# Does entropy really explain time vector?

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I've heard many physicists put forward the second law of thermodynamics as an explanation of the vector of time. Can someone explain to me why that is not circular reasoning? It seems that it merely says that entropy increases with time therefore time must increase with entropy. How is that not circular? Isn't a better proposal needed for an explanation?

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Entropy is quite the little buzz word these days. I hate buzz words, but that is a different post. Time in simple terms is a measure of change or rate of change. So are changes causing time to move or is time causing change. This is the chicken and the egg. Sounds pretty circular to.

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Entropy is word from the past. Created by a guy from XIX. When scientists know nothing.

Rudolf Clausius had no idea about black holes - in them it's reversed - even little photons are merging and forming composite particles.

Imagine that you have apple - you can cut it to half, but you can't join these half again to form whole single apple. You can cut these half again, but you can't merge them.
You can cut piece of metal to half, and they're separated. If you would like to join them together you have to add additional energy to melt it or weld it.

?

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Suppose you had an ideal gas contained in a perfectly insulated box, and you made a movie showing the movement of all the molecules. You then ran the movie backwards. The motion of the gas molecules would look the same as when the movie was run in the forwards direction. But if the box was not perfectly insulated, and the temperature outside the box was initially warmer or cooler than the temperature inside the box, the movie would not look the same when it was run in the forward or the backward direction. And if someone inquired as to which version of the movie showed what actually happened as time passed, it would be the one in which there was an increase in total entropy of the system.

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The word entropy and the understanding of it in thermodynamics is in question by many scientists. It is basic understanding that adding energy adds entropy, but many don't find this to be true. Howard bloom for one raises the question that the big band lead more to order than entropy, and even it a super nova seen as entropy, in reality most of our heavy elements are formed, elements with higher and more complex forms.

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The word entropy and the understanding of it in thermodynamics is in question by many scientists. It is basic understanding that adding energy adds entropy, but many don't find this to be true. Howard bloom for one raises the question that the big band lead more to order than entropy, and even it a super nova seen as entropy, in reality most of our heavy elements are formed, elements with higher and more complex forms.

If you are going to claim that there is an argument that a supernova isn't a net increase in entropy, you need to cite the papers that argue this.

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No, entropy does not explain the arrow of time. Entropy is a quantity which can be defined with the help of statistical mechanics. It is the logarithm of the number of microstates (the position and velocity of each particle in a system) compatible with a macrostate (the state you observe). For example, a gas at a certain temperature has millions of microstates which give the same macroscopic characteristics you observe.

Entropy increases with time because greater number of microstates means greater probability. Therefore, when we say Entropy increases all we're saying is things tend to evolve to a more likely configuration, which is pretty obvious.

There's nothing in the microscopic laws of physics that forces entropy to increase. For all we know, we could be going from future to past and we would never realize, as long as entropy increased in that direction. In this sense, increasing entropy means going towards the future. However, the question still remains: why is entropy so much larger in one extreme of time than in the other?

For a better an longer explanation of this, check Sean Carroll's blog preposterous universe or read his book From Eternity to Here.

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There appears to be two definitions of Entropy based on :

1. The flow of energy

2 . Changing states of Order

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The word entropy and the understanding of it in thermodynamics is in question by many scientists. It is basic understanding that adding energy adds entropy, but many don't find this to be true. Howard bloom for one raises the question that the big band lead more to order than entropy, and even it a super nova seen as entropy, in reality most of our heavy elements are formed, elements with higher and more complex forms.

What I believe you are referring to is that heavy elements have a more ordered state and hence lower entropy than the lighter elements from which they were created, and that their creation occurred in a star that subsequently exploded.

But here is another example. A newly laid chicken's egg contains an undifferentiated region of egg yolk surrounded by egg white. When development is complete, the egg contains a fully formed chicken, a much more complex structure then what the egg originally contained. Does the entropy of the universe increase or decrease when the original egg develops into a chicken?

