Physics is a natural science based on experiments, measurements and mathematical analysis with the purpose of finding quantitative physical laws for everything from the nanoworld of the microcosmos to the planets, solar systems and galaxies that occupy the macrocosmos.
The laws of nature can be used to predict the behaviour of the world and all kinds of machinery. Many of the everyday technological inventions that we now take for granted resulted from discoveries in physics. The basic laws in physics are universal, but physics in our time is such a vast field that many subfields are almost regarded as separate sciences.
The early Greeks established the first quantitative physical laws, such as Archimedes’ descriptions of the principle of levers and the buoyancy of bodies in water. But they did not actually conduct experiments, and physics as science stagnated for many centuries. By the 17th century, however, Galileo Galilei and later Issac Newton helped pioneer the use of mathematics as a fundamental tool in physics, which led to advances in describing the motion of heavenly bodies, the laws of gravity and the three laws of motion.
The laws of electricity, magnetism and electromechanical waves were developed in the 1800s by Faraday and Maxwell, in particular, while many others contributed to our understanding of optics and thermodynamics.
Modern physics can be said to have started around the turn of the 20th century, with the discovery of X-rays (Röntgen 1895), radioactivity (Becquerel 1896), the quantum hypothesis (Planck 1900), relativity (Einstein 1905) and atomic theory (Bohr 1913).
Quantum mechanics (Heisenberg and Schrödinger), beginning in 1926, also gave scientists a better understanding of chemistry and solid state physics, which in turn has led to new materials and better electronic and optical components. Nuclear and elementary particle physics have become important fields, and particle physics is now the basis for astrophysics and cosmology.