Biuletyn PTA nr 17

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               |         Biuletyn PTA nr 17         |   
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  Biuletyn informacyjny Zarzadu Glownego Polskiego Towarzystwa Astro-   
  nomicznego (Adres kontaktowy: M. Ostrowski, ,  
  a w bardzo pilnych sprawach: )   
Spis tresci:   
   I.   Europejski program ASTROVIRTEL 

   II.  Nowosci naukowe 
        - LIGHT AT 1 mph 
        - 1997/98 PHYSICS DEMOGRAPHICS 
I.   Europejski program ASTROVIRTEL 
On behalf of ESA and ESO, we are glad to be able to announce the opening 
of the ASTROVIRTEL Programme. 
ASTROVIRTEL is an initiative financed by the European Commission under 
the scheme "Enhanced Access to Large Infrastructures" of the 5th 
Framework Plan and it is operated by the ST-ECF and ESO/DMD. 
The aim of ASTROVIRTEL is to give the opportunity to selected groups of 
European scientists (from EC Member and Associated States [for a list of 
these states, see]) to 
access and use the ESO/ST-ECF Archive (which currently contains data 
obtained with the ESA/NASA HST, with the ESO NTT, VLT and with the Wide 
Field Imager on the ESO/MPI 2.2m Telescope) as if it would be a 
"virtual" Telescope. 
A description of the ASTROVIRTEL Programme, together with the details of 
the first Call for Proposals, can be found at . 
Please note that the deadline for the first Call is June 15th, 2000. 
Do not hesitate to contact us if you need further information. The 
ASTROVIRTEL email address is 
Piero Benvenuti 
Head / ST-ECF 
Peter Quinn 
Head / DMD 
From: Piero Benvenuti ( 
II.  Nowosci naukowe 
LIGHT AT 1 mph.  A year ago Lene Verstergaard Hau used a Bose 
Einstein condensate (BEC) as a special nonlinear optical medium for 
slowing light from 3 x 10^8 m/sec to a mere 17 m/sec (38 mph; Update 
415).  This comes about when an incoming light pulse enters the BEC and 
experiences an extremely abrupt change in index of refraction (and as for 
absorption of the light, this is prevented by applying two laser beams 
which induce a transparency at the frequency of the incoming light).  In a 
talk presented at this week's meeting of the American Association for the 
Advancement of Science (AAAS) in Washington, DC, Hau said that she 
and her Harvard colleagues had slowed the light further, to a speed of 1 
mph.  She said that if  the velocity could be slowed still more, to a value 
of 1 cm/sec, then this would be comparable to the speed of sound in the 
condensate and it might be possible to get atoms to surf on the front of the 
light pulse.  Hau believes that this approach to slowing light, if it can be 
simplified, would lead to highly sensitive light switches and to low-power 
nonlinear optics (right now high-power laser light is required to produce 
nonlinear effects). 
CANDIDATE DARK MATTER PARTICLES, specifically thought to be 
examples of "weakly interacting massive particles" (WIMPs), have been 
indirectly detected by a group operating in the Gran Sasso National Lab 
(INFN) in Italy, according to a paper to be delivered by Pierluigi Belli of 
the University of Rome (DAMA collaboration) at a dark matter detection 
meeting in Marina del Rey, California this week (a meeting sponsored by 
UCLA: information from  Dark matter is a 
hypothetical non-luminous substance thought to be lurking in and around 
galaxies, influencing the way the galaxies rotate and interact.  The dark 
matter might consist in part of baryons (particles such as the protons 
found in common atoms) or more novel forms such as WIMPs. Because 
of the way the Earth orbits the sun and the way our solar system moves 
through the galaxy (buffeting the presumed dark matter halo as it goes) 
there is reason to think that the flux of WIMP wind we encounter (and the 
rate at which WIMPs feebly interact in terrestrial detectors) would be 
higher in June than in December.  The DAMA experiment reports having 
discovered just such an seasonal effect in the frequency of events in which 
a presumed incoming WIMP (with masses about 50 times that of the 
proton) strikes a shielded sodium-iodine scintillation material, causing 
tiny flashes of light deep within the detector (INFN preprint AE-00/01;  Dark matter interactions in detectors are expected to 
be rare and analysis difficult, so the DAMA interpretation will be subject 
to great scrutiny at the California meeting, where other groups searching 
for WIMPs will be reporting as well. 
