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Quantum Mechanics

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  • snhicks1000
    Welcome to the Yahoo! Message Board for Quantum Mechanics
    Message 1 of 218 , May 18, 2000
      Welcome to the Yahoo! Message Board for Quantum Mechanics
    • Snhicks
      http://news.bbc.co.uk/2/hi/science/nature/8133806.stm Planck achieves ultra-cold state PLANCK SPACE TELESCOPE Planck is now the coolest thing in space Planck
      Message 218 of 218 , Jul 8 6:39 AM

        Planck achieves ultra-cold state
        Planck is now the "coolest thing in space"
        Planck will survey the famous Cosmic Microwave Background
        This ancient light's origins date to 380,000 years after the Big Bang
        It informs scientists about the age, shape and evolution of the cosmos
        Planck's measurements will be finer than any previous satellite

        Europe's Planck observatory has reached its operating temperature, making it the coldest object in space.

        The observatory's detectors have been chilled to a staggering minus 273.05C - just a tenth of a degree above what scientists term "absolute zero."

        Launched in May, Planck will survey the "oldest light" in the Universe.

        Its detectors, or bolometers, should see detail in this radiation that offers new insights into the age, contents and evolution of the cosmos.

        Although laboratory set-ups have got closer to absolute zero than Planck, researchers say it is unlikely there is anywhere in space currently that is colder than their astronomical satellite.

        This frigidity should ensure the bolometers will be at their most sensitive as they scan the sky for the target light.

        The remarkable conditions are maintained, in part, by always pointing Planck away from the heat of the Sun. Shields and baffling get the telescope down to about -220C.

        Three active refrigeration systems then lower the onboard environment at the heart of the observatory extremely close to the state of zero heat energy - when, theoretically, atoms would stop moving.

        Planck has been sent to an observation position some 1.5 million km from Earth. Its first data release is expected next year.

        The European Space Agency mission was launched along with another telescope called Herschel. This second observatory is sensitive to shorter wavelength radiation than Planck and will be studying the birth of stars and the evolution of galaxies.

        It, too, carries bolometer technology, but operates at a slightly warmer temperature - just 0.3 of a degree above absolute zero.

        Story from BBC NEWS:

