Cosmologist Laura Mersini-Houghton: ‘Our Universe is a Little Grain of Dust in a Beautiful World’ | astronomy

TheOra Mersini Houghton was born in Albania and raised under an authoritarian communist regime that, until its collapse in 1991, isolated the country from the rest of the world. Influenced by her father, Nexat Mersini, a mathematician, she developed a keen interest in physics and, in 1994, won a Fulbright scholarship to study in the United States. her first book, Before the Big Bang, describes her quest to shed light on the origins of our universe and prove that we are one of many in a much broader multiverse. Mersini-Houghton is now Professor of Theoretical Physics and Cosmology at the University of North Carolina at Chapel Hill, although she is currently in Cambridge, England, where she spends time each summer doing research.

How has life in a closed society shaped your thinking?
I think it encouraged a greater love of freedom and knowledge – the more you are prevented from discovering somewhere beyond, the more curious it makes you. Also, due to the very bleak reality of Albania, we had few sources of distraction, so people were more thirsty for knowledge than I see now in the West. Also, one mindset is to want to find the answer and not really like the prevailing philosophy in the field at the time.

What drew you to theoretical physics and cosmology in particular?
Cosmology contains all the most amazing questions I’ve been dreaming about since I was a kid: Where did the universe come from and what was it before it existed? As for working in theoretical rather than experimental physics, I’m really not a practical person – if I put it in a lab, I would probably accidentally set it on fire.

You write that the beginning of this century was a good time to enter the field of cosmology. why?
Because knowledge has advanced a lot, and for the first time we can actually ask those big questions that fascinated me when I was a kid. There were two main findings that really prompted this curiosity. In 1998, a group of supernova astronomers discovered that there is dark energy in the universe, which is in fact the predominant component – exactly the same type of energy as what was present at the time of the big bang.

The other component was theoretical findings in string theory. Now, string theory is designed to fulfill that Einstein dream of a single universe that the theory of everything explains. But around 2004, string theory ended up with a full spectacle of the many potential energies that could start universes like ours.

In the book, she describes an eureka moment she had in a North Carolina coffee shop. what did you realize?
I was so intrigued [Nobel prize-winning physicist] Roger Penrose estimated that there was almost no chance of our universe coming into being. I kept analyzing his argument, which is based on the second law of thermodynamics, trying to see if he had done something wrong. Then I realized that the problem was not the actual computation, it was more about how we think, and that we needed a paradigm shift from one universe to many universes. And here I began to borrow the scene of string theory to do the math. At the coffee shop, I thought, OK, I’ve convinced myself I need a bunch of many potential infant universes to choose from, but how do I derive the answer, which one is ours? And then I realized, of course, quantum mechanics in the string theory scene. In other words, think of the universe as a wave, and then the quantum equations will tell me what happens to that wave.

A lot of hard computational work followed. I stumbled after the first round of calculations. What have you overlooked?
I missed the most important element: the solution to this equation is not just one branch or one universe, it is an entire family. So these branches that might grow and become universes are all quantum entangled with each other. In order for each of them to create their own identity while growing up in Classical universes, they have to separate themselves from each other. This is known in physics as decoherence, or removing any trace of quantum entanglement that has no equivalent in classical physics. I did not take this into account.

Once the account is ready, how do you start testing it?
When the separation process [of universes] Happening, this is the point when the cosmic microwave background (CMB) is created. So all the fluctuations of inflation will leave scars or scratches as a result of this tangle, and it will be printed on our website. [universe’s] CMB. This was something we could count. So I calculated the strength of the tangles between the different branches and how quickly this tangle was washed away. This allowed me to see how much curvature or scarring this tangle would leave on our skies as it did during inflation, and then fast forward to the present day, to make predictions about what those very large-scale deflections would look like. One of the main predictions of cosmic inflation is that everything is scattered uniformly across the sky. But the scar now resulting from the entanglement with other universes modifies or weakens this unification, violating it on very mild scales. We expected it, and the Planck satellite saw them [in 2013].

That should be a great moment of validation.
yes. And I think that’s when people started paying more attention to this work. Until then, the belief was that, to see beyond the horizon of our universe, we must break the speed of light, which we cannot do. So, if we can’t test the multiverse, why bother looking for it? But Rich Holman, Tomo Takahashi and I made it clear that you don’t need to get out of this universe, you can actually find all traces within your sky. That’s when the whole field suddenly shifted and everyone was doing research on the multiverse.

Are you saying it’s mainstream now?
Oh, sure. All great minds work on it. Roger Penrose has his own theory of the multiverse. And Stephen Hawking, in the last few years of his life, began working on the multiverse. Wherever you look, suddenly everyone has a copy of the multiverse.

The multiverse is a mind-boggling concept. Do you think a lot about the other universes out there?
yes I do. In a way, it is the natural extension of the Copernican principle, because once we thought the Earth was the center of the universe, then the solar system and our galaxy, and now we find that even our universe is just one small grain of dust in a much more complex and beautiful world. This to me makes more sense.

Does it seem likely that other universes could harbor life?
definitely. With Fred Adams, an astrophysicist at [the University of Michigan in] Ann Arbor, I decided to see if structures would form in universes with conditions very different from ours. We discovered that you can change Newton’s constant by 10,000 – six orders of magnitude – and you can do the same with Planck’s constant, and still get life in other universes. In fact, our universe appears to be habitable only at the border. We were sitting on the edge between habitable and uninhabitable.

Did you enjoy writing? the book? Was it okay to go back to your work step by step?
Yes and no. At first, I was excited to share this passion and excitement in research with the general public. But then there was an impulse to share more and more personal stories. And now my colleagues, who knew absolutely nothing about my life, could suddenly find out everything. This is a strange feeling.

Do you spend a lot of time in Albania these days?
I haven’t been back in some time, because my family moved to Toronto and my dad passed away and there’s no one left there. I will let you in on a secret. Stephen Hawking and I were organizing a conference in Albania. He was very excited about it, everything was in place, but he passed away a month before it was due. I called him every week to check on his health, and after we decided to cancel [because Hawking was unwell], I remember his chief nurse saying, “Whatever you do, don’t tell him you’ve canceled the conference in Albania, because he’s so looking forward to it.” So I never told him.

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