Changes

'''Relativity''' is a mathematical system built on untestable hypotheses.  By relying on ''assumptions'' about nature rather than ''observations'', the theories of relativity violate [[Isaac Newton]]'s rule against the use of hypotheses:  "Hypotheses non fingo" ("I feign no hypotheses)".<ref>http://plato.stanford.edu/entries/newton-philosophy/</ref>  Relativity also rejects -- without any experimental evidence -- Newton's [[action at a distance]], which is basic to Newtonian gravity and [[quantum mechanics]].

'''Relativity''' is a mathematical system built on untestable hypotheses.  By relying on ''assumptions'' about nature rather than ''observations'', the theories of relativity violate [[Isaac Newton]]'s rule against the use of hypotheses:  "Hypotheses non fingo" ("I feign no hypotheses)".<ref>http://plato.stanford.edu/entries/newton-philosophy/</ref>  Relativity also rejects -- without any experimental evidence -- Newton's [[action at a distance]], which is basic to Newtonian gravity and [[quantum mechanics]].

The [[non-locality]] of [[quantum mechanics]] and [[Newton]]ian physics contradicts the theories of relativity, which assume that time is an intrinsic part of space.  Causality breaks down under '''relativity''' if information can be transmitted faster than the speed of light.  In addition, the [[uncertainty principle]] suggests that light [[photons]] must sometimes travel faster than the speed of light despite the assumption of relativity; "[t]he only

The [[non-locality]] of [[quantum mechanics]] and [[Newton]]ian physics contradicts the theories of relativity, which assume that time is an intrinsic part of space.  Causality breaks down under relativity if information can be transmitted faster than the speed of light.  In addition, the [[uncertainty principle]] suggests that light [[photons]] must sometimes travel faster than the speed of light despite the assumption of relativity; "[t]he only

known way to resolve this tension involves introducing the idea of antiparticles."<ref>http://nobelprize.org/nobel_prizes/physics/laureates/2004/wilczek-lecture.pdf (p. 102)</ref>  Quantum field theory is another attempt to partially reconcile relativity with quantum mechanics.  But "quantum field theory, which was born just fifty years ago from the marriage of quantum mechanics with relativity, is a beautiful but not very robust child."<ref>http://nobelprize.org/nobel_prizes/physics/laureates/1979/weinberg-lecture.pdf (p. 556)</ref>

known way to resolve this tension involves introducing the idea of antiparticles."<ref>http://nobelprize.org/nobel_prizes/physics/laureates/2004/wilczek-lecture.pdf (p. 102)</ref>  Quantum field theory is another attempt to partially reconcile relativity with quantum mechanics.  But "quantum field theory, which was born just fifty years ago from the marriage of quantum mechanics with relativity, is a beautiful but not very robust child."<ref>http://nobelprize.org/nobel_prizes/physics/laureates/1979/weinberg-lecture.pdf (p. 556)</ref>

Since speed is relative, it follows that two observers in different inertial reference frames may disagree on the mass and kinetic energy of a body. Since all inertial reference frames are treated on an equal footing, it follows that mass and energy are interchangeable.

Since speed is relative, it follows that two observers in different inertial reference frames may disagree on the mass and kinetic energy of a body. Since all inertial reference frames are treated on an equal footing, it follows that mass and energy are interchangeable.

There is a logical difficulty, however, to an increase in relativistic mass.  Such increase would only exist in the direction of motion, and the rest mass would remain intact with respect to a force applied in a direction orthogonal to velocity.  But mass is not a vector, and the notion of the mass of an object having different values depending on the direction of an applied force is unacceptable.  Accordingly, most physicists today avoid Einstein's original reliance on relativistic mass and his suggestion that mass increases.  Instead, most physicists today teach that  

There is a logical difficulty, however, to an increase in relativistic mass.  Such increase would only exist in the direction of motion, and the rest mass would remain intact with respect to a force applied in a direction orthogonal to velocity.  Neither mass nor energy is a vector, and the notion of the mass of an object having different values depending on the direction of an applied force is illogical.  In recent years most physicists have shifted away from Einstein's original reliance on relativistic mass and his suggestion that mass increases.  Instead, most physicists today teach that  

:<math>F=\frac{d}{d\tau} p</math>  

:<math>F=\frac{d}{d\tau} p</math>