Better Physics

Kara Hoffman, University of Maryland

IceCube

Neutrinos are unique astronomical messengers which may provide critical information in identifying sources of cosmic rays and the processes out of which they are born. The search for astrophysical neutrinos has given rise to a new generation of neutrino telescopes of an unprecedented scale, including the IceCube Neutrino Observatory, the world’s first kilometer scale neutrino telescope, which was constructed by instrumenting the clear, deep ice at the South Pole with 5160 photomultiplier tubes. Both IceCube’s science potential and its extreme location provide excellent tools for engaging students, especially in this year as we prepare to mark the 100th anniversary of Amundsen and Scott’s historic expeditions to the Pole. I will discuss the science goals of IceCube, as well as the unique challenges associated with constructing and operating a large scientific instrument in one of the world’s most remote locations.

Duncan Brown, Syracuse University

LIGO: Teaching its physics

Gravitational-wave astronomy is an exciting new frontier in 21st century astronomy and physics. Gravitational-wave observatories, such as LIGO, are targeting some of the most violent processes in the universe: the collision of black holes, exploding stars and even the big bang itself. These astrophysical events capture the interest of physics majors and non-majors alike. Interferometric gravitational-wave detectors are instruments of mind-boggling sensitivity: their displacement sensitivity is comparable to measuring the distance to the nearest star to a few tens of microns. Both the technologies used in the detectors and the astrophysics of LIGO’s sources are rich with opportunities for teaching undergraduate physics. I will present some examples from gravitational-wave astrophysics and experiment.

Gregory Snow, Dept. of Physics and Astronomy, University of Nebraska-Lincoln

High Energy Astrophysics: The Auger Observatory

Located in Mendoza Province, Argentina, the Pierre Auger Observatory is the world’s largest experiment studying ultra-high energy cosmic ray particles from outer space. The experiment uses a combination of 1600 surface detectors (water Cerenkov detectors spread over an area of 3000 square kilometers), and 27 fluorescence telescopes overlooking the surface detector array to measure extensive air showers created by incoming, primary cosmic ray particles. Physics results on the origin of the highest energy cosmic ray particles, their energy spectrum, and their particle identity will be presented. In addition, education materials about the Observatory and cosmic ray physics developed by the Observatory’s Education and Outreach Task will be described.

Douglas Caldwell, NASA-SETI

The Kepler Mission: Searching for Planets using 17th Century Physics (with a few modern twists)

The discovery of the first exoplanets in the 1990’s confirmed that giant planets were common in the Galaxy but left open the question of the prevalence of terrestrial planets. NASA’s Kepler Mission was launched in March 2009 to determine the frequency of Earth-size planets orbiting within the habitable zone of their parent stars. Kepler monitors more than 100,000 stars nearly continuously, searching for the small drop in brightness as the planet passes in front of, i.e., transits, its host star. Using essentially the same methods described by Johannes Kepler and put into practice during the 17th and 18th century transits of Venus, we determine the planet’s size, orbital period, and orbital semi-major axis.  Using simple energy balance arguments developed in the 19th century, we estimate the equilibrium temperature of the discovered planets. In special cases, we can use 20th century relativity to directly determine the mass of planets from the transit light curve alone. To date, Kepler has discovered more than 1,200 planet candidates; somewhat surprisingly, more than 400 of them are in multiple planet systems. As Kepler’s observations continue, we will be able to answer the question of whether Earth-size planets are common, or whether we really do live in a geocentric universe.

Joseph Amato, Dept. of Physics and Astronomy, Colgate University

Using Astronomy to Motivate and Teach Introductory Mechanics

Physics from Planet Earth (PPE) is a one-semester, calculus-based introductory course in classical mechanics intended for first year students of physics, chemistry, astronomy and engineering. Most of the core topics in mechanics are included, but many of the examples and applications are drawn from astronomy, space science, and astrophysics. The laws of physics are assigned the task of exploring the heavens – the same task addressed by Newton over 300 years ago at the birth of classical mechanics. How do we know the distance to the Moon, Sun, or other galaxies? How do we know the masses of the Earth, Sun, and other planets and stars, and why do we believe in “missing” mass? As a physics course, PPE concentrates on how we know rather than on what we know. Examples and applications include those of historical importance (the Earth-Moon distance, the Earth-Sun distance, Ptolemaic vs. Copernican models, weighing the Earth) as well as those of contemporary interest (Hubble’s Law, rocket propulsion, spacecraft gravity boosts, the Roche limit, search for extrasolar planets, orbital mechanics, pulsars, galactic rotation curves). The course has been taught successfully at Colgate for over a decade, using materials that have been developed and refined during the past 15 years. Developers of PPE are eager to enrich the course by identifying other topics in contemporary astronomy that can be adapted for the first year physics audience.

