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Prof. Raju Raghavan
(Virginia Tech, Director of IPPAP)
"How does the Sun Shine?"
Date: Wednesday, November 16, 2005
Time: 7:00pm
Location: 1670 Litton Reaves Hall
Admission: free and open to the public
The Sun is the source of energy that has created and preserved all life on earth.
Not surprisingly, humanity has wondered about how the Sun shines - in lore, lyric, and literature,
epitomized by the simple query of the child:
"twinkle twinkle little star, how I wonder what you are?"
The question became a scientific puzzle only about 150 years ago.
A series of brilliant ideas and experiments in the early 1900's
sharpened the puzzle into a scientific crisis.
The breakthrough came with Einstein's theory of the equivalence of mass and energy and
the development of quantum mechanics in 1925. The amazing answer came a decade later with
the birth of nuclear physics: energy from the fusion of atomic nuclei in the 15 million degree core of the Sun.
Is this idea really correct? The question could only be settled by experiment,
but how does one "look into"
the core of the Sun and verify the presence of the thermonuclear furnace there?
The clue was that the same fusion reactions that power the Sun also emit neutrinos that
interact so weakly with matter that they can escape the huge mass of the Sun.
We can actually see the solar burning if we can detect these neutrinos.
Doing that in practice, however, is almost a science fiction adventure: Huge detectors
nearly a thousand tons in mass must be placed, ironically for a device to see the Sun,
in caverns miles underneath tall mountains. Amazingly, the experiments still worked and
proved conclusively that the Sun is indeed powered by fusion reactions. But they did much more.
They revealed stunning surprises in a different discipline - elementary particle physics,
by basically rewriting it with new chapters on the neutrino itself.
The adventure continues today with new questions such as
- why is there more matter in the universe than antimatter? - and
- did the Sun always shine steadily or did it vary in ancient times and cause vast changes
in weather on the earth a million years ago? Ingenious new solar neutrino experiments are
being developed at Virginia Tech to answer these questions.
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Prof. David Reitze
(University of Florida)
"The Laser Interferometer Gravitational Wave Observatory:
Lasers Probing the Frontier of Astrophysics"
Date: Friday, October 28, 2005
Time: 2:30pm
Location: 130 Chemistry-Physics Building
Admission: free and open to the public
The Laser Interferometric Gravitational Wave Observatory (LIGO) is poised to open a new window on the universe - the detection of gravitational waves from distant large-scale astrophysical sources. Gravitational waves were predicted by Einstein almost 90 years ago but never been observed directly despite a number of experiments over the last 40 years. While there exists strong indirect evidence for gravitational waves, it is only with the construction of large-scale high precision interferometers that direct detection of gravitational waves is possible. Gravitational waves are miniscule dynamic strains applied to space-time by motion of massive astrophysical objects. A passing gravitational wave will expand and contract the distance between two mirrors ('test masses') in the arms of an interferometer. Direct observation of gravitational waves presents a formidable challenge, because the effect is expected to be infinitesimal, less than one part in 10-22.
The astrophysical motivation for detecting gravitational waves is compelling. Unlike the visible sky, the gravitational wave 'sky' is completely unexplored. Potential gravitational wave sources include binary neutron star and black hole systems and pulsars. The LIGO detectors and its partner GEO600 in Europe have the sensitivity to observe gravitational waves not only in our own galaxy, but in neighboring galaxies, thus opening an absolutely unique window into these phenomena.
In the first part of the presentation, I will give an overview of gravitational waves - what they are and where they come from - and describe in general terms the techniques that gravitational wave astrophysicists use to hunt for them. In the second part of the presentation, I will describe the LIGO interferometers and present results from the first searches for gravitational waves by LIGO.
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Prof. Mildred S. Dresselhaus
(MIT)
"Impacts of Nano-Technology in the 21st Century"
Date: Friday, September 16, 2005
Time: 2:30pm
Location: 130 Chemistry-Physics Building
Admission: free and open to the public
A brief survey is given on how the properties of materials at the
nanoscale differ from their bulk counterparts. We envisage that
future applications of nanostructures will focus on these
differences in properties and one applications area where significant
impact may be expected is in addressing the grand challenge of our
energy future. This topic will be further developed.
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Prof. Djordje Minic
(Virginia Tech)
"Albert Einstein's guide to a Brief History of Physics"
Everything you ever wanted to know about the history of physics (but were afraid to ask),
from the viewpoint of Albert Einstein's scientific achievements.
Date: Friday, April 15, 2005
Time: 2:30pm
Location: 210 Robeson Hall
Admission: free and open to the public
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Prof. John Simonetti
(Virginia Tech)
"The Accelerating Universe: Einstein's Greatest Blunder - NOT!"
Date: Wednesday, March 30, 2005
Time: 7:00pm
Location: 1670 Litton Reaves Hall
Admission: free and open to the public
During the past century our understanding of the structure and evolution of the universe
has increased dramatically. From humble beginnings, astronomers have surveyed the vast
reaches and contents of the universe, demonstrating that it is expanding, and pinned down
a reasonably precise value for its age. Along the way, Albert Einstein's contributions have
played a major role. His General Theory of Relativity set the stage for our exploration,
and it now appears he was onto something that many researchers in his day, not even he,
could accept. Recent observations have led many to conclude that the expansion of the
universe is accelerating, whereas deceleration would be expected if ordinary matter dominates
the contents of the universe. This surprising result implies that about 73% of the energy
in the universe is in a form we know almost nothing about, beyond the name we have placed
on it: "dark energy". Another 23% is "dark matter," known only from its attractive gravitational
effects. Only about 4% of the content of our universe is ordinary matter, the stuff in the
periodic table of elements! Interestingly, the basic story behind these conclusions is
understandable using very simple physics, as this talk will show.
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