Gravitational Waves Exist: The Inside Story of How Scientists Finally Found Them
By Nicola Twilley
Just
over a billion years ago, many millions of galaxies from here, a pair
of black holes collided. They had been circling each other for aeons, in
a sort of mating dance, gathering pace with each orbit, hurtling closer
and closer. By the time they were a few hundred miles apart, they were
whipping around at nearly the speed of light, releasing great shudders
of gravitational energy. Space and time became distorted, like water at a
rolling boil. In the fraction of a second that it took for the black
holes to finally merge, they radiated a hundred times more energy than
all the stars in the universe combined. They formed a new black hole,
sixty-two times as heavy as our sun and almost as wide across as the
state of Maine. As it smoothed itself out, assuming the shape of a
slightly flattened sphere, a few last quivers of energy escaped. Then
space and time became silent again.
The
waves rippled outward in every direction, weakening as they went. On
Earth, dinosaurs arose, evolved, and went extinct. The waves kept going.
About fifty thousand years ago, they entered our own Milky Way galaxy,
just as Homo sapiens were beginning to replace our Neanderthal
cousins as the planet’s dominant species of ape. A hundred years ago,
Albert Einstein, one of the more advanced members of the species,
predicted the waves’ existence, inspiring decades of speculation and
fruitless searching. Twenty-two years ago, construction began on an
enormous detector, the Laser Interferometer Gravitational-Wave
Observatory (LIGO). Then, on September 14, 2015, at just
before eleven in the morning, Central European Time, the waves reached
Earth. Marco Drago, a thirty-two-year-old Italian postdoctoral student
and a member of the LIGO Scientific Collaboration, was
the first person to notice them. He was sitting in front of his computer
at the Albert Einstein Institute, in Hannover, Germany, viewing the LIGO
data remotely. The waves appeared on his screen as a compressed
squiggle, but the most exquisite ears in the universe, attuned to
vibrations of less than a trillionth of an inch, would have heard what
astronomers call a chirp—a faint whooping from low to high. This
morning, in a press conference in Washington, D.C., the LIGO team announced that the signal constitutes the first direct observation of gravitational waves.
