The Zeroth Law of Thermodynamics states:
If two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other.
Liquid-Liquid barrier in Coffee with Creamer
Credit: R.B. Boyer
It’s called the “Zeroth Law” because it was discovered after the other laws, but is more fundamental than them. It’s an algebraic concept, if a=b and b=c, then a=c. A thermometer in a pot of boiling water is a system, and it reaches thermal equilibrium with the boiling water when its temperature reaches 100 degrees celsius.
Our refrigerators are systems, releasing cold into our homes when we open the door. Our homes are systems, releasing heat into the winter air through our windows and walls. The Sun is a system, radiating heat and light energy out into the Universe. We are systems, dispersing heat, work, and electrical energy through our bodies all over the place.
The First Law of Thermodynamics states:
Energy can neither be created nor destroyed. It can only change forms.
Blue Ball Aggregator
Hydrogen atoms fuse into helium atoms in our Sun, releasing a difference in mass as energy according to E=mc2 in the form of light and heat. Phytoplankton convert that light into chemical energy via photosynthesis. The phytoplankton die, fall to the bottom of the ocean, where they are buried and are stored as crude oil, another form of chemical energy. When we burn the oil, that energy is converted into light and heat.
At no point in the process is additional energy added to the system. The energy in the oil is the energy that came from the Sun. With the exception of the tides, which are driven by the gravitational pull of the Sun and Moon, all of the energy on Earth comes from the Sun’s light and heat.
The Second Law of Thermodynamics states:
The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.
Drop an egg and you get a broken egg, but drop a broken egg and you will never get an egg made whole. This is not to say that you cannot turn a scrambled egg back into an egg, as is often asserted, but rather that it would take a great deal of energy to put Humpty Dumpty back together again.
Energy is like this egg. A hot cup of coffee will cool to room temperature because the heat the coffee disperses to equalize with the rest of the room. If you want to make the coffee hot again, you will need to zap it with energy in a microwave oven. The energy used to run the microwave oven is energy dispersed into the coffee, and you can’t put it back together again either.
The Second Law is why you can’t build a perpetual motion machine or a 100-percent efficient engine. Some energy is always dispersed as part of an exchange.
The Third Law of Thermodynamics states:
As temperature approaches absolute zero, the entropy of a system approaches a constant minimum.
Snow By Night
Credit: tricky TM
As the heat disperses into an unusable form within a system, that system approaches a temperature of absolute zero, -273.15° Celsius, or -459.7 Fahrenheit. The key word here being “approaches.” Absolute Zero is unattainable; therefore, it is impossible to remove all the energy from a system.
We are doomed. Eventually the Universe will all wind down and a uniform freeze will pervade everything thanks to the Second Law. But, thanks to the Third Law, the energy won’t be gone, it will have spread so thin as to be unusable.
C.P. Snow best summarized the three laws of Thermodynamics (fourth added posthumously):
- 0. This is the Game: you’re here, you are part of the system
- 1. You Can’t Win: you can’t get more energy out of the system than you put into it.
- 2. You Can’t Break Even: any transfer of energy will result in some waste of energy unless a temperature of absolute zero can be achieved.
- 3. You Can’t Get Out of the Game: you cannot achieve absolute zero.
Stated simply: There’s no such thing as a free lunch.
Note: Creationists argue that the Second Law invalidates the possibility of evolution. Things cannot go from a state of disorder to increasing order, as evolution appears to do. The problem with their arguement is that the Second Law applies to a closed system. The Earth isn’t a closed system, it’s powered by the Sun. Evolution is powered by the Sun, and it’s an extremely wasteful proccess.
Coffee Cup Sterling Engine: