The notion of the "quantum realm" or the behavior of particles at the quantum level is indeed distinct from our macroscopic everyday experience. At the quantum level, particles exhibit wave-particle duality, superposition, and entanglement, which are phenomena that are not directly observable in our everyday macroscopic world.
However, it's important to note that the scale and behavior of the quantum realm are significantly different from the vastness of the universe as a whole. The quantum realm refers to the microscopic scale, where the laws of quantum mechanics govern the behavior of particles like electrons, photons, and atoms. On the other hand, the universe as a whole encompasses a wide range of scales, from the microscopic to the macroscopic, including galaxies, stars, planets, and even larger cosmic structures.
While there is empty space between particles at the quantum level, it doesn't necessarily imply that the universe as a whole is similarly "empty" or that we exist within a quantum level. The universe is a complex and dynamic system, composed of various forms of matter, energy, and forces, interacting on different scales. Our understanding of the universe is primarily based on classical physics and general relativity, which provide effective descriptions of macroscopic phenomena.
Quantum mechanics, on the other hand, is a theory that describes the behavior of particles at the quantum level, but it has different rules and principles than classical physics. While quantum mechanics is incredibly successful in explaining the behavior of particles at small scales, there is currently no widely accepted theory that unifies quantum mechanics with gravity and explains the behavior of the universe as a whole.
In summary, while the quantum realm and the behavior of particles at the quantum level are fascinating, it is important to distinguish them from the vastness and complexity of the universe. The universe encompasses a wide range of scales and phenomena, and our understanding of it is based on a combination of classical and quantum physics, as well as ongoing scientific exploration and research.