How do you know that Gravity its an attractive force?

All are missing the point of your question, of course.

As you say, "the rules of gravity are based on observations in net effect". That is the unpretentious role of physics. If two distinct ways of describing the world lead to exactly the same observable phenomena, they are classified as different *interpretations* of the same physical theory. Since, by definition, there is no experiment that can favor one over the other, the distinction is considered an epistemically meaningless word game. For the sake of economy some physicists therefore prefer what is called the "null interpretation", where the equation describing what is observed is taken at face value, with no unobservable "mechanism" attributed. Such an interpretation (or lack thereof) is also known as "shut up and calculate".

The specific question alludes to an interpretation of gravity developed for the purpose of avoiding Newton's mysterious "action at a distance" by interpreting is as the effect of momentum transfer from particles which fill all space homogeneously and that travel at arbitrarily high speed in all directions isotropically. These hypothetical particles are absorbed by matter at a rate proportional to mass density, transferring their momentum to it. An isolated object is struck from all directions at the same time so the net force is zero. Place an object next to it, however, and particles coming from the direction of the object are partially blocked. This leads to a force imbalance accelerating the two objects *towards* each other consistent with Newton's inverse square law.

Though equivalent to Newton's Gravity assuming Newtonian Mechanics, it is not equivalent to General Relativity, however, since it cannot describe gravity waves. This, however, misses the main point that to refer to it as an alternative to Newton's gravity is meaningless.

It isn't. It only appears that way. Nicolas has the right idea. The law of gravity is Wrong!!! We've known this for some time now, but we still use it to describe the way objects behave because it's good enough for 99% of the things people are dealing with. Technically you might say gravity is a repulsive force where space pushes masses together.

We do not really know whether gravity is attractive (including Einstein's warping of time/space, which is close enough in effect to include as an attractive force for this discussion) or repulsive. It does seem to be more simplistically instinctive to explain gravity as the counter-balance of centrifugal and attractive forces, but neither Newton nor Einstein said anything about it being an attractive force. I will include whatever quotes I can find that seem relevant to this subject below. The main problem with gravity as attraction is "action at a distance" - this problem is resolved with a repulsive theory. The push force coming from traveling electro-magnetic waves at the upper limits of the frequency spectrum. The shadowing from standing EM wave structures (mass) providing the pull by blocking the push from the illuminated side. To go further into the specifics of this is way beyond the scope of this venue and is fully covered in the link provided below for those knowledgeable and/or curious enough to pursue.

Newton, in a letter to Dr. Bentley: "That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance, through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it."

Einstein, in a letter to M. Besso, 1951 - "All these fifty years of conscious brooding have brought me no nearer to the answer to the question: What are light quanta?"

I think I will leave this at that. Gravity does not really fit a definition of an attractive force nearly as well as it does a repulsive one, specifically EMRP. The attractive definition leaves problems which the repulsive explains (action at a distance/Mercury's orbital anomaly/Pioneer spacecraft orbital anomaly). There is also some ultra cosmic extragalactic radiation that has been, and continues to be, detected that invalidates Einstein's special theory of relativity in the upper limit area of high frequency EM waves, and can be explained as the possible source for this outside (repulsive) force.

J.L.Synge:

"..... Thought is difficult and painful. The difficulties and pain are due to confusion. From time to time, with enormous intellectual effect, someone creates a little order - a small spot of light in the dark sea of confusion. At first we are all dazzled by the light because we are used to living in the darkness. But when we regain our senses and examine the light we find it comes from a farthing candle - the candle of common sense. To change the metaphor, the sages chase their own tails through the ages. A little child says 'Gentlemen, you are chasing your own tails.' The sages gradually lose their angular momentum, and, glancing over their shoulders, see what they are pursuing. But most of them cannot believe what they see, and the tail chasing does not die out until a generation has passed....."

"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former" - Albert Einstein

How would elliptical orbits be explainable using a repulsive force which is being "shielded" by mass? What would be the source of the repulsion? Why would it be different for, say, Jupiter and Earth, and how would you account for the Moon going 'round Earth, and the rings of Saturn and the other gas giants? What about the spherical shape of Earth itself?

========== Edit =============

Actually, Dr. R., not all are missing the point of the question. My pedagogical questions must be answered by anyone suspecting gravity of being an attractive force (including those accepting the possibility of the absorption of carrier particles according to an inverse-square law, by some purported "shielder").

> "what's capability or stress ? i concept it takes capability to have a stress?" In physics, a stress is a push or a pull. you may calculate the quantity of capability expended with the help of a stress with the help of measuring the capability of the stress, how a techniques it strikes the article this is pushing/pulling, and the attitude between the process the stress and the process the article. it incredibly is conceivable to exert a stress with out expending any capability. that takes place in those 2 particular circumstances: Case a million: The stress would not pass the article in any respect. occasion: a ladder leans against a wall. The ladder is pushing on the wall (exerting a stress); however the wall isn't shifting. No paintings is finished; no capability is expended. Case 2: The stress is exerted at precise-angles to the process action. occasion: A ball swinging around a pole on a tether. The tether pulls the ball inward (in a course in direction of the pole; however the ball strikes at precise angles to this stress. No paintings is finished; no capability is expended. > "Does it no longer take capability for gravity to push down...?" No: the gravity (the stress) is there despite if any capability is expended or no longer. Forces can exist for an indefinite quantity of time with out making use of any capability. If the stress would not pass something; or strikes it in basic terms in a perpendicular course; then no capability is needed.

actually gravity is a distortion in space/time think of it like a fabric or sheet, when anything of mass is placed on this fabric it creates a kind of distortion in the sheet or an indent. if you place something else of mass around it, it will fall in towards the large object. no why does this happen and how do we know it does? well there are easy ways to test it, one of which i just said, in this experiment we can see that there is no force pushing them together but a force that because of its mass, pulls it in

Ever since the big bang, some force has been working to bring all the mass and energy of the universe back together where it was. This force is known to us as gravity. When all the mass and energy of our whole universe is drawn together and contained within only one black hole, something wonderful happens.

Because gravity pulls you. Try throwing something it will drop in ground. It means ground has gravity it attracts anything. It is an attractive force.

Well one of the most obvious signs is that wherever u r on the earth u fall towards the earth. Like if u r in antartica u dont fly down into space. And our planet gets saved from meteors by the meteor getting to close to another planet and starts going towards it.

Why know the affects of gravity, not what it is, i.e. why its there in the first place. Rotating mass at attomic level to planet level?

We can measure foirce though, or can we?