It may be hard to believe that the cause of gravity continues to remain one of the great mysteries of science, even to this day. This article will briefly explore our understanding of gravity.

We are all familiar with the effects of gravity. The story of Newton being hit on the head by an apple leading to his discovery of gravity is often taught to school children. In short, gravity is a natural phenomenon by which all physical bodies attract each other. For example, the Earth attracts you and keeps you grounded. When you weigh yourself, you are actually measuring the effect gravity has on your body. Although this seems obvious, science still continues to debate what causes gravity.

In 1687, English mathematician Sir Isaac Newton published *Principia and wrote, “ “I deduced that the forces which keep the planets in their orbs must [be] reciprocally as the squares of their distances from the centers about which they revolve: and thereby compared the force requisite to keep the Moon in her Orb with the force of gravity at the surface of the Earth; and found them answer pretty nearly.” *This became known as Newton’s inverse square law of gravity. Although Newton was unable to define the exact nature of the gravitational force, Newton’s law of universal gravitation became widely accepted right up to the beginning of the 20th century. It is often taught in high school science classes and for most applications is a good approximation regarding the behavior of gravity.

In 1915, Einstein published his theory of gravity within the framework of his now famous theory of general relativity. According to general relativity, the effects of gravitation are caused by a spacetime curvature and not a force, as Newton had asserted. Einstein’s theory of general relativity was able to successfully account for several effects that were unexplained by Newton’s law, such as the anomalies in the orbits of Mercury. Einstein’s theory of general relativity proposed that spacetime is curved by matter, and that free-falling objects are moving along locally straight paths, called geodesics, in curved spacetime. A simple way to think about this is to think about a drum. Now think about pushing down in the center of the drum. This would cause the entire surface of the drum to become concave (i.e., curve inward). If you drop a marble on the drum, it will fall to the center due to the inward curvature of the drum’s surface. Although Einstein general theory of relativity is now a corner stone of modern physics, especially astrophysics, it still did not explain fundamentally why or how matter curves space, which still left the nature of gravitation a mystery. On a side note, while general relativity predicted numerous phenomena, such as gravitational lensing (i.e., the bending of light by a large mass) and an effect of gravity on time known as gravitational time dilation (i.e., the slowing down of “clock” in a strong gravitational field), it was incompatible with the highly successful theory of quantum mechanics, which describes the behavior of atoms and subatomic particles.

Where does all this leave us? Currently, there is no widely accepted theory on the fundamental nature of gravity. However, there is no lack of proposed theories. The one that appears to have the most support is string theory. M-theory is the most comprehensive formulation of string theory. In general, M-theory asserts that the fundamental building blocks of all matter can be reduced to infinitely small building blocks of vibrating energy, having only the dimension of length, termed “stings.” Conceptually, the “strings” vibrate in multiple dimensions. The vibration of the string determines whether it appears as matter or energy. According to string theory, every form of matter or energy is the result of the string’s vibration. In addition, M-theory predicts there are eleven dimensions, ten spacial and one temporal, as opposed to the four dimensions implicitly predicted by relativity and quantum mechanics. One of the attractions of string theory is that it fundamentally explains gravity. At this point, you might think we have finally reached a conclusion regarding the nature of gravity, but there are problems. There is no scientific consensus that M-theory correctly describes reality. Its detractors, such as Richard Feynman, Roger Penrose and Sheldon Lee Glashow, have criticized M-theory for not providing experimental predictions at accessible energy scales. In essence, science has been unable to verify M-theory experimentally.

While scientists understand how gravity acts, they do not understand why it exists. For example, why are atoms mostly empty space, instead of being pulled into a solid mass by gravity? Why is the force that holds atoms together different from gravity? Modern physics holds that the gravitational force is mediated by a massless particle called the graviton, which is postulated to travel at the speed of light. However, there is no experimental evidence that the graviton exists. In essence, the effects of gravity have been known for thousands of years, likely by the earliest humans. Laws describing the behavior of gravity have been known for hundreds of years. The exact nature of gravity continues to be controversial.

