2 Futures Can Explain Time's Mysterious Past 107
cyberspittle sends this excerpt from Scientific American:
Tentative new work ... suggests that perhaps the arrow of time doesn't really require a fine-tuned, low-entropy initial state at all but is instead the inevitable product of the fundamental laws of physics. Barbour and his colleagues argue that it is gravity, rather than thermodynamics, that draws the bowstring to let time's arrow fly. Their findings were published in October in Physical Review Letters.
Yes, I saw a movie that explained this once. (Score:3, Interesting)
It was Back to the Future, Part II [imgur.com].
Arrow of Time (Score:5, Informative)
The article is wrong when it says that the laws of physics work the same going forwards or backwards in time. They do not and there is data to prove it. So the 'arrow of time' does not need any entropy to define it - it is baked into fundamental particle physics.
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Eggs turn into chickens at a different rate than chicken turns into eggs. This is proof either that A) time must go forwards, or B) my proof has a logic flaw in it.
If time flowed backwards, 0, -1, -2, -3.... all those reactions works in reverse because that is what they did already. Hence the logic flaw. You know how the system behaved at t-1, t-2, t-3, yet you assume it must be symetric in forward time. Like assuming that chickens turn into eggs at the same rate eggs turn into chickens.
Particle physics has
Entropy (Score:2)
Eggs turn into chickens at a different rate than chicken turns into eggs. This is proof either that A) time must go forwards, or B) my proof has a logic flaw in it.
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If I start with the glass on the table then there are is a very large range of momenta I can give the glass to arrive at the state where it is s
Re:Arrow of Time (Score:4, Interesting)
Time cannot go backwards because time, as an independent phenomenon doesn't exist. The passage of time, and what enables "change" is the expansion of the universe. It expands slower or faster near or away from the influence of gravity as time passes faster or slower near or away from the influence of gravity. Time and space aren't simply "relative". The are the same thing. Entropy is strongly correlated but not actually coupled.
IANAP, and I haven't actually convinced anyone that the way I see it is true. But I think the universe described by Renate Loll is probably the closest to my own mental picture. Or, at least, the idea that there are not really three spacial dimensions but one made my own mental map easier to "run" in my mind.
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Throw a ball, it follows a parabolic path, y=f(x). You can define it in terms of x. x=universe expansion if you will, its just a value that changes. You can define it in terms of t, time if you will f(t) this is how we normally define our universe, you can define it in terms of how many farts the world has made so far today if you like f(f). Perhaps your universe smells bad.
So therefore y is a function of farts because that is how I defined it.
I'm not really disagreeing with you, I'm simply explaining that
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I might not understand what you're saying.
The farther away galaxies are from each other, the faster they are moving from each other, and, the faster they are accelerating. Wouldn't this and other phenomenon be independent of my perception? I mean gravity doesn't only affect my physical being and the construction of it in my mind. It objectively affects the passage of time throughout the universe. Doesn't it?
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The base and top will align to a certain star at the same time each day, and they will perceive a day as slightly different in duration between base and top. (This assumes we've got sufficiently precise clocks to notice the difference, and indeed some have been invented.) If you made a clock based on the spinning of the planet, it would not change based on gravity. (It would change based on speed, since it couldn't therefore constantly observe the sky from a constant point.) If you compared it with a s
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Time cannot go backwards because time, as an independent phenomenon doesn't exist. The passage of time, and what enables "change" is the expansion of the universe. It expands slower or faster near or away from the influence of gravity as time passes faster or slower near or away from the influence of gravity. Time and space aren't simply "relative". The are the same thing. Entropy is strongly correlated but not actually coupled.
That's an interesting theory. I eagerly await your paper to see the math behind it or your science fiction novel, whichever you are attempting to support.
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(Apologies for the simplification, but really you know what the particle was at t-1, t-2, t-3, so you know how it behaves when running time backwards, so you have proof that particle physics in broken, not proof of the arrow of time! FFS logic 101!).
At any moment t, the particle behaves in manner a, so while t-1,t-2,t-3, may appear to show the particle behaving in a manner b, when those prior times were the actual times the particle would have still acted in manner a. If somehow, our observation of past t is different then current t, then something else must have occurred that we are not aware of, possibly entangled particles or even the act of observation.
Simple Explanation (Score:2)
Because GP (and some physicist) think that if particle physics correctly describes matter/anti-matter....
Whoa there it is a LOT simpler than that. If you have a system in state A and it changes into state B then your process is A-->B. If you reverse time then the process you have is B-->A. Now if both these states have identical entropy there are no phase space arguments to favour one state over the other and so both processes (A-->B and B-->A) should be equally likely if the laws of physics are the same with regard to the direction of time.
What these experiments showed are that for some system
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The article is wrong when it says that the laws of physics work the same going forwards or backwards in time. They do not and there is data to prove it. So the 'arrow of time' does not need any entropy to define it - it is baked into fundamental particle physics.
While I don't doubt what you say, I am curious how would there be data to show physics working backward in time? How would you even test for something like that?
