An ocean traveler has even more vividly the impression that the ocean is made of waves than that it is made of water. - Arthur Eddington

When we compare the universe as it is now supposed to be with the universe as we had ordinarily preconceived it, the most arresting change is not the rearrangement of space and time by Einstein but the dissolution of all that we regard as most solid into tiny specks floating in void. That gives an abrupt jar to those who think that things are more or less what they seem. The revelation by modern physics of the void within the atom is more disturbing than the revelation by astronomy of the immense void of interstellar space.

"In ancient days two aviators procured to themselves wings. Daedalus flew safely through the middle air across the sea, and was duly honored on his landing. Young Icarus soared upwards towards the sun till the wax melted which bound his wings, and his flight ended in fiasco. In weighing their achievements perhaps there is something to be said for Icarus. The classic authorities tell us that he was only "doing a stunt," but I prefer to think of him as the man who certainly brought to light a constructional defect in the flying machines of his day. So too in science. Cautious Daedalus will apply his theories where he feels most confident they will safely go; but by his excess of caution their hidden weaknesses can not be brought to light. Icarus will strain his theories to the breaking-point till the weak joints gape. For a spectacular stunt? Perhaps partly; he is often very human. But if he is not yet destined to reach the sun and solve for all time the riddle of its constitution, yet he may hope to learn from his journey some hints to build a better machine"

Relativity physics is especially interested in invariants, and it has discovered and named a few more. It is a common mistake to suppose that Einstein’s theory of relativity asserts that everything is relative. Actually, it says: 'There are absolute things in the world but you must look deeply for them. The things that first present themselves to your notice are for the most part relative'.