# How many planets in our galaxy harbor intelligent life? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [July 30, 2015, 2:37pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578 "2015-07-30T14:37:21Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [July 30, 2015, 2:37pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/1 "2015-07-30T14:37:21Z")
Just curious what most think on the matter, using their best guess. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [July 30, 2015, 2:45pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/2 "2015-07-30T14:45:06Z")
Insufficient data for a meaningful answer. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [July 30, 2015, 2:45pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/3 "2015-07-30T14:45:29Z")
You forgot the 0 option. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [July 30, 2015, 2:49pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/4 "2015-07-30T14:49:54Z")
> [@Johnny\_L.A](#): > > Insufficient data for a meaningful answer. Of course, that’s true. But most here are familiar with the Drake Equation, and I’m just curious how people’s guesses at the variables shake out. > [@TriPolar](#): > > You forgot the 0 option. 😉 I was tempted. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [July 30, 2015, 2:50pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/5 "2015-07-30T14:50:21Z")
I believe the universe is teeming with life . . . and given enough time, much of it will evolve intelligence. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [July 30, 2015, 2:52pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/6 "2015-07-30T14:52:31Z")
> [@panache45](#): > > I believe the universe is teeming with life . . . and given enough time, much of it will evolve intelligence. I believe there’s billions of planets with life, but maybe only a hundred or so that will evolve human-like intelligence or greater. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [July 30, 2015, 2:55pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/7 "2015-07-30T14:55:37Z")
> [@cmyk](#): > > Of course, that’s true. But most here are familiar with the Drake Equation, and I’m just curious how people’s guesses at the variables shake out. The Drake Equation is interesting, but essentially meaningless. There is no way to know even approximate values of four out of the seven of them. Of the remaining three, we’re only now beginning to accumulate data for them. So my guess is a number between one and _n_. ---
**Author:** ![Blaster\_Master](https://avatars.discourse-cdn.com/v4/letter/b/cab0a1/32.png) [@Blaster\_Master](https://boards.straightdope.com/u/Blaster_Master)\ **Post date:** [July 30, 2015, 3:02pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/8 "2015-07-30T15:02:58Z")
At best, it’s a handful, I have severe doubts that it could be on the order of dozens or hundreds. Yes, we’re probably looking at billions of planets that are in the habitable zone as far as we can tell, but we’re not able to determine how many are really Earth-like, as the smallest planet we’ve found is still a few times larger. While it’s possible that life could form in dissimilar conditions to Earth, I think it’s unlikely that life would evolve as anything other than organic, and it would need to be on a stable enough planet to give it sufficient time to evolve. So, sure, I think it’s quite likely that life exists in a lot of places, though we’re still not sure how difficult or easy it is for simple life to spring up. But more than that, depending on how we define intelligent life, we really only have one example, humans and possibly some very closely related, now extinct, hominid species. And even for us to evolve, we’ve had several mass extinctions and other probably quite rare events happen. As I think the extinction events show pretty well, evolution doesn’t necessarily create intelligence, as life was plentiful in previous epochs for millions of years without any particularly intelligent life evolving. So, I think it’s quite possible that even if there’s planets out there with millions or even billions of years of a head start over Earth, they may still never evolve intelligent life. So even if there are billions of planets capable of supporting life and a decent fraction of those do, I think intelligent life is probably a much more rare event as it necessitates an environment were the added intelligence is worth the large increase in resources to support it. Beyond that, look at the overwhelming portion of human history, we were intelligent, using tools, developed language, created societies, but it’s only in the last hundred years or so that we’ve actually done anything detectable off-planet. What if other intelligent species develop but die off from disease or natural disaster before they can develop sufficiently advanced technology? What if they don’t have the same access to resources that we do, or they evolve in a way that they’re intelligent but not particularly able to use tools, like a dolphin? Or what if they start to develop advanced technology and then wipe themselves out with it or perhaps choose to pursue other endeavors like arts or philosophy? Or what if their intelligence is just so fundamentally different from ours that we couldn’t meaningfully recognize them as intelligence or, if we could, we couldn’t meaningfully communicate with them? ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [July 30, 2015, 3:04pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/9 "2015-07-30T15:04:57Z")
