From “Where Is Everybody?” by Jim Al-Khalili:
“Of course, an alien planet being suitable for life is one thing, but the really big unknown is this: given the right conditions, how likely is it that life could evolve elsewhere? To answer is that we need to understand how life began on Earth. If we are indeed alone in the vastness of the cosmos, then we need to understand why we are so special. Why would the Universe be apparently so finely tuned for life to exist, yet harbour it in just one isolated corner?
One way of thinking about this is to ask yourself how come you exist? What were the chances that your parents would meet and produce you? Indeed, what were the chances of their parents meeting, and so on all the way back? We are each of us the culmination of a long and highly unlikely chain of events leading back to the origin of life itself. Break any one of the links in that chain and you would not be here to ask the question in the first place. Maybe our existence is really no more remarkable than the lottery winner contemplating his or her good fortune: had that sequence of numbers not come up, then someone else would have won and they would also reflect on the improbable odds of their win.
What life on Earth can tell us about alien existence elsewhere in the Galaxy is limited by the fact that we have a statistical sample of just one. Our own example tells us nothing about the likelihood of life elsewhere, or what it would look like if it did exist. Could there be advanced alien civilisations out there or would they only be in the form of simple, single-celled microbes? If we can’t begin to address that issue, how will we even know where to look?
Most profound of all of course is what it would mean for us if we did find them?”
From “What Are We Looking For?” by Nathalie Cabrol:
“At the crossroads of scientific disciplines, astrobiology uses advances in all fields to answer these questions: How does life begin and develop? Does life exist elsewhere in the Universe? What is life’s future on Earth and beyond?
These questions represent a puzzle of cosmic proportions, to which we are missing several key pieces. We do not have a clear definition of what life is. Could it have been seeded on Earth through panspermia (in which comets and asteroids transfer material between other bodies in the solar system on impact) and planetary exchange (the idea, for example, that there was some exchange of material between Mars and Earth at the time they were forming)? Or was it created on our planet through abiogenesis, a process by which life arises naturally from simple organic compounds and chemical processes? We also do not have a record of when – or in which environment – the transition from prebiotic chemistry to life took place. We don’t know whether life is a common universal occurrence or a fluke. But if we are to solve the puzzle, it makes sense to start with us.
The terrestrial biosphere we inhabit – even if it hasn’t provided the answers to the questions above – is a record of life’s evolution and adaptation driven by environmental and cosmic bottlenecks, extending over billions of years. Further away, we can see the solar system we belong to as a lab where, over eons, nature has created a diversity of environments surpassing in complexity anything we could develop in an experiment. Beyond the solar system, our most sophisticated instruments provide windows in space and time where we can catch a glimpse of how galaxies, stars and planets are formed. Last, but not least, the human mind can model, theorise, and generate limitless thought experiments.
With this in hand, we have started to build an understanding of what, where and how to search for life beyond our planet. By necessity, our vision is still anthropocentric: we are searching for life as we know it, and this approach is a logical one because it is always easier to start with what you know, when what we know of life is still so limited. As our knowledge broadens, hypotheses and models grow more complex, and the technology to test them becomes more sophisticated, which allows more discoveries to be made, and fundamental hypotheses and models to be refined. This is an iterative process. In that regard, the past few decades of exploration of the Earth’s most extreme environments, the solar system, and deep space have revolutionised our definition of habitability and life potential.”
From “It Came From Beyond The Silver Screen!” by Adam Rutherford:
They mostly get it wrong. Mostly. Film-makers have been infusing culture with their visions of aliens for more than a century, and almost all of them have been a lot like us. The Moon natives in the first cinematic trip into space, Georges Méliès’s La Voyage dans la Lune (1902), were Selenites, named after Selene, the Greek goddess of the Moon. They’re a bit like arthropods with bulbous heads and lobster claws, but mostly human – upright and bipedal. The next trip was when the 1919 adaptation of H. G. Wells’s The First Men in the Moon landed, which also had Selenites as the endogenous lunar men. Alas, all prints of the film are lost. In the few remaining stills from the shoot, the Selenites are also somewhat insectoid, but look disturbingly like the blue, globoid-headed, oval-bodied Igglepiggle from the bewildering otherworldly toddlers’ programme In the Night Garden. And so the tone was set for a century of aliens – humanoid, insect or insect-like humans are the mainstay of cinematic extraterrestrials. We turn to human-like forms either because of budgetary constraints or for reasons of anthropocentrism.
