PANGON

Do We Live in a Giant Cosmic Bubble?

By Clara Moskowitz, Staff Writer

posted: 30 September 2008 06:48 am ET
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This Chandra X-ray photograph shows Cassiopeia A (Cas A, for short), the youngest supernova remnant in the Milky Way. Credit: NASA/CXC/MIT/UMass Amherst/M.D.Stage et al.
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This Chandra X-ray photograph shows Cassiopeia A (Cas A, for short), the youngest supernova remnant in the Milky Way. Credit: NASA/CXC/MIT/UMass Amherst/M.D.Stage et al.
Mugshots of some of the two dozen supernova explosions captured by NASA's Swift satellite. Credit: NASA

If the notion of dark energy sounds improbable, get ready for an even more outlandish suggestion.

Earth may be trapped in an abnormal bubble of space-time that is particularly void of matter. Scientists say this condition could account for the apparent acceleration of the universe's expansion, for which dark energy currently is the leading explanation.

Dark energy is the name given to the hypothetical force that could be drawing all the stuff in the universe outward at an ever-increasing rate. Current thinking is that 74 percent of the universe could be made up of this exotic dark energy, with another 21 percent being dark matter, and normal matter comprising the remaining 5 percent.

Until now, there has been no good way to choose between dark energy or the void explanation, but a new study outlines a potential test of the bubble scenario.

If we were in an unusually sparse area of the universe, then things could look farther away than they really are and there would be no need to rely on dark energy as an explanation for certain astronomical observations.

"If we lived in a very large under-density, then the space-time itself wouldn't be accelerating," said researcher Timothy Clifton of Oxford University in England. "It would just be that the observations, if interpreted in the usual way, would look like they were."

Scientists first detected the acceleration by noting that distant supernovae seemed to be moving away from us faster than they should be. One type of supernova (called Type Ia) is a useful distance indicator, because the explosions always have the same intrinsic brightness. Since light gets dimmer the farther it travels, that means that when the supernovae appear faint to us, they are far away, and when they appear bright, they are closer in.

But if we happened to be in a portion of the universe with less matter in it than normal, then the space-time around us would be different than it is outside, because matter warps space-time. Light travelling from supernovae outside our bubble would appear dimmer, because the light would diverge more than we would expect once it got inside our void.

One problem with the void idea, though, is that it negates a principle that has reined in astronomy for more than 450 years: namely, that our place in the universe isn't special. When Nicholas Copernicus argued that it made much more sense for the Earth to be revolving around the sun than vice versa, it revolutionized science. Since then, most theories have to pass the Copernican test. If they require our planet to be unique, or our position to be exalted, the ideas often seem unlikely.

"This idea that we live in a void would really be a statement that we live in a special place," Clifton told SPACE.com. "The regular cosmological model is based on the idea that where we live is a typical place in the universe. This would be a contradiction to the Copernican principle."

Clifton, along with Oxford researchers Pedro G. Ferreira and Kate Land, say that in coming years we may be able to distinguish between dark energy and the void. They point to the upcoming Joint Dark Energy Mission, planned by NASA and the U.S. Department of Energy to launch in 2014 or 2015. The satellite aims to measure the expansion of the universe precisely by observing about 2,300 supernovae.

The scientists suggest that by looking at a large number of supernovae in a certain region of the universe, they should be able to tell whether the objects are really accelerating away, or if their light is merely being distorted in a void.

The new study will be detailed in an upcoming issue of the journal Physical Review Letters.

* Top 10 Strangest Things in Space


////////////////////////The immortal Game was a chess game played on 21 June 1851 by Adolf Anderssen and Lionel Kieseritzky. The very bold sacrifices made by Anderssen to finally secure victory have made it one of the most famous chess games of all time. Anderssen gave up both rooks and then his queen, checkmating his opponent with his three remaining minor pieces. It has been called an achievement "perhaps unparalleled in chess literature."[1]



//////////////////////CLOSURE


///////////////////////SHIREY SANKRANTI-JLR CRSS




////////////////////////AARA LAW PRACTICE,BRNISON AVE BPPEAL



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Quantum Introduction The Quantum Casino Quantum Entanglement Quantum Decoherence Quantum Reality It's A Small World
The Cosmic Universe The Anthropic Principle The Arrow of Time The Mathematical Universe Is the Universe a Computer? The Big Brother Universe
- Return to Home -
The Arrow of Time

We are all aware of an intuitive "flow" of time from past to future. Not only do we feel this flow of time, but we also see it manifested in the behaviour of objects which change over time. Many objects seem to behave differently in the forward time direction when compared to the backward time direction. For example, we don't see a spilt glass of water jumping up and going back into the glass, we don't see a broken egg reforming itself. These effects all add to the impression that there is some sort of "forward direction" in the time dimension. This directionality is called the Arrow of Time.

