Science

What Stephen Hawking's Last Theory Has To Say About The Universe

What Stephen Hawking's Last Theory Has To Say About The Universe

The two scientists also offer mathematical guidelines for astronomers to seek evidence about the existence of these possible parallel universes.

This formulation, derived from Hawking's research with his American colleague James Hartle in the 1980s, posed a massive problem, if there are infinite universes with infinite variations in their physical laws, there is no way to predict which Universe we are in. This theory isn't so simple as it's made in comics - it's not as if we've just got a bunch of versions of our Earth floating around out there somewhere. The paper was submitted just ten days before Hawking died. The paper - titled "A smooth exit from eternal inflation?" - has now been published in the Journal of High Energy Physics.

One of the implications in this new paper is that, according to Hertog, it could be possible to detect the presence of other universes by looking at the microwave radiation left over from the big bang.

However, in their co-publication, Hawking and Hertog say that despite being formed amidst radically different laws of physics, the individual universes may not be that different from one another. "It reduces the multiverse down to a more manageable set of universes which all look alike".

Speaking of his collaboration with Hawking, Hertog admitted that he thought it would be their last work together: "I always had the impression that he never wanted to quit and, in a way, this was Hawking".

Stephen's paper also implies that it might be possible to test this theory.




The European Space Agency has a project underway to build gravitational wave detectors in space that should be sensitive enough to find the faint signals Hertog talks about. That stated that the universe didn't have what we could understand as a beginning, because the singularity that existed pre-Big Bang had no initial time or space boundaries.

He added: "It's a theory that envisages a beginning to the universe where time is not present but our notion of time crystallises".

The concept depends on the term "eternal inflation". The belief is that once this process started, it never really stopped.

"The usual theory of eternal inflation predicts that globally our universe is like an infinite fractal, with a mosaic of different pocket universes, separated by an inflating ocean", Hawking explained. "I personally felt this might be the conclusion of our journey, but I never told him", recounts the Belgian professor at the Catholic University of Leuven. If the scale of different universes in the multiverse is large or infinite the theory can't be tested.

Hawking and Hertog's paper relies on string theory, a branch of physics that tries to reunite quantum physics with gravity and Einstein's theory of relativity.

Hertog told Cambridge that the physics that would account for infinite parallel universes break down when applied to the theory of eternal inflation.