Scientific American articles

Astrophysics"Collapse and Formation of Stars" by A.P. Boss, January 1985
"The Great Supernova of 1987" by S. Woosley and T. Weaver, August 1989
"Black Holes in Galactic Centers" by M.J. Rees, November 1990
"The Expansion Rate and Size of the Universe" by W.L. Freedman, November 1992
"The Ghostliest Galaxies" by Gregory D. Bothun, February 1997

Atomic and Molecular Physics
"Detecting Individual Atoms and Molecules with Lasers" by V.S. Letokhov, September 1988
"The Birth of Molecules" by A.H. Zewail, December 1990
"Friction at the Atomic Scale" by Jacqueline Krim, October 1996

Biophysics and Medical Physics
"Advances in Tumor Imaging" by Maryellen L. Giger and Charles A. Pelizzari, September 1996
"The Machinery of Thought" by Tim Beardsley, August 1997
Solid State Physics
"Ion Implantation of Surfaces" by S.T. Picraux and P.S. Peercy, March 1985
"Crystals at High Pressure" by R.M. Hazen and L.W. Finger, May 1985
"Advanced Metals" by B.H. Kear, October 1986
"Quantum Dots" by M.A. Reed, January 1993

Classical physics

t is also useful to distinguish classical physics and modern physics. Classical physics has its origins approximately four hundred years ago in the studies of Galileo and Newton on mechanics, and similarly, in the work of Ampere, Faraday,Maxwell and Oersted one hundred fifty years ago in the fields of electricity and magnetism. This physics handles objects which are neither too large nor too small, which move at relatively slow speeds (at least compared to the speed of light: 186,000 miles per second!).
The emergence of modern physics at the beginning of the twentieth century was marked by three achievements. The first, in 1905, was Einstein's brilliant model of light as a stream of particles (photons). The second, which followed a few months later, was his revolutionary theory of relativity which described objects moving at speeds close to the speed of light. The third breakthrough came in 1910 with Rutherford's discovery of the nucleus of the atom.Rutherford's work was followed by Bohr'smodel of the atom, which in turn stimulated the work of de Broglie, Heisenberg, Schroedinger, Born, Pauli, Dirac and others on the quantum theory. The avalanche of exciting discoveries in modern physics continues today.
Given these distinctions within the field of physics experimental and theoretical, classical and modern it is useful to further subdivide physics into various disciplines, including astrophysics, atomic and molecular physics, biophysics, solid state physics, optical and laser physics, fluid and plasma physics, nuclear physics, and particle physics.

What is Physics ?

Physics is often described as the study of matter and energy. It is concerned with how matter and energy relate to each other, and how they affect each other over time and through space. Physicists ask the fundamental questions how did the universe begin? how and of what is it made? how does it change? what rules govern its behavior?
Physicists may be roughly divided into two camps: experimental physicists and theoretical physicists. Experimental physicists design and run careful investigations on a broad range of phenomena in nature, often under conditions which are atypical of our everyday lives. They may, for example, investigate what happens to the electrical properties of materials at temperatures very near absolute zero (­460 degrees Fahrenheit) or measure the characteristics of energy emitted by very hot gases. Theoretical physicists propose and develop models and theories to explain mathematically the results of experimental observations. Experiment and theory therefore have a broad overlap. Accordingly, an experimental physicist remains keenly aware of the current theoretical work in his or her field, while the theoretical physicist must know the experimenter's results and the context in which the results need be interpreted.

High energy/particle physics

High energy/particle physics

Particle physics is the study of the elementary constituents of matter and energy, and theinteractions between them. It may also be called "high energy physics", because many elementary particles do not occur naturally, but are created only during high energy collisions of other particles, as can be detected in particle accelerators.

Currently, the interactions of elementary particles are described by the Standard Model. The model accounts for the 12 known particles of matter (quarks and leptons) that interact via thestrong, weak, and electromagnetic fundamental forces. Dynamics are described in terms of matter particles exchanging gauge bosons (gluons, W and Z bosons, and photons, respectively). The Standard Model also predicts a particle known as the Higgs boson, the existence of which has not yet been verified; as of 2010, searches for it are underway in the Tevatron at Fermilab and in theLarge Hadron Collider at CERN.

The Big Bang was confirmed by the success of Big Bang nucleosynthesis and the discovery of the cosmic microwave background in 1964. The Big Bang model rests on two theoretical pillars: Albert Einstein's general relativity and the cosmological principle. Cosmologists have recently established the ΛCDM model of the evolution of the universe, which includes cosmic inflation, dark energy and dark matter.

Numerous possibilities and discoveries are anticipated to emerge from new data from the Fermi Gamma-ray Space Telescope over the upcoming decade and vastly revise or clarify existing models of the Universe.^[36][37] In particular, the potential for a tremendous discovery surrounding dark matter is possible over the next several years.^[38] Fermi will search for evidence that dark matter is composed of weakly interacting massive particles, complementing similar experiments with the Large Hadron Collider and other underground detectors.

Astrophysics

Astrophysics

Astrophysics and astronomy are the application of the theories and methods of physics to the study of stellar structure, stellar evolution, the origin of the solar system, and related problems of cosmology. Because astrophysics is a broad subject, astrophysicists typically apply many disciplines of physics, including mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum mechanics, relativity, nuclear and particle physics, and atomic and molecular physics.

