Alien life

eco

Is there life beyond our own planet? Nobody knows but I personally think that there has to be some-one out there in this vast universe. Surely we can't be alone in a space that supposedly expands forever. People argue that you need oxygen to breath but thats only true for earth dwelling species. That doesnt mean that life on other planets need to have oxygen to live. They would have evolved to live in a different atmosphere than ours and perhaps our tunnelled vision has led us to look in the wrong places. We have to look at the situation with an open mind if we are to succeed in finding life on other planets. What do you think?

Capt'n Midnight

Originally posted by eco
People argue that you need oxygen to breath but thats only true for earth dwelling species. That doesnt mean that life on other planets need to have oxygen to live.

Thermodynamics again I'm afraid.
If you metabilise glucose aerobically you can get many times (>10) the amount of energy than anerobically doing it)

Unicellular life on our planet was able to live with oxygen for most of earths history. Oxygen was released as a byproduct by photosynthesisers, for about a billion years the brown oceans adsorbed it (and Iron fell out of solution) Eventually the sky and oceans became blue. And larger organisms could form because oxygen allows higher metabolic rates than anerobic respiration. Larger organisms need to move metabolites and support themselves etc.

Water would be the most common substance the photosunthesiesrs would have available to use, yes there are others who use sulphur and other stuff but if any of them evolved to use it , water would allow a planet wide distribution.

Also oxygen in the atmosphere is indicative of life. If there was no life then the oxygen in our atmosphere would gradually react with rocks etc. Again simple chemistry. If you find Oxygen in a spectrscopic examination of a planet it proves life exists there.

Ok there may be other susbstances you could use - but water is the most likely. If you propose HCl , then you need to worry dissolving the organism.

Note: oxygen is extremely toxic to the organisms that evolved before it became common in our atmosphere. Conversally they are immune to Hydrogen Sulphide , Carbon monoxide and Cyanide which are lethal to us in small amounts.

Redshift

There are supposed to be more stars in the universe than grains of sand on all the beaches in the world so say 1% of stars have planets and 1% of those have earthlike planets in terms of distance from the Sun, Water present, ect. Even if the odds of life forming on one of those planets is a trillion to one then there are many millions of planets with some form of life. I only saw this one one of those science channels a very interesting program hosted by Sam Neil.

bizmark

I think their is other life out their.....But that its very likely where the only intellgent race around in this galaxy at lest which is more than likely for the best.....wouldnt want to come across a alien race a few million years more advanced than us who are hostile

Mind you we might be able to beat them with water

albertw

Originally posted by Redshift
There are supposed to be more stars in the universe than grains of sand on all the beaches in the world so say 1% of stars have planets and 1% of those have earthlike planets in terms of distance from the Sun, Water present...

The drake equation http://www.seti-inst.edu/science/drake-bg.html

Lots of argument over the numbers.

And it doesnt take into account some other theories why no other life has been found. eg the zoo hypothesis, wherby we have been listed as a protected species by the rest of the galaxy and everyone is barred from coming to see us.

It also takes no consideration of our moon which some believe is the main reason we are still here, mars does not have a big balancing moon by contrast.

Personally I think there probably is bacteria floating around somewhere, perhaps even higher lifeforms, but as for inteligent life as we know it, we may well be alone.

And intelligent(ish) life is only here cause the dinosaurs (not known for thier intellignce) were wiped out.

Cheers,
~Al

Capt'n Midnight

Life (un encapsulated self replicating macro-moleucles) evolving on mars/venus possible to probable.

Life being sustained long enough to develop intelligence on a planet without a strong magnetic field - unlikely? - because life as we know it needs liquid water, liquid water implies water vapour in the atmosphere. Also that level of heating implies closeness to a star such that radiation from it will dissassociate H20 and possibly accelerate Hydrogen ions to escape velocity (or is it the solar wind that does this ?) and over billions of years will remove water from a planet. (note: This effect would also apply to Methane Ammonia H2S not just to water. - and whatever about needing Free Oxygen for active macroscopic life - you can't have life in an evironment without access to hydrogen compounds)

A resonable sized moon seems to be a requisite for life - maybe a binary system where a planet orbiting a small red dwarf as a trojan might recieve enough heat from a Sol sized star and be shielded by the smaller one ?

Unpossible

Anyone take into account that we probbably don't know all there is to know about chemicals? People here are arguing using known chemicals, isn't it possible (and likely) that we don't know squat about things out side out solar system? How do we know what stars are made of? Just because life on this planet works one way does not mean that it can't work in an unknown way in another planet, where the table of elements is (dare i say it) alien to ours

williamgrogan

Of course there is!

As the parameters in The Drake Equation are becoming better understood they are dramatically pointing to life being more likely elsewhere. Basic life is probably as common as muck.

Intelligent life could be rare though. It took Earth over 4 billion years to evolve it, which is about 1/3 of the age of the universe, and then only in one “species”.

GuanYin

Thread split and the discussion on alian biology moved to science.

On topic here please.

WG banned from Astronomy/Space for a week for posting a rake of irrelevant biblical quotes (available in the Science thread), religious philosophical debates elsewhere I think.

User45701

I Think there is life. I have argued this point many times with many priests who use all the bibical stuuf mentioned above.

