The calculation of the number of atoms in the universe, particularly after the Big Bang, is complex due to the universe's potential infinite extent. Atoms became stable approximately 380,000 years post-Big Bang during the recombination epoch. Current estimates indicate an average density of 0.25 atoms per cubic meter in the observable universe, contributing to about 4.9% of the total energy density, as per the Lambda-CDM model. The remaining energy density consists of 27% dark matter and 68% dark energy, with the exact nature of these components still largely unknown.
PREREQUISITESAstronomers, cosmologists, physicists, and anyone interested in the fundamental structure and composition of the universe.
Technically, atoms couldn't form and remain stable until the recombination epoch, about 380,000 years after the Big Bang. Some of the best evidence for the Big Bang theory itself, comes from the analysis of the expected proportion of light elements during this initial phase of nucleosynthesis.zaman786 said:TL;DR Summary: how do we calculated the number of atoms at the start , after big bang?
hi, how do we calculated the number of atoms at the start of universe i.e, after big bang?
Wikipedia says 0.25 per cubic meter in the observable universe.Vanadium 50 said:Are you sure?
Their references areIn the observable universe, atoms have an average density of 0.25 atoms/m³. According to the Big Bang model (Lambda-CDM model), they make up around 4.9 percent of the total energy density. The remaining 95.1 percent, whose nature is still largely unclear, is composed of about 27 percent dark matter and 68 percent dark energy, as well as small contributions from neutrinos and electromagnetic radiation.