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This "transforming away" is similar to the difference between Cartesian and polar coordinates on a flat sheet of paper. The Cartesian coordinate system is flat, and the polar system is curved. But they are both coordinate systems on a flat sheet of paper. However, there are surfaces ("curved surfaces"), like a sphere, that have no flat coordinate system at all. In spacetime, this is equivalent to something that has no flat coordinate systems, and hence gives rise to fictitious forces that can't be transformed away. This is what gives rise to gravity, a fictitious force that, unlike the centrifugal or Coriolis force, can't be transformed away. That is, there is no place where one can stand and see gravity as just a case of people being pushed on by a floor that is accelerating upward.
This "transforming away" is similar to the difference between Cartesian and polar coordinates on a flat sheet of paper. The Cartesian coordinate system is flat, and the polar system is curved. But they are both coordinate systems on a flat sheet of paper. However, there are surfaces ("curved surfaces"), like a sphere, that have no flat coordinate system at all. In spacetime, this is equivalent to something that has no flat coordinate systems, and hence gives rise to fictitious forces that can't be transformed away. This is what gives rise to gravity, a fictitious force that, unlike the centrifugal or Coriolis force, can't be transformed away. That is, there is no place where one can stand and see gravity as just a case of people being pushed on by a floor that is accelerating upward.
This is the curvature of spacetime. The Einstein Field Equations explain how that curvature arises fomr the presence of massive objects like the Earth or the Sun.
This is the curvature of spacetime. The Einstein Field Equations explain how that curvature arises from the presence of massive objects like the Earth or the Sun.
[[Category: Astronomy]]
[[Category: Astronomy]]
[[Category: Cosmology]]
[[Category: Cosmology]]
[[Category: Physics]]
[[Category: Physics]]