What’s down with gravity?
I said down because things fall down, not up. That’s a joke!
Legend has it that the English mathematician, Sir Isaac Newton, discovered gravity when an apple fell on his head. I’m sure he also said a few Church words when that happened. Seriously, this event supposedly led to his developing his law of universal gravitation, which he published in 1687 in the now famous book ‘Philosophiae Naturalis Principia Mathematica’. In this book he presents his equation for gravity that says that the gravitational force is proportional to the product of the two masses where F the force between the two masses is equal to G the gravitational constant times the first mass times the second mass dived by r squared the distance between the centers of the masses. NASA still uses Newton’s law of motion and gravitation to plot out the course of their space ships and probes.
G, the gravitational constant is an empirical physical constant equal to 6.673X10 to the - 11 meters cubed per kilograms per second squared.
However, no one, even Newton, knew how gravity works. That was until a German Jewish physicist by the name of Albert Einstein changed everything when he came up with his General Relativity theory, this after Newton’s law of gravitation had been accepted for nearly a hundred years. Simply put, Einstein threw out the idea of gravitation being an attractive force between two masses as Newton had said and tied gravity to the bending of space by a mass, showing that the larger the mass the greater the bending effect. It’s as if a mass causes space to bend around it much like a heavy object on a sheet held firm would cause a dip. Things near this dip would spiral down into the gravity well caused by the mass. He went on to say that motion keeps the planets from spiraling into the sun. The planet must move around a massive object with enough velocity to cancel out the object’s bending of space, but no matter what, the planet is always falling. It just never gets there because it’s curving out of the way.
At the time Einstein proposed this crazy idea in 1915, he was ridiculed.
How the hell can an object bend space? Space is a vacuum.
Einstein explained that space is like a fabric that can be bent, twisted and stretched. At the time, Einstein managed to confuse many who could not grasp his new theory. His formula was esoteric and involved a term that is called Einstein’s tensor and is calculated by the equation where G a measure of curvature of spacetime geometry is equal to eight times pi times small G the gravitational constant over c the speed of light to the fourth power and all that times T a measure of matter content. This equation has some interesting consequences. One that I find wild is the fact that Newton predicted that a planet orbiting a star would follow an ellipse. Einstein’s equations show the same thing but that the ellipse would rotate slowly around the star. His idea was verified for the planet Mercury.
The definitive verification of Einstein’s relativity occurred when Arthur Eddington measured the bending of the light from a star near the disk of the sun during a total eclipse of the sun in 1919.
It’s obvious now that gravity is not just influenced by mass. There is an energy component associated with mass because of Einstein’s special relativity equation E=M times C squared that links mass and energy and this has something to do with the bending of space, which has an energy component associated with it.
It’s amazing how Einstein’s ideas have become so legitimate now. All I can say is thank God that he didn’t fall victim to the Nazi’s. That would have been a terrible human loss as well as a great loss to science.
Thanks for reading.