What if Life Wasn't Life to Us?

[Skyler4856]

Orion.....MWAHAHAHAHAHA

[Ralathon]

The reason we're looking for earthlike life is because our form of life seems the easiest to form.

We're made primarily out of Hydrogen, Carbon, Oxygen, Nitrogen and Phosphorous. Those are also the most common elements in the universe (ignoring noble gasses that don't lend themselves for chemical bonds).

Life is going to be made out of very complex molecules or structures. This requires some sort of solvent to ensure the needed components can interact. Water is both abundant and one of the best known solvents.

The building blocks of RNA and DNA are very easy to make and self assemble into polymers. This drastically reduces the random chance element in the formation of life.

So based on those things it makes sense to look for earthlike life. Of course this could be completely wrong, we only have 1 datapoint after all. It could be we're the anomaly while life elsewhere consists of sentient plasma bubbles in stellar cores, or quark-gluon structures on the surface of a neutron star, or something wilder still. The thing is that we don't know and it makes sense to start with the one method that we know for sure to work.

[How2FoldSoup]

Been putting this very question to people for years.... I'm 54 in July.

People base their assumptions for life based on life as they know it, Some planets "cannot support life" as it has a methane atmosphere... that is wrong, it cannot support life as we know it... we were born here, we breathe oxygen, but what if life evolved on another planet and it breathed methane?

The surface of Venus is a probe killer... 80 - 90 atmospheres on the surface, but if life were to exist there, it would be short, stubby and have massive bones...

It is arrogance to think we are alone in the Universe, and also fatalistic.

Out of the billions and billions of planets out there, only ONE evolved life? Why not 2?

If you believe in 2, why not 100.... 1000.... a million?

And as for the argument that they couldn't travel here because it would take hundreds, if not thousands of years...

YES.... based on our technology.... what if they had warp drive, or FTL, or wormhole creators?

And they also assume these creatures have our lifespans.... hell, turtles can live for over 100 years..... why not aliens living for 1000 years...

In our loneliness, I suspect we have become very arrogant in our thinking... or maybe, fatalistic, or small minded...

You need to dream, to imagine... what if?

Yesterdays "what if" is today's reality.

I completely agree with the idea of your thoughts but I have to stay skeptical about using methane or some other elements for biochemistry. I believe life thrives throughout our galaxy even if it's just at a cellular level. I am extremely hopeful of finding fossilized bacteria on Mars or living bacteria in Titan or Enceladus's underground oceans. I have no idea what type of life we could find but I think it would be smarter and easier for us to look for carbon/water based lifeforms before anything else.

Biochemistry is a complicated thing and when you look down at our own it's amazing how it functions at the particle level with proteins transferring 1 electron at a time. It's simply amazing. Having said that, if life could figure out a way to use other elements and compounds to do their own biochemistry than so be it. But, until we've seen it then it will always just be theory and it's easier to look for what you know best. What we know best is Earthlike life.

[Accelerando]

I completely agree with the idea of your thoughts but I have to stay skeptical about using methane or some other elements for biochemistry. I believe life thrives throughout our galaxy even if it's just at a cellular level. I am extremely hopeful of finding fossilized bacteria on Mars or living bacteria in Titan or Enceladus's underground oceans. I have no idea what type of life we could find but I think it would be smarter and easier for us to look for carbon/water based lifeforms before anything else.

Biochemistry is a complicated thing and when you look down at our own it's amazing how it functions at the particle level with proteins transferring 1 electron at a time. It's simply amazing. Having said that, if life could figure out a way to use other elements and compounds to do their own biochemistry than so be it. But, until we've seen it then it will always just be theory and it's easier to look for what you know best. What we know best is Earthlike life.

Since the theory can be tested by sending space probes for the same order of cost as any other massively expensive search-for-life mission, why isn't it a good idea to look for alternate biochemistries before carbon+water-based life? Either way it isn't going to materially benefit us in any direct way, and if we do find life in alternate biochemistries then it will definitely shed light on a vast new field. Not to mention massively broadening our vistas for where we might find life in the universe...

[Seret]

Because based on the only solid data we have such missions are less likely to succeed. It's logical that the first places we look are the places that we know for certain are viable.

[KerikBalm]

The problem with the requirement for an earth-life atmosphere for life is that the Earth did not have an earth-like atmosphere when life first arose. In fact, there was practically no free oxygen at all on earth because it is so reactive.

