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Why do we assume aliens (if they exist) are roughly the same size and shape as humans?

9 Answers
Why do human beings that believe aliens exist assume they have two eyes, two arms, two legs, etc. If they do exist why would they necessarily be the same size let alone visible to the naked eye - ie smaller or larger and why would they arrive in a vehical at all let alone one made of what some would describe as essentially metal in the form of a propelled craft?
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Hello Foxgru62 and welcome to Mybestanswer

My opinion is that we assume that aliens look similar to us because we are inevitably subjective beings, by definition. We are conditioned from the day we are born to apply any "standard" context of every day logic or common-sense, which helps us survive in our normal environment, to any type of unknown concept. It's a difficult way of thinking to break free from. That's what makes forgein concepts like the odd behaviors of particles at the quantum level and what "caused" the Big Bang to occur to be so difficult to even begin to comprehend.

Who's to say what an alien is defined as anyway? We have a difficult enough time trying to define life here on earth with a single all encompassing definition! We could very easily be surrounded by some forms of life that we have no idea are even living beings. Is there even a discrete line between a living beings and other objects?

Let me ask you this; is a star an alien form of life? One set of criteria, which I personally disagree with, but is nonetheless rather mainstream science, is that there are seven basic criteria necessary for something to be called a living. For instance it must have the ability to undergo some type of internal metabolism. metabolism is merely a set of reactions that convert food to energy and energy to work as needed. A star, or more specifically the Sun has a internal metabolism it uses the energy of which to maintain it's order as a single entity. To be alive, we must produce waste products that are removed by some means. The sun has plenty of waste products it releases including, but not limited to heat and light! Life must have internal order of some type, like cells which have smaller pieces (organelles), and make up part of larger units of order, like tissues and organs. The sun has elements in it's core layered as separate and rather discrete units, each composed of a particular element. The atomic elements can be broken down into subatomic particles, a lower level of order. These internal layer can be said to be part of a whole sun including the outer photons that are slowly escaping and the solar flares, etc.

There are basically ways to describe all seven of the qualities, even reproduction, in several ways, however the most obvious is the very way with which many scientists think that stars are "born". A former star that explodes into a supernova provide all the material that is necessary to "grow" one or more new stars. Closer to asexual reproduction, but no matter. And nothing prohibits two or more such events originating from separate stars to contribute to the newly growing star that results. But just to be clear, these rules are considered bendable anyway! Presently viruses are considered living even though they cannot reproduce without a symbiotic relationship with a living host cell. There has been debate for years , but it's generally accepted that they are living by most modern thinking. So even if the star did have a problem fulfilling one or two of the seven requirements we can't say it NOT living, but deem a virus living!

So I have no predefined notions of what alien life would look like, or be made of, or even at what level of magnitude they would be compared to our size! we may one day discover electrons are living beings, and/or galaxies.

We're quick to call anything between the order of cells and organisms, inclusively, "alive", but we expect it to suddenly terminate at these borders for some reason. What about the more obvious extensions like a ant colony or a bee hive, that act almost like a single organism! So why are households and communities, towns and counties, states and countries not levels of organization of a living being. Some people have come to this conclusion, can sort of generally consider the Earth a living planet, or biosphere. But again, as my star example points out, there's no reason to assume there is any upper limit, is there? Planets are ordered into solar systems, along with stars (something more like an organ made of several types of living tissue). Then theirs star clusters and of course the obvious galaxies. Beyond that it's hard to be assured of the next higher level of organization, since we can't see very much of the whole universe, but at minimum the universe itself is a higher order of life. Scientist have many very we explained theories of different type of "multiverses" that they expect to exist (I admit this is purely speculative), but the next order may be the collection of universes, and beyond that we've yet to realistically even guess, but there may be no end for all we know.

The same can be said for getting smaller and smaller in a cells order of organization. So it stands to reason that we may not be so special after all. Just another gear in the machine! That's not a bad thing, but it's worthy of much closer examination, or so it is my opinion. This means the question of finding alien life becomes much more blurry,but much more promising too! It may be anywhere and everywhere, just not recognized as such. Like we consider the "organism" level a living being, there would necessarily be other living beings "out there". But their composition, behaviors, appearance, or whatever ever other qualities you might want to insert here, is in no way constrained to those of Earthlings. Life has what I consider a more fundamental quality of response or adaptation to changes they experience (external or internal) So the environment would be a critical factor in determine what life was reasonably expected to conform to, thus making up their composition.

Another key concept to life, as I personally believe it to be, is that entropy, or the tendency for particles to become less ordered as time progresses, is "locally" held constant for the most part. We don't fall apart, or atomize and dissipate into diffuse molecules or atoms. Why? Because we manage to maintain the rate of increasing disorder of the total sum of all the particles in the universe, buy making some other portion of the universe become disordered to a higher degree (enough to make up for our ordered composition). How do we do this? We gather energy sources from the environment, while plants consume photons as energy, we consume molecules that can be converted to energy by cellular respiration (i.e. we eat and we breath to offset the order we maintain). That, I believe is a more fundamental property that defines life. Again entities such as stars qualify just fine by this standard too!

