Hi Friends,

I posted a question here about the properties of light several months ago and got some really helpful answers. I now have a question about gravity and would love to here what you all have to say!

So, I have been trying to understand gravity in general relativity and here is where I am getting confused. If I understand correctly, relativity says gravity is just the curvature of spacetime, induced by the presence of mass. Masses are just following straight lines in space, but their 'straight' lines are warped by the curved spacetime. When a moving mass reaches a curved region, it's 'straight' line is following the curve, leading it to orbit the larger mass or appear to be attracted to it. I totally understand that, but where I am lost is how two stationary masses would attract eachother. How does this warped spacetime view of gravity explain the acceleration of stationary masses directly towards a larger mass? How could the stationary mass go from not moving, so it has no 'straight' line, to being accelerated across a new 'straight' line right towards the larger mass?

I have been reading books and watching videos but just cannot find a good explanation for the acceleration of stationary objects. I see all these visualizations of spacetime as a sheet and mass makes a dent in it, making other masses 'fall in', but that explanation requires the old attractive force gravity to make the mass 'fall down the hill'... If masses are just following straight lines, then why should they be 'attracted' to sources of curvature in space?

Thank you

I posted a question here about the properties of light several months ago and got some really helpful answers. I now have a question about gravity and would love to here what you all have to say!

So, I have been trying to understand gravity in general relativity and here is where I am getting confused. If I understand correctly, relativity says gravity is just the curvature of spacetime, induced by the presence of mass. Masses are just following straight lines in space, but their 'straight' lines are warped by the curved spacetime. When a moving mass reaches a curved region, it's 'straight' line is following the curve, leading it to orbit the larger mass or appear to be attracted to it. I totally understand that, but where I am lost is how two stationary masses would attract eachother. How does this warped spacetime view of gravity explain the acceleration of stationary masses directly towards a larger mass? How could the stationary mass go from not moving, so it has no 'straight' line, to being accelerated across a new 'straight' line right towards the larger mass?

I have been reading books and watching videos but just cannot find a good explanation for the acceleration of stationary objects. I see all these visualizations of spacetime as a sheet and mass makes a dent in it, making other masses 'fall in', but that explanation requires the old attractive force gravity to make the mass 'fall down the hill'... If masses are just following straight lines, then why should they be 'attracted' to sources of curvature in space?

Thank you