Physics and Astronomy

专业详情

WHY MAJOR IN PHYSICS & ASTRONOMY

One sure way for a physicist to spark a lively debate at almost any gathering is to quote Sir Ernest Rutherford (1871-1937), nuclear physicist and Nobel Prize Laureate, who once said that “All of science is either physics or stamp collecting.”

On the one hand, this quote is clearly a humorous caricature, particularly in view of the fact that Rutherford won his Nobel Prize in Chemistry, not in Physics! On the other hand, the humor of the quip does depend upon its sly reference to a genuinely distinguishing facet of physics: Physics is the broadest of the sciences, and more than any other seeks to explain the natural world in the most universal manner possible.

The sheer scale of what physicists study is dazzling: astrophysicists study galaxies so far from Earth that their distance (in miles) needs 22 zeros after the last digit, whereas particle physicists study subatomic particles so light that their weight (in ounces) needs 35 zeros before the first digit! Optical physicists use ultrafast laser spectroscopy to directly observe atoms taking part in chemical reactions that last only a million billionth of a second, while just down the hall their colleagues may be studying data on other solar systems in our galaxy, to better understand how the Earth itself was formed 4.2 billion years ago. There is no other science which spans such a vast range of time, space, and matter as physics.

The other distinguishing hallmark of physics is its emphasis on basic knowledge. It has been said that the periodic table of the elements is chemistry, but understanding why the elements form a periodic table in the first place is physics. Physicists look for the hidden symmetries that underlie the natural world, and try to express them in the most universal terms possible. For example, research in the area of nonlinear dynamics has revealed that the chaotic pattern of the heartbeats in a heart-attack patient undergoing severe arrhythmia has exactly the same mathematical properties as a leaky faucet, caught halfway between on and off, which is spluttering erratically. This emphasis on looking past the surface is terrific training for any student, regardless of whether they make physics or astronomy their profession.

MODERN PHYSICS

The frontiers of physics today lie in the areas of (very) complex systems, “soft” matter, nanoscale systems, particle physics, and the physics of quantum optics and quantum entanglement. Our department has faculty working in all of these areas. In nanoscale physics, we are studying such things as how soft organic materials stretch at the atomic level when adhering to hard materials, and how the magnetization dynamics of single-domain magnetic nanoparticles (i.e., particles about a nanometer wide) might contribute to improved magnetic recording technology.

Our particle-physics faculty are working on many problems of fundamental importance; one of the more interesting is the search for so-called “neutrino oscillations”. In brief, many physicists believe that a certain class of subatomic particles known as neutrinos do not maintain a constant identity as they move, but instead rotate between different “flavors” – something like a car which is either a Ford, a Honda, or a Saab, depending on how far down the road it has traveled. (This problem has led physicists in Japan to build a neutrino detector 136 feet tall and 145 feet around, housing 50,000 gallons of water and 11,200 photomultiplier tubes, in a chamber 3,300 feet underground. Extreme devices such as this are needed, because neutrinos are extremely hard to detect.)

At Northwestern, we are working on a project which will culminate in a an intense beam of neutrinos being directed literally through the Earth, from Fermilab here in Chicago to an underground detection chamber some 600 miles away in the old Soudan mine near Duluth, Minnesota! If successful, the project will decisively determine whether neutrinos “oscillate” or not, and if so, how quickly they do it.

MODERN ASTRONOMY

Today is perhaps the most exciting time in history to be an astrophysicist. Technological breakthroughs such as adaptive optics for giant telescopes (which allow them to see clearly through the shimmer of Earth’s atmosphere), orbiting space-based detectors and instrumentation, and ultra-precision measurement techniques, have revolutionized our ability to examine the Universe. In only the last decade, we have detected scores of new planets orbiting near-by stars, and discovered that “normal” matter (as we are made of) constitutes only about 15% of the mass of the Universe. (The other 85% is the mysterious, so-called “Dark Matter”.)

To investigate these phenomena, our astrophysics faculty use x-ray, ultraviolet, optical, infrared, and radio telescopes located almost everywhere: Chile, Arizona, Hawaii, outer space, even the South Pole. (We have had three undergraduate physics majors conduct independent studies at the South Pole, helping Professor Giles Novak with his research on the magnetic field at the center of the Milky Way galaxy.)

Our theoretical astrophysics faculty study exotic objects such as black holes, neutron stars, and white dwarf stars by calculating their properties using certain assumptions, then comparing these to experimental observations. The “official” logo for this research group shows a white dwarf star in orbit about a giant red star, with the dense dwarf pulling in gas from the edge of the red star in a giant whirlpool. This is because such objects do exist, and eventually, as too much mass pours down upon the white dwarf star, the dwarf collapses and then explodes with the energy of a hundred billion Suns. Such events are called supernovas, and they generate the heavy elements that make up ourselves and the Earth.

AFTER NORTHWESTERN

The emphasis in physics and astronomy is always squarely on analytical thinking: the formulation of relevant questions, careful examination of the data, testing of alternative hypotheses, and the rigorous give-and-take of logical debate and discussion. These skills can serve students well in virtually any career, including research and development, medicine, law, journalism, computer science, business, and education. In addition, the strong emphasis upon the use of mathematics and computers allows physics/astronomy majors to move easily into any number of quantitative fields.

Historically, about 60% of the physics majors at Northwestern have chosen to pursue advanced degrees after graduation. Most of these degrees are in physics and astronomy, but include many other disciplines: law, business, medicine, and engineering. On average, physics majors score high on the MCAT and higher than other undergraduate majors on the LSAT (more data is available here). A rapidly growing area of graduate interest is medical physics, including nuclear medicine and diagnostic technology. 

Nationwide, over 90% of the students who pursue PhDs in physics or astronomy are fully supported as either research or teaching assistants throughout their entire graduate careers. They receive full tuition waivers and monthly stipends in return for part-time teaching or research. The very low cost of obtaining a graduate degree in physics or astronomy is one of the major incentives that leads the majority of physics bachelors to enter PhD programs. Afterwards, most PhDs enter careers in basic research in universities, government, or industry.

A recent survey of Northwestern physics/astronomy undergraduate alumni who chose not to attend graduate school revealed a remarkable diversity of career paths. The largest group, about 24% of the total, had become self-employed entrepreneurs, mostly in the areas of computer and engineering consulting. Other employment paths included industrial research and development, business management (often in technological companies), computing, government public-policy research, law, engineering, medicine, the military (with technical/engineering duties), technical sales (such as very expensive, very complex CAT-scan equipment), high-school teaching, accounting, museum or library work, police forensics, nonprofit social work, freelance writing, veterinary medicine, and stock brokerage.