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Where do planets come from? How are galaxies formed? What is the origin of the universe? Pitt is part of an international consortium gathering reams of data that may help researchers, such as Pitt newcomer Ravi Sheth, better answer these fundamental questions.

Shooting Star


Shanti Wendler


 Ravi Sheth
In the beginning, the universe was wrapped in a hot, smooth, tight little package—less than a billionth of a billionth the size of a proton, an ambitious speck exploding into existence with the biggest bang.

Of course, this wasn’t the beginning. Where the speck came from and what it was like at its moment of creation is still a mystery, shrouded in the singularity that occurs when you try to squeeze the universe into nothingness, where temperature and density run away to infinity and every natural law jumps out the window.

It has been around 13.7 billion years since the Big Bang—the explosion that most scientists believe gave birth to our cold, chunky universe. Today, physicists and astronomers work incessantly to document its mysteries. They look with wonder through telescopes or analyze cryptic blends of mathematical symbols and Greek letters, driven by a curiosity to uncover every detail and understand its meaning and consequence.

Ravi Sheth, assistant professor in the Arts and Sciences’ Department of Physics and Astronomy and an astrophysicist at the University of Pittsburgh, tries to trace the universe’s transformation—from a smooth speck to galaxy after galaxy. He works the old-fashioned way, with a pencil and paper, drawing model after model, trying to explain how galaxies form and how they die, hoping to reconstruct the past and peek into the future.

Twenty years ago, it would have been difficult to prove or disprove his models. Between cloudy skies and waiting for a turn on the best telescopes, scientists could have spent their entire lives gathering information on the same object. No more. Astronomy has been transformed by a massive influx of data. Advances in computer science have made it possible to store and process this information, allowing teams of scientists to build huge databases. The biggest of these is the Sloan Digital Sky Survey (SDSS), a project whose participants include the University of Pittsburgh and 12 other institutions—among them Princeton University, Johns Hopkins University, the University of Chicago, and Fermi National Accelerator Laboratory (Fermilab).

The SDSS images are collected at the Apache Point Observatory, site of the SDSS telescopes in Sunspot, N.M. For scientists around the world, SDSS is something like a public telescope in perfect weather, allowing them to study data on millions of objects. SDSS is in the process of mapping a quarter of the night sky, measuring the positions and brightness of more than 100 million celestial objects. It will also measure distances to a million of the closest galaxies, allowing scientists to construct a three-dimensional image of the universe.

At various release dates, the entire scientific community will have access to the SDSS data. For participating institutions, such as Pitt, the latest SDSS findings are immediately available. This undertaking gives scientists, such as Sheth, an accurate picture for testing models of how galaxies form and evolve.

Sheth’s beginning came in Wisconsin 34 years ago, born to an Indian father and American mother. They named him Patrick, which didn’t please his Indian grandparents. Based on his month of birth, they insisted certain auspicious sounds should begin his name. So, “unlucky” Patrick became Ravi prior to the family moving to Bombay (now Mumbai).

He became enthralled with science while still in high school. At the time, he was taking physics and reading The Dancing Wu Li Masters, which explains—with a twist of Eastern mysticism—the advances of modern physics, such as quantum theory and relativity. Sheth admits most scientists would consider such books “hokey,” though he doesn’t. After all, he studied philosophy as well as physics as an undergraduate.

He always believed he would attend college in the United States, but he didn’t want to give up playing cricket, his favorite sport. He chose to attend Haverford College, just outside Philadelphia, because of the sport’s popularity there. While at Haverford, an astronomer named R. Bruce Partridge nurtured Sheth’s academic interests while recognizing his athletic prowess. When it came time for Sheth to choose a graduate program, Partridge helped him qualify as a Marshall Scholar to study in England, where he could continue playing cricket. Thanks to Partridge’s guidance, Sheth decided to study astrophysics at the University of Cambridge, earning his Ph.D. there. Next, he did postdoctoral research at the University of California-Berkeley, Hebrew University, Fermilab, and the Max-Planck Institute for Astrophysics. Last year, he finally settled into his first faculty position in the University of Pittsburgh’s Department of Physics and Astronomy.

As for the department, it has its roots in the University’s acquisition of the Allegheny Observatory on Pittsburgh’s North Side in 1867, though it has come a long way since then. Its link to the SDSS project gives Pitt’s astrophysics program additional national visibility, says David Jasnow, professor and chair of the department. It also helps attract students and faculty, including Sheth.

Jasnow calls Sheth a “very sophisticated statistician” at a time when researchers of every stripe must increasingly make sense of mountains of data. Take the SDSS project. During the next five years, millions of galaxies will be catalogued for things such as size, texture, and location in the sky. Enough raw data will be gathered to fill 30 university libraries, three times the printed collection of the U.S. Library of Congress.

How, though, will scientists use that data to understand how the universe evolved into what it is today? Enter Sheth.

