Joseph Ciuffo, age 11, of Somerset, N.J. , for his question:
HOW WERE THE PLANETS FORMED?
Nobody was there to take notes on the birth of the solar system, so scientists had to piece the story together from indirect evidence. Nowadays, most experts agree on how and when the planets were formed. It seems most likely that all nine planets were born at the same time, and the stupendous event also included the birth of the sun.
In the 1660s a learned person announced that our world was created in the year 4001 B.C. The whole thing was completed, he stated, at 9 a. m. on Oct. 23 which was a Sunday. Nowadays, such a statement sounds ridiculous. After all, our patient scientists have gathered masses of evidence that prove that the earth has been in existence much longer than this. Fossil dinosaur bones date back 100 million years, and certain rocks are older than 3 billion years.
All sorts of other evidence was gathered to trace back the story of the planet earth to its very beginnings. All the known facts suggest that the whole thing started perhaps 6 billion years ago when an enormous cloud of dusty cosmic gases began to shrink and condense. In time it formed a flat saucer, and the saucer started to rotate.
Most of the material in the original cloud condensed to form a massive ball in the center. Smaller amounts formed circles around it, one outside another. The ball in the middle was destined to become our sun. The material in the rings was destined to become the nine orbiting planets.
The material in the rings swirled around, and chunks of matter collided and clung together. Gradually most of the material in each ring joined together to form a planet with perhaps one or more small moons. So far, the formation of the future planets took place with light only from the faraway stars.
However, the future sun in the center condensed until it became hot enough to start the process of nuclear fusion. In this fiery furnace, particles of matter were converted into radiant energies. Then the first great day arrived. The sun lit up in a blaze of glory, shedding light and warmth on its orbiting planets.
Most experts suspect that the early stages of planet formation happened rather quickly, perhaps within a few hundred million years. In any case, it seems likely that about 5 billion years ago the planets already were formed and circling their orbital paths around the dazzling sun. It also seems likely that most of the other starry suns may have given birth to families of planets.