        Published: 2009/07/03 17:31:54 GMT

        © BBC MMIX

        --- In quantummechanics2@yahoogroups.com, "Snhicks" <emperor_snhicks@...> wrote:
        > http://www.aip.org/pnu/2002/573.html
        > inside science research-physics news update
        > Number 573, January 16, 2002 by Phil Schewe, James Riordon, and Ben
        > Stein
        > Quantum Gravitational States
        > Quantum gravitational states have been observed for the first time.
        > An experiment with ultracold neutrons shows that their vertical
        > motion in Earth's gravitational field come in discrete sizes. Quantum
        > properties--such as the quantization of energies, wavelike dynamics
        > including interference, and an irreducible uncertainty in the
        > simultaneous measurement of position and momentum--usually emerge
        > only at the atomic level or under special circumstances (e.g., low
        > temperatures) wherein a particle is trapped in a potential well by a
        > controlling force. Observing such properties in phenomena governed by
        > the electromagnetic or the weak and strong nuclear forces is common
        > enough, but the strength of gravity, many orders of magnitude weaker
        > than the other forces, has not previously been strong enough to
        > enforce the kind of confinement needed to make quantum reality
        > manifest.
        > Such an effect has now been seen. Physicists at the Institute Laue-
        > Langevin reactor in Grenoble, France employ a beam of ultracold
        > neutrons. Moving at a pace of 8 m/sec (compared to 300 m/sec for an
        > oxygen molecule at room temperature), the neutrons are sent on a
        > gently parabolic trajectory through a baffle and onto a horizontal
        > plate. Because the neutrons bounce at such a grazing angle, the plate
        > is essentially a mirror for the neutrons, which are reflected back
        > upwards until gravity saps their ascent; then the neutrons start
        > falling again, eventually to be captured by a detector. In effect the
        > neutrons are caught in a vertical potential well: gravity pulls down,
        > while atoms in the surface of the mirror push up.
        > The researchers report seeing a minimum (quantum) energy of 1.4
        > picoelectron volts (1.4 x 10-12 eV), which corresponds to a vertical
        > velocity of 1.7 cm/sec. A comparison of this energy level to the
        > minimum energy for an electron trapped inside a hydrogen atom, -13.6
        > eV, demonstrates why this kind of detection has not been made before.
        > The experiment provides also preliminary evidence for higher
        > quantized motion states as well. In the horizontal direction there is
        > no confinement and therefore no quantum effect. [By the way, neutron-
        > interferometry experiments, in which neutron waves are split apart,
        > moved around separate paths, and then brought back together in order
        > to produce an interference pattern, have been influenced by gravity,
        > but these neutron waves were not quantum states owing to the
        > gravitational field. By contrast, the Laue-Langevin experiment is the
        > first to observe quantum states of matter (neutrons) in Earth's
        > gravitational field.]
        > The next step is to use a more intense beam and an enclosure mirrored
        > on all sides (the energy resolution improves the longer the neutrons
        > spend in the device). An energy resolution as sharp as 10-18 eV is
        > expected, which would allow one to test such basic propositions as
        > the equivalence principle, according to which the neutron's
        > gravitational mass (as measured by its free fall in gravity) is the
        > same as its inertial mass (as prescribed by Newton's second law,
        > F=ma, where F is a generic force and a the acceleration imparted).
        > (Nesvizhevsky et al., Nature, 17 Jan 2002.)
        > Looking at Extrasolar Planets By Direct Observation
        > Looking at extrasolar planets by direct observation will be possible
        > soon, says UC-Berkeley astronomer Ray Jayawardhana. Because a star is
        > so much brighter than any planet (viewed from outside our solar
        > system, Jupiter would be only one billionth as bright as the sun),
        > the presence of extrasolar worlds around distant stars has so far
        > been inferred only indirectly, by the slight distortion imparted to
        > the star's spectrum. But with new adaptive optics technology---which,
        > with computer-controlled flexing of secondary mirrored surfaces, can
        > partly undo the fuzzy distortions of incoming light introduced by
        > atmospheric air currents overhead-attached to the largest optical
        > telescopes, such as the 8.1-m-diameter Gemini North and the 10-m Keck
        > telescopes, the prospect of gaining the needed clarity for seeing
        > planets has improved greatly.
        > At last week's meeting of the American Astronomical Society in
        > Washington, DC, Jayawardhana reported an example of the new, sharper
        > viewing: a picture taken with Gemini showing not yet a planet exactly
        > but a planet in the making near the star MBM12, some 900 light years
        > away. This protoplanetary disk (see NOAO press release) is the first
        > such disk imaged for a four-star system and the first edge-on disk
        > discovered with the help of adaptive optics. Furthermore, this star
        > is still quite young and the disk itself only an estimated 2 million
        > years along on its planet-building mission.
        > It is young star systems like this that offer hope of seeing planets
        > directly since the star-to-planet brightness ratio might be only as
        > little as 100,000. With the higher angular resolution available (80
        > milli-arcseconds for the case of this disk, which lies at a distance
        > of only 150 AU from the star) from adaptive optics coupled with large
        > ground-based telescopes Jayawardhana believes planets, and not just
        > disks, can be spotted in the next few years. Indeed he referred to
        > some planetary candidates already glimpsed but not yet subjected to
        > the full battery of tests needed for planetary designation-such as
        > observing the planet candidate co-move with its star and recording a
        > spectrum consonant with planets (methane, water, etc.).
        > --- In quantummechanics2@yahoogroups.com, "Snhicks"
        > <emperor_snhicks@> wrote:
        > >
        > > Ultracold molecules pave way for quantum 'Super Molecule'
        > > July 3, 2003 - Achievement Could Improve Understanding of
        > > Superconductivity
        > >
        > > http://www.brightsurf.com/news/july_03/NIST_news_070303.php
