> Standing on the ground, the accelerometer should show zero because gravity is cancelled out by the floor being solid. If latter can be a force, why not the fo

> Standing on the ground, the accelerometer should show zero because gravity is cancelled out by the floor being solid. If latter can be a force, why not the former? This is the part where you are demonstrably wrong. This experiment has actually been performed. Take an accelerometer that shows 0 in space far away from the Earth, where there is no gravity. Bring it back to the earth and let it fall from your ship: it will keep showing 0 (well, because of friction with air, it will show some value, but a pretty small one). When it reaches the ground, it will "suddenly" show 9.8m/s². This is not something you can debate: this is the measured reality. You can debate how to explain this, of course. But the reality is there: being in freefall towards the earth is equivalent from an accelerometer point of view to being in deep space with no engines running. Another similar observation is this: the feeling of being in a gravity well is not the earth pulling you down, it is the floor pushing you up. If you're on a space station in deep space, to feel the same as on the earth, you need something pushing at your feet in the direction of your head, not something pushing on your head in the direction of your feet.