What is quantum theory?

Answer 1

Quantum theory is the mathematical representation of the universe assuming that everything is divided into well defined amounts (quanta, plural of quantum if we ignore the context) that behave both like particles and waves.

One of its basic concepts is that nothing is in one defined position but exists as a distribution of probabilities dispersed in space. The particle itself may react at any point, but it has different probabilities of "appearing" at different positions.

Another characteristic of Quantum Theory is that in it, whatever you cannot measure can be in an infinite different amount of states. The actual state you see when you you finally observe the system depends, not only on what you observe, but also on how you observe it.

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Quantum theory is the language of all particle theories. It is formulated in a well-defined mathematical language that makes predictions for the relative probabilities of the various possible outcomes, but not for which outcome will occur in any given case.

The word quantum means a definite but small amount.

The basic quantum constant h, known as Planck's constant,and its value is 6.626 x 10-34 Js
The quantum theory of physics was developed in order to explain the relationship between matter and energy at an atomic level as well as subatomic. The theory was created by the ideas of Max Planck, Albert Einstein, Niels Bohr, Werner, and many others. It includes basic ideas of quantum physics. One of the most prominent ideas is that matter acts as waves AND as a particle (wave-particle duality). Another crucial idea to the theory is the uncertainty principle. This principle states that certain pairs of values about matter cannot be simultaneously known. For example, if the position of a particle is measured, its momentum value will become less accurate.
At its simplest - it states that the universe is grainy, that energy (like matter) comes in discrete packets rather than being continuous (as it seems to be).

Answer 2

Quantum physics is a branch of science that deals with discrete, indivisible units of energy called quanta as described by the Quantum Theory. There are five main ideas represented in Quantum Theory:

1. Energy is not continuous, but comes in small but discrete units.
2. The elementary particles behave both like particles andlike waves.
3. The movement of these particles is inherently random.
4. It is physically impossible to know both the position and the momentum of a particle at the same time. The more precisely one is known, the less precise the measurement of the other is.
5. The atomic world is nothing like the world we live in.

While at a glance this may seem like just another strange theory, it contains many clues as to the fundamental nature of the universe and is more important then even relativity in the grand scheme of things (if any one thing at that level could be said to be more important then anything else). Furthermore, it describes the nature of the universe as being much different then the world we see. As Niels Bohr said, "Anyone who is not shocked by quantum theory has not understood it." I agree with him on that quote. Always remember this, no one in this world fully understands quantum mechanics or quantum physics.

Answer 3

Quantum theory, or quantum physics, is more generally called quantum mechanics. It is a theory that describes how our world works, especially at very small levels - though ultimately, all of the effects we see at larger levels are due to quantum mechanics.At very small levels, things behave quite differently than what we would expect. For example, there is inherent randomness in our world; and you can't measure certain things precisely - not because our instruments aren't good enough, but because of the inherent properties of our world.

I suggest you check the Wikipedia article on "Introduction to quantum mechanics".