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	Radiation pressure - Wikipedia, the free encyclopedia
		Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation.
		It may be shown by electromagnetic theory, by quantum theory, or by thermodynamics, making no assumptions as to the nature of the radiation, that the pressure against a surface exposed in a space traversed by radiation uniformly in all directions is equal to ⅓ the total radiant energy per unit volume within that space.
		In acoustics, radiation pressure is the unidirectional pressure force exerted at an interface between two media due to the passage of a sound wave.
	en.wikipedia.org /wiki/Radiation_pressure (593 words)

	radiation pressure
		The minute pressure exerted on a surface at right-angles to the direction of travel of the incident electromagnetic radiation.
		In quantum mechanics, radiation pressure can be interpreted as the transfer of momentum from photons as they strike a surface.
		Radiation pressure on dust grains in space can dominate over gravity and explains why the tail of a comet always points away from the Sun.
	www.daviddarling.info /encyclopedia/R/radpressure.html (150 words)

	Radiation Pressure
		The fact that electromagnetic radiation exerts a pressure upon any surface exposed to it was deduced theoretically by the father of electromagnetic theory James Clerk Maxwell in 1871, and later on, proven experimentally by Lebedev in 1900 and by Nichols and Hull in 1901.
		Electromagnetic radiation pressure is proportional to the energy intensity of the EM field, and inversely proportional to the speed of light.
		So, in order for radiation pressure to equate to the effects of gravity, we should find a condition for radiation pressure coefficient to be the same for all matter, so that the net force will depend on mass, that is the number of elementary targets within a particle or material body.
	www.blazelabs.com /f-g-rpress.asp (3257 words)

	observational redshifts
		With an initially uniform radiation energy density and, as a result of the radial behavior of the curvature component, the region internal to the collapse boundary is cut off from the expanding external region since the temporal expansion rate, dx/dt, goes to zero at this boundary (zero propagation velocity).
		Pressure inside the hole region is large and negative and at the hole edge approaches the singularity.
		Pressure function versus radius for the case of the hole mass equal to the experimental value (subscript 1) and for the hole radius equal to the sphere radius (subscript 3) where the singularity at the hole boundary has merged with the zero at the sphere radius.
	home.att.net /~dale.r.koehler/cosmologicalpressurefluctuations.htm (5432 words)

	radiation pressure (Site not responding. Last check: 2007-10-10)
		Pressure as momentum flux per area can be extended to the case of radiation.
		Note that for the ideal gas of nonrelativistic particles, the pressure is 2/3 the kinetic energy density.
		For relativistic particles, the pressure is 1/3 the kinetic energy density -- the photon gas is an example.
	www.aoc.nrao.edu /~jweather/physics425/node7.html (106 words)

	Blackbody Radiation
		A uniform background radiation in the microwave region of the spectrum is observed in all directions in the sky.
		The discovery of the 3K microwave background radiation was one of the crucial steps leading to the calculation of the standard "Big Bang" model of cosmology, its role being that of providing estimates of relative populations of particles and photons.
		The scale of the fluctuations is larger than the horizon at the time the background radiation was emitted, indicating that the fluctuations are primordial, dating from a time before the separation of radiation and matter, the transparency point.
	hyperphysics.phy-astr.gsu.edu /hbase/bkg3k.html (947 words)

	The Pressure of Light
		When radiation pressure is calculated for a given source and body, (the Sun and Earth for example) it is very small.
		Using (2), the radiation pressure at the surface of the sun is only.214N/m^2.
		The astrological effect of radiation pressure is enough to affect comets and deep space probes [1].
	www.u.arizona.edu /~lilley98 (912 words)

	P. N. Lebedev and light radiation pressure
		According to this hypothesis the solar ray pressure is responsible for the deflection of the comet tails.
		For example, it has been found that stellar radiation pressure is one of the most important mechanisms responsible for particle dynamics in the interstellar medium.
		The difference in pressure was responsible for the creation of a torque on the rod so that the hanging spring of the rod was twisted.
	www.europhysicsnews.com /full/07/article4/article4.html (1284 words)

	Theoretical Principles of Plasma Physics and Atomic Physics
		Emission Rate: The intensity of radiation emitted during a discrete atomic transition is determined by the Level Population and the Atomic Decay Probability.
		For sufficiently small radiation intensities, the photoionization cross section will be reduced due to the plasma field fluctuations (see Absorption) and the increase of the ionization time in comparison to the coherence time of the radiation (see Photons).
		Deriving a radiation pressure by means of the conservation laws would therefore be an unallowed generalization from classical mechanics and indeed violate the experimental fact of the constancy of the speed of light.
	www.plasmaphysics.org.uk (7930 words)

	Radiation Pressure - Emmy Noether Research Group
		Depending on the properties of the dust particles and the radiation field of the central star the radiation pressure in radial direction can exceed the gravitational attraction and force the dust grains on an unbound trajectory.
		fluffy dust aggregates, there are also transversal components of radiation pressure that have an impact on the particle motion perpendicular to the direction of incident light.
		The experimental setup that we have developed allows for measuring the radiation pressure forces exerted on an individual micron-size dust particle in directions parallel and perpendicular to the incident light.
	www.uni-muenster.de /Planetologie/en/groups/emmy/radiationpressure.html (333 words)

