http://www.scienceweek.com/search/reports1/quavoco.htm
COSMOLOGY: EXPECTATIONS IN THE NEXT CENTURY OF RESEARCH
Cosmology is one of the grand sciences, a domain of research
whose results have enormous intellectual consequences, at least
for people who care about what they are and where they are.
Martin Rees (Cambridge University, UK) presents an essay on the
near-future research expectations of cosmologists, the author
making the following points:
1) Astronomers still do not know what the Universe is made
of. Observable radiation-emitting objects -- such as stars,
*quasars, and galaxies -- apparently constitute only a small
fraction of the matter in the Universe. The vast bulk of matter
is dark and unaccounted for, and most cosmologists believe this
dark matter is composed of weakly interacting particles left over
from the *Big Bang. But dark matter could be something more
exotic. "Whatever the case, it is clear that galaxies, stars and
planets are a mere afterthought in a Cosmos dominated by quite
different stuff." The author suggests that intensive searches for
dark matter, mainly via sensitive underground experiments
designed to detect elusive subatomic particles, will continue in
the coming decade, and that within the next decade both the
amount and nature of dark matter will be clarified.
2) The author suggests that research in the near-future is
also likely to focus on the evolution of the large-scale
structure of the Universe. The current view is that ever since
the Big Bang, gravity has been amplifying inhomogeneities,
building up structures and enhancing temperature contrasts -- "a
prerequisite for the emergence of the complexity that lies around
us now and of which we're a part." The author suggests that
astronomers are now learning more about the 10 billion year
process of Cosmic evolution by creating virtual universes on
computers, and that in the coming years researchers will be able
to simulate the history of the Universe with ever improving
realism and then compare the results with astronomical
observations.
3) The author suggests that the great mystery for
cosmologists is the series of events that occurred less than 1
millisecond after the Big Bang, when the Universe was
extraordinarily small, hot, and dense. "The laws of physics with
which we are familiar offer little firm guidance for explaining
what happened during this critical period." To solve this
problem, it will necessary to improve and refine current
observations in order to understand the characteristics of the
Universe when it was only one second old: its expansion rate, the
size of its density fluctuations, and its proportions of ordinary
atoms, dark matter, and radiation.
4) The author suggests the following Cosmic timeline for the
evolution of the Universe from the Big Bang to the present:
... ... a) 10^(-43) seconds after the Big Bang: the *Quantum
Gravity Era.
... ... b) 10^(-36) seconds after the Big Bang: Probable *Era of
Inflation.
... ... c) 10^(-5) seconds after the Big Bang: Formation of
protons and neutrons from *quarks.
... ... d) 3 minutes after the Big Bang: Synthesis of atomic
nuclei.
... ... e) 300,000 years after the Big Bang: First atoms form.
... ... f) 1 billion years after the Big Bang: Appearance of
first stars, galaxies, and quasars.
... ... g) 10 to 15 billion years after the Big Bang: Appearance
of modern galaxies.
5) The author concludes: "How did a hot amorphous fireball
evolve, over 10 to 15 billion years, into our complex Cosmos of
galaxies, stars, and planets? How did atoms assemble -- here on
Earth and perhaps on other worlds -- into living beings intricate
enough to ponder their own origins? These questions are a
challenge for the new millennium. Answering them may well be an
unending quest."
-----------
Martin Rees: Exploring our Universe and others.
(Scientific American December 1999)
QY: Martin Rees, Cambridge University, UK.
-----------
Text Notes:
... ... *quasars: (quasi-stellar objects). Extremely luminous
sources radiating energy over the entire spectrum from x-rays to
radio waves, and which are apparently the oldest and most distant
objects in the universe. They are believed to involve massive
black holes.
... ... *Big Bang: The Big Bang theory is the general
cosmological model that proposes that all matter and radiation in
the universe originated in an explosion at a finite time in the
past.
... ... *Quantum Gravity Era: Quantum field theory is the
mathematical fusion of quantum mechanics with special relativity
theory, and the term "quantum gravity" refers to the fusion of
quantum mechanics with general relativity theory. The essential
basis for these fusions is the so-called "equivalence principle",
which identifies the mass involved in the gravitational force
equation with the inertial mass in the equation that relates any
force to the product of inertial mass and acceleration. The
"quantum gravity era" is the time-frame during which both quantum
effects and gravity determined the behavior of particles.
... ... *Era of Inflation: The inflationary model, first
proposed by Alan Guth in 1980, proposes that quantum
fluctuations in the time period 10^(-35) to 10^(-32) seconds
after time zero were quickly amplified into large density
variations during the "inflationary" 10^(50) expansion of the
universe in that time frame.
... ... *quarks: A quark is a hypothetical fundamental particle,
having charges whose magnitudes are one-third or two-thirds of
the electron charge, and from which the elementary particles may
in theory be constructed.
-------------------
Summary & Notes by SCIENCE-WEEK [http://scienceweek.com] 28Jan00
[For more information:
http://scienceweek.com/swfr.htm]