t=S

[arfa brane]

The problem with distance and time is that you have to assume, if dx/dt is real, that x is a function of t.

If f(x) = x[sup]2[/sup], d(f(x))/dx = 2x and d(f(x))/dt = 0. Time rates of change implicitly assume that time is a function of distance.

Oops. P.S., the math works as outlined.

 

[RJBeery]

More structured, but less information.
Probably the most complex non-organic thing in a city is a computer, but even very simple organic life would contain more information. A leaf of grass for example.

This misses my point. We, as sentient willful beings, could take ANY disordered system and reduce its entropy by imposing structure on it. We could wipe out a forest and replant the trees in a grid, for example. However, the process itself has a global net entropy increase, just as the creation of a memory does, even though local entropy may decrease.

 

[AlexG]

That's relativity's problem that it can't deal with things moving faster than c. There is nothing wrong with my scenario and it's not "stupid" because relativity can't deal with it. If anything is stupid it's relativity because it falls apart at the speed of light.

Because things can't move faster than c.

Your scenario is stupid because YOU can't deal with relativity.

 

[Secret]

@RJberry, Scifes, Wellwisher
Thanks for the clarification on the psychological arrow of time

Today some random browsing of scifi and wikpedia material about time gives me the below thought:

If we have a glass cup, 4 minutes later it shatters
->Normal
If we have some glass shards, 4 minutes later it become a glass cup
->It must be a video clip played in reverse as it is highly improbable for something more disordered to become more ordered according to 2nd Law of thermodynamics

Now I have a perfectly spherical ball on the middle of a frictionless table, 4 mnutes later it is at the edge of the table
If I video it and played one of the videos in reverse, is it possible to distinguish which video is which? (assume you don't know where the ball initially is and assume all you see is the ball moving only)

Or even:
If we have a ball that is stationary with respect to the table (and have no other changes) from 0-4 minutes. How can we tell which ball is the one from 0 mins and which ball is the one 4 minutes later?

 

[Reiku]

You don't understand Einstein's opinion of time, nor do you understand any of his theories even at a very basic level.

You don't know anything. You've managed to demonstrate that several times.

Einstein said (though I know this was not a qoute to me) but Einstein said that the past and future don't exist.

In reference to the OP, the psychological arrow is the complete opposite. The psychological arrow arises because there is a past and future distinction in the subjective psychological perception of the human mind.

Time has been argued not to even exist, according to the time problem of relativity and quantum mechanics. One could argue that the only real description is the psychological arrow. But we tend to imprint our percption of events on the physical world outside which might be erreneous.

More to the point, time does not even have a flow. So any talks which might include the idea that time flows from the past to future is pretty meaningless in physics.

 

[Reiku]

At best, all we can say is there is an eternal present. The present moment is all that ever exists. Past and future are just illusory concepts of a feeble mind trying to make an understanding of why events happen the way they do.

 

[Aqueous Id]

You can always construct an experiment in such a way as to produce a desired answer. So if you wanted to create ambiguity, you could make the video as proposed. Or, you could show the complete information: the beginning, where the ball (or balls) were placed on the table, and whatever was done to start one rolling. Initial conditions are requisite to resolving the ambiguity.

Another aspect of what you may be asking, is whether the 2nd law or thermodynamics requires that a ball be in any particular position before and after time elapses. The answer to that depends on more information not given. Otherwise I could say the ball has an equal likelihood of occupying any position on the table. Then when you come back and say "the table is tilted 1° lower in the NE corner", then we can say with certainty that it will have a nonrandom trajectory.

There are many dimensions to the question, you stated it very broadly. Do you have a particular idea you are pursuing? Say more if you wish.

 

[Robittybob1]

Regarding the arrow of time, it's purely a function of entropy. The real question to ask is, why did the universe possess a low-entropy state from which it could transition?

I don't think you will get an answer to that. I read on and see if I'm right.

 

[Robittybob1]

At best, all we can say is there is an eternal present. The present moment is all that ever exists. Past and future are just illusory concepts of a feeble mind trying to make an understanding of why events happen the way they do.

This idea will catch on, like everyone wants a sore thumb!

 

[Reiku]

This idea will catch on, like everyone wants a sore thumb!

I think it already has with some physicists.