	Radiation Pressure....
		When the radiation, which has momentum, is absorbed or reflected from a surface then the radiation exchanges momentum with the wall.
		Radiation pressure is this force per unit area.
		But photon momentum, which is equivalent to radiation pressure, explains why the sphere doesn't fall on the ground.
	www.physicsforums.com /showthread.php?p=294435 (1688 words)

	Matter, Energy, and Radiation Hydrodynamics
		That is, pressure is proportional to the average particle kinetic energy and the particle density, or equal to two-thirds of the total kinetic energy, KE, in a given volume of gas (the kinetic energy density).
		The negative pressure generated by the binding forces is exactly balanced by positive forces generated by the mutual repulsion of the outer electron shells (Coulomb repulsion) and the thermal motion of the atoms.
		The total pressure present is the sum of the Fermi pressure, the kinetic pressure of the Boltzmann gas consisting of the nuclei and non-degenerate electrons, and the pressure of the photon Bose gas.
	nuclearweaponarchive.org /Nwfaq/Nfaq3.html (20363 words)

	Radiation Pressure - Advanced Physics Forums (Site not responding. Last check: 2007-10-10)
		According to the people working on JAXA's Hayabusa mission to asteroid 25143 Itokawa, the largest force currently acting on their probe is radiation pressure due to sunlight reflecting off the probe.
		Since they plan to use the radiation pressure to assist the eventual landing of the craft, one might say that Hayabusa is the first real solar sail craft.
		There is also the Line Driven Stellar Wind model which is based on the effect of radiation pressure from the star (usually a type O, B or A star) were momentum is transferred to the ions of the outer Stellar Atmosphere.
	www.advancedphysics.org /forum/showthread.php?t=2697 (487 words)

	Gravity
		The imbalance of radiation pressure is due to the reflection of this background radiation by matter particles.
		Low pressure atmospheric systems are caused fundamentally by the absence of air pressure (relatively speaking) in the atmosphere, whereas the cause of gravity in this model is due to the absence of radiation pressure.
		As in ordinary radiation fields, the density of the long-wavelength radiation diminishes as the square of the distance from the attractive source; the radiation void of the Earth.
	www.johnkharms.com /gravitation.htm (12400 words)

	Newtonian Gravity Pressure Equation
		A difference in the radiation pressure (leading to gravity) depends upon two essential factors; as in a low pressure storm known as a hurricane, the strength of the hurricane's winds depend upon the outer local atmospheric pressure as well as the strength of the low pressure within the eye of the storm.
		So, for there to be gravity in the pressure viewpoint, the strength of gravity must depend upon the average local vacuum radiation pressure as well as the amount of matter present.
		Matter disturbs the vacuum radiation and this disturbance is essentially a lowering of the radiation pressure of the vacuum.
	www.johnkharms.com /mass.htm (2828 words)

	D Solar and Earth electromagnetic radiation and indices
		Electromagnetic radiation carries momentum and the reflection of incident radiation at a surface represents an exchange of momentum.
		The effect of this solar radiation pressure as a force acting upon the vehicle is dependent upon the reflective characteristics of the spacecraft surfaces.
		The perturbing effect upon a spacecraft's trajectory is directly dependent upon the vehicle's area to mass ratio and inversely proportional to the square of its distance from the sun.
	www.spenvis.oma.be /spenvis/ecss/annexd/annexd.html (905 words)

	CIMIS - [ Current Hourly Flags ]
		Solar radiation, air temperature or vapor pressure is flagged R. Solar radiation, air temperature or vapor pressure is severe.
		Actual vapor pressure is equal to or less than to 0.00 kPa or actual vapor pressure is greater than 1.05 times the saturation vapor pressure.
		Measured solar radiation is greater than 75 percent of calculated extraterrestrial radiation, the sun is 10 or more degrees above the horizon, and the station shows recorded precipitation (precipitation is greater than 0).
	wwwcimis.water.ca.gov /cimis/dataQcCurrentHourly.jsp (696 words)

	Gravity and Inertia via Radiation Pressure
		All forces that act through a distance are attributed to cosmic radiation pressure and shadowing of these frequencies by matter.
		A surface gravity and/or radiation pressure limit are shown to exist when the radiation flow is totally shielded by large planets.
		A multitude of combinations of the electrostatic, magnetic and inertial forces may be tried, with the objective of shielding or focusing the radiation to modify the local effects of gravity and inertia upon an object.
	home.netcom.com /~sbyers11 (846 words)

