Answer: Can we divide leptons and quarks into even smaller particles?

so Mario asks is it possible to divide leptons and quarks into more fundamental quarks and how can we prove that they are the most fundamental particles if we can't keep doing this can we only separate one particle into smaller particles well that's a good question because the history of physics is that we have found that if we look at elementary particles atoms we discover that they're made out of simpler objects I mean democrates over two and a half millennium ago hypothesized that all of matter was made out of atoms which and atoms were always thought to be indivisible point like objects and in fact we discovered convinced by the end of the 19th century that matter indeed was made out of atoms but understood very soon that Adams had structure electrons and nuclei and then we understood that the nucleon has the nucleus of atoms has structure the nucleus is made out of protons and neutrons and later we've understood that protons and neutrons have structure they're made out of point like quarks so today our standard theory of elementary particle physics is based on a theory of matter which identifies the basic constituents of matter as point like electrons neutrinos and quarks but of course everyone was open to the idea that electrons and quarks themselves would exhibit structure and might be made out of even more fundamental sub electron sub quarks we haven't given them good names because we haven't found them we've been looking we now can probe the structure of electrons and quarks down to let see roughly one millionth of their size so it's as if we have a microscope where we can blow up a quark to a very big radius and look inside with great detail and we have seen no evidence that they have any structure at all now it just might be that the point-like objects were looking at inside quarks and leptons are even smaller but there's no evidence for that at all and it could be that this is the end of the story could be that quarks and leptons are themselves truly the point-like constituents of matter however there are various open problems in elementary particle physics and our exploration of matter that suggests that there is no physics at shorter land scales but it might be of a different nature and indeed there are attempts to unify all the forces of nature based on something called string theory in which when you look at a cork with a very good microscope much much better by factors of a million times a million times better than what we have today you would see not sub quarks not that the cork was made out of three or four or some number of smaller units but rather the cork is not a point-like object at all it's an extended streamlined object it's a vibrating string and that's a totally different approach to what makes up the different elementary particles not even smaller point-like particles but different modes of vibration of a single extended object and string theory in fact you have only one string but it vibrates differently different kinds of vibrations much like a a violin string has many different harmonics and in string theory all the elementary particles that we see our simply different vibrational modes are the same extended string so that's a way of having sub structure but not point nu point like sub structure

Channel: Nobel Prize

Views: 30,134

Rating: 4.888268 out of 5

Keywords: leptons, quarks, subatomic physics

Id: ZorRPAD32i4

Length: 4min 44sec (284 seconds)

Published: Wed Jul 14 2010