Science Life on other planets discussion

[Pyromaniac605]

I thought we should have a thread to discuss life on other planets.
Firstly I would just like to suggest life that doesn't need oxygen.
As weird as that sounds, how do we know that oxygen is vital to life? for all we know it could just be the way life evolved on Earth. What's so special about oxygen that says that all life in the universe needs oxygen?
Think about that for a while.

Darren

 

[Artlav]

Here on Earth: Hot underwater volcanoes are teeming with life that dos not need sun and needs sulfur hydro-something. Still carbon-based and takes oxygen though.

Somewhere else life might be distinctly different. What can be imagined tend to be somewhat pale, like silicon-based life on hot planets, or liquid nitrogen-dissolved life on colder worlds.

The most basic definition of life don't need specific chemicals involved, and is based on behaviour and tendencies of the patterns observed. Can't find it though.

 

[SiberianTiger]

I believe that earliest possible indication of some planet has a life whose presence is detectable by remote sensing should be some peculiarity of its atmosphere (let's assume for starters we are scoping down to planets with atmospheres). For Earth, such is presence of free oxygen in atmosphere. It's a violent chemical agent and it would quickly on astronomy scale react away, producing oxides, had there not be a constant replenishment by Earth's plants and photosynthesizing Protozoa. And we can characterize life as something that disturbs natural energy balance in its environment.

However, to view some characteristic of a different planet as "untypical" we must first have a statistics on a bunch of "typical" planets with similar mass, rotation and illumination. Knowing only the Solar system is of little help here, because the only atmospheric look-alikes we have here are Uranus and Neptune. Two specimen in a category is just too few to produce a viable statistical set. I hope then in the coming centuries we collect more knowledge on various planets in extrasolar environments, however.

 

[Grover]

yesterday, an argument in physics class brought up a quite valid point:

if there are a billion stars in this galaxy, and billions of galaxies in the universe, that gives an absolutley HUGE number of solar systems where life COULD potentially exist.

now, if you consider that the universe constantly renews itself, as suns 'supernova' and new ones are born, that means that there is an infinite number of times that the right conditions could be made, and if something can happen, and the process continues forever, then by maths and probability, it WILL happen, the only question is when.

also, for the present alone, if there is a 0.000001% chance of a planet being able to sustain life of any kind (back the the oxygen question), then due to the number of star systems, it would be sensible to say that there SHOULD be some life SOMEWHERE in the universe

however, sonsidering the 'galactic speed limit' of c (~3.3x10^8 M/s, or 330000000 M/s, or 330 Mega meters /second) it would take 4.4 years (minimum) to reach our closest star, and possibly millions of years to reach other parts of the galaxy.

so the question really is:
can we find a way to traverse the galaxy practically?

some people believe extreme magnetic fields can produce a "hyperspace" effect, but if you travel conventionally, then the speed-time effect as you approach the speed of light would mean that if it took you 4 weeks to travel there at your top speed, you would be travelling for 28 years (based on Stephen Hawking's theory) and during a one year journey, ~365 years would pass by.

therefore, with our current technology, travelling to alien worlds is impractical

 

[T.Neo]

some people believe extreme magnetic fields can produce a "hyperspace" effect, but if you travel conventionally, then the speed-time effect as you approach the speed of light would mean that if it took you 4 weeks to travel there at your top speed, you would be travelling for 28 years (based on Stephen Hawking's theory) and during a one year journey, ~365 years would pass by.

No... that sounds like Heim theory to me. Hawking works primarily with wormholes in that field, and they have their problems.

There is the Alcubierre drive, but it has a lot of problems. You cut out a lot of them if you don't try to use it to go above c, but it's orders of magnitude less cool that way.

therefore, with our current technology, travelling to alien worlds is impractical

No... it is impossible with our current technology, but possible with out current scientific knowledge. Whether it is practical or not is determined by how good your technology is.

Quite impressive travel times to nearby stars have been demonstrated by theoretical concepts, and if you could travel fast enough, you could travel across the Galaxy in some ridiculously short period of apparent time, due to time dilation. But getting up to those absurd speeds would be very difficult.

Life on other planets is quite likely; the elements for it are common, and it appeared quite early on in the history of the Earth, which lends to the actual formation of life to not be an extrodinarily rare event. The evolution of complex life and intelligent life are another matter, but I think it would be unwise to be limiting in the scenarios in which complex life can evolve.

There are things that make familiar carbon-and-water based life superior to so called "alternate biochemistries"; such biochemistries could concievably form life, but the less efficient biology would probably limit such life to simple, single-celled forms.

 

[Izack]

Straying a little bit from the point, but not too much...

If life can be seen as a system of chemical reactions (an unbelievably, mindbogglingly complex system,) what's not to say that any chemical reaction isn't a very (insert as many more verys as you see fit) primitive iteration of life? It doesn't last very long because it either isn't sustainable or it lacks the ingredients/conditions necessary to sustain it. By this reasoning (faulty or not) life could exist anywhere matter and energy exist in significant quantities, so long as the reaction can be sustained.

One of the many problems with this is that it points to life in too many directions at once, and considers too many mundane things to be 'alive' (like car motors and nuclear reactors. :lol

Just a random idea; feel free to ignore or snicker.

 

[jedidia]

What's so special about oxygen that says that all life in the universe needs oxygen?

As far as I know, none claimed that all life in the universe needs oxygen. We have a multitude of organisms here on earth that do quite well without it.

However, for really complex bio-orgnisms, oxygen seems like an optimal solution: it is the most aggressive agent, reacting with almost anything, and fast at that. Our whole organic system relies on this reactivity. We breathe oxygen into our lungs and distribute it through our bodies, and it's absolutely essential that it reacts with anything it finds along the way.

