A team of UBC physicists and engineers have designed a experiment featuring a trough of flowing water to help bolster a 35-year-old theory proposed by eminent physicist Stephen Hawking.
In 1974, Hawking predicted that black holes–often thought of having gravitational pulls so strong that nothing escapes from them–emit a very weak level of radiation. According to the theory, pairs of photons are torn apart by a black hole’s gravitational field–one photon falls into the black hole, but the other escapes as a form of radiation.
In results outlined in the latest issue of Physical Review Letters, a team of UBC researchers led by international post-doctoral researcher Silke Weinfurtner put the test to Hawking’s theory by creating a ‘white hole’ in a six-metre-long flume of flowing water.
Placing an airplane wing-shaped obstacle in the path of the flowing water created a region of high-velocity flow which blocked surface waves, generated downstream, from traveling upstream. The obstruction simulated a white hole, the temporal reverse of a black hole.
The shallow surface waves divided into pairs of deep-water waves, analogous to the photon pairs featured in Hawking’s theory. Like in black holes, they showed that the analog would also emit a thermal spectrum of radiation.
“While this creative simulation obviously doesn’t prove Hawking’s theory, it does show that his ideas apply broadly,” says UBC theoretical physicist William Unruh.