous CERN accelerator, LEP, said they were on the verge of discovering the particle when, again, funding dried up. And now there's the LHC. Originally scheduled to start operating in 2006, it has been hit with a series of delays and setbacks, including a sudden explosion between two magnets nine days after the accelerator was first turned on, the arrest of one of its contributing physicists on suspicion of terrorist activity and, most recently, the aerial bread bombardment from a bird. (A CERN spokesman said power cuts such as the one caused by the errant baguette are common for a device that requires as much electricity as the nearby city of Geneva, and that physicists are confident they will begin circulating atoms by the end of the year). 

In a series of audacious papers, Nielsen and Ninomiya have suggested that setbacks to the LHC occur because of "reverse chronological causation," which is to say, sabotage from the future. The papers suggest that the Higgs boson may be "abhorrent to nature" and the LHC's creation of the Higgs sometime in the future sends ripples backward through time to scupper its own creation. Each time scientists are on the verge of capturing the Higgs, the theory holds, the future intercedes. The theory as to why the universe rejects the creation of Higgs bosons is based on complex mathematics, but, Nielsen tells TIME, "you could explain it [simply] by saying that God, in inverted commas, or nature, hates the Higgs and tries to avoid them."

Many physicists say that Nielsen and Ninomiya's theory, while intellectually interesting, cannot be accurate because the event that the LHC is trying to recreate already happens in nature. Particle collisions of an energy equivalent to those planned in the LHC occur when high-energy cosmic rays collide with the earth's atmosphere. What's more, some scientists believe that the Tevatron accelerator at Fermi National Accelerator Laboratory (or Fermilab) near Chicago has already created Higgs bosons without incident; the Fermilab scientists are now refining data from their collisions to prove the Higgs' existence. 

Nielsen counters that nature might allow a small number of Higgs to be produced by the Tevatron, but would prevent the production of the large number of particles the LHC is anticipated to produce. He also acknowledges that Higgs particles are probably produced in cosmic collisions, but says it's impossible to know whether nature has stopped a great deal of these collisions from happening. "It's possible that God avoids Higgs [particles] only when there are very many of them, but if there are a few, maybe He let's them go," he says.

Nielsen and Ninomiya's theory represents one side of an intellectual divide between particle physicists today. Contemporary physicists tend to fall into one of two camps: the theorists, who posit ideas about the origins and workings of the universe; and experimentalists, who design telescopes and particle accelerators to test these theories, or provide new data from which novel theories can emerge. Most experimentalists believe that the theorists, due to a lack of new data in recent years, have reached a roadblock — the Standard Model, which is the closest thing the theorists have to an evidence-backed "theory of everything," provides only an incomplete explanation of the universe. Until theorists get further data and evidence to move forward, the experimentalists believe, they end up simply making wild guesses — like those concerning time-traveling saboteurs — about how the universe works. "Nielsen and Ninomiya's theories are clearly crazy theories," says Dmitri Denisov, a physicist and Higgs-hunter at the DZero experiment at Fermilab. "In recent years theorists have been starving for experimental input and as a result, theories of second type are propagating widely. The majority of them have nothing to do with world we live in." 

Nielsen concedes, "We have very little data, so theorists are going their own ways and making a lot of theories that may not be very plausible. We need guidance from experimentalists to make the theories more healthy."

"But," he adds, "in terms of our theory, we are submitting to a form of experiment. We are saying the LHC won't be allowed to produce a large number of Higgs. If it does, it would be very damaging to our theory."

Particle physics has a long history of zany theories that turned out to be true. Niels Bohr, the doyen of modern physicists, often told a story about a horseshoe he kept over his country home in Tisvilde, Denmark. When asked whether he really thought it would bring good luck, he replied, "Of course not, but I'm told it works even if you don't believe in it." In other words: if preposterous theories are mathematically sound and can be confirmed by observation, they are true, even if seemingly impossible to believe. To scientists in the early 20th century, for example, quantum mechanics may have seemed outrageous. "The concept that you could have a wave-particle duality — that an object could take on either wave-like properties or point-like properties, depending on how you observe it — takes a huge leap of imagination," says Roberto Roser, a scientist at Fermilab. "Sometimes outlandish papers turn out to be the laws of physics."

So what would Peter Higgs himself make of the intellectual controversy surrounding his eponymous particle? Speaking on behalf of his friend, Professor Richard Kenway, who holds Higgs' former position at the University of Edinburgh, says that the 78-year-old emeritus professor remains quietly confident that the LHC will discover the Higgs boson when it is eventually running at full strength. For his part, Kenway says the LHC's delays are to be expected given the size and intricacy of the $9 billion experiment. And he says if he ever needs further proof that the Higgs boson is not abhorrent to nature, he need only spend time with his friend and mentor. "If nature truly did not want us to discover the Higgs, a cosmic ray would have zapped the embryo that became Peter, preventing its development into a physicist," he says.

By Eben Harrell Wednesday, Nov. 11, 2009

How To See a Black Hole

A black hole is like a scary monster from children’s literature. It’s vividly imagined but never actually seen in real life.

A simulated image of the disk of gas surrounding the supermassive black hole at the centre of the Milky Way as it might appear with new methods designed to reveal the black hole's dark edge. The light-bending effects of the black hole's strong gravitational field as well as the disk's rapid rotation would produce a crescent shaped image wrapped around the event horizon.

Avery Broderick

This is true even for the largest black holes we know — the ones that reside at the centers of galaxies. The nearest of these lies some 30,000 light-years away, in the core of the Milky Way. If you placed it in our solar system it would probably span the orbit of Mercury. Yet, because of its great distance, it’s a mere speck against the sky, about 36 million times smaller than the full Moon. How could anyone see any detail when looking at something with an apparent size that small?

Amazingly, there is a way. And now it’s promising not only to reveal the giant black hole in our own galaxy, but also a much larger and more active one in the galaxy known as M87 in Virgo.

The nifty trick that puts this ambitious goal within reach is called very long baseline interferometry. VLBI involves two or more radio dishes that are spaced as far apart as possible — for example, in Arizona and Hawaii. The dishes observe the same radio sources in the sky, and when their signals are combined they form an image that’s as sharp as what you would get from a single receiver as big as the separation between the dishes. The idea is to show the way radio emission is spatial distributed across a small region of sky. It’s just what you need to “see” a black hole.

But what does that mean? Aren’t black holes supposed to be, well, black?

