clifford_a-_pickover_surfing_through_hyperspacebookfi-org

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(subatomic particles), WIMPs (weakly interacting massive particles), MACHOs
(massive compact halo objects), black holes, and vast, filamentary networks of
warm, ionized gases that are difficult to detect with present satellites.
• Cosmic strings and cosmic textures are hypothetical entities that distort the spacetime
fabric.
(Perhaps some of the large, extragalactic structures are artifacts of inexact observations
and analysis. Further research is required to be certain.)
What are the biggest questions for today's scientists? Perhaps, "Are there higher spatial
dimensions?" or "Which laws of physics are fundamental and which are accidents of
the evolution of this particular universe?" or "Does intelligent, technologically advanced
life exist outside our Solar System?" and "What is the nature of consciousness?"
How many of these questions will we ever answer?
7. M-theory, like string theory, relies heavily on the idea of supersymmetry in which
each known particle having integer spin has a counterpart with the same mass but halfinteger
spin. Supersymmetry predicts "supergravity" in which a graviton (with spin 2)
transmits gravitational interactions and has a partner gravitino with spin 3/2. Conventional
gravity does not place constraints on the possible dimensions of spacetime, but
with supergravity there is an upper limit of eleven dimensions of spacetime. In 1984, 11-
D supergravity theories were disbanded in favor of superstring theory in ten dimensions.
M-theory in eleven dimensions gives rise to the five competing string theories in ten
dimensions (two heterotic theories, Type I, Type IIA, and Type IIB). When the extra dimension
curls into a circle, M-theory yields the Type IIA superstring. On the other hand, if the
extra dimension shrinks to a line segment, M-theory yields one of the heterotic strings.
New theories deal with arcane concepts difficult for mere mortals to grasp. For
example, the strength with which objects interact (their charges) is related to the size of
invisible dimensions; what is charge in one universe may be size in another; and certain
membranes may be interpreted as black holes (or "black-branes") from which nothing,
not even light, can escape. The mass of a black-brane can vanish as the hole it wraps
around shrinks, allowing one spacetime with a certain number of internal holes
(resembling a piece of cheese) to change to another with a different number of holes,
violating the laws of classical topology.
Edward Witten and Petr Horava have recently shown how to shrink the extra
dimension of M-theory into a segment of a line. The resulting structure has two 10-D
universes (each at an end of the line) connected by a spacetime of eleven dimensions.
Particles (and strings) exist only in the parallel universes at the ends, which can communicate
with each other only via gravity. For additional reading on these mindnumbing
concepts, see Michael Duff's paper cited in Further Readings.
Note that string theory says little about the space in which strings move and vibrate.
A relatively new mathematical model known as loop quantum gravity represents an
alternate approach in which the rules of quantum mechanics are applied directly to
Einstein's description of space and time. In this model, space itself comes packaged in