Stanley Green, age 8, of Winston Salem, N.C., for his question:
WHAT MAKES THE EARTH TURN?
Earth is just one tiny part of our vast universe. Each individual unit in the mammoth network has its own pattern of movement which seems to be controlled by a divine power that is unknown to man.
Earth has three motions. First of all, it spins like a pop. Then it travels around the sun. And finally it moves through the Milky Way galaxy with the rest of the solar system.
Earth spins around its own axis once every 24 hours, making a day. Next, it travels around the sun once every 365 days. And it moves with the sun as it circles the center of the Milky Way once every 200 million years.
What makes the earth turn? Most scientists can explain how it's done but admit that an unknown, unexplained power controls the miracle.
When a botanist talks about the trees in this group, he refers to them as needleleaf trees.
Most important forest tree in North America until about 1890 was the eastern pine which still grows from Minnesota to Maine and from Canada to the mountains of Georgia. Although all of the virgin stands of this great tree were cut down by the end of the last century, it is still widely planted for timber and for ornamental purposes. Its slender needles grow in bundles of five.
Largest of the pines is the sugar pine. It can go as high as 250 feet and has a trunk that is 10 feet in diameter. It grows in the mountains of California and Oregon.
Among the world's oldest trees is the bristlecone pine. Found in the mountain areas of the southwestern part of the United States, scientists say some of the trees are more than 4,600 years old.
Northeastern hard pines include the red pine, the jack pine and the pitch pine. Twp or three stiff, long needles grow in clusters. These trees are used for lumber and pulp.
The southern hard pine, often called the yellow pine, includes four types which grow from South Carolina to Louisiana and from New Jersey to Texas. They provide turpentine and resin.
The western hard pines include the ponderosa, Jeffrey and lodgepole pines. The ponderosa's needles grow to 10 inches long and cluster in groups of two or three. These trees are among the most important lumber producers in the United States today. They can be found from Montana and Yellowstone National Park to the Sierra Nevada Mountains.
Needle leaf trees reproduce by means of sex organs in their flowers. Pollen from male organs produces sperms which unite with eggs in female organs. This union, which is called fertilization, produces seeds. The seeds grow inside pine cones.
Wind carries the pollen from the male flowers to the scales of the female flower. When the seeds are finally ripened, they are ready to leave the tree. The pine cone pops open and the wind scatters the wing like seeds far and wide.