Yes and no. If completely isolated in space, a black hole would indeed be well camouflaged. But in the densely populated center of the Milky Way, there is plenty of hot gas swirling around the giant black hole there.

The energized ions in the gas give off radio waves. Seen up close, there should also be a dark sphere at the center of that swirl of gas, where matter funnels in and never comes out. The dark sphere is the infamous event horizon. It’s the point of no return, from which not even light can escape. In this case, “seeing” the black hole means seeing the event horizon silhouetted against the glowing gas.

Shep Doeleman of the Massachusetts Instistute of Technology has been leading the charge to image the Milky Way’s central black hole, and he and his collaborators have made astounding progress. They’ve looked deep into the heart of the radio source known as Sagittarius A*, where the black hole is believed to be lurking. What they’ve got is not exactly an image but a sense that there is some structure on the scale of a supermassive black hole deep in the heart of the radio source.

The complication in mapping out an image of this object is that Sgr A* is changing on a regular basis, presumably as clumps of gaseous matter go a-whirling around the black hole.

This is not going to be a problem when it comes to looking at even bigger black holes, like the giant monster at the center of the galaxy M87 in Virgo. It devours vast quantities of gas and spits out a spectacular jet that extends far into extragalactic space.

Recently, Karl Gebhardt of the University of Texas at Austin and Jens Thomas of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, set about measuring the size of M87 by running existing data through a new model that mimics the galaxy star by star. Unlike earlier efforts, their model also takes into account the unseen halo of dark matter that surround the visible portion of the galaxy. This turned out to have an unexpected affect on the way the model calculates the mass in the stars that illuminate the galaxy’s core. In the final analysis, it allocates far more mass — a whopping 6.4 billion suns — to the galaxy’s monstrous central black hole.

The surprising corollary to this is that M87’s black hole, if viewed from Earth, should be the same apparent size as the black hole in Sgr A* — just as the Sun and the Moon appear roughly the same size, though the Sun is larger and much farther way. That puts M87’s black hole within reach of Doeleman’s radio telescopes. It may even be easier to image than Sgr A* because it’s larger size means it doesn’t change nearly as rapidly.

What’s particularly exciting to theorists like Avery Broderick, of the Canadian Institute for Theoretical Astrophysics in Toronto, is that M87’s black hole is also violently active, with a vast disk of gas around it and a big jet of shooting out in one direction. A radio image of this black hole might not only reveal the event horizon but show us the region where the jet is launched.

“It’s kind of exciting as an alternate object because it is so different from the supermassive black hole in our backyard,” says Avery. “Between them, they span the range of what we expect from these objects.”

Stay tuned. Modern astronomy is increasingly become the science in which the unseen becomes seeable. Before long we’ll be adding black holes to that list.

Seven things that don't make sense about gravity

It's the force we all know about and think we understand. It keeps our feet firmly on the ground and our world circling the sun.

Yet look a little closer, and the certainties start to float away, revealing gravity as the most puzzling and least understood of the four fundamental forces of nature.

Michael Brooks investigates its mysterious ways

What is gravity?

You jump up, and gravity brings you back down to Earth. You reach the brow of a hill and gravity accelerates you down the other side. All neat and tidy then: gravity behaves in the way Newton thought of it, as a force that affects and changes the motion of something else.

That, at least, was how it seemed until Einstein came along. His general theory of relativity tells us that gravity is not quite that simple.

General relativity provides a framework under which the laws of physics look the same for everyone at every moment, regardless of how they are moving. Einstein achieved this by making gravity a property of the universe, rather than of individual bodies.

General relativity describes gravity as geometry. The fabric of the universe - the four dimensions of space and time - is full of lumps and bumps created by the presence of mass and energy. This warping is unavoidable; whenever anything - be it you, me, a piece of space dust or a photon of light - tries to travel through the universe in a straight line, it actually follows a trajectory that is curved by any mass and energy in the vicinity. The result of this curvature is what we think of as gravity. To look at it a slightly different way, gravity is not what one body does directly to another, but what a body's mass does to the surrounding universe.

Nevertheless, treating gravity as if it were a straightforward force, as Newton did, has served us well. It allowed us to send rockets to the moon and chart the orbits of the planets with astonishing accuracy. "The Newtonian description works to high precision," says Bernard Carr of Queen Mary, University of London.

Einstein's description has stood up equally well to scrutiny in situations when high speeds and accelerations are involved. Yet useful as they are, neither the Newtonian model nor relativity is a fundamental explanation for gravity. We still don't know how the fundamental, quantum properties of mass, energy and space-time combine to create the phenomenon.

We do have an idea, though. At the most basic level, the other three fundamental forces of nature - the electromagnetic force, the weak nuclear force and the strong nuclear force - work through the action of particles. The electromagnetic force, for example, is delivered by photons. This picture is known as quantum field theory. In the same way, there ought to be particles that deliver the gravitational force.

There are still two problems with this, though. First, we have yet to find any proof of the existence of these hypothetical particles, which have been dubbed "gravitons". Secondly, when quantum field theory is applied to gravity, it is prone to give nonsensical answers to straightforward questions. "These are fundamental obstructions that need to be overcome," says Bruce Bassett of the University of Cape Town, South Africa.

Why does gravity only pull?

All the other forces in nature have opposites. In the case of the electromagnetic force, for example, it can attract or repel, depending on the charges of the bodies involved. So what makes gravity different?

The answer seems to lie with quantum field theory. The particles that transmit the strong, weak and electromagnetic forces have various types of charge, such as electric or colour charge. "Those charges can be either positive or negative, leading to different possibilities for the sign of the force," says Frank Wilczek of the Massachusetts Institute of Technology. This is not the case with gravitons, the hypothetical particles that quantum field theory says should transmit gravity. "Gravitons respond to energy density, which is always positive," says Wilczek.

Or are we assuming too much here? "We don't know that gravity is strictly an attractive force," cautions Paul Wesson of the University of Waterloo in Ontario, Canada. He points to the "dark energy" that seems to be accelerating the expansion of the universe, and suggests it may indicate that gravity can work both ways. Some physicists speculate that dark energy could be a repulsive gravitational force that only acts over large scales. "There is precedent for such behaviour in a fundamental force," Wesson says. "The strong nuclear force is attractive at some distances and repulsive at others."

