Every job has some relation to physics, but there are some examples that many would not think of as being physics-intensive. Athletes, both professional and amateur, use the principles of physics all the time. The laws of motion affect how balls are batted and thrown, and what happens when athletes tackle, run, and jump. The more an athlete and coach understand and use their knowledge of physics in their sport, the better that athlete will become.

Automobile crashes are subject to the laws of physics, and people who reconstruct crashes use physics concepts such as momentum, friction, and energy in their work. Modern electronics, from televisions and computers to smart telephones and music players, depend on the applications of physics. Telephone and computer networks are connected by fiber optics that use the principles of the refraction of light to transmit the light over thousands of miles.

Modern medical imaging methods, including X rays, CT scans, ultrasound, PET, and magnetic resonance imaging (MRI), all depend on physics. Doctors, health providers, and technicians in hospitals and medical clinics must have an understanding of these methods in order to select the best device and interpret the results.

Aristotle was a Greek philosopher and scientist who lived for sixty-two years in the fourth century B.C.E. He was a student of Plato and an accomplished scholar in the fields of biology, physics, mathematics, philosophy, astronomy, politics, religion, and education. In physics, Aristotle believed that there were five elements: earth, air, fire, water, and the fifth element, the quintessence, called aether, out of which all objects in the heavens were made. He believed that these elements moved in order to seek out each other. He stated that if all forces were removed, an object could not move. Thus motion, even with no change in speed or direction, requires a continuous force. He believed that motion was the result of the interaction between an object and the medium through which it moves.

Through the third century B.C.E. and later, experimental achievements in physics were made in such cities as Alexandria and other major cities throughout the Mediterranean. Archimedes (c. 287–c. 212 B.C.E.) measured the density of objects by measuring their displacement of water. Aristarchus of Samos is credited with measuring the ratio of the distances from Earth to the sun and to the moon, and espoused a sun-centered system. Erathosthenes determined the circumference of Earth by using shadows and trigonometry. Hipparchus discovered the precession of the equinoxes. And finally, in the first century C.E. Claudius Ptolemy proposed an order of planetary motion in which the sun, stars, and moon revolved around Earth.

After the fall of the Roman Empire, a large fraction of the books written by the early Greek scientists disappeared. In the 800s the rulers of the Islamic Caliphate collected as many of the remaining books as they could and had them translated into Arabic. Between then and about 1200 a number of scientists in the Islamic countries demonstrated the errors in Aristotelian physics. Included in this group is Alhazen, Ibm Shakir, al-Biruni, al-Khazini, and al-Baghdaadi, mainly members of the House of Wisdom in Baghdad. They foreshadowed the ideas that Copernicus, Galileo, and Newton would later develop more fully.

Despite these challenges, Aristotle’s physics was dominant in European universities into the late seventeeth century.