CapitalistImperialistPig

Mike Brown's penultimate lecture in his Caltech/Coursera Solar System course concerns what he calls "the best experiment to find life in the Solar System" yet. On it's trip to Jupiter, the Galileo spacecraft flew by a couple of planets to get a slingshot boost on its way, taking some data in the process. The data consisted of infrared spectra, imagery at multiple filtered wavelengths, and radio data. Some of the data was highly suggestive: oxygen in the atmosphere, presence of liquid water, very abundant methane in the atmosphere, and some peculiar features in the wavelength filtered data. All of the above were suggestive of the presence of life, but hardly conclusive. You have perhaps guessed the identity of the planet in question: Earth. The data, analyzed by Carl Sagan and colleagues, also included imagery with a resolution of roughly 1 kilometer. No definitive signs of human construction were found at that scale. The only definitive evidence of life, and...

Or, at least, less than 100. We know that, says Mike Brown, because the level of methane on Mars is less than 1 part per billion - about the amount that would be produced by 100 cows, burping. It's not exactly a shock that Mars is not prime cattle country, but the aforementioned result is also a major blow to one of Mike's favorite theories: that some kind of life on Mars was all but certain since life from Earth was very likely transported to Mars in the Early days by meteorites blown off the Earth in major collision, to land there when the planet was more hospitable. Even today, it seems likely that Mars has locales where methanogens would survive and reproduce. Of course the reverse voyage scenario is also possible. In which case it would be a bit tragic that the planet that (perhaps) gave us birth, no longer supports life.

Geoffrey Miller has a theory about Fermi's paradox . Seventy years or so ago, a bunch of physicists were wondering about the plausibility of extra-terrestial intelligence. It was obvious already that there were lots of stars, and it seemed likely that many of them had planets. Once intelligent life had evolved, it shouldn't take long to colonize a galaxy. Fermi listened patiently, then asked, simply, “So, where is everybody?” That is, if extraterrestrial intelligence is common, why haven’t we met any bright aliens yet? This conundrum became known as Fermi’s Paradox. The paradox has gotten somewhat sharper since. We have now discovered hundred of extraterrestial planets, and it's clear that they are pretty common. It's plausible, if not yet demonstrated, that there are many which are good candidates for supporting life. The evolution of life and especially intelligence is more problematic - it took a long time here on Earth. Still it's plausible - again not y...

Would you want to know when you are going to die, or at least when the physical decrepitude of age will overwhelm you? It seems that there is a message, if not exactly to the main , at least to sophisticated molecular analytic engines, written in your cells . For the most part, we live longer than our individual cells. Cells are constantly breaking down, being shed, and replaced by the products of new cell division. There is a problem with the replication of chromosomes that takes place prior to cell division however, in that the enzymes that mediate it cannot fully replicate the ends of the chromosomes. Consequently, in order to protect us from losing genes with every division, our chromosomes are equipped with special end caps, called telomeres . Cell division does shorten these telomeres however, and this limits the number of times a cell can divide. Consequently, every cell division is a step toward ultimate doom. You might want to ask why the Intelligent Designer would pl...