Either way, the apparent difference between gravity and the other fundamental forces poses a problem for physicists wanting to create a "theory of everything" that provides a single explanation for them all. At the moment, most theorists expect our best route to such a theory to lie via a hidden symmetry of nature known as supersymmetry, which suggests that every particle has a much heavier twin waiting to be discovered. Wilczek warns, though, that this may not be the final answer. "It's also possible that some essentially new idea will be required," he says.

Why is gravity so weak?

Take a moment to try a jump into the air. Have you ever thought about how remarkable it is that so little effort is required to jump a few inches off the ground. Your puny muscles, weighing just a few kilograms, can overcome the gravitational force of the Earth, all 6 × 10²⁴ kilograms off it. Gravity is a real weakling - 10⁴⁰ times weaker than the electromagnetic force that holds atoms together.

Although the other forces act over different ranges, and between very different kinds of particles, they seem to have strengths that are roughly comparable with each other. Gravity is the misfit. Why should this be so?

So far, our best explanation comes from string theory, the leading candidate for a "theory of everything". String theory requires that the universe has more than the three spatial dimensions that we experience, and possibly as many as 10. According to string theorists' best ideas, gravity is so weak because, unlike the other forces, it leaks in and out of these extra dimensions. We only get to experience a dribble of the true strength of gravity.

The proof of this might come through experiments that probe the gravitational attraction between objects that are very small distances apart. String theory suggests that the unseen dimensions are hidden from view because they are rolled up small, or lie "end-on" to our dimensions, making it hard to detect their presence. These compactified dimensions could alter the gravitational attraction between two bodies if they are very small distances apart. Experiments have got down to about 0.06 millimetres, but have failed to see anything so far.

One of the big hopes for the Large Hadron Collider at CERN near Geneva, Switzerland, is that it will tell us why gravity is so weak. "The LHC's purpose, more or less, is to understand this question," says Lisa Randall of Harvard University.

Though it is not likely to provide a complete answer, the case for gravity residing in extra, hidden dimensions would be strengthened if the LHC finds evidence for particles called Kaluza-Klein states.

These were mooted as far back as the 1930s by theorists attempting to unite electromagnetism and gravity. Kaluza-Klein states arise when familiar particles slip into an extra dimension. As they rattle around there, they create an "echo" that would manifest itself as a heavier particle.

Why is gravity fine-tuned?

The feebleness of gravity is something we should be grateful for. If it were a tiny bit stronger, none of us would be here to scoff at its puny nature.

The moment of the universe's birth created both matter and an expanding space-time in which this matter could exist. While gravity pulled the matter together, the expansion of space drew particles of matter apart - and the further apart they drifted, the weaker their mutual attraction became.

It turns out that the struggle between these two was balanced on a knife-edge. If the expansion of space had overwhelmed the pull of gravity in the newborn universe, stars, galaxies and humans would never have been able to form. If, on the other hand, gravity had been much stronger, stars and galaxies might have formed, but they would have quickly collapsed in on themselves and each other. What's more, the gravitational distortion of space-time would have folded up the universe in a big crunch. Our cosmic history could have been over by now.

Only the middle ground, where the expansion and the gravitational strength balance to within 1 part in 10¹⁵ at 1 second after the big bang, allows life to form. That is down to the size of the gravitational constant G, also known as Big G.

G is the least well-defined of all the constants of nature. It has been pinned down to only 1 part in 10,000, which makes it look pretty rough and ready next to the fundamental number called the Planck constant, which is accurate to 2.5 parts in 100 million. It's gravity's weakness that makes G difficult to measure more accurately - but that's just a laboratory issue. The important question is, where does this value come from? Why does G have the value that allowed life to form in the cosmos?

The simple but unsatisfying answer is that we could not be here to observe it if it were any different. As to the deeper answer - no one knows. "We can make measurements that determine its size, but we have no idea where this value comes from," says John Barrow of the University of Cambridge. "We have never explained any basic constant of nature."

Does life need gravity?

Plants certainly do. Charles Darwin was the first western scientist to show that rooted plants have gravity sensors: plumb lines, effectively, that give them a sense of up or down. Turn a plant pot on its side and you'll find that the roots continue to grow towards the centre of the Earth.

Grown in space, plants show disoriented roots that don't get the best access to nutrients and water. Poor starch production is one of a number of adverse effects of this.

Some seeds grown in microgravity even produce plants in which the genes are expressed differently from normal.

Animals suffer a raft of problems if they are deprived of gravity - though we don't yet know the whole story. "We've had animal life in space for half a century, but we've yet to have a single mammal go through its life cycle," says biologist Richard Wassersug of Dalhousie University in Halifax, Nova Scotia, Canada.

We do know that there can be problems from the start. Experiments on the Russian space station Mir found that fewer quail eggs than normal hatched, and chicks from those that did hatch were unusually likely to suffer abnormalities.

Then there was an experiment on the US space shuttle Discovery, paid for by the KFC fast food corporation, that investigated the development of quail embryos. None of its 16 embryos hatched. In normal gravity, the yolk lies next to the shell, but in microgravity it floats in the middle of the albumen. This led to problems in the transfer of gas between the embryo and the shell, which proved fatal for the embryos. Wasser reckons these difficulties could be solved with suitable engineering, or by taking the embryos into space at a later stage.

Even bigger problems emerge if embryos survive to see the light of day. Chicks hatched in microgravity can't balance and orient themselves well enough to feed. Amphibians have problems with breathing: their instinct is to go "up" for air, but there is no up.

Humans have problems with breathing for a different reason. In space, astronauts' lung capacity is reduced because there is no gravity to pull the diaphragm downwards. To make matters worse, the liver sits higher in microgravity, further reducing lung size. For a short trip this isn't too much of a problem, but what would happen to babies born in space?

"We don't know what happens if you grow from a crawling baby to an adult with smaller lungs," Wassersug says. "There's every reason to believe serious problems will start to set in during youthful growth." It's the simple things that get you: you can't cough your lungs clear, for example. This and other seemingly minor complications "could be seriously dangerous by the time you get to sexual maturity", Wassersug says.

Then there's the issue of bone loss. To grow properly, our bones need to be stressed by out body's weight. Space station crews returning to Earth show that we also suffer severe muscle loss in microgravity - possibly enough to make it impossible for women to give birth naturally in space.

Who knows what else could affect us after long years in space? "It's hard to appreciate how little we've learned about development and growth in weightlessness," Wassersug says.

Can we counter gravity?

Though the notion of building a gravity shield has a long history, no one has yet managed to do it. Perhaps the most famous attempt was by Russian émigré scientist Evgeny Podkletnov.

