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Atom in Modern Science
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in Bombay, because we know that its spin is equal and opposite to its twin, i.e. down'. Somchow, the particle in Bombay knows that its twin is spinning up. In other words, what was done in New York affected what happened in Bombay. This strange phenomenon is known as the Einstein-Podosky-Rosen (EPR) effect. How docs the particle in Bombay know which axis has been chosen? There is no time for it to receive the information from the other particle by any conventional signal. EPR's thought experiment is the Pandora's Box of modern physics. It inadvertently illustrated an inexplicable connectedness between particles in two far away different places. This is the crux of the EPR experiment, and this is where Einstein disagreed with Bobr.
EINSTEIN VS. BOHR
Einstein asserted that no signal can be instantaneous i.e. faster than the speed of light. According to Bohr, the twin-particle systein is an indivisible whole, even if they are separated by a great distance. But the connections are not 'signals in the Einstcinian sense; they transcend our conventional notions of 'information-transfer'. EPR's thought experiment indicates that the signal between the two particles is transmitted at superluminal spccd, i.c. faster than the speed of light. The concept of a "faster-than-light" communication between events, which cannot be connected by a signal (the definition of space- like), is as much a radical departure from current physical theory as Einstein's special Theory of Relativity was for the accepted (classical) physics of 1905. Nonetheless, it is logically consistent with canonical physical thought. In fact, it can be derived from the indivisibility of Planck's quantum for action, which is the basic clement of quantuin theory.
Relativity pcrinits the hypothetical existence of particles called "tachyons", which come into existence already travelling faster than light. In the formalism of the special theory of relativity, tachyons have an imaginary rest-mass. Unfortunately, it is difficult to interpret what an "imaginary rest-mass" means in physical terms, or what the interaction forces would be between tachyons and the ordinary particles with real rest-mass.