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Csientific Theories to Meditate About

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    Top 10: Weirdest cosmology theories 09 August 2006 NewScientist.com news service Stephen Battersby 1. Clashing branes Could our universe be a membrane floating
    Message 1 of 1 , Sep 2, 2006
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      Top 10: Weirdest cosmology theories
      09 August 2006
      NewScientist.com news service
      Stephen Battersby

      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.

      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.

      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.

      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.

      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.

      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.

      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.

      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.

      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.

      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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