It's where times when. There could've been intelligent life 3 billion years ago, and we'd be none the wiser.
I suspect, for all practical purposes, we are alone. That is, we'll never find evidence of life (or complex life, at least) outside of Earth.
You don't need a paper to figure this out. Given the vastness of the universe, with its billions of not planets, but galaxies, the odds wouldn't have to be astonishingly low. They would have to be zero. Yet we know they aren't zero because we are here. Hence other life MUST be out there, statistically. It is essentially impossible for something to happen in the universe only once. What gets more interesting, then, is discussing HOW advanced other life might be. The Milky Way galaxy is towards the outward edge of the universe. We came into existence billions of years after other most other galaxies. So, other life on systems closer to the center of the universe has had billions of years head start on us. Where might humans be billions of years from now? Mind boggling to even think about it; given how fast we things are advancing currently, it is almost impossible to foresee where we might be just a thousand years from now, much less millions or billions.
If we do not self destruct for the next one thousand years, I am pretty sure people would be travelling the stars, but the chance of self extinction as a specie is very high.
For the same reason my daughter doesn't believe in Santa Claus, but during Christmas, she does. It benefits her.
People really seem to miss on understanding the vastness of both space and time and can't extend their imagination beyond the human-centric scale. While the odds of some kind of life existing within the billions of galaxies is statistically certain, the odds of existing at the same time are statistically impossible, the odds of perceiving each other are more impossible and the odds of contact are further limited by the complications of having mass since the laws of physics severely limit the speeds mass can travel. (And, physical existence is just as complex going the other way, down to the quantum scale where a grain of sand is as complex as galaxy) And yet we f*** up life on the one oasis we will ever know, dreaming that someone or something will offer us an alternative.
I don't think we are alone but I don't think it really matters. I am going to die long before we figure it out.
And there you have it... all that space and so little time. FWIW, God is definitely an alien so most people believe in aliens one way or another.
FWIW, when I was kid, I and some other kids saw a UFO. It looked exactly like the flying saucer you hear everyone describe. It hovered where it was it for a minute or so, then quickly accelerated up and out of sight. I called the police to report it, but they seemed pretty dismissive when I told them our parents weren't home. BUT they called back later. They had checked with the airport, and the airport apparently reported seeing something similar on their radar. Given people's stance on this, I realize that saying you saw a UFO usually moves you into the nutjob category...but I definitely saw it, and so did others with me, and the airport apparently confirmed it. So, the answer to are we alone? is No, and to whether or not intelligent life does exist out there is Yes.
No other object as been misidentified as a flying saucer more often than the planet Venus. Even former President of the United States of America, James Earl Carter Jr., thought he saw a UFO once but it's been proven he only saw the planet Venus. Venus was at its peak brilliance that night. You probably thought you saw something up in the sky other than Venus, but I assure you, it was Venus.
As a scientist, specifically a computational chemist, I take a little offense from this. The question of whether or not we're alone in the universe cannot be answered just by a simple conjecture based upon what happened with us and Earth. As far as we know, in the observable universe there are a finite number of stars, hence a finite number of chances for life. If the probability for life is scarcer still than your chances, then it's still highly unlikely that you'll get life outside of Earth. That's why my colleagues from Astrobiology actually study the conditions for which life can arise. It's not just a simple academic practice, the facts matter. My personal take on it is that the models we have now are far from conclusive. I took one course of astrobiology (again, it's not my area of expertise) which I dropped, admittedly, because I took an alternative course closer to my area. It has been made a point that the models have been incredibly volatile. Since the original equation, we've had to append so many more conditions that have dramatically shrunk the possibility of life outside of earth. So that and the fact we can't really check it anyway, at the moment, makes it feel really 'soft' for me at the moment. Anyway, the general takeaway from all this is that, 'is there life elsewhere in the universe'? Spoiler Maybe.
We have only know life by our definition of life on Earth. And based our (very narrow) definition, we search the universe for "similar" Earth, and I believe we now have much more information that there are many "similar" Earth out there. The chance of alien life is getting higher and higher as we see more. If our definition is wrong, and we have to consider it can very well be given that we only know a tiny little bit (Earth life), there may be trillions of alien life forms and we won't ever know just because of the vastness of the universe and how extremely small and insignificant we play in that vastness.
I disagree. When you consider the essentially unimaginable vastness of the universe, and the fact that we are, in fact, here, the question is already answered. Trying to apply science to it is understandable, but the factors included are unknowns themselves, thereby applying a false sense of specificity to the attempt. As we have not yet discovered any life outside of earth, we have absolutely no idea what forms it might take, what it might need to exist, etc. So applying any probably to any of that is pure guesswork anyway. It therefore isn't a computational question, as we don't have the data to make the computations. It is more one of simple common sense, and a knowledge of probabilities. AT the very least, the assumption would need to be that life exists elsewhere until it can be conclusively shown this isn't the case. . This is where the essentially infinite size of the universe becomes important. If the probability for life were that low, WE wouldn't exist. We can't, in fact, study that, as all we have is evidence from one microsystem...ours. We have no idea what other forms of life might be, or what their requirements would be. Life evolved here taking advantage of the environment here. Life elsewhere could well evolve on completely different parameters. Consider oxygen. All life on earth requires oxygen. Does that mean that all life anywhere requires oxygen? No. They have to be. We don't have to data to make definitive determinations of the probabilities involved. It would be a fascinating topic to study. I might even look into some classes, just for fun. How can we append 'conditions' when we have absolutely no idea, at all, what life outside of earth might look like or require? I tend to believe, as stated in Jurassic Park, that 'life finds a way'. Every assumption we make around life is built around life on Earth, which, by definition, does not apply to the question of life outside of Earth. This fact seems to be forgotten in the attempt to quantify this equation. And so it will stay until we have more data...ie, actually find life elsewhere. Until then, simply the fact that we exist, and the vastness of the universe, essentially dictates that the answer must be that other life exists. Only our own hubris prevents us from accepting this basic premise.
