You cannot tell if the video is going forward or backwards or infact if it is even a still picture so you cannot tell that time has elapsed.
Exactly (elaborations below)
(Elaborations below)
It can be deduced from the first video for the reasons you posted. Glasses don't reassemble and jump back on a table.
Bolded part is a consequence of the 2nd law of thermodynamics. However (elaborations below)
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Elaboration:
The point of my "thought experiment" is to investigate the relationship between time and entropy
In daily life, we usually perceive that time elapse and always go irreversibly from the past to the future, we remember the past but not the future (psychological arrow of time). In physics they investigate this issue known as the arrow of time.
The first half of this question (why the psychological arrow seemed to be going against the direction of entropy) is answered by various users on this thread mainly in page 1 and 2
Now get back to your quotes:
From what I read about here
http://en.wikipedia.org/wiki/Arrow_of_time
, some brief knowledge of the 2nd law of thermodynamics and the daily experience of mixing coffee with milk or breaking glass. It seems apparent to me that
time is a function of entropy. However as I continue to browse other materials, I think it might not be that simple
wikipedia said:
Consider the situation in which a large container is filled with two separated liquids, for example a dye on one side and water on the other. With no barrier between the two liquids, the random jostling of their molecules will result in them becoming more mixed as time passes. However, if the dye and water are mixed then one does not expect them to separate out again when left to themselves. A movie of the mixing would seem realistic when played forwards, but unrealistic when played backwards.
Now imagine that the experiment is repeated, this time with only a few molecules, perhaps ten, in a very small container. One can easily imagine that by watching the random jostling of the molecules it might occur — by chance alone — that the molecules became neatly segregated, with all dye molecules on one side and all water molecules on the other. That this can be expected to occur from time to time can be concluded from the fluctuation theorem; thus it is not impossible for the molecules to segregate themselves. However, for a large numbers of molecules it is so unlikely that one would have to wait, on average, many times longer than the age of the universe for it to occur. Thus a movie that showed a large number of molecules segregating themselves as described above would appear unrealistic and one would be inclined to say that the movie was being played in reverse.
(Currently the most convenient source I can find for this discussion is above, other sources include discussion with my peers, and some scifi wikis)
Similarly, if I remember correctly, that when considering the kinetics of some objects classicially that if one reverses the direction of time, they get the same result, in this case the motion of a (classical) particle is symmetric for both directions of time. (I'm not sure about the relativistic case cause I'm still confused by relativity)
For the glass cup case, since a broken glass is more disordered (or its energy is more evenly distributed in other degrees of freedom,thus become less usable (if I remember correctly the alternate definition of entropy)) than an intact glass. We say the broken glass is future while the intact glass is the past. Thus if we played this video backwards, we say it is fake as it is highly improbable for a glass to jump back onto itself, as you have stated, as a consequence of the 2nd law of thermodynamics. Thus it seems my assumption bolded still hold
Now to the stationary ball case:
If the ball is stationary (this ball is classical for the sake of argument, that is we ignore the internal vibrations of the particles that consituet it, i.e. treat the ball as one large billard ball object commonly found in classical mechanics), it means
its entropy is unchanged. As you have already pointed out, if I make video of this, you can't even tell whether this is a video played in reverse, forward or just a picture, and you also deduced that you cannot determine whether time has elasped or not. Thus if using my bolded assumption above, it means time have not elasped at all. But in reality, if you left a ball in a place, even though a ball is observed to be unchanged, we still know time has elasped. This case thus serve as a counterexample of my bolded assumption above. Thus I have a conclusion that the elapse and arrow of time seemed to be not just based on entropy (or 2nd law of thermodynamics) (P.S. It might be my mistake of trying to assume that we can deduce the elapse of time in my thought experiment in respond to your 2nd quote, I apologies for that)
The question is, why in reality we still know that time has elasped even though the ball does not change, and what is the other factor that consituet our perception that time elaspe and have a preferred direction?
There cannot be any motion with out time. All equations for motion have a time term.
I do noticed this, however I'm always wondering what time actually is. That's why when I read about some theories that time, e.g. here
http://www.scientificamerican.com/article.cfm?id=is-time-an-illusion
I always ask myself, how can you explain motion without time
If my memory serves, I remember the explanation to the above question in that magazine is analogous to the relationship between money and apples oranges etc. That they said money is just a convenient notation e.g. $4.5 per apple, $3.5 per orange. There they said instead of using money, they relate things directly e.g. 9/7 oranges per apples. Using this analogy, instead of using seconds, they said some weird things such as a complete rotation of earth equals (forgot number) heart cycles. However I found this explanation counterintutive as they are simply treat the things relatively. They still have not explained why there is motion in the first place?
Thus I found theories where time is absent hard to explain for itself.
And this is why I have set up a total of 3 threads investigating the nature of time in different aspect with other users, while I slowly learn the required stuff in uni
In order for the camera to have recorded a movie of a ball the ball must have been giving off light. Light travels a distance in a duration of time. Just the mere fact that you can see the ball in the video means that light is traveling and time is elapsing. If time was not elapsing you would not be able to see the ball.
If you really want to get nit picky, the ball is actually changing over time, so slow in fact that you can't observe it. If the camera was a time lapse camera, and you recorded for a million years, you would clearly see the ball change over time. Observing a mass for a couple minutes and claiming no change occurs is absurd! That's like watching a banana on the counter top for a split second and claiming the banana doesn't change. Let the banana stay there for two weeks and see what the banana looks like.
