AMEN: 四月 2013

2013年4月29日

gotta bet on sure things：谁将是小微企业业务王者（标题自设）

gotta bet on sure things：谁将是小微企业业务王者（标题自设） (http://goo.gl/mag/OE3Wu87)

2013年4月28日

爱因斯坦理论再次被证实是对的 Theory Of Einstein's Proved Right -- Again

科

学家们对爱因斯坦(Albert Einstein)的引力理论进行了迄今为止真实世界中最严苛的检验──结果证明，理论仍然成立。

AFP/Getty Images

爱因斯坦

爱因斯坦的广义相对论称，拥有质量的物体会导致时空弯曲，即我们所理解的引力。根据爱因斯坦的相对论，时空是一个由时间和空间组成的四维结构。

例如，一个保龄球可以让床垫上出现一处凹陷，这个凹陷改变了同一床垫上一个原本做直线运动的弹子的轨迹。与之相似，太阳的质量扭曲了周围的时空。质量较小的物体，比如地球，在这个扭曲的空间中沿着一个路线运动，我们称之为轨道。

科学家们检测这个广义理论并不是因为他们觉得理论错了，而是因为他们肯定地认为这个理论不是最终的解释，就像牛顿(Isaac Newton)的万有引力定律会被爱因斯坦的理论取代一样。

爱因斯坦的引力理论发表于近一个世纪之前，已经通过了迄今为止的所有检验。不过，科学家们一直在努力找出爱因斯坦的引力理论不再成立的精确条件，以及在哪个方面需要提出一个替代性的理论。例如，爱因斯坦的引力理论框架与量子理论相矛盾，量子理论解释了自然界在原子和亚原子水平上的运行规律。

这份研究报告发表在《科学》(Science)杂志上。德国马克斯•普朗克射电天文学研究所(Max Planck Institute for Radioastronomy)的天体物理学家、这份研究报告的作者之一弗莱雷(Paulo Freire)说，以黑洞为例思考，爱因斯坦的理论预测无限强大的引力场和密度，这是荒谬的。

弗莱雷和他的同事把一个距地球7,000光年的宇宙空间作为实验室，来检验爱因斯坦的理论。那里有两颗相互环绕的奇异星。

其中一颗奇异星是所谓的白矮星，它是一个质量轻得多的恒星的冷却遗迹。另一颗是每秒旋转25次的脉冲星。尽管这颗脉冲星的宽度只有12英里，其质量却是太阳的两倍。

苏格兰阿伯丁大学(University of Aberdeen)的理论物理学家Charles Wang说，在如此小的空间里拥有如此大的质量，会产生非常大的引力。Charles Wang没有参与这项研究。

脉冲星表面的引力是地球的3,000亿倍。那里的环境接近残酷、拥有无限能量的黑洞。黑洞连光线也能吞没。

弗莱雷说，爱因斯坦理论从来没有在这样一个环境中被检验过。

脉冲星和白矮星释放出引力波，这个双星系统逐渐失去能量。因此，这两颗星会相互靠近，在轨道上运行的速度也更快。

根据爱因斯坦的理论，这两颗恒星的轨道周期（即他们相互环绕一周所需的时间）每年应该减少大约0.000008秒。

弗莱雷和他的同事们使用了几台望远镜对这个双星系统进行了精确的测量。他们得出的结果与基于爱因斯坦理论的预测完全吻合。

Charles Wang说，尽管爱因斯坦的理论框架到目前为止仍然无懈可击，这项研究仍然很重要，因为天文学家的观察帮助发现了检测爱因斯坦引力理论的新的极端案例。

在爱因斯坦的理论发表后的第四年，这一理论在一次日食过程中首次被显著证实，他因此一下子成为了名人。在被问到如果他的理论被证明是错误的，他会作何感想时，爱因斯坦回答说：我会为上帝感到遗憾。这个理论是正确的。

GAUTAM NAIK

（本文版权归道琼斯公司所有，未经许可不得翻译或转载。）

http://cn.wsj.com/gb/20130426/bus114525.asp?source=whatnews2

Scientists have subjected Albert Einstein's famous theory of gravity to its toughest real-world test so far─and it has prevailed.

Einstein's general theory of relativity states that objects with mass cause a curvature in space-time, which we perceive as gravity. Space-time, according to Einstein's theories of relativity, is a four-dimensional fabric woven together by space and time.

For example, a bowling ball causes a dent in a mattress, and that dent changes the otherwise straight motion of a nearby marble on the same mattress. Similarly, the mass of the sun distorts the space-time around it. A body with less mass, like the earth, travels along one path in that distorted space, which we call its orbit.

Scientists aren't testing the general theory because they think it is wrong but rather because they are certain it can't be the final explanation─just as Isaac Newton's notion of gravitational force was superseded by Einstein's explanation.

Einstein's theory of gravity, published nearly a century ago, has passed every test it has been subjected to. Nonetheless, scientists have been trying to pin down precisely at what point Einstein's theory of gravity breaks down, and where an alternative explanation will have to be devised. Einstein's framework for his theory of gravity, for example, is incompatible with quantum theory, which explains how nature works at an atomic and subatomic level.

Consider that for a black hole, Einstein's theory 'predicts infinitely strong gravitational fields and density. That's nonsensical,' said Paulo Freire, an astrophysicist at the Max Planck Institute for Radioastronomy in Germany and co-author of the study, which appears in the journal Science.

Dr. Freire and his colleagues put Einstein to the test in a cosmic laboratory 7,000 light years from earth, where two exotic stars are circling each other.

One, known as a white dwarf, is the cooling remnant of a much lighter star. Its companion is a pulsar, which spins 25 times every second. Though the pulsar is just 12 miles across, it weighs twice as much as the sun.

'When you have such a big mass in such a small space you have extremely high gravity,' said Charles Wang, a theoretical physicist at the University of Aberdeen, Scotland, who wasn't involved in the study.

The gravity on the pulsar's surface is 300 billion times as great as the gravity on Earth. The conditions there approach the relentless, overwhelming power of a black hole, which swallows even light.

'We're testing Einstein's theory in a region where it has never been tested before,' said Dr. Freire.

The pulsar and white dwarf pair emit gravitational waves and the binary star system gradually loses energy. As a result, the stars will move closer to each other and orbit faster.

Einstein's theory suggests the stars' orbital periods─the time they take to go around each other─ought to shrink by about eight-millionths of a second per year.

Dr. Freire's and his colleagues used several telescopes to take precise measurements about the two-star system. Their results perfectly matched the Einstein-based prediction.

Though Einstein's framework remains intact so far, 'the study is significant for the way observations by astronomers are helping to identify new, extreme cases' to test his general theory of gravity, said Dr. Wang.

Einstein's theory was first─and dramatically─confirmed during a solar eclipse within four years of its publication, making him an instant celebrity. When asked how he would have felt if he had been proven wrong, Einstein replied: 'I would have felt sorry for the Lord. The theory is correct.'

GAUTAM NAIK

http://cn.wsj.com/gb/20130426/bus114525_ENversion.shtml