# What is the border between quantum mechanics and classical mechanics?

Jul 27, 2022

In classical mechanics, objects obey Newton’s laws of motion, which describe how they move in response to external forces. In contrast, quantum mechanics is the branch of physics that studies the behavior of matter and energy in the presence of an observer.

Quantum mechanics has its roots in the early days of quantum theory, when physicists were trying to understand the strange behavior of subatomic particles. In the early 1900s, they developed a theory called quantum electrodynamics, or QED, to describe the behavior of these particles.

However, QED could not explain everything about the subatomic world. In particular, it could not explain the behavior of particles that have very little mass, such as electrons. To explain these particles, physicists developed a new theory called quantum mechanics.

In quantum mechanics, particles do not always obey Newton’s laws of motion. Instead, they follow the laws of quantum mechanics, which are different from the laws of classical mechanics.

One of the key differences between quantum mechanics and classical mechanics is the way that they handle uncertainty. In classical mechanics, objects are described by their position and momentum. However, in quantum mechanics, objects are described by their wave function, which is a mathematical function that contains all the information about the particle’s position and momentum.

The wave function is a probabilistic description of the particle’s behavior. It tells us where the particle is likely to be found, but it does not give us a precise location. This is because the position of a subatomic particle is uncertain.

Another key difference between quantum mechanics and classical mechanics is the way that they handle interactions between particles. In classical mechanics, particles interact with each other through forces. However, in quantum mechanics, particles interact with each other through something called the quantum force.

The quantum force is a force that is mediated by the exchange of virtual particles. It is responsible for the strong nuclear force, the force that holds the nucleus of an atom together. It is also responsible for the force that holds electrons in their orbit around the nucleus.

Finally, quantum mechanics and classical mechanics differ in the way that they describe the behavior of time. In classical mechanics, time is a continuous quantity. However, in quantum mechanics, time is a discrete quantity. This means that it is divided into small units, such as the Planck time.

The Planck time is the time it takes for light to travel the distance of one Planck length. It is the smallest unit of time that can be measured, and it is incredibly small. In fact, it is so small that it is almost impossible to imagine.

Despite these differences, quantum mechanics and classical mechanics are both essential theories of physics. They are both needed to understand the behavior of subatomic particles.

## Other related questions:

### Q: What is the relation between quantum mechanics and classical mechanics?

A: There is a fundamental difference between quantum mechanics and classical mechanics. Classical mechanics is based on the principle that the behavior of physical systems is determined by the laws of classical physics, while quantum mechanics is based on the principle that the behavior of physical systems is determined by the laws of quantum mechanics.

### Q: Can quantum mechanics explain classical mechanics?

A: Quantum mechanics can explain classical mechanics if the classical mechanics is considered to be a limit of quantum mechanics.

### Q: What’s the difference between quantum mechanics and classical mechanics?

A: Quantum mechanics is the branch of physics that studies the behavior of matter and energy in the presence of an observer. It is the foundation of modern physics and the theory of the wave-particle duality.

Classical mechanics is the branch of physics that studies the behavior of matter and energy in the absence of an observer. It is the foundation of Newtonian physics and the theory of the four forces.