天文学：宇宙运动的揭示 / ASTRONOMY: Cosmic Motion Revealed

 James Glanz 

天文学家们深入宇宙，发现它正在以越来越快的速度膨胀，这表明爱因斯坦在他提出填充“真空”空间的神秘能量时是正确的。

Astronomers peered deep into the universe and found that it is flying apart ever faster, suggesting that Einstein was right when he posited a mysterious energy that fills “empty” space

自然的最终命运和宇宙的命运几个世纪以来一直困扰着哲学家和科学家。几十年前，科学家们发现宇宙正在膨胀，其星系在各个方向飞散。但引力的作用可能会减缓这种膨胀，因此研究人员一直试图弄清楚宇宙的最终命运：它是否拥有足够的物质有一天会坍塌，或者它会永远膨胀下去。1998年，两组天文学家穿过时间和空间的巨大鸿沟来回答这个根本问题——他们甚至对自己的发现感到惊讶。

The nature and ultimate fate of the universe have preoccupied philosophers and scientists for centuries. Scientists discovered decades ago that the universe is now expanding, with its galaxies rushing apart in all directions. But the pull of gravity could slow that expansion, and so researchers have tried to work out the final destiny of the cosmos: whether there is enough matter to cause it to one day collapse on itself, or whether it will expand forever. In 1998 two teams of astronomers peered across an enormous gulf of time and space to answer that fundamental question—and amazed even themselves with what they found.

宇宙中的物质不仅不足以永远阻止膨胀，而且外向运动似乎正在加速，而不是减慢。同时，这一发现引发了关于空间性质的深刻问题，以至于宇宙学家们不禁怀疑宇宙的最终命运是否永远无法确定。

Not only is there too little matter in the universe to ever halt the expansion on its own, but the outward motion appears to be speeding up, not slowing down. At the same time, the finding raises such profound questions about the nature of space that cosmologists are wondering whether the ultimate fate of the universe can ever be known for certain.

这是一项天文学家能够深入过去的天才壮举，独立团队通过观察遥远的爆炸恒星（称为超新星）得出了他们的结论，这些超新星的亮度出奇地暗淡，揭示了加速使其远离地球的距离异常大。随着这些延伸到数十亿光年之外的宇宙的发现，天文学家们在宇宙最深邃、最神秘的过去获得了稳固的立足点。我们将他们的发现——这些发现改变了我们对宇宙的看法，并为物理学提出了新的基本问题——称为1998年度突破。

In a triumph for astronomers' ability to look deep into the past, the independent teams came to their conclusions by observing far-off exploding stars called supernovae that turn out to be surprisingly dim, revealing an acceleration that has swept them to unexpectedly large distances from Earth. With these results, reaching billions of light-years into space, astronomers have gained a secure foothold in the deepest and most mysterious reaches of the cosmic past. We name their findings, which transform our view of the universe and pose fundamental new questions for physics, as Breakthrough of the Year for 1998.

更增添了发现的戏剧性的是，加速膨胀最简单的解释是一种奇怪的能量，它在大尺度上抵消引力，将物质推开——这是阿尔伯特·爱因斯坦在1917年提出的一个想法，后来被认为是不正确的。今年的发现表明，宇宙中大部分能量是以这种形式存在的，爱因斯坦称之为宇宙常数，或lambda。因为物质和能量是可互换的，这个巨大的能量库意味着宇宙中的物质，从桌椅到恒星和星系团，可能只是创造物中微不足道的一部分。

Adding to the drama of the find, the simplest explanation for the accelerating expansion is a bizarre energy that on large scales counteracts gravity, pushing matter apart, an idea that Albert Einstein posited in 1917 and later rejected. This year's discoveries suggest that most of the energy of the universe is in this form, which Einstein called the cosmological constant, or lambda. Because matter and energy are interchangeable, this huge energy reservoir means that the universe of matter, from tables and chairs to stars and clusters of galaxies, may be but the minor portion of creation.

这些启示如此深刻和令人不安，以至于世界各地的天文学家仍在试图反驳这一说法，以找出任何可能造成宇宙加速的假象。迄今为止，他们尚未成功，因此物理学家们正争相解释宇宙能量的起源。lambda符号，λ，再次出现在天文和物理学期刊的方程中，新的结果催生了一个小型的理论搜索产业，寻找更奇特的加速膨胀的可能性。

These implications are so profound and unsettling that astronomers around the world are still trying to disprove the finding, to uncover anything that could create a false impression of cosmic acceleration. To date they have been unsuccessful, and so physicists are rushing to explain the origin of the cosmic energy. The lambda symbol, λ, is once again sprinkled throughout equations in the astronomy and physics journals, and the new results have inaugurated a small industry of theoretical searches for even quirkier possibilities for boosting the expansion.

