What uses gravity to function?

Answer 1

Gravity is the engine that drives the universe.

We don't know what caused the big bang 13.7 billion years ago, but after it happened the first stars and planets were formed by the action of gravity.

Gravity created the stars and planets and put them into there orbits. The huge pressure of gravity creates fusion at the core of a star. Planets like Jupiter are gas giants that were just a little too small to ignite into a star.

All the planets and stars are collected into galaxies which formed because of the attraction of gravity. Many of them, like the Milky Way (our galaxy) have a super massive black hole in the middle of them.

As a star runs its fusion process it burns out its fuel converting it to larger elements which is burned as well. This keep happening until the star tries to burn iron. At that point it has swelled to the size of a red star and if it is larger enough (4 times the size of the sun) it can explode in a super nova or a nova creating larger elements. We are all star stuff.

Now in engineering gravity is used to operate simple machines; like an inclined plane. A draw bridge can be opened by dropping a counterweight that is heavier than the bridge and then lifts it. Or it can be used to slowly drop the bridge; either way the counterweight has to be cranked back up to the top for it to function again.

A lot of ancient machines used water pressure to operate and that was all gravity driven. One machine made for a temple had Hercules shooting a dragon. When the bow was fired it lifted a conical plug in the base of a hidden water tank. The water drained into a sealed tank; with a thin pipe that lead to the dragon's mouth. As the water came down it pushed out the air making a reed vibrate (inside of the dragon) and the dragon seemed to roar. This was a clever use of simple machinery to awe the crowds and make it look like a miracle had happened.

Today we use engines to do most of our work, but a pendulum clock like Big Ben still uses gravity to function. We use gravity in other areas to operate simple machinery. The flow of water that powers a hydroelectric dam is all gravity driven. This was the major source of power for a long part of human history; not just electrical but mechanical.

So which item were you asking about: how do machines use gravity to function or how does the universe use gravity to function? Or were you asking what gravity is?

Answer 2

Everything in our environment requires gravity to function in a useful and normal manner, because if everything were weightless everything would pretty much be just floating around uselessly. Humans and all living creatures also need gravity to function normally, without flying off into space.
Without gravity our air would fill up with human and animal bodily waste materials, and then we would have an environmental problem worse than global warming.
We would all need to buy waste product credits from Al Gore.

Answer 3

Elevators when they are going down. Bombs when they leave an airplane and drop down. Highways that are banked on curves. Hawks when they accelerate for diving on prey.