Living in the Universe

An Astrobiology Cornucopia

April 27, 2008 on 8:00 am | In Overview | Comments Off

Fourth Week of April 2008

Ladies and Gentleman, boys and girls, earthlings and aliens, I just came back from AbSciCon, the astrobiology science conference in Santa Clara, and my head is so full of astrobiology that I think it might explode. Three days, six hundred and fifty papers, two thousand authors total, twenty-eight countries represented. I gave an education talk on my Second Life work, but the breadth of research results made it an incredible meeting. I can barely give you a sense of what was involved, but I’ll select three papers to talk about in particular.

The keynote address at the beginning of the first day was a wonderful overview of the cosmic context of life given by Lord Martin Rees. Yes, if you weren’t aware of it, over in Britain there’s a scientist who’s so famous he not only was knighted and became Sir Martin Rees but he is now in the House of Lords. Even Isaac Newton didn’t go beyond a knighthood. Martin Rees is also the Astronomer Royal, and he made a joke about the fact that his primary duty there involves casting the queen’s horoscope. He’s the president of the Royal Society, and he holds Newton’s Chair of Astronomy hundreds of years later. He also happens to be a really nice guy.

Rees a brilliant and preeminent cosmologist, and he talked about the setting for life in the universe on the largest scales. He reminded the audience that we expect the universe to be fecund and have material that can form life and biology because of the way carbon has been created and flung out from stars through cosmic time. He also—unusually for most scientists—was strongly supportive of SETI, pointing out that it’s an important philosophical experiment to actively look for extraterrestrial intelligence, though he noted that we’re only likely to detect a small fraction of all the possible brains out there. He made several references to science fiction and in one aside said that he preferred first-rate science fiction to second-rate science any day, but mostly he was talking about cosmology.

He homed in on the six numbers that describe the universe on the largest scales and the fact that some of those numbers are poised at values that permit the existence of life. These cosmic coincidences have begged an explanation by cosmologists, and the most popular one involves the fact that we live in a multiverse, a “small” pocket of space-time that could be part of a much larger construct. Most of these universes in the multiverse are sterile because their physical properties would not permit stable atoms or long-lived stars or biology of any kind, but ours of course is not. He also gave a sense of how vast the totality of the universe could be, so vast that it’s kaleidoscopic in proportion and so vast that all the possible probability outcomes may occur somewhere in space and time. It was a head spinning talk, and it really set the scene for all the work that would follow.

The second talk I want to highlight was given by Richard Muller at the University of California, Berkeley. He gave a wonderful overview of a new signal seen in the extinction of marine creatures on Earth in the past half billion years, that shows a strong periodicity. We know there have been mass extinctions in the history of life on Earth, but it’s mostly been thought that they were random, probably caused by cosmic impacts from space or some sort of climate catastrophe. But Muller has used an enormous compendium by the late Jack Sepkoski of fossil marine data to do a new analysis, and he’s found a very strong evidence for a sixty-two million year cycle in the death of species.

His new analysis involves a lot of new data that he was willing to share with anyone in the audience, making available his Excel spreadsheet. It involves tens of thousands of marine species. The sixty-two million year cycle only leaps out when a new age calibration is used. It turns out that the ages for fossil dating over the past half billion years had errors of up to ten or twenty million years, and that was enough to smear out this signal. But with the new age calibration it was obvious in all his graphs. It’s seen separately in trilobites, bivalves, porifera, and brachiopods, less strongly in gastropods, cephlopods, and fish. He also sees weaker evidence for a hundred and forty million year cycle. The existence of two periodicities in the extinction of marine creatures over half a billion years begs for an astronomical explanation because something that’s periodic is probably coupled to orbits or gravity in some way.

The potential explanation of these two cycles was provided by a pair of talks that followed by Mikhail Medvedev and Adrian Melott. The hundred and forty million year cycle, for which the evidence is still fairly weak, is probably caused by the periodic passage of the Sun and the Solar System through the spiral arms of the Milky Way galaxy. The sixty-two million year cycle exactly matches the period of the Sun’s motion up and down in the plane of the Milky Way galaxy.

Imagine the Milky Way and its disk as an old style phonograph record, a 33 record, warped by heat so it is corrugated and the Sun travels up and down and in and out of the plane of the galaxy as it goes round, with a two hundred and fifty million year orbit and a sixty-two million year cycle for the up and down motion. At its maximum excursion from the plane of the Milky Way, the Earth and the Solar System sees an increased flux of cosmic rays, and this increased flux of cosmic rays causes mutation of DNA, climate change, and the combination is a one-two punch that kills species. So we have a very neat explanation for the periodicity of extinctions. It’s caused by our large-scale astrophysical environment, and we might wonder if other life bearing planets in the Milky Way galaxy are subject to similar periodicities.

The last talk I want to mention was by Denise Herzing from the Wild Dolphin Project in Florida. The Wild Dolphin Project is just what you might imagine. This woman has an incredible job. For nearly twenty-five years she’s spent five months of the year out in the Bahamas tracking, playing, and working with Atlantic spotted dolphins. She’s a behaviorist, and they try to be as least intrusive as possible in the dolphin culture. For that span of time they’ve studied two hundred individuals over three generations, and they know many of these individuals by sight and behavior after that length of time.

Remember, these are wild dolphins. This is not a controlled situation, and yet they’ve managed to record sounds to correlate behavior and vocalization and learned an enormous amount about dolphins that wasn’t known before. As Carl Sagan noted some years ago, we’ve managed to train dolphins to speak about two hundred words of English by tapping out symbols on a keyboard but we still speak exactly zero words of dolphin. So who’s smarter? Denise’s presentation made it clear that these incredible creatures display fantastically complex behavior and socializations.

She and her colleagues were able to train the dolphins to use a portable underwater keyboard to tap out symbols and essentially communicate with the humans. The dolphins that participated were mostly the young females. It seems that the young males were off fighting, as in other species, and what she summarized was a rich tapestry of subtle behavior, plus evidence of substantial intelligence and problem-solving abilities and of distinct personalities amongst the dolphins. That’s perhaps a good way to leave the idea of astrobiology from this major recent gathering of astrobiologists—while we look for intelligent, interesting creatures out in space, we should remember that we share a planet with extraordinary creatures that we don’t yet fully understand.