引力波通过能量过程（如空间中的黑洞碰撞）在时空结构中产生涟漪。人们一直认为它们会发生，但物理学家没有足够灵敏的设备来检测它们。这一切都在2016年发生了变化，当时测量了两个超大质量黑洞碰撞引力波。这是物理学家阿尔伯特爱因斯坦在20世纪早期进行的研究预测的重大发现。科学家Russel Hulse和Joseph H. Taylor探讨了引力波创造的一个可能想法。 1974年，他们发现了一种新型的脉冲星，这种脉冲星已经消失，但是在一颗巨星死亡之后，它仍然在迅速旋转。脉冲星实际上是一颗中子星，一颗中子球被压碎到一个小世界的大小，迅速旋转并发出辐射脉冲。 1916年，爱因斯坦正在研究他的广义相对论。他的工作的一个产物是他的广义相对论公式（称为他的场方程）的一组解决方案，允许引力波。问题是，没有人发现任何这样的事情。如果它们存在，那么它们将是如此令人难以置信的弱，以至于它们几乎不可能找到，而是单独测量。物理学家花费了20世纪的大部分时间来设计关于探测引力波和寻找宇宙中创造它们的机制的想法。搜索此类波浪背后的想法非常简单：如果它们存在，那么发射它们的物体将失去引力能量。这种能量损失是间接可检测的。通过研究二元中子星的轨道，这些轨道内的逐渐衰变将需要存在能够带走能量的引力波。为了找到这样的波，物理学家需要建立非常灵敏的探测器。在美国，他们建造了激光干涉引力波观测台（LIGO）。它整合了两个设施的数据，一个在华盛顿州汉福德，另一个在路易斯安那州利文斯顿。每一个都使用连接到精密仪器的激光束来测量引力波经过地球时的“摆动”。每个设施中的激光沿着四公里长的真空室的不同臂移动。如果没有影响激光的引力波，则光束在到达探测器时将彼此完全相位。如果存在引力波并对激光束产生影响，使它们甚至在质子宽度的1/10000波动，那么就会产生一种称为“干涉图案”的现象。经过多年的测试，2016年2月11日，从事LIGO项目的物理学家宣布他们已经检测到几个月前黑洞二元系统相互碰撞的引力波。令人惊奇的是，LIGO能够用光学精确的行为来检测，这些行为发生在光年之后。精度水平相当于测量距离最近的恒星的距离，误差小于人发的宽度！从那时起，也从黑洞碰撞现场发现了更多的引力波。中子星非常庞大，呈现出具有强引力场的物体类型，这些引力场也可能与引力波的产生有关。这两人因其工作获得了1993年诺贝尔物理学奖，这在很大程度上取决于爱因斯坦使用引力波的预测。
Gravitational waves are created as ripples in the fabric of space-time by energetic processes such as black hole collisions out in space. They were long thought to occur, but physicists didn’t have sensitive-enough equipment to detect them. That all changed in 2016 when gravitational waves from the collision of two supermassive black holes were measured. It was a major discovery predicted by research done early in the 20th century by physicist Albert Einstein. One possible idea for the creation of gravitational waves was probed by the scientists Russel Hulse and Joseph H. Taylor. In 1974, they discovered a new type of pulsar, the dead, but rapidly spinning hulk of mass left over after the death of a massive star. The pulsar is actually a neutron star, a ball of neutrons crushed to the size of a small world, spinning rapidly and sending out pulses of radiation. In 1916, Einstein was working on his theory of general relativity. One outgrowth of his work was a set of solutions to his formulas for general relativity (called his field equations) that allowed for gravitational waves. The problem was, nobody had ever detected any such thing. If they existed, they would be so incredibly weak that they would be virtually impossible to find, yet alone measure. Physicists spent much of the 20th Century devising ideas about detecting gravitational waves and looking for mechanisms in the universe that would create them. The idea behind searching for such waves is fairly simple: if they DO exist, then objects emitting them would lose gravitational energy. That loss of energy is indirectly detectable. By studying the orbits of binary neutron stars, the gradual decay within these orbits would require the existence of gravitational waves that would carry the energy away. To find such waves, physicists needed to build very sensitive detectors. In the U.S., they constructed the Laser Interferometry Gravitational Wave Observatory (LIGO). It unites data from two facilities, one in Hanford, Washington and the other in Livingston, Louisiana. Each one uses a laser beam attached to precision instruments to measure the “wiggle” of a gravitational wave as it passes by Earth. The lasers in each facility move along different arms of a four-kilometer-long vacuum chamber. If there are no gravitational waves affecting the laser light, the beams of light will be in complete phase with each other upon arriving at the detectors. If gravitational waves are present and have an effect on the laser beams, making them waver even 1/10,000th of a proton’s width, then a phenomenon called ” interference patterns” will result. After years of testing, on February 11, 2016, physicists working at with the LIGO program announced that they had detected gravitational waves from a binary system of black holes colliding with each other several months earlier. The amazing thing is that LIGO was able to detect with microscopic precision behavior that happened light-years away. The level of precision was equivalent to measuring the distance to the nearest star with a margin of error less than the width of a human hair! Since that time, more gravitational waves have been detected, also from the site of a black hole collision. Neutron stars are incredibly massive and presented the type of object with strong gravitational fields that might also be implicated in the creation of gravitational waves. The two men won the 1993 Nobel Prize in physics for their work, which drew largely upon Einstein’s predictions using gravitational waves.