Other methods are thinkable, for example methane breathers, but it can be savely concluded that their organisms would be somewhat slower, due to the lower reactivity of their breathing agent. This can be said about pretty much any gas that could provide a functional agent.

I think it is therefore save to say that on worlds where oxygen exists, it will be used by local complex life. Because, in terms of evolution, they will surely be fitter than counterparts breathing other gases, because their organisms work with inferior speed: slower thinking, slower movement.

Only on worlds where there is no oxygen (which should still be a lot) I could imagine an alternate form of organism to dominate, i.e. based on whatever best chemical agent they have in their atmosphere.

 

[T.Neo]

See definition of life on Wikipedia.

IMO it can really be narrowed down to three things;

Reproduction- life must reproduce, and pass on information to it's offspring.

Metabolism- life must sustain reactions that fuel activity and aid in the repair and maintainence of it's structures.

Structure - life must have structure and organisation (i.e. it mustn't be sprawled out as a puddle on the floor).

The idea of slower organisms is an interesting one... I have a feeling that it would lead to organisms with more of a resemblance to plants, fungi, or even more primitive animals like cnidarians, sponges or starfish.

 

[SiberianTiger]

One of the many problems with this is that it points to life in too many directions at once, and considers too many mundane things to be 'alive' (like car motors and nuclear reactors. :lol

Instead of trying to define 'alive' try to define 'dead', and you'll see you are wrong.

The ad hoc theory describing life on Earth, for instance, requires the following sufficient signs of object to consider it alive:

• Alive organism an object restricted to its physical boundaries.
• Its boundary is one-way conductive for and information and entropy (but isolates information from escaping outside and entropy from passing inside).
• Life consumes energy to build up its information complexity.
• An organism is able support and recover its state.
• An organism can preserve and spread its life information (most basically, it's a spreading the genome to entire species through reproduction).

 

[Izack]

I never was keen on biology. :tiphat:

 

[Pinguinboy]

I think Extraterrestial lifeforms do not always have to require to our defenition rules of life. We see this as our construction state, but who says it will be also at other life forms?

 

[SiberianTiger]

I never was keen on biology. :tiphat:

It's more about philosophy, maths, computer science and thermodynamic, really. Speaking shortly, life is about information. Computers are about information, too - but today they are very poorly protected from entropy (they need humans to protect them, supply them with power, and reproduce them). What's simpler to do: destroy iPhones or destroy herring?

 

[Ghostrider]

life must have structure and organisation (i.e. it mustn't be sprawled out as a puddle on the floor).

There could be a debate on this: a friend of mine's pet cat definitely qualifies as "life", but he's as sprawled out on the floor as any puddle.

 

[SiberianTiger]

I think Extraterrestial lifeforms do not always have to require to our defenition rules of life. We see this as our construction state, but who says it will be also at other life forms?

If they don't match our definition when we encounter them, we hardly recognize life in them. Or probably our understanding of life undergoes a shift. The possibility of latter is really the Holy Grail of entire space exploration undertaking.

 

[docabn]

To heck with alive or dead.
Go with sentient or not. Alive simply means that there is a possible new set of recources to exploit. Sentient could mean that too if you are and evil dictator, but it more so represents the ability to exchange ideas that would be novel and lead to greater scientific and philosphical insite.
As for non sentient life, the closer to earth like the better. Finding a world which has lifeforms that humans could possibly exploit for food, industry, medicine, ect... gives us a destination and something practicle to do once we get there. The more of these extraterestrial locations we inhabit the greater the chance of discovering sentient life forms (who we hope are not evil dictators). :lol:

 

[SiberianTiger]

Alive simply means that there is a possible new set of recources to exploit.

As for non sentient life, the closer to earth like the better. Finding a world which has lifeforms that humans could possibly exploit for...

Which combined, doesn't characterize ourselves as sentient species.

 

[Eccentrus]

on the topic of whether life really needs oxygen or not, the answer is blatantly obvious: No, the breaking of sugar and other sources of energy (fat) does not need oxygen, while it is true that oxygen gives us a competitive edge on faster metabolism via the Tricarboxylic cycle and the cell respiration/electron transfer system in the mitochondrion, to produce much more ATPs than the unoxidized metabolism. but then again we should refrain ourselves from assuming that this is also the case with organisms that doesn't use ATP as their energy currency, if they require something else, such else a reducer rather than an oxidizer as the metabolic enhancer. But then again, since most reducers are metals such as Lithium, Natrium, or in the odd case of Carbon, then perhaps such complex organisms which use this method of fast paced metabolism could be "eating" the reducers, and respirate the "fuel", exactly the reverse of what is common on earth.

 

[Izack]

If it moves, eat it! If it thinks, enslave it!

 

[T.Neo]

People, the correct term is not sentient life, but sapient life. There are far more organisms on this planet that are sentient, than humans. "Sentient life" is just a sort of holdover from science fiction from the likes of Star Wars or Star Trek.

As for non sentient life, the closer to earth like the better. Finding a world which has lifeforms that humans could possibly exploit for...

While I agree that certain Earth like traits are desirable in the search for sapient life, I fear that we will be in a paradigm for quite some time, that sapient life requires a planet exactly like the Earth to evolve.

 

[jedidia]

Go with sentient or not.

actually, defining the difference between sapient and non-sapient live is a lot tougher than defining the difference between alive or dead.

if they require something else, such as a reducer rather than an oxidizer as the metabolic enhancer.

Now this is a really neat idea! haven't thought of that yet (then again, I suck at biology and am not too bright on chemistry either, so it's really no surprise I haven't thought of it...)