It is hard to shake the intuition that there's a real and objective physical world out there. If I see an umbrella on top of a shelf, I assume you do too. And if I don't look at the umbrella, I expect it to remain there as long as nobody steals it. But the theory of quantum mechanics, which governs the micro-world of atoms and particles, threatens this commonsense view.

Featuring Chiara Marletto, Research Fellow of Physics, and Christopher Timpson, Professor of Philosophy of Physics, both at the University of Oxford, and Marcus Huber, Professor of Physics, TU Wien.

This episode is 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: 

• 'QBism': quantum mechanics is not an objective description of reality – it reveals a world of genuine free will

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Interest in the multiverse theory, suggesting that our universe is just one of many, has spiked since the movie Everything Everywhere All At Once was released. The film follows Evelyn Wang on her journey to connect with versions of herself in parallel universes to stop the destruction of the multiverse. The multiverse idea has long been an inspiration for science fiction writers. But does it have any basis in science? And if so, is it a concept we could ever test experimentally? 

Featuring Andrew Pontzen, professor of Cosmology at University College London, Katie Mack, Hawking chair in cosmology and science communication at the Perimeter Institute for Theoretical Physics, and Sabine Hossenfelder, research fellow of physics at the Frankfurt Institute for Advanced Studies. 

This episode is 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: how we're tackling the challenges facing the theory
• Curious Kids: how likely is it that there are parallel universes and other Earths?
• The multiverse: our universe is suspiciously unlikely to exist – unless it is one of many

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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

Hosted on Acast. See acast.com/privacy for more information.

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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