Newbie question about quantum physics

[Danilo Boskovic]

So... My question is quite simple. If i took an electron from an atom and put it in th palm of my hand (the electron has absolutely no kinetic or potential energy in this case, its resting), before i close my hand it will be there, but when i close my hand it might not. Am i right?

 

[Obliv]

It depends on the environment that the electron is in. A chaotic environment like your hand in open air would not necessarily assume the electron is in your hand. You should look up the Heisenberg uncertainty principle, for it is fundamental to quantum mechanics. Quantum mechanics forces us to think of an electron as a cloud of probability, with no single point being the only point that it must be. It COULD be anywhere, but there might be a higher probability being in your hand for some reason (my knowledge ends at this reasoning).

 

[Nugatory]

So... My question is quite simple. If i took an electron from an atom and put it in th palm of my hand (the electron has absolutely no kinetic or potential energy in this case, its resting), before i close my hand it will be there, but when i close my hand it might not. Am i right?

It's not really meaningful to say that the electron has no kinetic or potential energy, but I'll assume that by "no kinetic energy" you mean that the electron isn't moving relative to you, and by "no potential energy" you mean that there's no nearby source of electrical fields strong enough to noticeably affect the behavior of a charged object in your hand.

And with that said... no, it is not right. I'd guess that you've heard something about how quantum mechanics says that "things are only there if they're observed" or some such, and you're trying to prevent observation by closing your fist? That's not what quantum mechanics says, and if you search this forum for "conscious observer" you'll find a number of threads discussing what it does say.

 

[Danilo Boskovic]

The "hand" is a representation of a perfect environment, i didnt mean it literally.

 

[Danilo Boskovic]

Yes i am starting to study chemistry but i am interested in physics, therefore my understanding of qm is low. So... My question is not literal. If an electron was standing in one place, in space, without any movement relative to anything, will it stay there after it is observed for the second time (considering that the temperature is absolute zero)

 

[andresB]

If an electron was standing in one place...

That is a big "IF"

QM is just not that way.

 

[Danilo Boskovic]

That is a big "IF"

QM is just not that way.

Yeah i know... I just wondered what it would look like if it was in that state.

 

[Danilo Boskovic]

The thing is all our observations so far are limited to the state we are in and it is impossible for us right now to observe it in an absolute perfect environment therefore everything can be put in question. I mean, yes it works, but is it really the way it is? Would it behave the same way in a galaxy and in empty space whereby it wouldn't be affected by conditions that affect us?

Edit: conditions: speed is one we can't affect on and we know of. But we don't know everything until we realize how does the universe behave (i mean, cmon, we don't even know how do galaxies hold together and not get ripped appart due to unsufficient force to hold it together). So our observations are quite subjective.

Edit 2: even speed can have a big influence considering that we are working with something that is extremely small and easly affected. We observe the environment we live in, not the world around us. Therefore search for reality is kind of pointless unless we find out does the envoroment have influence on observations.

 

[Danilo Boskovic]

I'd love to hear opinions on the post above

 

[PeroK]

I'd love to hear opinions on the post above

It's rambling nonsense. Learn some physics properly.

 

[Danilo Boskovic]

It's rambling nonsense. Learn some physics properly.

Maybe i do not know physics well, but niether you can say that you know everything about the conditions that play part in our existence? I am just kind of more the Einstein type, even though i accept the qm as it is.

 

[andresB]

Yeah i know... I just wondered what it would look like if it was in that state.

there is no such state, that's the point.

 

[Danilo Boskovic]

there is no such state

What do you mean by that? I ment it in a way if an electron would find itself inside blank space outside of a galaxy where it isn't affected by gravity or any other force in any manner. Its hypothetical, yes. But it exist, just not achievable by technology we have today. I was wondering would the physics be the same at that state.

 

[andresB]

What do you mean by that? I ment it in a way if an electron would find itself inside blank space outside of a galaxy where it isn't affected by gravity or any other force in any manner. Its hypothetical, yes. But it exist, just not achievable by technology we have today. I was wondering would the physics be the same at that state.

There is no state where the position of the electron is well determined and the velocity (or momentum) is zero (aka, the momentum is well determined too). That state is just not possible in QM, there is no way of realizing it in laboratory or in the nature.

 

[bhobba]

If an electron was standing in one place, in space, without any movement relative to anything, will it stay there after it is observed for the second time (considering that the temperature is absolute zero)

That's not possible because of the Heisenberg's uncertainty principle it can't handle a well defined momentum (standing means zero momentum) and position (in one place means it has a definite position) at the same time. BTW that's why absolute zero is impossible.

If you are just starting out I would suggest the following rather that the semi historical approach of most books:
http://www.scottaaronson.com/democritus/lec9.html

The usual approach IMHO in many cases leads to confusion.

Thanks
Bill

 

[Danilo Boskovic]

That's not possible because of the Heisenberg's uncertainty principle it can't handle a well defined momentum (standing means zero momentum) and position (in one place means it has a definite position) at the same time. BTW that's why absolute zero is impossible.

If you are just starting out I would suggest the following rather that the semi historical approach of most books:
http://www.scottaaronson.com/democritus/lec9.html

The usual approach IMHO in many cases leads to confusion.

Thanks
Bill

An excellent answer i must say. I thought absolute zero was possible in the scenario, but considering the laws its logical that it isnt, and if it was, my question would make sense. I was thinking on learning QM but currently I am busy with german and my studies in pharmacy, but when i find time, i will buy some books to start with!

 

[Danilo Boskovic]

That's not possible because of the Heisenberg's uncertainty principle it can't handle a well defined momentum (standing means zero momentum) and position (in one place means it has a definite position) at the same time. BTW that's why absolute zero is impossible.

If you are just starting out I would suggest the following rather that the semi historical approach of most books:
http://www.scottaaronson.com/democritus/lec9.html

The usual approach IMHO in many cases leads to confusion.

Thanks
Bill

One more thing. When the particle is defying the absolute 0 by its movement, from where does the energy comes from? What is keeping it moving if no artificial interfeering is involved? This is probably a quite easy question but since i have little knowledge in QM... :D

 

[bhobba]

One more thing. When the particle is defying the absolute 0 by its movement, from where does the energy comes from? What is keeping it moving if no artificial interfeering is involved? This is probably a quite easy question but since i have little knowledge in QM... :D

You are falling into a trap of ascribing properties to an unobserved quantum system - you can't do that.

But as far as movement goes cognate of Newtons first law.

Thanks
Bill

 

[Danilo Boskovic]

You are falling into a trap of ascribing properties to an unobserved quantum system - you can't do that.

But as far as movement goes cognate of Newtons first law.

Thanks
Bill

Ok. Qm is really confusing. I'll start off from the basics but what really interests me now is what happens when we do not observe it. Thanks for the answers.

 

[bhobba]

Ok. Qm is really confusing. I'll start off from the basics but what really interests me now is what happens when we do not observe it.

That parth leads nowhere. The theory is silent on what happening when not observed.

Thanks
Bill

 

[Danilo Boskovic]

That parth leads nowhere. The theory is silent on what happening when not observed.

Thanks
Bill

Than there is more to be discovered. I was thinking on going to physics as my secondary education (after i finish my P.h.D. in a few years). I hope by than we will figure QMs principles out

 

[bhobba]

Than there is more to be discovered. I was thinking on going to physics as my secondary education (after i finish my P.h.D. in a few years). I hope by than we will figure QMs principles out

That's the issue. You think in a theory where the primitive is observation there must be more to it. That's the trap - that path will lead nowhere. Once you shake that progress in understanding QM will be swift and you will laugh at the issues you had before. But until you do you will forever be in a mire of confusion.

Even Einstein, whose attitude to QM is often misrepresented, understood this. He was a champion, as am I, of the ensemble interpretation of QM. He believed QM was a complete and correct theory of ensembles - but like similar ensembles in statistical physics incomplete, in that its an approximation to a deeper theory. As yet we do not know that deeper theory, or, despite Einstein's belief, there is in fact one - nature may simply be like that. In the interim just, as Einstein did, accept that's the way it is. If you don't, you will get nowhere - fast.

Thanks
Bill

 

[Khashishi]

Even in classical mechanics, the position of the electron is uncertain after you put it in your hand, because your body is somewhat conductive, and charges move around. If you stick your hand on a van de Graff generator, the electrons will distribute themselves around your body to minimize repulsion. So some of them will end up in the hairs on your head and cause them to stick up (if you aren't bald).