Oxford Literary Festival
April 4, 2025
It was a lovely sunny Spring day in Oxford. I gave a talk at the Oxford Literary Festival about my black hole book, A CRACK IN EVERYTHING. Very engaged audience. Question I really liked: “But what does it MEAN for time to be warped?” (See below, where I have attempted an answer)
If there is a supermassive black hole in the heart of every galaxy, there must be on in our Galaxy. And there is, the 4.2 million-solar-mass Sagittarius A*
Maarten Schmidt discovered quasars, which pump out 100 times the light of a typical galaxy and we now know are powered by supermassive black holes
A black hole is a bottomless pit in space-time from which nothing, not even light, can climb out – which is of course why it is black
Supermassive black holes are tiny – often only the size of the Solar System – but they project their power via titanic “jets” that stab outwards through galaxies for millions of light years
NASA’s Hubble Space Telescope made the discovery that there is a supermassive black hole in the heart of essentially every galaxy
Einstein in his rock ‘n’ roll years: He never believed in black holes, despite the fact they were a prediction of his own theory of gravity
Exeter College on a very sunny morning: I had to report to the Green Room there before being taken to the venue of my event
What does it MEAN for time to be warped?
We think of there being 3 dimensions of space – north-south, east-west, up-down – and one of time – past-future. But, in fact, Einstein in 1905 discovered that it is impossible to define intervals in space without reference to the time and intervals of time without reference to space. Space and time are hopelessly intermingled and there are actually 4 space-time dimensions.
Later, in 1915, Einstein discovered that gravity is nothing more than the warpage of space-time by energy – most commonly, mass-energy. So, for instance, the mass of the Sun creates a valley in the space-time around it and the Earth circles the upper reaches of that valley like a roulette ball in a roulette wheel.
But, remember, it’s space-time not merely space that is being warped. So there is an effect on time. If you stand on one step of the staircase below a friend, time flows more slowly for you than them. This effect of time being warped/slowed by gravity has to be taken into account by your smart phone or satnav in calculating your location relative to global positioning satellites. If your phone did not compensate for this warpage/slowing of time, it would get your location wrong by an extra 50 metres every day.