Protons, electrons, and neutrons are fundamental particles that make up the atoms in our universe. They exist because they are the building blocks of matter.
According to our current understanding in physics, protons and neutrons are composed of smaller particles called quarks. Protons consist of two up quarks and one down quark, while neutrons consist of one up quark and two down quarks. Quarks are held together by the strong nuclear force, which is mediated by particles called gluons.
Electrons, on the other hand, are elementary particles and are not composed of smaller particles. They are classified as leptons and do not have any internal structure. Electrons have a negative charge and are attracted to the positive charge of protons, which allows them to form stable atoms.
As for where these particles come from, our current understanding is based on the Big Bang theory. According to this theory, the universe began as a hot, dense state about 13.8 billion years ago. During the early stages of the universe, as it expanded and cooled, the energy transformed into matter in the form of particles and antiparticles. However, due to a process known as baryogenesis, there was a slight imbalance between matter and antimatter, resulting in an excess of matter.
As the universe continued to expand and cool, protons, neutrons, and electrons formed as the result of various interactions and transformations of particles. The formation of protons and neutrons occurred during a process called nucleosynthesis, which took place a few minutes after the Big Bang. Electrons were present from the beginning and were eventually captured by atomic nuclei to form atoms.
It's important to note that our understanding of the origins of these particles is based on theoretical models and experimental observations. Scientists continue to study and explore the fundamental nature of particles through particle accelerators, astrophysical observations, and theoretical advancements.