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I think the article is referring to time-translational symmetry. Which is what results in conservation of energy. If you claim that time translational symmetry is violated, then you are also claiming the violation of the conservation of energy. Although nothing forbids either, but it would have been big news. And I haven't heard it!
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http://subbot.org/coursera/big... [subbot.org]
Dark Energy and the Big Bang are violations of energy conservation laws.
Conservation doesn't necessarily hold in General Relativity, either. Where does the energy of red-shifted photons go?
Time travel (Score:5, Funny)
The meeting location will be posted next Wednesday.
Re:Time travel (Score:4, Funny)
Boring. I might head there next week-end if I can bother, or maybe the one after. Time travel means I can procrastinate indefinitely.
Re:Time travel (Score:4, Funny)
The guest speaker was half dead from temporal lag and the symposium got over scheduled, twice!
Don't even ask about the Parallelers. Ack!
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I'll go the first time, and afterwards, if it was boring, I'll just stop by myself before I go and tell myself not to go at all. Problem solved!
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That always seemed like a radical stretch to me - I mean every particle in your body is already identical to every other particle of its kind in the universe, what difference would it make to the physics of their interaction if some of them had traveled through time? You might do strange things to sequential causality, but to date we have no conclusive evidence that such a thing even exists as anything other than an observer phenomenon.
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Don't bother, it will have been boring.
No, that's the tunnel driller's association meeting, you're thinking of.
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Don't bother, it will have been boring.
I was the only one there, but I found myself to be quite entertaining.
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Boring. I might head there next week-end if I can bother, or maybe the one after. Time travel means I can procrastinate indefinitely.
"Time Machines Repaired While You Wait"
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For those interested in time travel, the inaugural meeting of the International Time Travel Association will be held at the Perimeter Institute last Tuesday at 20:00. The meeting location will be posted next Wednesday.
You've got this completely wrong grammar-wise!
"The main work to consult in this matter is Dr. Dan Streetmentioner's Time Traveler's Handbook of 1001 Tense Formations. It will tell you, for instance, how to describe something that was about to happen to you in the past before you avoided it by time-jumping forward two days in order to avoid it. The event will be described differently according to whether you are talking about it from the standpoint of your own natural time, from a time in the further future
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I was thinking about going, but the reviews will have been mixed.
Huh? (Score:1)
Can someone translate this for me (in American English) in four sentences or less what this is about, and more importantly - what it means to me?
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This means the timecube is real!
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This means the timecube is real!
Now I can die a happy man.
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This means the timecube is real!
I can't even find a flashcube.
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Re:Huh? (Score:5, Informative)
I read the linked article, but not the original paper, and here's my summary (sorry for not limiting it to four sentences, but I can only do so much):
One of the outstanding problems of physics is to explain the directionality of time. It's easy to distinguish the future from the past, even though the fundamental laws of physics operate the same forward and backward. This "arrow of time" is normally explained in terms of increasing entropy, but that doesn't answer the question of why the universe started out in a low entropy state.
The researchers here made a computer simulation of a simple system of particles interacting with gravity, and a metric of entropy based on how close the particles were together. What they observed is that gravity can (briefly) pull the particles together into a low "entropy" state. You can then post-rationalize this as having a single low-entropy "starting point", from which you get two high entropy "futures", which consist of earlier and later states by external simulation time. But both would be "future" according to a creature living in the simulation, seeing the entropy increase as one moves away from the "big bang". It's the whole "what is north of the north pole" thing - if you walk north toward the north pole, you eventually start heading south, even though you haven't turned around.
The researchers claim that it's gravity which is the key to giving you this starting point, but other researchers quoted disagree, saying simply that having an entropy metric which doesn't have an upper limit is sufficient to give similar behavior, and claiming they'll be publishing a paper soon which will show this.
What does it mean to you? Nothing, really. It's still rather preliminary and esoteric at this point. Maybe in another few years they'll be some science special on TV which will discuss it in a "isn't science mind-boggling?" sense. It (or rather similar such arguments) will eventually inform basic theories about physics and how the universe works, but right now it's not even at the "one day sir, you may tax it" stage.
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Fair summary.
Alternatively, time itself does not have an arrow and that is introduced only by the presence of observers.
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People assume that time is a strict progression of cause to effect, but *actually* from a non-linear, non-subjective viewpoint - it's more like a big ball of wibbly wobbly... time-y wimey... stuff.
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Time flies like an arrow. Fruit flies like bananas.
Don't leave your clocks sitting out or they'll draw bugs.
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Sometimes this faith involves an old white man with a beard.
Santa?
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Sometimes this faith involves an old white man with a beard
John Travolta?
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Sometimes this faith involves an old white man with a beard.
Darwin? <ducks>
Article Venue (Score:5, Funny)
I *refuse* to read science articles unless they are dumbed down, explained with barely-relevant images, and posted on medium.com!
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I'm curious, would a wall of equations make you happier?
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In that case one might be in for a disappointment. The article[1] seems to only contain about a page worth of equations.
[1]: http://arxiv.org/abs/1409.0917 [arxiv.org]
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If you can explain the disorder, haven't you created a meta-order that formally describes the disorder? What is the limit on the creation of such meta-orders?