        > > Ultracold molecules pave way for quantum 'Super Molecule'
        > > July 3, 2003 - Achievement Could Improve Understanding of
        > > Superconductivity
        > >
        > > A team of researchers at JILA, a joint institute of the Commerce
        > > Department's National Institute of Standards and Technology (NIST)
        > > and the University of Colorado at Boulder, has done the physics
        > > equivalent of efficiently turning yin into yang. They changed
        > > individual potassium atoms belonging to a class of particles called
        > > fermions into molecules that are part of a fundamentally different
        > > class of particles known as bosons. Though the transformation lasts
        > > only a millisecond, the implications may be long lasting.
        > >
        > > The work, reported in tomorrow's edition of the journal Nature, is
        > an
        > > important step toward creating a "super molecule," a blend of
        > > thousands of molecules acting in unison that would provide
        > physicists
        > > with an excellent tool for studying molecular quantum mechanics and
        > > superconductivity. Creation of a "super atom" (known as a Bose-
        > > Einstein condensate or BEC; see www.bec.nist.gov for more
        > > information) earned another research team at JILA the 2001 Nobel
        > > Prize in physics.
        > >
        > > In the Nature paper, NIST's Deborah Jin and colleagues describe
        > their
        > > experiments to produce these exotic molecules at temperatures of
        > only
        > > about 150 nanoKelvin above absolute zero. The technique involves
        > > manipulating a cloud of atoms within an ultra-high vacuum chamber
        > > with lasers and magnetic fields to coax the atoms to pair up into
        > > loosely joined molecules. Surprisingly, the researchers report, the
        > > number of molecules produced is very largeڷith about a
        > quarter
        > > million or 50 percent of the atoms within the original cloud
        > pairing
        > > up.
        > >
        > > "This work," Jin notes, "could help us understand the basic physics
        > > behind superconductivity and especially high-temperature
        > > superconductivity."
        > >
        > > Superconductivity is a property in which electrons (a fermion
        > > particle) move through a metal with no resistance. The experiments
        > > may lead to creation of fermion superfluids made from gases that
        > > would be much easier to study than solid superconductors.
        > >
        > > "Our experiments," Jin continues, "produced the lowest molecular
        > > binding energy that has been measured spectroscopically." In other
        > > words, the atom pairs forming each molecule are hanging on to one
        > > another by their proverbial fingertips. They also are spaced very
        > far
        > > apart by molecular standards. The researchers measured the amount
        > of
        > > energy required to hold the molecules together by breaking the
        > > molecular bond with a relatively low-energy radio wave. Most
        > > molecular bonds require higher-energy light waves to break them
        > > apart.
        > >
        > > The atoms, a form of potassium with one extra neutron (the isotope
        > of
        > > potassium with a molecular weight of 40 rather than the more common
        > > 39), are classified as fermions. Fermions are the particles most
        > > people are familiar with˜.e., protons, neutrons, electronsڡnd
        > they
        > > obey one basic rule. No fermion can be in exactly the same state at
        > > exactly the same time and place as another fermion. Hence, no two
        > > things made of ordinary matter can be in exactly the same place at
        > > exactly the same time.
        > >
        > > The molecules formed from these potassium atoms, however, are
        > bosons.
        > > Unlike fermions, bosons can be in exactly the same energy state in
        > > exactly the same time and space. Light waves or photons are the
        > most
        > > commonly known bosons, and laser light is an example of how bosons
        > > can behave in unison. Bose-Einstein condensates (BECs) are the
        > atomic
        > > equivalent of lasers. First produced in 1995 by JILA scientists
        > Eric
        > > Cornell and Carl Wieman, BECs are a fourth state of matter in which
        > a
        > > dense cloud of atoms acts like one huge super atom.
        > >
        > > Funded by NIST and the National Science Foundation, the current
        > work
        > > of Jin and her colleagues. Cindy A. Regal, Christopher Ticknor and
        > > John Bohn, builds on these earlier experiments.
        > >
        > > As a non-regulatory agency of the U.S. Department of Commerce's
        > > Technology Administration, NIST develops and promotes measurement,
        > > standards and technology to enhance productivity, facilitate trade
        > > and improve the quality of life.
        > >
        > > National Institute of Standards and Technology
        > >
        > >
        > >
        > > --- In quantummechanics2@yahoogroups.com, snhicks2000 wrote:
        > > >
        > > > from Scientific American issue December
        > > > 2001,<br>"THE NOBEL PRIZES FOR 2001<br>In October the Royal
        > > > Swedish Academy marked the centennial of the Nobel
        > > > Prizes. The laureates in each field received a portion of
        > > > 10 million Swedish kronor, or about
        > > > $957,000.<br>PHYSICS"<br><a
        > > href=http://www.sciam.com/news/101001/2.html
        > > target=new>http://www.sciam.com/news/101001/2.html</a><br>"In 1995
        > > Eric A. Cornell and Carl E. Wieman of the
        > > > University of Colorado at Boulder, and independently
        > > > Wolfgang Ketterle of the Massachussetts Institute of
        > > > Technology, produced one of the msot sought-after substances
        > > > in physics: the Bose-Einstein condensate.<br>Named
        > > > after the two men who postulated its existence, the BEC
        > > > is a new state of matter in which very slow moving
        > > > atoms condense into a "superatom" that moves and
        > > > behaves like one particle.<br>Working with rubidium and
        > > > sodium gases, the researchers slowed down individual
        > > > particles by cooling the gases to a tenth of a millionth of
        > > > a degree above absolute zero. <br>The BEC promises
        > > > to provide valuable insights into quantum-mechanical
        > > > processes and may one day be applied to lithography,
        > > > nanotechnology and ultraprecise measurements."
        > > >
        > >
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