Limitations of Existing Data and Theories

• There are periods in the history of the universe for which we have few observations and theories, such as the formation of the first stars and galaxies.
• The composition of the universe is still being explored, as we see the effects of dark matter but have not yet identified any dark matter particles in laboratories.
• The expansion of the universe is not accounted for by current theories of gravity.
• The standard model of physics does not account for antimatter.