[puppypower (OP)]

The entropic force is a force that is generated by entropy. This force is easily provable in the lab, and is very common in the living state. The entropic force is not normally considered one of the forces of nature. However, this is only due to tradition/convention. It is not due to any lack of consistency with the definition of force.

One common example of the entropic force can be witnessed, experimentally, with the phenomena called osmosis. An osmotic device has two chambers separated by a semi-permeable membrane. One side will have pure water or water with low solute concentration; small amount of dissolved stuff. The other side will have a higher solute concentration.

The water can flow through the semi-permeable membrane, but the solute is restricted by the membrane. The result is potential is established between both sides of the membrane, such that the water will flow in the direction of the higher solute concentration.  In doing so, the water flow will generate a pressure head, that is called the osmotic pressure. Since pressure is defined as force/area, the osmotic pressure is connected to a force that is being applied over an area. This is represented below;



Osmosis is considered a colligative property of matter. What that means is osmosis is only dependent on the concentration of solute; dissolved things. It is not dependent on the characteristics of any particular solute. For example, the same concentration of Na+, Ca+2, Cl-1 or even neutral solutes like glucose will all generate the same osmotic pressure. Osmosis is not dependent on any of the standard four forces, but is driven exclusively by entropy. The water will attempt to increase entropy, driven by the second law, to homogenize both sides. Entropy will generate osmotic pressure, which I will define as entropic force/area. Entropic force means a force driven by entropy.

The entropic force is widely used by the living state; cells, due to the wide range of membranes and their selective permeability for solutes. Water can freely moves across these membranes. The entropic force is used to generate pressure. This can be used to drive work cycles. It can also be used, through osmosis and reverse osmosis, to regulate the local and global entropy of the water. Entropy a state function, meaning it is based on the state of matter. The cell can use the entropic force to regulate entropy, thereby allowing it control the state of the cellular matter. Thus allows it to interface the standard forces of nature such as the EM force.

I know the entropic force, although provable, is not part of the standard four force tradition. But it should be included as the fifth force, even if the unification of five forces will be made more difficult than using only four forces. It is hard to fully describe the living state, in a logical way without this extra force. Without the entropic force, life remains a random mystery.  But with it, random things become quantified with ordered logic.

[the5thforce]

[jeffreyH]

I hadn't really studied osmosis so I learned something new. Thanks puppypower.

[chiralSPO]

I don't think that osmotic pressure establishes entropy as a force. And there are a few reasons why:

1) The most important part of establishing an osmotic pressure is the mechanism of allowing only one substance to cross from one chamber to another: Whether it is a semipermeable membrane that allows water to cross, but not some other type of dissolved species, or a shared headspace that allows volatile compounds to exchange between the chambers without allowing the exchange of non-volatile species. What drives the equilibrium is not necessarily entropy, but the sorting mechanism that is applied.

For instance let us imagine two chambers separated by a water-permeable membrane. One chamber contains a 1 molal solution of compound X in H₂O, while the other contains pure H₂O. Using colligative equations, we find that there should be an osmotic pressure of 24.6 atmospheres at 300 K (pressure in atm = 0.0821 * T in Kelvin * molality of dissolved species). If compound X is something like pyridine or t-butanol, this is perfectly valid. But what if compound X is D₂O? The entropy of mixing is unchanged, but D₂O can cross the barrier at the same rate as H₂O, so there will be 0 osmotic pressure!

In essence, there is one characteristic of the solute that does matter, and that is the extent to which is is capable of moving between chambers.

2) The source of the energy is thermal. You can think of the semi-permeable barrier as a device analogous to a valve or a winch or one of those watches that charges itself using the mechanical energy of the wearer's pace. Each of these can allow random or multi-directional motions to be unidirectional. There is nothing magical involved, and all of the energy can be traced back to electrostatic or gravitational sources (or one of the other two forces, but this is rarer), so there is no 5th force required.

