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Paradox: A Q&A with Jim al-Khalili

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One of my favorite science books in recent years was physicist Jim al-Khalili’s The House of Wisdom, delving into the Islamic Golden Age, when the arts, sciences and mathematics flourished in the Muslim world as much of Western Europe fell into the Dark Ages. So I was delighted to hear that he has a new book: Paradox: The Nine Greatest Enigmas in Physics. And he was kind enough to answer a few questions for the cocktail party.

You can read an excerpt from Paradox here. But first, here’s what al-Khalili had to say about it.

1. What prompted you to write Paradox? It seems like a bit of a departure from your last book, House of Wisdom, which delved into the Islamic Golden Age for math and science.

Actually, The House of Wisdom was the ‘departure’ for me. I am not an historian of science and that book took a lot of time and effort to research. With Paradox I have returned to what I love and, I hope, do best: popularize physics. It occurred to me that so many of the deepest questions in physics have been framed as paradoxes – puzzles that highlight some of the stranger implications of theories such as Einstein’s relativity of quantum mechanics. I think it’s such a fun way of getting the science across.

2. I’m curious to hear more about the difference between perceived paradoxes, where the answer is tricky but known, and genuine paradoxes. What is the crucial distinction for physics paradoxes?

Well, since we believe Nature not to be paradoxical, the way I see is that if there seems to be a paradox then this indicates where there is a gap in our understanding. So all the physics paradoxes in the book are in fact just perceived paradoxes and the mysteries dissolve away (I hope, if I’ve done my job properly) once the science is explained.

3. Your book mentions the time travel paradox i.e., the classic film trope that wonders what would happen if you went back in time and killed your own grandfather. So, (a) how does physics/philosophy resolve this paradox? and (b) what’s your favorite time travel movie?

My favorite time travel film is The Terminator without a shadow of a doubt.

As for how we might resolve the very real paradox of time travel, there are two ways out. One is straightforward but not satisfying, the other is speculative but sure fire: either we say that we can go back in time but cannot change the past in a way that causes it to turn out differently to the way it has. So I can go back to meet my grandfather but I cannot kill him; the fact that I am there to even try is proof that he must survive any attempt on his life since I do get born.

The other is to subscribe to the idea of parallel universes (realities). Each one with its own time line. By going back to the past I unavoidable slide into a parallel universe. This is not such a crazy theory and there are several hints in modern physics that our universe is not the only one.

4. The Schroedinger’s cat paradox is one of the most famous in physics — and possibly the most misunderstood by non-scientists. Why? How should non-scientists be thinking about this paradox for a better understanding of the nuances?

Ooh, well, I could say: read the chapter in the book, but here is the short answer: since we know from quantum mechanics, and countless experiments that an atom, say, can do two things at once, then if each of those eventualities can by tied up with the fate of the cat in the box then surely, Schrodinger said, the cat must also exist in two states at once (dead and alive at same time). But we never open the box to see both outcomes at once.

Now this is a thought experiment but it’s a real issue if we push quantum mechanics to it’s logical conclusions. The mystery is resolved if we restrict quantum behavior to the subatomic world. We can now show that in fact quantum weirdness like this ‘leaks away’ before it can ‘infect’ the cat.

5. What can readers gain by acquiring a better understanding of the logic, etc. that underlies paradoxes? I.e., why is it important to delve into paradoxes, at least occasionally?

For scientists, they are a powerful tool to highlight where there may be gaps in our understanding – if we force a paradox then there is something missing.

For the general reader, paradoxes are just fun – they’re puzzles or brain teasers. But rather than the solution to a trivial riddle, the solution to these paradoxes involves a deeper understanding of the laws of nature, so it’s a great way to learn about some of these quite counter-intuitive and mysterious ideas in modern physics.

6. Now that you’ve tackled the Islamic golden age and physics paradoxes, what might your next book be about?

Why, thank you for asking. I am currently writing my most ambitious book yet: the very first popular account of a new field of science: quantum biology. This is where quantum physics and molecular biology come together. Evidence has been mounting over the past decade to suggest that a vast array of biological processes, from photosynthesis to the way we smell, can only be explained properly if the molecules of life are also governed by these weird quantum rules.

The new field of quantum biology has now come of age and as a nuclear physicist I think I have some tricks up my sleeve that can help. This is an area I am currently interested in in my research: I am working on the idea of whether quantum tunneling of protons in the hydrogen bonds that link DNA strands together can be a mechanism for genetic mutations. The book will be published in the United States by Random House, hopefully in early 2014.


Jennifer Ouellette About the Author: Jennifer Ouellette is a science writer who loves to indulge her inner geek by finding quirky connections between physics, popular culture, and the world at large. Follow on Twitter @JenLucPiquant.

The views expressed are those of the author and are not necessarily those of Scientific American.

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