And both forces are directly proportional to the sources themselves
But there are two very significant differences.
- First, mass comes in only one "type", which means that every mass attracts all other masses. (Mathematically, it would be just as meaningful for all masses to repel one another, but we wouldn't be here to wonder why.)
Charge comes in two types, positive and negative. The existence of two types of charge means that charges can either attract or repel one another. In this week's lab, you will perform a series experiments that will confirm the rule that "like charges" repel and "unlike charges" attract.
- Second, the gravitational force is so weak that it becomes significant only when very large mass is involved. This is important to how our universe is structured. The gravitational force between two people is nearly undetectable, but the earth holds us to its surface and the earth orbits the sun.
The electrical force, on the other hand, is very strong. It can hold matter together at the small scale, but large charge separations cannot be easily maintained. There is a great tendency for objects with opposite charge to "neutralize" one another.
Here's the puzzle:
Consider the possiblility of a parallel (or perhaps orthogonal) Universe, also with two distinct charges, but one in which like charges attract and unlike charges repel. The top picture shows a hydrogen atom from our Universe, in which the positive proton attracts a negative electron. The lower picture shows a positive proton attracting a positive electron in the parallel Universe. (Incidently, positive electrons can be created in our Universe. They are a form of anti-matter called positrons.) Would the parallel Universe be different from ours if this were the only difference? Explain your reasoning, giving an example of how nature would or would not be different.