We lazily assume aliens will be a bit like us, because we do like thinking about ourselves. Star Trek and dozens of imitators have got away with simply gluing bits of lump onto human faces or painting them green to indicate their non-human status. The Star Wars Universe offers little but variations on humans. Budget didn’t seem to be much of a problem in James Cameron’s Avatar (2009), just a tiresome lack of imagination. ‘Let’s make them taller than us, and a bit cat-like, but sexy, and give them tails. They need to be primitive but wise. Oh, and make them blue too.’
We have a pretty good grasp of evolution these days, and our bounteous fossil record, now coupled with genetics, gives us a picture of how life evolved on Earth. There are plenty of mysteries remaining, but we know much about our nearest ancestors: the emergence of bipedalism and all the many factors by which we came to be who we are. To assume that on other worlds, evolution would deliver a species identical in physical stature is plain silly. We don’t really know why we became two-legged when almost all terrestrial animals are not, but we can hypothesise that it is an adaptation to a range of complex environmental conditions, primarily to equip a species for a life on the savanna rather than swinging in the trees, and an increased efficiency of movement. If the Earth ever got a reboot, and the story ran again from the beginning, with just a few variables altered we would not have come out like this. Even a seemingly unconnected matter like the tilt of the Earth’s axis has played a crucial role. That 23° tilt, which gives us our seasons, was caused by a rock the size of Mars colliding with the neonate Earth, and knocking off a block that would form the Moon. Imagine if the rock had missed; no tilt, no seasons, no Moon, no tides. This would have meant a different weather system, different climate changes over time, and an entirely different set of evolutionary ancestors. Imagine if that sixmile-wide asteroid hadn’t tumbled out of the Cretaceous sky into what is now the Gulf of Mexico and caused an extinction level event that wiped out the dinosaurs and so many other species, yet allowed our small mammal ancestors to thrive. Imagine that rock being half the size, and only half of the dinosaurs had been wiped out. Would we be as we are? The answer is almost certainly no. Our form is not inevitable – it’s mere cosmic happenstance.”
Aliens don't exist.
Well they don't exist and my evidence is no evidence of them existing, before you get all defensive like most Alien fanatics do, just hear me out..
For argument sake, lets say they DID exist, why is it that we always see a stupid looking photo with a dot on it and not the actual thing? We have great technology here on earth, they can't seem to capture one proper photo or video (100% of them are fake anyway)
Why is it that the Alien fanatics believe they do exist and try to believe so deeply? I am really curious about that question, so please do explain. For a second do you not think that this may be all some sort of "fun" the government created for you people so they draw attention away on what they are really trying to do?
I can go on and on! But it's just the same story over and over again with the fanatics.
For a time I use to believe too, honestly I did, and then this awesome feeling called common sense kicked my head so I understood what I had to.
Tell me, do you have proof of E.T's existing? Show me one.
No no they don't!
If aliens existed, wouldn't we have proof? Most pictures of UFOs are photoshopped and others are stars. We couldnt have seen aliens anyway, the government have never tracked a UFO entering earth's atmosphere!
Also, most alien sightings are caused by hallucinations and/or drug overdoses. Sorry to burst your bubble..
They aren't real
It's actually pretty obvious. You can see that there is no other life forms on any other planet or anywhere else. I mean aliens? Come on? Really? You gotta be kidding me. Aliens are just some made-up hoax or myth just to make people believe in something. It was made to scare little children like 4-5 year olds.
Aliens do not exist.
The most current estimates guess that there are 100,000,000,000 to 200,000,000,000 galaxies in the Universe, each of which has hundreds of billions of stars. As far as planets go, there are around 50,000,000,000 in our milky way galaxy alone.
The Kepler mission revealed 1,235 planet candidates, while 54 of them were orbiting their host star in the so-called Goldilocks zone.