回到1917年，当爱因斯坦提出这个常数时，他和他的同事们认为宇宙是静止的，既不膨胀也不坍塌。他在方程中引入了宇宙排斥力，以防止宇宙因其内部物质的引力而坍塌。

Back in 1917, when Einstein proposed the constant, he and other scientists thought that the universe was static, neither expanding nor collapsing. He put the cosmic repulsion into his equations to prevent the universe from collapsing on itself from the gravitational pull of the matter inside it.

但到了1929年，天文学家埃德温·哈勃仰望星空，震惊了当时的科学界，发现宇宙确实在膨胀。宇宙诞生于一个称为大爆炸的热致密状态，被比作一场烟火表演，其最辉煌的时刻已经过去。就像烟火的余烬一样，最初相互靠近的星系今天在缓慢地分开，而那些一开始距离稍远一些的星系正在以高速相互远离。从我们银河系的视角来看，任何其他星系远离的速度都可以通过其光的“红移”来测量——频率的下降和波长的增加，类似于一列远去的火车喇叭音调的下降。

But by 1929, astronomer Edwin Hubble had peered into the heavens and startled the scientific world of his day by discovering that the universe is in fact expanding. Born in a hot, dense state called the big bang, the cosmos has been likened to a display of fireworks whose most brilliant moments are behind it. Like fading cinders in the fireworks, galaxies that were initially close to each other are today drifting apart slowly, while those that began slightly further apart are flying away from each other at higher speeds. From our vantage point in the Milky Way, the speed at which any other galaxy is moving away can be clocked using the “redshift” of its light—a drop in frequency and increase in wavelength akin to the dip in pitch of a receding train's whistle.

但测量星系的实际距离是困难的。哈勃通过观察称为造父变星的恒星的视亮度来做到这一点，它们的内在亮度是已知的；因此，这些恒星可以作为“标准烛光”来测量距离，因为更远的造父变星看起来更暗。哈勃比较了红移和距离，发现了膨胀。

But gauging a galaxy's actual distance is difficult. Hubble managed it by observing the apparent brightness of stars called Cepheid variables, whose intrinsic brightness is known; these stars can thus be used as “standard candles” to measure distance, as more distant Cepheids appear dimmer. Hubble compared the redshifts with the distances and discovered the expansion.

爱因斯坦接受了哈勃的发现。但他认为，如果膨胀是原始爆炸的遗迹，那么宇宙常数——他觉得让方程不美观——就不需要了。他收回了这个想法，并称之为他“最大的错误”。

Einstein accepted Hubble's find. But he reasoned that if the expansion was a relic of a primeval explosion, the cosmological constant—which he felt made the equations unaesthetic—wasn't needed. He withdrew the idea and called it his “biggest blunder.”

随着宇宙学家们继续研究膨胀宇宙的概念，他们得出结论，在宇宙120亿到150亿年的生命中，由于每颗星系对其他星系施加的引力作用，膨胀会略微减慢。但要发现这种变化需要深入研究过去，观察数十亿光年外闪烁的恒星——这个距离太远，无法看到造父变星。

As cosmologists continued to work with the notion of an expanding cosmos, they concluded that over the 12- to 15-billion-year life of the universe, the expansion would slow slightly, thanks to the pull of gravity that every galaxy exerts on every other. But spotting such a change requires probing deep into the past by looking at stars glittering billions of light-years away—too far away for Cepheids to be seen

因此，在过去的20年里，天文学家们转向了一种新型标准烛光：最亮的超新星，它几乎每次都会以相同的方式发生。但这些明亮、巨大的爆炸很少见——典型的旋涡星系每千年只会爆发两到三次。为了找到足够多的超新星，天文学家们会在一个晚上对大片天空进行电子成像，捕捉数万个遥远的星系，然后在几周后再次对同一区域成像。一旦图像在计算机上叠加并减去，任何新的超新星都会显现出来，并可以被观测直到它们消失。

So for the past 20 years, astronomers have turned to a new kind of standard candle: the brightest kind of supernova, which happens nearly the same way each time. But these bright, massive explosions are rare—only two or three erupt in a typical spiral galaxy per millennium. To find enough of them, astronomers make electronic images of large swaths of sky in a single night, capturing tens of thousands of distant galaxies, and then image the same areas a few weeks later. Once the images are overlaid and subtracted on a computer, any new supernovae leap out and can be observed until they fade away.

