Oh, here is Tom's misconception:
You can say:
"To accelerate two blocks of metal of different masses to the same speed, requires different forces".
Yes, that is true, for
f=m.a.
You can say:
"So, how gravity applies same acceleration for different masses and obtain same speed?"
What you missing Tom, is a complete different way force is applied, and this is why I wrote before "the concept is the same, not the force".
When you PUSH a solid block of metal, you are applying force to a specific point of such block, this point of contact could be small if using a screwdriver, or large if using a cement brick as contact. In both cases, you are NOT applying uniform force to all atoms, just the ones on surface of contact, they are transferring movement to the other atoms. So, the force "F" necessary to accelerate the block is the SUM of force needed to move all the atoms. Gravity works differently, each atom slides down the space/time deformation, you can call it also force, but all atoms are pushed at once, individually, no matter how many atoms are there, the force applied by gravity is not applied to a surface, but to the guts of the mass, individual atoms. The final speed achieved is calculated based on individual atoms being pulled at the same time, no matter if 1 or 2 trillion atoms.
If you think as gravity as a force, it confuses you, because you are used to think and see force being applied to the surface of masses, pushing a car, a refrigerator, a furniture. That force is "compression", since it is transferred from the atoms on the surface being pushed to the next layer, next, etc. Only when the last layer (opposite surface) of atoms start to move, then your cumulative force are being applied to all atoms of the mass. Think about pushing a spring or a foam. In a way, this compression force is entirely applied to the mass, it doesn't move a second mass that is barely touching the first one side-by-side.
There is NO known force in the universe that can push all individual atoms of
any solid mass at once. Imagine you being able to push a very soft foam block without compression, without changing its surface shape even by microns. Such force doesn't exist. It needs to go inside the matter, act on individual atoms, same force applied on each one, everything at the same time, and move the whole block without compression.
Think about a mass of 10 layers of atoms. The force is applied, it acts on the first layer, but it needs to act on the second, third... tenth. How the force can continue, go through the first and reach the second, go through all the first 9 layers and still have enough energy to push the tenth layer? Go through all the trillions of layers and still being able to keep pushing next layers and so on? Such kind of force doesn't exist at all. Oh, wait, you can think of magnetic force, it can act at once in all metallic ferrous metallic atoms without deforming the surface. Ferrous, magnetic and electric forces, different story. I wrote above "
any solid mass".
The only force you can think of doing such magic trick is gravity. But gravity is not a force, if it is, you will need to explain how it can act on all layers of ANY material at the same time, acting on individual atoms, in order to not deform the surface being pushed, and "being pushed" I mean during acceleration on free fall. If you accelerate a block of foam by pushing it at 9.8m/s², your hand will deform the surface being pushed. Gravity doesn't do that.
The best way to understand gravity is comparing with buoyancy on atmosphere. Any volume of gas less denser (LD) than the gas that surrounds it will seeks escape to a LD direction, even if this density delta is barely measurable. The trick here is that the LD gas does not seek a LD direction, it is being pushed by the more denser gas all over, the side with LD pressure will allow it to move in that direction, it is not escaping, it is being pushed out. Gravity changes the density of space, matter being pressed by same space density all around, seeks to slide into such less dense space, and it works over all atoms of the mass, not a surface. So, mass moves towards less denser space, stronger the gravity, lower space density.
Now, the complication is to understand what is space, how can its density could act on individual atoms?
As a slider, doesn't matter how big the mass, its density, how many masses together or separated, they will slide down at once to the less dense space.
Now, even if you don't agree with the above, be a gentleman and give me 10 seconds and think again about your conception of f=m.a being equal to Fg=Gm1m2/r², where Fg is not a force any longer, but the inclination of a slider, while f=m.a is a non inclined slider, same space density all around.
This is a nice and easy reading about this subject:
https://www.science.org.au/curious/space-time/gravityFebruary 2016 was the first time our instrumentation could detect gravitational waves originated from space. Google and understand how they did it.
It is very difficult to build an image representing gravity space distortion, the best people can do is a two dimensional space distortion like the image below, in fact is nothing like that, it is from all angles, all directions, the distortion is all around the mass. The "sliding vector" happens everywhere around it, another mass will be sliding towards the center of the ball, no matter where it comes from.