1134th General Monthly Meeting

"Biocosmology: a new science"

Dr Charley Lineweaver, Senior Fellow
Planetary Science Institute, Australian National University

Wednesday 4 May 2005, 7 pm (bar open from 6 pm)
Conference Room 1, Darlington Centre, Sydney University, City Road

As we learn more about the origin and evolution of the universe and about the prerequisites for the emergence of life, the connections between cosmology and biology are becoming more obvious and more quantifiable. Where and when in the universe did the first molecules form? Where and when did the first stars and terrestrial planets form? Where is the liquid water in the universe? Since life emerged early in the history of the Earth, does that mean that life is common in the universe? I will summarize our knowledge and speculations about the origin of life in our galaxy and in the universe.

Dr Lineweaver is an American permanently resident in Australia, and has been a Senior Lecturer at the University of NSW since 2002. He received his PhD in Physics at Berkeley, University of California in 1994, after studying at Berkeley and the Ludwig-Maximillian Universität, München.

In addition to working at Berkeley, he was a Post-doctoral Fellow at the Observatoire Astronomique de Strasbourg, France, from 1994 to 1997 and a Vice-Chancellor's Research Fellow at the University of NSW from 1997 to 2000.

Dr Lineweaver was a Eureka Prize finalist for Science Journalism in 2001 for his article "The Origin of the Universe" — the 13 billion year history of the Universe, published in 2000. He has published numerous papers and has set up a course teaching Astrobiology entitled "Are We Alone?" — the most popular General Studies course offered by the School of Physics at the University of NSW. His research interests include cosmology, astrobiology and statistical analyses of extrasolar planets.

Report on the General Monthly Meeting by Jak Kelly

Dr Charles Lineweaver of the Australian National University gave an extremely interesting talk, basically on where we came from and why we are here, in this part of the galaxy. How did life emerge from the hydrogen and helium that constituted, and still does, the main part of the universe in the beginning? Early cosmology was based on speculations with little experimental evidence but over recent decades has become a much more exact science as measurements of what is out there have accumulated. The study of the origins of life in the cosmos is in its early speculative state, like early cosmology, but progress is likely to be much more rapid as relevant information increases.

There is only a limited habitable zone around a star for water-based life. It must be liquid, not ice or steam. Earth is in this fortunate position. Living organisms also need heavier atoms such as carbon, nitrogen, oxygen and others. These atoms are made in stars and widely distributed when the stars end their careers in the massive explosions of supernova. The heavy atoms, quaintly called metals by astronomers, are spread throughout the galaxy; so will life be likely to emerge on planets around the hundreds of billions of stars throughout our galaxy? Dr Lineweaver and others speculate that there is a life-friendly zone in the galaxy, just as there is about a particular star. This zone is defined by the presence of enough "metals" and the absence of too many stellar explosions, which produce doses of radiation lethal to life on nearby stars. This gives us a spherical shell about the massive black hole at the galactic centre. The inner radius is far enough out to avoid the lethal turmoil of frequent star birth and death in the more crowded inner reaches of the galaxy and the outer radius is limited by the diminished supply of "metals".

Again we are lucky. Our sun is in this zone. Has life also made it around the millions of other nearby stars? Perhaps we will soon know. Planet-finding is a growth industry with over a thousand so far, although most are unsuitable for life as we know it. Finding small rocky earth-like planets is more difficult but when we do we won't have to wait for SETI to decipher radio signals. An analysis of the atmosphere will tell us if life is on its way, although we may have to wait the odd billion years or so to have meaningful conversations with them.