Venkat Mangudi wrote: [ on 11:35 PM 7/6/2007 ]
This is an interesting piece doing the rounds on http://del.icio.us
http://www.seedmagazine.com/news/2007/07/a_cyclic_universe.php
After reading the above, go here:
http://space.newscientist.com/channel/astronomy/cosmology/dn9987-top-10-weirdest-cosmology-theories-.html
Top 10: Weirdest cosmology theories
* 12:14 04 September 2006
* NewScientist.com news service
* Stephen Battersby
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1. Clashing branes
Could our universe be a membrane floating in
higher dimensional space, repeatedly smashing
into a neighbouring universe? According to an
offshoot of string theory called braneworld,
there are large extra dimensions of space, and
while gravity can reach out into them, we are
confined to our own "brane" universe with only
three dimensions. Neil Turok of Cambridge
University in the UK and Paul Steinhardt of
Princeton University in New Jersey, US, have
worked out how the big bang could have been
sparked when our universe clashed violently with
another. These clashes repeat, producing a new
big bang every now and then - so if the cyclic
universe model is right, the cosmos could be immortal.
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2. Evolving universes
When matter is compressed to extreme densities at
the centre of a black hole, it might bounce back
and create a new baby universe. The laws of
physics in the offspring might differ slightly,
and at random, from the parent - so universes
might evolve, suggests Lee Smolin of the
Perimeter Institute in Waterloo, Canada.
Universes that make a lot of black holes have a
lot of children, so eventually they come to
dominate the population of the multiverse. If we
live in a typical universe, then it ought to have
physical laws and constants that optimise the
production of black holes. It is not yet known
whether our universe fits the bill.
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3. Superfluid space-time
One of the most outlandish new theories of
cosmology is that space-time is actually a
superfluid substance, flowing with zero friction.
Then if the universe is rotating, superfluid
spacetime would be scattered with vortices,
according to physicists Pawel Mazur of the
University of South Carolina and George Chapline
at Lawrence Livermore lab in California and
those vortices might have seeded structures such
as galaxies. Mazur suggests that our universe
might have been born in a collapsing star, where
the combination of stellar matter and superfluid
space could spawn dark energy, the repulsive
force that is accelerating the expansion of the universe.
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4. Goldilocks universe
Why does the universe have properties that are
"just right" to permit the emergence of life?
Tinker with a few physical constants and we would
end up with no stars, or no matter, or a universe
that lasts only for the blink of an eye. One
answer is the anthropic principle: the universe
we see has to be hospitable, or we would not be
here to observe it. Recently the idea has gained
some strength, because the theory of inflation
suggests that there may be an infinity of
universes out there, and string theory hints that
they might have an almost infinite range of
different properties and physical laws. But many
cosmologists dismiss the anthropic principle as
being non-science, because it makes no testable predictions.
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5. Gravity reaches out
Dark matter might not really be "stuff" it
could just be a misleading name for the odd
behaviour of gravity. The theory called MOND
(modified Newtonian dynamics), suggests that
gravity does not fade away as quickly as current
theories predict. This stronger gravity can fill
the role of dark matter, holding together
galaxies and clusters that would otherwise fly
apart. A new formulation of MOND, consistent with
relativity, has rekindled interest in the idea,
although it may not fit the pattern of spots in
the cosmic microwave background.
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6. Cosmic ghost
Three mysteries of modern cosmology could be
wrapped up in one ghostly presence. After making
an adjustment to Einstein's general theory of
relativity, a team of physicists found a strange
substance popping out of their new theory, the
"ghost condensate". It can produce repulsive
gravity to drive cosmic inflation in the big
bang, while later on it could generate the more
sedate acceleration that is ascribed to dark
energy. Moreover, if this slippery substance
clumps together, it could form dark matter.
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7. It's a small universe
The pattern of spots in the cosmic microwave
background has a suspicious deficiency: there are
surprisingly few big spots. One possible
explanation is that the universe is small - so
small that, back when the microwave background
was being produced, it just could not hold those
big blobs. If so, space would have to wrap around
on itself somehow. Possibly the oddest suggestion
is that the universe is funnel-shaped, with one
narrow end and one flared end like the bell of a
trumpet. The bent-back curvature of space in this
model would also stretch out any smaller
microwave spots from round blobs into the little
ellipses that are indeed observed.
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8. Fast light
Why do opposite sides of the universe look the
same? It's a puzzle because the extremes of
today's visible universe should never have been
in touch. Even back in the early moments of the
big bang, when these areas were much closer
together, there wasn't enough time for light - or
anything else - to travel from one to another.
There was no time for temperature and density to
get evened out; and yet they are even. One
solution: light used to move much faster. But to
make that work could mean a radical overhaul of
Einstein's theory of relativity.
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9. Sterile neutrinos
Dark matter might be made of the most elusive
particles ever imagined - sterile neutrinos. They
are hypothetical heavier cousins of ordinary
neutrinos and would interact with other matter
only through the force of gravity - making them
essentially impossible to detect. But they might
have the right properties to be "warm" dark
matter, buzzing about at speeds of a few
kilometres per second, forming the largish dark
matter clumps mapped by recent observations.
Sterile neutrinos could also help stars and black
holes to form in the early universe, and give the
kicks that send neutron stars speeding around our galaxy.
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10. In the Matrix
Maybe our universe isn't real. Yale Philosopher
Nick Bostrum has claimed that we are probably
living inside a computer simulation. Assuming it
ever becomes possible to simulate consciousness,
then presumably future civilisations would try
it, probably many times over. Most perceived
universes would be simulated ones - so chances
are we are in one of them. In that case, perhaps
all those cosmological oddities such as dark
matter and dark energy are simply patches, stuck
on to cover up early inconsistencies in our simulation.
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((Udhay Shankar N)) ((udhay @ pobox.com)) ((www.digeratus.com))
