As most of us know, it is (currently) impossible to attain a temperature of absolute zero. But is it also impossible to attain a *feeling *of absolute zero? Let’s say you have a system very close to absolute zero…3 degrees Kelvin for instance. If you introduce a stiff breeze into the system, does the wind chill make it feel colder? Or does the breeze, which is essentially the movement of molecules, actually heat the system up? If it’s the former case, and it feels colder, is it possible to make it feel colder than absolute zero? If it’s the latter case, and it feels warmer, at what temperature will wind have no effect? (If at higher temperatures the wind makes it feel colder, and and extremely low temperatures the wind makes it feel warmer, there would have to be a value somewhere in the middle where wind has no effect.)
Keep in mind I’m not asking if we can achieve a temperature below absolute zero, just a sensation below absolute zero.
There is no sensation anywhere near absolute zero. The nerves would freeze and die long before they reached that temperature, so I guess the answer to your question is no.
Wind chill is the apparent temperature felt by exposed skin, so the thermometer would read whatever the actual temperature was, the wind would have no effect on it.
In principle, I don’t see why not. Perception of temperature is actually based on the rate of heat loss from the body. This can be used as a proxy for an actual temperature measurement, since, all else being equal, rate of temperature loss to the environment is proportional to the temperature difference from the environment. But of course, all else isn’t always equal, and some factors (such as wind speed) can change the efficiency with which temperature is lost to the environment. So basically what you’re asking is, is it possible to set up a situation where heat would be lost quicker than it would be to a passive absolute zero environment, and the answer to that is almost certainly “yes”: Hook up a heat pipe to a hot object, and you can pump heat out of it very fast indeed.
Assuming a spherical cow (i.e., ignoring FCOD’s point on nerves/feeling), there are (at least) two problems with attaining Absolute Zero in this way.
The first, you mentioned in your OP. If we force a breeze into the system, we are introducing heat into the system. Especially since this system resides in a vacuum.
Heck, when we force light into the system (e.g., to observe Bose Einstein Condensate), we are introducing heat into the system.
The second is that Absolute Zero is the absolute absence of heat. To me, this is as attainable as counting to infinity. IOW, no matter how much heat we remove from the system, how do we know we have removed all of the heat? What if there is some amount of heat present, that our equipment just cannot measure?
I’m pretty sure that at near-absolute-zero, a stiff breeze would do more warming by friction (and probably obscure quantum effects) than it would do cooling. Generally what you’re trying to do to cool things down is to remove all sorts of molecular activity. Near absolute zero, cooling is a pretty subtle thing – they actually shove atoms around using lasers in order to slow them down (simplified to my meager understanding of the technique). So anything as crude as shoving many, many molecules around at high speed would only raise the temperature.
Wind chill does two things. First, evaporation increases when the wind blows. Second, the wind sweeps away warmed air from the surface of the body, increasing heat transfer. At temperatures near absolute zero there wouldn’t be any liquid water to evaporate (I wouldn’t expect there to be significant sublimation at those temperatures, either). The second effect - improved heat transfer - would only come into play if the air (which might be liquid) were colder than the object in question, and at those temperatures how much colder could it be?
BTW, wind can sometimes make you feel hotter. This can happen in very hot, dry weather when sweat evaporates quickly even in still air. If the air temperature is higher than skin temperature there will be a layer of air near the body that’s cooler than the ambient air temperature. Wind will sweep away this layer, increasing the heat transfer from the air to the skin. This is also why, at a given temperature, a convection oven will cook something faster than a conventional oven.
A stiff breeze of what? Near absolute zero, the only atomic thing that might be gaseous is helium. Can you get stiff breezes of electrons, say, and would they remove energy?
I suspect that just about any breeze possible near absolute zero would bring a net gain of energy.
Everyone’s assuming that the body being cooled is also near absolute zero. I do not think this is a good assumption. The very concept of windchill assumes that the system is not in thermal equilibrium: You have a warm object (like a human body) in a cold environment (like outside in Alaska). The windchill is not the temperature at which the object would come into equilibrium if it were allowed to cool off; it’s a measure of the instantaneous heat transfer the object is experiencing right now.
I think Chronos has the right approach–you need to look at the heat flow to compute an effective temperature.
But to be extra nitpicky, temperature is only defined in systems in thermal equilibrium. Once there’s heat flow, temperature is only an approximation. If the system is near equilibrium, the temperature(s) are probably meaningful. But if the system is far from equilibrium, temperature will not be so useful a quantity.
“absolute zero” and “largest heat transfer rate” have almost nothing directly to do with each other.
You could be in a vacuum at absolute zero, and not even feel cold, as a vacuum is a pretty good insulator. Why do you think spacesuits have cooling systems?