How to Find a Habitable Planet

Reviews current and emerging techniques of indentifying Earth-like planets

why would they want to communicate with us? They might be so much ahead of us morally and technology whise. when they are technology whise then it might be entirely possible we have been scouted hundreds of years ago already, but they did it in a way we wouldnt notice it? They might think we would mess up theyr system and would do more harm then good or something.

I think we should first focus on figuring out how to beat lightspeed and figure out how gravity works and ****. Before we try to discover planets 20 million lightyears away.

a) please use a spell checker.

b) what does morality have to do with anything?

I think he's saying other cultures might frown upon our current activities of destroying the biosphere.

thank you

The Alcubierre drive thing seems to ignore the incredible distortions to time that would occur if you were able to generate gravity strong enough to sufficiently distort space like that. I'm not really sure how that would affect things, but the picture painted in the description you quoted is very disingenuous because it ignores this.

There's no reason that I'm aware of to think that wormholes exist. Right now, they're just things that can sort of exist in theory if you take some of our abstract theories far enough--that doesn't mean that they can exist in practice, and it certainly doesn't mean that they actually exist in our actual universe. If they did exist and if they did allow for spacelike movement, that would be extremely troubling.

The light traveling faster than the speed of light in certain circumstances thing has been around for a while. I've never quite gotten the explanation for why it doesn't violate causality, but people a lot smarter than me all agree that it doesn't, so I'm cool with that. It has something to do with the difference between phase velocities and group velocities and how it would be impossible to actually trasmit information through light traveling that fast. But, whatever, I don't really get it.

You have to realize how big of a deal it would be to violate causality. That would essentially make the fundamental question of science, "Given that things are like this now, what will they be like x seconds from now?", completely meaningless since there would be unmeasurable variables from the future. Hell, if our universe isn't causal, then it's possible that there's some being from the future who's just ****ing with us and making it look like the universe obeys all these physical laws we've been finding.

I think most physicists would consider worries like that to be non-starters. The first axiom of physics is essentially "Everything in our universe is predictable to some extent or another." If you drop causality, then we're living in a universe that from our perspective behaves completely arbitrarily.

I'm not particularly aware of this stuff, but from what I understand, it seems like there are basically a bunch of reports of people seeing weird things near military bases and military pilots seeing weird things.

One explanation of this is that there are aliens that like to visit our planet and are really interested in our military for some reason and our government is covering it up and the aliens are fairly subtle about it but not totally concealing themselves.

Another explanation is that there are in fact weird things near military bases because aerodynamics is really complicated, so the military just tests lots of different shapes to see how they fly/how radar bounces off of them. They don't talk about it much because they don't want other countries copying their cool flying shapes. We don't see many of them because almost all of them end up sucking. Military pilots are typically really smart, awesome people, but in flight they occasionally lose circulation to their brain and hallucinate in lots of cool trippy ways (google pilots and out of body experiences if you're interested), so them seeing some flashing lights and maybe occasionally a green man or two really isn't that interesting.

Nah.. I'm some guy.

I was a physics major in college for 3ish years until I switched to math. I was always fairly interested in this stuff and still occasionally read up on it on the interwebs.

I just think it's silly to speculate about the motivations of a completely different life-form. When people say that a dog "likes" something or "wants" something, they're already basically pretending that the dog is human. That works fairly well for dogs, and you can predict their behavior pretty well by basically just figuring they're a human brain with a sorta weird personality in some weird body. When we're talking about something from a completely different planet that evolved completely independently of us, I think that any such comparisons are ridiculous.

I don't think that's silly at all. It's silly to assume that their motivations are quite similar to ours though.

You're speaking in relative terms. To answer your question, "I don't know". But it might stand to reason that the level of intrigue we find with a primitive life form may be inversely proportional to how advanced we are.

yes i agree with everyone, Stephen Hawking is pretty dumb and has no idea what hes on about.

Surely thinking about it on such a small scale means youre missing his point?

I'd like to see that Hawking character try to buy gas in West Memphis.

Grunching

Humans have stared at a hill of ants a **** of a lot and have studied ants a **** of a lot, so even that example is dumb on reflection.

Given this can we trust him on physics?

Huge derail, but Warren Ellis is writing a comic book right now called supergod, and it's about mankind creating these super beings patterned after gods, and then falling prey to the fact that they don't think or act like us, and their motivations are completely different. Its a fun read if you like Ellis, and something interesting to think about.

Well, maybe they'll give the trees the power to make some kind of poisonous gas that drives us to suicide in some form of retaliation. Wow, wouldn't that make a horrible movie?

It might be that if we encounter alien "life" that is way more advanced than us, we'll notice that they seem to behave in some ways that seem to suggest a "desire" to stay alive. Life, if you try to chop it into little pieces and if it's a life form that doesn't survive when chopped into little pieces (unlike starfish, for example), it might run away or kill you or restrain you or whatever. Even that's not really a given, though. They might not care about self-preservation after they've reproduced or when they're off their home planet, or they might just never care, or they might not understand the concept of being chopped into little pieces or something. Who knows?

