Professor Stephen Hawking in 2006. Credit: Wikipedia
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Physicist/mathematician Stephen Hawking has improved after spending the night at a hospital near his home in Cambridge, England, and the 67-year-old’s condition was described as “comfortable.” Hawking’s first wife, Jane, was quoted that she believed his illness was no longer life-threatening. A spokesperson for Cambridge University, where Prof Hawking holds the post of Lucasian Professor of Mathematics, said that he would be kept in hospital for observation. “He is comfortable and his family is looking forward to him making a full recovery,” said Gregory Hayman. “He has had a good night but will be kept in at Addenbrooke’s Hospital for observation. He is showing signs of improvement.”
Hawking, best known as the author of the best-selling science book A Brief History of Time, was taken to hospital two days after returning from a tour of engagements in the United States. Cambridge University took the unprecedented step of commenting on Hawking’s condition, describing him as “very ill”.
Hawking suffers from ALS (amyotrophic lateral sclerosis), an incurable degenerative disorder also known as Lou Gehrig’s disease. He is wheelchair bound and only able to speak with the help of a voice synthesiser.
He was diagnosed with the muscle-wasting disease at the age of 21, which has gradually robbed him of his voice and movement in his limbs.
At the time of being diagnosed with the disease, he was told that he could expect to live for two years but has become one of the oldest-known survivors of the disease, after more than 40 years.
Stephen Hawking at NASA's StarChild Learning Center in the 1980s. Credit: NASA
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Famed theoretical physicist Stephen Hawking has been rushed to a hospital and is seriously ill. Cambridge University released information today that Hawking has been fighting a chest infection for several weeks, and was taken to a hospital in Cambridge.”Professor Hawking is very ill,” said Gregory Hayman, the university’s head of communications. “He is undergoing tests. He has been unwell for a couple of weeks.” Hawking, 67, is well known for his work on black holes, and has remained active despite being diagnosed at 21 with ALS, (amyotrophic lateral sclerosis), an incurable degenerative disorder also known as Lou Gehrig’s disease.
For several years, Hawking has been almost entirely paralyzed, and he communicates through an electronic voice synthesizer.
“Professor Hawking is a remarkable colleague. We all hope he will be amongst us again soon,” said Professor Peter Haynes, head of the university’s Department of Applied Mathematics and Theoretical Physics.
Hawking had canceled an appearance at Arizona State University on April 6 because of his illness.
He announced last year that he would step down from his post as Lucasian Professor of Mathematics, a title once held by the great 18th century physicist Isaac Newton, and the end of this academic year. However, the university said Hawking intended to continue working as Emeritus Lucasian Professor of Mathematics.
Hawking has described himself as “lucky” despite his disease[29]. Its slow progression has allowed him time to make influential discoveries and it has not hindered him from having a very full life.
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Researchers from the European Space Agency are testing what they describe as the smallest, yet most precisely controllable engine ever built for space. Measuring 10 centimeters (4 inches) across and making a faint blue glow as it runs, the Field Emission Electric Propulsion, or FEEP, engine produces an average thrust equivalent to the force of one falling hair. But its thrust range and controllability are far superior to more potent thrusters, and will be important for a future space mission that will test Einstein’s General Theory of Relativity.
“Most propulsion systems are employed to get a vehicle from A to B,” explained Davide Nicolini of the agency’s Scientific Projects Department, in charge of the engine research. “But with FEEP, the aim is to maintain a spacecraft in a fixed position, compensating for even the tiniest forces perturbing it, to an accuracy that no other engine design can match.”
Watching how objects behave when separated from all outside influences is a long-time ambition of physicists, but it can’t be done within Earth’s gravity field. So a next-decade mission called the LISA Pathfinder (Laser Interferometer Space Antenna) will fly 1.5 million km (900,000 miles) to one of the Lagrangian points, L-1. There, the Sun and Earth’s gravities cancel each other out, so that the behavior of a pair of free-floating test objects can be precisely monitored.
But to detach the experiment fully from the rest of the Universe there will still be some remaining per-turbations to overcome, most notably the slight but continuous pressure of sunlight itself. That’s where FEEP comes in. It operates on the same basic principle as other ion engines flown aboard ESA’s SMART-1 Moon mission and other spacecraft: the application of an electric field serves to accelerate electrically-charged atoms (known as ions), producing thrust.
