When estimating the number of particles in the universe, various types of particles are taken into account at different scales. Here are the primary particles that are typically considered:
Atoms: Atoms are the building blocks of matter and consist of a nucleus containing protons and neutrons, surrounded by electrons. In the context of estimating the number of particles in the universe, atoms are often counted because they are the fundamental units that make up ordinary matter.
Protons and Neutrons: Protons and neutrons are subatomic particles found in the nucleus of an atom. They are collectively referred to as nucleons. While protons carry a positive electric charge, neutrons are neutral. Both protons and neutrons are taken into account when estimating the total number of particles.
Electrons: Electrons are negatively charged particles that orbit the nucleus of an atom. They are much smaller and lighter compared to protons and neutrons. Since electrons play a crucial role in atomic structure and behavior, they are also considered when estimating the number of particles in the universe.
Quarks: Quarks are elementary particles that are the fundamental constituents of protons and neutrons, as well as other particles known as hadrons. Quarks come in different types, such as up, down, charm, strange, top, and bottom. While quarks are not typically counted individually when estimating the total number of particles in the universe, they are indirectly accounted for through their presence in protons, neutrons, and other hadrons.
It's important to note that these particles represent the fundamental constituents of matter at the atomic and subatomic scales. When estimating the number of particles in the universe, astrophysicists and cosmologists consider the collective matter distributed across galaxies, clusters, and other large-scale structures. The exact method used for estimation depends on the specific approach and assumptions made in a given study or model.