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I was taught Gravity is a predictable force and Newton's Law of Gravitation reads as below:
Every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them.
The formula is:
Mathematically, this translates into the force equation shown to the right. In this equation, the quantities are defined as:What is theoretical about gravity from a Newtonian perspective?
- F<sub>g</sub> = The force of gravity (typically in newtons)
- G = The gravitational constant, which adds the proper level of proportionality to the equation. The value of G is 6.67259 x 10<sup>-11</sup> N * m<sup>2</sup> / kg<sup>2</sup>, although the value will change if other units are being used.
- m<sub>1</sub> & m<sub>1</sub> = The masses of the two particles (typically in kilograms)
- r = The straight-line distance between the two particles (typically in meters)
http://www.phy6.org/stargaze/Sgravity.htm
That the cause of the Moon's motion is the force known as "gravity" is a Theory. A very, very, very well-supported Theory. It is also a Theory that this effect is constant universe-wide.
As to just exactly what gravity is, that's another theory. Lowercase "t" because our empirical proofs for gravity exerting a warping effect on spacetime itself are in their infancy, being as we are in the middle of an overwhelming gravity well where it's hard to isolate a specific effect from outside influence.
So, like evolution, gravity is a fact, a Theory and a theory. (given that we agree to call "whatever invisible force it is that causes hammers to fall", gravity)
The continuing (sometimes willful) confusion about this is just another snowball on the Everest of evidence that science education in America needs to be broadened and improved, not dumbed-down.
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