> [@Johnny\_L.A](#): > > The Drake Equation is interesting, but essentially meaningless. There is no way to know even approximate values of four out of the seven of them. Of the remaining three, we’re only now beginning to accumulate data for them. > > So my guess is a number between one and _n_. That’s the logical answer. But, this isn’t necessarily about being right or wrong, because of course we can’t know. Only what’s your _feeling_ on intelligent life out there? We do have insufficient data on life elsewhere, but not necessarily zero data. We’ve explored all the major planets, most of the major moons, etc. in our own system, and while we think some are good candidates, there’s been no evidence of life yet. And in a solar system that has one planet bursting with life. That’s a bit discouraging, dwelling on that alone. ---
**Author:** ![Frank](https://avatars.discourse-cdn.com/v4/letter/f/3d9bf3/32.png) [@Frank](https://boards.straightdope.com/u/Frank)\ **Post date:** [July 30, 2015, 3:13pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/10 "2015-07-30T15:13:22Z")
I can’t answer the question. I certainly think that there is other intelligent life besides us. There’s just no way to even guess how common it might be based on our limited sample size. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [July 30, 2015, 3:18pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/11 "2015-07-30T15:18:29Z")
> [@Blaster\_Master](#): > > At best, it’s a handful, I have severe doubts that it could be on the order of dozens or hundreds. Yes, we’re probably looking at billions of planets that are in the habitable zone as far as we can tell, but we’re not able to determine how many are really Earth-like, as the smallest planet we’ve found is still a few times larger. While it’s possible that life could form in dissimilar conditions to Earth, I think it’s unlikely that life would evolve as anything other than organic, and it would need to be on a stable enough planet to give it sufficient time to evolve. > > So, sure, I think it’s quite likely that life exists in a lot of places, though we’re still not sure how difficult or easy it is for simple life to spring up. But more than that, depending on how we define intelligent life, we really only have one example, humans and possibly some very closely related, now extinct, hominid species. And even for us to evolve, we’ve had several mass extinctions and other probably quite rare events happen. As I think the extinction events show pretty well, evolution doesn’t necessarily create intelligence, as life was plentiful in previous epochs for millions of years without any particularly intelligent life evolving. So, I think it’s quite possible that even if there’s planets out there with millions or even billions of years of a head start over Earth, they may still never evolve intelligent life. So even if there are billions of planets capable of supporting life and a decent fraction of those do, I think intelligent life is probably a much more rare event as it necessitates an environment were the added intelligence is worth the large increase in resources to support it. > > Beyond that, look at the overwhelming portion of human history, we were intelligent, using tools, developed language, created societies, but it’s only in the last hundred years or so that we’ve actually done anything detectable off-planet. What if other intelligent species develop but die off from disease or natural disaster before they can develop sufficiently advanced technology? What if they don’t have the same access to resources that we do, or they evolve in a way that they’re intelligent but not particularly able to use tools, like a dolphin? Or what if they start to develop advanced technology and then wipe themselves out with it or perhaps choose to pursue other endeavors like arts or philosophy? Or what if their intelligence is just so fundamentally different from ours that we couldn’t meaningfully recognize them as intelligence or, if we could, we couldn’t meaningfully communicate with them? Great post. But to address some of your points in the last paragraph, yes, intelligence is a tricky thing to define, and what I’m talking about is an intelligence on par or greater than ours, or at least our more recent hominid ancestors. And yes, there might be intelligences that are so wholly alien, we wouldn’t recognize it as such, let alone communicate with it, but if it’s self-aware and employs some aspect of logic, it still counts. As for intelligent life that had evolved, but went extinct whether by natural or technological catastrophe, I’d say you can count that. I’m more interested in how many intelligent beings have existed (or still do), rather than how many might be out there at this particular moment. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [July 30, 2015, 3:19pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/12 "2015-07-30T15:19:41Z")