DARK MATTER UPDATE.  At the dark matter detection meeting in 
Marina del Rey, California last week (Update 473) a group form Gran 
Sasso, Italy reported detecting evidence for dark matter particles.  The 
Cryogenic Dark Matter Search collaboration (10 US institutions), using a 
different detection scheme, reported finding no evidence for such particles, 
and asserted that their results were incompatible with the Gran Sasso 
finding. (Stanford press release, 2/24. see preprint at 
STRANGE HALO ORBITS EXPECTED AT SATURN.  Consider particles in orbit 
above a planet.  If the particles are uncharged or have a very low 
charge-to-mass ratio, they will follow a conventional ("Keplerian") 
trajectory centered about the axis of the planet at the equator 
(Saturn's rings are an example of such particles).  If, however, the 
particles are highly charged, their motions are dominated by an 
electromagnetic interaction with the planet's magnetic dipole (Earth's 
van Allen belts are an example).  If the charge is somewhere in between 
these two cases, and gravity and electromagnetic forces are comparable, 
then strange orbits are possible.  Scientists at the University of 
Colorado (Mihaly Horanyi and Jim Howard, 303-492-6903) and Loughborough 
University (Holger Dullin) in the UK estimate that if conditions are 
just right some particles could race around a planet in orbits (stable 
for as long as 10 years) that never cross the planet's equatorial plane 
(see figure at  The dust analyzer on the 
Cassini craft now gliding toward Saturn might be able to detect 
particles in these novel orbits.  (Howard et al., upcoming article in 
Physical Review Letters; Select Article.) 
Physical Society Meeting in Long Beach, Jens H. Gundlach of the 
University of Washington (paper P11.3) reported a long-awaited higher 
precision measurement of the gravitational constant, usually denoted by 
the letter G. Although G has been of fundamental importance to physics 
and astronomy ever since it was introduced by Isaac Newton in the 
seventeenth century (the gravitational force between two objects equals 
G times the masses of the two objects and divided by their distance 
apart squared), it has been relatively hard to measure, owing to the 
weakness of gravity.  Now a group at the University of Washington has 
reduced the uncertainty in the value of G by almost a factor of ten. 
Their preliminary value is G=6.67390 x 10^-11 m^3/kg/s^2 with an 
uncertainty of 0.0014%. Combining this new value of G with measurements 
made with the Lageos satellite (which uses laser ranging to keep track 
of its orbital position to within a millimeter) permits the calculation 
of a brand new, highest precision mass for the earth: 5.97223 (+/- 
.00008) x 10^24 kg. Similarly the new mass of the sun becomes 1.98843 
(+/- .00003) x 10^30 kg. Gundlach's (206-543-4080, setup is not unlike Cavendish's venerable 
torsion balance of two hundred years ago: a hanging pendulum is obliged 
to twist under the influence of some nearby test weights.  But in the 
Washington experiment measurement uncertainties are greatly reduced by 
using a feedback mechanism to move the test weights, keeping pendulum 
twisting to a minimum.  (See Gundlach's written summary at; figures at 
MAGNETIC FIELDS ARE EVERYWHERE.  The history of the universe is usually 
described in terms of the distribution of matter: first primordial 
knots, then clouds, galaxies, stars, and clusters.  A parallel, and 
perhaps not unrelated, saga can be written for magnetic fields. 
Basically, Philipp Kronberg (416-978-4971) of the University of Toronto 
finds magnetic fields every place he has looked in the cosmos: within 
the Milky Way (where the fields are typically about 5 microgauss), in 
intergalactic areas within galaxy clusters (1-2 microgauss for the Coma 
cluster, 350 million light years away), and even outside clusters.  The 
latter observations are brand new and were reported by Kronberg at the 
APS meeting ( 
Detecting weak magnetic fields outside clusters was difficult and 
required the use of new low-frequency receivers mounted on the Very 
Large Array (VLA) radio telescope.  The radio range employed, around 75 
MHZ, is normally problematic owing to scattering in the Earth's 
ionosphere, but new image processing techniques have allowed a sharp VLA 
"deep field" image to be formed.  From the intensity of the radio glow, 
Kronberg deduced a magnetic field of about 10^-8 to 10^-7 gauss for a 
distant region outside any galaxy cluster, a place (near the "Great 
Wall") where fields had not been mapped before.  Where did such fields 
come from?  Kronberg suggests that huge shock waves, formed where two 
large streams of weakly magnetized gas come together, could amplify 
existing fields to much higher levels, as well as playing a part in the 
acceleration of cosmic rays.  Angela Olinto (paper B7.1) of the 
University of Chicago (773-702-8206) discussed the idea of primordial 
magnetism, fields that might have existed at or shortly after the time 
of the big bang.  Such fields, she speculated, might have come about 
through the development of some asymmetry (just as matter came to 
predominate over antimatter) in the infant universe.  Early magnetism 
might  then have influenced subsequent galaxy formation or even the 
distribution of matter now seen imprinted in the cosmic microwave 
background (CMB).  She said that the surprising absence of subsidiary 
peaks in the CMB spectrum (see Update 481) might be attributable to 
magnetic effects.  This hypothesis could be addressed, Olinto said, by 
the Planck satellite (launch date several years from now; see Update 
342), dedicated to mapping the CMB with unprecedented precision. 