One of Sheth’s strengths is finessing data to get answers to specific questions, says Andrew J. Connolly, assistant professor, Department of Physics and Astronomy, and member of Pitt’s SDSS team. What’s more, Connolly says the ability to manipulate big stores of data has some interesting uses outside astronomy, including predicting patterns of population growth and the spread of disease. Pitt’s School of Medicine and Department of Computer Science are two areas using this kind of highly refined analysis.

Of course, Sheth teaches, too. While at Fermilab, Sheth gave a lecture where he used his model to explain how galaxies form in “halos,” which are blobs of dark matter. Dark matter doesn’t shine, so it’s invisible to telescopes and can only be detected through its gravitational effects. Ryan Scranton, who has begun his postdoctoral work at Pitt, attended that lecture. He describes Sheth’s model and explanation as lucid and organized—evidence of someone with “tremendous command over what he’s talking about. I learned more about halos from that one talk than in all my years of study.”

Understanding things like dark matter may lead to new laws of physics, Jasnow says. “It’s very exciting.”

In the beginning, or at least a trillionth of a trillionth of a trillionth of a second after the Big Bang, our fiery speck was expanding exponentially. Yet, the smallest particles of light, photons, were ingredients in a hot soup of particles that included atoms—protons, neutrons, and electrons. As the theory goes, the high-energy photons kept running into electrons, preventing the formation of atoms, creating instead an opaque cloud of free electrons. But as the universe kept expanding, it also kept cooling, which sapped some of the photons’ energy and allowed the electrons to combine with protons and neutrons to form atoms. As more and more electrons became bound up in atoms, there were fewer of them left to scatter the photons. So, as the universe cooled, it became transparent and light could escape.

This light had a particular wavelength and temperature. In the Big Bang model, scientists can predict those precise numbers.

Two unsuspecting scientists first observed this ancient light in 1965. Bell Laboratories technicians Arno Penzias and Robert Wilson were installing microwave antennae to relay phone calls from satellites. But they ran into an annoying problem: They couldn’t get rid of a faint hissing, which was constant across the sky. They had stumbled across this primordial light, or Cosmic Microwave Background (CMB) radiation. Ironically, less than 100 miles away at Princeton University, two physicists had just predicted this phenomenon. The physicists, Robert Dicke and P.J.E. Peebles, were building their own antenna to detect the CMB radiation when Penzias and Wilson realized what they had found. It was Penzias and Wilson who shared the Nobel Prize in physics in 1978, based on their discovery.

The annoying hiss turned out to be the strongest evidence for the Big Bang theory.

During Sheth’s postdoctoral research, he studied the connection between CMB radiation and the formation of galaxies.

Here’s how galaxies form. Experiments have shown that not quite the same amount of CMB radiation reaches us on earth from different parts of the sky: To us, we see tiny differences between one area of the sky and another. These small fluctuations, though, are the initial seeds that gravity nurtured into today’s cosmic web of galaxies and vast empty voids.

Gravity is the reason the dense regions are so dense and the sparse ones are so empty. Think of it as cosmic capitalism. Gravity’s pull makes regions that are already dense grow even denser by draining matter out of the less dense regions. The rich are getting richer and the poor are getting poorer. The universe, though, is expanding faster than gravity can hold it all together. This makes it harder for gravity to form and maintain the dense regions. By measuring the abundance of the massive objects we see in space today, we can learn how quickly the universe expanded and what the future may hold.

Particle by particle, Sheth calculates how it all comes together. His models begin with millions of particles, which are attracted to each other according to the laws of gravity. Each particle will be attracted to others that lie within a certain distance. They collect into larger particles, which behave the same way until a large structure develops.

He takes the data from experiments run on supercomputers and incorporates the results into simple models of the underlying physics. Really, all he’s doing is calculating the probabilities of two particles coming together and building a model based on those probabilities. Sheth’s models can be used to determine other patterns based on probabilities, predicting, for instance, population growth and the spread of disease by understanding the behavior of entities containing millions of particles. Once the physics is understood, he can do in hours what would take a supercomputer days or weeks.

In his spare time, Sheth follows cricket, plays squash, reads poetry, and “sometimes” reads Shakespeare.

When Sheth came to Pittsburgh last year, he took on an additional task—teaching undergraduates. For his Introduction to Astronomy class, students meet in a small lecture room with stadium seating. Wearing jeans and fleece, Sheth could pass for a student. He speaks in a low voice, and it seems as though you shouldn’t be able to hear him in the back rows, but you can:

“There’s a really great lecture next door about multiple dimensions,” he says. “So if you want to go, I’ll just turn my back.”

One student does leave, missing quite a dramatic tale from Sheth, told with all the passion of a Shakespearean tragedy. It’s a story about a star in its “death throes,” spewing matter in violent convulsions, its final defeat in a lifelong battle with gravity.

Shanti Wendler is a CAS senior at this University with a dual major in physics and astronomy and nonfiction writing.





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