But while the thrust of other ion engines is measured in millinewtons, FEEP’s performance is assessed in terms of micronewtons – a unit one thousand times smaller. The engine has a thrust range of 0.1 – 150 micronewtons, with a resolution capability better than 0.1 micronewtons in a time response of one-fifth of a second (190 milliseconds) or better.
The engine uses liquid metal caesium as propellant. Through capillary action—a phenomenon associated with surface tension—caesium flows between a pair of metal surfaces that end in a razor-sharp slit. The caesium stays at the mouth of the slit until an electric field is generated. This causes tiny cones to form in the liquid metal which have charged atoms shooting from their tips to create thrust.
Twelve thrusters will be used for the LISA Pathfinder. Working together with another propulsions system designed by NASA, the thrusters should yield directional control at least 100 times more accurate than any spacecraft before; down to a millionth of a millimeter.
LISA involves three satellites up to five million km (three million miles) apart and linked by lasers, orbiting the Sun. The aim is to detect ripples in space and time known as gravitational waves, predicted by Einstein’s theory of general relativity but so far undetected. The waves would cause tiny variations in the distance measured between the satellites.
The engine was tested last month, and once the tests are analyzed and the concept is proven, the FEEP technology has been earmarked for a broad range of other missions, including precision formation flying for astronomy, Earth observation and drag-free satellites for mapping variations in Earth’s gravity.
Just when I was getting excited about the possibility of travelling to distant worlds, scientists have uncovered a deep flaw with faster-than-light-speed travel. There appears to be a quantum limit on how fast an object can travel through space-time, regardless of whether we are able to create a bubble in space-time or not…
First off, we have no clue about how to generate enough energy to create a “bubble” in space-time. This idea was first put on a scientific grounding Michael Alcubierre from the University of Mexico in 1994, but before that was only popularized by science fiction universes such as Star Trek. However, to create this bubble we need some form of exotic matter fuel some hypothetical energy generator to output 1045 Joules (according to calculations by Richard K. Obousy and Gerald Cleaver in the paper “Putting the Warp into Warp Drive“). Physicists are not afraid of big numbers, and we are not afraid of words like “hypothetical” and “exotic”, but to put this energy in perspective, we would need to turn all of Jupiter’s mass into energy to even hope to distort space-time around an object.
This is a lot of energy.
If a sufficiently advanced human race could generate this much energy, I would argue that we would be masters of our Universe anyway, who would need warp drive when we could just as well create wormholes, star gates or access parallel universes. Yes, warp drive is science fiction, but it’s interesting to investigate this possibility and open up physical scenarios where warp drive might work. Let’s face it, anything less than light-speed travel is a real downer for our potential to travel to other star systems, so we need to keep our options open, not matter how futuristic.
The space-time bubble. Unfortunately, quantum physics may have the final word (Richard K Obousy & Gerald Cleaver, 2008)Although warp speed is highly theoretical, at least it is based on some real physics. It’s a mix of superstring and multi-dimensional theory, but warp speed seems to be possible, assuming a vast supply of energy. If we can “simply” squash the tightly curled extra-dimensions (greater than the “normal” four we live in) in front of a futuristic spacecraft and expand them behind, a bubble of stationary space will be created for the spacecraft to reside in. This way, the spaceship isn’t travelling faster than light inside the bubble, the bubble itself is zipping through the fabric of space-time, facilitating faster-than-light-speed travel. Easy.
Not so fast.
According to new research on the subject, quantum physics has something to say about our dreams of zipping through space-time faster than c. What’s more, Hawking radiation would most likely cook anything inside this theoretical space-time bubble anyway. The Universe does not want us to travel faster than the speed of light.
“On one side, an observer located at the center of a superluminal warp-drive bubble would generically experience a thermal flux of Hawking particles,” says Stefano Finazzi and co-authors from the International School for Advanced Studies in Trieste, Italy. “On the other side, such Hawking flux will be generically extremely high if the exotic matter supporting the warp drive has its origin in a quantum field satisfying some form of Quantum Inequalities.”
In short, Hawking radiation (usually associated with the radiation of energy and therefore loss of mass of evaporating black holes) will be generated, irradiating the occupants of the bubble to unimaginably high temperatures. The Hawking radiation will be generated as horizons will form at the front and rear of the bubble. Remember those big numbers physicists aren’t afraid of? Hawking radiation is predicted to roast anything inside the bubble to a possible 1030K (the maximum possible temperature, the Planck temperature, is 1032K).
Even if we could overcome this obstacle, Hawking radiation appears to be symptomatic of an even bigger problem; the space-time bubble would be unstable, on a quantum level.
