18 replies to this topic

[Ruben]

Ok, a bit confusing seeing that is contradicting common sense. For example, the famous saying: "If a tree falls in a forest, and there is no one there to hear it, does it make a sound?" Well, according to common sense, and logic we think: yes, of course it does; but Quantum Theory says no. Quantum Theory says that something does not exist, if it is not being looked at, but because the human body has thousands of atoms, we could never loose our body. Wait! That doesn't even make sense. Really, scientifically that does make sense. But going back to if something is not looked at, it doesn't exist, well... How is that possible. They even have a theory on that on how the world was created. It doesn't make too much sense to me, so can anyone explain better?

[rvalkass]

Ruben, on Dec 7 2008, 06:05 AM, said:

Ok, a bit confusing seeing that is contradicting common sense. For example, the famous saying: "If a tree falls in a forest, and there is no one there to hear it, does it make a sound?" Well, according to common sense, and logic we think: yes, of course it does; but Quantum Theory says no.

Quantum theory is generally concerned with events on a sub-atomic level, rather than at the 'human' scale. This was one thing that the Schrodinger's cat thought experiment set out to show - quantum mechanics makes very little sense on a macroscopic scale.

Ruben, on Dec 7 2008, 06:05 AM, said:

Quantum Theory says that something does not exist, if it is not being looked at,

Quantum theory, and the uncertainty principle, actually say the following: before you observe a property of an object, you can only determine the probability of that property having certain values. This takes the form of a wavefunction. When the object is observed, and the property measured, the wavefunction 'collapses' and the property takes the measured value. However, the uncertainty principle says that, for certain pairs of properties, they can never be measured precisely (for example, if you know the velocity of an object absolutely precisely then it must occupy all space). The object still exists, you just cannot determine any of its properties to an arbitrary precision.

[Lightning73]

Exactly what rvalkass said, another example was if you had two boxes each containing a glove, you wouldn't be able to tell which contained the left-handed or right-handed until you opened the box right? Now in Quantum Theory, the gloves are neither until you open the box.

I love this theory, although it's quite hard to understand it for some people. My math teacher actually told me about this. I really hope that someday this theory will be either solved or busted.

[asdftheking]

After reading these posts I still don't understand what is the idea of the quantum theory. Is there any way to put it in a nutshell, or at least just explain key points. Gloves, boxes, and sub-atomic particles, huh?

[Lightning73]

asdftheking, on Dec 9 2008, 06:19 AM, said:

After reading these posts I still don't understand what is the idea of the quantum theory. Is there any way to put it in a nutshell, or at least just explain key points. Gloves, boxes, and sub-atomic particles, huh?

You should read this part about Quantum theory on wikipedia: http://en.wikipedia.org/wiki/Introduction_...antum_mechanics

[rvalkass]

Quantum mechanics deals with phenomena on the scale of atoms (and smaller) rather than on a 'human' scale. It contains other theories like the uncertainty principle, Schrodinger's equation, the Pauli exclusion principle and quantum entanglement. All these are things that don't really appear to affect you on a human scale, but have a great effect on sub-atomic particles (ie. the particles that make up atoms).

[inertialFate]

Hasnt the quantum theory got something to do with quantum physics?

[asdftheking]

Lightning73, on Dec 9 2008, 03:04 AM, said:

You should read this part about Quantum theory on wikipedia: http://en.wikipedia.org/wiki/Introduction_...antum_mechanics

Ok, thanks. I'll look at the article.

[Unknown_99]

(for example, if you know the velocity of an object absolutely precisely then it must occupy all space)

rvalkass, could you explain what the above is in english? I mean, in simpler terms that commoners like me would understand?

[rvalkass]

Unknown_99, on Dec 11 2008, 05:24 AM, said:

(for example, if you know the velocity of an object absolutely precisely then it must occupy all space)

rvalkass, could you explain what the above is in english? I mean, in simpler terms that commoners like me would understand?

Part of quantum physics is the Heisenberg Uncertainty Principle. This states that there are certain properties of an object you can never know more precisely than a certain value. The most common form of this is the following formula:



Where Delta X is the uncertainty in the position of the object and Delta P is the uncertainty in its momentum (its mass times its velocity). The h-bar over 2 is the certain value which sets the maximum precision you can know these values to.

If the uncertainty in its position becomes 0 (ie. you know exactly where it is) then the uncertainty in its momentum must go to infinity, so it would be travelling infinitely fast with infinite mass. Similarly, if you know its velocity precisely, the the uncertainty in momentum becomes 0, so its position becomes infinite.