Following a
Supernova explosion, gravitation gradually starts to shed its purely compressive
character and begins a long metamorphosis through an endless series of phase
transitions which, to be more precise, we would refer to as energy transformations
or transductions. The first transition,
in a great compressive thrust, consists in transducing the gravitational potential
of the collapsing star, as it bounces off its iron and neutron core, into a
compact shock front. As this wave travels through the star’s outer layers
it delivers a compressive force highly magnified by its compactness, forcing
together numbers of free nuclei of various masses, along with free protons and
neutrons. The wave travels on leaving behind an expanding gas cloud composed
not only of all the elements up to iron but also a range of newly synthesized
heavier elements and their isotopes, many of which contain a large excess of
neutrons. Some of these nuclei are as a result unstable since they contain more
protons and neutrons than their binding energies can control, and they immediately
start to decay by ejecting excess particles in a process, radioactivity, that
must continue until they finally reach a low energy, stably bound structural
configuration. The generation of radioactivity
is the second major transduction of gravitational energy. The supernova explosion
then causes these radioactive isotopes to act as vectors storing and transporting
excess gravitational energy
throughout the ISM.
During solar system formation, as molecular clouds condense under the effect
of gravitational contraction, heavier elements fall in toward the center of
gravity with the result that neutron-rich radioactive nuclei are strongly represented
in the inner planets as they form, which is why they have become an important
element of the Earth’s crust. There is clear evidence that short-lived nuclides
were originally present on Earth, with initial abundances in general many times
their present values. Similarly longer lived isotopes, for example 235U, are believed to have been 100 times
more abundant than at present. Another long lived isotope, Thorium, 232Th, is about four times more abundant than uranium in the Earth’s crust
and is in addition present in uranium ores. Following the decline of radioactive
isotopes since the formation of the Earth, concentrations of radiogenic nuclides,
the products of decay, have increased at rates depending on the different half-lives
of their precursors, considerably complicating the radioactive landscape. Subsequently,
geochemical, hydrothermal and other gravitationally driven geological fractionation
processes tended to concentrate radioactive nuclides in deep crustal placer
deposits. Along with the fact that radionuclides were considerably more abundant
in the Archaean Earth, these processes created compact centers of powerful radiogenic
decay pressure.
Radionuclides can undergo many possible modes of decay depending on the particular
characteristics of the species in question, however the three principal types
concerning us here are alpha, beta and gamma emission. A most important characteristic
of a-particles, Helium nuclei 4He2+, is that a given nuclide will emit them at certain
discrete energy levels exclusively. For example 238U emits alphas of 5.2 MeV only, while 235U emits alphas of 4.39 MeV and 4.56 MeV in fixed proportions. b-decay is considerably more complex, but the most significant result
is emission of electrons over a wide spectrum of energies with, however, a characteristic
maximum energy for each nuclide. Typical b-electron emission energies range from several keV to a few MeV. g-ray photons are also emitted at certain defined energy levels characteristic
of each nuclide, commonly in the multi-MeV range. The kinetic energy levels
of these emissions constitute a significant feature as surprisingly they lie
within the energy range of the universe approximately one second after the Big
Bang, during the era of nucleosynthesis. They also correspond to temperatures
between 109K and 1010K obtaining in the
core of a large star in which iron is being synthesized. Given the conditions
of energy, pressure and confinement described above, it is reasonable to conclude
that processes such as the triple alpha reaction and the CNO cycle operating
at temperatures between 107K and 108K, which we normally
associate with stellar core nucleosynthesis, could easily have occurred on Earth
although clearly not at rates occurring in stellar cores. These processes would have generated, in a
highly confined locale, all the biogenic elements, C, H, N, O, P, S along with
others including some transition metals, by de
novo nucleosynthesis, constituting
the third major transduction of gravitational energy.
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