Edward Prather, CAE, University of Arizona,

Research on Students’ Learning of Astronomy: Clues for Ways to Get Students to Learn Physics¹

For the past decade members of the Center for Astronomy Education (CAE) have been developing and conducting research on the effectiveness of learner-centered instructional strategies and curriculum materials that put students in an active role in the traditional lecture classroom.  The results of this work have been incorporated into a series of “Teaching Excellence Workshops” that members of CAE have been conducting around the nation as part of the JPL’s NASA Exoplanet Exploration Public Engagement Program and the NSF CCLI Phase III Collaboration of Astronomy Teaching Scholars (CATS) Program.  We present the results of a national study on the teaching and learning in introductory astronomy courses in which these instructional strategies were used.  Nearly 5000 students enrolled in 70 classes taught by 36 different instructors at 30 institutions around the United States participated in this study.  The classes varied in size from very small (N<10) to large (N>700) and were from all types of institutions, including both 2-year and 4-year colleges and universities.  Results show dramatic improvement in student learning with the increased use of interactive learning strategies, independent of type of institution or class-size and after controlling for individual and ascribed population characteristics.  The results of this work will inform the development of instructional programs designed to increase the learning of physics by leveraging the powerful and conceptually engaging topics presented in the study of the universe.
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¹This material is based upon work supported by the National Science Foundation under Grant No. 0715517, a CCLI Phase III Grant for the Collaboration of Astronomy Teaching Scholars (CATS). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Barbara Ryden, Ohio State University

Interpreting Hubble’s Law

Observational cosmology provides an excellent platform for teaching important concepts in physics. In part, this is because modern observations create a “gee-whiz” reaction that captures students’ imaginations. In part, however, it’s because even familiar warhorses of cosmology, such as Olbers’ Paradox and Hubble’s Law, demonstrate how our underlying assumptions affect our interpretations of data.

Focusing on Hubble’s Law as my example, I’ll dissect how (and why) Edwin Hubble leapt from measured redshifts and fluxes to interpreted velocities and distances. Then I’ll examine how, at levels from Astro 101 to graduate courses, Hubble’s Law can lead to discussion of the nature of space and of motion. In particular, since a Hubble-like relation can occur both in Newton’s universe and Einstein’s universe, Hubble’s Law provides an opening for discussing the conceptual and observational differences between the Newtonian concepts of gravity, space, and time, and the general relativistic concept of spacetime.

David Helfand, Quest University Canada and Columbia University

X-ray Views on the Physics of the Universe

Over the past sixty years, our ability to transcend the atmospheric filter that limits our view of the Universe has allowed us to open dozens of octaves of the electromagnetic spectrum for astronomical observations. I will begin with a musical analogy for this phenomenon and then focus in the 0.1-100 keV portion of the spectrum. From the first V-2 rockets that detected the Sun’s X-rays on photographic film to the sub-arcsecond imaging of the Chandra Observatory, the last six decades have seen a greater improvement in both angular resolution and sensitivity in the X-ray band than did the 400 years between Galileo’s telescope and Hubble. Physical principles from optics, atomic and molecular physics, photon counting, and kinematics are illustrated in this history. The objects we observe in the high energy universe provide an even richer source of the manifestations of physics on cosmic scales: magnetic reconnection that heats the solar corona, the fluid dynamics of accretion disks, the general relativistic phenomena seen in neutron stars and black holes, the nuclear physics of stellar evolution, the hydrodynamics of supernova explosions, the thermal physics of hot gases from the interstellar to the intergalactic medium, and the striking illustration of dark matter in colliding galaxy clusters may all be used to explicate physics, much of which cannot be reproduced on a laboratory scale.

Roger Blandford, KIPAC, Stanford University

New Horizons in Physics Education

Modern astrophysics is very well-suited to motivate, substantiate, and illustrate the concepts and applications that need to be conveyed when teaching physics. Astrophysics exploits the power of the image and taps into a common fascination with exploration and discovery that unites student and teacher, scientist and lay person. It can draw young people into careers in technology, science, medicine, and education, and it is a powerful way to help those who choose other careers to develop critical thinking skills and trust in rational argument. Astrophysics offers physics students a sure path to confident familiarity with principles and techniques of great generality. Besides, it is a lot of fun!

In this talk, I shall draw on recent astrophysical developments for examples that illustrate each of these attributes. I shall conclude by asking some questions concerning the skills that today’s students will need when they enter the workforce.

Duncan Brown, Syracuse University

The New Astronomy of LIGO

Gravitational waves are among the most remarkable predictions of Einstein’s theory of general relativity. These waves—ripples in the curvature of spacetime—carry information about the changing gravitational fields of distant objects. Almost a century after Einstein first predicted the existence of gravitational waves, scientists are on the brink of directly detecting them for the first time. Gravitational waves will be a radically new tool for exploring fundamental physics and astronomy. They will probe the physics driving the most violent astrophysical events in the universe in ways inaccessible to electromagnetic observations. When the gravitational-wave window on the universe opens, the potential for discovery will be immense.

Construction of the U.S. Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) is well underway. Within the next five years, observers at Advanced LIGO expect to make the first detections of gravitational waves. Gravitational waves produced by the collision of black holes, asymmetric core collapse supernovae, rapidly spinning neutron stars, and even by the Big Bang itself are targets for detection in the years to come. I will give an overview of the new field of gravitational-wave astronomy: how the waves are generated, our efforts to detect them and what we hope to achieve when we can observe the universe in this new way.