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Lab group led by Nobelist Eric Cornell confirms ZPF Casimir Effect (Physics News Update, 7feb07)
Originally posted on sciy.org by Ron Anastasia on Mon 12 Feb 2007 03:59 PM PST
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Number 811 #1, February 7, 2007 by Phil Schewe, Ben Stein, and Davide Castelvecchi
The Casimir Effect Heats Up
For the first time, a group led by
Nobel laureate Eric Cornell at the National Institute of Standards
and Technology and the University of Colorado in Boulder has
confirmed a 1955 prediction, by physicist Evgeny Lifschitz, that
temperature affects the Casimir force, the attraction between two
objects when they come to within 5 millionths of a meter
(approximately 1/5,000 of an inch) of each other or less. These
efforts heighten the understanding of the force and enable future
experiments to better account for its effects.
Tiny as it is, the
Casimir effect causes parts in nano- and microelectromechanical
systems (NEMS and MEMS) to stick together. It confounds tabletop
experimental efforts to detect exotic new forces beyond those
predicted by Newtonian gravity and the Standard Model of particle
physics.
In their work, the researchers investigated the Casimir-Polder
force, the attraction between a neutral atom and a nearby surface.
The Colorado group sent ultracold rubidium atoms to within a few
microns of a glass surface. Doubling the temperature of the glass to
600 degrees Kelvin while keeping the surroundings near room
temperature caused the glass to increase its attractive force
threefold, confirming theoretical predictions recently made by the
group's theorist co-authors in Trento, Italy.
What was happening here? The Casimir force arises from effects of
the vacuum (empty space). According to quantum mechanics, the
vacuum contains fleeting electromagnetic waves, in turn consisting
of electric and magnetic fields. The electric fields can slightly
rearrange the charge in atoms. Such "polarized" atoms can then feel
a force from an electric field. The vacuum's electric fields are
altered by the presence of the glass, creating a region of maximum
electric field that attracts the atoms. In addition, heat inside
the glass also drives the fleeting electromagnetic waves, some of
which leak onto the surface as "evanescent waves." These evanescent
waves have a maximum electric field on the surface and further
attract the atoms.
Electromagnetic waves from heat in the rest of
the environment would usually cancel out the thermal attraction from
the glass surface. However, dialing up the temperature on the glass
tilts the playing field in favor of glass's thermal force and
heightens the attraction between the wall and the atoms.
Obrecht et al.,
Physical Review Letters, 9 February 2007
Also see the NIST press release
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