Science Questions

Has all the air in the world been breathed before?

Sun, 29th Jan 2012

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Question

Tom Aust asked:

Hello - I really enjoy your podcast.

 

I don't know when you might be discussing something related to this but ...  I was listening to a Johnny Cash tune the other day and he wanted to get away from this woman and "go where the air ain't been breathed before". Is that possible (that the air hasn't been breathed before)? Especially in light of the thousands of species that have preceded us. Thanks.

 

Tom Aust

Northern California

Answer

Dave -  It rather depends what you mean by not being breathed before.  If you're only interested in the molecules not having been breathed in before - and specifically if you're interested in the oxygen and nothing else - then any oxygen molecule you're breathing in either hasn’t been breathed before at all - or it can’t have been breathed more that a few times, because otherwise it wouldn’t be oxygen anymore it would be carbon dioxide!

But, if you're thinking about the actual atoms and whether any of the atoms have ever been breathed before, that's a whole different kettle of fish.

Chris -  Because they're being recycled around the Earth all the time, aren’t they?  In the sense that a plant makes some oxygen, you breath it in and mix it with some sugar to make it into carbon dioxide,  that comes back out and the plant breathes that back in and recycles all these atoms again and again.

Dave -  That's totally right.  I was just doing some calculations.  It takes about 2,000 years for all of the plants in the world to work their way through all the oxygen in the atmosphere.  So, some of the molecular oxygen you're breathing in won't have been breathed in before.  But because the Earth is about 3.8 billion years old, you would have thought that pretty much all of it will have gone through plants and creatures in the past.

But then again, I wouldn’t say for definite that all of the atoms, all the molecules that you breath in have been breathed before, because there are 6 with 23 zeros (6 x 1023), or maybe as low as maybe 3 with 23 zeros (3 x 1023), molecules of gas in every lung full of air, and some of those might well have just been sitting there since the beginning of the Earth.

Also, some atoms have been coming out of volcanoes or degassing out of the centre of the Earth, and some have been raining in from space.  So, in a normal breath, a few atoms won't have been breathed before, but I think most of the air will, wherever you are.

Chris -  When you say Earth is 3.9 billion years old, you mean life on Earth is 3.9 billion years old because the Earth itself is a little bit older than that.

Dave -  Yeah, definitely.  So, creatures have only been breathing stuff for 3.9 billion years.

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I should think just about every atom of our atmosphere has done the rounds many times over. Don_1, Thu, 3rd Nov 2011

Not quite all of them. There are some that certainly have not. Bored chemist, Thu, 3rd Nov 2011

I saw a piece of air today and it looked brand newe ! neilep, Thu, 3rd Nov 2011



You must have been visiting Eyjafjallajökull, Iceland!!!

Other than the volcanic origin of components in the air, most of the Tritium and Carbon-14 components in the air come from the sun, and are relatively new. CliffordK, Thu, 3rd Nov 2011



You must have been visiting Eyjafjallajökull, Iceland!!!

Other than the volcanic origin of components in the air, most of the Tritium and Carbon-14 components in the air come from the sun, and are relatively new.


Funny that !..were ewe taking the tour too ? 





neilep, Fri, 4th Nov 2011


Funny that !..were ewe taking the tour too ? 

Nope, never been there.
But, it is the coolest name of a mountain that I know...
Did you learn how to pronounce it?  I'm sure it is pronounced just like it is spelled CliffordK, Fri, 4th Nov 2011

Some bits, yes. Most (all?) of the oxygen in the atmosphere was produced because living things exhaled it. Geezer, Fri, 4th Nov 2011


The question was about breathing... not photosynthesis. CliffordK, Fri, 4th Nov 2011


The question was about breathing... not photosynthesis.


What's the difference? Plants have to breathe too ewe know. Geezer, Fri, 4th Nov 2011

Some of the gases in the air we breathe have come from decay of heavy radioactive elements in rocks ...


http://en.wikipedia.org/wiki/Radiogenic

So have never been breathed before.
RD, Fri, 4th Nov 2011

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