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apurvmj
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It is said that light particle being mass-less charged particle are not affected by gravity but space, which is mass-less and charge-less get warped by gravity. How come?
There is a big distinction. Gravity is the curvature of spacetime. Spacetime exists even in Special Relativity, where there is no gravity.ChrisVer said:Well, there is not a distinction between gravity and spacetime.
Geometrodynamics is not the same thing as General Relativity. Geometrodynamics was Wheeler's attempt to replace all of elementary particle physics with curved spacetime.That's why some people refer to General Relativity as geometrodynamics (as stated in wiki, it's a loose use).
Photons possesses energy and momentum and are affected by gravity, just as particles with mass are affected by gravity.The concept is that the photon (light's particle) is not really affected by gravity- it's massless.
Bill_K said:There is a big distinction. Gravity is the curvature of spacetime. Spacetime exists even in Special Relativity, where there is no gravity.
Geometrodynamics is not the same thing as General Relativity. Geometrodynamics was Wheeler's attempt to replace all of elementary particle physics with curved spacetime.
Photons possesses energy and momentum and are affected by gravity, just as particles with mass are affected by gravity.
apurvmj said:It is said that light particle being mass-less charged particle are not affected by gravity [...]
The idea that photons and other particles follow geodesics is a weak field approximation, neglecting the gravitational field produced by the particle itself.ChrisVer said:Photons however follow geodesics (no matter what energy they have)... that means they follow straight lines on the specific geometry, as they do as "massless" on a flat spacetime.
Bill_K said:The idea that photons and other particles follow geodesics is a weak field approximation, neglecting the gravitational field produced by the particle itself.
Consider a photon passing by a central body. Both objects possesses energy, and together they orbit about their common center of energy. The gravitational field carried by the photon affects the central body, moving it back and forth. And the path followed by the photon is determined by the combined fields of both objects, and is not the same as a geodesic in the original spacetime.
ChrisVer said:The concept is that the photon (light's particle) is not really affected by gravity- it's massless.
apurvmj said:It is dificult me to understand mass can affect absolute nothing ie space, but can't affect energy particle like photon.
apurvmj said:Sapce time curvature is gravity right. But without mass curvature in space doesn't exist. It is dificult me to understand mass can affect absolute nothing ie space, but can't affect energy particle like photon.
Mordred said:the volume of space is never empty, there is always some form of energy/mass-density residing in every region of space.
Mordred said:How space time geometry is described is essentially a distribution of the energy-density relations.
Mordred said:Localized gravity essentially affects the pressure distributions in a given region.
PeterDonis said:This is (to the best of our knowledge) true of our universe, but it is important to note, first, that for much of the universe's volume, while the energy density is not, strictly speaking, zero, it is very, very, very, very small, much too small for us to measure directly, and there are other places, such as the interiors of neutron stars, where the energy density is very, very, very large, thirteen or more orders of magnitude larger than the density of water (for a total variation in energy density of something like 40 orders of magnitude or more). The FLRW model, with a constant energy density everywhere at a given instant of time, is an approximation, only meant to be valid on a very large distance scale, something like a billion light years or larger.
Gravity is a fundamental force of nature that causes objects with mass to attract each other. It is responsible for the motion of planets, stars, and galaxies.
Gravity affects space by warping it. The presence of massive objects, such as planets or stars, causes space to bend and curve. This is what we commonly refer to as the force of gravity.
The relationship between gravity and space is crucial in understanding the behavior of objects in the universe. Without gravity, the planets would not orbit the sun, and stars would not form. It also plays a role in the structure of the universe and its expansion.
The theory of general relativity, developed by Albert Einstein, explains the relationship between gravity and space. It states that gravity is not a force but rather a result of the curvature of space caused by massive objects.
According to the theory of relativity, gravity also affects time. The stronger the gravitational pull, the slower time moves. This phenomenon, known as time dilation, has been proven through experiments and is essential in understanding the behavior of objects in space.