sorry, 忘记了~~不好意思~~
原文链接如下：
http://www.skyandtelescope.com/news/39867717.html
Most Powerful Gamma-Ray Burst May Point to New Physics
Observations from NASA’s Fermi Gamma-ray Space Telescope hint that all forms of light may not travel through space at the same speed. Very-high-energy gamma rays may be slowed down as they propagate through the quantum turbulence of space-time. If future observations bear this out, it will rock the foundations of modern physics, and perhaps point the way to a "theory of everything" that would help unify the twin pillars of 20th-century physics: Einstein’s general theory of relativity and quantum mechanics.
This artist’s concept depicts what a gamma-ray burst might look like if we could view it up close (this is not something we’d recommend). The explosion triggers two jets, whose particles travel no less than 99.9999 percent the speed of light.
European Southern Observatory
Fermi, formerly known as the Gamma-ray Large Area Space Telescope (GLAST), launched in June 2008. Its intended purpose is to the study the extreme universe — exploding stars, cosmic jets, annihilating particles, and other stuff that we don’t want happening near Earth. Soon after launch, Fermi started picking up gamma-ray bursts (GRBs), powerful explosions usually triggered by dying stars.
On September 16, 2008, Fermi picked up the most powerful GRB observed to date. The burst took place 12.2 billion years ago. Intriguingly, the highest-energy gamma rays from this GRB arrived later than the low-energy gamma rays. The higher a gamma ray’s energy, the shorter its wavelength. These high-energy gamma rays, detected by Fermi’s Large Area Telescope (LAT), have wavelengths one-thousandth the size of an atomic nucleus.
NASA’s Swift satellite picked up the X-ray afterglow of the September 16th gamma-ray burst.
NASA / Swift / Stefan Immler
As predicted by quantum mechanics, and as verified by countless laboratory experiments, space-time becomes turbulent at very tiny scales, as "virtual particles" pop into existence for fleeting moments. According to some theories that attempt to unify quantum mechanics with general relativity, very-short-wavelength gamma rays will "feel" this turbulence, which would retard their velocity. In other words, if these theories accurately describe nature, high-energy gamma rays travel slightly slower than the speed of light.
This effect would be so subtle it would be nearly impossible to measure in a laboratory experiment. But as Fermi project scientist Steve Ritz (NASA/Goddard Space Flight Center) notes, GRBs give us a chance to conduct the experiment in space by letting gamma rays run a very long race across the vast distances of intergalactic space. These explosions are so powerful they can be seen to immense distances. In fact, the September 16th burst is the most powerful observed to date, and was easily detected by Fermi. With Fermi’s ability to detect very-high-energy gamma rays, and pin down their sky coordinates, it is uniquely suited to carry out this experiment.
The 16.5-second delay for the highest-energy gamma ray observed in this burst is consistent with some of these theories of quantum gravity, which is an exciting development. But before Fermi’s scientists uncork their champagne bottles, they must rule out alternative explanations. And this will require observations of many more GRBs.
After all, the most straightforward interpretation of the time delay seen in the September 16th burst is that the mechanism that produced the burst created the highest-energy gamma rays a few seconds later than their lower-energy counterparts. "Burst emissions at these energies are still poorly understood, and Fermi is giving us the tools to figure them out," says LAT lead scientist Peter Michelson of Stanford University, whose team reports its results in the February 19th Science Express.
But over the next few years, Fermi will detect more and more bursts. If Fermi sees a time lag for high-energy gamma rays that becomes larger with increasing distance, this would present compelling evidence that these theories of quantum gravity are indeed telling us something profound about nature at its most fundamental scales. At that time, Fermi scientists may do more than just uncork the champagne; they can start reserving themselves a round-trip ticket to Stockholm.
"This one burst raises all sorts of questions," says Michelson. "In a few years, we'll have a fairly good sample of bursts, and we may have some answers." |
置顶卡
变色卡
千斤顶
显身卡
实在是佩服各位的理论基础及能力~~~我已经晕了~~