What would the world be like if the air were 78% oxygen, instead of 78% nitrogen? I’d imagine first off that accidental fires would be pretty horrendous.
Well, if it were too high, the air itself would burn up at the first flame, making it practically impossible to go above a certain level. Maybe someone else can tell us what that percentage would be. I suspect 78% is above it, though.
I don’t believe oxygen itself will burn, no matter how high the concentration. So I don’t see how what you assert (the air would burn) could happen. Can you clarify that?
As to the OP, some botanists think that higher oxygen concentrations reduce the effectiveness of photosynthesis. Too high, and our plants won’t survive on sunlight for energy. http://jxb.oxfordjournals.org/cgi/content/abstract/52/357/801
I’m not following this. What would it combust with? There is nothing flammable in air. I agree, it may be difficult to keep combustible/oxidizable materials around in a high oxygen environment. That might preclude life.
Really? I thought concentrated oxygen was flammable. :smack:
Heat-Fuel-Oxygen. Gotta have all three for a fire.
Though I’d think having 78% oxygen might make it quite a bit harder to put out a fire. Now that I think about it, would water have more oxygen dissolved in it in this world? And if so would it make water less useful to put a fire out with?
Is it not believed that the ancient Earth in the Carboniferous Period and before had an atmosphere with a far higher oxygen ratio?
Water removes two things. Heat and Oxgyen. Water supersaturated with O2 would still cool the fire.
What about methane? Granted, it only makes up 0.0001745% of the atmosphere by volume according to wikipedia.
Yes, and that’s why very large land animals could survive back then. I don’t know what the ratio was, though.
How would it get that high? The highest it ever was was around the Cretaceous period at 40%. You had much more vegetation and larger oceans then. I don’t know if it would be possible to reach 78%.
The oxygen itself isn’t flammable; it’s just that in high-oxygen environments, a lot of things that aren’t usually regarded as flammable, are, and the things which are normally flammable become even more so. But it’s still always something else burning, not the oxygen.
Many things that just sit around in our 17% O2 atmosphere would spontaneously combust in a high oxygen atmosphere. Any fires would burn hotter and more completely and longer. So pretty soon any incompletely oxidized materials on the earth’s surface would burn up. This would remove oxygen from the atmosphere.
Plus, the free oxygen in our atmosphere is the result of photosynthesis. Our atmosphere is not in chemical balance but has a constant input of O2 from photosynthesis and a constant removal of O2 from oxidation. If O2 levels get very high plants start to spontaneously combust. More intense and more frequent fires act as a check on plant growth, which acts as a check on input of oxygen into the atmosphere. At some point high oxygen levels themselves are toxic to plants.
So there’s an equilibrium value to the amount of oxygen an atmosphere will have. Any higher and you get fewer plants and less input of oxygen and more removal of oxygen.
Ok, I’m confused now. Does anybody have solid cite on oxygen levels through ages? Sources that I was capable to google are not consistent.
Also, Lemur, I thought that present oxygen level is close to 21%, not 17?
I was relying on memory and it turns out I was mistaken:
This is tangential to the OP’s question, but I might as well bring it up while it is still fresh in my mind. It’s something that has been pestering me for years. A biology professor of mine once said that evolution no longer occurs on this planet because there’s “too much oxygen.” He said that evolution ended about 40,000 years ago. What was he talking about? I’ve never seen or heard this anywhere else. As it relates to the OP, would evolution have occurred at all if the O[sub]2[/sub] concentration were too high to begin with? Roy Walford has pointed out that oxygen is a pretty nasty substance, as it “corrodes iron and participates in every fire in town.” He once opined that the reason a hostile alien race has never messed with us is because they might have come here to Earth, taken one whiff of our atmosphere, and said “zounds—all that oxygen!” “We better leave those tough little Earth devils alone!”
He’s an idiot, that’s what. 200-250 million years ago, around the Permian period, it’s believed the atmospheric concentration of O2 was up around 35% contrasted with the measly 21% we have today.
Or to put it another way, in a sense the oxygen in the air is already burned; atomic oxygen, single atoms of oxygen combine with each other ( and most everything else ) with great enthusiasm. The oxygen in our lower layers of air, O2, could be considered “oxygen ash” just as water can be considered burned hydrogen.
Well, one thing I know is that in a more oxygen-rich atmosphere, you can get bigger bugs. This is because most arthropods don’t have ‘lungs’ like we do, but merely a passive system for absorbing oxygen into their blood. Past a certain size, this becomes inefficent (hence why larger animals developed organs to ‘suck’ in the air to allow for gas exchange ie lungs).
But with a higher Oxygen concentration, these primitive lung-like organs are still workable at larger sizes. How big? Well, the arthropods would still be limited by the mass of their exoskeletons, but I’m guessing big enough that you may want to reach for a claw hammer/revolver instead of a flyswatter
Similarly, animals with high metabolisms (mammals, for example) need a lot of oxygen/energy to maintain their body temperature, particularly if they are smaller. So small mammals might be more abundant. In fact, you may have ecosystems where large bugs prey on comparitavely smaller mammals!
Poster have mentioned high concentrations of oxygen during the carboniferous. Will this be a problem when I’ll use my time travel machine to hunt dinosaurs (I’ll pay attention not to kill any butterfly, I promise)? Or is our body able to handle an oxygen rich atmosphere?
ETA : Just remembered that some people are given oxygen to breathe. Still, I leave my question, in case there would nevertheless be an issue with breathing all the time oxygen-rich air when you’re otherwise in good condition.