In 1992, Podkletnov published a paper in which he claimed to have detected a 2 per cent weight reduction around a spinning disc made out of a ceramic superconductor.

Martin Tajmar, a researcher at the company Austrian Research Centers, published a similar claim in 2003 and was able to pursue the research further with funding from the European Space Agency. Three years later Tajmar and ESA announced they had measured an effect in a spinning superconductor that might, with further development, be harnessed to affect gravity. Others have tried and failed to replicate this effect.

Why does anyone think it might even be possible? Because relativity does not rule out the possibility that the bent space-time that gives rise to gravity's pull can be "unbent". "By appropriate arrangements, it should be possible to diminish - or enhance - the influence of gravity," says physicist Bahram Mashhoon at the University of Missouri.

Tajmar invokes an effect called "gravito-magnetism" as a way of doing this. According to general relativity, the mass of a rotating body will drag space-time around with it, putting a twist into it. Just as a spinning charge creates a magnetic field, a spinning mass creates a gravito-magnetic field.

This should have real-world effects - the Earth's spin, for instance, should cause satellite orbits to precess - but you won't be surprised to hear there are practical issues with using the idea to reduce gravity. "The relativistic effects are extremely small in practice," Mashhoon points out.

Though it's not even clear that a spinning superconductor has any gravito-magnetic influence, people should not be ridiculed for continuing to research in this area, Mashhoon says. It might just turn out to be the only way we can achieve interstellar travel. Some researchers have suggested that above a certain critical speed, relativity can give repulsive gravitational effects that could be used for propulsion as well as gravity shielding. "With present technology, it would take us about a million years or so to go to the nearest neighbouring star," Mashhoon says. "It is hard to blame people for looking into these things."

Will we ever have a quantum theory of gravity?

Quantum mechanics and relativity, our two most successful theories of how the world works, both seem strangely at odds with the everyday world as we experience it - and with each other.

Quantum theory, which describes how things behave at the subatomic level, is certainly weird. Quantum objects can simultaneously be in two locations, or move in different directions.

Relativity is, if anything, worse. We can use it to describe gently curving space-time, but the equations turn to nonsense in the extreme conditions found at the heart of a black hole or the beginning of the universe.

From a physicist's point of view, the big problem is that no one has figured out how quantum theory and relativity fit together to make a quantum theory. There has to be a better theory out there, one that describes how and why everything works, from subatomic to cosmological scales, but it is proving extraordinarily elusive.

Einstein was among the first scientists to try to marry gravity with other theories of physics, yet we may be no closer now than he was when he began his search. The most popular quantum gravity theories today seem to have fundamental problems that no one knows how to solve.

Does that mean we'll never get there? We shouldn't despair, says Lee Smolin at the Perimeter Institute for Theoretical Physics in Waterloo, Canada. "I am a big believer in our capacity to understand the universe we find ourselves in," he says.

According to Roger Penrose of the University of Oxford, the final quantum gravity theory won't look like anything that's around at the moment. He reckons today's theories are not powerful enough to even be considered as candidates, as they ignore important issues such as solving the mysteries of the quantum world's strange behaviour. "There ought to be such a theory, but I would expect it to represent a major revolution in our picture of the physical world," he says. "It will require a major breakthrough, and a fundamental departure from current thinking."

Will we get there? Penrose is optimistic. "We might destroy ourselves in a nuclear war or by overheating of the Earth," he says. "But barring that sort of thing, I don't see why not."

Everything you always wanted to know about female ejaculation (but were afraid to ask)

by Sharon Moalem

Sharon Moalem is an evolutionary biologist and neurogeneticist at the Mount Sinai School of Medicine in New York City. His book, How Sex Works, was published this month in the US by HarperCollins

WHEN the British Board of Film Classification ordered 6 minutes and 12 seconds of material cut from British Cum Queens in 2002, they found themselves under attack from an unlikely quarter: a group of feminists.

The offending segment showed some of the female participants apparently ejaculating fluid from their genitals on orgasm. The film board stated that female ejaculation did not exist, so the actresses must have been urinating. And urinating on another actor on film is banned under the UK's Obscene Publications Act.

The group Feminists Against Censorship marshalled all the scientific evidence they could find to prove that some women do in fact ejaculate. The film board eventually backed down from its complete denial of the phenomenon, stating that female ejaculation was a "controversial and much debated area".

It was only a partial climbdown, however, as the film board insisted that the scenes in question were "nothing other than straightforward urination masquerading as ejaculation". In their defence, most pornography scenes that depict women ejaculating are indeed staged. Either the fluid is put into the vagina beforehand off-camera, or the actresses are simply urinating.

The dispute raises an intriguing question. In the 21st century, when human biology has been investigated right down to the genetic level, how can the existence of female ejaculation still be open to debate?

Medical textbooks are silent on this aspect of female physiology and most physicians never learn anything of it, unless of course they experience it themselves or witness it in their partners.

In the past few years, however, there has been an upsurge of research into the female sexual response. It seems that, even today, the human body may be harbouring a few surprises.

Although still controversial, many scientists now accept that some women can ejaculate some kind of fluid during sexual arousal or orgasm. Just how common it is, what the fluid is, and whether it serves any kind of function are some of the most hotly debated questions of sex research today, and I am playing a small part in helping to investigate them.

Many historical texts, such as the Kama Sutra, spoke about female "semen", as did writers, including the Greek physician Hippocrates. Sometimes the writers may have been referring to everyday vaginal secretions, which increase during sexual arousal. However, there are several references to something more akin to ejaculation. In the 17th century, the Dutch physician and anatomist Regnier De Graaf spoke of "liquid as usually comes from the pudenda in one gush".

In the last century, Ernst Gräfenberg, the German doctor who gave his name to the controversial G spot, drew attention to female ejaculation in a 1950 paper published in The International Journal of Sexology. "This convulsory expulsion of fluids occurs always at the acme of orgasm and simultaneously with it," he wrote. "Occasionally the production of fluids is so profuse that a large towel has to be spread under the woman to prevent the bed sheets getting soiled."

Most people did not take the paper seriously and thought Gräfenberg was probably describing a type of incontinence. It is certainly true that a few women experience loss of bladder control during sex, sometimes at the moment of penetration or at orgasm. But some who end up being investigated and even surgically treated for such "coital incontinence" may in fact be experiencing ejaculation. (And probably some who think they ejaculate may in fact be leaking urine.)

