The Atlas project at Cern: its first results have failed to confirm the theory of supersymmetry
The Large Hadron Collider (LHC) at Cern, the European centre for particle physics, has been presented as an experiment that can’t fail—as long as no more holes get punched in the tunnel, that is. Whether or not its high-energy collisions generate the particles that physicists are predicting, we’ll learn something new and exciting about the basic building blocks of the universe and the forces that act between them.
This tidy conceit can’t disguise the fact that scientists aren’t wholly relaxed about the outcome. They have become attached to their pet theories and will be distressed if these don’t stand up—not least because it’ll be hard to find any better ideas. That’s true of the Higgs boson, the particle predicted to confer mass on other fundamental particles. It is equally true of supersymmetry.
This theory, conceived in the early 1970s, promises a solution to several key problems in physics. The four fundamental forces of nature—gravity, electromagnetic force, and the strong and weak forces that operate in atomic nuclei—are thought to be manifestations of a single force that existed in the first instants of the big bang. The family ties between electromagnetic and weak forces have already been found; supersymmetry would unite these two with the strong force. What’s more, it could explain the nature of the mysterious “dark matter” which is thought to exist. And it could relieve some complications with the theory of the Higgs particle. Best of all to some, it is mathematically beautiful.
Supersymmetry implies that every known particle has a heavier supersymmetric partner, or “sparticle”: each quark has a squark and so on. Verifying supersymmetry means finding these particles. Previous accelerators, such as the Tevatron at Fermilab in Illinois, have failed to do so, but have set limits on how massive they can be.
Now, two of the experimental projects at the LHC, called the compact muon solenoid (CMS) and Atlas, have released their first results—which show no sign of sparticles. That is no reason to abandon the theory, but it may mean that, if sparticles exist, they may be so heavy that supersymmetry runs into as many problems as it solves. Since there are many versions of the theory, an exhaustive search will take time. But as some theorists have spent much of their lives on supersymmetry, its demise would cause much gnashing and wailing.
When worlds collide
Most of the public discussion of extrasolar planets—those around other stars—has, since the discovery of the first of them in 1995, focused on whether there are other Earth-like, habitable worlds. But the less solipsistic and perhaps more tractable question is whether our solar system is typical in the cosmos. Our view of planetary diversity is being broadened by Nasa’s Kepler space observatory, launched in 2009 to scan the stars for extrasolar planets. Among the 170 multi-planet systems seen in the first four and a half months of its operation is a truly mind-boggling one called KOI-730, in which two planets run along a single orbit, one a sixth of a full revolution in front of the other, like two racing cars on the same track.
This possibility had been recognised in theory; the 60-degree angle of separation is the only arrangement in which two such planets can remain stable without one spinning off to its own orbit. Even then, the lagging planet may catch up, with apocalyptic results. Far from being unlikely, it has been suggested this happened to the Earth: that in the early solar system it had a smaller, co-orbiting partner with which it collided, some of the debris forming the Moon. Too much scanning?
Cancer risks from marginal sources is such a fraught issue that you’d expect any scientist to think carefully before suggesting new ones. Yet biophysicist David Brenner is no crank fretting about radio masts, but director of Columbia University’s Centre for Radiological Research. He fears that too many children are being given large doses of X-rays from unnecessary computed tomography (CT) scans for conditions that could be assessed with other techniques.
No one disputes that the dangers of individual scans are minuscule. But with use of them skyrocketing, says Brenner, tiny numbers add up. As Science magazine reports, this is a potentially incendiary claim. One Yale radiologist points out that “no one has conclusively shown that medical radiation has caused cancer,” and the matter can barely be raised without panicking patients. But the debate at least highlights the laxity of regulation for CT scanning. The X-ray dosage per scan varies widely, and some scans do seem to be needless. It’s a reminder that new technologies need careful chaperoning when they meet clinical practice.
The Large Hadron Collider (LHC) at Cern, the European centre for particle physics, has been presented as an experiment that can’t fail—as long as no more holes get punched in the tunnel, that is. Whether or not its high-energy collisions generate the particles that physicists are predicting, we’ll learn something new and exciting about the basic building blocks of the universe and the forces that act between them.
This tidy conceit can’t disguise the fact that scientists aren’t wholly relaxed about the outcome. They have become attached to their pet theories and will be distressed if these don’t stand up—not least because it’ll be hard to find any better ideas. That’s true of the Higgs boson, the particle predicted to confer mass on other fundamental particles. It is equally true of supersymmetry.
This theory, conceived in the early 1970s, promises a solution to several key problems in physics. The four fundamental forces of nature—gravity, electromagnetic force, and the strong and weak forces that operate in atomic nuclei—are thought to be manifestations of a single force that existed in the first instants of the big bang. The family ties between electromagnetic and weak forces have already been found; supersymmetry would unite these two with the strong force. What’s more, it could explain the nature of the mysterious “dark matter” which is thought to exist. And it could relieve some complications with the theory of the Higgs particle. Best of all to some, it is mathematically beautiful.
Supersymmetry implies that every known particle has a heavier supersymmetric partner, or “sparticle”: each quark has a squark and so on. Verifying supersymmetry means finding these particles. Previous accelerators, such as the Tevatron at Fermilab in Illinois, have failed to do so, but have set limits on how massive they can be.
Now, two of the experimental projects at the LHC, called the compact muon solenoid (CMS) and Atlas, have released their first results—which show no sign of sparticles. That is no reason to abandon the theory, but it may mean that, if sparticles exist, they may be so heavy that supersymmetry runs into as many problems as it solves. Since there are many versions of the theory, an exhaustive search will take time. But as some theorists have spent much of their lives on supersymmetry, its demise would cause much gnashing and wailing.
When worlds collide
Most of the public discussion of extrasolar planets—those around other stars—has, since the discovery of the first of them in 1995, focused on whether there are other Earth-like, habitable worlds. But the less solipsistic and perhaps more tractable question is whether our solar system is typical in the cosmos. Our view of planetary diversity is being broadened by Nasa’s Kepler space observatory, launched in 2009 to scan the stars for extrasolar planets. Among the 170 multi-planet systems seen in the first four and a half months of its operation is a truly mind-boggling one called KOI-730, in which two planets run along a single orbit, one a sixth of a full revolution in front of the other, like two racing cars on the same track.
This possibility had been recognised in theory; the 60-degree angle of separation is the only arrangement in which two such planets can remain stable without one spinning off to its own orbit. Even then, the lagging planet may catch up, with apocalyptic results. Far from being unlikely, it has been suggested this happened to the Earth: that in the early solar system it had a smaller, co-orbiting partner with which it collided, some of the debris forming the Moon. Too much scanning?
Cancer risks from marginal sources is such a fraught issue that you’d expect any scientist to think carefully before suggesting new ones. Yet biophysicist David Brenner is no crank fretting about radio masts, but director of Columbia University’s Centre for Radiological Research. He fears that too many children are being given large doses of X-rays from unnecessary computed tomography (CT) scans for conditions that could be assessed with other techniques.
No one disputes that the dangers of individual scans are minuscule. But with use of them skyrocketing, says Brenner, tiny numbers add up. As Science magazine reports, this is a potentially incendiary claim. One Yale radiologist points out that “no one has conclusively shown that medical radiation has caused cancer,” and the matter can barely be raised without panicking patients. But the debate at least highlights the laxity of regulation for CT scanning. The X-ray dosage per scan varies widely, and some scans do seem to be needless. It’s a reminder that new technologies need careful chaperoning when they meet clinical practice.