“Most of all, we find that the RSET [renormalized stress-energy tensor] will exponentially grow in time close to, and on, the front wall of the superluminal bubble. Consequently, one is led to conclude that the warp-drive geometries are unstable against semiclassical back-reaction,” Finazzi adds.
However, if you wanted to create a space-time bubble for subluminal (less-than light speed) travel, no horizons form, and therefore no Hawking radiation is generated. In this case, you might not be beating the speed of light, but you do have a fast, and stable way of getting around the Universe. Unfortunately we still need “exotic” matter to create the space-time bubble in the first place…
Sources: “Semiclassical instability of dynamical warp drives,” Stefano Finazzi, Stefano Liberati, Carlos Barceló, 2009, arXiv:0904.0141v1 [gr-qc], “Investigation into Compactified Dimensions: Casimir Energies and Phenomenological Aspects,” Richard K. Obousy, 2009, arXiv:0901.3640v1 [gr-qc]
An international collaboration of astronomers is reporting an unusual spike of atmospheric particles that could be a long-sought signature of dark matter.
The orbiting PAMELA satellite, an astro physics mission operated by Italy, Russia, Germany and Sweden, has detected a glut of positrons — antimatter counterparts to electrons — in the energy range theorized to be associated with the decay of dark matter. The results appear in this week’s issue of the journal Nature.
Dark matter is the unseen substance that accounts for most of the mass of our universe, and the presence of which can be inferred from gravitational effects on visible matter. When dark matter particles are annihilated after contact with anti-matter, they should yield a variety of subatomic particles, including electrons and positrons.
Antiparticles account for a small fraction of cosmic rays and are also known to be produced in interactions between cosmic-ray nuclei and atoms in the interstellar medium, which is referred to as a ‘secondary source.”
Previous statistically limited measurements of the ratio of positron and electron fluxes have been interpreted as evidence for a primary source for the positrons, as has an increase in the total electron-positron flux at energies between 300 and 600 GeV. Primary sources could include pulsars, microquasars or dark matter annihilation.
Lead study author Oscar Adriani, an astrophysics researcher at the University of Florence in Italy, and his colleagues are reporting a positron to electron ratio that systematically increases in a way that could indicate dark matter annihilation.
The new paper reports a measurement of the positron fraction in the energy range 1.5–100GeV.
“We find that the positron fraction increases sharply over much of that range, in a way that appears to be completely inconsistent with secondary sources,” the authors wrote in the Nature paper. “We therefore conclude that a primary source, be it an astrophysical object or dark matter annihilation, is necessary.” Another feasible source for the anitmatter particles, besides dark matter annihilation, could be a pulsar, they note.
PAMELA, which stands for a Payload for Antimatter Matter Exploration and Light Nuclei Astrophysics, was launched in June 2006 and initially slated to last three years. Mission scientists now say it will continue to collect data until at least December 2009, which will help pin down whether the positrons are coming from dark matter anihilation or a single, nearby source.
Source: Nature (there is also an arXiv/astro-ph version here)
The hits just keep on coming from Department of Energy’s Fermi National Accelerator Laboratory. So far this month, the lab has announced the discovery of a rare single top quark, and then narrowed the gap — twice, actually — for the mass of the elusive Higgs Boson particle, or “God particle,” thought to give all other particles their mass.
Now, scientists have detected a new, completely untheorized particle that challenges what physicists thought they knew about how quarks combine to form matter. They’re calling it Y(4140), reflecting its measured mass of 4140 Mega-electron volts.
“It must be trying to tell us something,” said Jacobo Konigsberg of the University of Florida, a spokesman for Fermilab’s collider detector team. “So far, we’re not sure what that is, but rest assured we’ll keep on listening.”
The Standard Model of elementary particles and forces includes six quarks, which bind together to form composite particles. Credit: Fermilab
Matter as we know it comprises building blocks called quarks. Quarks fit together in various well-established ways to build other particles: mesons, made of a quark-antiquark pair, and baryons, made of three quarks.
But recently, electron-positron colliders at Stanford’s SLAC National Accelerator Laboratory and the Japanese laboratory KEK have revealed examples of composite quark structures — named X and Y particles — that are not the usual mesons and baryons. And now, the Collider Detector at Fermilab (CDF) collaboration has found evidence for the Y(4140) particle.