Is there a micro gravity in the outside space which is essentially vaccum.

So the answer to the question is that “we dont know.” So we know its effects, but we dont know what causes it.

Interesting……

That seems to be about the size of it.

Very well explained . Another step in our learning process. After learning that process we will be trying to find the next mystery of our physical world . Will this go on and on , are we will have complete knowledge of everything .

Answer me this, is the curvature of spacetime caused by gravity or is it what causes gravity as well. Take two objects of the same size but different masses. if the object with a greater mass has a greater density it in turn is displacing more space on the quantum level than that of the object with a lesser density. Therefore, wouldn’t it be correct to assume that the denser object has a greater gravity?

According to Einstein’s general theory of relativity, space is deformed (i.e., warped or curved) by matter. The greater the density of matter, the greater the deformation. Thus, denser objects have a greater gravitational effect.

My understanding is the more mass an object has, the more it warps space and therefore the more gravity it causes. If you take an object and compress it, it’s density increases, but it doesn’t cause any more gravity because it’s mass doesn’t increase. Am I wrong?

You are correct.

What happens at the atomic scale is the key to understanding the mechanism to what causes gravity in the the oceans structure of fluid water molecules. The nuclei of the hydrogen and oxygen atoms that form the water molecules are attracted the central gravitational point of the earth so that with-in the electron spheres each nuclei leans from its central neutral gravitational position toward the center of the earth. As the moon transits above; the nuclei of each atom is slightly attracted toward the moons central gravitational point. This attraction to the moon within the electron sphere is tiny with-in each water molecule. The combined atomic gravitational fluctuation effect with-in the large deep fluid atomic ocean structure is observed as the motion of the daily tides.

– See more at: http://www.windsorrealestateinfo.com/Gravity-at-the-Atomic-Scale-by-Tim-G.-Meloche#sthash.Rh9Fy86O.dpuf

were is the answer buch

I do have an explanation of how matter curves spacetime. Furthermore the mechanism I have could be used to explain the origin of other forces including new forces that are responsible for unexplainable phenomena such as the galactic rotation problem and the accelerated expansion of the universe which are currently attributable to dark matter and dark energy, respectively. The mechanism I have is an underlying mechanism that keeps on generating various forces at various stages in the universe just like evolution is the underlying mechanism that generates various life forms at progressive times.

You may well have a new explanation for unexplained phenomena. I suggest you either write a book or submit a paper to a reputable journal for peer review. The latter is what Einstein did regarding his special and general theories of relativity.

I am just wondering how much time will it take my previous comment to be moderated. I have done the comment on 28 January and has not been moderated till now?!!!

I apologize. I work hard at getting to all comments. Sorry I missed yours.

If you want to know what causes gravity just look at the equation for escape velocity Ve^2 = 2GM/r. That Ve^2 looks a lot like a field diluted C^2 and the C^2 looks a lot like the rest energy per unit mass of M. So why not spread the rest mass energy out as a field and call it gravity.

For several years now I am intrigued by the origin of gravity. I never agreed with the idea that the gravity could be a kind force analogue to magnetism. Why? Because magnetism is both attractive and repulsive, while gravitation is only “attractive”. It seemed like no theory was able to explain this peculiarity. However, in 2011, I heard about something new in relation to this enigma but, oddly enough, nobody seems took it into account. That year, three American scientists won the Nobel prize in physics “for the discovery of the accelerating expansion of the Universe through observations of distant supernovae”. That was a big piece of news, at least to me. I wonder why no one linked this astounding finding with the gravity! To me, the connection between both phenomena is clear.

As a matter of fact, I am convinced now that in this “accelerating expansion” lies the ultimate CAUSE OF GRAVITATION.

Today, 2018 seven years later from that 2011, still I couldn’t find on the internet any hypothesis linking both phenomena so I want to expose my point in the hope of bringing a different perspective on the subject.