Ground-breaker

It is unknown how common genuine female ejaculation might be, or even whether it occurs solely on orgasm or merely during heightened sexual arousal. Just as with men's semen, women who believe that they are ejaculating report great variation in the nature and volume of the fluid produced. It can range from clear to milky-white in colour, and the amount of fluid can range from a few drops to more than a quarter of a cup.

The real ground-breaker came in 1981, when renowned US sexologists Beverly Whipple and John Perry published a case report of a woman apparently happy to ejaculate under laboratory conditions. Watched by a team of researchers, the woman was vaginally stimulated by her husband until she reached orgasm, climaxed, and then ejaculated, releasing noticeable amounts of fluid.

According to Whipple, when Philadelphia gynaecologist Martin Weisberg saw their report he said: "Bull... I spend half my waking hours examining, cutting apart, putting together, removing or rearranging female reproductive organs... Women don't ejaculate."

In response, Whipple offered to set Weisberg up with a personal demonstration. The following is Weisberg's description of what he witnessed, which was later included in Whipple and her co-author's bestselling book, The G Spot and Other Recent Discoveries About Human Sexuality: "The subject seemed to perform a Valsalva manoeuvre [bearing down as if starting to defecate] and seconds later several cc's of milky fluid shot out of the urethra."

Impressive as that demonstration sounds, it is interesting to note that the fluid appeared to emerge from the urethra, the tube that drains urine from the bladder to an exit near the entrance of the vagina (see diagram). Could it have been urine after all?

Not according to chemical analysis of the fluid, carried out by Whipple and a few others since then. They found the ejaculate contained very low levels of urea and creatinine, the two main chemical hallmarks of urine.

One marker it did contain, however, was prostate-specific antigen, or PSA. That's the same chemical produced by the prostate gland in men.

The male prostate is usually around the size of a walnut, weighing about 23 grams. It surrounds the urethra like a doughnut and is encased by a fibromuscular sheet, which contracts during ejaculation to help expel prostatic fluid into the urethra, where it mixes with the other components of semen.

Less widely known is that women have prostate tissue too. And this, it seems, is the best candidate for the source of female ejaculate. Also known as the Skene's glands or the paraurethral glands, in 2001 the Federative Committee on Anatomical Terminology officially renamed these structures the "female prostate".

The female prostate seems to vary in size and shape much more than the male version, with some women lacking any appreciable amount of prostate tissue, according to autopsy studies by Slovakian pathologist Milan Zaviacic. This may explain women's differing experiences.

G spot

If the tissue is there at all it lies next to, or sometimes surrounds, the urethra, which is adjacent to the vagina's anterior wall. In other words, if the woman is lying on her back, the prostate is directly above the uppermost wall of her vagina.

This is roughly the same area as the G spot, the part of the vagina that is particularly sensitive to stimulation, although even the G spot's existence is controversial. Assuming there is such a thing, however, it is beginning to look to many sexologists as if the G spot is just the name for the best place to stimulate a woman's prostate. Variation in the amount of prostate tissue could explain why not all women find stimulation of this area arousing - in other words, whether or not they have a G spot

When anatomy textbooks show the female prostate - and not all do - the gland tissue is sometimes shown with ducts draining fluid to two pinhole-sized openings next to the urethra, just above the vagina. Others, however, suggest there may be as many as 20 ducts, and that they drain into the urethra, near its external opening (as shown above).

One of the more interesting reports on female ejaculation was published in 2007 by a team led by Florian Wimpissinger, an Austrian urologist at Rudolfstiftung Hospital in Vienna (The Journal of Sexual Medicine, vol 4, p 1388).

Two women in their 40s came to the attention of the researchers after they attended a sexual medicine clinic because of "significant fluid expulsion during orgasm". The women agreed to produce samples of the fluid by masturbation in the lab. When analysed, this fluid was found to be chemically distinct from urine, with high PSA and other features more akin to male ejaculate.

Ultrasound scans showed that both women had large prostate glands. One woman's scan showed "a hyperintense structure surrounding the entire length of the urethra", which "closely resembles that of the male prostate", according to the authors. By inserting a fine flexible tube with a camera on the end into the urethra, the researchers could see a duct exiting just inside the entrance to the urethra.

The team has another paper due to be published in The Journal of Sexual Medicine next month, describing how they used MRI scans to investigate the prostate of seven women who attended a urology clinic. In this study, however, the team did not find a correlation between prostate size and the ability to ejaculate. Larger studies of this kind are obviously needed.

Partly thanks to the growing body of research in this area, there seems to be increasing awareness of female ejaculation among the general public. Some sex educators provide workshops claiming to teach women how to ejaculate (as well as how to discover their G spots and have more orgasms).

One question that is rarely addressed, however, is whether female ejaculation has a biological function. Not every aspect of our physiology has to have such a role. For example, men are thought to have nipples only because women need them, and male and female embryos develop from the same body plan. Some have even cited this as the reason why women orgasm. Perhaps female ejaculation has a similar explanation.

On the other hand, it is tempting to speculate about what purpose female ejaculation could fulfil. Whipple and Perry have suggested that female ejaculation evolved to combat infections of the urethra and bladder. Many secretions and fluids produced by the human body, such as saliva, tears, and indeed male ejaculate, are awash with compounds that inhibit the growth of bacteria.

Urinary tract infections are relatively common in women, and sometimes arise from bacteria spread to the urethra during sex. A gush of antimicrobial fluid at the entrance to the urethra around the time of sex might help fight off such bacteria.

Along with my colleagues I am investigating whether female ejaculate contains some of the antimicrobial chemicals present in semen, such as zinc. If so, then this fascinating and long-neglected phenomenon might turn out to be more than just a sexual curiosity.

Discover Interview: Lisa Randall

One of physics' brightest stars ventures into 10 dimensions, visits other universes, explains gravity, and keeps her sense of humor.

by Corey S. Powell

Starting in earnest a couple of decades ago, a group of physicists began seeking deeper truth in string theory, which holds that the fundamental particles of nature consist of minuscule vibrating strands of energy. Problem is, the theory works well only if the strings vibrate in more than three dimensions. Randall, a theoretical physicist at Harvard University, is a leading light of a second generation of researchers who are taking that idea to an even grander level, envisioning not just tiny strands but huge territories of higher dimension, called branes. She thinks this approach could revolutionize our understanding of gravity and uncork the deepest workings of the universe.

