Physics for the 21st Century Course Overview Welcome to Physics for the 21st Century: an on-line course that explores the frontiers of physics. The 11 units, accompanied by videos, interactive simulations, and a comprehensive Facilitator's Guide, work together to present an overview of key areas of rapidly-advancing knowledge in the field, arranged from the sub-atomic scale to the cosmological. The goal is to make the frontiers of physics accessible to anyone with an inquisitive mind who wants to experience the excitement, probe the mystery, and understand the human aspects of modern physics. About This Course | Using This Site
Quantum Minimum amount of a physical entity involved in an interaction Etymology and discovery[edit] The word quantum is the neuter singular of the Latin interrogative adjective quantus, meaning "how much". "Quanta", the neuter plural, short for "quanta of electricity" (electrons), was used in a 1902 article on the photoelectric effect by Philipp Lenard, who credited Hermann von Helmholtz for using the word in the area of electricity. However, the word quantum in general was well known before 1900,[2] e.g. quantum was used in E. In 1901, Max Planck used quanta to mean "quanta of matter and electricity",[5] gas, and heat.[6] In 1905, in response to Planck's work and the experimental work of Lenard (who explained his results by using the term quanta of electricity), Albert Einstein suggested that radiation existed in spatially localized packets which he called "quanta of light" ("Lichtquanta").[7] Quantization[edit] See also[edit] References[edit] Further reading[edit]
A Lazy Layman's Guide to Quantum Physics That's an easy one: it's the science of things so small that the quantum nature of reality has an effect. Quantum means 'discrete amount' or 'portion'. Max Planck discovered in 1900 that you couldn't get smaller than a certain minimum amount of anything. The meaning of quantum physics is a bit of a taboo subject, but everyone thinks about it. Copenhagen Interpretation (CI) This is the granddaddy of interpretations, championed by the formidable Niels Bohr of Copenhagen university. The CI has a bit of a cheek calling itself an interpretation, because it essentially says "thou shalt not ask what happens before ye look". When you do try to take Copenhagen seriously you come to the conclusion that consciousness and particle physics are inter-related, and you rush off to write a book called The Dancing Wu-Li Masters. More recently, Henry Stapp at the University of California has written papers such as On Quantum Theories of the Mind (1997). What happens to the cat? What happens to the cat?
Configuration state function In quantum chemistry, a configuration state function (CSF), is a symmetry-adapted linear combination of Slater determinants. A CSF must not be confused with a configuration. In general, one configuration gives rise to several CSFs; all have the same total quantum numbers for spin and spatial parts but differ in their intermediate couplings. Definition[edit] A configuration state function (CSF), is a symmetry-adapted linear combination of Slater determinants. , of the system being studied. where denotes the set of CSFs. , are found by using the expansion of to compute a Hamiltonian matrix. In atomic structure, a CSF is an eigenstate of In linear molecules, does not commute with the Hamiltonian for the system and therefore CSFs are not eigenstates of . and . nor commutes with the Hamiltonian. are still valid quantum numbers and CSFs are built to be eigenfunctions of these operators. From configurations to configuration state functions[edit] CSFs are however derived from configurations. . boxes. .
Quantum mysteries John Gribbin For seventy years, physicists have worried about what quantum mechanics means. They can use quantum physics, to be sure; witness the successful designs of lasers and computer microchips, and the understanding of molecules that makes genetic engineering possible. But the equations that are a routine part of this kind of work contain one embarrassing feature. In fact, few physicists worry about such things. The archetypal example of the quantum mysteries is the "experiment with two holes", where the measured position of a single electron that passes through two holes in a screen can only be explained in terms of the wave function travelling through both holes at once and interfering with itself. Imagine that we have a source which will emit a single quantum particle in a random direction (ordinary radioactive nuclei do exactly this, so there is nothing special about the source). So far, simple enough. It works like this.
