It is difficult to understand some of the concepts of both the Copenhagen Interpretation and the Schroedinger's Cat thought experiment without knowing at least a little bit about Quantum Physics, which is in turn based on Classical Physics. Physics a word based of of the greek word physis, meaning nature. Physics originated with the greek physicist Aristotle, who worked on the original five elements, causality, optics, chance and spontaneity. This was the foundation of modern physics, which describes matter in all its forms, and how it moves through space and time. Several simple examples are gravity, momentum, acceleration, electromagentism, thermodynamics, heat, and optics. Classical physics can be applied to almost everything, but not to the inside of an atom. There, the laws of classical physics break down.

The Theory that accurately describes the insides of atoms is Quantum Physics, which describes everything in terms of quanta, or discrete units of energy, not continuous units. Quantum Physics is preferred for describing systems whose dimensions are close to atomic, including molecules, atoms, electrons, protons, and other subatomic particles. Three of the more important concepts of Quantum Physics are the Photoelectric Effect, wave-particle duality and the Heisenberg Uncertainty Principle.

In Quantum Physics, wave particle duality is a proven concept which states that everything can behave as both waves and particles at the same time. Wave particle duality should be distinguished from is wave particle complementarity, which states that matter can show both wave or particle properties, but not at the same time [4]. Wave particle duality can be traced back to a debate over the nature of waves and matter in the 1600s between physicists Christiaan Huygens and Isaac Newton. Huygens said that light exhibited wave-like properties, while Newton said that light had particle-like properties. Now, in the 20th and 21st centuries, work from physicists like Albert Einstein, Louis de Broglie and several others have proven wave particle duality, ending the centuries long debate over the nature of matter and waves. One well-known example of Quantum Physics that can show this wave particle dualityis the double slit experiment.

The double slit experiment was orignally performed by physicist Thomas Young in 1801 [15]. The double slit experiment is an experiment in quantum physics to show how light behaves like a wave. In this experiment, there is a light source positioned in front of a plate with two thin slits, and a screen behind the plate with the slits. The light source is turned on and emits photons which go through the slits. Once they go through the slits, they start acting as waves by interfering like waves. The two waves combine to form an interference pattern. This interference pattern is shown on the screen as a pattern of light and dark. This proves that light behaves as a waves. However, it also strikes the screen as particles, which means that light acts as both waves and particles (Mouseover image to animate double-slit experiment).

The final important concept of quantum physics is the Heisenberg Uncertainty Principle. A particle cannot be described as a wave or a particle but microscopically in terms of wave-particle duality. This principle states that you cannot know the exact position and momentum of a particle in space-time. The definite placement and momentum of a particle is determined by probability waves, which are the most probable place for the particle to reside. With the Uncertainty Principle, the more you know about the momentum or the position, the less you know about the other variable. The formula for this principle is the change in position times the change in momentum will be greater than Planck's Constant. Planck's Constant is a physical constant describing the sizes of quanta. This can be reduced as seen in the formula. The Uncertainty Principle basically describes what wave-particle duality does to the characteristics of subatomic particles.