This computer simulation shows the warping of space and time around two colliding black holes observed by LIGO on September 14, 2015. The colored surface is space represented as a two-dimensional sheet with one of the three space dimensions removed. The funnel-shaped warping is produced by the black hole's huge mass. The colors near the black holes depict the rate at which time flows: green, normal; yellow, slowed by 20 or 30 percent; red, hugely slowed. The bottom shows the waveform, or wave shape, of the emitted gravitational waves, which carry away energy, causing the black holes to spiral inward and collide._Image: Simulating eXtreme Spacetimes
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