Faculty team serves up a slice of the universe


Caroline Moseley

Princeton NJ -- If Astrophysics 203, "The Universe," had only one message, it would be: The universe is big. Really big. And if students used only one adjective to describe the course, it would be: Cool. Really cool.

 

In a recent session of Astrophysics 203, "The Universe," professors used pizza to demonstrate some geometrical properties of curved-space time that might allow space travel -- then treated the class to a pizza party. From left are: Anne Griffin '01; faculty members Michael Strauss, Richard Gott and Neil deGrasse Tyson; Sergio Frisoli '03; and Charles Insler '03.


 

"Quasars, supernovae, black holes, the Big Bang -- the material is so darn cool," says Alexandra Blasgen '01, a student in the course. "It's fascinating stuff. You learn something great at every lecture."

"The Universe" ("Now there's an audacious title," says Neil deGrasse Tyson, one of the instructors) satisfies the quantitative reasoning general education requirement and is intended for humanities and social science majors, though it attracts students from across the disciplines.

"The course doesn't aim to make everybody a scientist -- what a boring world that would be," says Tyson. "We do want them to understand how the universe works.

"After their problem sets are long discarded, and exam questions forgotten," he says, "we hope what remains is a humble appreciation for our small and fragile place in the cosmos."

Stars, galaxies, the universe

The course is designed in three parts: stars, galaxies and the universe. Subjects include the birth, life and death of stars; the search for extrasolar planets and for extraterrestrial life, intelligent or otherwise; galaxies from dwarfs to giants, from starbursts to quasars; dark matter and the large-scale structure of the universe; Einstein's special and general theories of relativity; black holes; time travel; and Big Bang cosmology.

The stars segment is taught by Tyson, visiting research scientist and director of the Hayden Planetarium in New York City; galaxies are the purview of Michael Strauss, associate professor of astrophysical sciences; and the section on the universe is taught by Richard Gott, professor of astrophysical sciences.

Tyson, whose own research is on the structure of the Milky Way galaxy and the formation of stars in other galaxies, leads off. It's his job to make sure the fledgling astrophysicists "get cozy with very large numbers." How many is a million? A billion? A trillion? "You live 2 billion seconds in your life," he says. "At about the age of 31-1/2, you live your billionth second. I celebrated with candlelight and wine!"

Light travels at 186,000 miles per second. "A light year is the distance light travels in one year," says Tyson, emphasizing that a light year "is a measure of distance, not time -- about 6 trillion miles." Conor Neu '02 comments, "Every number is more amazing than the one before."

Tyson's personality is big enough to complement the astronomical numbers. Jovial, nattily attired in a vest emblazoned with celestial bodies, his romp through the billions and trillions is only just over-the-top. His frequent jests are apposite, and he often uses popular cultural references -- such as clips from sci fi films -- that resonate with students. He is particularly disparaging about popular scientific misconceptions: "I have a book called 'How Not To Get Abducted By Aliens,'" he says. "If you do what it says, it works."

In the classroom, in the planetarium and in print, Tyson has spent his professional life demystifying the cosmos for nonscientists -- "bringing the universe down to earth," he says. Tyson believes astrophysics is a particularly accessible science because, "You only have to look up to be inspired. The universe is right there, staring back at you."

Tyson's biggest classroom coup was bringing TV's Bill Nye, the Science Guy, into the lecture hall for a staged confrontation that delighted students. But he also brings, in spirit, Ptolemy, Copernicus, Galileo, Kepler, Tycho Brahe and Isaac Newton -- the last being Tyson's nominee for "World's Smartest Person."

Then, enter Michael Strauss, a kinder, gentler and even more quantitative astrophysicist. His own research on the most distant objects in the universe is about as up-to-date as students are likely to hear anywhere but at a press conference. He doesn't have any gimmicks, and doesn't need any. His enthusiasm for his material shines like a solar flare. "Astrophysics is so interesting," he says. "If we worked at it, we could make it boring, but it would be awfully difficult."

Strauss introduces students to their own galaxy, the Milky Way. He points out that the Copernican revolution was sociological as well as scientific, leading to "the principle of mediocrity: There is nothing special about us. We live on a typical planet revolving 'round a typical star in a typical galaxy in a typical group of galaxies." This very ordinariness has been used as an argument for intelligent life on other planets, he points out: If us, why not them?

His graphics of choice are incandescent galaxies, distant quasars and the occasional Calvin and Hobbes cartoon -- one favorite describing the Big Bang as "the horrendous space kablooie."

Strauss's word to the class is that the universe is expanding and will expand forever. It never had, nor ever will have, a center or edges. Its size was, and will continue to be, infinite. "Infinity is a funny thing," he observes.

