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Thursday, July 25, 2013

Black-Body Radiation and Gravity

Blackbody radiation induces attractive force stronger than gravity
Artistic visualization of the interaction between an atom and a Black-Body. Due to the atractive force of the Black-Body, the atom is pulled to the direction of this body. Credit: M. Sonnleitner, et al. ©2013 American Physical Society
The black-body objects are perfect not-reflectors that produce constant radiation when they are at a uniform temperature. Thus, the properties of a black-body depends on its temperature, thinking that this radiation would have a repulsive effect. Now a new, scientists have demonstrated theoretically that black-body radiation induces a second force in atoms and molecules that are near its surface which is attractive and stronger than the repulsive radiation pressure. Consequently, the atoms and molecules are pulled to the surface of the black-body by a force which may be greater than gravity. The new attractive force - what scientists describe as "black-body force" - suggests that a variety of astrophysical scenarios need to be revisited.
blackbody_radn_curves_Swinburne University of Technology
À medida que a temperatura diminui, o pico da curva da radiação de um corpo negro se desloca para menores intensidades e maiores comprimentos de onda.
Scientist identify a few interesting results in their formulation. First, this force decays with the third power of the distance to the black-body (F ∝ 1/r3). Second, it is more stronger for small objects. Third, the force is more stronger for warmer objects. Above a few thousand degrees Kelvin, the force of attraction changes to repulsion.
In their study, scientists demonstrated that the strength of the black-body in a grain of dust, at a temperature of 100 K, is much stronger than the gravitational force in this grain. However, for a massive star at a temperature of 6000 K black-body force is much weaker than the gravitational force.
Scientific Article: M. Sonnleitner, et al. “Attractive Optical Forces from Blackbody Radiation.” PRL 111, 023601 (2013). DOI: 10.1103/PhysRevLett.111.023601
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