In a repeat conclusion to keeping it simple in the Universe, we see that symmetry is the repeating beauty. The Standard model is not accepted as the theory of everything by anyone. For one thing, it is the ugliest organization of asymmetrically numbered particles but it almost works. The theories that use the 4 known forces in the Universe have to add gravity by hand and the equations usually blow up or don't work smoothly because there is not enough room to unite them with gravity In 3 dimensions. There is a theory that creates gravity automatically and allows gravity to naturally appear - and that is String Theory. With extra dimensions, there is room to allow all the forces to unite along with gravity.

2,000 years ago Democritus theorized the Universe was made of atoms (that which can not be cut) but Pythagoras saw that strings of different lengths had different frequencies and saw the Universe in terms of music with beauty and harmony and of course symmetry. I see how they were both right in their way. Today we are on the brink
of a TOE a theory of everything. While everything in science is derived indirectly to be true it must be testable, reproducible and falsifiable. For String Theory that test will be to perfectly derive the mass of a proton using string theory equations. That is how close we are and yet far away.