Yet Randall is resolutely down to earth. She chafes at the thought that her ideas should be restricted to the confines of academia, she both respects and swats aside her importance as a woman in a male-dominated field—and then there is that laugh, hearty and throaty, that erupts repeatedly during our conversation. She finds this world rich and comforting and funny. She just wants to give it a little more dimension.


Where did your interest in physics begin?

When I was in school I liked math because all the problems had answers. Everything else seemed very subjective. The teachers in English class would say, "What is the reason that this is an important book?" They'd look for the three good reasons, whereas you might think of some other one. I didn't like the arbitrariness of that. Later I decided that just doing math would drive me crazy. I'd be up all night working on a problem, and I thought, "I can't live the rest of my life like this." [Laughs] I wanted something more connected to the world.

Speaking of staying connected to the world—in your work you imagine extra dimensions, but you still have to live on the same planet as the rest of us. Do you carry around the image of other dimensions in your mind?

It's momentary. In my book I describe a time walking over the Charles River and thinking, "You know, I really do believe there are extra dimensions out there." Sometimes I have a sense of what I'm seeing being a small fraction of what's there. Not always there, but probably more often than I realize. Something will come up, and I'll realize I'm thinking about the world a little differently than my friends.


So you intuitively believe higher dimensions really exist?

I don't see why they shouldn't. In the history of physics, every time we've looked beyond the scales and energies we were familiar with, we've found things that we wouldn't have thought were there. You look inside the atom and eventually you discover quarks. Who would have thought that? It's hubris to think that the way we see things is everything there is.


If there are more than three dimensions out there, how does that change our picture of the universe?

What I'm studying is branes, membranelike objects in higher-dimensional space. Particles could be stuck to a three-dimensional brane, sort of like things could be stuck to the two-dimensional surface of a shower curtain in our three-dimensional space. Maybe electromagnetism spreads out only over three dimensions because it's trapped on a three-dimensional brane. It could be that everything we know is stuck on a brane, except for gravity.


Yet we very clearly see only three dimensions when we look around. Where could the other dimensions be hiding?

The old answer was that the extra dimensions were tiny: If something is sufficiently small, you just don't experience it. That's the way things stood until the 1990s, when Raman Sundrum and I realized you could have an infinite extra dimension if space-time is warped. Then with Andreas Karch, I found something even more dramatic—that we could live in a pocket of three dimensions in a higher-dimensional universe. It could be that where we are it looks as if there's only three dimensions in space, but elsewhere it looks like there's four or even more dimensions in space.


And there could be a whole other universe set up that way?

Possibly. It would be a different universe because, for example, bound orbits [like Earth's path around the sun] work only in three dimensions of space. And the other universe could have different laws of physics. For example, they could have a completely different force that we are immune to. We don't experience that force, and they don't experience, say, electromagnetism. So it could be that we're made of quarks and electrons, while they're made up of totally different stuff. It could be a completely different chemistry, different forces—except for gravity, which we believe would be shared.


What is so special about gravity?

In string theory there are two types of strings, open ones with ends and closed ones that loop around. Open strings are anchored to the surface of a brane, so the particles associated with them are stuck on the brane. If you have an open string associated with the electron, for example, it's on a brane. Gravity is associated with a closed string. It has no end, and there is no mechanism for confining it to a brane. Gravity can spread out anywhere, so it really is different. It can leak out a little into extra dimensions. That can explain why gravity is so weak compared with the other forces. After all, a little magnet can lift a paper clip against the pull of the entire Earth.


Some of these ideas sound, frankly, a bit crazy to the average person. Where do they come from?

One reason people think about extra dimensions is string theory, the hypothesis that fundamental particles are actually oscillations of tiny strands of energy. String theory gives you a way to combine two very different models of the world, quantum mechanics and general relativity. Basically, quantum mechanics applies on atomic scales, and general relativity applies on big scales. We believe there should be a single theory that works over all regimes. String theory does that, but only in a universe that has more than three dimensions of space. More generally, there's stuff we don't understand if there are only three dimensions of space, and some of those questions seem to have answers if there are extra dimensions. Also, no fundamental physical theory singles out three dimensions of space. The theory of gravity allows any number. So it's logical to think what the world would look like if extra dimensions are there.


How will we know if your ideas are right?

Experimentalists will look for what are called Kaluza-Klein particles, which are associated with the hidden dimensions. The Large Hadron Collider [a particle accelerator on the French-Swiss border that will switch on in 2007] could have enough energy to produce these particles. In our theory, Kaluza-Klein particles will decay in the detector—you find the decayed product and you can reconstruct what was there. That would provide very strong evidence of extra dimensions. Maybe within five years we'll know the answers.



These are costly experiments. Do you worry about the public's willingness to support such purely theoretical research?

I'm really concerned about it. If we don't do it now, we'll probably never do it. We've built up the technology; we're at a point where if we don't continue, we'll lose that expertise, and we'll have to start all over again. True, it's expensive, but at the end of the day I believe it will be worth it. It makes a difference in terms of who we are, what we think, how we view the world. These are the kinds of things that get people excited about science, so you have a more educated public.


One of the amazing things about your work is that so much of it comes straight from your imagination, not from rooting around in the laboratory. It seems very much like chalk-and-blackboard research.

Right, the blackboard. Those are the things that seem to strike people, that we have blackboards with equations all over them and that we are talking to each other a lot; we're not just going into our offices and ignoring the rest of the word. But we do just go and think sometimes. Once you're really focused, if you get jogged out of it, you have to go back and really reestablish that. It's like Fred Flintstone and his bowling ball: You don't want to interrupt someone when they're in that state. Then again, sometimes we're just talking and writing together on a piece of paper, and sometimes we're at that blackboard putting ideas back and forth. Our work is all those things. It's reading what other people have done, trying to puzzle through something, getting stuck, getting unstuck, trying to find different ways around a problem.


You don't exactly fit the image of the graying, tweedy professor. Does being a young woman in a male-dominated field carry special responsibilities?

If only I was still young! [Laughs] I thought maybe I'd make it all the way through an interview without having to talk about this. But, yeah, I think it does. I'm probably more careful, and probably I spend more time on this particular issue. Also, in writing my book, I felt it had better be good, because there aren't that many women in the field, and I thought it would be subject to extra scrutiny. So there is extra responsibility; the flip side is that potentially there's extra reward if it draws a more diverse group into physics.


Outside your own area of research, where do you see the most vibrant things happening in science today?