I think the movie Contact said it best.

"If We are the only ones out there, Then its a hell of a waste of space"

albertw

Hi,

Originally posted by Unpossible
Anyone take into account that we probbably don't know all there is to know about chemicals? People here are arguing using known chemicals, isn't it possible (and likely) that we don't know squat about things out side out solar system? How do we know what stars are made of? Just because life on this planet works one way does not mean that it can't work in an unknown way in another planet, where the table of elements is (dare i say it) alien to ours

Its is probable that there are some chemicals that we are completely unaware of. Though most we can predict, and create. The cases where new chemicals would arise would likley to be in planets with very alien compositions, for example a large solid planet with high gravity, or exreeme pressure. Even within the solar system we have some rather strance worlds, Venus springs to mind, where the pressure is 90 times that of the earth. I doubt that we would find a substance that we could not work out its composition.

Your other questions take a little longer to go through.

Hydrogen is the simplest element. It has one electron and one proton. It is by far the most common substance in the universe. The first stars were formed by condensing clouds of Hydrogen, and in their cores the nuclear reactions produced heium, and in some stars all the elements in the periodic table up to Iron can be produced.

So how do we know that? The debate on what the sun was fulled by was only resolved in relativly recent times. Renessiance philosiphers had speculated that it was simply a ball of matter on fire, but such theories began to run into problems as more information about the earth was found out. For example the Earth was discovered to be billions of years old, if the sun was made of coal it would have burned out long ago. The current theory of the nuclear powered sun was adopted inthe last century, and has now passed every experimental test[1]. One example of the evidence is in the spectum that the sun produces, the peak of the light from the sun is actually green, which allows us to calculate the surface temperature, this temperature corresponds with the temperature we would expect the sun to have from experimental data. An effect of this colour=temperature can be seen in he night sky with other stars, the red ones are cooler nad the blue ones are the hottest. So we can be pretty confident of how the sun is powered and what the process is. For other stars, the processis mre complex and still being understood, in particular for the more extreme types of stars - the trully massive ones for example.

We find out about stars from looking at their spectrum, and in a similar way we know that most of the matter in galaxies is hydrogen. except that the natural spectrum of hydrogen isnt visible, its around the 21cm wavelength, which requires large radiotelescopes to see. And large clouds of hydrogen are floating around in space still, though the exact distance to the ones near the milky way is dificult to calculate due to the abscense of stars in or behind them.

So stars like the sun are capable of producing elements up to Iron. At this point you need to add more energy to the reactions than you would get out, so nothing higher than iron is produced by stars like the sun. Its only in supernovae, when the star collapses on itself that conditions are right for further reactions to take place, and this produces all the heavier elements that we see on Earth and the other planets.

These elements are also seen in and aound stars, as peaks and troughs in the spectrum from the stars. The first stars would have been almost purely hydrogen but the stars that are produced today have components of lots of different elements, which astronomers refer to as metallicity.

All of this flows from the basics of atomic physics, protons electrons and the like, and the standard model of all these particles is almost complete, and much of this has been experimentally validated on earth in te `atom smashers` in places such as CERN.

Based on all that, (and I can waffle more [and probably more coherently] if you like!), I hope you get an understanding of who things are thought to work, and why its unlikley that a different set of elements are likley to turn up elsewhere.

As to where this leave us as regards life elsewhere... thats a different matter

Cheers,
~Al
--
www.irishastronomy.org

[1] Solar neutrinos were a major headace until recent years, but thats sorted out now!

Capt'n Midnight

Re: sun temperature
The amount of light will depend on how far the star is away and it's temperature.
But the composition of the atmosphere will be far more important - eg: on our planet most of the Solar radiation is blocked by the atmosphere. Ozone for example blocks much of the UV. UV is important because some of those photons have enough energy to break many of the chemical bonds in bio-molecules. (sunburn/fading of posters etc) - yes algae etc. can produce sunblock but more UV favours faster evolution ? (but I suspect not as much as high levels of oxygen)

So on an Oxygen free planet there would be a lot more UV - even if the star was a red dwarf. This would make things more difficult for teressterial organisms, aquatic one would just be deeper in the sea. eh not that simple - the sea would be brown and more opaque than here since lots of iron would be dissolved in it.

Yeah the crust of our plannet and all the "terreaterial planets" has a lot of Oxygen with silicon and iron taking up large percentages of the rest. Our planet is mostly made up of supernova remnants. In a universe without supernova none of the heavier metals would have formed - but more importantly they would only be found in the core of stars - not an ideal place for life as we know it.

From all of this we can assume that most planets will be like ours - a battle between the solar wind , magnetic fields , gravity and energy - a battle for Hydrogen ions at the top of the atmosphere - too close to the sun and all hydrogen will be lost (Venus used to have oceans 1Km deep), too small (mars) and gravity won't hold it - on the earth our moon and magnetic field allow us to hold on to enough hydrogen to have oceans and a reduced biosphere. The other teresterial planets have very oxidised surfaces - not ideal conditions for complex chemistry.

Further out the gas giants have held onto their Hydrogen - yes there is liquid - essential for transport of large molecules - but it is so cold that chemistry is very difficult - almost all larger compounds would be insoluble solids.