So I'm going to do some rough math to try an determine how many planets in the universe may be habitable for life like earth is.
So if 54 out of 1,235 planets observed are in the habitable zone, this means that 4.3724696% of these planets are potentially habitable. What I'm going to do is calculate how many planets there are in the universe, and come up with an estimate to the total number of habitable planets there may be in the universe and draw a conclusion regarding the possibility of alien life existing based on those rough figures.
This galaxy has 50,000,000,000 planets, this means that roughly 218,6234,800 of the planets in the galaxy may be habitable for life. If we took 2,186,234,800 and multiplied it by 150,000,000,000 (between 100,000,000,000 and 200,000,000,000) to get a rough estimate of the total number of habitable planets in the universe, we would get 3.2793522e+20 planets in a Goldilocks zone.
If we look at our own solar system though, there are 3 planets in the Goldilocks zone but only 1 supports life that we know of. So if we took 3.2793522e+20 and divided it by 3 you would get 1.093117e+20 planets that are most likely habitable and have inhabitants based on all available evidence we can gather about the universe.
The chances of having 1.093117e+20 habitable planets, with 0 inhabitants is so close to 0 that I can't even think of a rational number to describe it at the point (even though I'm basing these numbers on what we see in our own galaxy and solar system along with the Keplar mission, and the numbers may not be 100% accurate when describing the whole universe, the picture I'm painting as a whole is still very accurate as a concept even if mathematical figures may not be totally correct).
This means that it is more likely that aliens exist somewhere in the universe, then not (even if only primitive life like bacteria exists, it is still alien life)
Aliens don't exist.
How do aliens have that kind of technology to get to us? How come they only come to us? I know we aren't the only ones in this galaxy..But it doesn't mean they are aliens. It could be anything pretty much. There is no proof. Some people claimed they have seen aliens, but its probably fake. Think about it .
Aliens Don't Exist
Aliens simply do not exist since there has not been any proof, apparently aliens have been seen in "pictures" but they are just simply a doll or either a piece of latex. I know for a fact that they don't exist. Has there been any proof? No so why don't you stop!
The distance to all other galaxies is so far, that the light takes millions, usually billions of years to reach us. With such large time frames involved, we cannot assume that extraterrestrials exist, and we cannot assume that life can exist. So am I to understand you are proposing that mankind will somehow break all known laws of physics to find these life forms on places we can't verify exist across distances we can never cover even if we had extra solar craft able to go one hundred thousand times the speed of light? If a tree falls in a forest with no one around to hear it, does it make a sound? The answer is no, it doesn't. The reason is, sound is made when we process it in our brains and make out a sound. For life to exist, it must be interpreted as life. If I burn a paper, it moves, it splits apart, creating more burning papers, and creates offspring of ash, all the while consuming air. But is it alive? Of course it isn't. Just the same, inanimate objects can do lifelike actions without being alive, as life can only be evaluated as life by other life. So you cannot assume that life exists just because there is an environment to support it. Therefore, unless you have some way to prove other forms of life, you cannot consider there to be life.
No They dont
Fact 1- Where are they?
Fact 2- Has anyone seen one
Fact 3- Why can't we find them
Fact 4- What do they look like?
Can you answer these? If you can you must be an alien yourself and to be honest that's humainly impossible and if you are you need to be taken to the secret service for examination. Thankyou and that's my point. Wanna argue? You're just wating your time because seriously I don't actually care what you think abnd I am not changing my answer. Bye
They do not exist.
Aliens do not exist. Just because there are millions of stars, planets etc. in space, that does not give the probability that there is life beyond earth, these planets are simple planets with no life. There is no evidence which suggests ET exists, although NASA has made attempts to find life in space, no life has been found and it never will be. From the beginning of civilization till now, not one evidence has been found. People will continue to believe in this fantasy and delusion regardless of any evidence being found because they are so thrilled by this belief and fascination.
No definitely not
God created the heavens and the earth, NOT aliens. DO quit thinking about and think of things that matter. Not old stories meant to entertain. We spend all this time debating things that really add no meaning to our lives. This debate has been going on for years with no end.