A Physics Question

[Agayek]

So I was having a discussion with some friends about Absolute Zero(Zero degrees Kelvin), and I commented about how AWESOME it would be to see an atom a 0 degrees kelvin when all motion stopped and the elctrons were suspended in their orbits, and that got me thinking...

Would they be stopped?

At 0K, all energy has ceased, including kinetic energy, so the electrons have ceased moving and all momentum is gone. However electrons, like planets and moons, exist in a balance. The force trying to throw them out(forward momentum) is equal to that trying to pull them in (magnetism and the nuclear forces). So if you stopped the momentum, then the attrative forces would pull the electron in. The electrons fuse with the protons and form neutrons, which would undoubtably release energy, and therefore raise the temperature.

But if the temperature is at 0K, and all energy has ceased, how can there be the kinetic energy for the electrons to move towards the center? Such a movement would generate energy and thus raise the temperature as well.

So, here's the big question, given the nuclear forces involved, is 0 Kelvin an attainable temperture or is it a theoretical construct? And if it is real, what happens to atom chilled to 0 Kelvin?

First and foremost, absolute 0 is impossible when matter is present. There's a whole bunch of fancy reasons for it, but the gist of it is that as long as something exists, it contains some amount of energy (even if that energy is very very small).

From a theoretical standpoint, once an atom reaches absolute 0, and all motion is stopped, there is no more internal force on the electrons. By simple virtue of deductive logic, if the electrons are stopped, then there are no forces acting on them. Thus, once an electron reaches absolute 0, there can be no nuclear forces being exerted.

 

[Karma168]

I like the way my physics teacher in highschool explained it. at absolute zero the pressure exerted by a gas is 0. As the pressure is what creates volume (just by sitting there not moving you exert some pressure) when there is no pressure, there is no volume and matter just stops existing. I know it's really basic but it's quite a nice simplistic model for explaining it to a laymen.

 

[Shifty Tortoise]

I don't understand anything that anybody has written here. You people are smarterer than me

 

[Jamash]

Spoiler: snip

So I was having a discussion with some friends about Absolute Zero(Zero degrees Kelvin), and I commented about how AWESOME it would be to see an atom a 0 degrees kelvin when all motion stopped and the elctrons were suspended in their orbits, and that got me thinking...

Would they be stopped?

At 0K, all energy has ceased, including kinetic energy, so the electrons have ceased moving and all momentum is gone. However electrons, like planets and moons, exist in a balance. The force trying to throw them out(forward momentum) is equal to that trying to pull them in (magnetism and the nuclear forces). So if you stopped the momentum, then the attrative forces would pull the electron in. The electrons fuse with the protons and form neutrons, which would undoubtably release energy, and therefore raise the temperature.

But if the temperature is at 0K, and all energy has ceased, how can there be the kinetic energy for the electrons to move towards the center? Such a movement would generate energy and thus raise the temperature as well.

So, here's the big question, given the nuclear forces involved, is 0 Kelvin an attainable temperture or is it a theoretical construct? And if it is real, what happens to atom chilled to 0 Kelvin?

I saw a Horizon special with Ben Miller that attempted to answer this theoretical question and the results are a sight to behold:


I think that clip could help to answer your question a lot better than I could with words, since although I understand what I watched, I'm not a physics student and couldn't explain it in my own words.

It's from a recent BBC documentary called Horizon: What is One Degree? and it's well worth watching if you get the chance.

 

[Mackinator]

Well if half of the crap scientists have theorised in Physics is true I give up on the world. I done A level physics and the stuff is insane - one of the particles they were trying to force on me was almost certainly disproven at CERN from what they "theorised" so I ignore complcated physics now.

 

[Amphoteric]

Asking what would happen at 0K is like what happened before the Big bang. It is not a coherent question.

You see, that statement feels awfully anti-scientific to me. Science has always been a profession not of "What can we do" but rather "What does that do". Whilst other trades and professions aim to make something useful such as a mechanic or a manufacturer, the very basics of science is looking at what is considered impossible, and find a way to prove it possible. A great example of this is the shape of the earth and its position in the universe-people scoffed back then at the idea that the earth was a sphere, or wasnt in the centre of our galaxy. It was as you said, not a coherent question.

In the world of science, nothing is impossible to try and figure out. Being curious simply allows us to look at something in a different way.

Time didn't exist before the big bang. That is why it isn't a coherent question to ask what happened before it. It is not "anti-scientific" to declare certain things impossible or unknowable.

