Quantum Theory

[Ruben 0]

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 5]

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.

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 0]

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 1]

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 0]

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://forums.xisto.com/no_longer_exists/

[rvalkass 5]

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 0]

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

[asdftheking 1]

 

You should read this part about Quantum theory on wikipedia: http://forums.xisto.com/no_longer_exists/

 

 

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

[Unknown_99 0]

(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 5]

(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.

[xenador 0]

It contains other theories like the uncertainty principle, Schrodinger's equation, the Pauli exclusion principle and quantum entanglement.

so I just got done with a college intro corse to chem so I will attempt to explain this, granted I dont have extensive knowledge on any of it.

uncertainty principle in short says you can not know something about a system without interfering with the system itself...due to effects of attraction repulsion you have on the system. Great example of this electrons, we know how many there are due to atom smashers but we can never know where they are because of how fast they move and the fact that by looking at the atom we would be manipulating the "operations" of the system.

Schrodinger's equation- states that S(entropy of a system) = k(shrodinger's constant...or the gas constant diveded by avogadro's constant R/N)log W(number of microstates possible, generally extremely large numbers, and generally extremely hard to calculate...save exceptions), another easier way of restating this is .... ΔS = nCp(or Cv)ln(T2/ T1) that is....the change in entropy is equal to the number of moles times the Constant pressure or volume times the natural log of the first temperature over the second. This is used in the lab setting a lot more.

Pauli exclusion principle- we only discussed this in terms of electrons. Basically no two electrons of an atom are alike...there are 4 different break downs on how to classify an electron.

quantum entanglement- we brushed over this one quite quickly, basically at some point you fail to be able to describe one system without mention of its counterpart because how they are entangled together.

hopefully that helps out a bit.

[onkarnath2001 0]

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?

but i want to ask that if a tree falls down there the potential energy is changed into sound,,if the sound doesn't come out then where the potential energy will go.as i know,"energy can neither be created nor be destroyed"then how can one believe on the classical physics.as quantum mechanics is applied in case of very small entities,,,but can it be applied in case of a bigger tree?????plz do reply

[Watermonkey 0]

I think that's the point of the exercise, though people should probably refrain from using common references to illustrate how it works. For example, the tree falling thing really can't relate to the discussion at hand because it's viewed and heard (or not) on a macro scale, our scale. Because the tree falls in our universe, it must obey the rules therein including the consequence of releasing mechanical energy upon impact with a solid surface, and weather or not a pair of ears is nearby to record this event is not relevant to it happening. Quantum theory really doesn't have anything useful to say about this theoretical scenario because its universe is mostly sub-atomic. The two must be separated, though perhaps at some point someone will finally come up with the string theory to explain it all and tie it all together in a nice simple package.... Not holding my breath.

[shadowx 0]

I am somewhat aware of the theory of observation, however i understand it to mean that an atom, or subatomic particle is in ALL states and ALL places until observed. An electron for example is widely taught to be orbiting the nucleus of an atom much like the moon around the earth, but in fact it does not orbit it at all. It simply pops in and out of existence. Its like hydrogen, with one electron. If you looked at it you would see many electrons, all around it, flashing into and out of existence, all the time. That one electron can be in more than one place at one time, and no places. It is completely separate from time itself, so it seems.This all goes back to Schroedinger's cat (wikipedia it). Whether or not this is true is a different matter. It's a well established theory, and much of quantum physics/mechanics makes no sense to most of us, but at the moment it is just a theory. It does have evidence from the double slit experiment (very interesting, wiki that if you like to be amazed and confused... 1 photon splitting into 2? and yet if you watch it to try to see it splitting it doesnt split...WTF?!).RE the tree in the forest riddle, it depends how you define sound.... If you define sound as something you hear then indeed, there is no sound for no-one is there to be able to hear it. However, if you define sound as a vibration then yes, it does make a sound for the energy is turned into vibration in the earth and air. In the same way a deaf person touching the ground would feel the "sound". But like watermonkey said, that's largely irrelevant when we are talking on the quantum scale.This is a scale where two subatomic particles can be entangled, and held miles, or lightyears apart and yet still communicate with each other (spin one particle left-right and the other will automatically change its spin to up-down, no matter of distance of obstacles between them...)

[anwiii 17]

i think shadowx has explained it the best in layman's terms.i for one though don't believe in the theories. i mean, how would one define measurment in human terms or terms of science.an object isn't an "object" until it is measured. this may be true in the physical sense and any human trying to discover the unknown, but an object will always be an object once it's converted with the energy that converts it as it's instantly measured by the energy that converts it.... even when it's still unknown to any human ability to try to define the unknown.someone mentioned about many universes created when the more likely is the many planes of existance. science and theories will never be able to explain those existances fully which means the theories discredit it's own self in some sense.all quantum theory proves is that we have a long way to go before we know the answersso maybe shakespeare said it best...."to be, or not to be..."....that's really the question here....and understanding exactly what that means.....a tree falling in the woods where nobody is around to hear the sound. sound is directly related to communication and understanding what the sound means. not with human ears specifically, but with the energy that surounds it. so the real question should be....what was the tree trying to communicate before it fell....not after it fell. something that human ears will still fail in comprehending the true answer.all quatum physics or theory is.....is when you look at something, that something changes it's existence or molecular structure. but it goes beyond that of sight and sound of human abilities.there are many theories behind "quantum physics". the simple explaination in what is is is that "objects" no matter how small, are ever changing with no pure definition.this is the same science that will disprove god and god's existance as god and the enrgy that surounds god is ever changing. even though i am not religious, i will use god as an example. and the fact that most people believe that god is all knowing, how can he be when quantum physics will prove god is ever changing with every single piece of energy behind everybody's thought(energy) about god and his/hers existance. so in fact behind quantum theory, there will be no definition of god or "thing" since everyone is always changing with no stop to the "truth" as there are many truths to quantum theories. this will always negate the fact that there is only one truth that cannot be changed.so what is quantum theory? you might as well try to make up a theory of your own. it will go well with all the other theories of life's existance as we know it. why? because as of right now, nobody knows and any theory is a possibility and no different from the rest. that is quantum theory at it's finest. an idea to try and explain the existance of all matter.sorry, i really am not an expert at these theories.....i just typed random thoughts on this subject. when it boils down to it, i don't know ***....let's move on.....