Why are they all brooms?

Because the center of gravity of the broom is closer to the bottom broom hair than the high point of the broom handle. You can try to put the broom across your fingers, just like a seesaw, to test the center of gravity of the broom.

So when you split the broom hair, the center of gravity is naturally close to the bottom, and it is not difficult to find a stable point. If the broom is new and the broom hair is straight and hard, it will be easier to support this center of gravity.

Because everything falls, because the center of gravity has no support. As long as the center of gravity is supported, all problems will be solved.

Many people say that it is the influence of space, but it has little influence on space. Wired magazine in the United States once calculated. The gravity (10-8 N) exerted on the broom by Venus, which is closest to the earth, and Jupiter, which is the most massive in the solar system, is far less than the gravity of the earth (about 10N), so it is impossible to make the broom stand upright.