The idea of String Theory is that our Universe came from a higher-dimensional, more symmetric, more complex state with an enormous number of degrees of freedom. In order for String Theory to be solved, we need to get rid of all the excess predictions it makes until we are only left with the Universe we observe. The problem of how we get from there to here has not been solved. (Credit: NASA/Goddard/Wade Sisler)
Inflation, dark matter, and string theory are all proposed extensions to the prior consensus picture. But what does the evidence say?
There are two things that never seems to fall out of fashion when it comes to theoretical physics: people proposing wild new ideas that attempt to make sense of the Universe, and people declaring that some of the best and most well-established theories must be wrong. Physics is generally a conservative science, where the broader community is slow to accept anything novel unless the evidence supporting it becomes so overwhelming that all of the alternatives become untenable. Many grand ideas have come along in recent years, including:
grand unified theories,
extra dimensions,
the notion that the Higgs is a composite particle,
supersymmetry,
dark matter,
dark energy,
cosmic inflation,
and string theory,
among many others. However, nearly all of these ideas remain in the speculative category, as the critical evidence supporting their existence is sorely lacking.
