# Tag Info

2

A small system coupled to a temperature bath will have a well defined temperature (the temperature of the temperature bath), if you do not disturb it out of equilibrium. If a single, isolated particle is considered, things are not that tricky either. You can always consistently assume a temperature of zero (but you gain nothing by doing so). But a small ...

2

Any "system/object" can be in a thermal state and thus will be well described by concepts such as temperature. Talking about things in thermodynamic terms such as temperature express a degree of personal ignorance about the system, in which case you talk about an average or expectation of certain general properties (such as overall energy etc). As an ...

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One definition of temperature is that it is the parameter which determines the distribution of velocities of an ensemble of particles. Note that I refer to an ensemble (a group) of particles. If you truly continue breaking down into smaller and smaller pieces, you no longer have the concept of a distribution and things become tricky. You can actually define ...

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Temperature is a measure of mean kinetic energy. So as long as particles can move, they will have temperature. And yes, quarks do have temperature. The highest man-made temperature was attained in a quark-gluon plasma at LHC in 2012.

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This answer has nothing to do with physics, but I was taught in grade school - and, yes, this was in an actual elementary school text - that the Fahrenheit thermometer was based on the coldest and hottest days in 1714 in Holland where he lived. I have never been able to verify that, so I assume it was false, but the temperatures of zero and 100 do represent ...

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If everything were at zero temperature you probably* would not be able to distinguish between the past and future. Mathematically time would still exist, in the same way that spatial directions still exist on a completely featureless plane, but since it would not be measurable (even if there were something around that could do a measurement!), it is ...

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No. In fact the official definition of the second is: The duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom at absolute zero. So time is still alive and kicking at absolute zero.

2

Your idea does not seem to work if you have two particles at different temperatures. Assume you "stop" one of them but not the other. Then does the time slows down for only one particle and not the other? or how would you explain that?

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Here is a table for various situations: The range ( ignoring dark polar crater) from 122C during the two week dat and at 0 latitude, to -158 at night. They probably did not take the cameras out unless within the range. It may be that the constituent parts of the camera would not work outside that range. Between the maxima and the minima there are ranges ...

1

You are way overthinking this. First, you can start with radiative cooling, but that's not the dominant process. At 65 C, in your workshop, convection cooling is the big dog. The total effect will depend on the shape and size of your container, how good a thermal insulator (or conductor, if you prefer) and even details like airflow. Without knowing these, ...

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You can add Newton's law of cooling in to your model quite easily: So we've said that Newton's Law of cooling tells you that the rate of cooling or temperature change is proportional to the temperature difference. Since your volume is fixed you can just look at this in terms of energy. so your equation for heating power when the power is on is going to be ...

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Assuming we can treat the air in the room as an ideal gas, it will obey the ideal gas equation of state: $$PV = nRT \tag{1}$$ where $n$ is the number of moles of the gas. The question tells us that the pressure is constant, and obviously the volume of the room is constant, so the only things that can vary are $T$ and $n$. The question tells us that $T$ ...

1

You can pump heat from cold objects to hot objects if you pay some more energy (that's what your refrigerator is doing) and that doesn't violate second law of thermodynamics. You should note as you heat object, its thermal radiation will increase. Intensity (that is power per unit surface area) of thermal radiation is proportional to $T^4$ so when the ...

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It is the mass of material more than the thickness that determines the stopping power (which incidentally is a function of energy - so you can't simply state "40 cm reduces gamma flux one billion times" without specifying the energy). Lead has a positive coefficient of thermal expansion - so the same amount of lead will become slightly thinner at colder ...

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Ohm's law assumes the temperature remains constant. An Ohmic conductor is one in which the current flowing through it is proportional to the voltage applied across it. A non-ohmic conductor is one in which the voltage and current are not linear. A) The resistance of most conductors increases as the temperature increases, however being ohmic and not ohmic ...

1

You will get most likely get uneven heating that is hard to reproduce - so I would say "no, that is not a good approach". Using a thermal bath like @BySymmetry suggested is much better - or wrap some resistive wire around it and run a known current through it for a known time. The key to good experiments is control and repeatability - your open fire solution ...

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You are confusing time with the flow of time. Time is just a coordinate like the spatial coordinates, that is we label spacetime points with four coordinates $(t, x, y, z)$. Indeed, in relativity (both flavours) the time and spatial coordinates get mixed up so different observers will disagree about what is time and what is space. But the obvious thing ...

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Fourier number is a measure of heat penetration depth. Together with Biot number it characterizes transient aspect of heat conduction. Characteristic time here is the time it takes for temperature difference between the object and the surrounding to drop to $1 \over e$ (37%) of its value. If initial temperature is $T_0$, and surrounding temperature is ...

1

I hope someone with more knowledge will pop into thread, but here is my education. There might be number of ways to measure such low temperatures. One I find fascinating is starting with material, namely Bose-Einstein condensate. Reference is this one: Cooling Bose-Einstein Condensates Below 500 Picokelvin, Leanhardt et al. Science, 12 September 2003. ...

3

The temperature is not measured in the sense of using a thermometer. Instead it is calculated from the velocities of the particles in the trap. Temperature is related to the velocity distribution by the Maxwell-Boltzmann equation. Under normal circumstances we are usually starting from a known temperature and calculating the velocity distribution. However ...

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Wind chill is really due to two things: 1) colder air moves across the surface of your skin, replacing the air you heated with your body: this in essence takes away the blanket of warm air you keep making for yourself. 2) As your body loses moisture through evaporation, there is a humidity gradient of stagnant vapor around your body. The higher the ...

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The answer is "it depends." Here are some of the factors on which it depends: The thickness of the ice. Ice is a mediocre conductor of heat, about the same as rock. A thick layer of ice somewhat insulates the upper surface of the ice from the ~0 °C water just below the ice. A thin layer of ice, the ice will be at ~0 °C. The average wind speed. Thermal ...

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You would not have ice (at atmospheric pressure) if the temperature was about 0°C. In your situation, the top of the ice is at -10°C and the bottom of the ice is at 0°C. Also, since there is very little water circulation, the bottom of the lake can be over 4°C.

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Newton's law of cooling actually comes from the more general equation for heat $Q$ transferred between a system (temeperature $T$) and it's surroundings(temperature $T_0$): $$\frac{dQ}{dt} = -hA(T-T_0)$$ where $A$ is the area through which heat transfer occurs (see, for example, here). For an ordinary macroscopic object, where $dQ = mc\ dT$, we get the ...

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The gas gets hotter because the energy has no where to go and it must convert into heat. The molecules bounce back and forth with one another creating more and more energy and less space, so the molecules began to compress through the helical rotors.

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Yes, it can measure the temperature of a gas. You can see this for yourself by hanging a thermometer by a string in the air.

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