The Y(4140) particle decays into a pair of other particles, the J/psi and the phi, suggesting to physicists that it might be a composition of charm and anticharm quarks. However, the characteristics of this decay do not fit the conventional expectations for such a make-up. Other possible interpretations beyond a simple quark-antiquark structure are hybrid particles that also contain gluons, or even four-quark combinations.
The Fermilab scientists observed Y(4140) particles in the decay of a much more commonly produced particle containing a bottom quark, called the B+ meson. Sifting through trillions of proton-antiproton collisions from Fermilab’s Tevatron, they identified a small sampling of B+ mesons that decayed in an unexpected pattern. Further analysis showed that the B+ mesons were decaying into Y(4140).
The Y(4140) particle is the newest member of a family of particles of similar unusual characteristics observed in the last several years by experimenters at Fermilab’s Tevatron as well as at KEK and the SLAC lab, which operates at Stanford through a partnership with the U.S. Department of Energy.
“We congratulate CDF on the first evidence for a new unexpected Y state that decays to J/psi and phi,” said Japanese physicist Masanori Yamauchi, a KEK spokesperson. “This state may be related to the Y(3940) state discovered by Belle and might be another example of an exotic hadron containing charm quarks. We will try to confirm this state in our own Belle data.”
Theoretical physicists are trying to decode the true nature of these exotic combinations of quarks that fall outside our current understanding of mesons and baryons. Meanwhile, experimentalists happily continue to search for more such particles.
“We’re building upon our knowledge piece by piece,” said Fermilab spokesperson Rob Roser, “and with enough pieces, we’ll understand how this puzzle fits together.”
The Y(4140) observation is the subject of an article submitted by CDF to Physical Review Letters this week. Besides announcing Y(4140), the CDF experiment collaboration is presenting more than 40 new results at the Moriond Conference on Quantum Chromodynamics in Europe this week, including the discovery of electroweak top-quark production and a new limit on the Higgs boson, in concert with experimenters from Fermilab’s DZero collaboration.
The Standard Model describes the interactions of fundamental particles. The W boson, the carrier of the electroweak force, has a mass that is fundamentally relevant for many predictions, from the energy emitted by our sun to the mass of the elusive Higgs boson. Credit: Fermilab
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Scientists at the Department of Energy’s Fermi National Accelerator Laboratory have achieved the world’s most precise measurement of the mass of the W boson by a single experiment. Combined with other measurements, a tighter understanding of the W boson mass will also lead researchers closer to the mass of the elusive Higgs boson particle.
The Higgs particle is a theoretical but as yet unseen particle, also called the “God particle,” that is believed to give other particles their mass. The W boson, which is about 85 times heavier than a proton, enables radioactive beta decay and makes the sun shine.
Today’s announcement marks the second major discovery in a week for the international DZero collaboration at Fermilab. Earlier this week, the group announced the production of a single top quark at Fermilab’s Tevatron collider.
For the W mass precision measurement, the DZero collaboration analyzed about 500,000 decays of W bosons into electrons and neutrinos and determined the particle's mass with a precision of 0.05 percent. Credit: Fermilab
DZero is an international experiment of about 550 physicists from 90 institutions in 18 countries. It is supported by the U.S. Department of Energy, the National Science Foundation and a number of international funding agencies. In the last year, the collaboration has published 46 scientific papers based on measurements made with the DZero particle detector.
The W boson is a carrier of the weak nuclear force and a key element of the Standard Model of elementary particles and forces, which also predicts the Higgs boson. Its exact mass is crucial for calculations to estimate the likely mass of the Higgs boson by studying its subtle quantum effects on the W boson and the top quark, an elementary particle that was discovered at Fermilab in 1995.
Scientists working on the DZero experiment now have measured the mass of the W boson with a precision of 0.05 percent. The exact mass of the particle measured by DZero is 80.401 +/- 0.044 GeV/c^2. The collaboration presented its result at the annual conference on Electroweak Interactions and Unified Theories known as Rencontres de Moriond on Sunday.
“This beautiful measurement illustrates the power of the Tevatron as a precision instrument and means that the stress test we have ordered for the Standard Model becomes more stressful and more revealing,” said Fermilab theorist Chris Quigg.
The DZero team determined the W mass by measuring the decay of W bosons to electrons and electron neutrinos. Performing the measurement required calibrating the DZero particle detector with an accuracy around three hundredths of one percent, an arduous task that required several years of effort from a team of scientists including students.
