Albert Einstein was not a physicist but a mathematician. He dreamt of deriving a unified field equation that incorporated gravity and electromagnetics as a total description of physical reality.
We are still waiting.
We will be waiting for a long time because gravity isn’t a real force but the mistake Isaac Newton made when he interpreted the common-day occurrence of things dropping down onto the earth’s surface as being due to an innate attraction of matter with matter and not being aware of electromagnetism.
The problem with a unified field equation is that you need to observe and measure two components at the same time and combine them in one equation. Except that if the electromagnetic force is assigned the integer portion of ‘the’ number, then the gravitational component at the same scale will be the decimal point after the integer followed by 38 zeros, with the final number being the gravity component.
Fluctuations in the decimal fraction will not be noticed by an apparatus designed to cope with variations of the integer part of the number.
This is why Einstein never succeeded because he wasn’t a physicist. He had a terminal infestation of mathematitus.
And if Newton observed a rubber bladder filled with helium waft its way upwards to the sky, he might have paused and realised that not all matter attracts matter.
Newton also assumed space was empty, as did his predecessors. So did we until the discovery of the solar wind and like the religiously devout, we haven’t changed our minds when new data appear but went along with confecting ad hoc adjustments to the gravity theory to cope with observation by inventing black holes, dark matter, and other fantasies in mathematical la-la land.
Gravity is essentially the force exerted on protons by the immersive electric field.
The calculus and maths are not affected by this explanation because those equations described the motion but do not explain it. The difference in mass is simply the ratio of the protons present in a shape or body compared to another body.
All matter is comprised of protons, electrons and neutrons which are joined electrons and protons. Shapes have different masses because of differing combinations of protons that make up matter. After all a 1m diameter sphere of lead simply has more protons than a 1m diameter sphere of aluminium. Dropped from a tall building both will fall to the Earth at the same speed because individual protons will not move differently than each other in the same electric field.
And if the electric field is weak or absent then gravity is weak and absent.