Most Powerful Gamma-Ray Burst May Point to New Physi ...

Most Powerful Gamma-Ray Burst May Point to New Physics-最强伽马射线爆发开启物理新视野
      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 ObservatoryFermi, 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 ImmlerAs 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."
     -----美国航空航天局费米伽马射线太空望远镜的观测活动中表明，宇宙中并非所有形式的光都是以相同的速度传播。超高能伽马射线在时空的量子乱流中传播时，其速度可能会降低。如果在今后的观测中能够证实这一点，它将会撼动整个现代物理学基础，而且也许能够为追寻“万物至理”指出一条明路，进而统一20世纪物理学的两大支柱理论学说：爱因斯坦的广义相对论和量子力学。
      这幅艺术想象图描绘的是在近处观察（我们可不建议这么做：））伽马射线爆发时的景象。爆发造成了两股喷流，喷流中的粒子以不低于99.9999%光速的速度传播。
      费米太空望远镜于2008年发射升空，它曾经称为“伽马射线大天区太空望远镜（GLAST）”。其主要目标就是研究宇宙中的极端现象——爆发中的恒星、宇宙喷流、湮灭粒子，以及其它那些我们根本不想发生在地球附近的现象。发射成功后不久，费米太空望远镜即开始收集伽马射线爆发（GRBs）的迹象，通常这种强烈的爆发是由濒死的恒星造成的。
      2008年9月16日，费米望远镜发现了迄今为止最为强烈的伽马射线爆发。此次爆发发生在122亿年以前。不过令人疑惑的是，爆发产生的低能伽马射线竟然早于超高能伽马射线到达地球。众所周知，伽马射线能量越高，则波长越短。这些“费米大天区望远镜（LAT）”所侦测到的高能伽马射线的波长仅相当于原子核大小的千分之一。
     天局“雨燕”号卫星捕捉到的伽马射线余晖，产生于9月16日伽马射线爆发过后。
     学理论以及经由无数实验室的验证，当“虚拟粒子”瞬间产生时，时空乱流的幅度是微乎其微的。而根据那些意图统一量子力学和广义相对论的学说判定，超短波长的伽马射线可以“触碰”乱流，致使其运行速度被拖慢。换句话说，如果这些学说完全切合实际情况的话，则高能伽马射线的传播速度要慢于光速。
    这种效应非常捉摸不定，基本上不可能在实验室得以验证。不过根据费米望远镜项目科学家史蒂夫·里茨（美国航空航天局/戈达德宇宙飞行中心）的说法，伽马射线爆发提供了一个在太空进行实验的机会，因为伽马射线需要穿过广阔的星系空间，这是一段非常遥远的距离。爆发具有极大的能量，所以在极远的距离也可以观察到。事实上，9月16日观测到的爆发是迄今为止最为强烈的，所以费米望远镜很容易就发现了它。费米望远镜所具备的侦测超高能伽马射线能力，能够锁定太空中的坐标，非常适于进行这一实验。
    在此次爆发中，观测到共计16.5秒的超高能伽马射线的时滞，这一结果与量子引力学的某些内容是一致的，同时这也是非常令人兴奋的学说进展。但在费米项目的科学家开香槟庆祝之前，他们必须排除其它一些解释的可能性。这就需要观测更多的伽马射线爆发目标。
    总而言之，9月16日的爆发中所见到的时滞最直接的解释就是，造成爆发的某种机制也同时造成了超高能伽马射线对比低能伽马射线的几秒延迟。“我们对这些能量中喷发的射线了解还非常少，而费米望远镜正要告诉我们答案，”LAT项目首席科学家——斯坦福大学的彼得·米歇尔森这样说道，他的科研小组在2月19日出版的《科学快讯》中阐述了研究成果。
    不过随着时间的推移，费米望远镜会不断发现更多的爆发点。如若费米望远镜能够发现高能伽马射线随着传播距离的增加而出现时滞，这就能压倒性地证明量子引力理论确实能够告诉我们一些事物最本初的性质。届时，费米项目的科学家们就不只是开香槟庆祝了；他们完全可以开始预订到斯德哥尔摩的往返机票。
    “这次爆发给我们提出了一系列的疑问，”米歇尔森说，“在今后的几年内，我们或许会发现更理想的爆发样本，从而获取一些问题的答案。”Most Powerful Gamma-Ray Burst May Point to New Physics-最强伽马射线爆发开启物理新视野
      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 ObservatoryFermi, 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 ImmlerAs 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."
