# What do the Laws of Thermodynamics actually say?

BobSpence
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What do the Laws of Thermodynamics actually say?

OK, the First Law of Thermodynamics is about the conservation of energy. Matter is not mentioned.

It relates the amount of 'work' done by a defined system, eg an engine, as measured by a measured force on an external object moving that object through a measured distance (for linear motion), or a measured torque rotating a shaft by a measured amount, for rotational motion, to the net quantity of heat added to the system, as by burning fuel, and any change in internal energy, such as the energy contained in the matter in the system, which can typically be determined by changes in temperature of that material.

It says nothing about the creation or destruction of matter.

Einstein's famous equation says that changes in the amount of internal energy of system will produce a change in the measured mass of the system, ie how much force is required to accelerate the system by a given amount. There is no creation or destruction of matter involved here.

Studies in Particle Physics show that sub-atomic particles can be converted entirely into an equivalent amount of energy and vice-versa. Quantum Theory further complicates the issue by allowing for fluctuations in the energy level in 'empty space' to allow the momentary 'creation' of pairs of 'virtual' particle/anti-particle pairs which in an extremely short time mutually annihilate back to energy. There appears to be at least some evidence for this.

So any simple statement that matter can neither be created or destroyed is not a 'Law' of modern physics, the reality is much more complicated.

Even if we insist on conservation of the total amount of matter-energy, the net matter-energy total of the known universe may in fact be zero, since gravitational energy is treated as a negative quantity. In this argument, the hot fireball of the Big Bang contained an enormous amount of energy as heat offset by an equivalent amount of negative gravitational energy. In the ultimate state of an extremely dispersed universe of cold matter, the gravitational energy is now numerically near zero (and still negative), as is the heat energy of the matter, still summing to zero. Otherwise we have to ascribe an enormous amount of positive gravitational energy to a universe of particles so widely dispersed that their gravitational interaction is negligible.

If we combine this scenario with quantum fluctuations, there is nothing in Physics which precludes in any fundamental sense a particularly large quantum fluctuation in some possible eternal 'metaverse' crossing some threshold and becoming the Big Bang. Of course there are many unresolved issues here, and it is a very active area of speculation in physics and cosmology.

The point is that appeals to the First Law of Thermodynamics are completely out of place here. It just doesn't apply.

I'll tackle the other laws in later posts.

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

BobSpence
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The Second Law, part 1

The Second Law of Thermodynamics is concerned with the flow of heat energy and the related issue of the maximum amount of useful energy that can be extracted, or minimum that needs to be supplied, in the process.

The basic idea is that without the input of some other form of energy, heat can only flow from a region or body to another region or body if the destination is at a lower temperature than the source. In the process it is possible to convert some of the heat energy into other forms of energy such as mechanical energy. The maximum amount of 'useful' energy theoretically available as a fraction of the heat extracted from the source is

(Th - Tc)/Th,
where
Th is the temperature of the hot source and
Tc is the temperature of the cold destination, in degrees above absolute zero.

To make heat flow the other way we need as a minimum to input the same amount of external energy relative to the heat delivered to the hot region. This is what happens in refrigerators or heat-pumps.

To be able to convert thermal energy to useful work, eg raising a mass against the force of gravity, we need to have both hot matter to serve as a source of thermal energy, and cool matter to provide a place for the energy to flow to. Once we have allowed the energy to flow and hopefully extracted some useful work from it in the process, the hot source will be a little cooler and the cold 'sink' will be a little warmer. That means that the variation of temperature has been evened out a little. In a situation where all matter is at the same temperature, we would no longer be able to extract any energy from a heat engine. This situation is referred to as the 'heat death' of the universe, when it has reached a state of maximum entropy which is a measure of how evenly distributed thermal energy is.

This can be compared to water power, which is only available where we have water at some height above the surrounding landscape, ie with somewhere to flow down to and turn a water wheel or turbine as it does so. Once all the water is at the lowest possible level, we can no longer extract any mechanical energy from it.

The entropy of a system can be defined by the expression Q/T, where Q is the total heat energy in the system, and T is the absolute temperature, assuming the system is at a uniform temperature. So entropy will increase as we extract heat from a hot source and discharge the 'waste' heat into a cool 'sink', unless we achieve the ideal amount of energy conversion specified by the equation above, so that the entropy 'extracted' from the hot source is exactly balanced by the entropy discharged to the cold sink.

Qin/Th = Qout/Tc,
or
useful energy out = Qin - Qout = Qin * (Th - Tc)/Tc

The theoretical best we can do is not increase entropy in running a heat engine, in practice we will always increase entropy.

