Black holes are essentially natural time machines that may be used to visit the past and the future. However, one shouldn't count on making a return trip to see dinosaurs any time soon. Our current spacecraft are incapable of approaching a black hole. As a caveat aside, Sam Baron, Associate Professor in Australian Catholic University, wrote a report in which he explained that traversing time using a black hole could be the last thing you want to do.
What are black holes?
A black hole is the result of the implosion of a massive star as it nears its latter stages of life.
Black holes, like planets and stars, have surrounding gravitational fields. What holds us to the planet and maintains the planet in orbit around the sun is a gravitational field.
Generally speaking, a larger item has a stronger gravitational field because of its greater mass.
According to Einstein's theory, matter and energy have an unusual impact on the universe. Space is expanded by energy and matter. Massive things bend and extend space.
Space valley is caused by a massive object. Objects approaching the valley plummet.
When you get close enough, you fall towards any large object, even a black hole. A black hole's sharp sides prevent light from escaping.
The valley of a black hole becomes steeper as you approach it. The event horizon is the point beyond which light cannot escape.
Stretching time
Time also expands as space does. Time moves more slowly when a clock is close to a large body than when it is closer to a smaller one.
A black hole's proximity will cause a clock's tick rate to be far slower than that of a clock on Earth. As shown in the film Interstellar, one year near a black hole may be equivalent to eighty years on Earth.
This is how time travel via black holes is possible. Flying near a black hole and then returning to Earth is like taking a time machine to the far future.
The catch
At the moment, there are three issues in time travelling. One can only go back in time one time via a black hole, for starters. Consequently, one won't be able to travel back far enough if the black hole was generated after the extinction of the dinosaurs.
Second, one have to go beyond the event horizon to join the conversation. This implies that leaving the event horizon is necessary for leaving the loop at a certain point in the past. That would require going faster than the speed of light, which we know to be impossible.
The third issue is spaghettification. You would be flattened like a noodle as you reached the event horizon. One would be so thin that you would dissolve into a whirlwind of atoms hurtling into nothing.
Black holes' time-warping characteristics are fascinating to consider, but any hope of really travelling back in time remains firmly in the domain of science fiction for now.
According to Sam BaronAssociate Professor, Philosophy of Science, Australian Catholic University
(With inputs from PTI)
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