Human knowledge about reality is a very long list of observations.
Some of those observations are poorly made, but the ones that are reliable we call facts.
But there are too many facts for anyone to know them all. Just think back to your last history class and imagine if you needed to know all the facts to pass the test, like what General So-and-So's breakfast was three days before the famous battle, how many soldiers where shot in the face, and if the surrendering general was wearing a clean uniform or one soiled from battle.
So science advances when someone finds something just as good as memorizing a bunch of facts. We call the ability to communicate precise and useful descriptions of facts based on their circumstances a scientific theory. Because it has to be precise, it is usually expressed in terms of math and because it has to be useful, it has to match up well with the most facts and be the simplest such theory to do so.

Before Galileo, the writings of Aristotle controlled much of Europe's mindset with regard to gravity and the motion of bodies. Aristotle believed the stars and planets had one type of motion, while things that could be touched on Earth had a nature which was completely different. While Aristotle believed in gravity (i.e. he wasn't insane when considering the motion of thrown objects), he believed that they travelled in a straight line, eventually ran out of forward motion, and fell to Earth. Aristotle's idea of gravity is similar to that experienced by cartoon characters (especially the coyote of the Roadrunner cartoons) who run off of a cliff and and don't fall until they come to a stop (and for cartoon characters, a moment of realization).

Galileo experimented and came to the conclusion that Aristotle was wrong on two points. Firstly, objects don't just run out of forward movement -- it is stolen from them by rubbing against other things. With smoother balls and tracks, Galileo demonstrated that rest was not a special state, but just the state of motion shared by a lot of things in common. Secondly, falling objects fall at the same rate regardless of their composition or state of motion. Thus Galileo developed ideas about acceleration.

Newton, advanced science many ways.
He invented a new type of math to deal with velocity and acceleration even when they happen in different directions and change over time. With this new math, calculus, it was possible to make more precise statements with less effort than other methods.
He developed the concept of momentum and mass.
He overthrew Aristotle's ill-gotten authority by unifying the motions of the planets with the motion of bodies on Earth. His Universal Gravitation showed that to high precision the motion of the planets and falling rocks was governed by the same laws of momentum, mass and gravity.
He experimented on his own eyeball, and developed useful descriptions of light and color.

Thus he advanced human knowledge from where it was before. But he was a bit prejudiced by his experiences and could not imagine the advances that would be made.

In 1905, Einstein wrote four remarkable papers.
In one, he showed that there existed strong evidence that the molecular nature of matter had visible consequence, which was a demonstration that the hypothetical "atoms" of chemistry were physically real.
In the second, he demonstrated, as Newton believed, that light came in chunks that carried momentum. Newton clearly didn't have the whole picture, but quantum physics from 1900 to the 1930s would unify the world of light and the Newtonian world of particles into a single physics.
In the last two, Einstein abolished the Newtonian concept of Euclidean space and absolute time. The relationship between velocity and momentum would change as a result of this discovery, but only significantly so for things fast enough to go around the Earth in less than a minute.
Later, in 1916, he would finish extending these ideas about motion to replace Newton's Universal Gravitation with an even more universal General Relativity -- a theory which predicts how the shape of the universe changes over time.

Newton's ideas still reign as precise and useful for things big enough to touch and slow enough to time in a race with a stopwatch and no more gravity than the Sun. But Einstein's ideas work even better.

Conceptually, Newton's prejudices about absolute time and Euclidean space and the instantaneous speed of gravity are simply wrong. Just as Aristotle's prejudices against experimentation and placing the motion of the planets outside the reach of human science were completely off-base. Einstein himself was prejudiced in a way that left him unhappy about the great changes in physics, and he died before the discovery of quarks which started yet more great changes in physics.

Prejudices may allow us to leap forward, in pursuit of a trail of thought that doesn't start off with strong evidentiary support, but gains more as the trail is followed. Or they may hold us back. But ultimately the test of scientific theories is how close they come to replacing the need to memorize long lists of facts.

Much of what we call science today owes to Newton and his insistence on communicating precise and useful descriptions of reality. But Newton was not the end of progress in science because we have grabbed observations which Newton could never have predicted that we would.