这两个团队（成员遍布欧洲、拉丁美洲、澳大利亚和美国）在过去几年里效率越来越高地收集了他们的超新星数据，期望找出引力在多大程度上减缓了宇宙的膨胀。今年早些时候，两个团队都宣布他们的期望被颠倒了：超新星相对暗淡的光芒表明，即使在物质稀少的宇宙中，它们也比预期的要远10%到15%，这表明膨胀在数十亿年里已经加速了。年底时，经过数十颗超新星的分析、发表或正在发表，这些结论得到了证实。

The two teams, both of which have members in Europe, Latin America, Australia, and the United States, collected their supernova data with increasing efficiency over the last few years, expecting to find out by how much gravity was slowing cosmic expansion. Early this year, both teams announced that their expectations had been turned upside down: The relative dimness of the supernovae showed that they are 10% to 15% farther out than expected even in a universe with little matter, indicating that the expansion has accelerated over billions of years. At year's end, with dozens of supernovae analyzed, published, or in press, those conclusions stand.

这一发现重现了一种神秘的排斥力，它抵消了引力，而lambda是最可能的候选者。早期的迹象表明，从宇宙演化的理论和对宇宙大尺度结构的观测来看，宇宙的质量很小，可能存在lambda，但这个想法通常被认为是荒谬的。现在lambda又一次变得合乎逻辑，爱因斯坦也被证明是正确的，尽管原因是他无法预见的。事实上，lambda似乎在宇宙中占主导地位：在最简单的理论图景中，超新星数据意味着宇宙能量的70%是lambda形式，只有30%是物质。

That finding resurrects a mysterious repulsion that counteracts gravity, with lambda as the most likely candidate. There were earlier hints, from theories of cosmic evolution and observations of the large-scale structure of the universe, that the cosmos holds little mass and that there might be a lambda, but the idea was generally considered outlandish. Now lambda is respectable once more, and Einstein is proved right, albeit for reasons he could not have foreseen. In fact lambda appears to be dominant in the universe: In the simplest theoretical picture, the supernova data imply that 70% of the universe's energy is in the form of lambda and only 30% is matter.

物理学家们后来将lambda解释为量子力学效应：即“真空”空间中闪烁出现的短暂粒子提供了一个能量源，赋予空间弹性，使其向外推。但到目前为止，计算表明这种lambda应该比超新星团观测到的要大几个数量级。这个谜团引发了对新物理学原理的探索，例如空间结构中的对称性，这些原理可以帮助抵消方程中的巨大项。这种奇怪能量的其他候选者，如“精质”和“X物质”，也被提出，因为物理学家们正在争夺解释宇宙大部分由什么组成的奖励。而且，由于这些能量形式中的一些可能会随时间变化，因此宇宙学家们对于声明数十万亿年后宇宙的命运变得不那么确定了。

Physicists have since interpreted lambda as a quantum-mechanical effect: that the evanescent particles that flicker in and out of existence in “empty” space provide a well of energy that gives space its springiness, shoving it apart. But so far, calculations suggest that such a lambda should be many orders of magnitude larger than the supernova groups have seen. That puzzle has launched a search for new physics principles, such as symmetries in the fabric of space, that might help cancel out huge terms in the equations. Other candidates for this strange energy, which go by names like quintessence and X-matter, have also been put forth, as physicists vie for the prize of explaining what most of the universe is made of. And because some of those forms of energy may change over time, cosmologists have become less confident about declaring the fate of the universe hundreds of billions of years hence.

事实上，此时宇宙常数仍然停留在理论领域；没有人确切知道导致宇宙不断加速的原因。天文学家们继续收集数据，并寻找除加速之外的其他效应来解释他们的发现。但尽管他们付出了努力，他们却没有发现任何理由怀疑他们的工作。虽然宇宙的本质曾经主要属于哲学家，但在1998年，宇宙学似乎有数据支撑，因为遥远的超新星的景象揭示了宇宙的真实本质——也许还有它的未来。科学家和哲学家都将在未来几年里应对其影响。

Indeed, at this point the cosmological constant remains in the realm of theory; no one yet knows the precise nature of the energy causing the universe to fly apart ever faster. Astronomers continue to gather data and to search for any effect other than acceleration that could explain their findings. But despite their efforts, they have found no reason to doubt their work. Although the nature of the universe was once chiefly the realm of philosophers, in 1998 it seems that cosmology is grounded in data, as visions of distant supernovae revealed the true nature—and perhaps the future—of the cosmos. Scientists and philosophers both will be grappling with the implications for years to come.

