Text Box: Says geochemist Douglas Hammond of the University of Southern California (USC) in Los Angeles: "Everybody always assumes radioactive decay to be totally independent of temperature, pressure, and chemical form. It seems there are some exceptions." ...
When Fritz Bosch and his colleagues at the Gesellschaft für Schwerionenforschung in Darmstadt, Germany, stripped away all the electrons from rhenium nuclei, something that might happen in a star's harsh interior, its half-life plummeted from 42 billion years to 33 years [that's from 42x109 to a mere 33]. But, until now, researchers have detected only tiny variations (or none at all) in the decay rate of beryllium and other atoms under Earth-like conditions...
Tweaking the Clock of Radioactive Decay, Richard A. Kerr, Science 286, 882-883 (1999)
Text Box: "The exception tests the rule." Or, put it another way. "The exception proves that the rule is wrong." That is the principle of science. If there is an exception to any rule, and if it can be proved by observation, that rule is wrong.
Richard Feynman (Nobel laureate 1965), The Meaning of It All, Addison-Wesley (1998); p 16
Text Box: Ultracold neutrons. ...The ultracold neutrons can be stored in "neutron bottles,"… One is simply a vacuum vessel with a door that can be closed after a batch of neutrons has entered. Populations of about 100 neutrons have been retained in such vessels, but the storage times are considerably shorter than the half-life of the neutrons against their natural radioactive decay, and the nature of the extra loss mechanism is not yet fully understood. ... 
Neutron, Arthur H. Snell, McGraw-Hill Encyclopedia of Physics, 1992; p 826
Text Box: Low ambient pressures promote nuclear fission just as much as high pressures aid fusion (see also book section 1.21). 
In the galactic halo, pressure and density drop with increasing radius. The drop in pressure steps up radioactivity, 
but the drop in material density tends to nullify any increase in the decay intensity. 
Consequently, the vast outer region of a galaxy tends to be more of an energetic, dense, and homogeneous plasma medium than what we have come to believe this "empty" space to be. 
At these great distances, of several orders of light years from the galactic center, the gravitational effect 
(that is, from CMB shielding) is small in relation to the net inward push (back pressure) of the decay radiation.
The latter being also a pro-gravitational influence, stable orbital speed, too, becomes correspondingly large for the region. 

Furthermore, orbital bodies of the galaxy are created by the "lawn-sprinkler effect": 
The core spews out stellar matter (periodically, as in the nova) while at the same time spinning about its axis*.
As such, the gases and stars streaming through an essentially homogeneous outer medium will have the same (terminal) speed irrespective of individual masses – just as much as electrons and nuclei of vastly differing masses have the same speed in the solar wind near Earth space (see book section 4.03 where this is also discussed quantitatively).
En route from the birthing ground to the outer regions, of course, the bodies would be decelerating (toward terminal velocity) from the high (escape) velocity attained at ejection. 
The galaxy cluster and the galaxy supercluster evolve in very similar ways but from much larger nuclear centers (see The Cosmos). 
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*At such epochs of mass ejections, the galactic nucleus would tend to appear shaped more like a bar than a sphere, that is, to distant observers. The galaxies that are active in this way, of course, would be the spiral galaxies. Statistically, therefore, half of them will be more in the phase of ejecting matter (their nuclei thus appearing to be elongated) while the other half will be more in a period of relative quiescence (with nuclei more spherical). All these are indeed observational facts today. Even our own Galaxy is presently in this “bar” phase of activity; see also book section 1.11.
Text Box: Astronomers have known for years that a powerful energy source at the core of the Milky Way is sending gamma-rays out through the entire galaxy, but now they're puzzling over an entirely new phenomenon – a halo of gamma radiation that appears to embrace the galaxy's perimeter. The discovery of this halo, thousands of light-years in diameter, was announced today at a meeting of the American Astronomical Society in Estes Park, Colorado. Astrophysicists don't know what the source is yet, but they have no shortage of theories. ...
The first gamma-ray map of the sky, generated 2 years ago by a space telescope called the Compton Gamma-Ray Observatory, was dominated by gamma-rays coming from the center of the Milky Way, where intense star formation occurs, and by a few bright sources outside our galaxy. 
Dave Dixon, a physicist at the University of California, Riverside, made a remarkable find when he subtracted from this image the core glow of the Milky Way and other known gamma-ray sources. The remaining gamma-rays – about 10% of those observed – emerged from a huge, diffuse cloud surrounding the galaxy, from a direction where no high-energy source is known to exist. ...
How can gamma-rays be produced in what looks like empty space? ...
"We all sat around at dinner last night and were racking our brains on how to explain it," says Neil Gehrels of the Goddard Space Flight Center in Greenbelt, Maryland, the project scientist for the Compton mission. "Once we get away from the galaxy, we don't know any sources" violent enough to produce the halo. ... 
Gamma-Ray Halo Intrigues Astronomers, ScienceNow, 4 Nov 1997
      Go to Part 3 of 3
THE UNIFICATION OF PHYSICS ILLUSTRATIONS
A Synopsis The Cosmos The Spin
ADDENDA The Cosmological Redshift The Neutrino
Two-Slit Tests The Galaxy Nuclear Reactions
NASA Tests Gravity The Sun
KamLAND Test Anti-Gravity The Pulsar
UCLA Test Relativity Superconductivity
Q and A Mass-Energy Fusion Energy
 Eugene Sittampalam
 27 May 2007