Astronomy / Space Alien size and planet mass.

[Quddus]

I was just thinking about life forms on other planets and their size/strength.

Let's assume they evolve to be of a similar design to us (standing upright on hind limbs, big brain in a head) i.e. humanoid.

If it's a bigger or denser planet we'd assume a higher gravity and therefore I'm guessing they might end up being shorter? But actually quite strong.

So if they came here they'd look small but would actually find our lower gravity quite easy and would be relatively strong pound for pound.

If they come from say a lower gravity system perhaps they'd be able to grow taller but would actually be quite weak compared to us.

Just thinking out loudly really... so thought I'd bore you all with it so you can join in with your thoughts...

 

[Iain M Norman]

Anything that evolves through a process of natural selection would certainly adapt to it's environment, I'd say that would be inevitable.

It's important to keep in mind that evolution and the process of natural selection is not necessarily a one directional pathway to bigger and more complex life.

Evolution has no foresight.

Humans are not the pinnacle of evolution on Earth any more than birds, elephants or tardigrades.

 

[adoredtv]

Strength and size is basically determined by availability of food, so it's quite possible that "humanoid" aliens could be absolutely massive ie dinosaur or whale size regardless of their planets g-forces.

 

[Quddus]

Anything that evolves through a process of natural selection would certainly adapt to it's environment, I'd say that would be inevitable.

It's important to keep in mind that evolution and the process of natural selection is not necessarily a one directional pathway to bigger and more complex life.

Evolution has no foresight.

Humans are not the pinnacle of evolution on Earth any more than birds, elephants or tardigrades.

Good points, agreed. Dawkins put it nicely in a lecture in Oxford years ago by saying "bacteria are the most successful organism on earth. We're merely the scum on the surface."

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Strength and size is basically determined by availability of food, so it's quite possible that "humanoid" aliens could be absolutely massive ie dinosaur or whale size regardless of their planets g-forces.

Absolutely right good point.

So to rephrase my question: food and energy supply (?oxygen ?other) etc being equal, and talkign strictly about the "scum on the surface" intelligent humanoid (let's assume) lifeforms, would a big planet yield shorter stronger beings and a small or less dense, less gravitational pull, planet yield taller but weaker beings?

I've always assumed that if "greys" that are reported by some actually exist what sized planet may they be from? They're generally reported as being small, so I wonder if it would be a large-mass planet.

 

[alexios]

So to rephrase my question: food and energy supply (?oxygen ?other) etc being equal, and talkign strictly about the "scum on the surface" intelligent humanoid (let's assume) lifeforms, would a big planet yield shorter stronger beings and a small or less dense, less gravitational pull, planet yield taller but weaker beings?

Oxygen isn't an energy source, it's just the oxidising agent aerobic organisms (that's all of life on earth except some bacteria like gangrene) use to break down food into energy. (simplifying — here's more info)

All things being equal (literally), organisms evolving in lower gravity will be longer/taller. Organisms growing in high gravity will be stockier with more muscle mass. It's physics, not just evolution. If your body collapses under its own weight, it's obviously not fit to survive in its environment.

But since all things are never equal, you get incredible variations in size. E.g. island species are usually much smaller than mainland ones. (see the extinct Mediterranean dwarf elephant, for instance) Or look at the differences between foxes and bears in temperate forests: same location, same gravity, same type of foods available, yet evolution doesn't go exactly the same way for both species, even though they're both incredibly successful and dispersed.

‘Greys’ are reported as being small and fragile, though — not the stocky body type associated with a high-gravity environment. (also: it's not planet size, it's planet mass. An Earth-sized world with a mercury core would have lots more gravity than the Earth).

 

[Surfinjo]

Good points, agreed. Dawkins put it nicely in a lecture in Oxford years ago by saying "bacteria are the most successful organism on earth. We're merely the scum on the surface."

I have developed a pretty poor opinion of Dawkins over the years, personally and this sort of populist tosh from him isn't going to improve it.

It's basic common sense that we and bacteria and everything in between are part of a greater ecosystem. To suggest that one part of another is lesser in any way, is arrogant and stupid in a way that only the likes of Dawkins is capable of.

As for the OP, whatever life may or may not evolve on other planets, it will be part of that planet's eco system. That will apply to every aspect of their existence.

