Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session Q5: Evolution: From the Big Bang to Us |
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Sponsoring Units: FPS FEd Chair: Barbara Levi, Physics Today Room: Hyatt Regency Dallas Pegasus B |
Monday, April 24, 2006 1:30PM - 2:06PM |
Q5.00001: Evolution of the Universe Invited Speaker: Cosmology is in the midst of a scientific revolution that is establishing its lasting foundations. The good agreement between many different sorts of observations and the predictions of the now-standard Lambda Cold Dark Matter (LCDM) theory gives us hope that this is humanity's first picture of the history of the universe as a whole that might actually be true. An unexpected feature of this new picture is that we humans appear to be central or special in many ways -- for example, we are made of the rarest stuff in the universe (stardust); we are intermediate in size between the smallest possible size (the Planck length) and the largest size (the cosmic horizon); and we are living at a pivotal time: the period in the history of the universe when its expansion began to accelerate rather than slow down, and in the middle of the ten-billion-year lifetime of our solar system and of the billion year most habitable period of our planet, and at what must be the end of the exponential growth of human impact on the earth. This talk\footnote{Based on a new book, The View from the Center of the Universe: Discovering Our Extraordinary Place in the Cosmos, by Joel R. Primack and Nancy Ellen Abrams (Riverhead Books, April 2006).} will review key observations that support modern cosmology, describe some symbolic ways of understanding the modern cosmos, and discuss some possible implications of a cosmic perspective for our 21st century worldview. [Preview Abstract] |
Monday, April 24, 2006 2:06PM - 2:42PM |
Q5.00002: Evolution of a Habitable Planet Invited Speaker: Earth has remained habitable, and inhabited, over most of its 4.5-Gyr history despite an appreciable (30{\%}) increase in solar luminosity over time and despite catastrophic events such as asteroid impacts and ``Snowball Earth'' episodes that have threatened biological survival on a global scale. Life has survived partly because of the resilience of the biota and partly because of feedback mechanisms that help to stabilize Earth's global climate. In particular, buildup of volcanic CO$_{2}$ during times when the climate is cold provides a strong negative feedback that helps keep Earth within the temperature regime favorable to life. The same processes that help stabilize Earth's climate should operate on other Earth-like planets, if they exist; thus, it is plausible that life could exist elsewhere. This hypothesis is now on the verge of being tested. NASA's twin \textit{Terrestrial Planet Finder (TPF)} missions, which could be launched as early as 2015-2020, will look for Earth-like planets around nearby stars and, if they are found, provide spectroscopic information on their atmospheres. Between them, these missions should be able to look for absorption bands of O$_{2}$, H$_{2}$O, CO$_{2}$, and O$_{3}$. Both O$_{2}$ and O$_{3}$ are considered to be good indicators of life for planets orbiting within the liquid water habitable zone of their parent star. NASA should be encouraged to give these missions high priority, so that we can answer these fundamental questions about the distribution of life in the universe. [Preview Abstract] |
Monday, April 24, 2006 2:42PM - 3:18PM |
Q5.00003: Evolution of Biological Diversity Invited Speaker: A conservative estimate posits approximately ten million species presently inhabiting Earth, and these are clearly only a small fraction of those that have existed throughout Earth's history. Although various types of selective mechanisms have been identified as generating this diversity, and several chance mechanisms as well, the relative importance of these mechanisms is not firmly resolved. We review the current status of the discussion and some of the associated political and social ramifications. [Preview Abstract] |
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