Einstein asserted that we can’t tell the difference between a body resting within a gravitational field and a body undergoing acceleration —equivalence principle—. In other words, if we are inside a rocket with no windows, we can’t tell if we are under the influence of a gravitational field of —to say— a planet or, simply, the rocket is undergoing some kind of acceleration.

My conjecture is: Gravity is just an indirect consequence of that accelerated (fourth-dimensional) cosmic expansion. And of the inertia of massive bodies. This inertia would be the cause of the space-time local curvature that Einstein was talking about. Can seem an idea too simple to be true, but is an idea that I find logical. Why? Let us think about this for a second. Each time we undergo acceleration, we undergo “gravity”. If we are in a car, if the car is accelerating, we feel a “gravity” towards the seat back. If we push the brake pedal, our body feels “gravity” towards the front. In fact, we can’t avoid that “gravity” each time we are accelerated in any direction. Then, how come the universe could manage to “hide” his gravity if is undergoing such acceleration? The answer is simple, the universe does not hide anything, the universal gravitation would be, precisely, the natural consequence of that cosmic acceleration!

Let me draw an analogy between our expanding universe and a balloon. Let’s suppose we have a balloon expanding more and more. In fact, suppose that such expansion is faster at every turn. Suppose too, that on the surface of this balloon there are flat objects, with different masses each one. Because of their inertia, each object will pressure the surface of the balloon, more deeply in the case of massive bodies and more shallowly in the case of lighter bodies. If we assume that the surface of that balloon is slippery, then, lighter objects will fall inside the depressions caused by the heavier ones. Why will the lighter bodies fall into it?

Let’s suppose a game on a billiard table. The end of the game would be to carry a ball from one end of the cloth to the other. But the rules are that instead of hitting the ball with the cue in the traditional way, we use the same cue, placed horizontally on the cloth to do it. Then, we place the cue at one end of the table, the ball in the middle and start to move the cue with some acceleration to the other end of the table. What happens to the ball?

Naturally, it will move forward pushed by the cue. But we’ll notice that as it moves forward, it moves to one side as well. Why? Because, as we all know, pool cues are thicker at one end than the other. This way, the ball also slides towards the tip of the cue as it moves forward. Physicists analyze this situation by decomposing the thrust force into two perpendicular vectors, one facing forward and the other to the side. That is, the ball moves to the side because a small part of the force used to push the cue forward takes a direction perpendicular to the movement. This is because the cue does not offer a perfectly horizontal front to the ball. In fact, physicists, using the sine and cosine functions, are able to calculate exactly what percentage of the force is distributed “forward” and what percentage “to the side”, depending on the angle of the cue.

What does all this have to do with the example of the balloon, you ask? Well, all in all, it’s the same situation. The balloon inflates faster and faster and as the massive objects sink its surface, the wall of the balloon does not OFFER A HORIZONTAL FRONT TO THE LIGHTER bodies in the vicinity of the massive ones. In the same way that the billiard cue did not offer a perfectly horizontal front to the ball. Therefore there is a lateral component that pushes the lighter bodies towards the depression caused by the heavier ones. The same thing happened with the pool’s cue, it was the lateral component what made the ball move towards the tip of the cue. This is what would happen in that balloon- world.

In this “world”, objects (or creatures) on the surface, are two-dimensional and can’t perceive the three-dimensional depression of the balloon. Then, each time these 2D beings on the surface see those lighter bodies go towards the heavier ones, they believe that heavier bodies attract them. In reality, lighter bodies slide over the curved “wall” of space-time. The real cause would be the curved surface of the space-time. This curved “wall” exert a force because there is a lateral component of the mysterious force behind cosmic expansion.

Maybe, a golf ball, with its dimples, that it would “inflate” could be a more apt image to understand how the universe expands. Within each “dimple” of the space-time, there is a huge number of massive bodies. For instance, our Milky Way and galaxy Andromeda, would be inside a dimple of our expanding universe. Because of that, they are in course of collision. This fact could lead us to think —mistakenly— that our universe is shrinking. But, the case is that bodies move closer only within each dimple. But dimples itself move away each with respect to others each time with increased speed.

