[SCIENCE WORLD]Kids' rooms aside, life is order

In the 1960s, the U.S. National Aeronautics and Space Administration, NASA, made plans to look for life on Mars. James Lovelock, a British chemist who participated in the project, began to ask himself how life could be recognized and what life is. If an organism that is completely incomprehensible to us were to be found on Mars, should the organism be regarded as life or not? The first problem for the project, he decided, was to develop a definition of "life." Biologists, he found, had no satisfactory definition so he began his own quest to define life.

After great effort, Mr. Lovelock concluded that life is the state of disequilibrium. In other words, it is a state of low entropy. For example, if a living thing has a temperature that is different from the temperature of its surroundings, the difference indicates that the living thing is in disequilibrium with its surroundings. A sand castle on a beach is also in disequilibrium. Left alone, the sand castle will gradually crumble into the same state as the beach. Biological workings require energy from food in order to maintain their disequilibrium.

Such disequilibrium contains more information than equilibrium. We can guess how much information a living thing contains, considering that cells and organs in a human body work on a system of mutual dependence. Entropy is the equivalent of "no information." Accordingly, a state of disequilibrium with a great deal of information is a state of low entropy. Mr. Lovelock defined life as the generation of low entropy through the use of energy.

Then he began to realize that the Earth is a huge life form itself, because the whole Earth is in dis-equilibrium in other words, it is low in entropy. If a planet is lifeless, its atmosphere would be close to equilibrium, but the atmosphere of the Earth is far from equilibrium. On Earth, the air includes abundant oxygen that did not exist in the primitive atmosphere here and does not exist in the atmospheres of other planets. The current atmosphere of the Earth was not original to the planet, but was manipulated on a day-to-day basis by life on the surface for 4 billion years. The current atmosphere of the Earth keeps the percentage of oxygen at 21 percent, the most suitable percentage for life forms on Earth. The persistence of disequilibrium means that an autonomous adjustment system is operating. Mr. Lovelock discovered such a system in several phenomena, including the composition of the Earth's atmosphere and the Earth's temperature. So he concluded that the Earth is a living entity involving the biosphere, atmosphere, oceans, and soil; the totality is a feedback or cybernetic system which seeks an optimal physical and chemical environment for life on the planet. He called this theory "Gaia," after the goddess of the earth in Greek myth.

Superficially, the Earth seems to have nothing to do with the biosphere. But the Gaia theory says they are intimately related. Living creatures do not live on a planet named Earth by just adapting themselves to the environment. They change the Earth and have active mutual relations with the Earth. The living creatures and the Earth are not separate, but one.

The writer is a professor of physics at Korea University

by Yang Hyeong-jin