What force holds stars together? electrostatic force magnetic force force of gravity nuclear force

Why is alchemy not considered to be a science ?

The first law of thermodynamics states that heat added to a system is neither created nor destroyed but is transformed ⇒ as it changes into other forms of energy.

Two vectors are shown. which statement best compares the vectors? vector x has greater magnitude than vector y. vector y has greater magnitude than vector x. the vectors have the same displacement. the vectors have the same direction.