> [@Frank](#): > > I can’t answer the question. I certainly think that there is other intelligent life besides us. There’s just no way to even guess how common it might be based on our limited sample size. Don’t answer. _Guess._ ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [July 30, 2015, 3:19pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/13 "2015-07-30T15:19:59Z")
I guessed high because I like to think that life is more robust than we give it credit for. ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [July 30, 2015, 3:23pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/14 "2015-07-30T15:23:47Z")
Do you mean right now? (After all, Earth didn’t have intelligent life for most of its history.) And, given relativity, what does “right now” mean in this context? Anyway, this is something I’m completely agnostic about. I think there _could be_ anywhere from a few to very many other planets with intelligent life, but I also find it entirely credible that we’re the only one. And if I had to pick something, I’d lean toward this response, if only because I suspect there may be an element of wishful thinking in those in those who conclude there _is_ intelligent life elsewhere. But I don’t expect the question to be resolved in my lifetime, so to me, it totally doesn’t matter one way or the other. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [July 30, 2015, 3:26pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/15 "2015-07-30T15:26:34Z")
> [@mlees](#): > > I guessed high because I like to think that life is more robust than we give it credit for. Yeh. I guessed about an order of magnitude higher (I guessed 100) than what I’d expect. Ten on the low side, 100 on the high. Anything greater would blow my mind. Which is another way to approach the poll: If we were shown a completely comprehensive survey of the entire galaxy, past and present, of which planets had intelligent life, at what number would you think, “yeh, that’s kinda what I expected.”\* \*Despite finding the truth, no matter the number would be in and of itself, amazing/shocking. ---
**Author:** ![Chimera](https://avatars.discourse-cdn.com/v4/letter/c/8e8cbc/32.png) [@Chimera](https://boards.straightdope.com/u/Chimera)\ **Post date:** [July 30, 2015, 3:27pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/16 "2015-07-30T15:27:49Z")
Ok, mine was a joke answer: Just 12. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [July 30, 2015, 3:29pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/17 "2015-07-30T15:29:55Z")
> [@Thudlow\_Boink](#): > > Do you mean right now? (After all, Earth didn’t have intelligent life for most of its history.) And, given relativity, what does “right now” mean in this context? > Anyway, this is something I’m completely agnostic about. I think there _could be_ anywhere from a few to very many other planets with intelligent life, but I also find it entirely credible that we’re the only one. And if I had to pick something, I’d lean toward this response, if only because I suspect there may be an element of wishful thinking in those in those who conclude there _is_ intelligent life elsewhere. But I don’t expect the question to be resolved in my lifetime, so to me, it totally doesn’t matter one way or the other. Past and present. And agreed that it could be we’re the only ones in the entire universe, even. ---
**Author:** ![Renee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/renee/32/287_2.png) [@Renee](https://boards.straightdope.com/u/Renee)\ **Post date:** [July 30, 2015, 3:57pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/18 "2015-07-30T15:57:07Z")
Apparently, there are 100-400 billion stars in the milky way. The mind boggles. I guessed thousands have intelligent life, but I’m defining intelligence pretty broadly, maybe dog level and up. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [July 30, 2015, 4:03pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/19 "2015-07-30T16:03:35Z")
> [@Thudlow\_Boink](#): > > … And, given relativity, what does “right now” mean in this context? **Technical answer:** Well, it’s relative. 😉 BUT, the galaxy is about 100,000 LY across, so if I assume correctly, “right now” would be somewhere within ~100,000 years at max, depending on distances from one another. However, the farther something is from you, the more you’re seeing their past. So since past & present counts, it’s sort of moot. **Practical answer:** If a planet is 30,000 LYs away, you’re allowing for 30,000 more years of evolution from what we could detect from here. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [July 30, 2015, 4:12pm UTC](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578/20 "2015-07-30T16:12:31Z")
Missed the edit: but to put 100,000 years into perspective, we were Neanderthals that long ago. So, even at the max “present”, we’d still count as intelligent. It took _tens of millions_ of years to evolve into an intelligent, tech-weilding creature from what we’d consider something with the intelligence of a chimp. [Next page](https://boards.straightdope.com/t/how-many-planets-in-our-galaxy-harbor-intelligent-life/726578.md?page=2)