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Theory of relativity (view source)
Revision as of 16:55, November 25, 2009
, 16:55, November 25, 2009no edit summary
== Special Relativity ==
== Special Relativity ==
Lorentz and Poincare developed Special Relativity as way of understanding how Maxwell's equations for electromagnetism could be valid in different frames of reference. Einstein famously published an explanation of Poincare's theory in terms of two assumptions (postulates):
=== Physical Observations Predicating Special Relativity ===
Lorentz and Poincare developed Special Relativity as way of understanding how Maxwell's equations for electromagnetism could be valid in different frames of reference. Einstein famously published an explanation of Poincare's theory based on two physical observations:
# ''The [[speed of light]] is constant for all (inertial) observers, regardless of their velocities relative to each other.''
# ''The [[speed of light]] is constant for all (inertial) observers, regardless of their velocities relative to each other.''
This fact was first discovered by Michelson and Morley in an experiment they conducted to determine change in the relative velocity of the speed of light as the Earth changed reference frames in it's orbit about the sun. In the experiment, the speed of light was observed to be the same regardless of the relative velocity of the Earth in relation to the light.
# ''The laws of physics are identical in all inertial reference frames.''
# ''The laws of physics are identical in all inertial reference frames.''
This premise is based on physical observations made of Newtonian mechanics that the laws of physics are invariant under transformation between inertial reference frames.
In layman's terms, these two assumptions can be restated as:
In layman's terms, these two assumptions can be restated as:
#there is no [[action at a distance]] (because that would make observations dependent on the frame of reference)
#there is no [[action at a distance]] (because that would make observations dependent on the frame of reference)
#space and time are completely symmetric throughout the universe (because otherwise frames of reference would not be interchangeable)
#space and time are completely symmetric throughout the universe (because otherwise frames of reference would not be interchangeable)
=== Critical Views on Special Relativity ===
When the assumptions are stated clearly as above, the weaknesses in the theory are more apparent. There ''is'' action at a distance in [[quantum entanglement]] and apparently also in gravity, as no gravitons can be found. However, no information has yet been transmitted via quantum entanglement, so while non-locality violates the spirit of relativity it is consistent with it if relativity is limited to the transmission of information. [[Quantum field theory]], an attempt to partially reconcile [[quantum mechanics]] with relativity, is incomplete at best. As to the second assumption, it is contrary to the [[arrow of time]], which illustrates the lack of symmetry in time. Logical defects include the incoherence of relativistic mass (see discussion below) and the lack of relativistic constraints near the beginning the universe (see above).
When the assumptions are stated clearly as above, the weaknesses in the theory are more apparent. There ''is'' action at a distance in [[quantum entanglement]] and apparently also in gravity, as no gravitons can be found. However, no information has yet been transmitted via quantum entanglement, so while non-locality violates the spirit of relativity it is consistent with it if relativity is limited to the transmission of information. [[Quantum field theory]], an attempt to partially reconcile [[quantum mechanics]] with relativity, is incomplete at best. As to the second assumption, it is contrary to the [[arrow of time]], which illustrates the lack of symmetry in time. Logical defects include the incoherence of relativistic mass (see discussion below) and the lack of relativistic constraints near the beginning the universe (see above).