[puppypower (OP)]

 

I don't think that osmotic pressure establishes entropy as a force. And there are a few reasons why:

1) The most important part of establishing an osmotic pressure is the mechanism of allowing only one substance to cross from one chamber to another: Whether it is a semipermeable membrane that allows water to cross, but not some other type of dissolved species, or a shared headspace that allows volatile compounds to exchange between the chambers without allowing the exchange of non-volatile species. What drives the equilibrium is not necessarily entropy, but the sorting mechanism that is applied.

For instance let us imagine two chambers separated by a water-permeable membrane. One chamber contains a 1 molal solution of compound X in H₂O, while the other contains pure H₂O. Using colligative equations, we find that there should be an osmotic pressure of 24.6 atmospheres at 300 K (pressure in atm = 0.0821 * T in Kelvin * molality of dissolved species). If compound X is something like pyridine or t-butanol, this is perfectly valid. But what if compound X is D₂O? The entropy of mixing is unchanged, but D₂O can cross the barrier at the same rate as H₂O, so there will be 0 osmotic pressure!

In essence, there is one characteristic of the solute that does matter, and that is the extent to which is is capable of moving between chambers.

2) The source of the energy is thermal. You can think of the semi-permeable barrier as a device analogous to a valve or a winch or one of those watches that charges itself using the mechanical energy of the wearer's pace. Each of these can allow random or multi-directional motions to be unidirectional. There is nothing magical involved, and all of the energy can be traced back to electrostatic or gravitational sources (or one of the other two forces, but this is rarer), so there is no 5th force required.

Arguments could also be made about the limitation of the four traditional forces as defined by particles accelerator data and  elementary particle interactions. Particle accelerators use high energy/temperature but low pressure. One cannot tell from low pressure data, how these same particles will interact at extreme pressure. This data represents a narrow bandwidth on a larger diagram.

In chemistry, materials are defined using phase diagrams, with material properties defined as a function of temperature and pressure. There are high pressure phases of water, where water will become a metal. This metallic state of water, would not be evident at atmospheric pressure no matter what temperature you use. One does not expect free electron mobility from water when it acts polar ionic. The EM forces are behaving in a new way.

Extreme pressure elementary particle phases will not be seen in the atmospheric pressure based particle accelerators. In my opinion, extreme pressure phases would blur the expected lines between forces, since certain phase interactions would not longer appear, and new ones would appear.

Pressure is force/area. Pressure can be generated by any of the four forces as well as by entropy. As we increase pressure, such as in the core of a star, we are adding a unifying force; pressure, that can impact all other forces, allowing new phases and phase changes to appear. The nuclear and EM can both be contributing to the bulk pressure.

The living state is a natural part of nature. Osmosis is an intrinsic part of life. Osmosis generates pressure, by means of entropy; colligative property, to alter the states of matter. Entropy is a state variable meaning there is a specific value of entropy for each state of matter. The same is true of phases of matter. The cell can fine tune the states it needs by applying entropic force, via pressure.


Reverse osmosis is where we apply pressure and cause water to reverse itself through the membrane from the side of higher solute concentration to the side of lower solute concentration. We apply this pressure with a weight; gravity. We can do this with a magnetic field; M or even a spring; EM. We can even use another osmotic device and generate positive pressure using entropy. The reverse osmosis allows lower entropy. Pressure can be used to control entropy, just like pressure can be used to define the states and phases of matter.

Pressure is the unified force, since it can be generated by all four standard forces as well as by entropy. It can also impact all four force plus entropy; define the stare of matter. I define force in terms of the ability generate unifying pressure=force/area and use that pressure to interface other forces and entropy.

Osmosis is somewhat limited in terms of the pressure it can generate. It is designed to work with the secondary binding phases of  enzymes; entropic lever for the EM force.

[jeffreyH]

Surely entropy is a consequence of actions and not a cause. Since in general entropy always increases then the more interesting point is finding other properties that also always increase.