Why do people keep bringing up this "Earth like atmosphere" requirement as if that was ever a seriously held "requirement"?

Yes, Earth's atmosphere changed over time. No, nobody is saying there can't be life on mars because it lacks Oxygen.

Also FWIW, the nitrogen content of Earth's atmosphere has been pretty much stable.

As Rathalon said"

We're made primarily out of Hydrogen, Carbon, Oxygen, Nitrogen and Phosphorous. Those are also the most common elements in the universe (ignoring noble gasses that don't lend themselves for chemical bonds).

Life is going to be made out of very complex molecules or structures. This requires some sort of solvent to ensure the needed components can interact. Water is both abundant and one of the best known solvents.

The building blocks of RNA and DNA are very easy to make and self assemble into polymers. This drastically reduces the random chance element in the formation of life.

So based on those things it makes sense to look for earthlike life.

And also as I previously said: you need to consider the cosmic abundance of elements in the Universe.

Its no accident that life here mainly uses the first rows (after hydrogen) in the periodic table.

Carbon is more common than Silicon, carbon's bonds are more stable than silicon. It seems rather unlikely that silicon based life would arise unless carbon had somehow been locally depleted. Carbon containing compounds would be more abundant and diverse, and would thus outcompete silicon compounds almost(?) everytime during abiogenesis.

I'd wager that the vast majority of life in the universe is Carbon based, simply based on the abundance of carbon relative to other potentially suitable atoms.

Water based... I'm not so sold on. I'll concede that amonia based life seems quite plausible (in place of water, Ie, carbon based life with NH3 as a solvent, not OH2)

Methane as a solvent: I'll conceed its plausible too, but that is still carbon based life

[Alchemist]

Carbon is more common than Silicon, carbon's bonds are more stable than silicon. It seems rather unlikely that silicon based life would arise unless carbon had somehow been locally depleted. Carbon containing compounds would be more abundant and diverse, and would thus outcompete silicon compounds almost(?) everytime during abiogenesis.

Look again at lithosphere composition: silicon oxide is the most abundant compound on rocky planets. The question is getting it into the solution (probably some fluoride content in the solution could fix this issue). But in cases there already are hydrocarbons (mostly methane) they are probably far more likely to get involved into complex organics formation than silicon, especially if part of the reactions are happening in the atmosphere while most silicon compounds aren't very volatile.

And again, if you look at nucleotides and proteins, they are not purely carbon-based, it's more like C+N (and even with occasional S in some aminoacids). If silicon was more accessible it could have been something like C+N+Si.

[Idobox]

It's important to define life first. My favourite definition is a system that decreases its own entropy by using an energy gradient. By this definition, a lot of things are alive, including cities or computer networks.

If you use this definition, you can find life anywhere you have an energy gradient, which means pretty much everywhere. Chemical life would be the easiest for us to recognize, with a metabolism and such. Carbon and silicon are the best candidates, with a preference for carbon (SiO2 is sand, difficult to excrete, and silicon is more rigid). Interesting sources of energy : sunlight, cosmic rays creating reactive species in the atmosphere, volcanism, radioactivity (there are fungi that feed on gamma rays), temperature gradients.

If you want, you can even imagine much more exotic stuff, like electromagnetic structures in dust clouds, or pseudo-molecules on the surface of neutron stars.

People look for liquid water because everywhere we find liquid on Earth, we find life. It doesn't mean you will always have life where you find water in the universe, but it's a good place to start looking.

Looking for oxygen is done for similar reasons. Because it is so reactive, you need something to produce a lot of it to get a measurable amount of it in a thick atmosphere. Once again, not a sure proof of life, but a very good clue.

[shynung]

It's important to define life first. My favourite definition is a system that decreases its own entropy by using an energy gradient. By this definition, a lot of things are alive, including cities or computer networks.

Do not forget that life can copy itself (reproduce) without any external help. By this definition, computer networks and viruses aren't alive, which makes a lot of sense.

Edited April 22, 2014 by shynung

[Idobox]

Do not forget that life can copy itself (reproduce) without any external help. By this definition, computer networks and viruses aren't alive, which makes a lot of sense.

Different definitions. An animal that can't reproduce (for example a mule) is still alive.

A planet sized organism (like in Solaris) could not reproduce either, but would still be considered alive.

