Other topics:
Emergence
Strings
Gravity and Cosmology
Condensed Matter Physics
Nanoscience
Quantum Mechanics
Elementary Particles
Quantum Fluids
STRINGS
The 2 great theories of the 20th century, which revolutionised science, are Einstein's theory of gravity and spacetime ('general relativity') and quantum mechanics. Unfortunately it is very hard to see how one can reconcile these together into one final 'Theory of Everything'. The attempt to do this is what string theory is all about. Currently string theory predicts that the fundamental 'stuff' of Nature is a set of structures, called strings, which obey the laws of quantum mechanics. However these only appear at length scales of 10-35 metres (ie., 1020 times smaller than the atomic nucleus). At this fantastically small length scale, the 4-dimensional spacetime we know of 'peels back' to reveal filamentary 11-dimensional structures, which appear and disappear, and whose vibrational patterns are supposed to give the
elementary particles that
we now think of as the building blocks of matter. These
'strings' also yield Einstein's gravity. In recent years
string thoery has evolved very rapidly, under the
influence of ideas like the 'holographic principle' (due
to 't Hooft
and
Susskind).
The principal problem
facing string theory is that it is almost impossible to
confirm or deny any of its ideas- this would require
observing processes at energies far higher than
anything currently active in the universe. Some current
versions of string theory may however imply a '5th
force', which might be observable in experiments.
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