Number of particles in the observable universe
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Total Number of Particles in the Observable Universe
Baryons, Electrons, and Atoms: Matter Particles in the Universe
The number of baryons (such as protons and neutrons) and electrons in the observable universe is estimated to be around 10^80. This figure is widely supported and often referred to as the Eddington number, which is also used to estimate the number of atoms in the observable universe, since each atom typically contains one electron and one or more baryons 125810. This estimate is based on observations of visible matter and is consistent across multiple studies.
Photons and Neutrinos: Abundant Massless and Nearly Massless Particles
Photons, which make up the cosmic microwave background, are far more numerous than baryons or electrons. The number of photons in the observable universe is about 10^89, which is roughly nine orders of magnitude greater than the number of baryons or electrons. Neutrinos, which are extremely light and weakly interacting particles, are estimated to exist in similar numbers to photons, also around 10^89 14.
Gravitons: Hypothetical Particles with Enormous Numbers
Gravitons, the hypothetical quantum particles that would mediate the force of gravity, could vastly outnumber all other particles. Estimates suggest that the number of gravitons in the observable universe could be as high as 10^113 times a factor related to the tensor-to-scalar ratio from cosmic inflation, potentially making them the most numerous particles by far if they exist 14.
Information Content and Particle Numbers
The total number of matter particles (baryons and electrons) in the observable universe is closely linked to the information content of the universe. Recent estimates suggest that all the matter particles together store about 6 × 10^80 bits of information, with each particle containing roughly 1.5 bits of information about itself .
Conclusion
In summary, the observable universe contains about 10^80 baryons and electrons, about 10^89 photons and neutrinos, and potentially up to 10^113 gravitons if they exist. These numbers highlight the vast scale and complexity of the universe, with photons and neutrinos far outnumbering matter particles, and gravitons possibly outnumbering all other particles combined.
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