Newton contributed to astronomy by:

using mathematical reasoning
developing theories of gravity and motion
conducting systematic, structured experiments
all of the above

Newton contributed to astronomy by developing theories of gravity and motion.

Explanation:

Newton reflected on the fact that bodies weighed on Earth and that the stars revolved around other stars. He imagined that there was a universal force that caused bodies to attract each other. Newton called it "Universal Gravitation Force" or "Gravity."

Then, the force of gravity is the physical force exerted by the mass of a planet on the objects that are within its gravitational field. In other words, this law establishes that bodies, by simply having mass, experience a force of attraction to other bodies with mass.

Objects are attracted according to their mass and the distance between their centers: if the distance increases, the force decreases, and if the mass increases, the Universal Gravitation Force is more intense:

where G is the universal gravitation constant, whose value is

This expression indicates that the gravitational force that a point mass M exerts on another point mass m that is at a distance r from the previous one is directly proportional to the product of the masses and inversely proportional to the square of the distances that separates them.

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !