doubts and questions on existing theories.

[dripto biswas]

i heard that any object above absolute zero should radiate some form of energy. so, can't a particle's position be pointed at any instant if i place very sensitive radiation detectors all around its path? can't i pinpoint the paritcle's position and velocity at any given instant like this? the detectors are not physically interacting with the particle and therefore can't be responsible for any change in its velocity or position. can anyone please clear my doubt on this topic.

[mathematic]

You need to supply a better description of your thought experiment. What radiation are you assuming?

[Klaynos]

I'd guess black body radiation. To answer the question, no, you would still be limited by the uncertainty principle.

[dripto biswas]

do i really have to mention the radiation? i mean, you guys should more than me about the form of radiation. and may i please ask you HOW i will still be limited if my apparatus is not in physical contact with the particle?

[jasonj]

It doesn't matter what kind of radiation, but any kind of detector has to have a physical connection with any particle stated or reaction of that particle. The fact that it's being observed can change it's direction and function. No tools needed. Uncertainty principle. Even thinking about it will change your results.

[swansont]

i heard that any object above absolute zero should radiate some form of energy. so, can't a particle's position be pointed at any instant if i place very sensitive radiation detectors all around its path? can't i pinpoint the paritcle's position and velocity at any given instant like this? the detectors are not physically interacting with the particle and therefore can't be responsible for any change in its velocity or position. can anyone please clear my doubt on this topic.

 

How would these detectors pinpoint the location to arbitrary accuracy?

[derek w]

i heard that any object above absolute zero should radiate some form of energy. so, can't a particle's position be pointed at any instant if i place very sensitive radiation detectors all around its path? can't i pinpoint the paritcle's position and velocity at any given instant like this? the detectors are not physically interacting with the particle and therefore can't be responsible for any change in its velocity or position. can anyone please clear my doubt on this topic.

It depends on your definition of an object,if your object is a red hot piece of steel then yes it will radiate energy.

[J.C.MacSwell]

Wouldn't it have to be infinitely hot, to radiate at infinite frequency, to be detectable to infinite precision?

[John Cuthber]

When it emits radiation it experiences a recoil force so the most you can know where it was,but not where it is.

[juanrga]

i heard that any object above absolute zero should radiate some form of energy. so, can't a particle's position be pointed at any instant if i place very sensitive radiation detectors all around its path? can't i pinpoint the paritcle's position and velocity at any given instant like this? the detectors are not physically interacting with the particle and therefore can't be responsible for any change in its velocity or position. can anyone please clear my doubt on this topic.

 

Unless I am completely wrong, it seems that you are trying to avoid the uncertainty principle of quantum mechanics, but this is not possible.

 

Heisenberg believed that the uncertainty was the result of our measurements. In fact still some popular presentations of the principle says that we cannot know position and momentum because any measurement introduces a perturbation and changes, for instance, the speed of the quantum object. This is not the real reason. We know today that the principle is unrelated to our measurements. Quantum mechanics says that the quantum object cannot be in some wavefunction with a given position and momentum.

 

Therefore it does not matter if you imagine a detector that does not physically interact with the object. The quantum object continues without having a given position and momentum because the laws of quantum mechanics say that there is not any wavefunction that was at the same time eigenfunction of the position operator and eigenfunction of the momentum operator.

[swansont]

Wouldn't it have to be infinitely hot, to radiate at infinite frequency, to be detectable to infinite precision?

 

You'd also need an infinite number of infinitely small detectors, which is what I was alluding to earlier.

[O'Nero Samuel]

It doesn't matter what kind of radiation, but any kind of detector has to have a physical connection with any particle stated or reaction of that particle. The fact that it's being observed can change it's direction and function. No tools needed. Uncertainty principle. Even thinking about it will change your results.

Even thinking about it would change your result? Then how can you tell that the result has changed when you didn't even know what is was in the first place?

[J.C.MacSwell]

 

You'd also need an infinite number of infinitely small detectors, which is what I was alluding to earlier.

I'll add them to my Christmas list!

[ydoaPs]

Even thinking about it will change your results.

 

No, it won't.

[O'Nero Samuel]

 

No, it won't.

I taught as much. Because one begins to wonder how thinking about the position of a particle interacts with the particle. The Uncertainty principle holds as long as there is a detector, since the detector would have to interact with that particle to detect it. That is the long and short of the whole story, anything added would be unscrupulous detail.

[juanrga]

The Uncertainty principle holds as long as there is a detector, since the detector would have to interact with that particle to detect it.

 

As stated in #10 the uncertainty principle of quantum mechanics holds even in absence of any detector. The principle is really about the quantum state of the particle not about measurements.

Edited December 13, 2012 by juanrga