@nit picky case, this is a consequence of the 2nd law of thermodynamics
@Case of light: yup this really showed time has elapsed (as c is still a finite quantity, depsite it is very large, that means there must be a finite, however small amount of time passed between the events of the ball reflecting the light and the light entering our eyes) The question is, in this particular scenario (we ignore the nit picky case here for the sake of argument) is the entropy between the events are different at all? Cause if it isn't, like what I replied to origin above, that means time is not just based on entropy. And the question remains on the nature of the elapse and arrow of time
This is not true of work cycles, such as gravitational work. For example, I have a machine that is 80% efficient. This means that 80% of energy going into my machine is used for work, and only 20% of that energy goes into entropy. Entropy needs energy and it only gets 20%. The other 80% is taken away from the normal expected entropy.
Say my machine is designed to use its work cycle, to lower entropy, and it is still 80% efficient. I will use energy to lower entropy, but since the machine is only 80% efficient, I will still get about 20% residual entropy, but in a different guise. The net affect of my work cycle is a lowering of entropy by 80% compared to random events. The cation pumps at the membrane can lower entropy better than 80% with respect to the cations.
In your work cycle scenario, if your input is E, that means 80%E is used for doing work (physics) and 20%E is dissipated as heat (which account for the entropy increase). As you can see there is an 20% energy loss to entropy. If you machine can lower entropy as stated in the itallics, then you should get more energy than you pumped in (i.e. you should get 180%E instead of 80%E, thus the portion used to contribute to entropy should be -80%E instead of 20%E) which is forbidden by the 2nd law of thermodynamics (Even if we assume the extra 80%E is from elsewhere, thus energy is still conserved)
The problem some people are having with entropy, is due to an erroneous assumption in science connected to chaos. They assume chaos rules the universe therefore everything is random. If this premise was true, than entropy would need to always increase. But chaos is actually a subset of entropy, with entropy able to control chaos.
Let me give an example. We have a tank of water. Within the water, the lord chaos is active allowing us to model the tank of water via statistics. Next, I open the plug at the bottom of the tank and the tank drains. Chaos has no choice but to go down the drain in a very orderly fashion. Chaos will not have the influence needed to flow out of the drain into the tank via probability.
Entropy is the entire effect, with the chaos within the water going down the drain, one of its many pawns. The pawn can't fight gravity. The entropy in the above example, gets its energy from the controlled release of potential energy in the tank. If we use this energy, instead for a work cycle, and are 80% efficient, we can further man handle entropy and chaos. The amount of choas and entropy is at a deficit compared to chaos, therefore we have created an entropy potential. We can make use of that too.
Assume we ignore the energy required to construct the tank in the first place (since the main character of this scenario is the water in the tank)
Accoridng to Newton's law of gravitation, the gravitational potential energy (GPE) is defined as the work done to move a unit mass from a point P to infinity. Thus the lower the object is located in the gravity well, the less GPE it has.
The reason why the water molecules move randomly in your scenario yet they all seemed to fell into the drain in a orderly fashion can be explained if we consider the tank and the drain network as ONE system. In this system, the drain is located below the tank, thus it has less GPE than the tank.
The water molecules have random motion hence disorder but in this system since it is located in the tank thus they as a whole have more GPE energy (hence less entropy) then the water in the sewers.
It is this GPE gradient that forces the water to drain in a orderly fashion to the sewers below, and the flow of water thus provide a means to convert their kinetic energy into work. After all the water has flowed into the sewers,
its entropy is much lower than the initial water in the tank (since you now have less energy available to do work)
Alt definition of entropy
wikipedia said:
Entropy is a thermodynamic property that can be used to determine the energy not available for work in a thermodynamic process
Which means when you go into the maths, entropy is the average amount of energy per degrees of freedom (or temperature) (e.g. rotation, vibration, translation motion etc.). These energy are used in the vibration of molecules etc. thus they cannot be used to do work and are considered as lost
The entropy in your scenario seemed to be decreased is because you only consider the tank as the system. As water flowing down the drain of course its entropy is decreasing.
However the 2nd law of thermodynamics stated that:
Entropy in a CLOSED system tend to increase (with time)
Your case is actually an open system (I don't have the words to explain why, I'll leave this to the people who know more about thermodynamics) that's why 2nd law seemed to be not applicable. You case is similar to the scenario when I was investigating the psychological arrow of time (as memory (which is regulated by the synapse) is clearly more ordered than a bunch of random neuron signals, thus the entropy is decreasing, thus seemed to violate the 2nd law) then numerous users explained that 2nd law allows entropy to be decreased in a certain open system (i.e. locally) but the drecrease is compensated elsewhere when you consider the universe (or even the multiverse) as a system. In this case we have a closed system thus entropy tend to increase.
TO conclude, it is basically what motor daddy said in the below quote (minus the emotional words)
You are trying to claim that the second law of thermodynamics is wrong. I'm sorry to tell you but you are the one making false claims. In a closed system entropy always increases, there is no way around it. Every physical process complies with the second law!
In your water scenario, it took energy to build the tank. It took energy to get the water in the tank. The net effect is that there was a net increase in entropy in the closed system known as the universe. There is no way around it!
No known process have shown to violate the 2nd law. Even in the maxwell demon experiment
http://www.nature.com/nphoton/journa....2008.145.html
The laser that is used to lower the temperature hence entropy requires electricity (a form of energy) to be activated in the first place.
I will answer so you can quit bumping.
I sorry that it is very annoying.
Few people tend to investigate an issue in detail
My friends often complain that I focus on the details too much, thus result in annoyance
However I think this should be the attitude for one doing science (no I don't mean keep asking people). IF you are not critical, how can you unlock more mystery of nature?
Concluding: If I shown some sort of cranky behavior (e.g. avoiding questions, saying pseudoscientific stuff etc.), please explain to me the correct concepts. A person learnt more from mistakes than success
