Is gravity a theory or a law? In other words, what is preventing us from...?

Question

In other words, what is preventing us from removing any shadow of a doubt regarding it such that we can drop the word 'theory' from the equation?

Answer 1

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Everything becomes clear if you assign their proper meanings to words like "theory", "law" etc. in a scientific context. In particular "theory" is not an insult (as in the silly saying "it's just a theory"). A theory is simply the most elaborate form of consistent scientific knowledge not yet disproved by experiment. In experimental sciences, a theory can never be "proved", it can only be "disproved" by experiment. This is precisely was makes a theory scientific. A statement that cannot be disproved by experiment may still be highly respectable but it's simply not part of any experimental science (it could be mathematics, philosophy or religion, but it's not physics). Now that we have the basic vocabulary straight, we may discuss gravity itself:

Gravity is a physical phenomenon which is obvious all around us.

As such, it's begging for a scientific theory to describe it accurately and consistently. The rules within a theory are called "laws" and the inverse square law of the Newtonian theory of gravitation does describe gravity extremely well. Loosely stated:

"Two things always attract in direct proportion of their masses and in inverse proportion of the square of the distance between them."

However, the Newtonian theory does not provide the ultimate law for gravity. We do know that General Relativity (GR) provides more accurate experimental predictions in extreme conditions (e.g., a residual discrepancy in the motion of the perihelion of Mercury is not explained by Newtonian theory but is accounted for by GR).

Does this mean Newtonian theory is "wrong"? Of course not. Until we have a "theory of everything" (if such a thing exist) ANY physical theory has its range of applicability where its predications are accurate at a stated level of precision (stating the precision is VERY important in Science; an experimental prediction is MEANINGLESS if it does not come with a margin for error). The Newtonian theory is darn good at predicting the motion of planets within the Solar System to many decimal places... That's all we ask of it and that's what makes it so valuable.

Even General Relativity is certainly NOT the ultimate theory of gravitation. We know that much because GR is a "classical" theory, as opposed to a "quantum" theory. So, GR is not mathematically compatible with quantum phenomena which become obvious at very small scales...

Science is just a succession of better and better approximations. This is what makes it nice and exciting. If you were to insist at all times on "the whole truth and nothing but the truth" in a scientific context, you'd never be able to make any meaningful statement (unless accompanied by the relevant "margin for error"). As a consistent body of knowledge, each theory allows you to make such statements freely, knowing simply that the validity of your discourse is only restricted by the general conditions of applicability of a particular theory. Without such a framework, scientific discourse would be crippled into utter uselessness...

I humbly hope this helps clarify things a little.

Source(s):

http://www.numericana.com/answer/physics…

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Thanks for taking the time to explain this in such detail. Very informative and helpful!

Answer 2

Gravity is considered fact - it is a characteristic of mass to attract other mass, and Newton's Law of Gravitation applies where the masses are appreciably further apart than the size of the masses. There are theories of gravity waves and the interaction of gravity with other forces.

Answer 3

It's a scientific law.

Answer 4

The universe is what it is. You can say that gravity is just a theory and has never been proven, but it will not make it any easier to climb 30 stories using the stairs.

What is gravity, really? Well, it's just a word. The word is associated with a theory, and the theory tries to describe an apparent pattern in the way the universe works. The universe, of course, does not care about mathematics and science. It continues functioning in the same way it always has.

If the concept of "down" exists, then there is obviously something there causing one direction to be preferred over all others. We name it "gravity". The equation

g = G * m / r^2

describes the gravitational field around an object. If the equation predicted a certain gravitational field, and we did an experiment to test it, we would be very surprised if we didn't get the result predicted by theory. The theory matches reality so perfectly that we may as well call it a law. Of course, humans have no dominion over the laws of nature, but our best guess seems to be accurate in this case.