Absolute Zero and Time

The Free Man

I was talking to a lecturer today about absolute zero, and he said the lowest temperature anybody has achieved in a lab is within 1 millionth of a Kelvin above 0K.
This got me wondering about if time stops at absolute zero, so i checked out some sites about it. They all said that there is still movement of particles at 0K.
How can they know this if they have never witnessed matter at 0K?
Even the coldest place we've found in the galaxy is 1K.
http://www.esa.int/esaSC/SEMX2ES1VED_index_0.html
Is there anywhere in space at absolute zero?

I am thinking that to reach absolute zero is impossible as we would look at it, in the same way that achieving the speed of light is impossible. But i would love to know if time could be stopped in matter this way.

If anybody knows of any resources that look into this more, please post your ideas.

Civilian_Target

There is no such thing as 0K. There cannot be, the uncertaintly principle won't allow it. All matter with temperature is made of particles, and the temperature is given due to particle vibrational and rotation energies. To get a temperature of 0K, this would mean particles would have to have a momentum of 0, and with a momentum of 0 their position will be uncertain, so 0 K is an impossibity.

Easygainer

Civilian_Target wrote:

There is no such thing as 0K. There cannot be, the uncertaintly principle won't allow it. All matter with temperature is made of particles, and the temperature is given due to particle vibrational and rotation energies. To get a temperature of 0K, this would mean particles would have to have a momentum of 0, and with a momentum of 0 their position will be uncertain, so 0 K is an impossibity.

Could it not be achieved without observation, which would be the only feasible circumstance in which it could happen - ie when the Universe has expanded indefinitely to the point that there is no energy left? That is, in theory it could only occur then...

Son Goku

No, you still couldn't get 0K.

Basically a zero kelvin particle can't exist because, as said before it's momentum would be definite, therefore it would be spread over the whole universe.

Which at first seems like it might happen, except there is some monotonous mathematics that doesn't really allow it.

(A state whose position is completely ill-defined will have a proper length of the Dirac-Delta function, states like this don't fit into the Schrodinger equation, Quantum Mechanics prohibits them.)

Essentially the particle can't ever have totally uncertain position, so it can't have totally certain momentum, which means it can't be at 0K.

You'd probably have a lot of trouble trying to get it to reach 0k anyway as everything pretty much stops, no?

Easygainer

Son Goku wrote:

No, you still couldn't get 0K.

Basically a zero kelvin particle can't exist because, as said before it's momentum would be definite, therefore it would be spread over the whole universe.

Which at first seems like it might happen, except there is some monotonous mathematics that doesn't really allow it.

(A state whose position is completely ill-defined will have a proper length of the Dirac-Delta function, states like this don't fit into the Schrodinger equation, Quantum Mechanics prohibits them.)

Essentially the particle can't ever have totally uncertain position, so it can't have totally certain momentum, which means it can't be at 0K.

OK... got a link to an article about it? (not the monotonous maths though )

Civilian_Target

http://en.wikipedia.org/wiki/Laser_cooling

In fact, the current lowest acheiveable temperature of most atoms is limited by an effect called Doppler Broadening (lowest temperature due to the uncertainty principle is called Natural Broadening) however, in some cases the use of inert-gas lasers can be used to overcome the doppler shift effects and allow more cooling. But at the end of the day, so long as the uncertainty principle, which states that

p x > h/2π (p = momentum = mass x velocity, x = position, h = Plank's const)

and if you want to reach absolute zero ( 0 K ) you must achieve a particle velocity of 0, which means the momentum will also be zero, but in doing this you're saying

position * 0 > constant

which means the position cannot be defined. So absolute zero can never be achieved.

Civilian_Target

Also - http://en.wikipedia.org/wiki/Absolute_zero

The Free Man

thanks for the info guys, i'm going to look into this further.

Gurgle

The Free Man wrote:

I am thinking that to reach absolute zero is impossible as we would look at it, in the same way that achieving the speed of light is impossible.

Nah, Absolute zero would be common if you go far enough from a galaxy. Its just the total absence of energy. Can't be measured though because the act of measuring it would introduce energy.

