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

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.

Answer 2

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.

Answer 3

Theory Of Gravity

Answer 4

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 5

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IMHO it's Newton's theory of classical physics but only Newton's law of gravitation. What Newton gave us was a framework in which to calculate the dynamics of moving bodies. This framework is still perfectly valid for slowly moving objects (relative to c) in weak gravity fields (with Schwarzschild radii of gravitating masses much smaller than orbital radii). I wouldn't call his gravitational potential a theory because there is just not enough there besides the formula. Planetary orbits follow more or less trivially if you plug the potential into his theory of mechanics. Classical physics as formulated by Newton is very rich. Much more so than one would suspect from high school physics. If you add in all of Lagrange's formalism and Hamilton and Noether's symmetries and all the solutions for important problems, you can fill a whole shelf in the library just with the most important results. That's about the scope of a typical small theory of the 18th or 19th century: a bookshelf full of books to spell out the basic and explore the consequences. A modern theory like quantum field theory fills many shelves just with the basics and huge libraries full of computer tapes with the necessary experimental data. A law, in general, is just a tiny result of a theory. Some laws can be used to axiomatically define a theory, but that is a slippery problem. The laws of conservation of energy and momentum, for instance follow mathematically from the structure of mechanics under additional symmetry assumptions and are not particularly fundamental (one can easily formulate non-conserving problems in the language of Newtonian mechanics and every mechanical engineer does so all the time). That they are not fundamental to physics can also be seen in the continued interest to test them experimentally... if they were set in stone we wouldn't bother. But they aren't! That we teach them as laws to our kids in high school is to make it easier to remember, not because it is logically more stringent. The better way would be to start with symmetries and progress from there to conservation laws, but then the number of students graduating would probably drop from 50% to less than 5%.... Evolution, on the other hand, has nothing to do with any of this. Evolution is an observed fact in descriptive biology, not a law to structure a certain aspect of a mathematically well defined theory. You can see it in a petri dish and pretty much any eco-system, IF you are willing to explore the living world. All it takes are open eyes to see it all around you. And what makes you think that a hard core creationist will ever shut up just because you arbitrarily re-define a word with an already perfectly clear meaning (to those who have real need for and exposure to it)? A late 19th century religious delusion which is perpetuated as a political platform for right wing political purposes does not capitulate to rational and certainly not to wishful thinking. It is simply a matter of politics and law to keep these people in check and to prevent them from spewing their poison into our schools. Socrates died in defense of rational thinking over irrational power some 2400 years ago. Creationists are nothing but hopelessly uneducated people dancing on his grave who are misled by hopelessly ruthless high priests of ignorance.

Answer 6

Gravity is a field generated by vibrating dipoles. These vibrations have been decaying(slowing down) because they radiate continuously. The cosmic background radiation is not left over from the big bang. It is the radiation from decaying gravity. To understand it, you need to know the structure of fundamental particles. To start I suggest you start here.
http://www.commonsensescience.org/spinning_ring.html

Answer 7

It's a scientific law.

Answer 8

a frog with no legs cannot hear

Answer 9

Idiot