History
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Ancient astronomy
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See the main article: History of astronomy
Astronomy is the oldest natural science. The Sumerians, and Ancient Egyptians studied
the stars, mostly with a view to prediction and religion. The first Babylonian star maps
date from about 1200 BC. That astronomical events are periodic also dates back to the
Babylonians.[3] Their understanding was not scientific, but their observations influenced
later astronomy. Much astronomy came from Mesopotamia, Babylonia, 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
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Natural philosophy started in Greece around 650 BC when a movement of
philosophers replaced superstition with 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
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Islamic scholars continued to study Aristotelian physics during the Islamic Golden Age.
One main contribution was to observational astronomy. Some, like Ibn Sahl, Al-
Kindi, Ibn al-Haytham, Al-Farisi and Avicenna, worked on optics and vision. In 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 developed the camera
obscura. European scientists later built eyeglasses, magnifying glasses, telescopes,
and cameras from this book.
Classical physics
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Physics became a separate field of study after the scientific revolution.
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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 supported Copernicus'
idea that the Earth moved around the Sun (heliocentrism). He also investigated
gravity. Isaac Newton used Galileo's ideas to create his three laws of motion and
his law of universal gravitation. Together these laws explained the motion of falling
bodies near the earth and the motion of earth and planets around the sun. [5]
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.
Modern physics
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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 Werner Heisenberg, Erwin Schrödinger, and Paul Dirac continued
to work on quantum mechanics and eventually we got the Standard Model.[6][7]
Definition
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Physics is the study of energy and matter in space and time and how they are related to
each other. Physicists assume the existence of mass, length, time and electric
current and then define (give the meaning of) all other physical quantities in terms of
these basic units. Mass, length, time, and electric current are never defined but
the standard units used to measure them are always defined. In the International
System of Units (abbreviated SI from the French Système International), the kilogram is
the basic unit of mass, the metre is the basic unit of length, the second is the basic unit
of time, and the ampere is the basic unit of electric current. In addition to these four
units, there are three other ones: the mole, which is the unit of the quantity of matter,
the candela which measures the luminous intensity (the power of lighting) and
the kelvin, the unit of temperature.
Physics studies how things move, and the forces that make them move. For
example, velocity and acceleration are used by physics to show how things move.
Also, physicists study the forces of gravity, electricity, magnetism and the forces that
hold things together.
Physics studies very large things, and very small things. For instance, physicists can
study stars, planets and galaxies but could also study small pieces of matter, such
as atoms and electrons.They may also study sound, light and other waves. As well as
that, they could examine energy, heat and radioactivity, and even space and time.
Physics not only helps people understand how objects move, but how they change
form, how they make noise, how hot or cold they will be, and what they are made of at
the smallest level. In short, physics is the branch of science that deals with properties of
matter and energy along with the interaction between them.
