Vũ trụ là vô cùng lớn. Vấn đề vũ trụ thực tế là vô hạn hay hữu hạn hiện vẫn còn nhiều tranh luận. | PARTICLE FAMILIES particles but also the various forces. All matter particles feel the weak force carried by W particles made of an electron and antineutrino or vice versa and by Z particles with a neutrino and antineutrino or some other composition. Photons made of an electron and anti-electron carry the electric force to which all charged particles respond. The strong nuclear force felt only by proton-like matter particles and mesons is carried by gluons colour and anticolour within the particles and by mesons quark and antiquark operating between the particles. Mathematically all of these forces are described by so-called gauge theories which give the same results wherever you start from. The electric force provides a simple example of indifference to the starting point in a pigeon perching safely on a power line while being repeatedly charged to 100 000 volts. Signals of a fraction of a volt continue to pass in a normal manner through the bird s nervous system. Indifference to circumstances is a requirement if the various forces are to operate in exactly the same way on and within a proton whether it is anchored in a mountain or whizzing through the Galaxy close to the speed of light as a cosmic-ray particle. In other words gauge theories are compatible with highspeed travel and Albert Einstein s special theory of relativity. The obligation that the force theories must be of this type strengthens the physicists confidence in them. Those four paragraphs sum up the Standard Model a well-rounded theory and one of the grandest outcomes of 20th-century science. It was created and largely confirmed in an era of unremitting excitement. Almost as fast as theorists plucked ideas from their heads experimenters manufactured the corresponding particles literally out of thin air in the vacuum of their big machines. It was as if Mother Nature was in a mood to gossip with the physicists about her arcane ways of running the Universe. The frenzy lasted for about 20 years .