Edited by Bill Angel
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I've heard many physicists put forward the second law of thermodynamics as an explanation of the vector of time. Can someone explain to me why that is not circular reasoning? It seems that it merely says that entropy increases with time therefore time must increase with entropy. How is that not circular? Isn't a better proposal needed for an explanation?

If the Flow of energy ( which itself has a mystical connotation of 'something ' appearing in different forms), is the driver of change in entropy. Namely the flow of energy from a high temperature to a lower temperature, then it can be said entropy is increasing, as more order moves to more disorder. A change has occurred which is identified as less ordered. We might perceive this as a movement forward in time. Thus the direction in time is 'named' by definition.

Now what happens to time, or our perception of time ( yet another mysterious 'something' ..TIME .. ) when we create a situation where entropy is reduced , namely it cant be by heat energy flowing from low temperature to high temperature 'forbidden by definition ' and by observation. But if a state of increased order occurs without the supply of energy, then maybe a decrease of entropy occurs and time is perceived to have changed direction ? ( or stopped )

( Is this what occurs in nuclear fusion Hydrogen to Helium , ( more ordered ? ) in the center of the Sun energy is concentrated or increased not spread out ? ).At least until the Sun shines, then we are back to forward spreading out of energy and disorder and increased Entropy. What happened in that little ' ...moment ... ' of fusion ? Hum !

.Not sure if this is any help. It might present more questions. !

Edited by Mike Smith Cosmos
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The word entropy and the understanding of it in thermodynamics is in question by many scientists. It is basic understanding that adding energy adds entropy, but many don't find this to be true. Howard bloom for one raises the question that the big band lead more to order than entropy, and even it a super nova seen as entropy, in reality most of our heavy elements are formed, elements with higher and more complex forms.

Locally, the Entropy decreased regions exist, but total Entropy is increased.

The problem depends on how to set the system area.

Edited by alpha2cen
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Locally, the Entropy decreased regions exist, but total Entropy is increased.

The problem depends on how to set the system area.

If we are in the sphere of influence of any of the regions you mention above of " Entropy decreased region " do we then experience a reversed direction of time ?

.

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If we are in the sphere of influence of any of the regions you mention above of " Entropy decreased region " do we then experience a reversed direction of time ?

.

Time is a property of the whole universe. It obeys the theory of relativity.

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Time is a property of the whole universe. It obeys the theory of relativity.

In the fabric of space time , as per Einstein theory of general relativity, does not the fabric get very distorted at special locations. Eg at locations of great mass say black holes or a star, or a planet. Strange things happen with time as you near a black hole. Does not the same apply when the distance is very, very small .( m1m2 g/r squared). Say at the point of nuclear fusion or molecular activity ?

If so what is happening to time/ local entropy at these places ? Presumably the whole universe does extend down to very small distances, and although the mass of particles is small, the very small ( r squared term on the bottom line) surely makes gravitational attraction very large at these distances thus distorting the fabric of Space-Time ?? Was this not what Richard Feynman was talking about with "trouble with infinities "

.

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In the fabric of space time , as per Einstein theory of general relativity, does not the fabric get very distorted at special locations. Eg at locations of great mass say black holes or a star, or a planet. Strange things happen with time as you near a black hole. Does not the same apply when the distance is very, very small .( m1m2 g/r squared). Say at the point of nuclear fusion or molecular activity ?

If so what is happening to time/ local entropy at these places ? Presumably the whole universe does extend down to very small distances, and although the mass of particles is small, the very small ( r squared term on the bottom line) surely makes gravitational attraction very large at these distances thus distorting the fabric of Space-Time ?? Was this not what Richard Feynman was talking about with "trouble with infinities "

.

At first, we set the system as the Universe. Then, the universe time can go by the periodical difference of the Universe entropy.

But, the local time flow can be changed with the state of local space-time.

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At first, we set the system as the Universe. Then, the universe time can go by the periodical difference of the Universe entropy.

