ecreases it in some places. If electrons are sent through theslits one at a time, one would 深圳桑拿柜锁 expect each to pass through oneslit or the 深圳蒲友按摩论坛 other, and so behave just as if the slit it passedthrough were the only one there – giving a uniform

distributionon the screen. In reality, however, even when the electrons aresent one at a time, the fringes still appear. Each electron,therefore, must be passing through both slits at the same 深圳桑拿洗浴城 time!

The phenomenon of interference between particles has beencrucial to our understanding of the structure of atoms, thebasic units of chemistry and biology and the building blocks outof which we, and everything around us, are made. At thebeginning of this century it was thought that atoms were ratherlike the planets orbiting the sun, with electrons (particles ofnegative electricity) orbiting around a central nucleus, whichcarried positive electricity. The attraction between the positiveand negative 深圳按摩足疗店 electricity was supposed to keep the 深圳宝安西乡桑拿会所 electrons intheir orbits in the same way that the gravitational attractionbetween

the sun and the planets keeps the planets in theirorbits. The trouble with this was that the laws of mechanicsand electricity, before quantum mechanics, predicted that theelectrons would lose energy and so spiral 深圳桑拿按摩论坛交流 inward until theycollided with the nucleus. This would mean that the atom, andindeed all matter, should rapidly collapse to a state of very highdensity. A partial solution to this problem was found by theDanish scientist Niels Bohr in 1913. He suggested that maybethe electrons were not able to orbit at just any distance fromthe central nucleus but only at certain specified distances. Ifone also supposed that only one or two electrons could orbit atany one of these distances, this would solve the problem of thecollapse of the atom, because 深圳桑拿会所按摩全套 the electrons could not spiral inany farther than to fill up the orbits with e least distances andenergies.

This model explained quite well the structure of the simplestatom, hydrogen, which has only one electron orbiting aroundthe nucleus. But it was not clear how one ought to extend itto more complicated atoms. Moreover, the idea of a limited setof allowed orbits seemed very arbitrary. The new theory ofquantum mechanics resolved this difficulty. It revealed that anelectron orbiting around the nucleus could be thought of as awave, with a wavelength that depended on its velocity. Forcertain orbits, the length of the orbit would correspond to awhole number (as opposed to a fractional number) ofwavelengths of the electron. For these orbits the wave crestwould be in the same position each time round, so the waveswould add up: 深圳按摩哪家好 these orbits would correspond to Bohr’s allowedorbits. However, for orbits whose lengths were not a wholenumber of wavelengths, each wave crest would eventually becanceled out by a trough as the electrons went round; theseorbits would not be allowed.

A nice way of visualizing the wave/particle duality is theso-called sum over histories introduced by the Americanscientist Richard Feynman. In this approach the particle is notsupposed to have a single history or path in space-time, as itwould 深圳夜生活 桑拿按摩 in a classical, nonquantum theory. Instead it is supposedto go from A to B by every possible path. With each paththere are associated a couple of numbers: one represents thesize

of a wave and the other represents the position in thecycle (i.e., whether it is at a crest or a trough). The probabilityof going from A to B is found by adding up 深圳桑拿iso全套 the waves for allthe paths. In general, if one compares a set of neighboringpaths, the phases or positions in the cycle will differ greatly.

This means that the waves associated with these paths willalmost exactly cancel each other out. However, for some sets ofneighboring paths the phase will not vary much between paths.

The waves for these paths will not cancel out Such pathscorrespond to Bohr’s allowed