Editing Preon (section)

===Unresolved problems with the Standard Model===
The Standard Model also has a number of problems which have not been entirely solved. In particular, no successful theory of [[gravitation]] based on a particle theory has yet been proposed. Although the Model assumes the existence of a graviton, all attempts to produce a consistent theory based on them have failed.

Kalman<ref>{{cite journal |last=Kalman |first=C.S. |year=2005 |title=Why quarks cannot be fundamental particles |journal=Nuclear Physics B: Proceedings Supplements |volume=142 |pages=235–237 |doi=10.1016/j.nuclphysbps.2005.01.042 |arxiv=hep-ph/0411313 |bibcode=2005NuPhS.142..235K |s2cid=119394495 }}</ref> asserts that, according to the concept of [[atomism]], fundamental building blocks of nature are indivisible bits of matter that are ungenerated and indestructible. Neither leptons nor quarks are truly indestructible, since some leptons can decay into other leptons, some quarks into other quarks. Thus, on fundamental grounds, quarks are not themselves fundamental building blocks, but must be composed of other, fundamental quantities—preons. Although the mass of each successive particle follows certain patterns, predictions of the [[rest mass]] of most particles cannot be made precisely, except for the masses of almost all baryons which have been modeled well by de&nbsp;Souza (2010).<ref>{{cite journal |last=de&nbsp;Souza |first=Mario Everaldo  |year=2010 |title=Calculation of almost all energy levels of baryons |journal=[[Papers in Physics]] |volume=3 |pages=030003–1 |doi=10.4279/PIP.030003 |url=http://www.papersinphysics.org/papersinphysics/article/download/64/pdf64 |doi-access=free }}</ref>

The Standard Model also has problems predicting the large scale structure of the universe. For instance, the SM generally predicts equal amounts of matter and [[antimatter]] in the universe. A number of attempts have been made to "fix" this through a variety of mechanisms, but to date none have won widespread support. Likewise, basic adaptations of the Model suggest the presence of [[proton decay]], which has not yet been observed.