"Quantum physics thus reveals a basic oneness of the universe"
Erwin Schrödinger
In the early years of the 20th century, some of the leading physicists of the time began to develop new theories that would turn the scientific world's view of how the physical universe works completely on its head. These new theories came to fall under the general umbrella of a completely new approach known as "Quantum Theory" or "Quantum Physics".
In essence, they began to realize that we are not, as we had thought for 300 years under classical physics, merely passive observers, but are integrally connected with everything in the universe.