What Does It Mean When Temperature is Absolute?

Temperature, what is it? Is it heat? Or is it Cold? Well, it's both of them.

From childhood, we learned that temperature is the degree of hotness or coldness of an object. This definition is still true. Well kind of. For a fact, the temperature isn't just a degree. It is actually the average energy of all the particles in a system and it's also related to the distribution of those energies in the system. You see, a change in temperature is basically a consequence of heat exchange. This results in a rise or fall in a body's hotness or coldness. So what does it mean when the temperature is said to be absolute?

Absolute - Maximum

If you're thinking it means 0 degrees Kelvin, you are slightly incorrect. That is just a point on the temperature scale. What it actually means is a point where we can go no further. This applies in both directions. So we have what is called Absolute Cold ( better known as absolute zero) and Absolute Hot. 

© From LMU and MPG Munich

Absolute Zero

I believe you're familiar with this particular phrase. Many science fiction movies have made reference to it. One of the most notable being the 2006 movie Absolute Zero (aptly named). Absolute Zero is not just a temperature. It's the coldest temperature possible and is measured to be about -273.15°C (in the Celsius scale), -459.67°F (in the Fahrenheit scale), 0°R ( in the Rankine scale) and 0K (in the Kelvin scale). It is thought by many that matter stops moving at this temperature and there can be no chemical reaction possible. Not to dismiss their thinking or anything but that statement is quite a misconception. 

Matter doesn't stop moving at absolute zero. More precisely, it is a temperature where particles are at their lowest energy point. In the field of Quantum physics, we have what is known as "Zero point energy". Let's recall the Heisenberg Principle of Uncertainty which roughly states that the increased degree of certainty of a particle's property results in the decrease in the degree of certainty in another related property. For instance, once more is known about a particle's momentum, less is known about its position and vice versa ( variations include energy and time). So we can't possibly completely stop a particle because it's position and momentum will be accurately known. Zero point energy follows the same principle. It means that even after all the energy that can be removed from particles has been removed, the particles will still have some energy. So to be more accurate, absolute zero is the temperature at which entropy is at it's minimal.

📷From ZidBits

Absolute Hot

This was postulated to be the highest temperature possible on the absolute scale which started from absolute zero. From calculations, it could be said that the absolute hot temperature is the Planck temperature (named after Max Planck) which has the value of 1.416786 x 10³². Above this temperature, it is thought that the force of gravity would become as strong as the other three fundamental forces ( strong, weak and electromagnetic force) due to the enormous increase in particle energies. Since there's no theory that aptly explains four fundamental forces equal in strength, we simply say physics breaks down at this point. Though the Quantum theory of gravity is a theory believed by many that could explain this phenomenon, we haven't still got a clue what it is. Superstring theory is another but it isn't just as beautiful as the proposed quantum theory of gravity. Absolute hot is just a postulation since we haven't physically measured such a high temperature. Currently, the highest temperature recorded is much closer than you'd to think. It's the Large Hadron Collider (LHC). It is recorded at 10 trillion degrees Fahrenheit! That is such an enormous amount of heat generated but not exchanged as it only occurs for a split second.

Negative?

There's one anomaly when considering temperature. That anomaly is called Negative temperature. Didn't think it was possible? Well, it exists. Don't get it wrong. Negative temperature isn't colder than absolute hot, it is hotter than absolute hot. To be put more accurately, it is hotter than what is defined to be hot. A substance that has a negative temperature is said to be infinitely hot. Now you might ask, "Isn't absolute zero a negative temperature?". It's not. Absolute zero is has a value of 0 on the Kelvin (absolute) scale whereas negative temperatures have negative values on the Kelvin scale. 

📷 BBC

Third Law of Thermodynamics

There is but one limitation when cooling an object to absolute zero. We can't quite get there. You see, the third Law of thermodynamics has an unattainability principle which states that any process cannot reach absolute zero temperature in a finite number of steps within a finite amount of time. Why is it so? Well, there are different explanations for this. A very basic reason is: In order for a body to reach absolute zero, all its energy must be removed and since energy is associated with mass and all matter has mass, it is impossible to remove all its energy. Hence absolute zero is unattainable. Another (although a lot more complex) as explained by Wikipedia is: "Suppose that the temperature of a substance can be reduced in an isentropic process by changing the parameter X from X2 to X1. One can think of a multistage nuclear demagnetization setup where a magnetic field is switched on and off in a controlled way. If there were any entropy difference at absolute zero, T=0 could be reached in a finite number of steps. However, at T=0 there is no entropy difference so an infinite number of steps would be needed".

To put into perspective how temperature increases, here's a list:

At -273.15°C: Absolute zero.

At -273.1499°C: Coldest Bose-Einstein condensate ( Also coldest temperature achieved by man).

At -273.16°C: Water's triple point.

At -196°C: Freezing point of nitrogen.

At -78°C: Freezing point of alcohol.

At 0°C: Freezing point of water (or melting point of ice).

At 4°C: Anomalous expansion of water.

At 25°C: Room temperature.

At 37.5°C: Human body temperature.

At 54°C: Temperature of the atmosphere at Death Valley.

At 99°C: Oven temperature for baking a cake.

At 525°C: Draper Point.

At 1090°C: Temperature of Lava.

At 5500°C: Temperature of the surface of the sun.

At 15million °C: Temperature at the core of the sun.

At 350million °C: Temperature at the center of a nuclear bomb explosion.

At 3billion °C: Supernova.

At 10trillion °C: Temperature during collisions in the Large Hadron Collider (LHC).

At 1.417 x 10³² °C: Planck temperature

📷 By Moses Boyd

Come to think it, we are just about 8 times hotter than absolute zero and 1.417 x 10³² trillion times colder than absolute hot. I guess that makes us all cooler than we really think