h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

does free O2 occure any where naturally in the universe, apart from super nova, or is it so reactive it just combines with other molecules

hmm think you are mixing occurrence and creation?

Super novas create the oxygen atoms (or elements) not the molecules (02) - although obv. those atoms once created could then combine to form 02. Or any other oxygen containing molecule.

Indeed, molecular oxygen has been detected (in 2007) in interstellar space.

02 the molecule has been detected elsewhere in the universe - other planets in the solar system and indeed in at least one extra solar planet.

So, heavy elements only get created naturally in type IIa supernovas (according to current mdoels) but molecular oxygen can occur in all sorts of places.

You don't need supernovae to create oxygen (element 8), elements up to Iron (element 26) are created by nuclear fusion inside Red Giant and Supergiant stars.

Only elements above iron require supernova conditions for their generation.

Ictoan is right though, you seem to be confusing nuclear reactions with chemical reactions.


Oxygen, however reactive, is still oxygen when it reacts with other things (in a chemical reaction).
All that changes in chemical reactions are the configurations of electrons in the outer reaches of the individual elements atoms.
The nucleus - which is what defines the nature of an atom - remains unchanged in all chemical reactions.

The energies which bind the outer electrons of atoms are much* weaker than the energies which bind protons and neutrons together in an atomic nucleus. That is why chemical reactions happen at our rather ambient temperatures whereas to force a nuclear reactions you need to generally be at millions of degrees C to get over the energy barriers to reaction. Hence supernovae, H-bombs epicentres, cyclotrons and star cores are the only places this sort of thing happens.








*very very much!

cheers Orcus - thought you might be along shortly!

i think i got the question arse about facewhat i want to know is can free O2 be found in large quantitys apart from earth or deos it tend to combine/react with the substaces it meets, theres a lot of CO2 and water/ice out there

thank you, the reason i asked was, to use in arguments with intelligent designers,

if we were designed why do we breath oxygen which in our atmosphere is basicaly plant crap, surely an intelligent designer would have come up with a system that used nitrogen, which is the most abundant gas we have

that also gets to the question/argument that the designer would have to wait for the plants it made to change the air to a degree where its creations could breathe so adding long times to their creation ideas

Things used to be anaerobic, until as you say enough plants evolved to raise the oxygen concentrations to useful levels. We have dioxygen (O2) on Earth partly because there's not mch left that's reactive enough to soak up the oxygen. There's plenty of carbon and hydrocarbons, but they have to burn if you want to combine them with oxygen. Left alone, they react very slowly.

Oxygen is generally considered to be a sign that life is present, because you need life to alter an atmosphere to any great extent, and only life is likely to free up oxygen from soil and water.

Dinitrogen (N2) is extremely inert - unreactive. I doubt there's any life out there that depends on nitrogen the way we depend on oxygen. Breathing oxygen only works because when you react oxygen with food molecules like sugar, you get energy out. That energy is what we use to live. To react nitrogen with sugar, or anything really, you have to put energy *in*.

The earliest life on Earth used sulphur and phosphorus chemistry.

So yes, high concentrations of O2 are unusual in the absence of life, but no, a sensible designer couldn't have used nitrogen instead because nitrogen doesn't work the same way.

article on interstellar oxygen
http://www.spacedaily.com/reports/Elusive_Oxygen_Molecule_Finally_Discovered_In_Interstellar_Space_By_The_Odin_Satellite_999.html

Don't bother arguing with them - it is futile as their case is belief based and not evidence based. And you are trying to refute it with evidence.

interesting bit on O2 and life - fromm when it was used to detect life on earth (it worked, btw )

http://blogs.discovermagazine.com/badastronomy/2009/08/04/lcross-detects-life-on-earth/

>The earliest life on Earth used sulphur and phosphorus chemistry.<

And that's fact is it?

To add to that, to not seem too rude. There is a *theory* that life began in what we call a reducing atmosphere - but when cyanobacteria evolved (aka blue-green algae) the process of photosynthesis evolved too and oxygen started getting produced.

This was likely devastating to most life as oxygen would have been horrifically toxic to them. So organisms that survived quickly developed methods to break it down as fast as possible.

This eventually became useful as it evolved lots of energy and ended up being the method that large parts of life used to turn fuel into energy and survive.

So our breathing started off as a desperate method of destroying that terrible toxin oxygen.


However, nobody actually knows this happened it just seems to fit most of the available data. Without a time machine noone can say what form of chemistry happened in early life. Nobody knows what the primeval atmosphere was consituted from - we just go by looking at the chemical composition of old rocks (with billions of years for nature to have screwed with our data) and the compositions of other planets' atomspheres to go by.


I wouldn't bother arguing with creationists either personally. I have far more useful and less futile places to divert my energy,

"I have far more useful and less futile places to divert my energy,"

Ah, still not completed Doom then?

Getting there

Short of inventing time machines, theory that fits the facts is all we're ever going to have about any part of history.

And to not seem rude myself - your post is pretty much my understanding of the state of the science of the early atmosphere. I just didn't think the full explanation was going to be helpful for Taff. I concede I should have said "probably used sulphur and phosphorus", but there's not need to educate me on chemistry. I pay people to do that.

Taff: I should think the reason nitrogen is so abundant in the atmosphere is that it doesn´t really react with anything. If animals breathed nitrogen, we might have run out of it long ago. With oxygen we have ways of replenishing the supply.

Fair enough Runescribe but presenting things as fact, when they are not, is not the best way for science to present itself.
I wasn't trying to educate you, more Taff

There is huge amounts of conjecture in that theory, it's far from being even remotely certain. To use the words of one of pre-biotic chemistry's more prominent researchers - it's unfalsifiable speculation. But still fun nonetheless.

Nitrogen is fixed from the atmosphere mostly by two (natural) processes.

1. Lightning.
2. Nitrogen fixing baceria - those which live in the root nodules of beans, peas and other leguminous plants.

So there are things that can utilise it directly. It is tough though, probably _the_ most stable small molecule.

It's wonderfully stuff. Comes in very useful in some organic reactions - you can often rely on nitrogen to just fall off a molecule and power the reaction.

Have you ever had the chance to play with liquid nitrogen?

*appears as a certain bulldog*

Ho yus.

The most stable small molecule? is it more stable than helium?

and for seriously interesting cold stuff, there are some funky things that happen to liquid hydrogen at certain temperatures and pressures, not least of which the way it boils.