Imagine a universe with extremely strong gravity. Stars would be able to form from very little material. They would be smaller than in our universe and live for a much shorter amount of time. But could life evolve there? It after all took human life billions of years to evolve on Earth under the pleasantly warm rays from the Sun. 

Now imagine a universe with extremely weak gravity. Its matter would struggle to clump together to form stars, planets and – ultimately – living beings. It seems we are pretty lucky to have gravity that is just right for life in our universe.

Featuring Fred Adams, professor of physics, University of Michigan, and Paul Davies, professor of physics, Arizona State University.

This episode was presented by Miriam Frankel and produced by Hannah Fisher. Executive producers are Jo Adetunji and Gemma Ware. Social media and platform production by Alice Mason, sound design by Eloise Stevens and music by Neeta Sarl. A transcript is available here. Sign up here for a free daily newsletter from The Conversation.

Further reading: 

• The multiverse is suspiciously unlikely to exist unless it is one of many

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Without a sense of time, leading us from cradle to grave, our lives would make little sense. But on the most fundamental level, physicists aren't sure whether the sort of time we experience exists at all. We talk to three experts and find out if time could potentially be moving backwards as well as forwards.

Featuring Sean Carroll, Homewood professor of natural philosophy at Johns Hopkins University, Emily Adlam, postdoctoral associate of the philosophy of physics at Western University and Natalia Ares, Royal Society university research fellow at the University of Oxford.

This episode was presented by Miriam Frankel and produced by Hannah Fisher. Executive producers are Jo Adetunji and Gemma Ware. Social media and platform production by Alice Mason, sound design by Eloise Stevens and music by Neeta Sarl. A transcript is available here. Sign up here for a free daily newsletter from The Conversation.

Further reading: 

• Quantum mechanics: how the future might influence the past
• Four misconceptions about quantum physics

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"There is nothing new to discover in physics", declared the British physicist Lord Kelvin in 1900. That is no longer true. Today it is becoming increasingly clear that there are problems that physics, as we know it, doesn't seem to be able to solve. Perhaps we just need more data, perhaps we need a new fundamental theory of reality. 

In this six-part series, host Miriam Frankel from The Conversation will take you on a mind-blowing journey from the smallest to the largest conundrums, exploring curled-up dimensions, consciousness and parallel universes along the way. We will discover the greatest mysteries facing physicists today – and discuss the radical proposals for solving them. 

The first episode will be available on March 8.  

Great Mysteries of Physics is produced by Hannah Fisher with sound design by Eloise Stevens. You can sign up to The Conversation’s free daily email here.

Great Mysteries of Physics is a podcast series supported by FQXi.

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