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We know that the curvature of spacetime is gravity itself and it is not a force.so,why do we feel our weight in a curve spacetime but not in a straight(I mean not curve) space time like zero gravity space?Why something called "Curvature" produce weight we feel?

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  • $\begingroup$ Actually, your feeling of weight is not directly related to the curvature of space time - for example, the people on the ISS who feel weightless are in a curvature not much different than the one you're in right now, but due to them free falling the net force on them is 0. $\endgroup$ – Mr.WorshipMe May 9 '16 at 19:20
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When you sit in your F1 car and turn right with 1g of lateral acceleration, you feel a centrifugal force (acceleration) of 1g pulling you in the opposite direction (left, in the car's frame). That is, there is a fictitious force caused by your curving reference frame. This is a Galilean point of view--an accelerated reference frame causes fictitious forces.

Now you are standing still on the Earth, yet you fell 1g pulling you down--but you're not moving--according to Galileo-so what's up? According to Einstein, you are moving--in Spacetime--yes, you are moving forward in time with speed ||c||--and thanks to the Earth's mass, the straight path forward actually curves downward at 1g. [You can prove this by stepping off the ledge of a tall building--but thought experiments are safer].

The surface on which you stand applies a force (per unit mass) of 1g upward that continuously pushes you off this spacetime-straight line--you feel this as gravity pulling you in the opposite direction: down.

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  • $\begingroup$ So,we feel weight due to reaction force of earth surface(e.g. for Newton third law)? $\endgroup$ – Abu sayed Jul 10 '16 at 6:46

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