Absolute Zero And Thermal Energy

Absolute Zero: The coldest theoretical temperature but also unachievable according to the third law of thermodynamics.

Absolute zero is a temperature. To understand how cold absolute zero is let's start with the temperature at which water freezes, which is 32 degrees Fahrenheit (0 Celsius). The coldest temperature ever recorded in Alaska was -80 Fahrenheit and the coldest temperature ever recorded on earth was -129 Fahrenheit in 1983 in the Antarctic. Absolute zero is -459.67 Fahrenheit. Humans have been able to come within a billionth of one degree Kelvin to absolute zero!

The coldest natural temperatures reached are in outerspace with the depths of space reaching just -454 Fahrenheit. Humans can do much better, reaching just a few hundred billionths of a degree above absolute zero (Kelvin scale). On the Kelvin scale absolute zero is 0 Kelvin.

What happens at this temperature?
Scientists predict what theoretically will happen at this temperature because it can't ever be achieved. The third law of thermodynamics forbids that humans should ever be able to reach that temperature. As we mentined before, thermal energy is the kinetic energy of the oscillation, vibration, and random activity of atoms and their constituent particles. As an object gets colder, its atoms and molecules begin to move slower and slower. Before we move on it is important to note that the way something is made colder is by heat (thermal energy) being removed, not "coldness" being introduced into the object.

Theoretically, at absolute zero all motion of the atom and its constinuent parts would cease. All thermal energy that could be, would be extracted from the atom. This presents an interesing perspective on time. If all motion would ceases then time would effectively cease also. If there is no time then how could you have space? (cue freaky twilight zone music)

What is thermal energy ?

The ultimate source of thermal energy available to mankind is the sun, the huge thermo-nuclear furnace that supplies the earth with the heat and light that are essential to life. The nuclear fusion in the sun increases the sun's thermal energy. Once the thermal energy leaves the sun (in the form of radiation) it is called heat. Heat is thermal energy in transfer. Thermal energy is part of the overall internal energy of a system. Read about the physics of thermal energy

  

At a more basic level, thermal energy comes from the movement of atoms and molecules in matter. It is a form of kinetic energy produced from the random movements of those molecules. Thermal energy of a system can be increased or decreased.
           

 

When you put your hand over a hot stove you can feel the heat. You are feeling thermal energy in transfer, otherwise known as heat. The atoms and molecules in the metal of the burner are moving very rapidly because the electrical energy from the wall outlet has increased the thermal energy in the burner. We all know what happens when we rub our hands together. Our mechanical energy increases the thermal energy content of the atoms in our hands and skin. We then feel the consequence of this - heat. Laws of Thermodynamics

 

On the left you can see 3 hypothetical thermodynamic systems. I've labeled system C as air for simplicity and the other systems could be anything really. We'll pretend they are solid objects though, two pieces of round iron. One is cold, one is hot. The air we'll make a temperature the same as system A. Instantaneously we put all three into a sealed box. Technically the the box now becomes System D but for simplicity we will leave it out.
 

By convection and radiation the fast moving atoms of system B impact the movement of the atoms of the air. So the transfer of thermal energy begins. As the air "heats up" the faster moving air atoms and molecules now start hitting the thermodynamic boundary of system B and transfering that energy (thermal energy). All this will occur spontaneously until an equilibrium temperature is reached among all 3 systems. What is the lowest that the equilibrium temperature can be? Can it reach Absolute Zero?