 Everyone knows the score with black holes: even if light strays too close, the immense gravity will drag it inside, never to be seen again. They are thought to be created when large stars finally spend all their fuel and collapse. It might come as a surprise, therefore, to find that physicists in the UK have now managed to create an "artificial" black hole in the lab.
The group begins by sending a pulse of light through an optical fibre that, as a result of a phenomenon known as the Kerr effect, alters the local refractive index. A split-second later they send a “probe” beam of light, which has a wavelength long enough to travel faster through the fibre and catch up the pulse. But due to the altered refractive index around the pulse, the probe light is always slowed enough to prevent it from overtaking — so the pulse appears as a white hole. Likewise, if the group were to send the probe light from the opposite end of the fibre, it would reach the pulse but would not be able to go through to the other side — so the pulse would appear as a black hole.
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