-273.15 Celsius degree!!!!

[tomwalker154]

Hi guys;
I want to find out 2 terms in physics. I don't know how to call them in English. Hope you guys can help.
As I read in a book a long time ago, there are 2 special phenomenons appearing when the temperature reach to -273.15 Celsius degree.
The first phenomenon: there is nothing can move at this temperature --> electricity can transfer without any resistance.
The second one: at the normal condition, liquid (water) falls down if it is dropped but at -273.15 Celsius degree, liquid automatically crawls over the glass and spread out.
Seem so weird, right? :D
Thank you guys!

[Khedrac]

OK - there are three different things here:

Absolute zero (0K or zero degrees Kelvin) is the temperature at which nothing moves (well probably).

Superconductivity is the property of some substances where electricity flows without resistance. A lot of work is going into making ones that work at liquid nitrogen (and warmer) temperatures.

Superliquids have no surface tension and so will flow up the sides of their containers (trying to spread out to one molecule thick).
EDIT: they have re-named this one superfluidity rather than super-liquid.

Note: liquid Helium is where things get interesting.
It's the main one to form a superfluidliquid at a few milli-Kelvin, but there is a form that is theorized to still be liquid at 0K (it only becomes a liquid at a few milli-Kelvin).
Edit: looks like the non-freezing form is Helium 3: (Wikipedia)

[snowblizz]

"Absolute zero" is IIRC the term you are looking for (or just above it). I'm my high-school physics is recalled correctly it's when all atomic movement stops. Basically no heat at all, and heat is atomic movement, or causes it or someting like that.
Since the celcius scale is sort of fidgety for it, the Kelvin scale starts at 0K at absolute zero and only goes up from that.

Not sure about the second one since at least water will be ice since about 273 decgrees celcius earlier.

I do think I roughly know what you talk about, but only vaguely.

[Brother Oni]

Not sure about the second one since at least water will be ice since about 273 decgrees celcius earlier.

It's actually possible to supercool some liquids and gases to below their freezing point since crystallisation requires some impurity or a 'seed' to initiate the process. In the case of water though, the lowest you can cool it to is about -48C before it just freezes anyway.

Here's a cool () video that illustrates the process with bottled water: link.

[snowblizz]

It's actually possible to supercool some liquids and gases to below their freezing point since crystallisation requires some impurity or a 'seed' to initiate the process. In the case of water though, the lowest you can cool it to is about -48C before it just freezes anyway.

Here's a cool () video that illustrates the process with bottled water: link.

I did say "about". The funny thing is I typoed the temp at first to 215, which wouldave bene kinda close taking the possibility of supercool liquids.

But it was the superfluid liquids I was remebering vaguely, I knew there was such a thing, just couldn't recall exactly, but I also had a gut feeling it wasn't necessarily reliant on the temperature being absolute zero. And I was pretty certain water at least was not gonna be it.

[Yora]

"Absolute zero" is IIRC the term you are looking for (or just above it). I'm my high-school physics is recalled correctly it's when all atomic movement stops. Basically no heat at all, and heat is atomic movement, or causes it or someting like that.
Since the celcius scale is sort of fidgety for it, the Kelvin scale starts at 0K at absolute zero and only goes up from that.

OK - there are three different things here:

Absolute zero (0K or zero degress Kelvin) is the temperature at which nothing moves (well probably).

Absolute Zero at 0K is the state of lowest possible movement. Because of the uncertainty principle movement can never fully stop. But when you reached the point where it can't get any lower, you got absolute zero.

[Storm_Of_Snow]

It's actually possible to supercool some liquids and gases to below their freezing point since crystallisation requires some impurity or a 'seed' to initiate the process. In the case of water though, the lowest you can cool it to is about -48C before it just freezes anyway.

Here's a cool () video that illustrates the process with bottled water: link.

The "seeds" are more correctly called nucleation sites, and whatever the fluid is contained in can supply them as well - the fewer sites there are, the fewer/larger the crystals in the structure are (which has massive implications for the material properties).

Personally, I'd like to run an experiment on the ISS with a chamber at a nominal zero pressure, carefully inject a quantity of pure water into the middle and let it sit there until it's radiated enough heat away to solidify, then look at the crystalline structure of the resulting ice block.

[The Great Wyrm]

At "nominal zero" pressure, the water will rapidly boil (until the vapor pressure reaches equilibrium). The walls of the chamber in your experiment would also have to be chilled in some way, or else they would radiate heat back to the water.

[BlueHerring]

OK - there are three different things here:

Absolute zero (0K or zero degrees Kelvin) is the temperature at which nothing moves (well probably).

To elaborate on Yora's statement, at absolute zero, electrons will still orbit their respective atomic nuclei. However, they will only ever be in their ground (lowest energy) state.

