The concept of the universe having an infinite density is rooted in the study of black holes and the Big Bang theory. While we don't have direct observational evidence to confirm the universe's density with certainty, several lines of theoretical and observational evidence suggest that the universe does not have an infinite density.
Expansion of the Universe: The observation that the universe is expanding, initially inferred from the redshift of distant galaxies, led to the development of the Big Bang theory. This theory suggests that the universe originated from an extremely hot and dense state known as a singularity. However, it does not imply that the singularity itself had infinite density. Instead, it signifies a moment of extremely high energy and temperature.
Cosmological Observations: Detailed observations of the cosmic microwave background radiation (CMB) provide strong evidence for the Big Bang theory. The CMB is the remnant radiation from the early universe, which has cooled and stretched due to the expansion of space. These observations match the predictions of an expanding universe that started from a hot, dense phase, but they don't directly address the question of infinite density.
Black Holes: Black holes are regions of spacetime where gravity is so intense that nothing, not even light, can escape from their gravitational pull. According to general relativity, the gravitational collapse of a massive object can lead to the formation of a singularity at the center of a black hole. While the singularity represents infinite density in theory, it is currently believed that our understanding of singularities breaks down at the quantum level. This indicates that our current laws of physics might not accurately describe the conditions inside a black hole.
In summary, our current understanding of the universe suggests that it originated from a hot, dense state during the Big Bang. While the concept of a singularity with infinite density is a possibility according to classical general relativity, it is unclear whether this concept accurately represents the true nature of the universe. Further advancements in theoretical physics and a better understanding of the interplay between general relativity and quantum mechanics may help resolve this question.