I think you all can understand what is the point I try to make. Our universe would be undergoing an accelerated (fourth-dimensional) expansion that we can’t perceive. But we can notice their 3D consequences. First of all, we do see how the space between distant galaxies are growing more and more. That is consistent with the balloon model. Furthermore, relatively “close” galaxies -like Andromeda and our Milky Way- are getting closer and closer each time. This is consistent with the expanding golf ball model too.

In other words, gravity is not an intrinsic characteristic of the mass. Is just the result of a combination of an accelerated expanding (fourth-dimensional) universe, and multiple massive objects. Those massive objects curve the space-time locally because of their inertia. And lighter bodies fall into holes. But, why? Not because of a kind of attractive property of massive bodies. The real cause is the curved surface of the space-time, this curved “wall” exert a force because of its lateral component.

Yes, the gravity would be the result of a “push” rather than a “pull”.

This form to understand gravity has the advantage of explaining the reason behind the equality between gravitational and inertial masses.

I want to remember the two kinds of masses the physicists postulate. This piece of information come from Wikipedia:

There are several distinct phenomena which can be used to measure mass. Although some theorists have speculated that some of these phenomena could be independent of each other, current experiments have found no difference in results regardless of how it is measured:

Inertial mass measures an object’s resistance to being accelerated by a force (represented by the relationship F = ma).

Active gravitational mass measures the gravitational force exerted by an object.

Passive gravitational mass measures the gravitational force exerted on an object in a known gravitational field.

“The interesting thing is that, physically, no difference has been found between gravitational and inertial mass. Einstein used the fact that gravitational and inertial mass were equal to begin his Theory of General Relativity in which he postulated that gravitational mass was the same as inertial mass and that the acceleration of gravity is a result of a ‘valley’ or slope in the space-time continuum”

As we see, they say that “Einstein postulated that gravitational mass was the same as inertial mass and that the acceleration of gravity is a result of a ‘valley’ or slope in the space-time continuum”.

OK, but Einstein doesn’t explain HOW that “valley” bring about gravity, neither why both masses are indistinguishable.

And the answer could be: are the same because the GRAVITATIONAL mass of a body depends on a force, the lateral component that comes from the curvature of the “wall” of the space-time. But such force, in turn, depends on the inertial mass of the very body!

Again: “ Gravitational mass measures the gravitational force exerted on an object in a known gravitational field”.

But if we consider such force not as the influence of a “gravitational field” on an object, but as the reaction of the (accelerated) “wall” of space-time to the inertial resistance of that very object, the identity becomes obvious. Each object, due to its inertial mass, curves locally the space-time and, in consequence, receive a thrust force proportional to its mass.

To explain this I’d like to back to the example of the billiard. Let’s suppose, again, we push a ball with the middle of the cue in a horizontal position. The ball, as it moves forward, it moves to one side due to the minimal leaning of the cue. For case, suppose the ball takes three seconds to reach the pool’s side band. Later, we change the ball for other heavier. What’s going to happen? Well, if we push the cue with the same thrust force (and with the same inclination of the cue), the ball will take up more time to reach the pool’s side band due to its greater weight. But, if we incline more the cue, then the lateral component of the force we apply become greater, even if we do not change the thrust force we apply. And the ball can reach the side band in the three seconds again.

In our balloon-world, this would be the case of the bodies with different masses. For one hand, more mass means more inertia to move it laterally. But, at the same time, more inertia means more curvature of the wall, and hence, more lateral thrust. That’s the key. It is as if each body in our world-balloon were pushed by a cue with different inclination depending on its inertial mass.

The more mass, more reactive force, then, we have the same acceleration for all objects in free fall, as Galileo showed us in the Leaning Tower of Pisa experiment.

If all the above were true, there is no reason for searching the graviton, the hypothetical quantum of gravitational energy.

Furthermore, if our universe, for a moment, would stop his accelerated expansion, gravity would disappear too!