 

[TiefBlau]

So I was having a discussion with some friends about Absolute Zero(Zero degrees Kelvin), and I commented about how AWESOME it would be to see an atom a 0 degrees kelvin when all motion stopped and the elctrons were suspended in their orbits, and that got me thinking...

Would they be stopped?

At 0K, all energy has ceased, including kinetic energy, so the electrons have ceased moving and all momentum is gone. However electrons, like planets and moons, exist in a balance. The force trying to throw them out(forward momentum) is equal to that trying to pull them in (magnetism and the nuclear forces). So if you stopped the momentum, then the attrative forces would pull the electron in. The electrons fuse with the protons and form neutrons, which would undoubtably release energy, and therefore raise the temperature.

But if the temperature is at 0K, and all energy has ceased, how can there be the kinetic energy for the electrons to move towards the center? Such a movement would generate energy and thus raise the temperature as well.

So, here's the big question, given the nuclear forces involved, is 0 Kelvin an attainable temperture or is it a theoretical construct? And if it is real, what happens to atom chilled to 0 Kelvin?

This idea might be true under the classical model, but in modern physics, particles still move at absolute zero.

Why? Fucked if I know. I swear, physicists are just screwing with us.

 

[Hero in a half shell]

I don't understand anything that anybody has written here. You people are smarterer than me

I agree with you enirely. If anyone needs me I'll be in the corner, crying over a novelty model of a hydrogen atom. *sob*

 

[maddawg IAJI]

It'd be impossible to find out, simply because we've never seen anything at absolute zero. We've seen things in very, very cold temperatures, well below freezing on a normal Celsius scale, but no one has ever achieved it.

 

[nicksdrago0]

Time didn't exist before the big bang. That is why it isn't a coherent question to ask what happened before it. It is not "anti-scientific" to declare certain things impossible or unknowable.

But thats the problem, we can't say something is impossible or unknowable without ironically enough, knowing everything about it. Can we fly without any assistance? Of course not, our bone mass is far to dense and our surface area means we simply can't do it. Was there time before the big bang? We don't know yet. There must have been time for the big bang to occur, but what if time was one of the things the big bang created? 100 years ago, it was "impossible" to fly. As our technology in both finding things and making things improve, our limits of impossibility get smaller and smaller. Simply dismissing a question because the current case is impossible to pull off is, in my view, really anti-scientific.

 

[Tallim]

Electrons aren't actually little balls whizzing around a nucleus

This is probably the most important sentence in this thread.

The models we use to understand the universe are meant to explain certain observable phenomena and do not necessarily correspond with reality.

The model is good enough as you say for the level it's used. I believe we now deal in Probability Density when talking about electrons. But been a long time since I was at Uni and can't remember.

 

[Phishfood]

So I was having a discussion with some friends about Absolute Zero(Zero degrees Kelvin), and I commented about how AWESOME it would be to see an atom a 0 degrees kelvin when all motion stopped and the elctrons were suspended in their orbits, and that got me thinking...

Would they be stopped?

At 0K, all energy has ceased, including kinetic energy, so the electrons have ceased moving and all momentum is gone. However electrons, like planets and moons, exist in a balance. The force trying to throw them out(forward momentum) is equal to that trying to pull them in (magnetism and the nuclear forces). So if you stopped the momentum, then the attrative forces would pull the electron in. The electrons fuse with the protons and form neutrons, which would undoubtably release energy, and therefore raise the temperature.

But if the temperature is at 0K, and all energy has ceased, how can there be the kinetic energy for the electrons to move towards the center? Such a movement would generate energy and thus raise the temperature as well.

So, here's the big question, given the nuclear forces involved, is 0 Kelvin an attainable temperture or is it a theoretical construct? And if it is real, what happens to atom chilled to 0 Kelvin?

There are two answers I can come up with.
1) is that its actually impossible to reduce something to 0K.
2) as the thing approaches 0k and everything slows the electrons pull in gradually. It wouldn't hit 0k and come to a complete stop in an instant.

 

[Jonluw]

I don't see why the electrons should stop moving when the atom hits 0K.
Temperature is a measure of movement between atoms, after all, the electrons do not, to my knowledge, have anything to do with it.

 

[Redingold]

Well if half of the crap scientists have theorised in Physics is true I give up on the world. I done A level physics and the stuff is insane - one of the particles they were trying to force on me was almost certainly disproven at CERN from what they "theorised" so I ignore complcated physics now.

