Space Exploration and its effect on the Earth's Oxygen supply: I have a question

[SAPierce2006]

Alright, this may seem a bit of a childish question, but for my sake I need it answered. So please stay with me.

Alright, pretty much what this is all about is the effect that space exploration has on the Earth's air supply. We were all sitting around talking about the creation of a space station and having it in orbit. The thought struck me that for people to live on the space station (whether that be the intention of it or not) they would need to have a decent supply of air that was re-manufactured via machine instead of plant. Then I took that and said that if enough space stations were created then eventually the amount of Oxygen on the Earth would become so depleted that humans could no longer exist on it.

Yes, I realize that the Earth has quite an abundant supply of oxygen. It is in water, carbon dioxide, carbon monoxide, etc. The list goes on and on. I'm sure there are other supplies of oxygen as well, but eventually we would disperse them to so many different places, the air on the Earth itself would become noticeably thinner. Yes I realize that this will never happen, and the amount of space stations that would need to be created is vast, and our limit on other resources might become a factor before that. All that aside, the amount of air on the Earth would thin out because a gas naturally fills its entire container. And if you take away some of the air, the air will thin out to compensate for what you took out. Correct?

Another way of saying this is to describe all of the Earth's oxygen supply as 100 units (this includes the oxygen in the air, water, and everything else on Earth). Let's say we take 10 units of the Earth's oxygen and put it in a gigantic space station orbiting around the Earth. If this were to take place, then those 10 units of air would no longer be on Earth, and the 90 units of oxygen on Earth would spread out and fill up the space of the removed oxygen, therefore making it thinner. If this were to happen numerous times, the amount of oxygen on Earth would thin out to such an extent, then it could not My entire hall does not agree with this, and it seems that they think that the Earth will magically supply us with more oxygen.

Some of their debates are photosynthesis, and claim that the plants will reproduce our air supply, which absolutely makes no sense to me, because I've clearly stated to them numerous times that CO2 has oxygen in it, and they are just separating the C from the 2 O, and that the O must be there in the first place.

Yes, I realize this is a stupid question, but it seems that my entire floor is against me here, and I would just like some knowledgeable reasons as to why this is true, or not true. Basically, I'm trying to figure out who's thought pattern is flawed here.

Thank you for your time.

 

[MeJennifer]

You can extract oxygen from water using electrolysis.

 

[SAPierce2006]

Yes, I know. I took that into account. You would eventually run out of that as well. I'm not stating that this is probable and one day will happen, but I'm saying that if we were to make a ton of space stations, the Earth's oxygen supply would thin out.

When I say the Earth's oxygen supply I mean EVERYTHING. As stated in my previous post "this includes the oxygen in the air, water, and everything else on Earth". Eventually we would run out of things to derive oxygen from.

 

[MeJennifer]

Yes, I know. I took that into account. You would eventually run out of that as well. I'm not stating that this is probable and one day will happen, but I'm saying that if we were to make a ton of space stations, the Earth's oxygen supply would thin out.

When I say the Earth's oxygen supply I mean EVERYTHING. As stated in my previous post "this includes the oxygen in the air, water, and everything else on Earth". Eventually we would run out of things to derive oxygen from.

Well, then ok, by the time we are able to make so many space stations that we use up all the water and oxygen in the air, I think we would have no technological problems in mining other planets and doing fusion in space to get oxygen.

 

[SAPierce2006]

yes yes, I realize all of that. I'm not stupid. That is not being debated. I'm just looking for whether or not it was theoretically possible for us to move enough oxygen off of the Earth that it thinned out the oxygen enough that it would not be possible to breathe. Yes, I know its a common sense, stupid thing, but that is all that I am looking for.

 

[LURCH]

Your theory is sound. The O₂ that has been taken into orbit in spacecraft has indeed caused the remaining oxygen in Earth's atmosphere to "spread out" to replace the loss.

As has already been pointed out, oxygen can be extracted from water through electrolysis, but this method would work just as well on a space station as it does on the ground. So, Rockets could be launched with water on board instead of oxygen, and that water could be electrolyzed to provide oxygen. But then, the water in the oceans would "spread out" to replace the water that had been removed from them and launched into space. And, correspondingly, the oxygen in the water in the oceans would be spread out.

Any way you look at it, whatever action is removed from Earth and launched into space used in fact gone from earth.