Neuroscience is exciting. Understanding how thoughts work, how connections are made, how the memory works, how we process information, how information is stored—it's all fascinating. Experimentally, though, we're still rather limited in what we can do. I don't even know what consciousness is. I'd like someone to define consciousness.


Many people would say physics has a long way to go too. Does it bother you that the things you're excited about now may seem quaint as soon as someone comes up with a better theory?

True, we haven't found all the answers, but we've found some and we're finding more. The fact that we don't know everything doesn't mean we know nothing. People have asked me, "Why bother, if you don't get final answers?" I said, "If someone gave me a dessert, and I knew it wasn't the best dessert ever, I would still be really happy to eat it and wait for the next one."


Will physics ever be able to tackle the biggest questions—for instance, why does the universe even bother to exist?

Science is not religion. We're not going to be able to answer the "why" questions. But when you put together all of what we know about the universe, it fits together amazingly well. The fact that inflationary theory [the current model of the Big Bang] can be tested by looking at the cosmic microwave background is remarkable to me. That's not to say we can't go further. I'd like to ask: Do we live in a pocket of three-dimensional space and time? We're asking how this universe began, but maybe we should be asking how a larger, 10-dimensional universe began and how we got here from there.


This sounds like your formula for keeping science and religion from fighting with each other.

A lot of scientists take the Stephen Jay Gould approach: Religion asks questions about morals, whereas science just asks questions about the natural world. But when people try to use religion to address the natural world, science pushes back on it, and religion has to accommodate the results. Beliefs can be permanent, but beliefs can also be flexible. Personally, if I find out my belief is wrong, I change my mind. I think that's a good way to live.


So does your science leave space for untestable faith? Do you believe in God?

There's room there, and it could go either way. Faith just doesn't have anything to do with what I'm doing as a scientist. It's nice if you can believe in God, because then you see more of a purpose in things. Even if you don't, though, it doesn't mean that there's no purpose. It doesn't mean that there's no goodness. I think that there's a virtue in being good in and of itself. I think that one can work with the world we have. So I probably don't believe in God. I think it's a problem that people are considered immoral if they're not religious. That's just not true. This might earn me some enemies, but in some ways they may be even more moral. If you do something for a religious reason, you do it because you'll be rewarded in an afterlife or in this world. That's not quite as good as something you do for purely generous reasons.

The Biocentric Universe Theory: Life Creates Time, Space, and the Cosmos Itself

Stem-cell guru Robert Lanza presents a radical new view of the universe and everything in it.

by Robert Lanza and Bob Berman

The farther we peer into space, the more we realize that the nature of the universe cannot be understood fully by inspecting spiral galaxies or watching distant supernovas. It lies deeper. It involves our very selves.

This insight snapped into focus one day while one of us (Lanza) was walking through the woods. Looking up, he saw a huge golden orb web spider tethered to the overhead boughs. There the creature sat on a single thread, reaching out across its web to detect the vibrations of a trapped insect struggling to escape. The spider surveyed its universe, but everything beyond that gossamer pinwheel was incomprehensible. The human observer seemed as far-off to the spider as telescopic objects seem to us. Yet there was something kindred: We humans, too, lie at the heart of a great web of space and time whose threads are connected according to laws that dwell in our minds.

Is the web possible without the spider? Are space and time physical objects that would continue to exist even if living creatures were removed from the scene?

Figuring out the nature of the real world has obsessed scientists and philosophers for millennia. Three hundred years ago, the Irish empiricist George Berkeley contributed a particularly prescient observation: The only thing we can perceive are our perceptions. In other words, consciousness is the matrix upon which the cosmos is apprehended. Color, sound, temperature, and the like exist only as perceptions in our head, not as absolute essences. In the broadest sense, we cannot be sure of an outside universe at all.

For centuries, scientists regarded Berkeley’s argument as a philosophical sideshow and continued to build physical models based on the assumption of a separate universe “out there” into which we have each individually arrived. These models presume the existence of one essential reality that prevails with us or without us. Yet since the 1920s, quantum physics experiments have routinely shown the opposite: Results do depend on whether anyone is observing. This is perhaps most vividly illustrated by the famous two-slit experiment. When someone watches a subatomic particle or a bit of light pass through the slits, the particle behaves like a bullet, passing through one hole or the other. But if no one observes the particle, it exhibits the behavior of a wave that can inhabit all possibilities—including somehow passing through both holes at the same time.

Some of the greatest physicists have described these results as so confounding they are impossible to comprehend fully, beyond the reach of metaphor, visualization, and language itself. But there is another interpretation that makes them sensible. Instead of assuming a reality that predates life and even creates it, we propose a biocentric picture of reality. From this point of view, life—particularly consciousness—creates the universe, and the universe could not exist without us.

MESSING WITH THE LIGHT
Quantum mechanics is the physicist’s most accurate model for describing the world of the atom. But it also makes some of the most persuasive arguments that conscious perception is integral to the workings of the universe. Quantum theory tells us that an unobserved small object (for instance, an electron or a photon—a particle of light) exists only in a blurry, unpredictable state, with no well-defined location or motion until the moment it is observed. This is Werner Heisenberg’s famous uncertainty principle. Physicists describe the phantom, not-yet-manifest condition as a wave function, a mathematical expression used to find the probability that a particle will appear in any given place. When a property of an electron suddenly switches from possibility to reality, some physicists say its wave function has collapsed.

What accomplishes this collapse? Messing with it. Hitting it with a bit of light in order to take its picture. Just looking at it does the job. Experiments suggest that mere knowledge in the experimenter’s mind is sufficient to collapse a wave function and convert possibility to reality. When particles are created as a pair—for instance, two electrons in a single atom that move or spin together—physicists call them entangled. Due to their intimate connection, entangled particles share a wave function. When we measure one particle and thus collapse its wave function, the other particle’s wave function instantaneously collapses too. If one photon is observed to have a vertical polarization (its waves all moving in one plane), the act of observation causes the other to instantly go from being an indefinite probability wave to an actual photon with the opposite, horizontal polarity—even if the two photons have since moved far from each other.

In 1997 University of Geneva physicist Nicolas Gisin sent two entangled photons zooming along optical fibers until they were seven miles apart. One photon then hit a two-way mirror where it had a choice: either bounce off or go through. Detectors recorded what it randomly did. But whatever action it took, its entangled twin always performed the complementary action. The communication between the two happened at least 10,000 times faster than the speed of light. It seems that quantum news travels instantaneously, limited by no external constraints—not even the speed of light. Since then, other researchers have duplicated and refined Gisin’s work. Today no one questions the immediate nature of this connectedness between bits of light or matter, or even entire clusters of atoms.