[wumpus]

To elaborate on Yora's statement, at absolute zero, electrons will still orbit their respective atomic nuclei. However, they will only ever be in their ground (lowest energy) state.

For values of "orbit" limited to "having angular momentum" and "with an axis on the nucleus*". I'd avoid using the term "orbit" as it implies the electrons have a specific location when you have a very good idea of their angular momentum. Electrons are weird, and that weirdness can really manifest itself (see superfluids) near absolute zero.

* even that might not be right, maybe something based on the moment of inertia?

[Rockphed]

To elaborate on Yora's statement, at absolute zero, electrons will still orbit their respective atomic nuclei. However, they will only ever be in their ground (lowest energy) state.

Unless the substance is superconducting. Then the electrons responsible for superconduction occupy states just beyond the Fermi surface*. Fermi surfaces have varying shapes, but it is my understanding that in general superconductors have spherical Fermi surfaces, thus allowing consistent conduction in all directions. As I understand it, superconduction breaks down when the applied electric field or incident magnetic field induces enough current to move the conduction electrons away from the fermi surface.

*The Fermi Surface identifies the highest energy ground state of electrons in every direction. In conductors, the Fermi surface occurs midway up a state band. In semiconductors and insulators, the Fermi surface occurs between state bands. Doping of semiconductors to move their Fermi surface one way or the other allows them to conduct with either positive or negative charge carriers. Okay, so it is always electrons doing the moving, but if the conduction band is close to full, the Fermi surface seems to move the wrong way when a field is applied.

[Cikomyr]

Isnt Absolute Zero a theoretical impossiblity to achieve? Kind of like the Lightspeed Barrier, you need an ever greater quantity of energy to remove the next tidbit of heat without ever reaching 0?

[Manga Shoggoth]

Isnt Absolute Zero a theoretical impossiblity to achieve? Kind of like the Lightspeed Barrier, you need an ever greater quantity of energy to remove the next tidbit of heat without ever reaching 0?

Well, you can reach the lightspeed barrier - all you need is to have a zero rest mass. Of course, this makes stopping difficult. You end up having to crash into things to stop.

(Actually, there is another way - particles can exceed the speed of light within a medium that gives light a slower speed than in vacuo. You end up getting Cherenkov radiation emitted, which can be quite pretty...)

[Kato]

Well, you can reach the lightspeed barrier - all you need is to have a zero rest mass. Of course, this makes stopping difficult. You end up having to crash into things to stop.

I don't think that's what Cykomyr meant

Yes, if you have mass, you can't reach light speed in vacuum. And I'm not sure if it is actually impossible, I'm willing to agree it is, but so far we've not reached 0K, just something like... 0.0000001K or so, iirc.

[Manga Shoggoth]

I don't think that's what Cykomyr meant

Yes, if you have mass, you can't reach light speed in vacuum. And I'm not sure if it is actually impossible, I'm willing to agree it is, but so far we've not reached 0K, just something like... 0.0000001K or so, iirc.

Oh, I know what he meant. I was just letting my inner pedant out for a while. I quite agree that getting to 2.99792450x10⁸Ms^-1 if you have any mass is impossible. I was a little more interested in the interesting case of Cherenkov radiation.

And according to Wikipedia:

1n June 2015, experimental physicists at Massachusetts Institute of Technology (MIT) have successfully cooled molecules in a gas of sodium potassium to a temperature of 500 nanokelvins, and it is expected to exhibit an exotic state of matter by cooling these molecules a bit further.

...so we're getting there.

[factotum]

The biggest problem with getting to 0K is the laws of thermodynamics, which state that heat flows from hot things to cold things. You would technically therefore need something *colder* than absolute zero to cool something down that far, and since pretty much everything is a solid at that temperature, it's largely impossible to use the standard "evaporate liquid to gas"/condense gas back to liquid" cycle that a typical refrigerator uses. I'd be curious to find out how those MIT guys managed to get something that cold!

[Manga Shoggoth]

I'd be curious to find out how those MIT guys managed to get something that cold!

Believe it or not, lasers.

For this technique, the newly created NaK molecules were exposed to a pair of lasers, the large frequency difference of which exactly matched the energy difference between the molecule’s initial, highly vibrating state, and its lowest possible vibrational state. Through absorption of the low-energy laser, and emission into the high-energy laser beam, the molecules lost all their available vibrational energy.

[Cikomyr]

The biggest problem with getting to 0K is the laws of thermodynamics, which state that heat flows from hot things to cold things. You would technically therefore need something *colder* than absolute zero to cool something down that far, and since pretty much everything is a solid at that temperature, it's largely impossible to use the standard "evaporate liquid to gas"/condense gas back to liquid" cycle that a typical refrigerator uses. I'd be curious to find out how those MIT guys managed to get something that cold!

Probably models.

But yhea, thanks for articulating what I meant.