The discovery by Karl Jansky in 1931 that radio signals were emitted by celestial bodies initiated the science of radio astronomy. Most recently, the frontiers of astronomy have been expanded by space exploration. Perturbations and interference from the earth’s atmosphere make space-based observations necessary for infrared, ultraviolet, gamma-ray, and X-ray astronomy.

Physical cosmology is the study of the formation and evolution of the universe on its largest scales. Albert Einstein’s theory of relativity plays a central role in all modern cosmological theories. In the early 20th century, Hubble's discovery that the universe was expanding, as shown by the Hubble diagram, prompted rival explanations known as the steady stateuniverse and the Big Bang.

The Big Bang was confirmed by the success of Big Bang nucleosynthesis and the discovery of the cosmic microwave background in 1964. The Big Bang model rests on two theoretical pillars: Albert Einstein's general relativity and the cosmological principle. Cosmologists have recently established the ΛCDM model of the evolution of the universe, which includes cosmic inflation, dark energy and dark matter.

Numerous possibilities and discoveries are anticipated to emerge from new data from the Fermi Gamma-ray Space Telescope over the upcoming decade and vastly revise or clarify existing models of the Universe.^[36][37] In particular, the potential for a tremendous discovery surrounding dark matter is possible over the next several years.^[38] Fermi will search for evidence that dark matter is composed of weakly interacting massive particles, complementing similar experiments with the Large Hadron Collider and other underground detectors.

Current research

Current research

Research in physics is continually progressing on a large number of fronts.

In condensed matter physics, an important unsolved theoretical problem is that of high-temperature superconductivity. Many condensed matter experiments are aiming to fabricate workable spintronics and quantum computers.

In particle physics, the first pieces of experimental evidence for physics beyond the Standard Model have begun to appear. Foremost among these are indications that neutrinos have non-zeromass. These experimental results appear to have solved the long-standing solar neutrino problem, and the physics of massive neutrinos remains an area of active theoretical and experimental research. Particle accelerators have begun probing energy scales in the TeV range, in which experimentalists are hoping to find evidence for the Higgs boson and supersymmetric particles.^[40]

Theoretical attempts to unify quantum mechanics and general relativity into a single theory ofquantum gravity, a program ongoing for over half a century, have not yet been decisively resolved. The current leading candidates are M-theory, superstring theory and loop quantum gravity.

Many astronomical and cosmological phenomena have yet to be satisfactorily explained, including the existence of ultra-high energy cosmic rays, the baryon asymmetry, the acceleration of the universe and the anomalous rotation rates of galaxies.

Although much progress has been made in high-energy, quantum, and astronomical physics, many everyday phenomena involving complexity, chaos, or turbulence are still poorly understood.^{[citation needed]} Complex problems that seem like they could be solved by a clever application of dynamics and mechanics remain unsolved; examples include the formation of sandpiles, nodes in trickling water, the shape of water droplets, mechanisms of surface tensioncatastrophes, and self-sorting in shaken heterogeneous collections.^{[citation needed]}

References

References

1. ^ Richard Feynman begins his Lectures with the atomic hypothesis, as his most compact statement of all scientific knowledge: "If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generations ..., what statement would contain the most information in the fewest words? I believe it is ... that all things are made up of atoms – little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. ..." R.P. Feynman, R.B. Leighton, M. Sands (1963). The Feynman Lectures on Physics. 1. p. I-2. ISBN 0-201-02116-1.
2. ^ J.C. Maxwell (1878). Matter and Motion. D. Van Nostrand. p. 9.ISBN 0486668959. "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular succession of event                                                                         s."
3. ^ H.D. Young, R.A. Freedman (2004). University Physics with Modern Physics (11th ed.). Addison Wesley. p. 2. "Physics is anexperimental science. Physicists observe the phenomena of nature and try to find patterns and principles that relate these phenomena. These patterns are called physical theories or, when they are very well established and of broad use, physical laws or principles."
4. ^ S. Holzner (2006). Physics for Dummies. Wiley. p. 7.ISBN 0470618418. "Physics is the study of your world and the world and universe around you."
5. ^ Note: The term 'universe' is defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them. However, the term 'universe' may also be used in slightly different contextual senses, denoting concepts such as thecosmos or the philosophical world.
6. ^ Evidence exists that the earliest civilizations dating back to beyond 3000 BCE, such as the Sumerians, Ancient Egyptians, and the Indus Valley Civilization, all had a predictive knowledge and a very basic understanding of the motions of the Sun, Moon, and 

DISCLAIMER

DISCLAIMER

The demonstrations and other descriptions of procedures and use of equipment in this book have been compiled from sources believed to be reliable and to represent the best opinion on the subject as of 1990. However, no warranty, guarantee or representation is made by the author as to the correctness or sufficiency of any information herein. The author does not assume any responsibility or liability for the use of the information herein, nor can it be assumed that all necessary warnings and precautionary measures are contained in this publication. Other or additional information or measures may be required or desirable because of particular or exceptional conditions or circumstances, or because of new or changed legislation. Teachers and demonstrators must develop and follow procedures for the safe performance of the demonstrations in accordance with local regulations and requirements.
This preliminary, partial manuscript is a very early, incomplete version of a published book. The much more extensive, heavily illustrated, and up-to-date, full-color, 300-page version was published by the University of Wisconsin Press in 2006 and can be ordered here. You may copy this material for your personal use. Further distribution or commercial use requires permission of the author.
In the matter of physics, the first lessons should contain nothing but what is experimental and interesting to see. A pretty experiment is in itself often more valuable than twenty formulae extracted from our minds.*