Reproduction is nearly universal in Earth's life, but not exactly necessary. And I like the idea of virus and computer networks being alive, although many people prefer a more constrained definition, that usually involves metabolism.

[KerikBalm]

Well, a mule may not be able to reproduce, but its cells can.

Its pretty easy to culture any animal's cells

Henrietta Lacks may be dead, but her cells live on in labs all around the world (hela cells).

If something is made of living things, is it then by definition alive?

Is a nation alive?

Is an ant colony alive, or only the ants themselves? only the queen? only the ant cells?

Of course, humans can't reproduce without glucose, or essential amino acids and vitamins... whereas other organisms can survive on just CO2, N2, light, and some minerals...

Then you have some species of mycoplasma, which are obligate intracellular parasites.... pretty darn close to viruses... and a plausible example of an intermediate of a living cell could evolve into a virus.

You can have bacteria growing on minimal media. You can have mammal cells growing, but they require addition of growth factors and "complex" media. You can have intracellular parasites growing in very complex media. You can grow some viruses in cell lysate. In some ways, you might say its simply a matter of the complexity of the "nutrients" needed to make it grow.

I would say it is any self propogating organization of matter with the capacity to evolve (as opposed to simple crystal structures). In that sense, viruses are life.

From a cell/molecular biology point of view (which is what I study) no line is drawn between "living things" and "viruses". At the molecular level, they are pretty much the same, its simply a matter of complexity.

You could view the infected cell as the "living virus" and the virus particle as something akin to sperm. You don't often study a pathogen by itself, but the host-pathogen interactions.

And infected cell has a certain organization, certain pathways and such, and that infected cell can propogate that organizatiosl scheme.

Personally, I consider viruses to be a form of life... just shift your focus from the infection particle to the infected cell, and you've got something that looks pretty much like life.

Its really just a philisophical question that serious science doesn't really address.

For the purposes of exo-biology, its sort of a "we'll know it when we see it"

-and yes, there is plenty of sci-fi where we initially don't know it when we see it

-the same goes for sentience

-and it goes both ways, with aliens not recognizing us as alive or sentient (typically until our resistance makes them take note, such as in Ender's Game, for example)

[Seret]

It's important to define life first.

Good luck with that...

[kiwi1960]

@KerikBalm

I won't argue the points I made, except one. You said that you doubted if anyone believed there wasn't life on other planets...

As I said, I'm 54, I saw the TV episode where Carl Sagan argued that life MUST exist on other worlds, the odds were in its favour, and byt the end of the that particular episode... scientists agreed with him.

Before that... well, it was changing... lets say... the 1930's and 40's.... scientists were saying that life on other worlds was impossible... or rather.,.. unlikely... times and attitudes have changed.

I remember an old teacher of mine who argued that because God created man, he couldn't have created life anywhere else because he would have said so...

I mention that ONLY because of the huge religious influence on the population way back when... diminished today, thank God... (excuse the pun) ... and its not open for debate.... I hate religious debates...

[KerikBalm]

Before that... well, it was changing... lets say... the 1930's and 40's.... scientists were saying that life on other worlds was impossible... or rather.,.. unlikely... times and attitudes have changed.

I remember an old teacher of mine who argued that because God created man, he couldn't have created life anywhere else because he would have said so...

I mention that ONLY because of the huge religious influence on the population way back when... diminished today, thank God... (excuse the pun) ... and its not open for debate.... I hate religious debates...

Well, a few points:

It wasn't too long ago that there wasn't widespread recognition and acceptance of other galaxies, leaving just our galaxy (me might be the only intelligent life in our galaxy... but the universe... no way).

To that, you can add no knowledge of extrasolar planets.

I'd imagine back in the 30s and such, people didn't bother really discussing things outside our solar system. I watched the old "The Day the Earth Stood Still" (not the new one with Keanu), based on the dialogue in that move, it seems at the time that people were really only concerned with, or even aware of, only our solar system and its 8/9 planets (with much speculation about mars and Venus, Venus was a Carte blanche because nobody had any readings below the cloud tops - and much fiction portrayed them as H2O clouds, and Venus as a swampy jungle world).

And I'd think we'd be talking about the perceptions from almost a century ago, but modern perceptions.

[Acemcbean]

Citation needed.

Heh, this was just a silly "thought" I had in a half-awake stupor at about 2 am. But if we must, I shall (probably not) do it for SCIENCE! And Jeb. Jeb too. Its almost 2 am again...