life on Earth
Can we use artificial photosynthesis to stop global warming?
Plants are amazing little chemical ... well, plants. In the process of photosynthesis, they take carbon dioxide and water and turn it into sugar and breathable oxygen. We have been adding carbon dioxide to Earth's atmosphere at dangerously high rates, leading to global warming, but could we reverse the process by doing what plants do on some kind of industrial scale?
Why must life metabolize?
The universe is a place that, all other things being equal, tends towards equilibrium, or balance. In other words, molecules and atoms will not spontaneously organize themselves into towers against the pull of gravity – but trees (among other examples) will. Molecules and atoms will not spontaneously organize themselves into highly concentrated solutions of sugars and salts in small droplets of water – but single-celled organisms in a pond will.
Without life, the tendency in nature would be for the towers of trees to fall – as happens when they die. The tendency of solutions inside cells is to disperse – as happens when they die. It is the metabolic processes of the living thing that prevents trees from falling or cells from dissolving. Also, without their towers, or highly concentrated solutions, these organisms cannot reproduce, since reproduction requires particularly delicate chemical processes to all go right in order to work. The organism uses metabolism to create a protected environment for its reproductive chemistry to go forward.
Metabolism is what changes the environment of an organism to allow that organism to live and reproduce. No metabolism, no life!
What is life?
Maybe an odd question for an astrophysics FAQ, but of course it’s a question that we need to answer if we’re going to look for aliens!
It has been surprisingly difficult to get scientists to agree on a universal definition for life; however, in very general terms, most would accept that life must at least 1) reproduce (make copies of itself) and 2) engage in some form of metabolism (cause the conversion of chemicals from one form to another for use by the organism). Wikipedia has a very reasonable discussion on the arguments over the definition of life and offers a more rigorous definition.
