What does everyone think about aliens?

Nature Talk
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I have been thinking about extraterrestrial life recently, and was wondering about what y’all think of it all. Do aliens exist, or are they just another piece of nonsense on this lonely planet? I personally think they should be, in some form, real. This is why I think that:

(a) This universe is HUGE. The probability of other life somewhere is incredible.
(b) There are plenty of Earth-like planets, and as we can see from examples such as hydrothermal vents and volcanoes, life can survive some pretty awful conditions.
(c) OK, we don’t see any aliens, but remember, what we see through huge telescopes actually happened centuries ago. Maybe it started being noticeable only recently, much like humanity.

What do you think?

P.S. I hope this is not too off-topic, since aliens are a form of nature.

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There’s probably life in other parts of the Universe, but since it originated and evolved separately from life on Earth, it is likely different, for the most part, from life on our planet. But perhaps it has some features in common with the life we know, since we have observed that some traits, such as bivalved shells in mollusks and brachiopods, have evolved in separate lineages and so might also have done so on other planets or on distant moons.

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Whether we find extraterrestrial microbes or actual little gray men, it will be interesting to see what the taxonomists do with them.

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To answer the question seriously, though, I have not the slightest doubt in my mind that Life exists in the infinite vastness of space… it would be inconceivable to imagine that it doesn’t. I would guess that it will take a form that might be unrecognizable to us… look at how different a slug is from a dog is from a maple tree, all of which exist on the same planet and (theoretically, at least) evolved from same ancestors… and imagine how different something that exists independent of those things would be. Probably impossible to imagine.

Now, the real question is… will we ever discover or see it for ourselves? I feel that is much more unlikely. It may sound pessimistic, but the very scale of the Universe that makes Life inevitable also makes finding it rather difficult. But… here’s hoping!

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I think, on first glance, life on another planet will look surprisingly similar.
That is because functional constraints are largely universal.
On second glance, the evolutionary history of these organisms will likely mean that there will be totally different approaches to the same structures (historic constraints). Think of how insect wings are different from bird wings, for example.

Personally, I think it is likely that the less an organism is influenced by other organisms, the more similar it will be to its “equivalent” on earth. The structures evolved due to some interaction with another specific species will probably be the most unfamiliar to us.

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Personally, I doubt that life exists on other planets. I think Earth is a special place.
That doesn’t stop me from imagining what alien life could be like.

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Mainly, I think that sci-fi writers tend to be biased toward bilaterally symmetrical forms. Who says intelligent life has to be bilaterally symmetrical or even capitate?

Picture this: a being shaped like five rays, no one of which is the “front” or “back.” It can walk equally well in any direction on a myriad of suction cup-like feet. Its mouth is on the underside at the point where the rays converge; the feet double as hands carrying bits of food to the mouth. You stand eye-to-eye with it – it has a single eyeball at the end of each ray, level with your eyes. Its intelligent brain is ring-shaped, also at the point where the rays converge.

On another planet, picture this: a being where each type of body cell – digestive cells, oxygen transport cells, reproductive cells, nerve/brain cells, etc. – is diffused throughout its body, which therefore does not need to be a particular shape. Its intelligence is also diffused throughout its body because of the diffused nerve/brain cells. This means that it cannot be slain in the usual way, because there are no vital organs in the sense that we are familiar with.

As many of you recognized, these fictional extraterrestrial intelligences are based on our planet’s starfish and sponges, respectively. Who’s to say that these body forms could not evolve to the level of intelligence? Some experiments with slime molds – giant protozoans – suggest that they have some characteristics of intelligence. Yet you don’t tend to see this in sci-fi stories.

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I love this idea! It reminds me of a siphonophore.

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I am sure that life equivalent to bacteria and archaea exists on other planets that have liquid water and fairly stable histories going back a few billion years. I expect those organisms to be based on carbon, as we are.

We’re most interested in multicelluar organisms. (I expect large organisms to be based on cells, due to limitations of transporting chemicals.) Possible? Yes. Probable? That’s unclear. Maybe. There are some serious bottlenecks life has to pass through to get to some equivalent of eukaryotic cells (capable of producing more chemical energy than they need just for survival) and then to get to a multicellular state.

On planets that have multicellular organisms, I would expect we would see many life forms that would seem familiar. Fish-like shapes for moving through water, for example. Flat surfaces broken into smaller units (maybe strips) for absorbing light energy. Many organisms would be wildly different, though.

What about intelligent life that we could recognize as such? Given that the universe is more than 13 billion years old and that there are more planets than I can imagine, I expect that there have been and are intelligent life forms elsewhere. Given the immense distances between planets and galaxies, I seriously doubt we’ll ever know.

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I think bilateralism might almost be a prerequisite for intelligence. (Though, being bilateral myself, I might be biased :P)
To me it seems like radiate organisms don’t really benefit from a central nervous system (which I’ll just call “brain” for simplicity) or at least not from the intermediary forms that would have to exist prior.
Bilateral organisms do, though. Being bilateral with pairs of sensory organs allows for triangulation, which requires more processing, therefore a higher neuron-density near the sensory organs (usually at the front) is an advantage. Over time, this structure can evolve into a brain and allow cephalisation to take place.
With head and brain it is far more straight-forward to evolve “more intelligence” than from the neuron-layout radiate animals tend to have.

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Earth is definitely special, regardless of wether or not aliens exist.

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Organisms that move quickly evolve a concentration of sensory organs at the front end because that’s the part of its body that first encounters dangers, foods, etc. With all those sense organs at the front end, nerves tend to be concentrated there, too – a brain. Also, the organism becomes bilaterally symmetrical. I think these things go together.

