Joseph Spinosi, age 10, of Baden, Pennsylvania, for his question:

What causes gravity?

This is the Age of Science and science probes for causes, the factors that: make other things happen. Sooner or later, you would think, a probe must lead back to a first cause that started all the others. Sometimes this turns out to be true. Light is one of these first causes that starts a lot of other causes on their way. We call it a phenomenon. But most scientific investigations do not lead back to one first cause. As a rule, things are caused by the meeting and interaction of several factors.

Gravity is a strange force because it is not caused by anything. It is a built in quality, or property, of matter. Every speck of matter in the universe has its exact quota of gravity. Wetness is a property of liquid water. Gravity is a property of all matter solids, liquids and gases. The mass of an object is the amount of matter or material packed into its size, or volume. And the quota of gravity allotted to an object depends upon its mass and its volume. The gravity in a speck of dust is a mere wisp. compared with the gravity of the massive earth but even the speck of dust has its built in property of gravity.