The estimation that the number of atoms in the universe is approximately 10^80 is based on certain assumptions and calculations derived from our current understanding of cosmology and physics. Here's a simplified explanation of how this estimation is made:
Observable Universe: The estimation refers to the observable universe, which is the portion of the universe that we can observe from Earth. It is important to note that the universe may be much larger than the observable universe, but we can only make observations within our observable horizon.
Cosmic Microwave Background (CMB): The CMB is the faint radiation left over from the early stages of the universe, which provides valuable information about its characteristics. It is nearly uniform in all directions but contains slight temperature variations.
Density Fluctuations: By studying the temperature fluctuations in the CMB, scientists can analyze the density fluctuations of matter in the early universe. These fluctuations are believed to have led to the formation of structures like galaxies and galaxy clusters.
Baryonic Matter: Baryonic matter refers to ordinary matter composed of protons, neutrons, and electrons. Scientists estimate the total amount of baryonic matter in the universe by measuring the average density of matter and extrapolating it to the entire observable universe.
Critical Density: The critical density is a concept in cosmology that represents the average density required for the universe to be spatially flat. Observations suggest that the total density of matter and energy in the universe is close to this critical density.
Volume of the Observable Universe: By considering the critical density and the overall mass-energy content of the observable universe, scientists can estimate its total volume.
Avogadro's Number: Avogadro's number (approximately 6.022 × 10^23) represents the number of atoms or molecules in one mole of a substance.
By combining these factors and performing calculations, scientists estimate that the number of atoms in the observable universe is on the order of 10^80. It's worth noting that this estimation may vary depending on assumptions, new observations, and advancements in our understanding of the universe.