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When people talk about how mass is curving the space-time and the geometry of it pretty much accounts for gravity, does the curvature actually means what it is usually represented as - a curve in a higher dimension (from plane to a 3D space)? In our 3D space case it would be a curve in 4th spacial dimension?
Quote from: McKayWhen people talk about how mass is curving the space-time and the geometry of it pretty much accounts for gravity, does the curvature actually means what it is usually represented as - a curve in a higher dimension (from plane to a 3D space)? In our 3D space case it would be a curve in 4th spacial dimension? No. What you’re thinking of is called extrinsic curvature. General relativity is a theory about how matter manipulates intrinsic curvature. Seehttp://mathworld.wolfram.com/ExtrinsicCurvature.htmlhttp://mathworld.wolfram.com/IntrinsicCurvature.htmlThink of a piece of paper. If we think of the paper has having zero thickness then the paper is a two dimensional object. Now roll the paper up into a cylinder. The intrinsic curvature of the sheet remains the same but the extrinsic geometry changes. The intrinsic geometry is determined by measurements made within the sheet while the extrinsic geometry is determined by how the sheet finds its way into three dimensions.The physics is explained herehttp://www.eftaylor.com/exploringblackholes/Curving140610v1.pdfBy the way, antimatter is merely matter which is composed of particles which have the opposite charge and spin of their counter parts. E.g. the antiparticle of a proton is a particle of the same charge and mass but is negatively charged and has the opposite spin. But its impossible to tell whether any substance is matter or antimatter by what it does to spacetime since the only thing that effects spacetime is matter’s energy density, momentum density and stress. None of the parameters that describe those quantities can tell you whether a substance is composed of matter or antimatter. In fact there is nothing about a particle that makes it matter rather than antimatter other than a certain convention. If that convention was changed then so too would the declaration of whether a substance was matter or antimatter.