Supernova A supernova (abbreviated SN, plural SNe after "supernovae") is a stellar explosion that is more energetic than a nova. It is pronounced /ˌsuːpəˈnoʊvə/ with the plural supernovae /ˌsuːpəˈnoʊviː/ or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. During this interval a supernova can radiate as much energy as the Sun is expected to emit over its entire life span. The explosion expels much or all of a star's material at a velocity of up to 30,000 km/s (10% of the speed of light), driving a shock wave into the surrounding interstellar medium. This shock wave sweeps up an expanding shell of gas and dust called a supernova remnant. Nova means "new" in Latin, referring to what appears to be a very bright new star shining in the celestial sphere; the prefix "super-" distinguishes supernovae from ordinary novae which are far less luminous. Discovery
Subatomic particle In the physical sciences, subatomic particles are particles smaller than atoms. (although some subatomic particles have mass greater than some atoms). There are two types of subatomic particles: elementary particles, which according to current theories are not made of other particles; and composite particles. Particle physics and nuclear physics study these particles and how they interact. In particle physics, the concept of a particle is one of several concepts inherited from classical physics. Interactions of particles in the framework of quantum field theory are understood as creation and annihilation of quanta of corresponding fundamental interactions. Classification By statistics By composition The elementary particles of the Standard Model include: Various extensions of the Standard Model predict the existence of an elementary graviton particle and many other elementary particles. By mass All composite particles are massive. Other properties
Electron History In the early 1700s, Francis Hauksbee and French chemist Charles François de Fay independently discovered what they believed were two kinds of frictional electricity—one generated from rubbing glass, the other from rubbing resin. From this, Du Fay theorized that electricity consists of two electrical fluids, vitreous and resinous, that are separated by friction, and that neutralize each other when combined. A decade later Benjamin Franklin proposed that electricity was not from different types of electrical fluid, but the same electrical fluid under different pressures. He gave them the modern charge nomenclature of positive and negative respectively. Franklin thought of the charge carrier as being positive, but he did not correctly identify which situation was a surplus of the charge carrier, and which situation was a deficit. Discovery A beam of electrons deflected in a circle by a magnetic field Robert Millikan Atomic theory
Net present value In finance, the net present value (NPV) or net present worth (NPW) of a time series of cash flows, both incoming and outgoing, is defined as the sum of the present values (PVs) of the individual cash flows of the same entity. In the case when all future cash flows are incoming (such as coupons and principal of a bond) and the only outflow of cash is the purchase price, the NPV is simply the PV of future cash flows minus the purchase price (which is its own PV). NPV is a central tool in discounted cash flow (DCF) analysis and is a standard method for using the time value of money to appraise long-term projects. Used for capital budgeting and widely used throughout economics, finance, and accounting, it measures the excess or shortfall of cash flows, in present value terms, above the cost of funds. NPV can be described as the “difference amount” between the sums of discounted: cash inflows and cash outflows. Formula where – the time of the cash flow ) where is given by: Example
Steven Weinberg Steven Weinberg (born May 3, 1933) is an American theoretical physicist and Nobel laureate in Physics for his contributions with Abdus Salam and Sheldon Glashow to the unification of the weak force and electromagnetic interaction between elementary particles. Biography Steven Weinberg was born in 1933 in New York City and graduated from Bronx High School of Science in 1950. He was in the same graduating class as Sheldon Glashow, whose own research, independent of Weinberg's, would result in them (and Abdus Salam) sharing the same 1979 Nobel in Physics (see below). Weinberg received his bachelor's degree from Cornell University in 1954, living at the Cornell branch of the Telluride Association. He left Cornell and went to the Niels Bohr Institute in Copenhagen where he started his graduate studies and research. Academic career In 1966, Weinberg left Berkeley and accepted a lecturer position at Harvard. Other intellectual contributions Political ideas Personal
Gamma-ray burst Artist's illustration showing the life of a massive star as nuclear fusion converts lighter elements into heavier ones. When fusion no longer generates enough pressure to counteract gravity, the star rapidly collapses to form a black hole. Theoretically, energy may be released during the collapse along the axis of rotation to form a gamma-ray burst. Gamma-ray bursts (GRBs) are flashes of gamma rays associated with extremely energetic explosions that have been observed in distant galaxies. They are the brightest electromagnetic events known to occur in the universe. Bursts can last from ten milliseconds to several minutes. Most observed GRBs are believed to consist of a narrow beam of intense radiation released during a supernova or hypernova as a rapidly rotating, high-mass star collapses to form a neutron star, quark star, or black hole. History Positions on the sky of all gamma-ray bursts detected during the BATSE mission. Counterpart objects as candidate sources
Fundamental interaction Fundamental interactions, also called fundamental forces or interactive forces, are modeled in fundamental physics as patterns of relations in physical systems, evolving over time, that appear not reducible to relations among entities more basic. Four fundamental interactions are conventionally recognized: gravitational, electromagnetic, strong nuclear, and weak nuclear. Everyday phenomena of human experience are mediated via gravitation and electromagnetism. The strong interaction, synthesizing chemical elements via nuclear fusion within stars, holds together the atom's nucleus, and is released during an atomic bomb's detonation. The weak interaction is involved in radioactive decay. (Speculations of a fifth force—perhaps an added gravitational effect—remain widely disputed.) In modern physics, gravitation is the only fundamental interaction still modeled as classical/continuous (versus quantum/discrete). Overview of the fundamental Interaction The interactions