Speed of light is a different thing entirely, which will be achieved within a couple of hundred years when we find a way around the inconvenient quantum effects

Son Goku

Speed of light is a different thing entirely, which will be achieved within a couple of hundred years when we find a way around the inconvenient quantum effects

Quantum Mechanics has absolutely nothing to do with why we can't travel faster than light. We can't exceed lightspeed because of the way spacetime itself is structured, which comes from special relativity not quantum mechanics.

Nothing in the entire universe has ever been observed to move faster than light and all evidence points against it, so I doubt we'll have done it in a few hundred years.

Gurgle

Son Goku wrote:

Nothing in the entire universe has ever been observed to move faster than light

Exactly, how could we observe such a thing?
The medium through which we would observe it is light.

Son Goku wrote:

and all evidence points against it, so I doubt we'll have done it in a few hundred years.

Evidence schmevidence.
Its 104 years since the first powered flight, the PC I'm typing this on was sci-fi when Einstein was around.

Son Goku

Exactly, how could we observe such a thing?
The medium through which we would observe it is light.

?!
Light would still refract of something moving faster than itself. It is capable of approaching at angle. I don't understand how the fact that we use light itself to observe things having anything to do with us no observing superluminal movement.

Evidence schmevidence.
Its 104 years since the first powered flight, the PC I'm typing this on was sci-fi when Einstein was around.

The principle isn't the same.
Flight was considered impossible, due to what were, then, insurmountable practical problems, not because it was ruled out by the universe itself.
Similarly a PC is an application of Boolean logic, which has existed since 1850, it was considered impossible to construct a Turing Machine of a PC's scale for practical reasons.

The speed of light is prohibited by the laws that allow objects to agree on the laws of physics regardless of their motion.
Make the speed of light breakable and that agreement and universality of rules breaks down. Our evidence that light speed can't be broken comes from this Lorentz invariance of the laws of physics.
We also have evidence in the form of mass-energy conservation.

When we say the speed of light can't be exceeded it is because all observers see light moving at 300,000 km/s always and can only observe others approach it.

Relativity rewrites what it means to move faster than something else.
The speed of light is more than some speed limit that can't be broken because something stops you. It can't be broken because it wouldn't make any sense due to the geometry of spacetime.

For instance you can reach somewhere infinitely fast and you still won't exceed the speed of light.

Gurgle

Son Goku wrote:

For instance you can reach somewhere infinitely fast and you still won't exceed the speed of light.

Yep, I just spent the last hour reading up on special relativity and I was coming back to ask that question.

You're really smart.

So a particle/mass/whatever can't in its own frame of reference move faster than light, but could hypothetically get somewhere faster than light would due to time dilation?

Why don't photons experience time dilation?
(or do they?)

Son Goku

So a particle/mass/whatever can't in its own frame of reference move faster than light, but could hypothetically get somewhere faster than light would due to time dilation?

Let's say you take a trip to Alpha Centauri which is 4.3 light years away.
If blast you off to there at 99.999% of the speed of light that distance will only look like 0.2 light years and only take about two months.
From earth's point of view though it took you 4.4 years, so you didn't break the speed of light.*

So you can travel 4.3 light years in two months, because of time dilation.

(*You also don't break the speed of light in your own frame because of the fact that distances all got smaller. In your frame you only did 0.2 light years in two months)

Why don't photons experience time dilation?

In a way they experience infinite time dilation. The whole universe passes by instantly for them.

Chucky

Does it make sense to say that wherever there is a wave (Light, Infra-Red, Micro, etc.) then Absolte Zero will be an impossibility?

Now, considering that we are permanently being bombarded by waves of all sorts including those originating from the 'Big Bang', then for us to achieve absolute zero is not going to happen.

Furthermore (This is a long shot), doesn't all matter decay? Therefore, once all the stars have used their fuel and all matter has decayed won't 'everything' then be in a state of Absolute Zero?

...or is Absolute Zero just another figment of our powerful imaginations

Civilian_Target

Nope - you don't even need a wave. The uncertainty principle means you can never actually measure a particle to zero momentum, so you can never observe or use absolute zero, so it's existance is pretty irrelevant: if it does exist you'll never know. In much the same way that trees cry when no-one is watching them.

Chucky

I hear that and indeed agree with it. However, there are things that fill me with doubt about the laws of Physics that have been devised in the past thousand years. The two most notable things are 'Dark Matter' and the 'Singularity'. Now, when I hear reputed scientists saying that the "laws of Physics break down" at the site of a singularity you cannot blame me for second-guessing all of the laws that humans have devised.