• James Glanz

自然的最终命运和宇宙的命运几个世纪以来一直困扰着哲学家和科学家。几十年前，科学家们发现宇宙正在膨胀，其星系在各个方向飞散。但引力的作用可能会减缓这种膨胀，因此研究人员一直试图弄清楚宇宙的最终命运：它是否拥有足够的物质有一天会坍塌，或者它会永远膨胀下去。1998年，两组天文学家穿过时间和空间的巨大鸿沟来回答这个根本问题——他们甚至对自己的发现感到惊讶。

The nature and ultimate fate of the universe have preoccupied philosophers and scientists for centuries. Scientists discovered decades ago that the universe is now expanding, with its galaxies rushing apart in all directions. But the pull of gravity could slow that expansion, and so researchers have tried to work out the final destiny of the cosmos: whether there is enough matter to cause it to one day collapse on itself, or whether it will expand forever. In 1998 two teams of astronomers peered across an enormous gulf of time and space to answer that fundamental question—and amazed even themselves with what they found.

宇宙中的物质不仅不足以永远阻止膨胀，而且外向运动似乎正在加速，而不是减慢。同时，这一发现引发了关于空间性质的深刻问题，以至于宇宙学家们不禁怀疑宇宙的最终命运是否永远无法确定。

Not only is there too little matter in the universe to ever halt the expansion on its own, but the outward motion appears to be speeding up, not slowing down. At the same time, the finding raises such profound questions about the nature of space that cosmologists are wondering whether the ultimate fate of the universe can ever be known for certain.

这是一项天文学家能够深入过去的天才壮举，独立团队通过观察遥远的爆炸恒星（称为超新星）得出了他们的结论，这些超新星的亮度出奇地暗淡，揭示了加速使其远离地球的距离异常大。随着这些延伸到数十亿光年之外的宇宙的发现，天文学家们在宇宙最深邃、最神秘的过去获得了稳固的立足点。我们将他们的发现——这些发现改变了我们对宇宙的看法，并为物理学提出了新的基本问题——称为1998年度突破。

In a triumph for astronomers' ability to look deep into the past, the independent teams came to their conclusions by observing far-off exploding stars called supernovae that turn out to be surprisingly dim, revealing an acceleration that has swept them to unexpectedly large distances from Earth. With these results, reaching billions of light-years into space, astronomers have gained a secure foothold in the deepest and most mysterious reaches of the cosmic past. We name their findings, which transform our view of the universe and pose fundamental new questions for physics, as Breakthrough of the Year for 1998.

更增添了发现的戏剧性的是，加速膨胀最简单的解释是一种奇怪的能量，它在大尺度上抵消引力，将物质推开——这是阿尔伯特·爱因斯坦在1917年提出的一个想法，后来被认为是不正确的。今年的发现表明，宇宙中大部分能量是以这种形式存在的，爱因斯坦称之为宇宙常数，或lambda。因为物质和能量是可互换的，这个巨大的能量库意味着宇宙中的物质，从桌椅到恒星和星系团，可能只是创造物中微不足道的一部分。

Adding to the drama of the find, the simplest explanation for the accelerating expansion is a bizarre energy that on large scales counteracts gravity, pushing matter apart, an idea that Albert Einstein posited in 1917 and later rejected. This year's discoveries suggest that most of the energy of the universe is in this form, which Einstein called the cosmological constant, or lambda. Because matter and energy are interchangeable, this huge energy reservoir means that the universe of matter, from tables and chairs to stars and clusters of galaxies, may be but the minor portion of creation.

这些启示如此深刻和令人不安，以至于世界各地的天文学家仍在试图反驳这一说法，以找出任何可能造成宇宙加速的假象。迄今为止，他们尚未成功，因此物理学家们正争相解释宇宙能量的起源。lambda符号，λ，再次出现在天文和物理学期刊的方程中，新的结果催生了一个小型的理论搜索产业，寻找更奇特的加速膨胀的可能性。

These implications are so profound and unsettling that astronomers around the world are still trying to disprove the finding, to uncover anything that could create a false impression of cosmic acceleration. To date they have been unsuccessful, and so physicists are rushing to explain the origin of the cosmic energy. The lambda symbol, λ, is once again sprinkled throughout equations in the astronomy and physics journals, and the new results have inaugurated a small industry of theoretical searches for even quirkier possibilities for boosting the expansion.

