Image: Kenn Brown
In Brief
- The basic laws of physics work equally well forward or backward in time, yet we perceive time to move in one direction only—toward the future. Why?
- To account for it, we have to delve into the prehistory of the universe, to a time before the big bang. Our universe may be part of a much larger multiverse, which as a whole is time-symmetric. Time may run backward in other universes.
More In This Article
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Sidebar
Time's Arrow FAQs
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Sidebar
The History of the Observable Universe
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Infographic
Entropy in the Kitchen
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Infographic
What Gravity Does to Entropy
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Infographic
Restoring Symmetry to Time
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PDF
Scientific American','WT.dl','1','WT.ndl','1');">"The Arrow of Time" feature from 1975 issue of Scientific American
The universe does not look right. That may seem like a strange thing to say, given that cosmologists have very little standard for comparison. How do we know what the universe is supposed to look like? Nevertheless, over the years we have developed a strong intuition for what counts as “natural”—and the universe we see does not qualify.
Make no mistake: cosmologists have put together an incredibly successful picture of what the universe is made of and how it has evolved. Some 14 billion years ago the cosmos was hotter and denser than the interior of a star, and since then it has been cooling off and thinning out as the fabric of space expands. This picture accounts for just about every observation we have made, but a number of unusual features, especially in the early universe, suggest that there is more to the story than we understand.
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76 Comments
Add CommentThe statement that we think of time as moving forward is very challenging because 'time does not move at all. Time is only a dependent attribute, resulting from any change of state or change of position. At the extreme, if all matter in the universe was at absolute zero can time exist?
Reply | Report Abuse | Link to thisWhy is a black hole the "highest amount of entropy that can be confined to a given volume"? Why isn't a black hole a LOW entropy state? Aren't black holes sometimes called "singularities" because all the particles within it are compressed to something approximating a point? Doesn't that imply uniformity, i.e., low entropy? Can someone help me out here?
Reply | Report Abuse | Link to thisAnother possible explanation: maybe the past was special and unique. All that is required for this is to postulate a First Cause. Let me posit one: God. Not a claim here, just an hypothesis, valid as any other.
Reply | Report Abuse | Link to thisUnderstanding time in its totality, especially when we look at knowledge economics we see that time indeed even moves backwards on our earth and is relative on our planet. Less developed countries are in essence though in the same year are in essence behind in time, Some students grasp phenomenon quicker than other students, they are ahead in time in terms of knowledge e.g. 12 year olds who graduate high school at the same time as 18 year olds. Indeed time is lost, take the water pump discovered by Romans lost and rediscovered by a dutch man in the 17th century, time is not constant with humans traveling faster, slower and being lost, just giving you the perspective of a knowledge economist. time a fascinating topic.
Reply | Report Abuse | Link to this1) Does the fact that our mathematical basic laws of physics are time-symmetric really imply that reality should be time-symmetric as well? After all, these laws are merely working models developed to describe reality as accurate as possible and should not be identified with reality itself.
Reply | Report Abuse | Link to this2) Does it make sense to state that the experimental observation that the entropy of an isolated systems tends to increase (2nd law) is related to the gradual collapse of the quantummechanical wavefunction for that system or in other words that the "arrow of time" is related to the tendency of a system to gradually move from a superposition state to a completely collapsed state or in other words that what we perceive as the direction of time is closely related to the gradual branching of reality? If this is so, does it make sense to say that the problem of the time-asymmetry of reality is closely related to the central problem of quantummechanics, i.e. why does the wavefunction collapse at the time of measurement?
3) Also, in my opinion, the popular definition of the second law of thermodynamics featured in the article should read: "entropy in an isolated system never decreases", since by its very definition a closed system is able to exchange energy with its surrounding.
The author goes to much trouble to keep the universe natural - perhaps ignoring the very possibility his work illuminates. Is it too distasteful to even consider that this universe is artifical? Given sufficiently advanced technology, we might be able to create the low entropy initial condition and make our own tiny version of the universe (didn't I see an article about that recently right in these pages?). Perhaps someone(thing) else has already beaten us to it? Maybe everything we can experience is little more than someone's experiment. If they are in a time-neutral or omnidirectional universe, then this is not so far fetched. Perhaps they can move to any part of our 14 billion years at will, observing from the outside (don't as me how - they can create universes!) how things have changed in our unidirectional universe here?
Reply | Report Abuse | Link to this"Gravity causes particles to clump into stars and galaxies, and entropy increases noticeablyconsistent with the second law." Is this correct? Imagine a small system with 4 particles on a grid 6x6. There are 33929280
Reply | Report Abuse | Link to thisstates (arrangements of the 4 particles) possible, by my figuring. If the particles are clumped into a square 4x4, there are only 25 states. Clearly the entropy is higher in the unclumped situation. The clumped situation seems to correspond to what happens when gravity draws particles together, thus gravity would seem to reduce entropy. What am I missing?
The given explanation of time only explains that when the universe evolves it evolves into disorder, it does not explain why it evolves at all. An explanation of time has to explain what change is, not how it is. Obviously, given the laws of probability and given that things change, they should change towards the disorderly. But this does not explain that they change, i e why the universe is not static.
Reply | Report Abuse | Link to thisur thoery may be trueand i think that after 10 years we would get real thoery about time
Reply | Report Abuse | Link to thisshreya
Two problems with your analysis: (1) assuming it is possible to unambiguously assign a time value to the universe as a whole (an ordering of events); (2) assuming that time is necessarily linear. Both assumptions are questionable, one is (arguably) ridiculous.
Reply | Report Abuse | Link to thisIt is very difficult to prove the arrow of time. Nature seems to resist all efforts to apply the human notion of time or even it's existence. SA needs to do an article that rejects time outright and look at the universe with just the notion of "now" - no past or future (the past resides in human memory, the future is human imagination). Strip time out of the universal equation and what do you get? Change. Things change and are different only because of normal system decay. We are too caught up with "flows" and point A to point B mentality. Circadian rhythms are almost impossible to move away from mentally. Drop the time illusion and I bet the universe will be more than happy to reveal all her secrets.
Reply | Report Abuse | Link to this--
Edited by Peter Lego at 05/22/2008 5:54 AM
yep. Not getting it either. How can on one hand say the the pre-universe was had all the matter that exists today compressed into a homogeneous box the size of 1cm3 and have low entropy, but a black hole that has 100s of solar masses squeezed into a box the size of my car have high entropy?
Reply | Report Abuse | Link to thisThe idea of entropy that comes up in information theory is analogous to that in physics and is basically defined as the amount of uncertainty in a system.
Reply | Report Abuse | Link to thisIf you think of entropy in this way, it makes perfect sense that a black hole maximizes entropy because we can know nothing whatsoever about its internal states, so uncertainty is at a maximum.
