Karen Mathews, ace 12, of Portland, P`aine, for her question:

Will we ever find another livable planet?

This is very likely to happen, but not in the near future. From what we know at present, the other planets of our Solar System are unfriendly toward the sort of living, things we are used to on the earth. But scientists are becoming more and more convinced that ours is not the only solar system in the universe. Somewhere across the enormous oceans of space there are bound to be other livable planets suitable for earthlings. But the search for them must wait until we master long distance space travel.

Let's recall the several factors that make the earth livable, that is from our point of view. Our bodies are accustomed to its size and gravity and built to withstand so more solar heat, which depends to some extent on our distance from the sun. We are used to a planet with oceans of water, a lot of weathery air and a special upper atmosphere to shield us from certain solar radiations. We also depend upon certain ratios of crustal minerals and a very precise mixture of gases in our breatheable air.

In order to be livable from our point of view, another planet would have to match these basic requirements. The larger and smaller planets of our own Solar System, could not qualify because, for one thin, they orbit at different distances from the sun. Various factors make their atmospheres and also their water supplies, if any, unsuitable.

Obviously, we shall have to seek farther afield to find a planet to match our matchless earth. And farther afield means beyond Neptune~Pluto and the masses of meteors that orbit around the outer rim of our Solar System. From here to there is somewhat more than 3,500 million miles  or about 100,000 times longer than a voyage to the moon. At the edge of the Solar System, we are at the shores of the vast ocean of outer space.

In every direction there are stars, separated by enormous distances that make our lunar voyages look like Grasshopper Jumps. Here we measure distance in light years, each one actual to about six million million earth miles. Over that way, at a distance of 4.4 light years, is Alpha Centauri, our sun's closest neighbor. Some 6.6 light years in another direction is another near neighbor, Sirius, the dazzling Dog Star.

Other starry suns in our corner of the universe are 100, 200 and even 300 or more light years away. Even if tae could reach them, what are the chances of finding ones that have planets? Astronomers suspect that most of the 100 billion stars in our Galaxy may have families of orbiting planets. Almost certainly, here and there we would find another solar system that has one livable earth type planet.

The search seems hopeless, but let's not save up hope. In 1940, a flight to the moon was considered ridiculous and few of any young persons found spaceships under The Tree. Now our lunar landings are part of history and a spacecraft landing on Mars occurred in 1976. It may take mankind 1,000 years to become mariners of outer space. But make no mistake about it, we are on our way.