回到1917年，当爱因斯坦提出这个常数时，他和他的同事们认为宇宙是静止的，既不膨胀也不坍塌。他在方程中引入了宇宙排斥力，以防止宇宙因其内部物质的引力而坍塌。

Back in 1917, when Einstein proposed the constant, he and other scientists thought that the universe was static, neither expanding nor collapsing. He put the cosmic repulsion into his equations to prevent the universe from collapsing on itself from the gravitational pull of the matter inside it.

但到了1929年，天文学家埃德温·哈勃仰望星空，震惊了当时的科学界，发现宇宙确实在膨胀。宇宙诞生于一个称为大爆炸的热致密状态，被比作一场烟火表演，其最辉煌的时刻已经过去。就像烟火的余烬一样，最初相互靠近的星系今天在缓慢地分开，而那些一开始距离稍远一些的星系正在以高速相互远离。从我们银河系的视角来看，任何其他星系远离的速度都可以通过其光的“红移”来测量——频率的下降和波长的增加，类似于一列远去的火车喇叭音调的下降。

But by 1929, astronomer Edwin Hubble had peered into the heavens and startled the scientific world of his day by discovering that the universe is in fact expanding. Born in a hot, dense state called the big bang, the cosmos has been likened to a display of fireworks whose most brilliant moments are behind it. Like fading cinders in the fireworks, galaxies that were initially close to each other are today drifting apart slowly, while those that began slightly further apart are flying away from each other at higher speeds. From our vantage point in the Milky Way, the speed at which any other galaxy is moving away can be clocked using the “redshift” of its light—a drop in frequency and increase in wavelength akin to the dip in pitch of a receding train's whistle.

但测量星系的实际距离是困难的。哈勃通过观察称为造父变星的恒星的视亮度来做到这一点，它们的内在亮度是已知的；因此，这些恒星可以作为“标准烛光”来测量距离，因为更远的造父变星看起来更暗。哈勃比较了红移和距离，发现了膨胀。

But gauging a galaxy's actual distance is difficult. Hubble managed it by observing the apparent brightness of stars called Cepheid variables, whose intrinsic brightness is known; these stars can thus be used as “standard candles” to measure distance, as more distant Cepheids appear dimmer. Hubble compared the redshifts with the distances and discovered the expansion.

爱因斯坦接受了哈勃的发现。但他认为，如果膨胀是原始爆炸的遗迹，那么宇宙常数——他觉得让方程不美观——就不需要了。他收回了这个想法，并称之为他“最大的错误”。

Einstein accepted Hubble's find. But he reasoned that if the expansion was a relic of a primeval explosion, the cosmological constant—which he felt made the equations unaesthetic—wasn't needed. He withdrew the idea and called it his “biggest blunder.”

随着宇宙学家们继续研究膨胀宇宙的概念，他们得出结论，在宇宙120亿到150亿年的生命中，由于每颗星系对其他星系施加的引力作用，膨胀会略微减慢。但要发现这种变化需要深入研究过去，观察数十亿光年外闪烁的恒星——这个距离太远，无法看到造父变星。

As cosmologists continued to work with the notion of an expanding cosmos, they concluded that over the 12- to 15-billion-year life of the universe, the expansion would slow slightly, thanks to the pull of gravity that every galaxy exerts on every other. But spotting such a change requires probing deep into the past by looking at stars glittering billions of light-years away—too far away for Cepheids to be seen

因此，在过去的20年里，天文学家们转向了一种新型标准烛光：最亮的超新星，它几乎每次都会以相同的方式发生。但这些明亮、巨大的爆炸很少见——典型的旋涡星系每千年只会爆发两到三次。为了找到足够多的超新星，天文学家们会在一个晚上对大片天空进行电子成像，捕捉数万个遥远的星系，然后在几周后再次对同一区域成像。一旦图像在计算机上叠加并减去，任何新的超新星都会显现出来，并可以被观测直到它们消失。

So for the past 20 years, astronomers have turned to a new kind of standard candle: the brightest kind of supernova, which happens nearly the same way each time. But these bright, massive explosions are rare—only two or three erupt in a typical spiral galaxy per millennium. To find enough of them, astronomers make electronic images of large swaths of sky in a single night, capturing tens of thousands of distant galaxies, and then image the same areas a few weeks later. Once the images are overlaid and subtracted on a computer, any new supernovae leap out and can be observed until they fade away.

