It always boggles my mind when I hear someone say "I don't believe other civilizations are out there, because we haven't seen any.", Which as Neil deGrasse-Tyson said, it's the equivalent of taking a teaspoon from the ocean and concluding there aren't any fish, which is utterly ridiculous, to say the least,(reply>), @Caio Matheus Agreed, I think the "estimates for life developing and intelligent life developing" are just wild speculation. I haven't seen what studies Lex refers to so maybe there is some empiric evidence, but since we don't even know how life originates how is it possible to assign a probability that it will be able to originate? <br><br>And for "intelligent" life (defining intelligent as what most people understand it to be), as far as we know, we humans are the only data point.,(reply>), @Philosopherous I agree with you. Also there's the problem that we don't completely understand what is life. There's not even a consensus on how life originated in this planet. So much we need to learn. It's kind awesome if we think about it.,(reply>), @Caio Matheus I get what you're saying, and agree completely. My issue is when they believe there isn't anything out there because we haven't yet found anything. I don't expect them to know for sure, of course. But to believe we're the only ones simply because we haven't yet seen any "evidence", yet given the vastness of the universe, is a little silly imo. <br><br>As you stated, if we just took a tiny sample from the ocean, and looked at it with our naked eye, we'd see nothing. With proper tools we would conclude at least there's microbial life. With more advanced tools we'd detect fish DNA, etc.<br><br>I think it's possible we're being bombarded with alien signals right now, but can't detect them. Hell, if we sent a wireless video to ourselves just 100 years ago we couldn't detect it. What makes us think we could detect a signal from an alien civilization 1 million years more advanced than us? <br><br>For all we know we're like ants to some aliens. When's the last time you bothered to send a YouTube video to an ant? Or talk to them? An ant doesn't even know you exist. Hover your finger right over one before you smash it. It can't even perceive you. Without sounding too woo-woo, I think it's entirely possible there could be a higher dimensional alien right in front of your face this very second and you would never know it. As for aliens similarly as advanced as us: the tech simply isn't there to traverse such vast distances. We're ants looking for other ants, meanwhile there's YouTube videos passing right though us 24/7 undetected.,(reply>), @Mountain Fisher could it be that having the environment we do (of oxygen, nitrogen, etc) has actually barred us from discovering and utilizing certain chemical compounds? That if intelligent life existed within a different gas/liquid they might have access to things which we simply do not have access to due to our environment?<br><br>I mean, imagine if one thing that instantly binds with oxygen and is thus almost useless to us, actually is incredibly useful to them because they simply don't have oxygen in their atmosphere.,(reply>), I get your point but actually no, it's not the same thing. <br><br>Science requires empiric observation and experimentation. The conclusions we arrive will always be conclusions that we have a "reasonable" degree of certainty. <br><br>When we analyse a teaspoon of water, the only conclusion that is scientific is that there is no fish in this teaspoon of water, but as technologie progress we can maybe see what elements are in this teaspoon of water and arrive in the conclusion that certain elements in this teaspoon <b>might</b> indicate that fishs live in this ocean, and that analysis can be so trustworthy that we might as well say that fish live in the water. But until we don't see, hear or feel a fish in the water it's not scientific to say that there are fish in the water or that there aren't.<br><br>The thing is that a reasonable degree of certainty seems to work fine for most cases. There's no 100% certainty of anything. <br><br>Same thing with aliens. From a scientific standpoint saying that there are aliens is as wrong as saying that there are. We could find something that somewhat indicates that aliens exist, that's what scientists are trying to do. But maybe there is none, maybe we are alone in the universe.<br><br>Sorry if I came out a arrogant, but that's what I think doing science is. Please correct me if I'm wrong.