Speculating about whether they'd travel through space if they could, and if they did, if they'd come to earth to say hello just seems insane.

Say I come up to you with a cardboard box and tell you there's a living thing from earth inside there. Given that information, you'd have absolutely no clue how that thing will react when I open the box with you there. It might be a rabid dog that jumps out and bites you. It might be bacteria or a plant or fungus or a sponge or something that wouldn't even be aware of your existence. It might be a psychopathic human with a gun who shoots you. It might be a nymphomaniac that ****s you.

Now replace the fact that the thing came from earth with the fact that the living thing DIDN'T come from earth, but got here somehow. What the hell can you say about how that thing will respond to your presence?

It's totally possible. If it turns out there are giant green men who have a passion for disco on Europa, then it's just a matter of making the effort to take a peek. If there's even fairly basic life on Mars, we might go through the enormous effort of finding it soon. All depends on the funding that various programs get. If there are green disco lovers who happen to be pretty small or not in our solar system, then they might not be quite possible to find with our current technology. I personally believe that predicting what technology will look like in 10+ years is basically impossible, so I don't really think you can practically come up with a time-table for finding small green disco lovers on some distant planet.

There's also of course always the potential that somebody finds us first. Since we have no clue what's out there, we have absolutely no way of knowing how likely this is to happen, but it's perfectly possible that it'll happen this sunday around 7:32 PM GMT (you heard it hear first!).

Also our civilization's understanding of cosmology and space/time travel is only defined by our own understanding of math and physics.

Other life forms may have a completely different (and more advanced) understanding of cosmology than us.

We apply our own idea of math and physics to things but our math and physics probably sucks bigtime compared to what is possible.

Knowing that the living thing developed the means to reach us tells us a lot, and I think it's pretty fair to assume it has a level of curiosity that would lead it to observe us.

This is if it was traveling at a constant speed. The gravitational force of planets and suns can be used to slingshot spacecrafts to speeds nearing the speed of light, but the technology is probably still many years away.

But if life is abundant in the cosmos and you have seen a million humanoid variations already do you take all the time and effort to study our planet.

The best analogy I can make is that we have people who study ants in detail, but not people studying every ant colony on the planet.

Not saying I agree with this hypothesis, but it is reasonable.

In reality, things are much more complex and you have to start thinking about the Drake equation, Fermi paradox, "Great Silence" / "Great Filter", etc.

You don't think it's fair to assume that, on a fundamental level, conscious beings capable of interstellar travel and/or communication would be interested in lifeforms on alien planets (aka, us)?

We kind have already dove into that itt. Yes is we are 1 of 1000 planets that host the same types of organisms including ourself then its easy to skip over us in particular. When they found the first of those 1000 planets tho Im sure they had a team of scientists sitting there studying us just like we would.

Plus Noah put it more of in this box we have a mystery guest from another planet instead of an intelligent being that is capable of coming to us on its own will. It makes it so much more a broader scope of what that organism is.

My bad. I was sorta arguing two different points at the same time, and they're not quite the same thing. I was arguing both that I think there's really nothing to be said about whether they'd bother to come here in the first place (because we have no clue what life on other planets would or could look like), and that if something did come here we wouldn't really be able to think of it as something with "motivations" in the way we'd like to.

So, yes, I agree that if something came here, we'd be able to say something about it--Namely, that it's alive and it came here. It's possible that we might be able to assume some reason for it coming here.

I mean.. for all I know we could be visited by some dude that speaks English and tells us it came here because it likes watching rugby and then goes and watches rugby for a while. But I think it's more likely that we'll be visited by something that we're just completely unable to empathize with at all.

I think you meant no communication theorem

Just one idea on why a very technologically advanced civilization might not visit earth could be that their technology allows them to view us accurately from very far away and/or are able to simulate earth without them actually going to us.

A civilization millions of years more advanced then us will have technology that we can't even comprehend. It's not really right to compare them studying us with how we study ants. There may be way more alternatives/reasons for them not to visit.

Nah.. I meant the no cloning theorem: http://en.wikipedia.org/wiki/No-cloning_theorem .

I could be wrong, but I'm pretty sure the no cloning theorem is a theorem in the sense that it follows from the uncertainty principle, but the no communication theorem is basically just a deduced concept that goes something like "We keep seeing these things in quantum mechanics that at first glance seem to violate causality, but then it turns out that they're 'action' at a distance that can't be used to communicate so they don't count"?

Regardless, in the simple case of two quantumly entangled particles, the no communication theorem follows from the no cloning theorem. If Alice measures particle 1 and then Bob measures particle 2, Bob will always get a result that agrees with Alice's measurement. However, Bob has no way of knowing that his measurement only had one possible result. If he could clone the particle 1000 times and take measurements on it, then he could be fairly sure that that's the case, but the no cloning theorem says that you can't do that. So, that's what I meant.