Photon Nomenclature[edit] In 1900, Max Planck was working on black-body radiation and suggested that the energy in electromagnetic waves could only be released in "packets" of energy. In his 1901 article [4] in Annalen der Physik he called these packets "energy elements". Physical properties[edit] The cone shows possible values of wave 4-vector of a photon. A photon is massless,[Note 2] has no electric charge,[13] and is stable. Photons are emitted in many natural processes. The energy and momentum of a photon depend only on its frequency (ν) or inversely, its wavelength (λ): where k is the wave vector (where the wave number k = |k| = 2π/λ), ω = 2πν is the angular frequency, and ħ = h/2π is the reduced Planck constant.[17] Since p points in the direction of the photon's propagation, the magnitude of the momentum is The classical formulae for the energy and momentum of electromagnetic radiation can be re-expressed in terms of photon events. Experimental checks on photon mass[edit]
The Everett Interpretation This FAQ shows how quantum paradoxes are resolved by the "many-worlds" interpretation or metatheory of quantum mechanics. This FAQ does not seek to that the many-worlds interpretation is the "correct" quantum metatheory, merely to correct some of the common errors and misinformation on the subject floating around. As a physics undergraduate I was struck by the misconceptions of my tutors about many-worlds, despite that it seemed to resolve all the paradoxes of quantum theory . The objections raised to many-worlds were either patently misguided or beyond my ability to assess at the time , which made me suspect (confirmed during my graduate QFT studies) that the more sophisticated rebuttals were also invalid. I hope this FAQ will save other investigators from being lead astray by authoritative statements from mentors. I have attempted, in the answers, to translate the precise mathematics of quantum theory into woolly and ambiguous English - I would appreciate any corrections. 4) [M].
Slater determinant Function that can be used to build the wave function of a multi-fermionic system In quantum mechanics, a Slater determinant is an expression that describes the wave function of a multi-fermionic system. It satisfies anti-symmetry requirements, and consequently the Pauli principle, by changing sign upon exchange of two electrons (or other fermions).[1] Only a small subset of all possible fermionic wave functions can be written as a single Slater determinant, but those form an important and useful subset because of their simplicity. The Slater determinant arises from the consideration of a wave function for a collection of electrons, each with a wave function known as the spin-orbital , where denotes the position and spin of a single electron. The Slater determinant is named for John C. Definition[edit] Two-particle case[edit] and , we have This expression is used in the Hartree method as an ansatz for the many-particle wave function and is known as a Hartree product. Multi-particle case[edit] or
Why Physicists Are Saying Consciousness Is A State Of Matter, Like a Solid, A Liquid Or A Gas — The Physics arXiv Blog There’s a quiet revolution underway in theoretical physics. For as long as the discipline has existed, physicists have been reluctant to discuss consciousness, considering it a topic for quacks and charlatans. Indeed, the mere mention of the ‘c’ word could ruin careers. That’s finally beginning to change thanks to a fundamentally new way of thinking about consciousness that is spreading like wildfire through the theoretical physics community. And while the problem of consciousness is far from being solved, it is finally being formulated mathematically as a set of problems that researchers can understand, explore and discuss. Today, Max Tegmark, a theoretical physicist at the Massachusetts Institute of Technology in Cambridge, sets out the fundamental problems that this new way of thinking raises. Tegmark’s approach is to think of consciousness as a state of matter, like a solid, a liquid or a gas. Tegmark does not have an answer.
Laser Device which emits light via optical amplification Red (660 & 635 nm), green (532 & 520 nm) and blue-violet (445 & 405 nm) lasers A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation".[1][2] The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. Lasers are used in optical disk drives, laser printers, barcode scanners, DNA sequencing instruments, fiber-optic and free-space optical communication, laser surgery and skin treatments, cutting and welding materials, military and law enforcement devices for marking targets and measuring range and speed, and in laser lighting displays for entertainment. Fundamentals Lasers are characterized according to their wavelength in a vacuum. Terminology Maser