这两个团队（成员遍布欧洲、拉丁美洲、澳大利亚和美国）在过去几年里效率越来越高地收集了他们的超新星数据，期望找出引力在多大程度上减缓了宇宙的膨胀。今年早些时候，两个团队都宣布他们的期望被颠倒了：超新星相对暗淡的光芒表明，即使在物质稀少的宇宙中，它们也比预期的要远10%到15%，这表明膨胀在数十亿年里已经加速了。年底时，经过数十颗超新星的分析、发表或正在发表，这些结论得到了证实。

The two teams, both of which have members in Europe, Latin America, Australia, and the United States, collected their supernova data with increasing efficiency over the last few years, expecting to find out by how much gravity was slowing cosmic expansion. Early this year, both teams announced that their expectations had been turned upside down: The relative dimness of the supernovae showed that they are 10% to 15% farther out than expected even in a universe with little matter, indicating that the expansion has accelerated over billions of years. At year's end, with dozens of supernovae analyzed, published, or in press, those conclusions stand.

这一发现重现了一种神秘的排斥力，它抵消了引力，而lambda是最可能的候选者。早期的迹象表明，从宇宙演化的理论和对宇宙大尺度结构的观测来看，宇宙的质量很小，可能存在lambda，但这个想法通常被认为是荒谬的。现在lambda又一次变得合乎逻辑，爱因斯坦也被证明是正确的，尽管原因是他无法预见的。事实上，lambda似乎在宇宙中占主导地位：在最简单的理论图景中，超新星数据意味着宇宙能量的70%是lambda形式，只有30%是物质。

That finding resurrects a mysterious repulsion that counteracts gravity, with lambda as the most likely candidate. There were earlier hints, from theories of cosmic evolution and observations of the large-scale structure of the universe, that the cosmos holds little mass and that there might be a lambda, but the idea was generally considered outlandish. Now lambda is respectable once more, and Einstein is proved right, albeit for reasons he could not have foreseen. In fact lambda appears to be dominant in the universe: In the simplest theoretical picture, the supernova data imply that 70% of the universe's energy is in the form of lambda and only 30% is matter.

物理学家们后来将lambda解释为量子力学效应：即“真空”空间中闪烁出现的短暂粒子提供了一个能量源，赋予空间弹性，使其向外推。但到目前为止，计算表明这种lambda应该比超新星团观测到的要大几个数量级。这个谜团引发了对新物理学原理的探索，例如空间结构中的对称性，这些原理可以帮助抵消方程中的巨大项。这种奇怪能量的其他候选者，如“精质”和“X物质”，也被提出，因为物理学家们正在争夺解释宇宙大部分由什么组成的奖励。而且，由于这些能量形式中的一些可能会随时间变化，因此宇宙学家们对于声明数十万亿年后宇宙的命运变得不那么确定了。

Physicists have since interpreted lambda as a quantum-mechanical effect: that the evanescent particles that flicker in and out of existence in “empty” space provide a well of energy that gives space its springiness, shoving it apart. But so far, calculations suggest that such a lambda should be many orders of magnitude larger than the supernova groups have seen. That puzzle has launched a search for new physics principles, such as symmetries in the fabric of space, that might help cancel out huge terms in the equations. Other candidates for this strange energy, which go by names like quintessence and X-matter, have also been put forth, as physicists vie for the prize of explaining what most of the universe is made of. And because some of those forms of energy may change over time, cosmologists have become less confident about declaring the fate of the universe hundreds of billions of years hence.

事实上，此时宇宙常数仍然停留在理论领域；没有人确切知道导致宇宙不断加速的原因。天文学家们继续收集数据，并寻找除加速之外的其他效应来解释他们的发现。但尽管他们付出了努力，他们却没有发现任何理由怀疑他们的工作。虽然宇宙的本质曾经主要属于哲学家，但在1998年，宇宙学似乎有数据支撑，因为遥远的超新星的景象揭示了宇宙的真实本质——也许还有它的未来。科学家和哲学家都将在未来几年里应对其影响。

Indeed, at this point the cosmological constant remains in the realm of theory; no one yet knows the precise nature of the energy causing the universe to fly apart ever faster. Astronomers continue to gather data and to search for any effect other than acceleration that could explain their findings. But despite their efforts, they have found no reason to doubt their work. Although the nature of the universe was once chiefly the realm of philosophers, in 1998 it seems that cosmology is grounded in data, as visions of distant supernovae revealed the true nature—and perhaps the future—of the cosmos. Scientists and philosophers both will be grappling with the implications for years to come.

• James Glanz