However, this "arrow of time" is something of a mystery to physicists because, at the microscopic level, all fundamental physical processes appear to be time-reversible (we'll consider this later). Also, as shown on the Cosmic Universe page, results such as the Wheeler-DeWitt equation suggest a spacetime structure in which all of time is laid-out in a "block universe", i.e., there is no actual "flow" of time, no movement of a "now" point.

So on this page we will investigate the cause of this mysterious "Arrow of Time".
Entropy

Entropy can be considered the amount of disorder in a system. For example, a car that has rusted could be said to have a greater entropy value than a new car: bits of the car may have fallen off, the paint may be flaking. Basically, the molecules of the car have become more disordered over time: entropy has increased.

As has just been just discussed, all microscopic processes appear to be time-reversible. The question of why we see an "arrow of time" in macroscopic processes has therefore presented physics with a long-standing conundrum. For this reason, much attention has focussed on the fact that the entropy of a closed system increases with time, i.e., a system will gradually become more disordered with time. Eventually the system (gas in a closed container, for example) will reach a state when all its molecules are completely randomly orientated. This state is called thermal equilibrium. The rule that entropy increases with time is called the second law of thermodynamics.

The reason for this increase in entropy can be seen from a purely probabilistic argument: a system will have many more possible disordered states than ordered states, so a system which changes state randomly will most likely move to a more disordered state. It's really just a matter of likelihood. For this reason, the second "law" of thermodynamics is not really a "law" at all, certainly not an unbreakable law on the same basis as other physical laws - it is a statistical principle. In fact, it might be possible for a room full of randomly-distributed particles to re-order itself quite by chance so that all the particles end up in one corner of the room - it would just be incredibly unlikely!

While the second "law" of thermodynamics is "just" a statistical principle, it is a mightily powerful statistical principle! This is because the basis of the second law - that "disorder will increase" - seems so obvious, and seems to appeal to a fundamental, platonic principle of mathematics. For this reason, the second law manages to appear even more fundamental and unbreakable than the other physical laws, some of which (for example, the amount of electric charge on an electron) seem rather arbitrary in comparison. This fundamental strength of the second law is described well by the astrophysicist Sir Arthur Eddington:

"If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations - then so much the worse for Maxwell's equations. If it is found to be contradicted by observation - well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can offer you no hope; there is nothing for it but to collapse in deepest humiliation."
- Sir Arthur Eddington

One of the most inexplicable features of the early universe is that it had an incredibly low value of entropy. This value of entropy was so low that even now - 13 billion years later - we still find ourselves living in a world of relatively low entropy. As a result, many of the objects we surround ourselves with have low entropy: new cars, and perfect unbroken eggs in egg cups. And these objects are basically falling apart around us as they inevitably move to higher entropy states: cars rust, eggs fall on the floor and break. Hence, the increase in entropy in our ordered world is one reason why we detect an apparent "arrow of time".
But change of entropy is fundamentally time-symmetrical!!

However, this is a good time to clear-up a very widely-held misconception about the change of entropy: that change of entropy is in some way fundamentally time-asymmetric, that entropy change behaves fundamentally differently in the forward time direction to the backward time direction. This is absolutely not the case. In the general case, entropy increases in the backward time direction in just the same way as it increases in the forward time direction: change of entropy is symmetrical with time. (However, a very small minority of physicists might still believe change of entropy is time-asymmetric - see my comments at the bottom of this discussion with the notoriously tetchy physicist Luboš Motl here).

The probabilistic basis of the second law of thermodynamics simply says that a system will have many more possible disordered states than ordered states, so a system which changes state randomly will most likely move to a more disordered state. This seems very clear and obvious - such a simple statement is never going to be the cause of something so mysterious as fundamental time-asymmetry. Indeed, this change to a more disordered state is just as applicable in the reverse time direction as in the forward time direction: it's just a change of state, independent of time.

But what about the second law of thermodynamics which states that "entropy increases with time"? This seems to imply a fundamental time-asymmetry to entropy. But we have to realise that the second law only applies to special-case systems: objects with low entropy, the sort of objects we generally encounter in everyday life (rusting cars, etc.). In fact, if we consider general-case objects (i.e., objects in thermal equilibrium), objects which have never been arranged into any sort of order, then their entropy is at a maximum already so their entropy can only decrease with time - completely at odds with the second law!

This generally-held misconception that change of entropy is fundamentally time-asymmetrical is revealed by the Loschmidt paradox. The Loschmidt paradox considers the apparently fundamental time-asymmetry of entropy implied by the second law and states that this is at odds with the known time symmetry of fundamental processes. It is only when we realise that the second law is frequently badly stated and hence contains unstated assumptions (which have been just considered) that the Loschmidt paradox is resolved. (Wikipedia describes this resolution of the paradox, showing how one of the key assumptions of Boltzmann's version of the second law of thermodynamics was flawed - see here).