If we look at the expansion of the universe then we could speculate that the amount of dark energy is always increasing. Since we consider dark energy to be a repulsive monopole then we may be able to tentatively state that as entropy increases the effects of gravity decrease. Not because the force of gravity is decreasing but that the interactions of gravity with matter of a higher entropy are weaker.

If the strength of the interactions between mass and gravity depend upon entropy then a lower entropy universe may have to have less dark energy. This may just be another law of nature.

[chiralSPO]

I have often wondered about the role of entropy in the expansion of the universe (more on this later--I have to go to the dentist now...)

[chiralSPO]

The entropy of a system (S) is related to the number of states (W) the system can be in by S = k*log(W).

A gas will expand to fill an available vacuum because each particle can be in more different locations (more states). By analogy, one might expect that space could expand to give the gas more possible states.

But the question is, as space expands, is it in such a way that there are actually more states available? If we imagine the universe as an image made of pixels (more pixels = more information = more entropy) as the image expands, is it adding pixels, or are the pixels getting bigger? If it is the latter, then I would not expect this process to be driven entropically.

Another question is, if we assume that expansion is adding pixels, does the change in entropy rely on there being matter that can form multiple states? One might expect that regions of the universe with more matter to expand more rapidly than empty regions...

[jeffreyH]

The entropy of a system (S) is related to the number of states (W) the system can be in by S = k*log(W).

A gas will expand to fill an available vacuum because each particle can be in more different locations (more states). By analogy, one might expect that space could expand to give the gas more possible states.

But the question is, as space expands, is it in such a way that there are actually more states available? If we imagine the universe as an image made of pixels (more pixels = more information = more entropy) as the image expands, is it adding pixels, or are the pixels getting bigger? If it is the latter, then I would not expect this process to be driven entropically.

That is a very pertinent point. It lies at the heart of the question of whether or not entropy has any link to the expansion of the universe.

Another question is, if we assume that expansion is adding pixels, does the change in entropy rely on there being matter that can form multiple states? One might expect that regions of the universe with more matter to expand more rapidly than empty regions...

Again this raises an issue regarding the linear nature of the expansion. You cannot avoid the results of Hubble's observations. What is your opinion of a link between entropy and expansion?

[chiralSPO]

Again this raises an issue regarding the linear nature of the expansion. You cannot avoid the results of Hubble's observations. What is your opinion of a link between entropy and expansion?

It is entirely possible that the universe is saturated with particles that we cannot observe (dark matter anyone? maybe virtual particles?) such that expansion anywhere is entropically favored, and there is no significant relationship to the matter that we do observe. Therefore the linear relationship between distance and velocity (and subsequent acceleration) would make sense.

[jeffreyH]

I would tend to agree with that point of view.

[puppypower (OP)]

Energy is needed for entropy to increase. The units of entropy are joules/K (joules/degree Kelvin). The sun does not collapse into a solid hydrogen state of lowered entropy, because it is supplying it own internal heat/energy to maintain higher entropy states. The energy output allows for more possible states W, as a plasma, than as a solid hydrogen metal. 

If we expand a gas, such as spraying the air from the can used to clean a computer keyboard, the gas and the can will both get cold. The gas and can will both show a red shift; IR into longer wavelength implies cooling, even though only the gas is moving. The entropy is increasing in both the gas and the inside go the can (higher W). This is absorbing heat for the entropy increase. 

If you had a giant compressed sphere of gas, floating in deep space, that was leaking gas in all directions so there is no change in velocity, the sphere would get colder and would appear to red shift. The sphere would appear to be moving away, if we assume a red shift can only due to motion, but not the 2nd law.

If we assume the BB from a singularity, then the number of states W, will need to increase from one. This means energy will be absorbed to supply the needs of the entropy increase and the higher number of possible states; W. The universe will cool and red shift as more states appear. It does not need to be in motion, as long as more degrees of freedom appear. This may be why motion is assumed relative. It does not even have to go anywhere. When the sub particles appear, the number of states W increases by orders of magnetite; universe would quick chill, red shift, inflate. This is all blended.