If it were a low entropy state we would have little or no uncertainty about it; we'd be able in principle to learn most everything about the internal states of the black hole.
To the question of why gravity, by clumping matter, doesn't reduce entropy, I believe the answer is that the ever increasing expansion of the universe "thins out" matter and thus increases entropy. The further things get apart, the less the pull of gravity.
Reply | Report Abuse | Link to thisBut the question of what is time can be addressed by realizing that there are two universes: a physical one and a mental one. They interact continuously, but the mental one has no time. The fact that two plus two equals four is not subject to dilution with the passage of time. My favorite quote on the subject is this';
God invented time so that everything wouldn't happen at once.
Dorothy van den Honert
Time is a human construct born of our subjectivity. The universe is time independent. Duration of phenomena is more accurate. And "duration" does not "run backward". Einstein introduce the subjecting in the relativity, but, reality is not relative. Reality just is regardless of any observer. Thus, the search for the beginning of time is a search for the beginning of subjectivity, which is pointless. The universe is. It is more than we can ever know, and it is much more complex than our pretentious theories can hope to explain. Better to figure out how to live in peace on our little dung heap.
Reply | Report Abuse | Link to thisAre the owners and editors of this magazine aware that an article such as this puts rational-minded people off?
Reply | Report Abuse | Link to thisHow far are you prepared to allow profit-seeking populism to erode SciAm's image as a high-quality science magazine?
A couple of comments:
Reply | Report Abuse | Link to this[b]For Befell:[/b] At the risk of appearing politically incorrect, within the context that you use the phrase "rational-minded-people" a better word would be "retarded". Retarded because the type of people you cite are backwards, stick-in-the-mud types that throughout recorded history have always stood in the way of technological and scientific progress. They're the same ones that said the world was flat, that man would never fly, that we would never get to the moon. The same that persecuted the great scientists of the renaissance and who mocked the Wright Brothers. In short, the so called "rational-minded-people" should not only be "put off" but perhaps even [i]put away[/i], figuratively speaking. In other words, confronted, challenged, and chagrinned to the point that they realize that they don't make this world go around, they have only been the ungrateful beneficiaries of it, making use of the advancements that they once ridiculed after they have been established by the blood and sweat of their betters.
We stand at this juncture where ideas from science fiction are our next frontier of advancement, much like it was at the beginning of the last century. However, unlike the beginning of the last century, the specter of so-called "rational thought", i.e. pseudo-skepticism, is more entrenched than ever before. Fortunately, by the very organizational process through which skepticism operates, it is its own worse enemy, in that it produces an inherent intellectual weakness that is masked by assumptions hidden from it adherents but quite obvious to those of us who have studied it.
Scientific American should be commended for running articles that challenge our minds and the limits of our technology because that is the only place left to go. As for the rational-minded-people, I am developing a campaign that will meet them in the arena of ideas and teach them just how irrational they have always been.
[b]For TheEye:[/b] Duration is only one aspect of time. Relativity theory has been demonstrated with atomic clocks, so it is a part of reality, and not just determined by observers.
The arrow of time comes from a simple fact. Time only exists when a force is applied over a distance. Since neither of those quantities can be negative, time has a positive constraint for any act.
Reply | Report Abuse | Link to thisI think TheEye said in the perfect words what my slightly autistic but unboundedly curious mind has concluded for myself prior to this article. It would have taken an essay to said what he/she said in a paragraph, props. But I see it the exact same way.
Reply | Report Abuse | Link to thisI think our short life span as humans has fueled and perpetuated the concept of time that it seems the average layperson has. Namely that it is some mystical governance, a law, even one that may eventually be manipulated. I guess we all thought of it like that growing up. Back to the Future anyone? Time is because things are, and things pass, either away or into new things. And that's it. Phenomona occurs, endures, and than fades, either away or into something new. This process cannot be reversed.
Saying that in literal terms some developing countries are behind in time on our planet because of the earth rotation is equally childishly speculative. That holds literally true only when you follow human created time zones that map a cooperative world time and day/night cycles
All in all, I think these articles are healthy for some, but many of SciAms articles make for reading that belong to lesser institutions.
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Edited by jcam88 at 05/23/2008 6:13 PM
Point for you debating the importance of "rational-mindedness;"
Reply | Report Abuse | Link to thisScience is itself rational. In essence, it's the human endeavor to see and understand the universe surrounding him with the utmost reverence for encompassing truth, understanding, and more specifically, doing so within the limits of observation. It's a literal way of seeing the universe and as such, it has strict rules with which it regulates itself as a body. What do you have when you don't have these strict guidelines with which to observe? Well for one, you have Creationists. The dangers are thus now understood in full capacity, are they not?
Do not misunderstand. As humans, we can sometimes only theorize. Yet we even do this by observing certain "laws" or rules nature plays by. For example, we have certain theories about how planet and stars and solar systems form, even though we can never observe as it happens literally (space is so vast by the time the light of a phenomon gets to us it's already no longer true. Also, we are limited by the very set of eyes nature gave us. We can never see the Universe outside of our literal pupils and what they can observe. There is so much may be going on in space we just as a species possibly just can't detect or observe. There's your alternate dimensions and the list goes on...) and every other year phenomena that defies explanation shatters the current models for understanding we have. Physics is on the threshold of one of these transformations as we speak.
Thus, Science is. It is the continuous pursuit of this understanding we seek. Always obsolete as soon as it's printed or typed or read or learned. Because there is never an end to the vast knowledge Nature has locked with herself.
Speculation and theories and a little imagination are to be encouraged, but one would say there is a fine line between informed intelligence and blatant over-imagination. If only there were agreement on where this line fell. Oh wait, there is. It's the Scientific Method. Respect it, or walk the way of Chaos. Hey, sounds kinda familiar.
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Edited by jcam88 at 05/23/2008 6:55 PM
I do not understand why it is necessary to posit other universes to explain an intial condition of low entropy. If it is admitted that eventually the milk molecules will separate from the coffee, they will do so given an infinite amount of time. Might one not assume that given an infinite amount of time that the dispersed energy and particles across the low entropy universe will collect to create the initial conditions that gave rise to the big bang? Of course, it is extremely improbable that at any given time that the universe with be in a lower entropy state, but with an infinte amount of time do not all logically possible things happen? The fact that we are living in a time of such improbably low entropy can be explained through the weak anthropological principle.
Reply | Report Abuse | Link to thisSomebody please correct me if my logic has jumped the track.
> The arrow of time comes from a simple fact. Time only
Reply | Report Abuse | Link to this> exists when a force is applied over a distance. Since
> neither of those quantities can be negative, time has
> a positive constraint for any act.
W=F*d
F=m*a
a=d/t^2
since sqrt of t can be + or - your theory is off.