The actual scientific article (Score:5, Informative)
The actual scientific article was published on arXiv [arxiv.org] in september. Gravity does not appear to be central to the problem, it is just used as an example here. They basically look at a toy problem where a large set of particles with simple interactions give rise to solutions where they can identify variables that increase monotonically away from a minimum, and hence can be used as a time variable. It is basically an entropic argument worked out in detail for a simple system.
Carrol et al have published related ideas [arxiv.org], and here is a popular science talk [youtube.com] by Carrol (the main argument starts around 19 minutes into it).
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Actually, you'll have to watch part too [youtube.com] also to see the whole argument.
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Right now, our model of time is an arrow. Check back when our model is closer to a big ball of wibbly-wobbly, timey-wimey... stuff.
The thermodynamics explanation is circular (Score:3)
Entropy requires time in which to move to a more disordered state.
Time exists because entropy becomes more disordered.
Hmm. Spot the logical flaw there.
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Entropy requires time in which to move to a more disordered state.
Time exists because entropy becomes more disordered.
Hmm. Spot the logical flaw there.
Ok. Your logical flaw is a strawman argument. While the article claims entropy is responsible for the arrow of time, i.e., the directionality of it, you pretended it said it's responsible of the existence of time at all. Then you argued against your own statement and pretended that was a valid argument against theirs.
Here's what they're actually saying. Assume time exists. So entropy can either increase or decrease with the passage of time. However, there are many more configurations with increased en
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By that definition, the hard drive on a computer increases in entropy when they make bigger ones. But we want more entropy then, because we can store what we choose on it. We don't have to limit ourselves to the disordered states.
So the identification of entropy with "everything falls apart" is misleading. More entropy serves us in many cases: a zipped file has less entropy than the uncompressed version, but we can't read the zipped version. In computational linguistics, maximum entropy models are useful.
Ju
The big crunch (Score:2)
This idea is not new... they don't say it outright, but I believe they are suggesting "The big crunch" and the endless cyclical universe. Basically the Big bang was a point in a cycle. There was a universe that "Crunched" into a point like state and then exploded into our universe. But that other universe had time flowing in the other direction. If true, I suspect they're suggesting that the big bang was just one point in an endless cycle of expansion and contraction... though you should take care no to thi
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" It suggests the Hindi/Buddhists are onto something. ;-)"
Hindu is the religion, Hindi is the language
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" It suggests the Hindi/Buddhists are onto something. ;-)"
Hindu is the religion, Hindi is the language
I thought it was plural of Hindu? Huh... learn something new every day. My apologies, I haven't been to India.
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I agree, I always liked that idea, but it doesn't appear to be the case. Dark energy is accelerating the expansion of the universe. Gravity isn't slowing it down eventually leading to contraction. It appears we are doomed to expand until nothing is within the light cone of anything else.
The future is very cold, dark and lonely.
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I agree, I always liked that idea, but it doesn't appear to be the case. Dark energy is accelerating the expansion of the universe. Gravity isn't slowing it down eventually leading to contraction. It appears we are doomed to expand until nothing is within the light cone of anything else.
The future is very cold, dark and lonely.
We don't understand Dark Energy/Matter... so I reserve judgment there. We have no idea what will happen when electrons have been stretched to the size of galaxies. It may very well be that it triggers a phase change and reverse time. Who knows?
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While it certainly isn't impossible (the universe is full of strange stuff) that would be rather unique. I can't think of any other forces that have a "phase change" and are attractive at some point and switch to being repulsive at another (electric repulsion doesn't count...it doesn't change).
That said, dark energy is truly bizarre. It appears to be a perpetual motion machine, pushing things apart constantly with no power input. I know it can be said that it doesn't really apply a force because it appears
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I don't believe in Dark Energy/Matter, any more than I believe in C/C++. Those are four separate things, with Dark Energy and Dark Matter related something like Java and Javascript.
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I've long thought that gravity and time are forces, like magnetism and electricity, and need to be unified.
If only someone had thought of doing this before. Your totally original idea of a Unified Field Theory could have revolutionised Twentieth Century physics.
Movement in space creates time. (Score:2)
I always thought this to be quite obvious once I though about it for a little while. ... I came up with this at about the age of 9. Since then I've been doing fine with that answer. Couldn't say if science found anything new, but I really don't care. That philosophical answer (I suppose it is one) is sufficient enough for me. :-)
You need space, matter and movement.
Those together create what we call time, when we observe it.
All four of those are interdependent.
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You make it sound as though we perceived the world like still frames in a movie, one after the other in sequence.
Time is an Art (Score:2)
If you are someone who researches the financial markets, there was a famous trader going back to the late 1800s named W.D. Gann. Gann's analysis of time was always that it was a subjective, illusory edge with respect to defining market movements, but that the definition was quantifiable at the highest of levels. In my book, "The Market is not Random.," [tminr.com] I explore this subject more and think it is relevant for this conversation.
What's more, I think this article's timing is perfect with the recent theatrical
It Works For Me (Score:2)