But, the local time flow can be changed with the state of local space-time.

Not really sure that I understand what you are saying. Could you spell it out in idiot style language. Thanks.

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Entropy is a property of a system, not a location. Discussing entropy "at the point of nuclear fusion or molecular activity" is meaningless. Discussing the entropy of that system before and after is not. (the entropy goes up)

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Entropy is a property of a system, not a location. Discussing entropy "at the point of nuclear fusion or molecular activity" is meaningless. Discussing the entropy of that system before and after is not. (the entropy goes up)

.

Surely if we put a line around a possible nuclear fusion say (2 x Hydrogen nucleus ) namely 2 protons to form p-p then decay to p-n then repeat 2x (p-n) = pp-nn (Helium nucleus) . The net result is surely a decrease in entropy by both definition a) an improved order b) increase in energy potential without net inflow of energy. Otherwise surely 'Suns' would not work. Decrease in entropy in this special confined, defined system as per Alpha2cen .?

Or have I got it all wrong ?

Edited by Mike Smith Cosmos
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.

Surely if we put a line around a possible nuclear fusion say (2 x Hydrogen nucleus ) namely 2 protons to form p-p then decay to p-n then repeat 2x (p-n) = pp-nn (Helium nucleus) . The net result is surely a decrease in entropy by both definition a) an improved order b) increase in energy potential without net inflow of energy. Otherwise surely 'Suns' would not work. Decrease in entropy in this special confined, defined system as per Alpha2cen .?

Or have I got it all wrong ?

He-4 has less entropy than the 4 free protons, but that's not the whole system.

You correctly mention a proton decay — each involves the emission of a positron and a neutrino. i.e. more particles, many possible states, when 2 protons fuse to form deuterium.

The step where a proton fuses with the deuterium releases a gamma. Another particle emitted. And after that you have to consider which branch you take, but the final answer is the same: there is no decrease in entropy of the system in fusion.

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He-4 has less entropy than the 4 free protons, but that's not the whole system.

You correctly mention a proton decay — each involves the emission of a positron and a neutrino. i.e. more particles, many possible states, when 2 protons fuse to form deuterium.

The step where a proton fuses with the deuterium releases a gamma. Another particle emitted. And after that you have to consider which branch you take, but the final answer is the same: there is no decrease in entropy of the system in fusion.

I will have to take your word for it. I am not sure I am up to the calculation of working out numerically the total entropy before and after the fusion process. Intuitively I feel that all these , and similar constructive processes are opposite to the destructive processes which we define as an increase in entropy. Surely symmetry would indicate a decrease in entropy ? No ?

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No.

Lower symmetry means decreased energy of a system. Which means less energy to do work. Which means increased entropy of the system.

Edited by MigL
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Damm, this mouse at work keeps double clicking and duplicating my posts,

Is there a way to get rid of the second post ?

Edited by MigL
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Damm, this mouse at work keeps double clicking and duplicating my posts,

Is there a way to get rid of the second post ?

yes go into edit your post at bottom . delete everything by back space. then save . it should vaporise as there is nothing there.

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No.

Lower symmetry means decreased energy of a system. Which means less energy to do work. Which means increased entropy of the system.

.But surely after fusion to He nucleus there is more energy to do work with.

Starting state

Mass before fusion is

( e=mc squared equivalent ) of 2 x P plus 2 X N {4 Particles} plus no Binding energy [ Disordered ] less usable energy

Finishing state

Mass after fusion is

( e = mc squared equivalent ) of 1 X PPNN plus Binding energy { 1 item only } [ more Ordered ] more usable energy

Then there are all the bits and pieces that come off in the process plus some radiation ( disordered ). ??

Not sure where they fit in to the entropy bit .?

Other than a source of more mass and energy which is obviously what comes out of the Sun and spreads out across the Universe including Earth.I think this bit is part of the disordered ( more entropy ). They did however come out in between the Start state and the finishing state of the System .

.

Edited by Mike Smith Cosmos

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