Astronomy is the oldest
natural science. The
Ancient Egyptians, and
Indus Valley Civilization all understood that the
objects in the sky moved since before 3000
 This is because they worshiped the objects in the sky as gods. Their understanding wasn't scientific, but their observations influenced later astronomy. A significant amount of astronomy came from
Ancient Egypt, and
Ancient Greece. Astronomers from Egypt built monuments that showed how objects in the sky moved, and most of the names for the constellations in the
Northern hemisphere came from Greek astronomers.
Natural philosophy started in Greece around 650 BC when
a movement of philosophers replaced
naturalism, which refuted the spiritual.
Leucippus and his student
Democritus suggested the idea of the
atom around this period.
Physics in the medieval Islamic world
Islamic scholars continued to study
Aristotelian physics during the
Islamic Golden Age. They also developed an early form of the
scientific method. Scientists like
Avicenna worked extensively on
The Book of Optics, Ibn al-Haytham rejected previous Greek ideas concerning vision and proposed a new theory. He studied how
light enters the
eye and then developed the
camera obscura. European scientists later built eyeglasses, magnifying glasses, telescopes, and cameras from this book.
Physics became a separate field of study after the
Galileo's experiments helped to create classical physics. Although he did not invent the telescope, he used it when he looked into the night sky. He discovered that the stars and planets were not perfect. He also investigated gravity.
Isaac Newton used Galileo's ideas to create his
three laws of motion.
 He also developed calculus to help understand problems in mechanics, such as
how celestial bodies moved around the Sun.
In a couple centuries, the
Industrial Revolution was in full swing and many more discoveries were made in many fields of science. The laws of classical physics are good enough to study objects that move much slower than the
speed of light, and are not microscopic. When scientists first studied
quantum mechanics, they had to create a new set of laws, which was the start of Modern Physics.
As scientists researched particles, they discovered what classical mechanics could not explain. Classical mechanics predicted that the
speed of light varied, but experiments showed the speed of light stayed the same. This was predicted by
Albert Einstein's theory of
special relativity. Einstein predicted that the speed of
electromagnetic radiation through empty space would always be the same. His view of
space-time replaced the ancient idea that space and time were quite separate things.
Max Planck came up with
quantum mechanics to explain why
metal releases electrons when you shine a light at it, and why
matter emits radiation. Quantum mechanics applies for very small things like the electrons, protons, and neutrons that make up an
atom. People like
Erwin Schrödinger, and
Paul Dirac continued to work on quantum mechanics and eventually we got the