As of 6:30 EST the 2017 winners of the Nobel Prize in physics were announced! The winners were Rainer Weiss, Kip Thorne, and Barry Barish. Weiss is a professor at MIT while Thorne and Barish teach at Cal Tech. They won the Nobel Prize because they were the first physicists to observe gravitational waves, or space-time distortions. These gravitational waves are believed to have originated from the collision of two massive black holes over a billion light years away!
Even more astounding is that this discovery confirms Einstein’s General Theory of Relativity, which he formulated 100 years ago without the sophisticated technology we take for granted today. His theory states that matter and energy would warp the geometry of space-time, producing gravity. This theory has numerous implications. His equations predicted that the universe was expanding from what we call the Big Bang. In this case, it predicted that massive objects like black holes would create ripples in space-time. The energy released from the collision of these black holes is still spreading outwards via these gravitational waves, which can stretch and compress space in a manner similar to how sound waves compress air. However the farther these waves travel the shorter the motion of their stretching and compressing, and, the harder they are to detect. We can think of the stretching-compressing motion of these waves the same way we think of our spring force (FS). After we stretch out the spring to its maximum potential energy, it begins to compress and stretch until it eventually runs out of kinetic energy. Thinking about the magnitude of energy emanating from the collision of the black holes, and the wide expanses of the universe they travelled to make it here, makes humanity seem so insignificant in the grand scheme of the cosmos.
So how could these physicists detect such a cataclysmic event that occurred billions of years ago? They developed LIGO: The Laser Interferometer Gravitational Wave Observatory. The LIGO detector has an L-shaped antenna with arms 2.5 miles long that contain mirrors made from ultra-pure glass at each end. The laser is split and sent to the mirrors of each arm and measures the distance between the two. If the arms are precisely the same length, the returning beams cancel each other out and no light is detected. But, since gravitational waves move in a stretching and compressing fashion, if one passed through the Earth, it would stretch one mirror and compress the other one. In this case, a discrepancy of one part in a billion trillion, a fraction of the width of a proton, misaligned the beams, causing the detector to record a rhythmic pulse from the wave. The future implications of this research are extensive. We can learn more about the big bang and the inception of our universe!
It’s also so interesting to learn about gravitational waves in the context of what we learn in class. We typically have only considered gravity as a force that dictates kinematic motion. However, the discovery of these gravitational waves poses this idea of an all-encompassing record of the history of space-time, and our universe.