For jcam88:
Reply | Report Abuse | Link to thisDebating "rational-mindness" is simple. What is rational has nothing to do with "truth". You say science is "rational", I say it's not because what is rational is a subjective, psychologically driven statement and has no bearing on conducting real science. Slavery, eugenics, and Nazism have all been considered "rational" based upon the biased criteria that was used to argue for them and ultimately enforce them. It was considered rational to think that the Earth was the center of the universe and that the world was flat. The claim that science is [i]rational[/i] is the false usurping of science by the weak minded and the inspisrationally challenged. Science should be about measurable and reproducible outcomes and theories that could lead to such experiments. Those that lay claim to science for the sake of rationalism are only carrying water for those who ultimately want to control and censor science. It's a historical fact.
It is also a fact that all theories that claim that time is nonexistent can be shot to pieces, in many cases because they rely on rationalism and not science, on philosophy and not experiment, and on psychology and not physics. That's just the way it is.
I loved the easy reading and understanding of this article. Great job!
Reply | Report Abuse | Link to thisTime is a measure, to think of reversing events as an effect of time is a misconception. Time is a measure of the beginning through to the end; being as the universe has not yet ended it can be said that the first second of the clock has not yet gone from tick to tock. What we experience is within the yet ongoing event of the universes beginning.
Reply | Report Abuse | Link to thisThere is already a quantum theory of gravity by Vasily Yanchilin. For short compilation in dutch language see www.janjitso.blogspot.com.The Russian scientist argues that reversal of time is impossible. He explains that at the edge of the universe everything looses qualities like speed and direction because c, which is related to the potential of the total mass of the universe, drops there to zero.
Reply | Report Abuse | Link to thisI suggest to call this a sea of iets. Which has very low entropy. In such a sea of iets an Initiative from Outside (God's finger) may create one or more (simultaneous, no inflation needed) Big Bangs, comparable to a foton hitting an electron and reducing its Heisenberg dimensions to almost a point.
The problem with the big bang theory is that sees time in a straight lineal pattern why not consider that time might be in wave length or sliced up dimension and that the universe its still being born as we speak or being renew in different part of its dimensions the scientist make mistakes when they try to deal in the absolute.
Reply | Report Abuse | Link to thisMr. Carroll you assume that time moves in a straight line, but that's not certain. In space time might move in wave length or dimensional slices or any other way that at this moment none of the scientist are 100% sure. The Big Bang Theory also has a lot of explaining to do, because is base on a lineal time continuum and because we really don't know how time behave in space this Big Bang Theory is flaw we should never be persuade to deal in the absolute, we must study and observe the universe more carefully before come to any substantial conclusion. Arysgad
Reply | Report Abuse | Link to thisIf time moves backward in a universe that is contracting, is this just the cosmological arrow of time or would the thermodynamic arrow of time also move backwards? In a collapsing universe, if we could observe the details, would ordinary events seem to run like a backwards movie? I am told the cosmological arrow relates to the expansion or contraction of the universe only, and the thermodynamic arrow relates to our personal experience of past and future.
Reply | Report Abuse | Link to thisI am also told that they are not necessarily pointed in the same direction - and I'm not sure if this Mr. Carroll's view.
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Edited by dgroberts at 05/28/2008 6:01 PM
uh... I'm not a big expert on anything really, but it seems to me that time is really just an abstract measurement of duration between arbitrary events a measurement based on a specific arbitrary rhythm.
Reply | Report Abuse | Link to thisNot an actual presence or force of the universe. I mean aren't other forces are at work, ones that make the time evident to a human observer? I've never seen time at work, but I've seen gravity, heat, magnetism, sound et cetera, and even though I've measured things through the use of time, like a meter, or a mile, I've never really seen one. (a time) Maybe I'm just confused.
Which direction do we look to see the past? If you can look any direction, far enough and see our origins, what does that say of our location in time? If we look in one direction primarily then things are more linear and understandable. If you go halfway to the past in one direction how was that place not equally far from the origin that we must share (in the big bang theory of time)?
Reply | Report Abuse | Link to thisNo. "Forward" is by definition the way time runs - even if this direction in another universe is the opposite of ours. But I think the question is meaningless as long as we don't have a proper explanation of what time is. Saying that 'it is subjective', as some say, or something like that doesn't cut it, IMO.
Reply | Report Abuse | Link to thisWhat we need to explain is why one dimension is special, or perhaps equivalently, why we have such a curious metric. My own wild guess is that since time seems intuitively to have something to do with "logic", in as much as in physical phenomena cause always comes before effect, maybe a good model of time would involve a representation of an elementary topos into a manifold.
Another thing that needs a proper explanation is: what is a particle? As it stands now, all the explanations seem to be some thing like "little hard lumps of stuff", a concept that is hard to fit into a smoothish manifold like our spacetime.
The sequance of linear Time is only a model for expaining mechamical features but this model it is not more useful for inerpreting the self-organization phenomena including life.
Reply | Report Abuse | Link to thispaolo manzelli pmanzelli@gmail.com
www.egocreanet.it
www.wbabin.net
www.edscuola.it/LRE.html
I have proven repeatedly that time does run backwards in my universe-- unfortunately the boss says I still have to be on time for work
Reply | Report Abuse | Link to thisI think fall into the category of- if a tree falls in the forest and no one is there to hear it does it make a sound. The answer is purported to be that if there is no one there to receive the sound transmission then no.
Reply | Report Abuse | Link to thisMy understanding is that time is the measure of the movement of consciousness. If there is no one there to perceive the consciousness moving then time is non existent therefore cannot move in any direction. Furthermore if we (I) was there then the consciousness that would be experienced would be moving in the direction that we could comprehend and even if it was moving backwards it would appear to us as though it was moving in a way that our consciousness understands which would not be discernable as being backwards.
My point is that if the (or a) Universe or universe is collapsing, the cosmological arrow of time is pointing backwards by definition. That might not effect the thermodynamic arrow of time - which humans experience.
Reply | Report Abuse | Link to thisI am told that there is no way that a human or any other local effect would know if the Universe was collapsing or expanding, and the local experience of time would be detached from the expansion or collapse of a universe.
If this is true, time running backwards in the context of Mr. Carroll's article means that the universe in question is collapsing, but not that time as we would experience or observe it would be any different.
But, I'm a layman. So, I await correction by wiser men (or women).
Sean Carroll's article relates the direction of time to entropy which is a measure of the state of a system. As a model this may be constructive for cosmological theory, but it seems to me that something vital and basic was left out of the discussion: causality. If we have a large mass on a pedestal high above the ground and suddenly a meteor arrives and breaks the pedestal, the mass will fall to the ground. When this happens the entropy may change, but that would be missing the point. Similary, if a photon arrives from some star in the Andromeda galaxy and excites a pixel in a telescope photocell, exciting that pixel will not cause a photon to be sent to that star in Andromeda, and I know of no law of physics predicts that it would. So, while it may be true that formulas which include the time variable t inpose no constraints requiring t to increase, the point is not the variation in t, but the underlying events effecting the changes described by the formalu.