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I believe aliens do exist, but not as little green men. Out of all the impossible, terrifying, weird and wonderful creatures an extraterrestrial could look like, it converges on a human-like form?

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Astrobiology is a super interesting field, I’m glad more people are starting to ponder about it! Part of me hopes that we are indeed the only life forms in the universe. This would mean that humanity exists in a giant sandbox, free to explore, without threat of meeting hostile aliens!

But, humans are humans, and instead of fighting against hostile aliens, we would start fighting against ourselves. No difference, really.

Perhaps over billions of years, as humanity spreads throughout space, we would start to diverge and evolve seperately in different areas? We might become alien to ourselves (if that makes any sense?) This is an idea that was explored by Turkish science-fiction author C. M. Kosemen, in his work titled All Tomorrows. Naturally, I imagine other species would also start to diverge and evolve as we bring them along with us.

And then there’s the other part of me that would delight at discovering alien life forms and ecosystems. One can only imagine the excitement, and perhaps complete rethinking and re-ordering of the fields of biology and taxonomy that would arise from such discoveries. It’s incredible how we know so little in the grand scheme of things!

Maybe there’s bizarre multicellular cold-tolerant organisms thriving in the oceans underneath the icy crust of moons like Europa and Enceladus here in our own solar system. Or maybe little single-celled things hanging in those far-off underwater vents on said moons! Maybe there’s sulfur-dioxide based life floating in Venus’s upper atmosphere where conditions are similar to that of Earth! Weird bacteria-like things hiding in the dark watery caves deep beneath Mars’ barren surface? There is evidence that both Mars and Venus were once warm watery worlds, perfect for life!

I got a little carried away writing that, but, this post really draws out my combined love for astronomy and biology all at once! Thanks for sharing this!

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There are too many possibilities to not be the only planet that has life. There are for sure planets with the same distance from their parent star which means those planets will have similar climates to us which enables life to exist on the planets. However, there may be life existence on planets that are at shorter or longer distances to their parent star than our planet.

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I’ve not been positive that humans are not the aliens here.

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Considering the tremendous genetic and biochemical similarity of humans to other organisms on this planet, the hypothesis that humans did not evolve here (are alien to earth) cannot be supported.

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In my personal opinion they don’t exist. The biggest proof for me is that despite the fact that we have organisms living in pretty extreme conditions we have not found a single shred of evidence of extraterrestrial life in any of the other planet in our solar system and seeing how for us to be alive in this planet our earth had to have near perfect condition, it seems extremely unlikely that there is any other life out there.

There was an article recently stating how quickly samples they’ve brought in from outer space (either mars,moon or asteroids) have become contaminanted by bacteria. Even though those samples have been carefully stored and transported, it didn’t stop bacteria from colonizing them. And yet there is no evidence of any alien bacteria from Mars or the moon or the asteroid we collected a sample from.

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That’s no proof at all. It only means that life, or the conditions necessary for life, are not super abundant. It’s a logical fallacy to assume that rules out life in other places than Earth. Absence of evidence is not evidence of absence.

Even within our own solar system, we can’t rule out life outside of Earth. It’s now pretty clear that early Mars had conditions that terrestrial life could have survived in. We still don’t know enough to say that life never inhabited Mars. Jupiter’s moon Europa is strongly suspected of having an ocean of liquid water under a layer of surface ice. Again, there seem to be conditions that terrestrial life could thrive in.

So in our one little solar system alone, there are/were at least three independent places life could exist. And, that’s just the kind of we find on Earth. It’s hard to imagine what conditions non-terrestrial life might be able to inhabit.

Out of the three places we’ve found so far that life could exist, we know one of them has life for sure, and don’t know yet whether life was/is in the other two. While we can’t really extrapolate from such a small sample, it’s far from telling us that life elsewhere doesn’t exist. In fact, the hints are completely the opposite.

Look at the probabilities. So far we have found about 5,000 exoplanets. None of them seem much like Earth, but it has shown us that planets are everywhere. So far our search methods have favored finding those planets that are large and close to their star, so that’s what we’ve predominantly found. The abundance of planets suggests that rocky Earth-size planets the right distance from their star to have liquid water must certainly be out there.

Even if an Earth-like planet only happens in 1 out of 10,000 star systems, that would mean there are 10M Earth-like planets in our galaxy alone. That’s a lot of possibilities for life to evolve. The numbers are literally astronomical. However, even with these numbers, you wouldn’t expect to find an Earth by looking at 5,000 planets that are mostly large and near their star. We simply don’t have enough data to rule anything out.

Another way to look at the probabilities is by considering habitable conditions. There are at least three in our star system. Let’s say there is one on average in every 10 star systems, that’s still 10G worlds with habitable places in our galaxy. And that’s just for the kind of life we know about.

Habitable places are clearly out there, even abundant. The real question is how likely the initial “spark” is that starts life. We only know of one instance where that happened, but even that shows us that’s it’s probably not so unusual. Earth is about 4.5G years old, and it seems life started only 1G year in, shortly after the planet was no longer a glob of molten rock getting regularly bombarded by more rocks and large snowballs. Since life happened quickly once conditions allowed it, it suggests that it’s not so unlikely.

So in summary, at this point we can only say we don’t know whether extra-terrestrial life exists. But, the data we do have certainly doesn’t rule it out, and even suggests that there should be “many” instances in our own galaxy. Then consider that there are about 100G other galaxies out there.

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Well we started searching only recently.

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