	Radiation
		The objective of this part of the investigation is to determine the stability boundaries of steady temperature profiles in optically-thick media, in particular as a function of the optical thickness parameter and Planck number, t and Pl respectively.
		is employed to obtain conditions (at high pressure) where the radiation pressure gradient may be strong enough to influence the flow, and thus enable a comparison of flows with and without significant radiation pressure effects.
		A pressure vessel was filled with SF gas and a buoyantly stable temperature gradient was created in the gap between two flat horizontal parallel plates (Fig.
	www-scf.usc.edu /~davidcla/rift2.htm (2754 words)

	EMRP Push Gravity Theory : Gravity EM Radiation Pressure Conclusion
		In this section it was shown that the source of gravity is the result of imbalance of the background EM radiations, (or photon showers in quantum terms), the main source of which are the highest frequency cosmic electromagnetic rays (blue shifted EM waves) present in our universe.
		We also know that radiation pressure is directly proportional to the magnitude of the Poynting vector in the propagating direction of an electromagnetic wave coupled to the objects radiation pressure coefficient which peaks to a value of two when its diameter is very close to the EM wavelength.
		The electromagnetic radiation pressure difference finally gives a physical meaning to Einstein's space time curvature, and the electromagnetic radiation shows why gravity cannot exchange information faster than the speed of radiation itself, that is the speed of light.
	www.blazelabs.com /f-g-grp.asp (1611 words)

	radiation force (Site not responding. Last check: 2007-10-10)
		Radiation from a point source is a one-dimensional example.
		The pressure is given by (1/c) times the flux, and the pressure gradient is given by the Thomson cross-section times the number density of electrons.
		The gravitational force per unit volume of the radiating object can be compared with the force per unit volume of the radiation.
	www.aoc.nrao.edu /~jweather/physics425/node8.html (201 words)

	[166.05] Why Radiation Pressure Cannot Stop the Formation of Massive Stars (Site not responding. Last check: 2007-10-10)
		Radiation pressure likely presents no significant barrier to massive star formation, despite the fact that the luminosity of a massive star can greatly exceed the Eddington limit for continued accretion.
		These channel radiation away from the bulk of the gas and reduce the radiation pressure it experiences.
		The discovery of these two mechanisms implies that radiation pressure feedback is not the dominant factor in setting the final size of massive stars.
	www.aas.org /publications/baas/v36n5/aas205/226.htm (309 words)

	Gamma Radiation Measurements on the Lifter by JL Naudin
		Radiating frequencies of very short wavelengths although theoretically present under vacuum conditions ARE NOT DETECTED when lifter is operated in air.
		The frequency of the radiation pressure (in vacuum) is not the same as the frequency of the power supply driving the lifter, and is still present with a pure dc hv supply.
		The measured Gamma Radiation at 40 mm from the Lifter is
	jnaudin.free.fr /html/lftgamma.htm (679 words)

	Radiation implosion - Wikipedia, the free encyclopedia
		The term Radiation implosion describes a class of devices which use high levels of electromagnetic radiation to compress a target.
		The term "radiation implosion" suggests that the secondary is crushed by radiation pressure, and calculations show that this pressure is very large.
		The recoil from this surface layer ejection produces pressures which are an order of magnitude stronger than the simple radiation pressure.
	en.wikipedia.org /wiki/Radiation_implosion (577 words)

	Photons and Light (Site not responding. Last check: 2007-10-10)
		As early as 1619, Kepler proposed that the pressure of sunlight was responsible for blowing back a comet's tail so that it always points away from the Sun.
		We have seen that all forms of electromagnetic radiation are different aspects of one entity, the electromagnetic wave.
		Since this acceleration is centripetal acceleration, the radiation pattern forms lobes in front and behind the direction of motion.
	physics.tamuk.edu /~suson/html/4323/photons.html (3410 words)

	Radiation Pressure (Site not responding. Last check: 2007-10-10)
		Pressure is Force/Area, and Force is change in momentum with respect to time.
		Hence, electromagnetic radiation should exert a pressure on objects when it hits them.
		If the radiation reflects, then the momentum is twice and so the radiation pressure is also twice.
	www.cbu.edu /~jholmes/P251/P5waves2/tsld037.htm (60 words)

	radiation pressure
		Suppose that a perfectly reflecting circular mirror is initially at rest a distance R away from the sun and is oriented so that the solar radiation is incident upon, and perpendicular to, the plane of the mirror.
		Radiation pressure ecerted on a perfectly reflecting surface is P= 2S/c where C is the speed of light and S is the poynting vector?
		The counter-force to radiation force is the weight of the reflecting surface (mass of mirror x acceleration due to gravity (
	www.physicsforums.com /showthread.php?t=95604 (461 words)

	Radiation pressure induced EPR paradox
		By studying the properties of the output field they demonstrate that the state of the radiation field can become non-classical, giving rise to the appearance of the EPR paradox on its continuous variables.
		In the proposed experiment, in fact, the two input modes in the cavity interact by means of the radiation pressure force by which each of them acts on the mirror.
		In conclusion, the proposed scheme achieves the goal of obtaining the entanglement of radiation fields with a macroscopic number of photons, by means of a classical ponderomotive force on a macroscopic object.
	www.europhysicsnews.com /full/11/article5/article5.html (1057 words)

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