The question might seem silly (and, maybe it is ), but I would like to know if gravity is really something you can not explain in some other terms and have just to take for granted (i.e. it simply works as it works and we, currently, do not know why), kind of like magnetic force?
Or is there an explanation?
Here are some, exact, points that seem puzzling to me:
If we would build a spaceship resembling Earth in shape and size, would it have gravity, just because of mentioned properties (although, as I understand it, the Earth is round, because of gravity)?
If we would take the Earth and cut off (kind of like from an apple) 1/10 of it the greater part would still have gravity, while the lesser won't?
- What about if we would split Earth in half?
- Or 40% : 60%?
Are we currently (or, theoretically, will ever be) capable of creating artificial objects, that have a gravity of their own?
Answer
Physics models exist in many frameworks, a number of them emerge from an underlying framework, which is considered fundamental.
What you are asking about comes from the classical gravitational model, which is based on a gravity law and the laws of Newtonian mechanics.
Laws in physics are like axioms in mathematics, necessary to pickup the correct mathematical model that will describe data, and predict new situations.
All of your questions are answerable within classical gravitational theory.
answers for
All masses interact gravitationally according to the law, $(G.m_1M_2)/{r^2}$. Shapes and densities and in general mathematical analysis allows the calculation of the force.
The various cuts will follow the law
ALL masses have a gravitational field
These answers are within the classical framework
Classical gravitation emerges from an underlying General Relativity mathematical model, but that is another story.
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