Prof Stephen Hawking's final research paper suggests that our Universe may be one of many similar to our own.
The theory resolves a cosmic paradox of the late physicist's own making.
It also points a way forward for astronomers to find evidence of the existence of parallel universes.
The study was submitted to the Journal of High-Energy Physics 10 days before Prof Hawking died.
In the 1980s, the Cambridge scientist, along with US physicist James Hartle developed a new idea about the beginning of the Universe.
This 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.
Instead, the Hartle-Hawking idea used a different theory called quantum mechanics to explain how the Universe arose from nothingness.
The idea tied up one loose end but created another - an infinite number some might say.
As physicists analysed the idea it emerged that it carried with it the implication that the Big Bang would create not just one universe - but an endless supply.
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