Kenneth Kaye, age 11, of Toronto, Ontario, Canada, for his question:
What are Saturn's rinds made of Rewrite required
This story goes to show that even the most scholarly astronomers have to change their minds. Lately this has happened quite often as space probes sent back close up information from our neighboring planets. For example, the Martian landscape is not a flat, featureless desert. Giant Jupiter is not colder than cold. However, the latest information on Saturn's rings was gathered not by spacecraft, but long range radar, beamed from California's Mojave Desert.
A few years ago, most astronomers agreed that Saturns rings must be made from tiny particles, most likely of ice and dusty gases. They had good reasons to believe this was so. But in December of 1972, the popular theory was blown sky high by a NASA 210 foot radar antenna. Using a 400 kilowatt radar beam, it bounced back signals from Saturn's rings. And we now know that these dazzling golden circles are made of sizeable chunks.
The beams left the Goldstone station in California, bounced back from Saturn and their signals came back to home base in two hours and 15 minutes. The experiment was made 12 times and each round trip was one and a half billion miles. The results were full of surprises.
Radar signals echo back their signals from solid surfaces. No radar echoes returned from the planet itself. This suggests that Saturn's surface is a mass of gases, which is what everybody thought. Had the rings been made of small particles, they would have returned weak signals or none at all. Instead, they were five times stronger than,they would be from Venus, if Venus were at that distance.
When the amazing signals were analyzed, astronomers learned that those glorious, mysterious rings are made from chunks and boulders, ranging from one to three yards wide and possibly wider. In countless numbers they orbit around the big hazy planet, reflecting sunlight like a swary of golden bees.
At present, astronomers speculate that most of the sparkling chunks may be made from ordinary ice. Perhaps they contain other frozen gases and maybe an assortment of minerals. But for these particulars, we most likely must wait until the spring of 1981. This is when a Mariner spacecraft is scheduled to pass by Saturn and relay close up scientific evidence back to Earth.
Now, little Mariner will be programmed to stay more than 85,000 miles from the surface of Saturn at a safe distance beyond the outer limit of those chunky rings.
The famous rings were photographed and measured in the 1800s. One of the three rings appeared to.be made of sizeable chunks. But according to the laws of physics, solid or fluid rings would come crashing down to the planet. This is why most astronomers assumed that they must be made from tiny particles. Maybe some of them do fall. But most of them overcome the laws of gravity by orbiting fast enough to stay in whirling formation.
Sandy Eged, age 11, of Niagara Falls, Ontario, Canada, for her question:
How much does the earth weigh?
The planet Earth, including everything, weighs 6.6 sextillion tons, or thereabouts. Now where in earth did they find a weighing machine to weigh the whole world, and everything in it? A very clever one was invented for the job, by the English physicist Henry Cavendish.
Henry Cavendish was the first person to weigh the world, way back in 1798. He solved the impossible problem by using the universal laws of gravitation, discovered by the great Isaac Newton. The elaborate apparatus used a contraption of round balls to measure the pull of the earth's gravity. Gravity is related to mass and weight. The experiment has been repeated many times. And in nice round figures, the number of tons in the total weight of the earth comes out as 6,600 followed by 18 zeros or thereabouts.