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