Quantum mechanics
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Quantum mechanics explains how extremely small things work - like atoms and molecules.
Some ideas in quantum mechanics can be used to understand how small objects combine into large objects like stars, and even the whole Universe.
Some parts of the theory are controversial. Some results from quantum mechanics seem to disagree with the theory of relativity.
Quantum mechanics describes nature in a way that is different from how we usually think about science, relying on probability rather than certainty.
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[change] History
Light was first thought to be made of particles. Isaac Newton called these particles "corpuscles". With this idea, he could explain how light behaved. Later, Christiaan Huygens thought that light was made of waves. These theories seemed to be conflicting with one another.
It turns out that both theories are correct - light can have particle and wave properties. We call this "wave-particle duality".
[change] The Heisenberg Uncertainty Principle
In Quantum mechanics, the Heisenberg Uncertainty Principle says that the more we know about where something is, the less we can know about how fast it is going; the more we know about something's speed, the less we can know about its position.
[change] Photoelectric effect
In 1905, Albert Einstein proved that although light is like a wave, it is made of particles of energy called photons. This came from the photoelectric effect.
This began quantum theory, where all subatomic particles like electrons, protons, neutrons, and others are both waves and particles at the same time. See picture of atom with the electron as waves at atom.
For other parts of quantum mechanics, see Schrödinger equation and quantum entanglement.
[change] Observation
A key part of quantum theory is that certain attributes of particles, such as position, speed, direction it moves in, and spin, are not defined until they are observed. It is instead in what is called a “superposition of states”.
[change] Uses
Quantum mechanics is useful for:
[change] Quantum mechanics
Quantum mechanics is a science that deals with how the atoms and subatomic particles (particles that are smaller than atoms) in matter and waves behave. It forms a mathematical framework for modern physics and chemistry. It also helps to explain how large objects like stars and planets are formed and why big events in space happen, like the Big Bang.
Quantum in Latin means 'how much'. It is used in quantum mechanics to describe set units that the theory gives to different properties. The basic parts of quantum mechanics were made during the first half of the year 1900 by Max Planck, Albert Einstein, Niels Bohr, Werner Heisenberg, Erwin Schrödinger, Max Born, John von Neumann, Paul Dirac, Wolfgang Pauli and others.
Quantum mechanics was first developed to explain the atom, especially the light emitted by different types of atoms. The quantum theory of the atom developed as an explanation for the electron staying in its orbit, which could not be explained by other theories.
The other thing that led to quantum mechanics was the study of electromagnetic waves such as light. It was found in 1900 by Max Planck that the energy of waves could be described as made of small packets or quanta. Albert Einstein used this idea to show that an electromagnetic wave such as light could be described by a particle called the photon with a set amount of energy, depending on its frequency. This led to a theory about subatomic particles and electromagnetic waves called wave-particle duality. This is where particles and waves were neither one or the other, but had certain properties of both.
[change] Other websites
- A history of quantum mechanics
- Introduction to Quantum Theory at Quantiki
- Wikipedia Basics of Quantum Mechanics
- Wikiquotes on Quantum Mechanics