Since its discovery at the European laboratory CERN in 1983, many experiments at Fermilab and CERN have measured the mass of the W boson with steadily increasing precision. Now DZero achieved the best precision by the painstaking analysis of a large data sample delivered by the Tevatron particle collider at Fermilab. The consistency of the DZero result with previous results speaks to the validity of the different calibration and analysis techniques used.
“This is one of the most challenging precision measurements at the Tevatron,” said DZero co-spokesperson Dmitri Denisov, of Fermilab. “It took many years of efforts from our collaboration to build the 5,500-ton detector, collect and reconstruct the data and then perform the complex analysis to improve our knowledge of this fundamental parameter of the Standard Model.“
This proton-antiproton collision, recorded by the DZero collaboration, is among the single top quark candidate events. The top quark decayed and produced a bottom quark jet (b jet), a muon and a neutrino. Credit: DZero collaboration.
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Scientists at Fermilab have observed particle collisions that produce single top quarks, a 1 in 20 billion find. This discovery confirms important parameters of particle physics, including the total number of quarks. Previously, top quarks had only been observed when produced by the strong nuclear force. That interaction leads to the production of pairs of top quarks. The production of single top quarks involves the weak nuclear force and is harder to identify experimentally. This observation occurred almost 14 years to the day of the top quark discovery in 1995.
Fermilab’s Tevatron, located near Chicago, Illinois is currently the world’s most powerful operating particle accelerator, and the discovery was made by scientists working on together on collaborations. Scientists say finding single top quarks has significance for the ongoing search for the Higgs particle. The Fermilab accelerator complex. Credit: Fermilab
“Observation of the single top quark production is an important milestone for the Tevatron program,” said Dr. Dennis Kovar, Associate Director of the Office of Science for High Energy Physics at the U.S. Department of Energy. “Furthermore, the highly sensitive and successful analysis is an important step in the search for the Higgs.”
Searching for single-top production makes finding a needle in a haystack look easy. Only one in every 20 billion proton-antiproton collisions produces a single top quark. Even worse, the signal of these rare occurrences is easily mimicked by other “background” processes that occur at much higher rates.
Discovering the single top quark production presents challenges similar to the Higgs boson search in the need to extract an extremely small signal from a very large background. Advanced analysis techniques pioneered for the single top discovery are now in use for the Higgs boson search. In addition, the single top and the Higgs signals have backgrounds in common, and the single top is itself a background for the Higgs particle.
To make the single-top discovery, physicists of the CDF and DZero collaborations spent years combing independently through the results of proton-antiproton collisions recorded by their experiments, respectively.
CDF is an international experiment of 635 physicists from 63 institutions in 15 countries. DZero is an international experiment conducted by 600 physicists from 90 institutions in 18 countries. The CDF detector, about the size of a 3-story house, weighs about 6,000 tons. Credit: Fermilab
Each team identified several thousand collision events that looked the way experimenters expect single top events to appear. Sophisticated statistical analysis and detailed background modeling showed that a few hundred collision events produced the real thing. On March 4, the two teams submitted their independent results to Physical Review Letters.
The two collaborations earlier had reported preliminary results on the search for the single top. Since then, experimenters have more than doubled the amount of data analyzed and sharpened selection and analysis techniques, making the discovery possible. For each experiment, the probability that background events have faked the signal is now only one in nearly four million, allowing both collaborations to claim a bona fide discovery that paves the way to more discoveries.
“I am thrilled that CDF and DZero achieved this goal,” said Fermilab Director Pier Oddone. “The two collaborations have been searching for this rare process for the last fifteen years, starting before the discovery of the top quark in 1995. Investigating these subatomic processes in more detail may open a window onto physics phenomena beyond the Standard Model.”
Space-time warping as a small black hole orbits a larger black hole (Don Davis)
[/caption]If you found yourself in the unfortunate situation of orbiting a black hole, you may be in for a rather dizzying and unpredictable ride. If the black hole is spinning, it will flatten out under centrifugal forces, much like the Earth bulges slightly at the equator, but the black hole’s bulge will be radically greater. As the shape of the black hole changes, so does its gravitational profile.
As you are not orbiting a spherical black hole, you can no longer expect to have a boring, predictable orbit; your orbit will become wild and chaotic, seemingly random. However, it would appear that there is an underlying constant to the mayhem, and what’s more, it seems this constant has also been observed in a more pedestrian system: a three-body Newtonian system. So what’s the link? Physicists aren’t quite sure…
When a massive star exhausts its fuel, it may collapse in on itself to create a black hole (after some exciting supernova action). The angular momentum of the original star is expected to be preserved, producing a rapidly spinning black hole. If the black hole “has no hair” (i.e. it has no electrical charge), the gravitational field solely depends on its mass and spin. If there is deformation due to the spin, the gravitational field changes, sending any orbiting body (like a neutron star) on a crazy roller-coaster ride.