That leads me to Dark Matter which apparently fills 99% of the universe. Wow!, certainly a lot of matter there but we don't actually know it exists. Perhaps our laws of physics have already 'broken-down' and we're adding a lie to a lie by searching for dark matter.

Opinions...please!

Civilian_Target

Quantum mechanics has yet to be broken down. The first law of Quantum Mechanics is that it cannot break down. Newtonian/Relatavistic physics breaks down all the time, as does the standard model.

Remember that current physical descriptions are only the best approximation we can come up with of what's out there. There's always a better approximation...

Son Goku

Chucky wrote:

I hear that and indeed agree with it. However, there are things that fill me with doubt about the laws of Physics that have been devised in the past thousand years. The two most notable things are 'Dark Matter' and the 'Singularity'. Now, when I hear reputed scientists saying that the "laws of Physics break down" at the site of a singularity you cannot blame me for second-guessing all of the laws that humans have devised.

That leads me to Dark Matter which apparently fills 99% of the universe. Wow!, certainly a lot of matter there but we don't actually know it exists. Perhaps our laws of physics have already 'broken-down' and we're adding a lie to a lie by searching for dark matter.

Opinions...please!

I understand the sentiment, but you have to appreciate that the standard model of particle interactions, which is a combination of the two most successful Quantum Field Theories (electroweak and QCD), literally explains every single subatomic phenomena.
In fact the only thing which it doesn't explain is gravity, which is explained by another theory called General Relativity.

Dark Matter is a term coined for the material which exists in halos around galaxies and effects their rotation and there is observational evidence for it, a good deal of observational evidence.

Singularities have never been observed at all, they simple refer to points where General Relativity says that it gives over to another theory of gravity. However these points only occur in such extreme conditions that we have never witnessed them.

So you see our laws actually account for all observed phenomena(excluding emergent things, but that is a computational problem). A current problem in physics is that we have no evidence of something our laws can't explain.

Chucky

Good points by both of you and you have provided me with new angles to look at it having showed disdain to Physics for so long, haha! It leads me to another thing though.

Civilian_Target, you said that:

"Remember that current physical descriptions are only the best approximation we can come up with of what's out there. There's always a better approximation..."

Now, wasn't there some French scientist in the past who claimed that everything in life could be defined mathematically? He was lambasted by his fellows but to me the trend in physics and chemistry shown over the past millenium would surely show that we are working towards that: Defining life and everything in it mathematically.

Obviously that would suggest that there is no true 'free will' and that the future of everything could be predicted mathematically. People obviously didn't like that thought. It's what I believe though - No free will.

planck2

the Nernst formulation of the 3rd law of thermodynamics says that absolute zero cannot be reached in a finite number of steps and yes things still move at close to absolute zero, but I can't remember why exactly. I remember reading something by Landau on the matter

amen

sort of off topic but

Nothing in the entire universe has ever been observed to move faster than light

isn't really true
early expansion of the universe appears to break c if only for a very short period of time

also there is something about splitting electron spin pairs and if you change the state of one the other know straight away irrespective of distance

Spear

amen wrote:

sort of off topic but


isn't really true
early expansion of the universe appears to break c if only for a very short period of time

also there is something about splitting electron spin pairs and if you change the state of one the other know straight away irrespective of distance

But that's space itself expanding, not mass moving above c.

The last part is known as the EPR (Einstein Podalsky Rosenberg) Paradox, sometimes referred to as spooky links.

Son Goku

amen wrote:

sort of off topic but


isn't really true
early expansion of the universe appears to break c if only for a very short period of time

also there is something about splitting electron spin pairs and if you change the state of one the other know straight away irrespective of distance

The early expansion of the universe doesn't exceed c as no material actually propagated through space faster than c.
It was simply an altering of the universe's "distance field" or metric.

also there is something about splitting electron spin pairs and if you change the state of one the other know straight away irrespective of distance

Again there is no "thing" here moving faster than light. All we can say is that a systems wavefunction is consistent non-locally.

Civilian_Target

Spear wrote:

The last part is known as the EPR (Einstein Podalsky Rosenberg) Paradox, sometimes referred to as spooky links.

In the EPR, information does not propogate at a speed faster than c, so relativity is not broken.