My friend Tim asked me this question:<\/p>\n
What do you think are the chances that we’ll detect (not necessarily physically encounter, but detect) life on another planet by the end of the century?<\/p><\/blockquote>\n
I think the odds are quite good, actually.<\/p>\n
First, here’s something that I’m pretty confident is true: Within a few decades, we will have figured out how to measure the chemical composition of the atmospheres of other planets.\u00a0 We’re moving fast in that direction right now, and while it’s a hard technical problem, I don’t see any show-stopping reasons why we can’t do it.\u00a0 Basically, you have to have telescopes with sharp enough resolution to see the planet separately from its star, and then you just do spectroscopy.<\/p>\n
I’ll be very surprised if we haven’t done this to hundreds and hundreds of planets within the next few decades.\u00a0 We’ll know what molecules are in the atmospheres of those planets.\u00a0 That means that we’ll detect life if <\/em>a couple of conditions are satisfied:<\/p>\n
\n
- Extraterrestrial life is not very rare.<\/li>\n
- Extraterrestrial life leaves identifiable chemical signatures in the atmospheres of host planets.<\/li>\n<\/ol>\n
That’s as much as I can say with confidence.\u00a0 From here on it’s guesswork.\u00a0 Regarding #2, one important question is what would count as an identifiable signature.\u00a0 People will naturally look at first for the chemicals that we find in our own atmosphere but that would not be there if there weren’t life.\u00a0 I think that plain old oxygen (O2<\/sub>) is one of the main ones here: the oxygen would all be in other forms such as CO2<\/sub> if it weren’t constantly replenished by biological processes.\u00a0 I have no idea whether extraterrestrial life will be based on similar chemistry to ours, so maybe O2<\/sub> won’t be the signature we’ll see.\u00a0 But it does seem likely to me that, if a planet has life on it, there’ll be molecules in its atmosphere that you wouldn’t expect to see in a dead planet, and once we get good at doing spectroscopy, we’ll find them if they’re there.\u00a0 So I’m not too worried about #2.<\/p>\n
#1 is the one nobody knows about.\u00a0 Is extraterrestrial life found on lots of planets, or is it a one-in-a-trillion shot?\u00a0 Here, you just have to make your best guess.\u00a0 Personally, I don’t think it’s likely to be incredibly rare, so once we’re mass-producing spectroscopy of other planets, we’ve got a good shot at finding it.\u00a0 But that claim is based on no data — it’s a Bayesian prior probability — so feel free to disbelieve me.<\/p>\n
I think this life is far more likely to be simple microbes than big intelligent things.\u00a0 I doubt we’ll be hearing messages from ET any time soon.\u00a0 That doesn’t mean that I think searches for intelligent life like SETI are a bad idea, though: they’re quite cheap compared to lots of scientific research, and the payoff if they succeed is so huge that I think it’s worth throwing a little bit of resources their way, despite the long odds.<\/p>\n","protected":false},"excerpt":{"rendered":"
My friend Tim asked me this question: What do you think are the chances that we’ll detect (not necessarily physically encounter, but detect) life on another planet by the end of the century? I think the odds are quite good, actually. First, here’s something that I’m pretty confident is true: Within a few decades, we … Continue reading Will we find extraterrestrial life?<\/span><\/a><\/p>\n","protected":false},"author":12,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-158","post","type-post","status-publish","format-standard","hentry","category-astronomy"],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/posts\/158","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/comments?post=158"}],"version-history":[{"count":0,"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/posts\/158\/revisions"}],"wp:attachment":[{"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/media?parent=158"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/categories?post=158"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.richmond.edu\/physicsbunn\/wp-json\/wp\/v2\/tags?post=158"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}