Reply | Report Abuse | Link to thisI enjoyed Kip Throne's book, [i]Black Holes and Time Warps[/i]. In it he describes a thought problem.
Reply | Report Abuse | Link to thisYou are located at one end of a room, on the far end in front of you is an object you must reach. The problem is you can move freely except you can't, from your reference, move forward. So how does one get to the object in front of them?
The answer is to rotate. You turn so that the object is no longer in front of you.
This problem really parallels what we experience with space and time. We can move freely in all the spacial directions, but only in one direction in time. So in order to solve this problem we rotate with respect to space and time such that we have freedom of movement on what was once the time dimension. But it is always easier said than done.
With our, (i don't want to say universe because that implies only one, ever) reality we have an absolute time outside of observation. This is due to the fact that c, the speed of light in a vacuum, is a constant. Since a velocity is distance over time, c*t can equate to the 3 spacial dimensions.
The Heisenberg uncertainty principle does show that at very small distance and short times these absolutes break down.
Personally, I like the idea that our universe will expand to the point of being a vast empty space until some yet unknown mechanism (dark matter?) will cause it to instantly compress into a small 1 centimeter ball of energy that will explode into a new universe. That dark matter might act like some kind of rubber band; at some point the normal matter runs out of momentum and stop stretching the universe, then the dark matter takes over and contract the universe back to pre-big bang conditions.
Reply | Report Abuse | Link to thisTime is the measurement of the gradual decay of the universe and we have allocated dimensions to this decay.
Reply | Report Abuse | Link to thisTime has more than one dimension. Akin to speed and acceleration, best to visualize time as a point on a wheel as it rolls along. This gives Time the property to oscillate, in a wave-type manner, as the point goes retrograde during the wheel roll. In doing so, it "solves" the problem of one particle going through through two separate pathways at the same time. Also, by giving time more than one dimension (3), this recognition helps string theory calculations.
Reply | Report Abuse | Link to thisJ.K.
I read with fascination Sean M. Carroll's article on the arrow of time in other universes. It prompted me to wonder about a couple things:
Reply | Report Abuse | Link to thisQuestion 1: I've heard it said that, relative to us, time halts at the event horizon of a black hole, and in fact, goes backwards within a black hole. Should we then observe (if possible), entropy decreasing in a black hole?
Question 2: In the article, Carroll writes: "Any beings who lived in one of these time-reversed regions would not be born old and die youngor anything else out of the ordinary. To them, time would flow in a completely conventional fashion. It is only when comparing their universe to ours that anything seems out of the ordinaryour past is their future, and vice versa.". Are there just two choices for the direction of the arrow of time (i.e. our past vs. our future)? Or, might there be a universe that has an arrow of time that is orthogonal to ours? In that case, perhaps their entire existence would be just a flash relative to us (or ours a flash to them). Is this possible?
Excuse my language but this article is the biggest load of crap I've read in a while.
Reply | Report Abuse | Link to thisIt seems that modern cosmologists and physicists can't think for themselves anymore.
The fact that you "choose" one state, i.e. the early universe as a "special state" is a cultural bias you do not seem to be aware of or care. Each state in the evolution of the universe is unique and therefore cannot be considered as the sole "special priveledged reference state"compared to another.
Intuitively, there seems to be a correlation between what we experience as the arrow of time and the continuous modification of the fabric of space. This continuous modification is the unidirectional expansion or stretching of the fabric of space which has been observed experimentally. I intentionally dont use the concept space-time here for clarity reasons.
Reply | Report Abuse | Link to thisConsider at time t1 a point-like observer A at position (x,y,z) and another point-like observer B at position (x,y,z). Consider the same point-like observers A and B at time t2>t1. Consider that the distance between A and B as measured with a measuring stick is the same at t1 and t2.
Then intuitively it seems that what A experiences as the arrow of time while observing B from t1 to t2 is related to the expansion of the fabric of space since in reality the distance between A and B is not constant from t1 to t2 but increases due to the expansion of the fabric of space causing B to have an intrinsic speed v relative to A. To use the terminology of special relativity: A and B do not share the same frame of reference.
Note that the increase in distance between A and B cannot be measured experimentally by the measuring stick, since the space between the most elementary particles making up the measuring stick is expanding at the same rate.
If now B moves with an additional speed relative to A, special relativity predicts that from the point of view of A, the arrow of time of B slows down. It is as if from the point of view of A, B keeps up with the expansion of space.
Intuitively, it seems that a point-like observer A does not experience the flow of time as long as he reflects on himself. However, while observing another point-like observer B moving at an additional non-relativistic speed relative to himself, the flow of time for B from the point of view of A seems inevitable and unidirectional. In the hypothetical case where B moves at the speed of light relative to A, general relativity predicts that the flow of time for B from the point of view of A stops.
Does this make sense?
Note that for a model to have scientific value, it must be falsifiable (Potter). Nowadays, in physics, an increasing number of models are not falsifiable and are therefore philosophical models rather than scientific ones. Therefore, any model about time and the arrow of time must allow to design and actually conduct experiments that either confirm or contradict the model. As long as such a model is not contradicted by an experiment, it remains a usefull scientific working model.
Reply | Report Abuse | Link to thisThe universe is big and old, that we know. We experience time's arrow as unidirectional. If the definition of universe is "all that there is wherever it is," then the concepts of parallel universes, alternate universes and multiverses are meaningless on their face. This article makes cosmology seem to be a seeker of ghosts in dark corners....
Reply | Report Abuse | Link to thisThe fact that physics seems to be time independent is not in the nature of the universe or of physics, but is in our context and math: think of differential equations where one factor, in this case, time, is approaching the limit of zero -- then you can run the equation forward and back as if there were no difference. However, as we know from differential calculus, the limit never actually reaches zero, so time is always a factor -- it is just not significant in the context where Carroll claims that it is absent.
Maybe the real question that needs to be explored is "Is the universe a closed system and how could we test our answer?"
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Edited by iskeen at 06/04/2008 9:13 AM
> Question 1: I've heard it said that, relative to
Reply | Report Abuse | Link to this> us, time halts at the event horizon of a black hole,
> and in fact, goes backwards within a black hole.
> Should we then observe (if possible), entropy
> decreasing in a black hole?
Yes, my understanding of astrophysics time approches 0 with respect to the outside observer.
It is explained like this:
You have a spacce ship orbiting a black hole. There is an explorer probe sent in relaying information back in some fashion. The information is sent at descrete intervals from the probe and are detected at the ship.
now the probe is always sending out the signal at the same time consistantly, but the recieving pulses at the ship get longer and longer delay has the drag of gravity slows down the signal (or one can say stretches the space the signal has to travel).