In a new paper by Clifford Will of Washington University in St. Louis, the excited physicist describes the scenario. “The orbits go wild — they gyrate and spin, they’re incredibly complex. It’s fantastic,” Will says.
However, physicist Brandon Carter discovered a mathematical constant back in 1968, showing these apparently chaotic orbits are predictable, and that it even applies to orbits around extremely warped space-time. “Black holes have this extra constant that restores the regularity of the orbits,” comments Saul Teukolsky of Cornell University. “It’s a mystery. Every other situation where we have these extra constants, we have symmetry. But there’s no symmetry for an orbiting black hole — that’s why it is regarded as a miracle.”
Quite simply, physicists have no idea why the Carter constant could arise from the General Relativity description of a spinning black hole. Now, to make the problem even more perplexing, Will carried out a classical (Newtonian) 2-body simulation with a third body orbiting. Again, the same constant appeared. It would appear that there is something special about the predictability of an orbit around this black hole configuration.
Teukolsky, who worked on similar problems for his Ph.D. in 1970, remains baffled by these results. However, Will continues to investigate the problem, by including a term for black hole frame dragging. In this situation, the spinning black hole will drag space-time around it, “creases” (or ripples) in space time being pulled with the direction of spin. In this case, the Carter constant disappears, only to return when higher order terms are added to the equations.
This all means one of two things. Either it is simply an artefact in the mathematics, a curiosity that will eventually be rooted out of the equations. However, there is a tantalising possibility that we are seeing a characteristic of exotic rotating black holes, where the configuration of the surrounding fabric of space-time can allow a predictable orbit to come out of the apparent chaos…
A powerful laser could create the conditions inside a giant exoplanet (Sunbeamtech)
[/caption]We’ve all heard that the Large Hadron Collider (LHC) will collide particles together at previously unimaginable energies. In doing so, the LHC will recreate the conditions immediately after the Big Bang, thereby allowing us to catch a glimpse of what particles the Universe would have been filled with at this time. In a way, the LHC will be a particle time machine, allowing us to see the high energy conditions last seen immediately after the Big Bang, 13.7 billion years ago.
So, if we wanted to understand the conditions inside a giant exoplanet, how could we do it? We can’t directly measure it ourselves, we have to create a laboratory experiment that could recreate the conditions in the core of one of these huge exoplanet gas giants. Much like the LHC will recreate the conditions of the Big Bang, a powerful laser intended to kick-start fusion reactions will be used in an effort to help scientists have a very brief look into the cores of these distant worlds…
The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory in California is ready for action. The facility will perform fusion experiments, hopefully making a self-sustaining nuclear fusion reaction a reality using an incredibly powerful laser (firing at a hydrogen isotope fuel). Apart from the possibility of finding a way to kick-start a viable fusion energy source (other laboratories have tried, but only sustained fusion for an instant before fizzing out), the results from the laser tests will aid the management of the US nuclear weapon stockpile (since there have been no nuclear warhead tests in 15 years, data from the experiments may help the military deduce whether or not their bombs still work).
Fusion energy and nuclear bombs to one side, there is another use for the laser. It could be used to recreate the crushing pressures inside a massive exoplanet so we can glean a better understanding of what happens to matter at these crushing depths.
The NIF laser can deliver 500 trillion watts in a 20-nanosecond burst, which may not sound very long, but the energy delivered is immense. Raymond Jeanloz, an astronomer at the University of California, Berkeley, will have the exciting task of using the laser, aiming it at a small iron sample (800 micrometres in diameter), allowing him to generate a moment where pressures exceed a billion times atmospheric pressure. That’s 1000 times the pressure of the centre of the Earth.
On firing the laser, the heat will vaporize the iron, blasting a jet of gas so powerful, it will send a shock wave through the metal. The resulting compression is what will be observed and measured, revealing how the metal’s crystalline structure and melting point change at these pressures. The results from these tests will hopefully shed some light on the formation of the hundreds of massive exoplanets discovered in the last two decades.
“The chemistry of these planets is completely unexplored,” says Jeanloz. “It’s never been accessible in the laboratory before.”