 

[Secret]

You can always construct an experiment in such a way as to produce a desired answer. So if you wanted to create ambiguity, you could make the video as proposed. Or, you could show the complete information: the beginning, where the ball (or balls) were placed on the table, and whatever was done to start one rolling. Initial conditions are requisite to resolving the ambiguity.

Another aspect of what you may be asking, is whether the 2nd law or thermodynamics requires that a ball be in any particular position before and after time elapses. The answer to that depends on more information not given. Otherwise I could say the ball has an equal likelihood of occupying any position on the table. Then when you come back and say "the table is tilted 1° lower in the NE corner", then we can say with certainty that it will have a nonrandom trajectory.

There are many dimensions to the question, you stated it very broadly. Do you have a particular idea you are pursuing? Say more if you wish.

It is often said the arrow of time is mainly contributed by the thermodynamic arrow, govern by the 2nd Law of thermodynamics (that a closed system tend to increase its entrophy)

1. In the first case, a glass cup has lower entrophy than a bunch of glass shards. Thus a glass is more likely to shatter than a bunch of glass shards assemble into a glass cup. Therefore when shown a video of a glass cup shatters, it is more realistic then a video of the process occur in reverse and it will be said as being played in reverse.

->In this case the future and past can be distinguished easily

2. In the rolling ball scenario (assuming the table is horizontal plus all other aformentioned conditions) the entrophy of the ball at the center of the table should be the same as that near the edge of the table. The ball is intially rolling at 1m/s (with respect to the table) from the center towards the edge of the table. If I take to videos:

a. Shows the ball rolling from the center to the edge
b. Same as a but playd in reverse

Now if I show these two videos to a random person (who does not know about the experiement), he will think both cases are equally realistic

-> Thus the past and future is indistinguishable

In the 3rd case, where the ball is stationary at the center of the table. I then take two videos of it. I then played one of them in reverse and show the videos to a random person.

Q: As the ball is stationary (which means entrophy in this case is irrelevant), how can we tell just from the video that time has elasped (Assume the duration counter of the video is not visible nor other trick question conditions)?

Q2: Assume we can deduce that time has elasped for case 3, is the future and past distinguishable using just these two videos?

I think it already has with some physicists.

You are actully right, some physicist found that when manipulating some equations, the varible corresponds to time cancels out completely, hence an idea that time does not physicaly exist, however I forgot the sources on where I got these information from (except they are from one of the issue of Scientific American)

I also thought of that before, but the problem is without time, how to explain motion?

 

[Reiku]

Yes, that would be Wheeler and deWitt. The equation named after them, the Wheeler deWitt equation has a time derivative which vanishes. The wave function in this equation describes the whole universe. This means there is no global time.

But some have suggested that the absence of a global time must imply a singularity.

 

[Reiku]

But one way to avoid the global implications of no time, is by saying such a thing simply doesn't exist. Time might be strictly, local. In all practically implications, this is true as far as we know.

 

[Secret]

Unanswered question in post #31, thus bump

 

[Secret]

weekly bump

 

[Boris2]

I don't believe it is correct to say that relativity can't handle faster than light scenarios.

 

[Secret]

@boris: I'm still confused by relativity

Also weekly bump

 

[origin]

I will answer so you can quit bumping.

Q: As the ball is stationary (which means entrophy in this case is irrelevant), how can we tell just from the video that time has elasped (Assume the duration counter of the video is not visible nor other trick question conditions)?

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.

Q2: Assume we can deduce that time has elasped for case 3,

How could you do that?

is the future and past distinguishable using just these two videos?

It can be deduced from the first video for the reasons you posted. Glasses don't reassemble and jump back on a table.

I also thought of that before, but the problem is without time, how to explain motion?

There cannot be any motion with out time. All equations for motion have a time term.

 

[Motor Daddy]

Q: As the ball is stationary (which means entrophy in this case is irrelevant), how can we tell just from the video that time has elasped (Assume the duration counter of the video is not visible nor other trick question conditions)?

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.

 

[wellwisher]

This misses my point. We, as sentient willful beings, could take ANY disordered system and reduce its entropy by imposing structure on it. We could wipe out a forest and replant the trees in a grid, for example. However, the process itself has a global net entropy increase, just as the creation of a memory does, even though local entropy may decrease.

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.

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.