Raymond B. answered • 12/26/20
Math, microeconomics or criminal justice
the density of the balloon (overall, the rubber & the air inside the balloon) exceeds the density of the air outside the balloon. Unless it's filled with helium, then it doesn't get pulled down by gravity
A hot air balloon also will rise, not fall, even though the rubber in the balloon would seem to make it denser than the air outside. But hot air rises, because it i less dense than cold air.
Gravity exerts a downward force on everything, but the cooler air is pulled down more than the hotter air or objects less dense than the cooler air.
It's the same with water as the median. If you are denser than the water, you sink, you get pulled down by gravity to the bottom of the water. But if you are lighter than water, or are on an inflated life jacket or float, you float.
Newton getting hit on his head by an apple falling out of a tree is the popular theory of gravity. It's a special case of Einstein's relativity to postulates gravity waves and gravitons, massless particles like photons of light.
Black holes are so dense the exert a force of gravity that pulls to them even light. They called black holes because you can't see them, as all light is pulled by gravity inward. The median there is not air or water, but a vacuum which has zero density. Everything is denser no matter how light and gets pulled "downward" (inward to the center of the Black Hole.
The Big Bang, the beginning of space and time is considered to be infinitely dense, yet it exploded sending its particles outward. Gravity didn't overcome the outward force. This suggests an antigravity force, such as from dark energy which may pervade the universe
Another wrinkle is Dr. Verlinde. He and his brother at Princeton argue that gravity is an "illusion." Newton had his "spooky" action at a distance (how can gravity act without a median and no connection?) Einstein then argued gravity is a result of geometry, a warp in the time space continuum, and that space is curved.
The Verlinde professors go further, arguing against Einstein & Newton, claiming quantum physics and string theory lead to a different view of gravity, that it is not a fundamental force of nature, but rather a result of entropy. Dirac argues the "force" of gravity varies throughout the universe. It is not a constant. Not many scientists even understand the Verlinde view, but if the universe is comprised at the quantum level of endless strings, it may lead to a very different concept of gravity.
Electricity, magnetism, the weak and strong nuclear forces have all been explained as variants of the same overall forces, but not gravity. It remains more mysterious than scientists admit. They usually try to "dumb down" their theories for popular acceptance.