Fermion Antisymmetric wavefunction for a (fermionic) 2-particle state in an infinite square well potential. In particle physics, a fermion is a particle that follows Fermi–Dirac statistics. These particles obey the Pauli exclusion principle. Fermions include all quarks and leptons, as well as all composite particles made of an odd number of these, such as all baryons and many atoms and nuclei. Fermions differ from bosons, which obey Bose–Einstein statistics. In addition to the spin characteristic, fermions have another specific property: they possess conserved baryon or lepton quantum numbers. As a consequence of the Pauli exclusion principle, only one fermion can occupy a particular quantum state at any given time. Composite fermions, such as protons and neutrons, are the key building blocks of everyday matter. The name fermion was coined by English theoretical physicist Paul Dirac from the surname of Italian physicist Enrico Fermi. Elementary fermions Composite fermions Notes
What are Present Value and Future Value Finance is all about time and risk. It’s basically a study of how people make decisions regarding the allocation of resources over time and the handling of risks of them. Playing with it requires some very fundamental techniques and strategies, which are all indispensable if not enough for success in financial markets. And the idea of present value is one of the most important that will help you value financial assets over time thus making choices between current resources and future gains. First off, money today is always more valuable than the same amount of money future. This is because you can always deposit that money in bank and roll it into a bigger amount by earning interest. Therefore, the present value of $112.5 3 years from now is $100. Present value is the amount of money today that would be needed to produce, using prevailing interest rates, a given future amount of money. In the example of $100, the future value of $100 after 3 years is $112.5. MFV = (1 + r)N * MPV Example 1
Weak isospin In particle physics, weak isospin is a quantum number relating to the weak interaction, and parallels the idea of isospin under the strong interaction. Weak isospin is usually given the symbol T or I with the third component written as or The weak isospin conservation law relates the conservation of ; all weak interactions must preserve . (electric charge), is conserved. is more important than T and often the term "weak isospin" refers to the "3rd component of weak isospin". Relation with chirality and can be grouped into doublets with that behave the same way under the weak interaction. and always transform into down-type quarks (d, s, b), which have , and vice versa. . and a neutrino (νe, νμ, ντ) with . Fermions with positive chirality (“right-handed” fermions) and anti-fermions with negative chirality (“left-handed” anti-fermions) have and form singlets that do not undergo weak interactions. Electric charge, , is related to weak isospin, , and weak hypercharge, , by See also
Hypernova Eta Carinae, in the constellation of Carina, one of the nearer candidates for a future hypernova A hypernova (pl. hypernovae) is a type of supernova explosion with an energy substantially higher than that of standard supernovae. An alternative term for most hypernovae is "superluminous supernovae" (SLSNe). Such explosions are believed to be the origin of long-duration gamma-ray bursts. Just like supernovae in general, hypernovae are produced by several different types of stellar explosion: some well modelled and observed in recent years, some still tentatively suggested for observed hypernovae, and some entirely theoretical. The word collapsar, short for collapsed star, was formerly used to refer to the end product of stellar gravitational collapse, a stellar-mass black hole. History of the term Before the 1990s, the term "hypernova" was used sporadically to describe the theoretical extremely energetic explosions of extremely massive population III stars. Gamma-ray bursts
Flavour (particle physics) In particle physics, flavour or flavor refers to a species of an elementary particle. The Standard Model counts six flavours of quarks and six flavours of leptons. They are conventionally parameterized with flavour quantum numbers that are assigned to all subatomic particles, including composite ones. For hadrons, these quantum numbers depend on the numbers of constituent quarks of each particular flavour. In atomic physics the principal quantum number of an electron specifies the electron shell in which it resides, which determines the energy level of the whole atom. In an analogous way, the five flavour quantum numbers of a quark specify which of six flavours (u, d, s, c, b, t) it has, and when these quarks are combined this results in different types of baryons and mesons with different masses, electric charges, and decay modes. If there are two or more particles which have identical interactions, then they may be interchanged without affecting the physics. Jump up ^ See table in S.
Lepton A lepton is an elementary, spin-1⁄2 particle that does not undergo strong interactions, but is subject to the Pauli exclusion principle. The best known of all leptons is the electron, which governs nearly all of chemistry as it is found in atoms and is directly tied to all chemical properties. Two main classes of leptons exist: charged leptons (also known as the electron-like leptons), and neutral leptons (better known as neutrinos). Charged leptons can combine with other particles to form various composite particles such as atoms and positronium, while neutrinos rarely interact with anything, and are consequently rarely observed. The first charged lepton, the electron, was theorized in the mid-19th century by several scientists and was discovered in 1897 by J. J. Thomson. The next lepton to be observed was the muon, discovered by Carl D. Leptons are an important part of the Standard Model. Etymology Following a suggestion of Prof. History Properties
Id, ego and super-ego Although the model is structural and makes reference to an apparatus, the id, ego and super-ego are purely symbolic concepts about the mind and do not correspond to actual somatic structures of the brain (such as the kind dealt with by neuroscience). The concepts themselves arose at a late stage in the development of Freud's thought: the "structural model" (which succeeded his "economic model" and "topographical model") was first discussed in his 1920 essay Beyond the Pleasure Principle and was formalized and elaborated upon three years later in his The Ego and the Id. Freud's proposal was influenced by the ambiguity of the term "unconscious" and its many conflicting uses. Id According to Freud the id is unconscious by definition: In the id, "contrary impulses exist side by side, without cancelling each other out. ... Developmentally, the id precedes the ego; i.e., the psychic apparatus begins, at birth, as an undifferentiated id, part of which then develops into a structured ego.