time.  Gravity has of course long been studied over planetary distances 
but is more difficult to gauge at the terrestrial scale, where intrusive 
electric and magnetic fields, many orders of magnitude stronger than 
gravity fields, can be overwhelming.  Nevertheless, Eric Adelberger and 
his colleagues at the University of Washington have managed to measure 
the force of gravity over distances as small as 150 microns using a 
disk-shaped pendulum carefully suspended above another disk, with a 
copper membrane stretched between them to help isolate electrical 
forces. (This experiment should not be confused with another University 
of Washington effort in which the gravitational constant is measured 
with higher precision see Update 482).   Adelberger (206-543- 4294, presented one of several talks at this 
week's APS meeting in Long Beach, California devoted to short-range 
gravity, a subject which has suddenly attracted much theoretical and 
experimental interest owing to a relatively new model which supposes the 
existence of extra spatial dimensions in which gravity, but not other 
forces, might be operating.  According to Nima Arkani-Hamed of LBL 
(, 510-486- 4665) this is why gravity is so weak: it 
dilutes itself in the extra dimensions. In other words, ordinary 
particles are tethered to our conventional spacetime, or "brane," while 
gravitons are free to roam into otherwise unseeable dimensions.  One 
implication of the model, testable with tabletop experiments such as 
Adelberger's, is that the gravitational force might depart from Newton's 
inverse square law (gravity inversely proportional to the square of the 
distance between two objects) at close range. Adelberger did not observe 
such a departure at distances down to tenths of a millimeter and will 
continue to explore even shorter distances.  For a list of tabletop 
experiments underway, see Another interesting 
implication of  the model introduced by Arkani-Hamed (and others; see 
preprint hep-th 9803315) two years ago is that the unification of the 
four known forces would not necessarily occur at energies as high as 
10^19 GeV but possibly at energies as low as 10^4 GeV, an energy scale 
within reach of the Large Hadron Collider under construction at CERN. 
Extra dimensions could, for example, manifest themselves in proton- 
proton smashups as an apparent disappearance of energy, implying that 
some of the collision energy had been converted into gravitons (the 
particle form of gravity) which then disappear into the extra 
dimensions.  The gravitons produced in this way might come back into our 
conventional world of 3 spatial dimensions and decay into two photons. 
Physicists have already looked for this kind of event. Gregory Landsberg 
of Brown University (401-863-1464; reported 
that at the D0 experiment at Fermilab some energetic two-photon events 
have been observed (including one in which the energy of the photons 
added up to 574 GeV, representing the highest composite mass ever seen 
in the D0 experiment) but not often enough to constitute evidence for 
extra dimensions.  In fact this shortage of events has been translated 
into a lower limit of 1300 GeV for the energy at which a prospective 
unification of the forces could take place. 
1997/98 PHYSICS DEMOGRAPHICS for US institutions from a 
recent AIP report:  1323 physics PhDs were granted, a 4% drop 
from the previous year.  Of these 13% were to women and 46% to 
foreign citizens.  Among first-year physics graduate students, 
foreign citizens now exceed their US counterparts.  Physics PhDs 
were awarded to a total of 9 African-Americans and 9 Hispanic- 
Americans during the academic year.  Over the three year period 
1996-1998 the leading institutions for African-American physics 
bachelors were Xavier U (LA), Southern U & A&M Coll (LA), and 
Lincoln U (PA).  In astronomy 116 PhDs were granted: 19% went 
to women and 30% to foreign citizens.  (Enrollment and Degrees 
Report, AIP Education and Employment Statistics Div;