Every life form on this planet possess unique aspects that allow it to compete for survival. Humans lack strength, stamina, the ability to fly, resist disease or tough skin. Intelligence is simply the aspect which we specialise to survive.

Looking at the time scale of life on this planet (3.6 bn years) compared to the time scale of ancestors who could preform the basic human activities of using fire and cutting tools, (4Mil years), it is apparent that intelligent life is not necessarily inevitable.

Such intelligent life will undoubtedly exist, but will be very few and far between compared to the number of life sustaining planetary eco systems that will almost certainly exist. So the chances that planets with extremely high gravity hold intelligent life of any kind is made even more remote.

 

[Groowie]

I have developed a pretty poor opinion of Dawkins over the years, personally and this sort of populist tosh from him isn't going to improve it.

It's basic common sense that we and bacteria and everything in between are part of a greater ecosystem. To suggest that one part of another is lesser in any way, is arrogant and stupid in a way that only the likes of Dawkins is capable of.

As for the OP, whatever life may or may not evolve on other planets, it will be part of that planet's eco system. That will apply to every aspect of their existence.

Every life form on this planet possess unique aspects that allow it to compete for survival. Humans lack strength, stamina, the ability to fly, resist disease or tough skin. Intelligence is simply the aspect which we specialise to survive.

Looking at the time scale of life on this planet (3.6 bn years) compared to the time scale of ancestors who could preform the basic human activities of using fire and cutting tools, (4Mil years), it is apparent that intelligent life is not necessarily inevitable.

Such intelligent life will undoubtedly exist, but will be very few and far between compared to the number of life sustaining planetary eco systems that will almost certainly exist. So the chances that planets with extremely high gravity hold intelligent life of any kind is made even more remote.

Haven't we already found life on another planets? Undoubtedly it is not something we (uneducated in that field) call intelligent but I'm pretty sure that there are people who deem even the smallest specks of life (that we oft think of irrelevant here) as something revolutionary. In terms of our importance on Earth, I wholeheartedly recommend the Cosmos series.

 

[Micky]

I always thought Oxygen was a Major Player too.
With pressure from gravity making stumpy Lifeforms though, a Blue Whale must be subject to great Pressures but is Huge.

Thinking about intelligent Life too I was wondering whether it stems from being aware of other monkeys and also having to be aware of danger from above and all around. Squirells too have to be aware all around in trees.
Your brain would have to interperet quickly changes in the envioroment to survive a suprise attack from predators.

Fish also can grow big, shoal and need all round awareness to be aware of predators but they lack a scenery. everything looks samey.

Mammals like dolphins and whales use Echo location so have more of an envioroment to interperet and use brain power.

So my point is, in my opinion a single Intelligent Lifeform on another planet would have to live in groups and adapt to changes in the envioroment like seasonal changes, weather, day night, and also have to be aware of all around from predators, oh and be big enough to cater for a big brain. ( ie not an ant)

So planets with flat featureless surfaces none seasonal and very little weather variations, or any change for that matter, would be less likely to harbour Intelligent Life.

 

[Surfinjo]

Haven't we already found life on another planets? Undoubtedly it is not something we (uneducated in that field) call intelligent but I'm pretty sure that there are people who deem even the smallest specks of life (that we oft think of irrelevant here) as something revolutionary. In terms of our importance on Earth, I wholeheartedly recommend the Cosmos series.

No. I am not familiar with the Cosmos series, but there is no evidence of any life, past or present, ever originating from outside the Earth.

 

[Groowie]

No. I am not familiar with the Cosmos series, but there is no evidence of any life, past or present, ever originating from outside the Earth.

I'd swear I've read that we've discovered some sort of life based on smallest scale. Oh, well. Does this count as alien? It was alien to us.

 

[Surfinjo]

I'd swear I've read that we've discovered some sort of life based on smallest scale. Oh, well. Does this count as alien? It was alien to us.

Any life originating outside the Earth would be a spectacular find and by definition be alien. But these organisms were found in California. Almost but not quite the same.

That apparent discovery was subsequently found to be not quite true.

http://news.nationalgeographic.com/...rsenic-space-nasa-science-felisa-wolfe-simon/

http://phys.org/news/2012-07-scientists-nasa-arsenic-life-untrue.html