Black Hole Blues and Other Songs from Outer Space

by Janna Levin

When challenged on the use of the atomic bomb, he would respond as he did in his autobiography: “One cannot escape the conclusion that an atomic bomb program started a year earlier and concluded a year sooner would have spared 15 million lives, my brother Joe’s among them.”

Summarizing the decades of contributions, there are three stellar death states: Stars like our Sun will die as white dwarfs, a cool sphere of degenerate matter comparable in size to the Earth, the pressure of densely packed electrons enough to resist total collapse. Heavier dead stars will stably end as neutron stars, an even denser sphere of degenerate nuclear matter around 20 to 30 kilometers across, the pressure of densely packed neutrons enough to resist total collapse. But the heaviest stars have no more recourse to nuclear pressures. Unhindered collapse is inevitable.

Conceptually, gravitational waves are required out of respect for the speed limit. As one black hole orbits another, the curves in the shape of spacetime must drag around with them, but the shape of spacetime cannot acclimate instantaneously, since that would require propagation of information—about the motion of the holes—faster than the speed of light. As the black holes move, the curves shift and adjust, and those changes wave outward incrementally and at the speed of light, carrying energy away from the violent astrophysical motions.

When the Vikings invaded they conferred derogatory names on the local inhabitants. He says Richan meant “dregs” and Drever

meant “rubbish.”)

Proportions alternate between infinitesimal and astronomical. The signals are infinitesimal. The sources are astronomical. The sensitivities are infinitesimal. The rewards are astronomical. The human ambition to understand the universe is merely epic, and astronomical trumps epic.

Quasars are the energetic output of the entire core of an ancient galaxy shining bright enough for us to see at considerable distances.

They observed the orbit of the pulsar to decay ever so slightly, one full rotation taking 76.5 microseconds less every year, and deduced that energy must be drained from the orbit to cause the dissipation. The energy loss is precisely as predicted by Einstein’s theory of gravity. The orbiting neutron stars drag the curves in spacetime around with them and pump energy into waves in the spacetime geometry. Or, more plainly, the lost energy is carried off in gravitational waves, in the sound of spacetime. Theory and experiment fit together snugly in this fortunate observation.

Two of the largest holes in the Earth’s atmosphere are in those LIGO beam tubes, just there beyond the double doors of the control room. There’s less stuff in those tubes than there is in the empty space between galaxies, which has a very little bit of stuff known as the intergalactic medium. Two of the biggest holes in the atmosphere and eight times less stuff than parts of outer space. (Although the emptiest regions of outer space are emptier still.)

The Sun and the Moon cause the mirrors to sway, and magnets are required to restore the mirrors to their baseline location. There are also seismometers to detect local motions of the Earth with attendant hydraulic systems to compensate for those displacements. All of this constitutes forms of noise, to be distinguished from a bona fide signal. We listen to the raw sounds of the instrument. It whirs with the tidal pull of the celestial bodies, the grumbling of a still-settling Earth, the remnants of heat in the elements, the quantum vibrations and the pressure of the laser.

The entire air hangar is maintained as a class 10,000 clean room, which tolerates about that many dust-sized motes per cubic foot. In comparison, on average New York has at least a million contaminants per cubic foot of the microbe or dust or chemical variety.

Still, powerful astrophysicists from Princeton University, John Bahcall and Jerry Ostriker, opposed LIGO. “There was a conspiracy against me at Princeton. They were worried LIGO would take money away from astronomy. Noble reasons.”

A reference to the Advanced Development Programs of the aerospace and defense corporation Lockheed Martin, the term “skunkworks” has some utopian tones, suggesting an unrestricted incubator. In Burbank in 1943, in around six months, Lockheed developed the first U.S. jet fighter, the P-80 Shooting Star, under a circus tent that accumulated unpleasant smells from a nearby plastics factory. The R&D technicians wisecracked that the odor matched imagined emanations from the moonshine factory Skonk Works in the comic strip Li’l Abner. The name stuck with modest permutation and became an alias for the Lockheed project.

Kip said emphatically, “Barry Barish is the most skilled manager of large-scale projects we’ve ever had in the world.” The view is widely held, possibly even held unanimously among those with an informed opinion.

Somewhere in the universe two black holes collide, an event as powerful as any since the origin of the universe, outputting more than a trillion times the power of a billion Suns. That profusion of energy emanates from the coalescing holes in a purely gravitational form, as waves in the shape of spacetime, as gravitational waves.

The collision sent us the most powerful single event we have ever detected since the big bang, the power in gravitational waves a hundred billion trillion times the luminosity of the sun. The detectors caught the final four orbits of a black hole 29 times the mass of the Sun in a pair with a black hole 36 times the mass of the Sun.