Before these experiments most physicists believed in an objective, independent universe. They still clung to the assumption that physical states exist in some absolute sense before they are measured.

All of this is now gone for keeps.

WRESTLING WITH GOLDILOCKS
The strangeness of quantum reality is far from the only argument against the old model of reality. There is also the matter of the fine-tuning of the cosmos. Many fundamental traits, forces, and physical constants—like the charge of the electron or the strength of gravity—make it appear as if everything about the physical state of the universe were tailor-made for life. Some researchers call this revelation the Goldilocks principle, because the cosmos is not “too this” or “too that” but rather “just right” for life.

One is simply to argue for incredible coincidence. Another is to say, “God did it,” which explains nothing even if it is true.

The third explanation invokes a concept called the anthropic principle,? first articulated by Cambridge astrophysicist Brandon Carter in 1973. This principle holds that we must find the right conditions for life in our universe, because if such life did not exist, we would not be here to find those conditions. Some cosmologists have tried to wed the anthropic principle with the recent theories that suggest our universe is just one of a vast multitude of universes, each with its own physical laws. Through sheer numbers, then, it would not be surprising that one of these universes would have the right qualities for life. But so far there is no direct evidence whatsoever for other universes.

The final option is biocentrism, which holds that the universe is created by life and not the other way around. This is an explanation for and extension of the participatory anthropic principle described by the physicist John Wheeler, a disciple of Einstein’s who coined the terms wormhole and black hole.

SEEKING SPACE AND TIME
Even the most fundamental elements of physical reality, space and time, strongly support a biocentric basis for the cosmos.

According to biocentrism, time does not exist independently of the life that notices it. The reality of time has long been questioned by an odd alliance of philosophers and physicists. The former argue that the past exists only as ideas in the mind, which themselves are neuroelectrical events occurring strictly in the present moment. Physicists, for their part, note that all of their working models, from Isaac Newton’s laws through quantum mechanics, do not actually describe the nature of time. The real point is that no actual entity of time is needed, nor does it play a role in any of their equations. When they speak of time, they inevitably describe it in terms of change. But change is not the same thing as time.

To measure anything’s position precisely, at any given instant, is to lock in on one static frame of its motion, as in the frame of a film. Conversely, as soon as you observe a movement, you cannot isolate a frame, because motion is the summation of many frames. Sharpness in one parameter induces blurriness in the other. Imagine that you are watching a film of an archery tournament. An archer shoots and the arrow flies. The camera follows the arrow’s trajectory from the archer’s bow toward the target. Suddenly the projector stops on a single frame of a stilled arrow. You stare at the image of an arrow in midflight. The pause in the film enables you to know the position of the arrow with great accuracy, but you have lost all information about its momentum. In that frame it is going nowhere; its path and velocity are no longer known. Such fuzziness brings us back to Heisenberg’s uncertainty principle, which describes how measuring the location of a subatomic particle inherently blurs its momentum and vice versa.

All of this makes perfect sense from a biocentric perspective. Everything we perceive is actively and repeatedly being reconstructed inside our heads in an organized whirl of information. Time in this sense can be defined as the summation of spatial states occurring inside the mind. So what is real? If the next mental image is different from the last, then it is different, period. We can award that change with the word time, but that does not mean there is an actual invisible matrix in which changes occur. That is just our own way of making sense of things. We watch our loved ones age and die and assume that an external entity called time is responsible for the crime.

There is a peculiar intangibility to space, as well. We cannot pick it up and bring it to the laboratory. Like time, space is neither physical nor fundamentally real in our view. Rather, it is a mode of interpretation and understanding. It is part of an animal’s mental software that molds sensations into multidimensional objects.

Most of us still think like Newton, regarding space as sort of a vast container that has no walls. But our notion of space is false. Shall we count the ways? 1. Distances between objects mutate depending on conditions like gravity and velocity, as described by Einstein’s relativity, so that there is no absolute distance between anything and anything else. 2. Empty space, as described by quantum mechanics, is in fact not empty but full of potential particles and fields. 3. Quantum theory even casts doubt on the notion that distant objects are truly separated, since entangled particles can act in unison even if separated by the width of a galaxy.

UNLOCKING THE CAGE
In daily life, space and time are harmless illusions. A problem arises only because, by treating these as fundamental and independent things, science picks a completely wrong starting point for investigations into the nature of reality. Most researchers still believe they can build from one side of nature, the physical, without the other side, the living. By inclination and training these scientists are obsessed with mathematical descriptions of the world. If only, after leaving work, they would look out with equal seriousness over a pond and watch the schools of minnows rise to the surface. The fish, the ducks, and the cormorants, paddling out beyond the pads and the cattails, are all part of the greater answer.

Recent quantum studies help illustrate what a new biocentric science would look like. Just months? ago, Nicolas Gisin announced a new twist on his entanglement experiment; in this case, he thinks the results could be visible to the naked eye. At the University of Vienna, Anton Zeilinger’s work with huge molecules called buckyballs pushes quantum reality closer to the macroscopic world. In an exciting extension of this work—proposed by Roger Penrose, the renowned Oxford physicist—not just light but a small mirror that reflects it becomes part of an entangled quantum system, one that is billions of times larger than a buckyball. If the proposed experiment ends up confirming Penrose’s idea, it would also confirm that quantum effects apply to human-scale objects.

Biocentrism should unlock the cages in which Western science has unwittingly confined itself. Allowing the observer into the equation should open new approaches to understanding cognition, from unraveling the nature of consciousness to developing thinking machines that experience the world the same way we do. Biocentrism should also provide stronger bases for solving problems associated with quantum physics and the Big Bang. Accepting space and time as forms of animal sense perception (that is, as biological), rather than as external physical objects, offers a new way of understanding everything from the microworld (for instance, the reason for strange results in the two-slit experiment) to the forces, constants, and laws that shape the universe. At a minimum, it should help halt such dead-end efforts as string theory.

Above all, biocentrism offers a more promising way to bring together all of physics, as scientists have been trying to do since Einstein’s unsuccessful unified field theories of eight decades ago. Until we recognize the essential role of biology, our attempts to truly unify the universe will remain a train to nowhere.

Adapted from Biocentrism: How Life and Consciousness Are the Keys to Understanding the True Nature of the Universe, by Robert Lanza with Bob Berman, published by BenBella Books in May 2009.