Splitting Quarks? Splitting Strings?

Question

Not that long ago we thought the atom was indivisible and as small as anything could get, then we discovered subatomic particles, then quarks. Right now quarks are known to exist and strings (string theory) are thought to make them up but it's figured that they're the bottom line, much like atoms and molecules before them. It just seems like a matter of time before a quark is opened, and if strings or otherwise are found that'll be opened, then whatever is next gets opened. Is there/does there have to be a bottom line? How do we know we aren't 100 steps away still? Could we be?

Answer 1

Could we be?  Yes.

Is there any evidence that shows quarks and leptons to be anything other than fundamental, point particles?  No.

As always, we'll keep looking.

Answer 2

It is impossible to know how far away we are from the bottom line. If you believe that strings have 1 spatial dimension, length, then they could logically be broken down into a single point with 0 spatial dimensions. But what at first appears to be a point, might not be a point at all. There could be an entire universe existing within that point. Or our entire universe might be only a point in an even larger universe.

We as a species know very, very little about how our world works. We may be limited only by our ability to imagine. Perhaps the universe exists only in our own mind, its size and complexity limited only by our own imagination.

Answer 3

The evidence that quarks and leptons (electron family) are point particles comes mainly from deep inelastic scattering patterns. However, there have been theories that both quarks and leptons have an internal structure.

Haim Harari (born 1940) is an Israeli theoretical physicist, who in April 1983 published a paper titled 'The Structure of Quarks and Leptons'. In this paper, he mentions an earlier internal structure model developed by J. C. Pati and A. Salam (electroweak theory) in 1974. This earlier model used the term 'prequark' or preon as a generic name for hypothetical sub-constituents of quarks and leptons. However, the Harari model for sub-quark and lepton structure (first developed in 1979) uses the name rishon (Rishon is the Hebrew adjective meaning first or primary) for two species of fundamental building blocks. The rishons were called T and V, for ‘Tohu’ ‘Vavohu’, Hebrew for 'formless and void'; the description of the initial state of the universe given in the first chapter of Genesis. One rishon T had a charge of +1/3 and the other V had a neutral charge. The antirishons T' had a charge of -1/3 and v' had a charge of zero.

The model constructed quarks and leptons by combining three rishons or antirishons but they could not be mixed in the same particle. This combination rule gives rise to sixteen quarks and antiquarks along with leptons and antileptons. For example, TTT (charge sum +1/3  +  +1/3 + + 1/3) gives rise to a total charge of +1e and a positron. Conversely T'T'T' has a total charge of -1e and is an electron. The neutrinos and their anti-partners could be made from VVV or V'V'V'. A u, or up, quark could be TTV and a d, or down, quark from TVV. An anti d quark would be V'V'T with the anti u as V'T'T'.  

The model also described the colour force of QCD using the colours red, yellow, and blue for the T rishon and anti-colours  for the V rishon. This colour 'force' was known as 'hyper-colour' with a confinement range of 10^-18 m. For example, a TTV state might have rishon colours of red, blue, and anti-blue leaving a nett colour of red. This colour scheme, for the rishons, was consistent with the rules of colour force exchange within QCD.

This model was successful with the first generation, or family, of quarks and leptons but did not work well with the second or third generation families (strange, charm, muons, bottom, top, and tau).

Like many models of quarks structure, Haim Harari' appears to be confined to the history books. Try: -

http://en.wikipedia.org/wiki/Harari_Rish...

for some more details.

As for string theory! It has five different versions, known of which seem to describe the physical world we see it! As I am aware, there are no sub-string models – as of yet!

I hope this is of some assistance!