When physicists study the edge of the visible universe, they are not directly observing "nothingness" or empty space. Instead, they are observing the cosmic microwave background radiation (CMB), which is the faint afterglow of the Big Bang. The CMB permeates the entire observable universe and provides valuable information about its early stages.
The CMB is not uniform and exhibits slight temperature variations across the sky. Scientists use sophisticated instruments, such as space-based telescopes like the Planck satellite, to measure these temperature fluctuations. These measurements help in understanding the structure and composition of the universe on large scales.
By analyzing the patterns and statistical properties of the CMB, physicists can gather insights into the universe's composition, its evolution, and the underlying cosmological principles. They can determine the density and distribution of matter, the presence of dark matter and dark energy, and test various cosmological models.
Regarding the null hypothesis, scientists establish a range of theoretical expectations based on our understanding of cosmology. They develop mathematical models and simulations to predict the expected patterns and fluctuations in the CMB. By comparing their observations to these theoretical predictions, they can evaluate whether the data aligns with the current understanding of the universe or if it requires modifications to existing models.
It's worth noting that the study of the edge of the visible universe is an active area of research, and our understanding continues to evolve. New observations, improved measurements, and refined theoretical frameworks contribute to our understanding of the early universe and its evolution.