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Originally Posted by skwinty
The force of gravity does not exist. This force was a newtonian construct to explain why apples fall from trees to the ground and why we don't fall of the earth.
The earth is in freefall around the sun (due to the curvature of space time caused by the suns mass) and bodies in free fall feel no "gravity". As far as the earth is concerned it is travelling in a straight line in curved space time.
ie the shortest distance between 2 points which is a straight line.
We dont fall off the earth due to the inertia and acceleration of the earth.
Originally Posted by renormalised
Pretty good answer, Steve, but not quite correct. For every day situations, such as an apple falling from a tree, tripping over a crack in the pavement etc, gravity can still be called a force (although, technically, it still isn't....if you like to be pedantic about it).
Help me out here renorm.
What part of my statement is incorrect?
My understanding is that Einsteins principle of equivalence states that gravity is equivalent to acceleration.
This implies that we do not realise or feel the earths acceleration as it wends its way around the sun and hence had to invent a fictitious force of gravity to explain the fact of apples falling from trees and rivers flowing downhill.
We choose to ignore the truth that our surrounds are moving relative to us.
Once set in motion, as in a car at a constant speed, our bodies inertia tends to keep us travelling in a straight line at a constant speed until the car turns. If we are not restrained in the car we are jammed against the car door. We attribute this to the force of gravity when in effect it the effect of inertia, or the cars acceleration in a different direction.
Gravity is more of a geometry rather than a force, and the speed of gravity would refer to the speed of the geometries propogation. Herein is the function of the hypothetical "graviton".
Mass tells spacetime how to warp and warped spacetime tells mass how to move and this becomes recursive ad infinitum. This is the origin of gravity, in my understanding.
Now, I suppose this is pedantic semantics but I find that in my attempts at understanding these principles, clarity is impeded by incorrect terms being applied to the fundamentals.
ie is "force" rather than for example "field" the correct word to describe gravitational effects.
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