If space-time can curve, then it can also wiggle. Spotting those wiggles,
turns out, is really hard.
A hundred years ago or so, Einstein published his General Theory of
Relativity which said that space and time aren’t just the background arena
for stuff in the universe to do things in — space-time *is* the stuff of
the universe. It curves and interacts with matter and energy. As the great
physicist J.A. Wheeler put it, “Matter tells spacetime how to curve.
Spacetime tells matter how to move.”
Along with all the other mind-bending predictions of General Relativity
came one elegant prediction: space-time can wiggle. Energetic events in the
universe should create gravitational waves that propagate outwards across
the cosmos, similar to the way electromagnetic waves (or, as call them,
‘light’) are emitted by accelerating electrons.
The prediction was easy, but a quick calculation showed a bit of a problem
with detection. These gravitational waves are tiny. Like, really small.
Brain-breakingly weak. So weak, it took a hundred years to catch one moving
through a pair of insanely sensitive detectors called LIGO.
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