Back to Osmosis:

With osmosis, the water moves through the membrane in the direction of the higher solute concentration. This is driven by entropy; 2nd law. This direction of movement allows the water and the solute to experience additional states W, by each being among a higher concentration of the other. The opportunity to increase entropy presents itself, with only the water able to move.

Since entropy needs energy to increase, while osmosis is a collative property, and does not depend on the force characteristics of the solute; the solute can be single or double charged, all plus or all minus, dipoles, or even neutral. In all cases, the same entropic force will be generated by the water, if there is the same concentration of any one or combination of these. If entropy and the entropic force needs energy to increase, what is the source of energy if not from the solute EM? 

The source of energy is in the water. Only reverse osmosis needs an external energy source. This is similar to forces which carry their own energy potential. We only need to an external source to reverse the potential; reverse osmosis. 

The traditional explanation for the energy source is the water molecules are in random motion; random collisions. The membrane offers no real barrier to this motion, so the water will collide randomly through the membrane. The solute adds more possible states for the randomness of the water, with the increasing amount of random pulling in more and more energy, thereby exerting more and more pressure.

This sounds good for ideal solvents, but this is not 100% true for water, since water is highly ordered because of hydrogen bonding. Each water molecule can form four hydrogen bonds which are stronger than most random collisions. This order is why water has such a high melting and boiling point for something so small. Water weighs as much as methane; molecular weight, but boils at +100C instead of  -161C. This is due to hydrogen bonding.

Random collision is more limited in water, compared to an ideal solvent. Water increases entropy differently, than an ideal solvent, by altering the internal entropy of its order. Suffice to say this internal tweaking of entropy by water, allows water to tweak entropy even without osmosis, such as near enzymes. Osmosis is more used for regulating global background entropy. This is getting long, I will explain this another time.

[puppypower (OP)]

The entropy of a system (S) is related to the number of states (W) the system can be in by S = k*log(W).

A gas will expand to fill an available vacuum because each particle can be in more different locations (more states). By analogy, one might expect that space could expand to give the gas more possible states.

But the question is, as space expands, is it in such a way that there are actually more states available? If we imagine the universe as an image made of pixels (more pixels = more information = more entropy) as the image expands, is it adding pixels, or are the pixels getting bigger? If it is the latter, then I would not expect this process to be driven entropically.

Another question is, if we assume that expansion is adding pixels, does the change in entropy rely on there being matter that can form multiple states? One might expect that regions of the universe with more matter to expand more rapidly than empty regions...

The idea of states W for entropy is useful because it tells use entropy is not necessarily randomness. For example, say we start a hydrogen molecule H2. There is a certain amount of energy needed to break the covalent bond; overcome the EM forces to form two atoms of hydrogen; 104 kcal/mole.

If add smaller amounts of energy to increase entropy, but not enough energy to break the bond, than more states W of the hydrogen molecule will appear  The entropy increase can be defined as vibrational, rotational, translational, torsional and bending states for the hydrogen molecule. These states of entropy are not exactly random, but define distinct classes of quantized energy levels that are the same for any H2. This gives us a unique H2 fingerprint.

These extra entropic states W add potential energy to the hydrogen molecule and place different strains on the EM force based covalent bond, but not enough to break the bond. In this case, the entropy is defining force opposite the EM force but in 3-D. This entropic force is translating, pushing, pulling, bending, twisting and rotating the hydrogen adding potential to the EM force. This is simpler to way pressure impacts 3-D surfaces; from all sides. Osmotic pressure extends this.

We may call a very specific instant of these five sub-states, random. But in the long term, these states will come under the umbrella of five classes of motion, each with certain quantum states. Entropy is about long term character as well as the short term uniqueness, with both allowing distinct variety in the four base forces; 3-D swiss army knife anti-force.

