I'm going to try to explain in plain language why gravity might not exist, but let's start with a little experiment that everyone understands.
When we are in a speeding truck, the acceleration remains the same, and a small ball is hung on the roof. The ball must be floating backwards, at an angle, all the time, imagine you driving and slamming on the accelerator. Is there a feeling of pushing back? This push back feeling is a force generated by the acceleration motion of the car, if the car keeps accelerating. Then you'll always have the feeling of pushing back, and if you are suspended from the roof of the car, you will also float up like this little ball.
When we looked outside the car. We know, of course, that this is because the truck is doing an acceleration motion, and their resultant force produces the acceleration. As a result, the ball floats in the carriage, but if you have been in this carriage since birth, you have never seen the outside world. Are you confused in the carriage? Except for pull and gravity? If you take the carriage as a reference, the carriage has not been moved from beginning to end. So why did the ball float up? If you do a force analysis in the carriage, you will find that the ball is affected by the pull and gravity of the rope and is also affected by an inexplicable force, so it will float.
If there is a smart person in the carriage, he will assume that the carriage has an acceleration that is opposite to the motion of the truck, multiplied by the mass of the ball, and then the ball will be balanced, and the name of the smart man is Newton. The hypothetical force in physics is an imaginary force, and its scientific name is inertial force, and it is not a real force.
Because we, who are standing in a higher dimension, know that this force is generated because there is a forward acceleration in the carriage. But the people in the carriage don't know, and some people here may not quite understand, let's take another example. If you are free-falling from a high altitude, you are floating and you do not feel gravity. This is the state of weightlessness, and everything around you, even if you let go, will remain relatively stationary with you.
The reality is that light objects will fall slower than you, and anyone who has learned how to land two iron balls at the same time will know. Light objects fall slowly because of air resistance, not because of gravity. Let's say your fall takes place in a vacuum. Everything around you remains relatively still with you, and assuming this height is high enough, the person is in a vacuum from birth to death. Then there will be no gravity in his life, and such a situation is not very similar to the space environment, in fact, it is not just similar. Albert Einstein said that the vacuum of free fall and the space environment are exactly the same state.
Let's take it a step further, if you hang balls of different masses on the roof of your car, you will find that they all float up at the same angle. Then multiply them by their own mass, and you will see that the magnitude of the force acting on different balls is also different. This shows that the inertial force that the smart man had assumed before did not just act on the ball we started with. Rather, it acts on all objects, which shows that his imaginary inertial force is actually a force field, and from then on. Gravitation was born, and gravity is a hypothetical inertial force field of Newton, and objects of different masses are subjected to different gravitational forces.
When you look at it from a higher dimension, you will know that in fact, this force does not exist, only because we have been born until now. has always been in the carriage of the universe, just like the people in the carriage, who have never understood why the ball is floating. So let's assume an inertial force field, and Newton doesn't understand why the apple will fall to the ground, so he assumes the gravitational force. It's like when we stand outside the carriage and look at the balls in the carriage, we all know that it's not because there's a force pulling him. It's because the truck is accelerating.
This is why Einstein's special theory of relativity says that under an inertial frame of reference, the laws of physics remain the same, that is, if the frame of reference is not uniform of inertia, then Newton's three laws do not apply. This is why the three laws of Newton are called classical physics in middle school textbooks, not that they are wrong. Rather, it has limitations, and these theories are only applicable to our everyday basic physics, for cutting-edge physics and technology. Some of the basic physics knowledge we have learned about high speed and strong field is not applicable.
If gravity is an imaginary force, then our solar system and the cosmic space we can touch, or even the entire universe. are all doing accelerated motion, just like the whole universe is being carried by a truck in the carriage to do accelerated motion. I think most people know that the Earth is revolving around the Sun at a speed of 30 kilometers per second. However, what many people don't know is that the Sun carries the entire solar system around the center of the Milky Way at 230 kilometers per second.
So, every second of your life, you appear in different places in the universe, don't think that you will return to this point in the universe next year, no matter where you are sitting now, you will never go back to the cosmic space you are in now. So, cherish the moment. Then the question is, who is the Milky Way revolving? We don't know, but what is certain. The Milky Way is also moving at a speed of 500 to 600 kilometers per second relative to an extra-system reference frame, one ring after another. Humans want to run outside the carriage to see, it's a long way to go.
The first to question gravitation was Newton himself, who wrote in a letter to the Dean of Trinity College: I know that there is an example there, so I will call him gravitation. But how that force is generated, I don't know. It can only be left to future generations to study.
We usually use gravity to explain some physical problems, but we only use this result obtained by Newton to explain the phenomenon. But the root cause of this result was unknown to Newton until his death, and perhaps this is one of the reasons why Newton studied theology in his later years.
Scientific rambling