Probe send: 1.2.3.4.5.6.7.8.9.0.1.2.3.4.
Ship sees: 1.2..3...4....5.....6......7.......8........9.........0
the probe will never know exactly when it crosses the event horizon, but the ship will never get another signal from the probe.
The faberic of space and time are still within the mathematics of physics up untill the point of the singularity.
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Edited by Chaosqueued at 06/05/2008 3:19 PM
Time, the Big Bang & the `Expanding Universe` are only concepts-they only exist in the mind: everything you see have ALWAYS been here oscillating and spiralling into a timeless matrix of perpetual intelligent flux that we have explained by the notions of Gods.
Reply | Report Abuse | Link to thisSean Carrolls article The cosmic origins of times arrow seems to be based on a critical and unstated assumption, namely that the Second Law of Thermodynamics holds throughout the postulated multiverse. But, other proponents of the multiverse have suggested that physical laws may vary from one universe to another, a conjecture that can apparently never be tested even in theory (at least without appeal to a supernatural or superuniversal observer). One must apparently assume multiversal validity of the Second Law in order to proceed scientifically with this cosmology, but this critical assumption should be made explicit
Reply | Report Abuse | Link to thisDear Iskeen:
Reply | Report Abuse | Link to thisThe definition of the universe that you used:
"all that there is wherever it is," is outdated and is more of a definition of the multiverse. As such, alternate universes are not ruled out and in fact are becoming more and more of an integral part of not only cosmology but quantum mechanics.
As I've stated elsewhere, it is misleading to say that physics is time symmetrical. It is only the equations from quantum mechanics that appear to work that way. One need not even turn to math to prove this point, one only need to look at gravity or more better yet, the physics of stars. At what point does is make sense to see a black hole reverse itself and become a sun?
As it so happens I plan on addressing the idea of what might lie beyond our universe later this year. It is a question that I feel should be addressed instead of accepting the usual answers of "nothing" or "no one knows".
The concept of nested Universes is not very new, it was considered a long ago by many other people, for example here http://www.slovio.com/multi-level-universe/
Reply | Report Abuse | Link to thishttp://superstruny.aspweb.cz/images/fyzika/spaceevol.gif
And this concept is imanent part of Aether Wave Theory, which explains how the process of daughter Universe formation can be observed at the case of quasars and how it's related to foam structure of dark matter.
http://superstruny.aspweb.cz/images/fyzika/spacetime/collapse.gif
By AWT the Universe always exhibits multiple time arrows: by the same way, as the matter aglomerates itself into gallaxies, it's radiated and dispersed into space back via radiative processes like giant condensing and evaporating dropplets or fluctuations of Aether density.
Reply | Report Abuse | Link to thisI found Prof. Carroll's "Time's arrow" article very interesting, but in the end unsatisfying, and I would like to present the following possible model of the universe. To my mind any general theory has to pass what I might call a "simplicity" test (not Occam's razor but similar) - is it the simplest believable explanation? At least two recent books take the current string theory of everything to task on this and other grounds. The theory of the universe I am proposing here is simple, and testable, I believe - I cannot think of a practical test right now, but I would bet that there is at least one. It stems from the premise of the article, and the thought that, despite over a century of Einstein, almost all of us have difficulty of thinking of time (the t-axis) as being a PHYSICAL dimension in the same way as are the Cartesian x-, y- and z-axes. If we do that, then two things become obvious; the t-axis can have a negative as well as a positive direction, and there is no reason for the rate of flow along the t-axis to be constant any more than it is along the x-, y- and z-axes.
Reply | Report Abuse | Link to thisThe first of these leads to a much simpler explanation for the "time's arrow" phenomenon (one that is so simple that it must be wrong or someone else would surely have proposed it already!). It also explains another cosmological puzzle, that of the lack of observable antimatter in the universe.
Suppose time simply flows in opposite directions for matter and for antimatter. Then our universe would consist of two parts, ours and the other antimatter part, which would be in perfect entropic symmetry at all times. (Think how much entropy, never mind the energy, it takes to produce even a single atom of antimatter in our universe. And I have never heard anyone trying to explain the enormous explosions that take place in the far cosmos, gamma-ray bursters and so on, as matter-antimatter collisions.) Both parts of the universe progress in the direction of maximizing entropy. At the "end", when entropy maximizes as "empty space" on one side and as a "singularity" on the other, there is a << discontinuity >> and the system re-configures itself. Thus you have a "bouncing" system, but consisting of only two parts, and always in perfect symmetry in entropic terms.
Some anti-matter particles (positrons) are relatively stable in our part of the universe; presumably some matter ones (electrons) would be relatively stable in the anti-matter part. I have no problem with this; Feynman diagrams are symmetric with respect to the direction of the flow of time, and presumably time would flow in the same direction for positrons as for electrons, etc., when they are in our part of the universe.
As to the second point I make above: it seems to be an implicit assumption by almost everyone that the rate of flow of time in the universe is constant, and has always been the same. Is there any actual evidence for this? (I cannot think of a way to test it, since the phenomenon being observed and the timing instruments used to observe it would be affected in the same way by any changes in the rate of passage of time.) In fact, however, thanks to Einstein we KNOW that time can flow at different rates. Think of the time differences between a stationary object and one traveling at near light-speed; this has been amply verified using atomic clocks at much lower speeds than that of light.
If in fact the rate of passage of time is variable, then a self-consistent universe (i.e. consistent with my hypothesis of a mirror-image matter-antimatter one) would be hyperbolic. Imagine a plot of the rate of passage of time as the y-axis of a two-dimensional hyperbolic graph, and the age of the universe as the x-axis. We would be in the (+,+) segment and the antimatter universe in the (-,-). Initially, for low x-values in our segment time passed very quickly, which would correspond to the "inflationary" period which just about all of the big bang theorists feel is necessary to explain the very early universe. Then the rate of passage of time becomes much slower, which corresponds to where we are now.
Would not this be an alternative (and better) explanation for the conclusion that the rate of expansion of the universe is accelerating, based upon observations of distant supernova explosions in the universe when it was much younger than it is now? (These observations seems to be becoming better supported by newer experimental results.) I would argue that this is in fact the beginning of the sampling of a period in the early universe when time was passing more quickly than it is now. I find that the current theory for these observations, that the rate of expansion of the universe is accelerating, with an explanation in terms of little-understood and unobserved "dark energy," to be unsatisfactory. I think "dark energy," or an Einstein fudge-factor, is unnecessary. (Dark matter, which is used to explain a different observation, that of the behavior of gravity in galaxies, would still be necessary, however.)
