Bill Grays age 12, of Williamsport, Pennsylvania, for his question:

Will the Big Dipper ever change?

The two pointer stars in the Big Dipper have shown the direction to Polaris, the North Pole Star, for thousands of years. We can depend on these pointer Stars throughout our lives and for several thousand years to come. But suppose we could study our sky 100,000 years from now. The Big Dipper gill not look like itself at all. The two pointer stars will be pointed towards some spot in the eastern part of the sky.

The Big Dipper is slowly, slowly changing. Each of the seven mayor stars is moving in a slightly different direction. The change is so slight that we will notice no change in 100 years. But, after 100,000 years our old Big Dipper will be pulled all out of shape.

Take the two stars at the bottom of the bowl. They are moving up and toward the handle. The bowl of the Big Dipper is slowly getting shallower. The first three stars in the handle are gradually moving away from the bowl, one behind she other. So this part of the handle is slowly growing longer.

The fourth and last big star in the handle of our Big Dipper tips down to make a curve in the handle. This star is moving to make an even sharper curve. In 100,000 years it will be almost directly under the third big star in the handle.

The two pointer stars are moving in opposite directions and here the change will be most noticeable. The lip of the Big Dipper is gradually failing down, The Big Dipper of the future may still look like a dipper but it will be completely changed around. What is now the handle will be the bowl, what is now the bowl will serve as a handle. And, of course, the whole picture will be upside down.

By this tame most of the other constellations also will have changed. actually, the stars we see from the earth are moving about at tremendous speeds. We do not notice their changing positions because they are such immense distances away. They also are separated from each other by vast oceans of  space.

The stars in a constellation seem to us to be next door neighbors. But this is not so at all. One bright star may be 50 light years away from us. Beside it we see another bright star which looks like a twin. But this second star .nay be 300 light years beyond the first star. And the two of them may be traveling in different directions.

All the stars we see are part of a huge system called the Galaxy. The Galaxy is shaped like a cartwheel and, like a cartwheels turns around and around. Stars near the center correspond to the hub of a wheel. Stars near the edge correspond to the wheel's rim. As the big wheel turns the stars of the vast system must move arc different speeds and in different directions. And so the constellations we see from earth get twisted out of shape,