Entropy is so often abused by creationists. The claim they make is usally something like this:
"The Second Law states that the entropy always goes up! That means the disorder of a system will always go up! But evolution states that systems (populations or individuals, I can never tell what their 'system' is defined as) become more organised! This contradicts the Second Law, so evolution is wrong."
So I'm going to show you a system where the entropy goes down.
Let's take a block of iron. And we heat it up, really, really hot.
Now, to begin with, this block of iron is isolated from the rest of the universe. But then I attach a tiny, tiny bit of wire from this stupidly hot block of iron, to another really huge block of iron - but at a much lower temperature.
A small amount of heat, dq, will leave the hot block of iron, and enter the cold block of iron. This is so small it is reversible so we can use the equation:
dS = dQ/T
where dS is a small change in the entropy, and dQ is a small change in the heat in the system. And T is the temperature.
What is the entropy change of the hot block of iron?
Well dQ is so small that T has not changed. dQ, you will also notice, is negative, as it has left the system - the heat has gone down. And that means dS - the change in the entropy - is also negative.
In other words, contrary to creationist assertions, the entropy of a system does not always increase.
If we were to consider the entropy change in the cold block of iron, we would find that the entropy change would be positive, and would at the very least cancel out the negative entropy change in the hot block of iron.
The entropy of a closed system tends to increase (statistically speaking), and that is what the second law actually says. A closed system is one that is thermally isolated - no energy enters or leaves the system.An example would be the combined hot block of iron and cold block of iron system I described above, and that is why we find the entropy of that closed system increases. Energy might go between the two blocks, but it doesn't leave (or enter) the system.
This is important. It is important because the Earth is not a closed system. Populations of animals are not closed systems. Individual animals are not closed systems.
They are not closed systems because animals are constantly losing and gaining energy to and from the environment. The environment is constantly radiating energy into space, and recieving energy again from the sun - a great big fusion reactor sat around eight light-minutes from us.
So, because none of these systems (the Earth, populations of animals or individual animals) are closed, none will necessarily tend to have an increase in entropy.
"The Second Law states that the entropy always goes up! That means the disorder of a system will always go up! But evolution states that systems (populations or individuals, I can never tell what their 'system' is defined as) become more organised! This contradicts the Second Law, so evolution is wrong."
So I'm going to show you a system where the entropy goes down.
Let's take a block of iron. And we heat it up, really, really hot.
Now, to begin with, this block of iron is isolated from the rest of the universe. But then I attach a tiny, tiny bit of wire from this stupidly hot block of iron, to another really huge block of iron - but at a much lower temperature.
A small amount of heat, dq, will leave the hot block of iron, and enter the cold block of iron. This is so small it is reversible so we can use the equation:
dS = dQ/T
where dS is a small change in the entropy, and dQ is a small change in the heat in the system. And T is the temperature.
What is the entropy change of the hot block of iron?
Well dQ is so small that T has not changed. dQ, you will also notice, is negative, as it has left the system - the heat has gone down. And that means dS - the change in the entropy - is also negative.
In other words, contrary to creationist assertions, the entropy of a system does not always increase.
If we were to consider the entropy change in the cold block of iron, we would find that the entropy change would be positive, and would at the very least cancel out the negative entropy change in the hot block of iron.
The entropy of a closed system tends to increase (statistically speaking), and that is what the second law actually says. A closed system is one that is thermally isolated - no energy enters or leaves the system.An example would be the combined hot block of iron and cold block of iron system I described above, and that is why we find the entropy of that closed system increases. Energy might go between the two blocks, but it doesn't leave (or enter) the system.
This is important. It is important because the Earth is not a closed system. Populations of animals are not closed systems. Individual animals are not closed systems.
They are not closed systems because animals are constantly losing and gaining energy to and from the environment. The environment is constantly radiating energy into space, and recieving energy again from the sun - a great big fusion reactor sat around eight light-minutes from us.
So, because none of these systems (the Earth, populations of animals or individual animals) are closed, none will necessarily tend to have an increase in entropy.