Which particle would that be? You can't just ignore physics because it doesn't fit with your personal philosophy.

 

[Amphoteric]

Time didn't exist before the big bang. That is why it isn't a coherent question to ask what happened before it. It is not "anti-scientific" to declare certain things impossible or unknowable.

But thats the problem, we can't say something is impossible or unknowable without ironically enough, knowing everything about it. Can we fly without any assistance? Of course not, our bone mass is far to dense and our surface area means we simply can't do it. Was there time before the big bang? We don't know yet. There must have been time for the big bang to occur, but what if time was one of the things the big bang created? 100 years ago, it was "impossible" to fly. As our technology in both finding things and making things improve, our limits of impossibility get smaller and smaller. Simply dismissing a question because the current case is impossible to pull off is, in my view, really anti-scientific.

Being able to prove things impossible using maths is not anti-scientific. It has already been proven absolute zero is not possible by thermodynamic means.

Also time is a dimension of space. Therefore before the big bang, there was no space and therefore no time.

 

[Smooth Operator]

I don't see why the electrons should stop moving when the atom hits 0K.
Temperature is a measure of movement between atoms, after all, the electrons do not, to my knowledge, have anything to do with it.

But that would imply a single atom has no temperature - is already at 0K.

Well since 0K is not achievable, I can only offer my half arsed theory:
- temperature is called internal energy because it is the sum of all forces working within a material/atom
- thus zero Kelvin means any and all forces/energy within the atom must be eliminated
- so were we to achieve zero Kelvin subatomic particles would be completely free and completely solid at the same time, imagine a solar system without gravity or movement it all just stops

 

[Durananrananrananran]

Caution: Did science years ago so rusty.

Theoretically, motion would not stop. The system would be at its lowest energy state. There's a simplification, I forget its name, that due to large differences in energy lets you view the wavefunction of a molecule as the sum of different wavefunctions describing individual types of motion. So a molecule at 0K would be in its lowest electronic energy state, lowest rotational state, lowest vibrational state and lowest translational state. Each of the lowest energy states has a non-zero energy, so 0K does not mean no energy.

Your problem here is the "electrons orbiting" idea. Electrons do not orbit the nucleus in the same way that the Earth orbits the sun. Like most of the physics you get taught at school it's a useful way of describing the situation that's actually completely wrong.

If electrons really were moving in little circles around the nucleii they would almost immediately lose their kinetic energy through Bremsstrahlung.

An electron orbital is a probability distribution around the nucleus describing where you are likely to find the electron if you try to measure its position. However - quantum physics being what it is - the electron does not have a definite position until that measurement is made.

I don't think (but I'm not sure on this point) that the shape of the orbital is in any way affected by the temperature of the atom.

Also, as a number of people have pointed out you cannot actually cool something to absolute zero, although you can get pretty close.

(PhD particle physicist - just don't ask me what "outside" looks like)

The shape of the orbital is not affected by temperature.

 

[Owlslayer]

I've also wondered what would happen, and what would it be to see it...
But i find it funny in a weird way that the lowest temperature is -273C, but the highest is-... umm... i dunno.
The bottom limit is near! But where's the top limit? Is there even one? When absolutely everything melts? Atoms vanish? Gah, i have no idea what I'm talking about xD

 

[Durananrananrananran]

I've also wondered what would happen, and what would it be to see it...
But i find it funny in a weird way that the lowest temperature is -273C, but the highest is-... umm... i dunno.
The bottom limit is near! But where's the top limit? Is there even one? When absolutely everything melts? Atoms vanish? Gah, i have no idea what I'm talking about xD

I believe that level is.... over NINE THOUSAND!

 

[Jonluw]

I don't see why the electrons should stop moving when the atom hits 0K.
Temperature is a measure of movement between atoms, after all, the electrons do not, to my knowledge, have anything to do with it.

But that would imply a single atom has no temperature - is already at 0K.

Huh?
The temperature of a single atom would be determined by the speed at which that atom as a whole moves about.

Take, for example, an electric wire. These are made from metal which have the peculiar atomic structure that the nuclei are suspended in a sea of electrons. When you direct a current through this wire, the electrons will move in one direction. The temperature, unless there is significant resistance in the wire, will not rise, i.e. the movement of electrons does not cause temperature to rise in itself. However, if there is resistance in the wire, the electrons will be hitting nuclei on their way through the wire, thereby causeing the nuclei to vibrate from the impact, resulting in a heated wire.