October 23, 2008

Hans Bethe Lecture Draws Large Crowd

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“If you looked far back enough, the universe should have been decelerating before it [started] accelerating,” said Prof. Robert Kirshner, Clowes Professor of Science, Harvard University, and the former president of the American Astronomical Society, at last night’s lecture entitled “The Accelerating Universe: Einstein’s Blunder Undone.”
Kirshner’s lecture last night was one of three talks on schedule for this year’s Hans A. Bethe Lecture Series. Over 200 people, including students, professors, elementary school kids and their parents, attended the lecture at in Schwartz Auditorium.
The lecture rejuvenated Albert Einstein’s proposition that a cosmological constant could have explained the nature of a stagnant universe. This assumption was later dubbed the “greatest blunder,” after George Gamow, one of Einstein’s colleagues, claimed in his autobiography, My Word Line.
Co-founded by the College of Arts and Sciences and the Physics Department in 1977, the Hans A. Bethe Lecture Series were created to honor its bearer, late professor Hans A. Bethe, physics, a Nobel Prize winner whose research spanned the fields of quantum and nuclear physics.
“[Bethe was] the most important faculty member that Cornell has ever had,” argued Prof. Saul Teukolsky, the Hans A. Bethe Professor of Physics and Astrophysics and chair of the Physics Department, who cited Bethe’s initiative of lifting up the standards of all sciences that were taught at Cornell during his time as a professor.
During his lecture, Kirshner argued that the ultra bright light that emanates from stellar explosions suggest that “the expansion of the universe is not slowing down as we expected,” rather, it is speeding up. In other words, the Universe is accelerating due to Dark Energy, a component that makes up 74 percent of the entire Universe.
Kirshner went on correct the notion that the Milky Way was the sole composition of the universe in 1917, when Einstein made his rather famous inference of a cosmological constant. It has now been shown that the earth’s own galaxy, the Milky Way, is one of a hundred billion galaxies that span the accelerating Universe.
“I think it must be static,” Kirshner said, humorously suggesting that Einstein conceived the notion of a static Universe while sitting down with a blank face in the front row of a lecture room.
Following Einstein’s controversial hypothesis, Edwin Hubble, using his 100-inch telescope at Mount Wilson Observatory in California, showed that the Milky Way was not the only galaxy, thereby suggesting that the Universe is a much larger entity.
While explaining the underlying mechanism of telescopes, Kirshner mentioned that the images obtained from the telescopes depict the state of the universe in the distance past, hundreds of millions of years ago. As a result, one cannot predict the universe’s near future expansion rate by means of present day technology, he said. He explained that the image of people that one sees in a lecture room depicts the state of the individuals after reflecting light in the previous second. Likewise, pictures of the widespread universe obtained from telescopes are in a large order of magnitude of units called light years.
Kirshner further argued that the sun is not at the center of the Milky Way. In fact, if one assumes the universe is moving constantly in all directions, i.e. “stretched out” equally from all sides, the resultant effect would not necessarily put the Milky Way at the center. In reality, the galaxies that are close to the Milky Way are moving away from the Milky Way, and those that are far away are moving much more rapidly away. Following this analogy, he asserted the point that the Universe is accelerating. He noted that a currently accelerating universe may not necessarily mean that the universe is “stuck in acceleration” forever.
As for research motivation, Kirshner explained that although scientific findings could ultimately lead to wealth and safety, his reward is “the joy of finding out how the world works.”
Chris Elliot, a senior from Ithaca High School attended the lecture in order to earn extra credit in his AP biology course, but said he found the theory behind an accelerating universe fairly interesting.
Ranajay Ghosh grad described the lecture as “very informative and totally entertaining.” He added, “I got what I expected from the talk, [which was delivered by] a pioneer in his field. He’s kind of rockstar physicist.”