What exactly is gravity?

Question

what kind of force is it? Why does it happen when there is matter.

Answer 1

Gravity is electromangetic in nature. Check the link below.

Someone wrote to me saying that electromagnetic waves did not have mass, therefore, they could not account for gravity.

First of all, electromagnetic waves are energy, and there is something called electromagnetic equivalent of mass.

A "resonant cavity" is a confined electromagnetic wave. No energy escapes it, yet, it has mass, and therefore it is subject to gravity. If so, then ALL mass is electromagnetic in nature. Which makes you conclude that gravity is an electromagnetic phenomenon. See link below for a more rigurous analysis.

Answer 2

Gravity is an unusual force! It appears to be very different from the other forces we know about (electrostatic, strong, weak) because it is a description of how spacetime is curved. More precisely, the existence of energy curves spacetime. What we call "gravity" is the observed effect of particles moving through curved spacetime.

Matter is equivalent to energy (Einstein's famous E=mc^2 equation), so matter will bend spacetime, but just energy is enough! Just as E=mc^2 says that matter is energy, Einstein's field equations G = 8 pi T say that energy is actually spacetime curvature. Get enough energy (or mass) in a small area, and its curvature will have measurable impact on nearby spacetime.

At small scales (like planets and asteroids, or far from a star) gravity behaves like a long-range force similar to electrostatics, and appears to only interact with massive objects. But when spacetime really gets bent (near a star, or counting the impact of an entire galaxy of stars), the effect on spacetime is more obvious. Light rays get bent near the curvature source, even though they have no mass. Time slows down relative to distant observers.

What kind of force is it? It is actually not a force, but a description of how curved spacetime behaves. Why does it happen when there is matter? Because matter (and energy) are sources of spacetime curvature.

Answer 3

For all our theories and advanced technology, we really don't know. Even if you describe it as a warping of spacetime in the presence of mass, we don't know why that happens. We don't know why it's so much weaker than all the other forces we know about. It's a property of our universe. If there is such a thing as other universes, we have no idea whether they have the same properties, physical laws, or component particles. You could say it's a choice God made when creating the universe, or you could try to come up with some other explanation.

Answer 4

Gravity is the apparent effect of the curvature of spacetime by masses. If an object follows a least-distance (geodesic) path in spacetime, it experiences NO forces. In the case of a planet such a earth, the spacetime curvature is such that one such geodesic is an elliptical orbit around the center of mass of the planet. Such an object experiences no force. Another geodesic is the path of an object falling toward the center of mass of the planet. To us in three dimensional space, that path looks like a straight line, but in spacetime it is curved because of its acceleration (draw a graph of an accelerating object, one axis space (just one dimension), the other time: that path is curved). When we try to prevent the object from following that path (by stopping it) that requires a force, and we call that force gravity.

Answer 5

... as far as I could recall what my physics teacher says ...., that GRAVITY is a force that pulls the matter towards the center.. So if the gravity is not present well what may happen is that matter or object tend to float in the air no order at all or should we say,..THERE WILL BE NO ORDER

Answer 6

Gravity is a bit of a mystery. Many believe that the presence of mass warps the surface of spacetime and causes paths of objects/light to curve towards a great mass.

Answer 7

Gravitation is a natural phenomenon by which all objects attract each other. In everyday life, gravitation is most familiar as the agency that endows objects with weight. Gravitation is responsible for keeping the Earth and the other planets in their orbits around the Sun; for keeping the Moon in its orbit around the Earth; for the formation of tides; for convection (by which hot fluids rise); for heating the interiors of forming stars and planets to very high temperatures; and for various other phenomena that we observe. Gravitation is also the reason for the very existence of the Earth, the Sun, and most macroscopic objects in the universe; without it, matter would not have coalesced into these large masses, and life, as we know it, would not exist.

Modern physics describes gravitation using the general theory of relativity, but the much simpler Newton's law of universal gravitation provides an excellent approximation in most cases.

In scientific terminology gravitation and gravity are distinct. "Gravitation" is the attractive influence that all objects exert on each other, while "gravity" specifically refers to a force which all massive objects (objects with mass) are theorized to exert on each other to cause gravitation. Although these terms are interchangeable in everyday use, in theories other than Newton's, gravitation is caused by factors other than gravity. For example in general relativity, gravitation is due to spacetime curvatures which causes inertially moving objects to tend to accelerate towards each other. Another (discredited) example is Le Sage's theory of gravitation, in which massive objects are effectively pushed towards each other.
In general relativity, the effects of gravitation are ascribed to spacetime curvature instead of to a force. The starting point for general relativity is the equivalence principle, which equates free fall with inertial motion. The issue that this creates is that free-falling objects can accelerate with respect to each other. In Newtonian physics, no such acceleration can occur unless at least one of the objects is being operated on by a force (and therefore is not moving inertially).

To deal with this difficulty, Einstein proposed that spacetime is curved by matter, and that free-falling objects are moving along locally straight paths in curved spacetime. (This type of path is called a geodesic). More specifically, Einstein discovered the field equations of general relativity, which relate the presence of matter and the curvature of spacetime and are named after him. The Einstein field equations are a set of 10 simultaneous, non-linear, differential equations. The solutions of the field equations are the components of the metric tensor of spacetime. A metric tensor describes a geometry of spacetime. The geodesic paths for a spacetime are calculated from the metric tensor.

Answer 8

# The natural force of attraction exerted by a celestial body, such as Earth, upon objects at or near its surface, tending to draw them toward the center of the body.
# The natural force of attraction between any two massive bodies, which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

Answer 9

Very good explanation gp4rts !

But the very fundamental question that reamins is that Why does mass curve the fabric od space-time ? I cant think of a good explanation, though it can be deductively reasoned that without curving space time mass will cease to exist!