Dying Stephen Hawking changed his mind about Big Bang theory

Famed physicist revised key idea shortly
before his death in March

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The newly published paper – completed ten days before the
physicist’s death on 14 March, at the age of 76 – ditches the “no
boundary theory” that he devised with fellow researcher James
Hartle back in 1983. 

The pair proposed that prior to the Big Bang, there was space
but no time. So the universe expanded from a single point when it
began, but has no time boundaries, making it infinite.

This idea “resolved a difficulty with Einstein’s theory that
suggested that the universe began nearly 14 billion years ago but
said nothing about how it began”, says the BBC. Yet while Hawking and Hartle had
“tied up one loose end”, the new theory created another, the
broadcaster adds.

The “no boundary theory” implies that the Big Bang would have
led to the creation of infinite universes, each exhibiting physical
laws that differ from others.

But if the Big Bang were to birth an infinite number of possible
universes, all with different laws of physics, most of them would
be hostile to the stable existence of the matter that makes up
stars, planets and human beings – and of physics itself as we know
it.

As a result, it would remain impossible to explain why the
physics of our own universe work as they do, given the variations
that other universes may experience.

However, in his final paper, submitted to the Journal of High Energy Physics, Hawking and
fellow physicist Thomas Hertog revised the theory, suggesting that
the universe does have a boundary – which makes for a “simpler set
of alternate universes”, The Times reports.

In the new theory, instead of space being filled with countless
universes where entirely different laws of physics apply, these
alternate universes may not actually vary that much from one
another.

According to The Guardian, the new theory “may provide
some comfort to physicists who wonder how, given all the hostile
variations thought possible, we find ourselves in a universe
well-suited to life”.

“In the old theory there were all sorts of universes: some were
empty, others were full of matter, some expanded too fast, others
were too short-lived. There was huge variation,” Hertog explains.
“The mystery was why do we live in this special universe where
everything is nicely balanced in order for complexity and life to
emerge?

“[The new theory] reduces the multiverse down to a more
manageable set of universes which all look alike. Stephen would say
that, theoretically, it’s almost like the universe had to be like
this. It gives us hope that we can arrive at a fully predictive
framework of cosmology.”