Eli5: Why does matter have gravity and how the heck does gravity work?
In: Physics
All forms of energy, which includes mass of everyday particles but also their kinetic energy or particles like photons which have kinetic energy but no mass, distort spacetime.
What this means is that whenever they are present in some location in space and time, the lengths, angles, and time intervals around it will be distorted, in a way that is related to the locations and directions of motion of the mass and energy.
This distortion means that a particle simply trying to follow the straight-line path (which could mean staying in place, or could mean traveling in some direction at constant velocity) will find itself attracted to the gravitating object. There isn’t a force in the traditional sense – it does this because its straight-line path through spacetime actually goes towards the object, because spacetime itself is bent.
This is how gravity works according to our most current theory. As for why, we don’t know. Newton figured out that gravity attracts, and didn’t have an underlying explanation for it. Now we drilled one level down – we know the attraction is caused by spacetime warping. However, now we don’t have an underlying explanation for that. So science goes.
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