The Bethe Lecture Series - Fall 2008

October 20 -24, 2008

Dr. Robert P. Kirshner
Harvard University
 

 

Robert P. Kirshner is Clowes Professor of Science at Harvard University. He graduated from Harvard College in 1970 and received a Ph.D. in Astronomy at Caltech in 1975.  He was a postdoc at the Kitt Peak National Observatory, and served on the faculty at the University of Michigan for 9 years.  In 1986, he moved to Harvard. He chaired the Astronomy Department from 1990-1997 and headed the Optical and Infrared Division of the Center for Astrophysics from 1997-2003.  He was Master of Quincy House, one of Harvards undergraduate residences from 2001-2007.  In 2007, he was on sabbatical at the Kavli Institute for Theoretical Physics at UC Santa Barbara.
 
Professor Kirshner is an author of over 200 research papers dealing with supernovae and observational cosmology. His work with the ” High-Z Supernova Team” on the acceleration of the Universe was dubbed the “Science Breakthrough of the Year for 1998″ by Science Magazine.  Kirshner and the High-Z Team shared in the Gruber Prize for Cosmology in 2007. A member of the Amercian Academy of Arts and Sciences, he was elected to the National Academy of Sciences in 1998 and the American Philosophical Society in 2004.   He served as President of the American Astronomical Society from 2003-2005.   Kirshner was given the Distinguished Alumni Award by Caltech in 2004.
 
Kirshner is a frequent public lecturer on science. He is also the teacher of Science A-35, a course for Harvard undergraduates entitled “The Energetic Universe.” His popular-level book “The Extravagant Universe: exploding stars, dark energy, and the accelerating cosmos” was published by Princeton University Press. It won the AAP Award for Best Professional/Scholarly Book in Physics and Astronomy and was a Finalist for the 2003 Aventis Prize.  The Extravagant Universe is available in paperback and has been translated into Japanese, Portuguese, Spanish, and Czech.

Physics Colloquium, Monday, October 20, 4:00 PM
Schwartz Auditorium, Rockefeller Hall

The Mystery of Dark Energy

Astronomical observations of the history of cosmic expansion made 10 years ago showed that the universe is accelerating.  When combined with evidence from the cosmic microwave background and from the distribution of galaxies, all signs point to a universe that is ~1/3 non-baryonic dark matter and ~2/3 dark energy.  The leading candidate for the dark energy is a variant on Einstein’s cosmological constant.  But the natural energy scale for vacuum energy exceeds the observed value by a factor of 10^120.  This is not good quantitative agreement.  I will describe ongoing and forth-coming observational programs that will draw tighter constraints on the nature of the dark energy and a proposed Joint Dark Energy Mission (joint between the DOE and NASA) that aims to probe this deep mystery at the heart of physics.

Public Lecture,
Wednesday, October 22, 7:30 PM
Schwartz Auditorium, Rockefeller Hall

The Accelerating Universe: Einstein’s Blunder Undone

Light from exploding stars halfway across the universe reveals an astonishing fact:  the expansion of the universe is speeding up!  Astronomers attribute this to a mysterious “dark energy” that drives cosmic acceleration.  And we need a lot of it–dark energy accounts for 2/3 of the matter and energy in the universe today.  Curiously, when Albert Einstein first thought about gravity in the universe, in 1917, he introduced a repulsive “cosmological constant” that he thought would match a static, unchanging universe.  When, in 1929, astronomical observations showed the universe was not static, but expanding, he stopped talking about the cosmological constant. It has dubbed his “greatest blunder.”  But today’s observations show that we need something that acts just like the cosmological constant to produce cosmic acceleration.  This talk will show how we use observations of supernova explosions to trace cosmic history and sketch plans to learn more about the nature of the dark energy, one of the deepest mysteries of the physical world.

Astronomy and Space Sciences Colloquium,
Thursday, October 23, 4:30 PM,
Schwartz Auditorium, Rockefeller Hall

Fundamentals of Supernova Cosmology

Supernova observations form the foundation of evidence for an accelerating universe.  Diligent work on supernova spectroscopy and supernova photometry in the nearby universe allows for tests of the assumptions that make supernovae so powerful at high redshift.  The most serious systematic problem in supernova measurements is produced by uncertainties in absorption by interstellar dust.  I will describe the work being carried out at the Center for Astrophysics in the near infrared that promises to help solve this problem. I will also discuss the current state of the CfA program at low redshift, the ESSENCE program at intermediate redshift, and the Higher-Z program with the HST at redshifts near 1.  I will show today’s best inferences for the properties of dark energy and outline the plans for improving them.  A flat universe with a cosmological constant for the dark energy is consistent with all the current constraints. 

An Image of our Milky Way Galaxy   

A Supernova in a nearby galaxy

The Vicinity of SN 1987A, the Brightest Supernova in 383 Years

Close-up View of SN 1987A
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The Bethe Lecture Series, established in 1977 by the Cornell Department of Physics and the College of Arts and Sciences, honors Hans A. Bethe who joined Cornell’s faculty in 1936, and whose research extended across fields as diverse as the quantum theory of solids and the nuclear processes that power the sun, receiving the Nobel Prize for the later work in 1967.  Bethe continued to make significant scientific contributions until his death in 2005.
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“…the spirit of physics, the idea of discovery … the beauty of how it fits together, and the beauty that the laws of physics are immutable.”
                                                           -Hans A. Bethe

 

 

 

 

 

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