This hypothesis of hyperbolic behavior would also account for the logarithmic quality which I feel that time may have, insofar as many universal quantities (and qualities) make more sense when plotted on logarithmic time scales than on linear ones. The differential of an xy=1 hyperbola is just ln y.
So just what is wrong with this theory? Comments please.
Why must everyone look at time as an object. Without humans on this planet, time wouldn't exist. Time is a human invention. An idea. A way to keep track of one event from another.
Reply | Report Abuse | Link to thisSure, if the physics of a universe started in the opposite direction as ours, things would go backwards. But time, as the idea that humans created, would continue traveling forwards.
Water poured from a might start on the ground at T=0:00 and travel back into the bucket as time goes forward, but time did not travel backward, just everything else did, time would still keep track of things the same direction.
i liked reading the article, though it's quite big, still thoughtful.
Reply | Report Abuse | Link to thisTime cannot run backward. The discussion of such arises only by misusing the word. Time progresses from cause to effect by definition. Our understanding of what is "cause" and what is "effect" need not reflect all possibilities. What we call "effect" may in fact be "cause" in another universe. But unless, under a consistent definition of terms, "cause " and "effect" are allowed to be random, time always moves forward.
Reply | Report Abuse | Link to thisIsn't the concept of time one of our ways of describing our subjective relationship to the objective world, rather than being an actual property of the world. And doesn't this refer to the world of classical physics, but not the world of quantum physics. As we record events, the sequence which evolves only after the fact acquires a direction, this being the order of recording. So then asking why we don't have time reversal is equivalent to asking why don't we record the same events but with the order reversed. Is this a well defined question?
Reply | Report Abuse | Link to thisIf the particles come closer under gravity, they will go faster, since they are falling in a potential well. If they collide or clump, they will heat up or release energy in some other ways, increasing entropy.
Reply | Report Abuse | Link to thistime is a man made word how can something go backwards when it doesnt exist?
Reply | Report Abuse | Link to thistime is a man made word i think it doesnt exist so how could a universe go backwards in time ?
Reply | Report Abuse | Link to thisI agree... Tomorrow will never come, today never is, and yesterday never was. Tomorrow's, yesterday's, yesterday's, tomorrow is today. Therefore nothing. As i'm sure previously posted, time is just a concept we use to "compare" two points that have happened and/or will happen.
Reply | Report Abuse | Link to this(sorry i know it sounds stupid but hey i'm 13)
Time. /My opinion./
Reply | Report Abuse | Link to this========.
There are two kinds of time:
a) the proper (individual) time and
b) the planetary time.
They are so familiar that we rarely give them thought.
Don’t we know, that time for living being is limited
and the planetary time is absolute for them ? It is.
Maybe therefore Newton declared that time is absolute.
It “ flows equably without relation to anything external”
he wrote in 1687. But Einstein had another opinion.
He wanted to know: “ Where does the conception of time
come from?”, “ What is the essence of time?”.
And to explain these questions he created two theories:
SRT and GRT and declared that time is relative, changeable.
1.
SRT explains behavior and the proper time of light
quanta /electron. Why do I think so?
a)
One law (postulate) of SRT says that speed of light quanta
is constant c=1. Second law says no another particle
can reach this speed. So there are two incommensurable
quantities. Is it possible to bind them together? No. I was
taught at school from the first class that the incommensurable
quantities cannot be compared. The connection between these
incommensurable quantities is similar to the decision of a
problem: “What will be if the whale attacks the elephant?”
We can see whale in a ocean and elephant in a savanna,
but they never meet and fight in the same “ frame of reference”.
And the same is about light quanta and another particles.
We cannot see them together in SRT. We can meet only the
light quanta in SRT and no other particles in it.
b)
SRT was born from Maxwell's theory and it is a continuation
of the electrodynamics’ development . The electron is a main
and single hero in the Maxwell's theory and SRT. There
isn't the Maxwell's theory / SRT without electron.
It is not correct to compare electron/ light quanta with another
particles (protons…etc) and bodies (billiard balls, satellites,
astronauts, “twins”) because they cannot produce electromagnetic
fields. The electron and the another particles are also incommensurable
quantities. They are absolutely different objects.
c)
Every epoch has its own delusion. Maxwell and Boltzmann
tried to explain electromagnetic fields using balls, wheels,
cog-wheels, springs…etc. H. Hertz, who demonstrated the
existence of the electromagnetic waves, wrote that the
electromagnetic waves didn’t have practice use. Etc….
Now we try to compare electron/photon
ability with astronaut’s and “twins’ ” opportunities. It is mistaken,
but what to do? We do it because this is our way of cognition
:” From vague wish to the bright thought”.
2.
So, how SRT explains time from electron/ light quanta point of view.
a)
When light quanta is in state of a rest its time is frozen,
and its own clock shows zero.
b)
When photon moves with constant speed c=1
its time is also frozen, and its own clock still shows zero.
c)
Only when photon moves with speed c>1 its zero time
changes and limited time appears. In this situation we
know photon as an electron. Photon works as an electron
and SRT explains this process.
d)
And when , for example, electron emits from an atom and
interacts with Vacuum all its parameters change. Its limited
time ends and its own clock shows zero again. Now it lives
in infinite/ eternal Vacuum until new incarnation, until its new
work, maybe, in an atom (molecule), or in a cell, maybe, in a blade
of grass or in a tree, maybe, in an animal or in a person.
In another words:” We are living beings until Light quanta/
Electron is present and works in our body.” Is it true? Why?
Because W. Pauli in 1924 wrote:" Each quantum state in the atom
is not limited to two electrons, but only one electron".
It means in the atom can be only one, single electron.
The electron manages the atom. If the atom contains more
than one electron (for example – two), this atom represents
“ Siamese twins”. Save us God of having such atoms and cells.
And the living being begins its life from one, singe cell.
e)
Trying to understand “ the electrodynamics of moving bodies”
Einstein wrote that it is the result of time and space changes.
It is not exactly correct , because these changes are secondary
in SRT. And the first point of SRT is that light quanta changes
its spin. The former Planck/ Einstein’s spin (h) changes in Goudsmit /
Uhlenbeck's spin (h = h / 2pi), and as a result of this act all its parameters
change and the time and new space appear.
3.
GRT explains the conditions of gravitation and the secret of
planetary time. Why do I think so?
a)
When Einstein worked on GRT, he asked astronomers:
“ What is the average mass of matter in the Universe?”
The result was lamentable. The quantity of mass was
insignificantly small. It was impossible to keep gravitation
law with such insignificantly little mass and so, the Universe
must be “open”, endless. But what to do with the infinite
space, Einstein didn’t know. Therefore he took (from the
heaven) “ the cosmological constant” in order to “close”
the Universe. The taken mass was enough for creating the
condition of gravitation. Without “ the cosmological constant”
the Universe is endless.
b)
In 1922 Friedman wrote, that we could not take “ the
cosmological constant” in calculation. Instead of it, it is
enough to take “time” and the Universe will be “closed”.
