Well this is a straight forward question that I have been thinking about. I have been doing some personal research on particle mechanics, it is just a little hobby of mine to think about and research particle based mechanics. In addition to the electron there are two other particles just like it, the mu and tau mesons. ** Why is it that after ‘NATURE’ went through the trouble of making the electron did ‘IT’ go through the further trouble of making it again and again?** This aspect of physics and particle structure/evolution has puzzled me though and though. What say you all that dabble in physics??
I’d recommend redaing The Elegant Universe by Brian Greene. In it he discusses that’s a question that plagued many physicists since the discovery of these “extra” particles. After the muon was discovered, Nobel Laureate Isidor Isaac Rabi asked “Who ordered that?”
I’m not trained in physics, so I’m sure someone more qualified than myself will explain it better. But AFAIK from the book, the short answer is that Nature didn’t really have a choice. The nature of the universe is such that the existence particles is in fact inevitable.
Or at the very least, any cogent Theory of Everything needs to be one that makes the exitsence mu and tau mesons not only possible, but necessary.
…as far as I know, anyway.
Philosphr, I don’t think there can ever be an answer to your question. Any legitimate ultimate theory must of course explain why there are three generations of quarks and leptons, but that just begs the question of why that particular TOE is the way things are. Ultimately, the question is a matter of philosophy, not physics.
Basically, nobody knows. There’s certainly no obvious answer, nor even any widely accepted, answer to why the number of “families” in the Standard Model of particle physics is more than just one. It’s probably unhelpful to just think in terms of electrons, muons and taus; each of these comes with a pair of quarks and a neutrino. The issue is also closely tied to the origin of different masses and so most explanations are couched in terms of “symmetry breaking” (a sort of more ambitious varient of the Higgs mechanism). Endless schemes have been proposed, but there’s no one that’s obviously more compelling than the crowd of others. Though particular proponents might vehemently disagree with that assessment.
The one area where the fact that there’s at least three families makes a big difference is that it’s only then that the Standard Model’s explanation of CP violation becomes possible. Thus if there were only a single family, then it appears that the slight imbalance between matter and antimatter that arose in our universe during the Big Bang wouldn’t have happened.
Otherwise, Rabi’s puzzlement still stands.
I understand that gr8rguy, I was simply wondering what if anything, other dopers who reasearch/already know about the phenomenon. Thats all. I understand the question falls on a certain amount of philosophy…so…philosophize!
Oh, well, obviously, there are three generations because there are three spatial dimensions. And there are three spatial dimensions because of the entire Trinity thing. Basically, three’s a great number! Or that’s my best guess. 
Although I think bonzer is correct in saying that you need multiple generations or else you can’t get a matter/antimatter imbalance, and it would obviously be pretty bad for us if there weren’t one.