Gene Barrett, age 15, of Bristow, Oklahoma, for his question:

How far does the Universe extend?

Suppose we were told that the Universe extends a trillion¬trillion lightyears, or some other precise distance from the earth. Naturally our next question would be, "What's outside the boundary?". Obviously our human minds cannot grasp the concept of a Universe that includes everything. When we accept this human limitation, it is a good idea to bring our thoughts back home and survey the vast expanse that lies within our range.

Our local universe is a wheeling galaxy of more than 100 million stars, plus enormous clouds of dusty gases. Its diameter extends about 100,000 lightyears, which means that traveling at an average speed of 186,000 miles per second we could cross from side to side in about 100,000 earth years. Huge as it is, our island universe is but a small backyard in the total universe called the cosmos.

So far as we know, the cosmic universe is endless and infinite. Since it includes everything, naturally it includes whatever is beyond the range of our most powerful telescopes and radio telescopes. Recently a quaser was identified at a distance of 12 billion light years, this seems to be the limit of the known universe    at this time.

Astronomers have probed this range in every direction. And distributed in all directions they have found about a thousand million galaxies, somewhat similar to our own wheeling home in the heavens. Most of them seem to be separated by vast oceans of space    and all of them seem to be racing at tremendous speeds.

Since every galaxy contains incandescent gases, it reveals a spectrum of rainbow colors. Such a spectrum reveals the nature of the burning gases and also whether the celestial object is approaching or receding from the earth. The spectrum is a chart of assorted wavelengths and when the distance between us and a heavenly object is changing, these wavelengths are shifted.

If the object is moving away from us, the wavelengths are increased and their lines shifted toward the red end of the spectrum. If the object is moving toward us, the wavelengths decrease and shift to the blue end of the spectrum. These red shifts and blue shifts give astronomers the key to how the distant galaxies are moving in relation to the earth.

It seems logical to assume that the thousand million galaxies in the known universe either stay in their places or mull around in haphazard directions. Not at all. Based on the evidence we have at the present time all the galaxies in every direction seem to be moving away from us and from each other.

Apparently the stupendous universe is expanding, or perhaps exploding at fantastic speeds in all directions. This theory' is stunning enough to boggle the brain    but at present we have no evidence to contradict it. Some astronomers suggest that perhaps the mighty cosmos has built in forces that cause it to expand, contract and then expand again. But at present, nobody can prove this theory either.