Friedman was correct, but why? Because “time”, by its
nature, is a limited physical quantity and, be taken in
mathematical calculation, automatically gives “closed” result.
c)
So, the detected material mass of the
matter in the Universe is so small (the average density
of all substance in the Universe is approximately
p=10^-30 g/sm^3) that the gravitation law doesn't work.
Astronomers and astrophysicists know about this fact and
therefore (to save the gravitation law) invented new matter
a "dark matter", a new energy a “dark energy” and another
abstract objects. This “ invention” is only a result of our
mentality , which says: ” If in a theory you meet infinity it
means the theory is nonsense”. It is very hard to take that
the Universe is infinite. It is no easy matter to give up
a lifetime of habit .
d)
On my opinion it is impossible to use GRT to Universe as
a whole. The Newton/ Einstein's gravitation laws are correct
only in the local parts of Vacuum. The Universe / Vacuum
as a whole is endless.
e)
So, how does GRT explain time?
According to GRT the time depends on the mass
and speed it means, of moving matter.
It means that different masses and speeds can create
different time. For example, our planet Earth has its
own time but for us it is absolute.
The other planets have another mass and speed and
therefore they have their own time. This time according
to GRT is relative. But their habitants will think their
time is absolute. But if they know GRT they will
not make this mistake.
=============
According to SRT and GRT time is relative.
SRT says about proper/ individual time of an
electron/ light quanta.
GRT says about planetary time of a Planet..
The time cannot exist without matter and speed,
in another words, without moving matter. But
different reasons and different moving of a matter
create the proper and planetary time.
=================..
Is it possible to see the different manifestation of
time in a human being?
Here is an article “ Even the time is pressed from fear”
by Dr. Vadim Chernobrov (collaborator of MAI -
- Moscow Aviation Institute).
He wrote, that we usually think time is a constant quality.
But Einstein’s relative theory says time is relative.
Question. Is it possible to check it in our life?
Answer. Russian and foreign researches say it is
possible. The documents (secret in the past) testify
that “cataclysm of time”, “ phenomenon of time’s
perversion “,” the changes (its deceleration) of time”
often is observed by people whose profession connected
with risk: astronauts, pilots, drivers, soldiers.
1.
The test pilot Mark Gallay wrote in his book
“The test in the sky” when his airplane was caught
with fire “ the time began to go in another scale. The time
almost stopped. Every second took ability of expansion,
and in this situation it was possible to do many things.”
He confirms that tested such feeling many times.
2.
The test pilot Marina L. Popovich said the same,
in the dangerous, catastrophic situations “ the time
is stretches”.
3.
In June 1989 the soviet airplane MIG-29 crashed near
Paris, in Le Bourget airport , in the time of its air show.
The notes of “the black box” showed that during the
four (4)seconds the test pilot Anatoly Kvochur made as
many operations as in normal situation it would take some
minutes. The test pilot later said: ” the time was stretched”.
4.
The captain N.Z.(fought in Afghanistan) remembers:
“the fly of the bullet was so beautiful that I didn’t guess
to evade from it, although I have enough time to do it”.
5.
The sergeant V. Ch (fought in Afghanistan) told:
“ The black barrel of gun seems very big, even enormous.
Time is stopped and full silence came. And I moved slowly
a step a side and the bullet passed close to me.”
6.
Etc…
His conclusions.
The people in a critical situation, on the border of death,
suddenly for themselves begin to see everything as in the
slow down film and in this time their speed reaction and
power increase in tens and hundreds times. And this explains:
a) why a man who escaped from wolves, can quickly reach
up the top of the naked tree,
b) an old woman took out a big trunk from her burned house,
which later two strong firemen couldn’t rise.
c) etc…
=============..
My experience.
The speed on the curve was so fast that to keep the balance of
the car I went on other road line and flew straight at the
“forehead’ of a green mercedes. The driver of the mercedes
was in panic, in horror. He threw the wheel and closed his face
with his hands. Suddenly the time stopped and the sound disappeared
for me and I made many actions before my car kicked only the side
back door of the mercedes. It was long time ago, but writing this article
I understood better what happened.
Our computer-brain works on a dualistic basis.
Brain of a man approximately consists of sixteen milliards neutrons.
All of them form the system that manages human body.
That is why that with the work of all the sixteen milliards neutrons
of brain, a man cannot catch a single impulse of his Electron, of his
Quantum of light, of his God:
(mass of electron is equal 10^-31 kg., charge of electron is equal 10^-19 k.)
But in that time ( critical time ) most neurons of my brain stopped
their electric pulse (time almost stopped) and my Light Quanta/Electron
in this new condition (superconductivity) had possibility to increase
my speed reaction and power on a short period of time and maybe
saved my life. I must to thank Him.
===================..
Best wishes.
Israel Sadovnik. / Socratus.
http://www.socratus.com
http://www.wbabin.net
http://www.wbabin.net/comments/sadovnik.htm
http://www.wbabin.net/physics/sadovnik.pdf
"To them, time would flow in a completely conventional fashion. It is only when comparing their universe to ours that anything seems out of the ordinaryour past is their future, and vice versa"
Reply | Report Abuse | Link to thisDoes this mean that people who remember our past, their future, are able to remember the end of their universe... knew what the end of their universe and the beginning of our universe would be?
Were they able to forsee the big bang?
Before the blogs were canceled here on Sci Am I had a blog under the username "PHAYEZ" which dealt with, among other things, time and measurement. I put forward that time only exists as a feature of three dimensional existence. Time is the "velocity/distance of 3D matter relative to the velocity/distance of other 3D matter". Outside of three dimensions "TIME" as such does not exist and infinity is equal to zero "time". Also outside of three dimensions measurements cannot be made of anything which makes mathematics, with all due respect, irrelevant since the language of mathematics has, as a syntax, products of measurement. The existence and non-existence of time is a spatial relationship oxymoron which is difficult to grasp when you are an entity who is wholly dependent on being made up of atoms which are moving through space.
Reply | Report Abuse | Link to thisOne final comment, if I may, on the speed limit of light and the fact that even information cannot exceed the speed of light. At the speed of light time is zero, in other words for the light there is no time that passes so that regardless of where it arrives, it arrives instantaneously. Nothing can move faster than instantaneously, even information...
Pierre
username: PHAYEZ (Edmonton,Alberta,Canada)
Sorry to be so blunt but Scientific American is proving to be nothing but a pseudoscientific rag. The truth is that time does not change by definition. Why? Simply because changing time is self-referential. Movement in time would have to be given as v = t/t which is nonsensical because the units cancel out. In other words, nothing can move in spacetime. Surprise! This is the reason that Sir Karl Popper once called spacetime "Einstein's block universe in which nothing happens." Source: Conjectures and Refutations.