So we should have no reasonable expectation to know what to even look for when scanning the skies for traces of life on other planets. Just look at the diversity in the life forms we know to exist around us! Bacteria with silicon based-DNA has been found relatively recently in the hottest and most acidic of pools of water, where life was though impossible to be found in (that was in Yellowstone park in the US I believe). Paramecium are single-celled protozoans that appear to have the ability to "learn", although they have not a single neuron! So similar concepts can be translated to different levels of organization, since this must be some sort of a series of chemical reactions, not groups of ordered neural cell impulses. Can the sun learn? Are atoms self aware? What are the extreme ceiling and floor requirements for life to be plausible? We would be far better of trying to study this subject as best as we can, BUT fully realizing that we have ALMOST ZERO confidence in our current expectations of what life does or even might look like! Size, shape, color, composition, motility or method of energy acquisition could have literally any possible value as closely as we can currently theorize.

That's my unique opinion of this matter, while it may not be mainstream science, It certainly raises questions about the ultimate essence of this quality that matter can possess called "life".

Thank you for asking such an interesting question!

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Assuming these aliens have advanced technology since they are coming here and we can't go there, then they must have intelligence. If they are not immobile (like a giant Cray computer) they must have some kind of neural network which, if it is organic, has to occupy some volume. This places a lower limit on their size, don't you think? My little dog does not have the number of neurons to think of these kinds of questions, after all. Now that we have established a minimal size for the intelligence, there has to be a body capable of carrying it. That gives us something the size of people or maybe bigger.

In movies they have to have an actor acting as an alien, or one moving so that a computer simulation can be made. This sort of pushes the envelope towards arms and legs, etc. I don't see any logical need for two of each though, although the visual system seems to have developed more than one time in the evolutionary scheme here on Earth, and for depth perception two eyes are good, three is redundant, one is not enough.

How they would get here, I don't know. Certainly not especially practical to travel hundreds or thousands of years in a tin can. However, there is no way that we have deduced to get over these vast distances faster, without violating some of the known laws of physics. Metal rocket ships are what we can build, although plastics and nanofiber construction is a rapidly developing field. We don't have force fields, and no body even knows what that would be.

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Astros46

Then again, perhaps a sense of fear can be humbling and beneficial to mankind. Our present-day lives have become so simplified in every sense of the word, that we have sufficient time and freedom to drive wedges between any and all possible differences we find with other human beings. Many people associate an ultimate, desperate fear with savage-like, hateful, destructive behavior, such as looting, burning down our own cities and killing one another without cause. But in reality it is entirely possible that it would bring humanity closer together, be it to fight a common aggressor, or simply out of nervously scared curiosity. It would put things in perspective for anyone that has any sense of humanity, whether they presently appear to or not. It may or may not be passive, depending on the "relationship" that might persist from that point forward. Although, I may be far to optimistic too!

Thank you!

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People assume aliens are roughly the same size and shape as humans because people have seen them and given descriptions of them. Another reason is that it is easier to imagine a humanoid alien than to imagine something that was unlike anything you have seen before. The reason they have humanoid aliens on science fiction shows is because they want a face that can show emotions. If the alien is too different than you can not relate to it at all.

I don't know if any of the alien sightings are real but most people know what the aliens are supposed to look like. It is very likely that aliens would need the equivalent of thumbs so they can use tools and build things and they would probably walk upright so they can walk and use their hands to carry stuff. Why wouldn't aliens be roughly the same size and shape as humans? Evolution is not totally random. There are reasons we are the size and shape we are.

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This is a good point. There was an International conference that had determined there were four types of aliens some years ago. One type was supposed to be just like humans which scared them the most. Many sightings talk about little people so they know they are not the same size. It may all be interconnected. I guess it is all just too much for humanity to grasp for what might be out there. There are the different outer space movies that do cover lots of things. Then they come to the Earth in human form.

If they are really invisible to the naked eye though I don't think much will ever be done about them. Many things are not able to be seen by normal humans. I don't think they are ready yet to believe or to look at much even about aliens that are about the same size as humans.

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There are so many possibilities to take into consideration. First we gotta understands to our inventions are not actual invention, we just copy and paste certain things from different characters. So aliens might exist but we are not capable of seeing them. They might even be in the same location than us. We might have the same habitat but we are unable to see each other.

To answer your question most humans don't analyze things. They just go with the flow.

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Thanks Neilov50 for the ideas I think you have some valid points - anyone else care to challenge or expand?
Foxgru62 ...

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Newibr81 Has It Guys but thanks for all your input!

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More great insight Nathan

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