After the completion of Standard Model, scientists developed many models trying to describe the subatomic world. Two of the most prevalent ones are Supersymmetry (SUSY) and multiverse.
Multiverse, the more prevalent one in pop culture, claims that there exist many universes outside of ours with different constants. These magical mathematical numbers include the speed of light, gravitational constant, Planck constant, etc. These numbers, when take out of context, have no meaning whatsoever. And yet, the public and even many scientists take those numerical values for granted. Anthropic principle, a philosophical idea in astrophysics, states that the universe has to be the way we observed to foster lives such as us. The “way” of universe includes all the properties and thus all the mathematical descriptions of universe. If the theory were true, however, these values thought to be constant could vary in different universes. For instance, it would very different to living in a world with speed of light only 10m/s. Many subdivision of Multiverse soon germinate and develop into various models. The author of the book The Elegant Universe, Brian Greene discussed nine types of parallel universe. One of the most interesting types is the quilted multiverse in which the speed of light prevents us from being aware of these other identical. In this type, every possible event will occur an infinite amount of times within finite amount of space. Many scientists believe that the success of Multiverse will declare the demise of particle physics since there would be meaningless to delve into the minute realm and only find out varying results in the inconsistent universe.
In particle physics, supersymmetry is a principle for a theory that could answer some of the crucial problems the universe posted unanswered by the Standard Model. For instance, under the model described by the SUSY principle, scientists are able to know the composition of dark matters, the reason gravitational force is weak, and the higgs mechanism. The supersymmetric theory describes that the equations of force and equations of matter are identical. It also predict that there exists the so called “cousin particles” that correspond to the property of each particle described in the Standard Model. These superpartners share the same mass and internal quantum numbers besides spin as the particles with which they pair. In another words, fermions, particles with not-integral spins including leptons and quarks, are predicted to have superpartners that are bosons. Yet, those particles have the same mass energy and carries the same charge as do their superpartners. Scientists coined the name of superpartners simply by adding letter “s” in front of the known particles in the Standard Model. Therefore, selectron is the superpartner of electron that has a spin of 1 and charge of -1. With so promising a prospect, Supersymmetry nonetheless draw criticisms because the principle is not falsifiable since the mechanism that can prove or disproof the theory is yet to be found. Furthermore, many skepticism target the principle for lack of evidence: scientists at LHC have not found any clue that suggest the existence of any superpartners of the existing particles.