The world-famous cosmologist Stephen Hawking published an important paper two weeks before he died on March 14, aged 76. He published his final theory called "A Smooth Exit from Eternal Inflation". He explained two ideas. The first was how humans might be able to find multiverses. These are other universes that were made at the same time as our universe, after the Big Bang. The second theory is about how our universe will end, when the stars run out of energy. Scientists say his paper could be his most important ever, and that he could have won a Nobel Prize for it.
Hawking explained his older theory called inflation. This is when our universe was made from a tiny point in space into the billions of stars we have today. Hawking suggested there were many big bangs and each of them made its own universe. He called this collection of universes a multiverse. Hawking believed scientists could find the multiverse by using sensors on space ships. A professor of cosmology said: "These ideas offer the breathtaking prospect of finding evidence...of other universes." Hawking is also famous for his best-selling book "A Brief History of Time".