It is this association of increasing 'thermodynamic' entropy with the process of moving from a state where there are concentrations of energy in very hot objects in a much cooler environment, to a state where everything is at the same temperature, that has lead to other interpretations of the concept of entropy which are often used in Theist arguments against the natural appearance and evolution of life.

The state of maximum entropy is extended to not only include a uniform distribution of temperature, but of all forms of matter and energy, so there is literally nothing left to drive any form of 'action'. Thus increasing entropy is seen as leading to a total lack of any form of structure or pattern, which involves uneven distribution of matter/energy, and life is seen as an extremely complex structure, so the emergence of life from non-living matter, and the evolution of 'higher' organisms, is seen as a process of increasing complexity, which is perceived as being against the trend of increasing uniformity and lack of structure, and therefore highly improbable, if not impossible, in a universe behaving in accordance with the Second Law.

The first thing to be said is that nothing in the emergence and evolution of life is in conflict with the basic thermodynamic constraints described by the Second Law, ie life does not involve heat flowing spontaneously, ie without the input of other forms of energy, from a cooler body to a hotter, or the generation of more mechanical energy from thermal energy than allowed by the Second Law. Virtually all life processes are drive ultimately by the input of radiation energy from the Sun, or possibly from the flow of thermal energy from vents in the deep ocean.

It is only in the extended interpretation of the entropy concept that these other 'complexity' issues arise, but even in the broader interpretation, all the Second Law implies is that 'complexity' cannot increase without the input of energy. Heat can flow from a cool body to a hot body if energy is supplied, as happens all the time in your refrigerator. Until we reach the 'heat death' of the universe, still a long way off, there are plenty of available sources of energy - just go outside and look at the Sun or the stars...

I think I will leave a more detailed discussion of the broader interpretations of Entropy to another post.

Favorite oxymorons: Gospel Truth, Rational Supernaturalist, Business Ethics, Christian Morality

"Theology is now little more than a branch of human ignorance. Indeed, it is ignorance with wings." - Sam Harris

The path to Truth lies via careful study of reality, not the dreams of our fallible minds - me

From the sublime to the ridiculous: Science -> Philosophy -> Theology

Brian37
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I am sure Bob will love me

I am sure Bob will love me for this.  He knows the clomping of my one trick poney is trotting in.

Theists basterdize the lagit science mentioned by Bob above and try to use it as a distraction to say, "Well if this is possible, therefore my deity exists(incert label here)"

The problem with this tactic is that it is a smoke screen to distract you from the hocus pocus claims of holy books. "First Law, Second Law, Entropy......ect ect ect, are not mention in any ancient holy text, much less demonstrated.

This is nothing but an attempt on the theist's part to justify fitting a square peg into a round hole.

None of their elaborate scames where they cherry pick science will ever constitute dead human fleash surviving rigor mortis. It will never constitutute a disimbodied ghost knocking up a girl.

This tactic is a result of scientific method exposing the myth sold as fact for the past 2,000 years and theists dont like the fact that the truth is catching up with them. Insted of discarding bad ideas their egos wont allow them to discard what is clearly fiction.

They dont understand that they attempt to defend this because it is a club mentality that merely makes them feel good. "I cant be wrong because I dont want to feel like I am stupid or have been duped." I hate to tell you this Christians, you have been duped and you are wrong.

This is why I avoid these psuedo science distractions and cut to the chase. You say Mary was knocked up by God? Where does "Second Law" or "Entropy" explain HOW this is possible. "God did it" is a claim, not a emperical fact.

I have a better explination. Someone made this hocus pocus fiction up and claimed it as fact. So, I'll make you a deal Christians, when you can put God's sperm in a petri dish and put it under a microscope for me, then you will have something. Dont worry, I wont hold my breath.

Bob, I hope I didnt spoil anything for you. But you know me. I cut to the case and attack the magic. No amount of psuedo science will ever justify hocus pocus, no matter how hard they try.

It sickens me that theists will take the wonderfull tool of scientific method and try to justify Marvel Comics with it.

"We are a nation of Christians and Muslims, Jews and Hindus -- and nonbelievers."Obama
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Hambydammit
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Thanks for this post,

Thanks for this post, Bob!  Would you consider taking the complete version of this and making it into a book page so that the rest of us RRS author types could easily reference it for newcomers?

(I feel fairly certain that if you asked Brian, he'd be happy to give you an RRS authors section.)

Atheism isn't a lot like religion at all. Unless by "religion" you mean "not religion". --Ciarin

Cpt_pineapple
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Actually, the total amount

Quote:

the net matter-energy total of the known universe may in fact be zero

Actually, the total amount of energy may be as little as an ounce. (Due to space-time curvature, not being a perfect plane)

Zombie
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Excellent post Bob, easy to

Excellent post Bob, easy to understand and logical.