Reply | Report Abuse | Link to thisAnd no, we are not traveling toward the future at 1 second per second. There is only the changing present, the now. There is no time travel in any direction. Wake up.
Nasty Little Truth About Spacetime Physics:
http://www.rebelscience.org/Crackpots/notorious.htm
Time does not "move" in any universe. The spacetime milieu is frozen in all universes. What moves is the point of view of the observer who slides along beholding different slices of the milieu.
Reply | Report Abuse | Link to thisEinstein surely knew this, but he rarely pushed it to its ultimate conclusion, even in his monumental battles with Neils Bohr and the Copenhagen Interpretation.
The fact is that there is no "chance" no "randomness" and all fabled "probability tables" are historical records of the way some physical events appear after the fact. They do NOT mean that two different probable outcomes exist if you flip a coin in the next minute. That outcome already exists, has always existed (if you really do reach in your pocket, pull out a coin, and complete the action) and further that historical record once created will always exist. The concept of chance is an artifact of the consciousness of the observer and that is all that it is.
An astute observer may indeed "predict" the future using models derived from probability tables and this is where the famed accuracy of QM formulae come in. But there are no branching universes at any decision or choice point because there were never any other paths to take. Obviously, there is no free will. What we humans enjoy that give us the illusion of free will is a selective inability to see the future. Sometimes this blinder does not work so well. Sometimes we misremember or totally forget the past until some relic reminds us otherwise.
In an entropy sense, low entropy means low energy but high knowledge, in that the simple milieu very early in the direction of spacetime that we think of as the beginning was very orderly. You could know where everything was and what it was going to do (in total violation of Heisenberg) but for some unknown reason that all blew up. Knowledge was very high, potential energy was very high. A soup can't boil if there are no differences at all between one volume of space and another.
Even today we can very accurate predict the position and momentum in spacetime of a macro-item, but not at all of a quantum particle. We have to revert to the probability tables.
We can talk about "cause and effect" and find some pretty good correlations, but really both cause and effect are artifacts of the way our minds work as we view a changing slice of frozen and fixed spacetime every instant, always moving in one direction as far as we can tell.
look up Nassim Haramein ...on google...u might be awakened..ridgeman
Reply | Report Abuse | Link to thisTime does run backwards in the only other universe that exists, namely the antimatter universe, created at the same time as our universe at Big Bang. The Multiverse concept, string theory and many worlds hypotheses are all theoretical errors due to Big Bang not being properly understood. Let us call this other time mode "Anti-time". Time and it's partner anti-time were both created at Big Bang, and neither existed as a dimension prior to the Singularity of Big Bang. Antimatter arising at creation was not destroyed, but rather preserved in a partition process, and possibly held in an alternate quantum phase. Dark Matter is antimatter. We can't see it, but can only sense it's Gravitational presence. The shock of Big Bang was so great, that not only was this process responsible for Inflation, but it caused time at the Quantum level to exchange, as between our universe and the antimatter one. Hence the Quantum world behaves in a bizarre manner, when compared to the classical/relativistic world. That is why we can only describe Quantum events in uncertain probablistic terms, and Cause and Effect does not operate as it should. Anti-time also explains the phenomena of Gravity and Entanglement. If Gravity propagates in Anti-time, that explains why it has never been detected. Also explains why it is weaker, due to signal transversing both universes. Also explains concept of Mass, as it is closely related to Gravity. There is no such particle as the Higgs Boson. Forces such as Gravity that propagate in anti-time, actually travel at velocity C, but give the appearance of being instantaneous. Hence Relativity is not violated. Finally, the reason that Relativity breaks down at a Singularity is because time breaks down. Similarly Quantum Mechanics breaks down because there is no Anti-time. Neither theory can describe a state where time is not present, but both theories are valid when it is. Hence the idea of Quantum Gravity is also a conceptial error. The status quo of this Universe/Anti-Universe may be expressed as S + ~S =K, where S is entropy, ~S is antentropy and k is constant.
Reply | Report Abuse | Link to thisbut isn't time and space an "invention" to make sense of "life" on a 3-dimensional level?
Reply | Report Abuse | Link to thisTime can be see to run backwards in the universe of film and imagination it can be seen by running a movie film in reverse
Reply | Report Abuse | Link to thisand the picture thar the "cosmologists have put together an incredibly successful picture"
Time can be seen to run backwards in the universe of film and the universe of imagination. Iit can be seen by running a movie film in reverse and in the imagination of what the "cosmologists have put together an incredibly successful picture" are we in Kanas anymore Dorthy
Reply | Report Abuse | Link to thissory but i writhe portuguese:
Reply | Report Abuse | Link to thisa realidade espaco-tempo tetra dimensional:haltura ,largura, comprimento e tempo est� mal equacionada. Na verdade a realidade cosmica tetra dimencional �:haltura ,largura, comprimento(muldimensionais)e enegia. O tempo � apenas um ideal fantastico-nao existe. O que interessa � o comportamento da fisica quantica/energia- e sua compreencao. O meu mail:isabelcinesio@gmail.com
Time is entropical dynamic in momentary snap of movie camera of our organic brain. Time is taking birth and dying in a moment and an illusion. So time forward or backward is meaningless. Time is not dimension. Universe does not know time or past except our brain memory cell snaps. Time we have not understood so we say forward or backward and arrow etc.
Reply | Report Abuse | Link to thisFor a useful discussion of this topic please see http://sites.google.com/site/smithjcn/time
Reply | Report Abuse | Link to this"Some 14 billion years ago the cosmos was hotter and denser than the interior of a star, and since then it has been cooling off and thinning out as the fabric of space expands."
Reply | Report Abuse | Link to thisSorry, but this is only a theory. It is not a good theory either because it doesn't hold up to scrutiny. The theory is the result of a misconception concerning the nature of the expansion of the Universe. It's too bad it gets accepted mainstream without much debate anymore. Anymore, it's about coming up with theories to explain why the big bang theory doesn't work, or more accurately I mean the movement is to come up with ways to make the big bang work, since it doesn't on its own. It's too frightening to think about how the universe could be expanding without having come from a big bang. By inventing things though, we can continue our ignorant understanding. Well, once upon a time, long, long ago, but not too long ago, things were 'special'... B.S.
In dense aether theory the Universe is composed of nested density fluctuations and we are one of this fluctuations. So it runs backward in time from perspective of every observer above the observer scale, which correspond the wavelength of cosmic microwave radiation.
Reply | Report Abuse | Link to thishttp://aetherwavetheory.blogspot.com/2009/08/awt-and-cosmological-time-arrow.html