For example, if we added heat to the core of the earth, new states of interaction will appear among all the materials mediated in 3-D by pressure.

[jeffreyH]

The entropy of a system (S) is related to the number of states (W) the system can be in by S = k*log(W).

A gas will expand to fill an available vacuum because each particle can be in more different locations (more states). By analogy, one might expect that space could expand to give the gas more possible states.

But the question is, as space expands, is it in such a way that there are actually more states available? If we imagine the universe as an image made of pixels (more pixels = more information = more entropy) as the image expands, is it adding pixels, or are the pixels getting bigger? If it is the latter, then I would not expect this process to be driven entropically.

Another question is, if we assume that expansion is adding pixels, does the change in entropy rely on there being matter that can form multiple states? One might expect that regions of the universe with more matter to expand more rapidly than empty regions...

The idea of states W for entropy is useful because it tells use entropy is not necessarily randomness. For example, say we start a hydrogen molecule H2. There is a certain amount of energy needed to break the covalent bond; overcome the EM forces to form two atoms of hydrogen; 104 kcal/mole.

If add smaller amounts of energy to increase entropy, but not enough energy to break the bond, than more states W of the hydrogen molecule will appear  The entropy increase can be defined as vibrational, rotational, translational, torsional and bending states for the hydrogen molecule. These states of entropy are not exactly random, but define distinct classes of quantized energy levels that are the same for any H2. This gives us a unique H2 fingerprint.

These extra entropic states W add potential energy to the hydrogen molecule and place different strains on the EM force based covalent bond, but not enough to break the bond. In this case, the entropy is defining force opposite the EM force but in 3-D. This entropic force is translating, pushing, pulling, bending, twisting and rotating the hydrogen adding potential to the EM force. This is simpler to way pressure impacts 3-D surfaces; from all sides. Osmotic pressure extends this.

We may call a very specific instant of these five sub-states, random. But in the long term, these states will come under the umbrella of five classes of motion, each with certain quantum states. Entropy is about long term character as well as the short term uniqueness, with both allowing distinct variety in the four base forces; 3-D swiss army knife anti-force.

For example, if we added heat to the core of the earth, new states of interaction will appear among all the materials mediated in 3-D by pressure.

entropy
ˈɛntrəpi
noun
1.
PHYSICS
a thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system.
"the second law of thermodynamics says that entropy always increases with time"
2.
lack of order or predictability; gradual decline into disorder.
"a marketplace where entropy reigns supreme"

Looking at the first definition leads to a conclusion that ultimately entropy and heat death are in fact the same thing. Correct me if I am wrong here. Unavailability of thermal energy also implies a tendency towards static, inertial kinetic energy. If the universe expands to a point where gravity can no longer operate on remote objects then only local gravitational fields would have any effect. Except that dark energy is said to be repulsive. If dark energy exists and only operates on the spacetime between galaxies then a tendency towards static kinetic energy is still possible if the dark energy does not interact with matter. Since spacetime can expand at a rate that appears to be faster than the speed of light this should be the case which would preserve inertial frames of reference. Just my musings.

[puppypower (OP)]

The topic was whether entropy could be defined as the fifth force. If you assume entropy appears as disorder, isn't force needed to upset an ordered system composed of matter? Entropy can impact ordered systems held together by any of the four standard forces and can therefore counter all the forces, like it is a unified repulsion force.

The same could be said of dark energy upsetting an ordered system, by adding entropy through changes in space-time. One might even argue that the red shift is connected to entropy since energy is loss, via a red shift, that cannot longer go into work. If we red shifted from visible light to IR, we have lost potential that cannot be used for work. 

The paradox of dark energy is, if dark energy expands space-time and this causes a red shift in the energy, then the value of energy is going down. This makes dark energy have the impact of negative energy. Do the energy balance! Negative energy should, in turn,  help the gravitational force, by cooling matter and removing repulsion, and lowering the heat that is available to entropy.