I Thermodynamics - Stanford University
... The idea of our knowledge of information of a system is closely related to a quantity called entropy. Entropy is often cloaked in mysterious double talk from those not familiar with the concept. There are three basic ways to define entropy. At the most basic level, entropy is a measure of the numbe ...
... The idea of our knowledge of information of a system is closely related to a quantity called entropy. Entropy is often cloaked in mysterious double talk from those not familiar with the concept. There are three basic ways to define entropy. At the most basic level, entropy is a measure of the numbe ...
worksheet
... hole solution was a blemish to be removed from the theory by a better mathematical formulation, not a consequence to be tested by observation. He never expressed the slightest enthusiasm for black holes, either as a concept or a physical possibility.” Freeman Dyson quoted in ‘Just Six Numbers’ by Ma ...
... hole solution was a blemish to be removed from the theory by a better mathematical formulation, not a consequence to be tested by observation. He never expressed the slightest enthusiasm for black holes, either as a concept or a physical possibility.” Freeman Dyson quoted in ‘Just Six Numbers’ by Ma ...
Black Holes : A lecture to 6th Formers
... Back in the early 1970’s it was realised that if a black hole was truly black, then it had to carry entropy. Entropy measures disorder, and it always increases in any physical process. But if a black hole was a thermodynamic object, then surely it had to be a black body: it had to radiate. Bekenstei ...
... Back in the early 1970’s it was realised that if a black hole was truly black, then it had to carry entropy. Entropy measures disorder, and it always increases in any physical process. But if a black hole was a thermodynamic object, then surely it had to be a black body: it had to radiate. Bekenstei ...
Word doc - UC-HiPACC - University of California, Santa Cruz
... system) and a mass triple Earth’s. G2’s dust is warm—550K, about twice Earth’s temperature; its gas is 10,000K, twice as hot as our Sun. But G2 is far cooler than the heated, rarefied gas at the galactic center. Because cool clouds in such a hostile environment evaporate, G2 either formed shortly be ...
... system) and a mass triple Earth’s. G2’s dust is warm—550K, about twice Earth’s temperature; its gas is 10,000K, twice as hot as our Sun. But G2 is far cooler than the heated, rarefied gas at the galactic center. Because cool clouds in such a hostile environment evaporate, G2 either formed shortly be ...
Document
... gamma ray bursts have been found to be associated with the deaths of very large stars. The favored models for these is the “core collapse supernova,” where the massive core of the star collapses into a black hole and black hole accretion powers a luminous jet. Despite numerous observations, many of ...
... gamma ray bursts have been found to be associated with the deaths of very large stars. The favored models for these is the “core collapse supernova,” where the massive core of the star collapses into a black hole and black hole accretion powers a luminous jet. Despite numerous observations, many of ...
Black body
A black body (also blackbody) is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. A white body is one with a ""rough surface [that] reflects all incident rays completely and uniformly in all directions.""A black body in thermal equilibrium (that is, at a constant temperature) emits electromagnetic radiation called black-body radiation. The radiation is emitted according to Planck's law, meaning that it has a spectrum that is determined by the temperature alone (see figure at right), not by the body's shape or composition.A black body in thermal equilibrium has two notable properties:It is an ideal emitter: at every frequency, it emits as much energy as – or more energy than – any other body at the same temperature.It is a diffuse emitter: the energy is radiated isotropically, independent of direction.An approximate realization of a black surface is a hole in the wall of a large enclosure (see below). Any light entering the hole is reflected indefinitely or absorbed inside and is unlikely to re-emerge, making the hole a nearly perfect absorber. The radiation confined in such an enclosure may or may not be in thermal equilibrium, depending upon the nature of the walls and the other contents of the enclosure.Real materials emit energy at a fraction—called the emissivity—of black-body energy levels. By definition, a black body in thermal equilibrium has an emissivity of ε = 1.0. A source with lower emissivity independent of frequency often is referred to as a gray body.Construction of black bodies with emissivity as close to one as possible remains a topic of current interest.In astronomy, the radiation from stars and planets is sometimes characterized in terms of an effective temperature, the temperature of a black body that would emit the same total flux of electromagnetic energy.