In astronomy, says Strauss, "We deal with many inexact numbers. One of the difficulties for those used to doing math only in the context of math, is the nature of approximations. In mathematics there is a well-defined answer: two-plus-three-equals-five, end of story. In astronomy, however, we think about it differently, not only because the numbers are so big, but because often accuracy is not that important. You may want simply to get an order of magnitude."

In class, for example, Strauss worked out the age of the universe. "I could have plugged numbers into a calculator, and done it to several decimal places," he says. "But no one really cares if the universe is 13.2 billion or 13.5 billion years old."

In addition, he points out, the value of the Hubble constant -- a measure of the rate of expansion of the universe, which ends up determining the age of the universe -- is uncertain. "There's always uncertainty in astronomical calculations," he says. "Your conclusions are stronger or weaker depending on the degree of uncertainty."

Not a problem, says Strauss. "It's easy to ask good questions in astrophysics. Answering them is more difficult. That's what's fun."

In the third section of the course, Strauss promises, "Professor Gott will take you 'beyond the beyond.'" It is up to Gott -- whose research ranges over general relativity and cosmology -- to introduce the class to Einstein's theories of special and general relativity, and the many conundrums that tantalize those on the frontiers of astrophysics.

Gott, a 1998 recipient of the President's Award for Distinguished Teaching, has a classroom persona that can best be described as idiosyncratic. A native of Kentucky, he has a gentle drawl that transmutes "Mr. Einstein" into "Mr. Ahnstahn," making the interpreter of the universe somehow more accessible.

Gott trundles in to lectures pulling a black suitcase, filled with fairly low-tech equipment -- a bright yellow plastic rocket ship, nerf balls in assorted sizes, lengths of strings, plastic doughnuts, a rubber football, an impressive fleet of Dinky cars. With this paraphernalia, he explains some of the features of the Einsteinian universe.

Euclidean geometry doesn't work in curved space-time, he points out. To demonstrate the effect of curvature, he takes two tiny trucks, starting them at separate points on the equator of a desktop globe; the cars start off in parallel, each taking the most direct, straightest route north. Parallel lines shouldn't meet, but the cars come nose to nose at the North Pole.

Gott covers the blackboard with calculations, deriving "the world's greatest equation": E=mc2, demonstrating, as did Einstein, the equivalence of matter and energy. The class, left gasping at the rapidity with which Gott charges through the numbers, breaks into applause.

The new cosmology having been established, or at least limned, Gott next shows slides of "Newton's place": Trinity College, Cambridge. He shows Newton's windows, Newton's cane, a statue of Newton, and a photo of his own somewhat younger self with the statue. He shows Newton's signature alongside Einstein's signature, and points out that the signatures "are completely different." He shows Newton's death mask, observing simply, "Ugh!" Yet, somehow the class ends up knowing a little more about the young Newton -- a boy who managed "the most accurate measurement of the speed of sound for his time" by clapping his hands repeatedly in the corridor and listening to the echo of each clap.

Time travel

Moving into general relativity, while giving Newton his due, Gott makes it clear that, in his opinion, Einstein trumps Newton on gravity and competes with Newton for the "World's Smartest" award. Gott, who created one of the nation's first courses in general relativity for undergraduates, explains, "Curved space-time is responsible for gravity. One of the remarkable things about general relativity is that it has produced so many interesting exact solutions to the field equations."

Gott offers students a wealth of cosmological speculation, exploring, for example, the notion of time travel "not necessarily for practical reasons, but to understand the limits of our theories."

"You can see how much each of the professors loves astro," says Brooke Meserole '04. "Their enthusiasm is so catching, it's almost impossible not to love it yourself. But at the same time, they challenge you to think things through on your own, and not to be content with something simply because they say so."
 


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May 7, 2001
Vol. 90, No. 27
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Contents

Senior thesis
Independent work caps Princeton experience
Delving into bioethics
Researching the court
Combining two interests
Analyzing theses topics

Minicourses provide 'continuing education'
Dale touched students lives
Faculty team serves up a slice of the universe

Communiversity 2001
PWB readers surveyed soon

People
Spotlight
Briefs

Sections
By the numbers: Endowed professorships
Nassau Notes
Calendar of events


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Editor: Ruth Stevens
Calendar editor: Carolyn Geller
Contributing writers: Karin Dienst, Jennifer Greenstein, Marilyn Marks, Caroline Moseley, Steven Schultz, Lauren Sun
Photographer: Denise Applewhite
Design: Mahlon Lovett, Laurel Masten Cantor
Web edition: Mahlon Lovett