Finding gravitational waves amidst all the background noise in space required an extraordinarily sensitive detector.
Monica Guica uses a pen and paper in her research. Following successes in International Physics Olympiads, Guica won a scholarship to study at university in the United States. Some years later, having completed her doctorate at Harvard University, Guica took up postdoctoral positions in France and the U. The grant she has been awarded as a Wallenberg Academy Fellow has given her the opportunity to establish her own research team here. She divides her time between Nordita and Uppsala University.
New ideas may begin in a discussion during coffee-break, or come from an article I read by a fellow researcher.
Leonard Susskind on Richard Feynman, the Holographic Principle, and Unanswered Questions in Physics
Black holes are formed when huge massive stars die and collapse in on themselves. Here, the gravitational pull is so strong that nothing can escape the black hole, not even light. Although we now know that black holes exist, pieces of the theoretical puzzle are missing. The general theory of relativity describes gravity, and how it affects time and space, but it does not cover everything. The problem that many physicists are keen to solve is that these two well tried and tested theories clash with each other. How did you come up with the idea of cosmic inflation?
In this talk, Bob Dicke told us that if you thought about the universe at one second after the beginning, the expansion rate really had to be just right to 15 decimal places, or else the universe would either fly apart too fast for any structure to form or re-collapse too fast for any structure to form. It would also draw the universe to exactly the right expansion rate that the Big Bang required [to create a universe like ours].
How so? During the spring of , after having come up with this idea of inflation, I decided that the best way to publicize it would be to give a lot of talks about it.
Then they got back to me in one day and made me an offer. It was great. When and where do you do your best work? I firmly believe that I do my best thinking in the middle of the night. I very much like to be able to have reasonably long periods of time, a few hours, when I can concentrate on something and not be interrupted, and that only happens at night. What often happens is I fall asleep at like and wake up at 1 or 2 and start working and then fall asleep again at 5. I bet it would have been a lot of fun to work with Einstein. What I really respect about Einstein is his desire to throw aside all conventional modes and just concentrate on what seems to be the closest we can get to an accurate theory of nature.
What are you currently working on? If this works out, these primordial black holes could perhaps be the seeds for the super massive black holes in the centers of galaxies, which are very hard to explain. It would be incredibly exciting if that turns out to be the case. What else are you mulling over?
A bigger question, which has been in the back of my mind for a decade, is the problem of understanding probabilities in eternally inflating universes. In an eternally inflating universe, these pocket universes [like the one we live in] go on being formed literally forever. The s and s could be considered a heyday of particle physics, when many subatomic particles—and not just elementary ones, it turns out—were being discovered. Could you talk a little bit about the events leading up to your discovery of the quark?
That was very dramatic for me. I had been working for years on the properties of particles that participated in the strong interaction. This is the interaction responsible for holding the nucleus of the atom together. The family of strongly interacting particles includes the neutrons and protons; those are the most familiar ones.
But now tens, dozens, hundreds of other particles were being discovered in experiments in which protons collided with each other in particle accelerators. There were lots and lots of energy states in which we saw relatives—cousins—of the neutrons and protons. They are produced in a particle collision in an accelerator, and they decay after a short time.
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After a tiny fraction of a second, they fall apart into other things. One particle that I predicted, the omega-minus , can decay into a neutral pion and xi-minus, and then the pion decays into photons, and the xi-minus decays into a negative pion and a lambda. And then the lambda decays into a negative pion and a proton. The interior of the sun has a very high temperature, but even that very high temperature is not enough to make all of these things.
Detecting the ‘Bang’ from the Big Bang
Do all these exotic particles exist anywhere outside of physics experiments? They existed right after the Big Bang, when temperatures were incredibly high. And they occur in cosmic-ray events. Looking at the table of known particles and the experimental data, it was clear that the neutron and proton could be made up of three particles with fractional charges, which I called quarks. The neutron and proton were no longer to be considered elementary. It was not a difficult thing to deduce. What was difficult was believing it, because nobody had ever heard of making the neutron and proton composite.
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Nobody had ever heard of these fractional charges. Nobody had ever heard of particles being confined permanently inside observable things and not directly attainable. As time goes on, physicists seem to find more and more particles. Could there be an infinite number of them? All of us theorists believe in simplicity. Simplicity has always been a reliable guide to theory in fundamental physics.
The Man Who Found Quarks and Made Sense of the Universe
But the simplicity may not lie in the number of named particles. It may be that the theory, expressed simply, gives rise to huge numbers of particle types.
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The particles might go on forever, but you detect only the ones that are light enough to play a role in your experiments. Now researchers are pinning a lot of hope on finding yet another set of predicted particles in experiments at the Large Hadron Collider. Do you think this will bring some clarity? Well, there is another possibility, that they find some phenomenon that is utterly unexpected.
He had had a very substantial library, a huge library. And when the bad times struck—the Depression—he had to get rid of them when we moved to a tiny apartment. He had to have the furniture taken away.
He paid somebody five dollars to take away his library. But he had a few books left, 50 books or something like that. One of them was a book that gave etymologies of English words borrowed from Greek and Latin. So I learned all these Greek and Latin roots and how they went to make up English words. It was exciting. That started me on etymology, and I have loved etymology ever since.
I was always OK in math. Actually I loved math, loved studying it, loved using it. I loved history. I was particularly in love with archaeology and linguistics. And I could discuss anything with my brother—archaeology, etymology, anything at all. He never did anything with it, but he was very, very intelligent and very knowledgeable about all sorts of things. He was passionate about birds and other living things.
Not so much the scientific principles of ornithology, but just seeing the birds and identifying them and knowing where they were, and what kind of nest they had, and what songs they sang. Going with him on a bird trip was the best thing—the best thing—I did in those years.
My brother taught me to read from a cracker box when I was 3. When you were going into college, you were interested in studying archaeology, natural history, or linguistics, but your father wanted you to make money as an engineer. If I designed something it would fall down. Then how did you settle on physics?
General relativity, quantum mechanics, you will love it. I never took his advice on anything else. He told me how beautiful physics would be if I stuck with it, and that notion of beauty impressed me. My father studied those things. He was a great admirer of Einstein. He would lock himself in his room and study general relativity.
He never really understood it. My opinion is that you have to despise something like that to get good at it.