I’ve noticed that a number of articles and news stories have appeared in recent months about the possibility of life on other planets, including the physics behind the possibility and the attempts to find it. Here’s a compilation of the few things I’ve seen. First, a recent news report said that our earth-moon system is very stable. Our moon is unique in our solar system because it is so large in relation to the planet it orbits. This is good because the moon’s gravitational pull helps keep the Earth stable and keeps it from tilting over too often. That aided the development of life on Earth because it kept it from being wiped out by extremes of temperature over the surface. But the chances of a “twin” system like ours developing elsewhere is awfully small, so it may be an important factor in the development of life on another planet.
Second, the Search for Extraterrestrial Intelligence (SETI) hasn’t discovered any evidence of life on other planets in spite of listening for over 40 years. Someone recently made the rather arrogant presumption that SETI would find evidence of life out there within the next 20 years. Virtually 100 percent, they claim. Personally, I find it hard to imagine that a civilization with the intelligence to send a radio signal our way would be dumb enough to do it in the first place. Why would they want to? In twenty years? Get serious.
Third, scientists in China now claim that time travel is impossible. Everything, they say, has to obey Einstein’s laws and that makes it impossible to go back or forward in time. So, no one is going to visit us here on Earth by traveling in time. I always wondered why no one has ever been here from the future or the past. Now we have a good idea.
Fourth, the number of planets out there that are enough like Earth to allow the development of life on their surface seems to be very small. So far, scientists have discovered over a thousand planets (though no one has ever actually seen one), but none of them are capable of supporting life. Too hot or too cold or too noxious or too dead or too whatever, but life as we know it couldn’t get a foothold at all on any of those.
Fifth, a report on arXiv.org, says that life may not always develop on a planet even if the conditions are right. I’m not sure I understand this report fully, but the scientist’s conclusion was based on a statistical analysis of the chances of life developing. I blogged about this a few months ago, and I said that life must develop if the conditions were right and everything necessary was present. Apparently that may not be the case. But we have to keep in mind that a statistical analysis can be far outside the bounds of normal life experience, and sometimes it’s just plain unrealistic. For example, statistically, the average family in the USA may have, say, 2.3 children. Granted, three-tenths of a child isn’t going to happen, but this is a statistical analysis. Keep your shirt on, no one is slicing your next kid into parts.
Sixth, in order for life to develop, everything has to be present. Everything. Let’s postulate a planet somewhere, orbiting a nice star, at just the right distance so it’s not too hot, not too cold, has water and oxygen and carbon and nitrogen and other things. That’s what happened on Earth. But if one element is missing, the life that develops there may be so different from ours that we may not recognize it. Our life developed in response to the mix of chemicals that existed 4 billion years ago when things were just getting a foothold. A planet that has a different mix (and a different planet certainly will) will develop a different form of life, or life may not develop at all. To expect life to develop on another planet like ours here, or even be remotely similar, is, in my estimation, an absurdly unreasonable expectation.
All together, the chances for life out there to be recognizable by any of our explorers in the future that may land on another planet is pretty slim. I think we should get used to the idea that we are alone, or at least, in company so limited that we might as well be.