Do you have free will? Is our Universe the only one, or do we live in one of many? And what does Einstein’s theory of relativity really say about the nature of reality?

These are some of the big questions that theoretical physicist Sean Carroll tackles in this Big Think video.

In 2022, Carroll published The Biggest Ideas in the Universe: Space, Time, and Motion, a book that achieves that rare feat of detailing the inner workings of scientific concepts in a way that’s accessible but not overly simplistic.

THE MULTIVERSE

0:00 Sean Carroll, Johns Hopkins physicist

0:18 What is the Multiverse and what does it mean to us?

2:38 What is the physicist’s version of the Multiverse?

6:43 Is every possible world real?

9:22 Why should we trust the many worlds of quantum mechanics?

12:24 How many worlds are there?

14:47 How does personal identity in the Multiverse work?

16:43 Do our decisions create different universes?

20:25 Why are we drawn to the Multiverse and how does technology propel it?

TIME

26:33 What is time? (And entropy?)

35:52 What is the past hypothesis? (The laws of thermodynamics)

ENTROPY

41:32 Why is entropy essential to living?

44:33 Why are there complex structures in the Universe?

46:11 Do complex structures require design?

47:55 What is the effect of increasing entropy?

50:03 What is the difference between entropy and complexity?

52:52 What is emergence?

PHYSICS: GALILEO'S LEGACY

55:08 Why is physics such a difficult field to study?

ORIGINS OF LIFE

58:14 Is life a struggle against entropy?

1:00:36 What are the origins of life here on Earth?

1:04:52 How many things had to “go right” for us to exist?

1:07:33 If this isn’t God’s design we’re seeing, what is it?

FREE WILL

1:11:22 What is Laplace's demon and do we have human agency?

1:16:30 What are the different viewpoints on free will?

1:23:44 How do our feelings fit into the molecular world?

1:26:24 Are there objections to the compatibilist worldview?

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About Sean Carroll:

Dr. Sean Carroll is Homewood Professor of Natural Philosophy — in effect, a joint appointment between physics and philosophy — at Johns Hopkins University in Baltimore, and fractal faculty at the Santa Fe Institute. Most of his career has been spent doing research on cosmology, field theory, and gravitation, looking at topics such as dark matter and dark energy, modified gravity, topological defects, extra dimensions, and violations of fundamental symmetries. These days, his focus has shifted to more foundational questions, both in quantum mechanics (origin of probability, emergence of space and time) and statistical mechanics (entropy and the arrow of time, emergence and causation, dynamics of complexity), bringing a more philosophical dimension to his work.

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