Astronomers believe that our universe experienced a sudden burst of rapid expansion in mere fractions of a second after the Big Bang, causing the universe to grow from "an infinitesimally small speck to one spanning a quarter of a billion light-years in mere fractions of a second" (Shmahalo). While individual regions become "bubble universes" and stop inflating, the exponential expansion, once started, continues forever. As it continues to expand, some parts quicker than others, new "bubble universes" are formed. Inflation lies at the foundation for the multiverse theory.
Since 30 years ago, observations of the cosmic microwave background, the light emitted by the cooling universe 380,000 years after the Big Bang, have offered support for inflation. The size of the blotches in the cosmic microwave background follows a distribution that is consistent with inflation models. Alan Guth, an MIT theoretical physicist says "It's not impossible [to build models that do not lead to a multiverse], so I think there's still certainly research that needs to be done. But most models of inflation do lead to a multiverse, and evidence for inflation will be pushing us in the direction of taking the idea of a multiverse seriously." With possible evidence of inflation, models for multiverse come naturally. On March 17th of last year, John Kovac of the Harvard-Smithsonian Center for Astrophysics and his BICEP2 "a distinct curl in the polarization pattern of the CMB," or Cosmic Microwave Background (Kramer). This "distinct curl" can be interpreted as being caused by inflated gravitational waves and thus would directly support both the theories of inflation and the multiverse. However, analysis of data from the Keck Array telescope at the South Pole and maps of dust emission from the European Space Agency's Planck collaboration has shown that the signal claimed to evidence of inflation is in fact caused by dust within the Milky Way. The dust finding does not necessarily refute inflation nor does it support the theory.
Thus, although there has been new findings that seem to support the multiverse theory, there is no direct evidence to prove it. All lines of "evidence" are currently indirect or ambiguous because they too are based on theories for the most part. As humans in our bubble universe, we cannot see what is happening outside. At least with current technology, we cannot say for certain whether a multiverse is possible.
- Alice Zhang