 

[sdemjanenko]

it isn't set in stone that we need to get oxygen from our planet. We could find it out in space somewhere and use that. Plus the number of space stations required to use that much oxygen would, if your forgive my bad pun, be astronomical

 

[ray b]

if we use LOX to burn in the rockets
we would use far more O2 then the air in the spacestation need
just to get off earth

btw do we have a practical way to split CO2 back to O2
other then useing plants

 

[LURCH]

Lox burned in rockets mostly stays in the atmosphere. Of that portion which is burned outside, I'm sure most must fall back in.

 

[Nereid]

[snip]

Yes, I realize this is a stupid question, but it seems that my entire floor is against me here, and I would just like some knowledgeable reasons as to why this is true, or not true. Basically, I'm trying to figure out who's thought pattern is flawed here.

Thank you for your time.

As LURCH has already pointed out, your idea is basically sound ... whatever is taken 'off the Earth' is gone.

With respect to oxygen, the element, there is one way to replenish it, using just what we have here already - we could make more oxygen, by nuclear reactions, transmuting (say) carbon. That it would require a huge amount of energy, that it would be utterly impractical, that there would be many other, much better, solutions to this 'problem', ... are irrelevant wrt your idea.

However, there is an 800 kilo gorrila in the room - what comes into the Earth. There are several (thousand?) tonnes of 'space dust', and several (thousand?) tonnes of meteorites, that are added to the Earth's mass, every year. These contain oxygen.

Then our intrepid spacestation denizens may feel like repaying the oxygen debt to mother Earth, so they may find a suitable comet or KBO, attach a rocket (or just spread carefully calculated white and black reflectors), and wait a century or two, and kablam! several billion (trillion?) tonnes of easily digestable oxygen, delivered right to Earth's doorstep.

 

[chronon]

Well, of course if you remove oxygen from the Earth then the Earth will have less oxygen. On the other hand there are lots of processes going on that tend to balance things out, so in a sense oxygen is 'magically' replaced. Firstly photosynthesis converts CO2 to oxygen - but you use up CO2. However, in the long term this will be replaced from the CO2 in seawater, and from volcanoes.

As for transmuting carbon, well that seems a hard way of doing things as the Earth is about 30% oxygen by mass (carbon is a fraction of a %). If you've used up the Earth's oxygen then you're just left with a lump of iron.

 

[TomServo4]

"All that aside, the amount of air on the Earth would thin out because a gas naturally fills its entire container. And if you take away some of the air, the air will thin out to compensate for what you took out. Correct?"

What you say about gases filling containers is absolutely correct. However, I would hesitate to call the Earth a container. Granted I don't have a degree in physics, but to the best of my knowledge it is the Earth's gravitational field which causes the atmosphere to "stick" to the Earth. Therefore it seems to me that the lessening of oxygen on the planet would cause the atmosphere to contract.

Now, the air probably would still become thinner. This would be because of a decrease in air pressure, since less molecules would be weighing down on one another. This would in turn allow them to move a little more freely. However, it would likely be far less severe than if the atmosphere were some kind of container the oxygen was attempting to fill.

Here is the main difference between the idea of a container and the gravitational field: the volume of the atmosphere in a container model would remain constant, whereas with a gravitational field the volume decreases as the oxygen depletes. Therefore, yes, the air will become thinner, but at a much slower rate.

That's assuming I know what I'm talking about, and likely I don't. :tongue:

 

[tony873004]

Oxygen isn't the only resource we would export to space while building this astronomical fleet of space stations.

Assuming all materials needed to build the space stations, including oxygen, come from Earth and not elsewhere in space, as soon as the total mass of all the spacestations was 6 x 10^24 kilograms, there would be no more Earth.

At some point in our space station building frenzie the Earth would no longer have enough gravity to hold onto the Moon.

 

[russ_watters]

Yes, except for the last part, tony - if the space stations were all in Earth orbit, the moon wouldn't know the difference whether the Earth was consumed or not.

 

[Phobos]

Note that space stations eventually come back to Earth (2 for 3 so far...Skylab and Mir).

site note...Part of the planned moon base project is to see if they can extract O2 from the moon rocks so they don't have to bring O2 from Earth.

 

[russ_watters]

While we're at the side-notes, AFAIK, very little oxygen meant for breathing (if any) is actually lost to space - it is recycled.