Thursday, August 25, 2011

The 2nd Law of Thermodynamics

The Second Law of Thermodynamics states the following:

  • The entropy in a closed system always increases.
  • The amount of unusable energy in a closed system increases.
  • It is impossible to turn all of the heat put into a system into work so that you can’t make a 100% efficient engine.

The 2nd law of Thermodynamics is based on the fact that heat will only spontaneously flow from a hot object to a colder object but it never will spontaneously flow from a cold object to  a hot object.

Whenever heat is used to do work a potion of the heat always goes to the colder location. This wasted heat is called entropy. Simply put you can never turn all of the heat into work and percentage of the heat converted in to work it the engines efficiency.  

Now applying work to a system can forced heat to go from a cold object to a hot object, which also reduces entropy, this shows that work can reduce entropy. This process is the basic theory behind air conditioners, refrigerators, and heat pumps.

Entropy is the measure of a system's thermal energy unavailable for conversion into mechanical work. It is also a measure of the equivalent states or multiplicity of a system and there by a measure of the disorder or randomness in a system.

In Classical Thermodynamics entropy is mathematically defined as dS = dQ/T.
These results in the change in entropy as: DS = Q/T.

  • S = entropy
  • Q = Heat energy
  • T = Temperature

In statically thermodynamics entropy is mathematically defined as S = k ln W.
This results in the change in entropy as: DS = k ln W2 / W1.
  •  S = entropy
  •  k = Boltzmann constant
  •  W = the multiplicity of a system.

Entropy and Disorder

The relationship between entropy and disorder is shpwn through the multiplicity of a system which is denoted by W. The multiplicity of disordered states (Wd) is many orders of magnitude grester than the multiplicity of ordered states (Wo) such that Wd >> Wo  this means they Sd >> So.

Since 2nd Law of Thermodynamics shows entropy tends to increase it also shows that the degree of disorder of a systems tends to increases. The only way to increase a system’s order; decreasing entropy; is for work to be performed on the system.

Abiogenesis and 2nd Law

The spontaneous process of life forming from non life by naturalistic means is called Abiogenesis. Now living things are the most ordered and complex systems that are known to exist, In fact even the simplest known living cell is infinitely more organized and complex than the most organized non-living chemical systems known to exist.

As a result the entropy of a living cell is many orders of magnitude lower than the entropy of the same amount non-living chemicals. This means that for abiogenesis to occur it must go against the 2nd law’s tendency towards increasing entropy.

Now it is true that entropy can be decreased by work being performed on a system but there is no evidence for a naturalistic mechanism performing the work needed for such a large decrease in entropy. Without this mechanism the 2nd law suggests that abiogenesis is impossible.

Applied Energy and 2nd Law

The 2nd Law Thermodynamics does indeed show that when energy is applied to a system it can reduce the system’s entropy. What it fails to show how the manner in which energy is applied affects entropy.  It does not show the deference between construction work and a bomb.

Construction work reduces a system’s entropy while bombs increase a system’s entropy.  Unfortunately the 2nd Law does not show the difference.  The result is that additional principle is needed to show this difference and this is also need to really determine if abiogenesis is possible or not.

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