     -----美国航空航天局费米伽马射线太空望远镜的观测活动中表明，宇宙中并非所有形式的光都是以相同的速度传播。超高能伽马射线在时空的量子乱流中传播时，其速度可能会降低。如果在今后的观测中能够证实这一点，它将会撼动整个现代物理学基础，而且也许能够为追寻“万物至理”指出一条明路，进而统一20世纪物理学的两大支柱理论学说：爱因斯坦的广义相对论和量子力学。
      这幅艺术想象图描绘的是在近处观察（我们可不建议这么做：））伽马射线爆发时的景象。爆发造成了两股喷流，喷流中的粒子以不低于99.9999%光速的速度传播。
      费米太空望远镜于2008年发射升空，它曾经称为“伽马射线大天区太空望远镜（GLAST）”。其主要目标就是研究宇宙中的极端现象——爆发中的恒星、宇宙喷流、湮灭粒子，以及其它那些我们根本不想发生在地球附近的现象。发射成功后不久，费米太空望远镜即开始收集伽马射线爆发（GRBs）的迹象，通常这种强烈的爆发是由濒死的恒星造成的。
      2008年9月16日，费米望远镜发现了迄今为止最为强烈的伽马射线爆发。此次爆发发生在122亿年以前。不过令人疑惑的是，爆发产生的低能伽马射线竟然早于超高能伽马射线到达地球。众所周知，伽马射线能量越高，则波长越短。这些“费米大天区望远镜（LAT）”所侦测到的高能伽马射线的波长仅相当于原子核大小的千分之一。
     天局“雨燕”号卫星捕捉到的伽马射线余晖，产生于9月16日伽马射线爆发过后。
     学理论以及经由无数实验室的验证，当“虚拟粒子”瞬间产生时，时空乱流的幅度是微乎其微的。而根据那些意图统一量子力学和广义相对论的学说判定，超短波长的伽马射线可以“触碰”乱流，致使其运行速度被拖慢。换句话说，如果这些学说完全切合实际情况的话，则高能伽马射线的传播速度要慢于光速。
    这种效应非常捉摸不定，基本上不可能在实验室得以验证。不过根据费米望远镜项目科学家史蒂夫·里茨（美国航空航天局/戈达德宇宙飞行中心）的说法，伽马射线爆发提供了一个在太空进行实验的机会，因为伽马射线需要穿过广阔的星系空间，这是一段非常遥远的距离。爆发具有极大的能量，所以在极远的距离也可以观察到。事实上，9月16日观测到的爆发是迄今为止最为强烈的，所以费米望远镜很容易就发现了它。费米望远镜所具备的侦测超高能伽马射线能力，能够锁定太空中的坐标，非常适于进行这一实验。
    在此次爆发中，观测到共计16.5秒的超高能伽马射线的时滞，这一结果与量子引力学的某些内容是一致的，同时这也是非常令人兴奋的学说进展。但在费米项目的科学家开香槟庆祝之前，他们必须排除其它一些解释的可能性。这就需要观测更多的伽马射线爆发目标。
    总而言之，9月16日的爆发中所见到的时滞最直接的解释就是，造成爆发的某种机制也同时造成了超高能伽马射线对比低能伽马射线的几秒延迟。“我们对这些能量中喷发的射线了解还非常少，而费米望远镜正要告诉我们答案，”LAT项目首席科学家——斯坦福大学的彼得·米歇尔森这样说道，他的科研小组在2月19日出版的《科学快讯》中阐述了研究成果。
    不过随着时间的推移，费米望远镜会不断发现更多的爆发点。如若费米望远镜能够发现高能伽马射线随着传播距离的增加而出现时滞，这就能压倒性地证明量子引力理论确实能够告诉我们一些事物最本初的性质。届时，费米项目的科学家们就不只是开香槟庆祝了；他们完全可以开始预订到斯德哥尔摩的往返机票。
    “这次爆发给我们提出了一系列的疑问，”米歇尔森说，“在今后的几年内，我们或许会发现更理想的爆发样本，从而获取一些问题的答案。”