We know that the universe is constantly expanding. As we go back in time, the universe is contracting. If we rewind back enough time , around 13.7 billion years, by the time the Big Bang happened, all the matter in the universe was transformed into an incredibly hot, infinitely dense speck of matter. That is, the entire universe reduced to the size of a single atom. This subatomic ball is known as a singularity.
But what happened before that? What happened before the Big Bang? Famous physicist Stephen Hawking has an answer for it. He featured it in an interview with popular astrophysicist Neil deGrasse Tyson on the latest ‘Star Talk’ show on the National Geographic Channel.
Hawking’s answer to the question “What was there before there was something?” It is based on a theory known as the “boundless proposal”: “The boundary condition of the universe is … that it has no boundary,” the British physicist simply told Tyson. This is it, nothing.
But just because your answer can be summed up in one word, it doesn’t mean it’s not complicated. Luckily for us, Hawking is one of the best science communicators in the world and in his interview with Tyson, Hawking used the shape of the Earth as an analogy for the curved shape of the space-time continuum.
Inside this huge little mass of heat and energy, the laws of physics and time as we know them stop working. In other words, time as we literally understand it did not exist before the universe began to expand . Rather, the arrow of time contracts infinitely as the universe gets smaller and smaller and never reaches a clear starting point.
“According to Einstein’s theory of general relativity, space and time come together for a space-time continuum that is not flat but is curved by matter and the energy it contains,” Hawking said.
To explain it further, Hawking used the Euclidean approach to quantum gravity. In the Euclidean approach, ordinary real time is replaced by imaginary time, which behaves like a fourth dimension.
“In the Euclidean approach, the history of the universe in imaginary time is a four-dimensional curved surface like the surface of the Earth, but with two more dimensions,” Hawking clarified.
So does that mean there are six dimensions in all?
According to Hawking, the universe has no limits. In other words, the Euclidean space-time continuum is an endless closed surface, something like the surface of the Earth. “There is nothing south of the South Pole, so there was nothing before the Big Bang,” says the physicist.
Just as there is nothing south of a point further south, time cannot exist before the Big Bang. Instead, time and space expand and extend outward from this singular point in time, like degrees of latitude on planet Earth.
