Yes, if you have enough plants around they can convert enough CO
2 to sugars to make up for the CO
2 burned in a candle. Up to a point, that’s just how the world usually works, since many of us (people, yeast, mushrooms, etc.) are like candles, using up O
2 and releasing CO
2. Plants and photosynthetic bacteria do the opposite.
Right now, unfortunately, people are burning up so much of the carbon materials stored up from previous photosynthesis that plants can’t keep up with us, and the CO
2 level is going up. That is the main source of global warming, which is going to be big trouble.
Mike W.
Well, the vacuum part will make both your candle and your plant stop functioning, but you should also provide some air. Air is about 70% nitrogen, and most of the rest is oxygen. There are ideas of spacecraft which can voyage for many years by using plants to recycle the CO
2 of the crew back into oxygen. More practically, the experiment has been done in the Arizona desert in a laboratory called "Biosphere" and "Biosphere II". They were pretty close to getting it to work, but the Earth’s ecosystem is very complicated and difficult to understand every last little bit of it. And a closed (except for sunlight input and heat output) ecosystem may be missing vital parts, or may introduce its own features which are not present in significant quantities in the Earth’s ecosystem to matter.
The Earth itself is an example of a closed (well, except for energy input and output) system which has worked for billions of years. We’re making a mess of the equilibrium, though.
Tom
(published on 10/22/2007)