But if change of entropy is time-symmetric, why do we see the entropy of the universe as only increasing? Roger Penrose considers this question in his book The Road to Reality. Penrose considers what we might expect to happen if we trace the entropy of the universe back in time from the state it is in now. If change of entropy is really time-symmetrical, then we should expect to see entropy increasing as we trace the universe into the past, just as we will see entropy increasing into the future. But we know, in fact, that the universe had a lower entropy in the past: i.e., the entropy of the universe actually reduces in the past. So where does this asymmetry come from?

As Roger Penrose goes on to reveal, the time-asymmetry of change of entropy within the universe is explained by the extraordinarily low entropy of the universe at its origin:

Basically, the low-entropy past of the universe "fixes" the experiment. If we want to get a symmetrical answer then we have to be careful to conduct a symmetrical experiment. Rather than starting with a special-case low entropy universe, we have to imagine a universe which started in thermal equilibrium and has reached its current state unaided, purely by chance:

After that low-entropy point is reached, we then see entropy starting to increase according to the second law. But the key thing is that if we trace the entropy of the universe back in time past the low-entropy point we now see that symmetry that Roger Penrose sought. Hence, change of entropy is fundamentally symmetrical.

In fact, throughout this discussion on the arrow of time we will find that the arrow of time is caused by the time-symmetric second law of thermodynamics, together with the very special, low-entropy initial conditions of the universe.

(This discussion on time-symmetric entropy change is based on an example by J. Richard Gott in his book Time Travel in Einstein's Universe in which the role of the universe is played by an ice cube - see here. The ice cube example is considered in detail in Chapter 6 of Brian Greene's book The Fabric of the Cosmos.)
Causality

We all have a very strong feeling of a directionality of time, which has a flow in a forwards direction. As Michael Lockwood says in his book The Labyrinth of Time: "We regard the forward direction in time, in stark contrast to the backward direction, as the direction in which causality is permitted to operate. Causes, we assume, can precede their effects, but cannot follow them."

But we have just seen how physical processes appear to be time-symmetrical, with no distinction between the forward and backward directions. So where does that leave causality? As Michael Lockwood again says about the passage of time: "We find no hint of this in the formalism of Newtonian physics. Not only is there no explicit reference to a passage or flow of time; there is not even any reference to cause and effect. Indeed, there is not even any directionality".

"But", you might protest, "surely causality works in only one direction: forwards in time? I kick a football - the football doesn't kick me." Well, let's consider the example immediately below of forward causality. We see a snooker cue coming in from the left, hitting the white ball, which then causes the white ball to hit the red ball:

However, if you shoot a movie of that sequence, and then play it backwards, it still makes perfect physical sense. As you can see below, we then have the red ball coming in from the right, hitting the white ball, which then causes the white ball to hit the cue backwards. So, because of the symmetry of the laws of physics, this process of causality - which we thought only applied to the forward direction of time - in fact applies equally to the backward direction of time as well:

The reason why we don't see causality happening in the backward direction is purely because of a bias in our psychological systems: something about the complexity of our psychological system (our brains!) causes our thought processes to work only in the forward direction of time (this will be considered below). The great advantage of recording the sequence on a movie and then playing the movie backwards (to reveal the time symmetry of causality) is that a movie camera works in a much more simple fashion than our brains and thus has no such psychological bias in the forward direction: it works in exactly the same way forward as backward.

So if causality is time-symmetrical, we could in fact think of our current situations are being caused by time-reversed future events as much as by past events! For example, as I sit here by my desk in work this morning, I could consider my position as being caused by me being in my apartment this evening, and driving my car from there backward in time, backward down the road the work, to put me in work this morning! It's a bit brain-bending, but it's equally valid as saying "I got up this morning, and drove forwards to work". It seems strange, but that's only because of our psychological bias. The movie of my complete day at work would tell the correct (time-reversible) story.
The Quantum Mechanical Arrow of Time

As has just been explained, almost all known physical principles (from Newtonian mechanics through to Einstein's relativity) have a completely symmetric treatment of past and future. Nowhere in any of these equations is there anything which distinguishes a forward direction of time from a backward direction of time. The exception to this rule appears to be quantum mechanics. On the page on The Quantum Casino it was explained how, when we make a measurement of a quantum observable, there is a "collapse of the wavefunction" in which a probability wave collapses to generate a single observed value from a range of possible values. This process appears to work in the forward time direction only, i.e., it is irreversible.

An explanation for this apparent "collapse of the wavefunction" is presented in detail on the page on Quantum Decoherence, so I don't want to repeat it here. Suffice to say that the coherent phase relationships of the interference terms are destroyed when a particle interacts with the environment. The dissipation of these terms into the wider environment can be interpreted in terms of increasing entropy (again, see the section on "Decoherence and Entropy" on the Quantum Decoherence page for full details). Quantum decoherence can then be understood as a thermodynamic process: after decoherence, the process is said to be thermodynamically irreversible.
Continuing our snooker analogy, the "collapse of the wavefunction" is like a snooker break-off shot. Imagine each ball represents an interference term of the quantum state. Before the shot, (before we make a quantum observation), we see low entropy - everything is nicely ordered. All the interference terms are coherent, and capable of producing interference patterns.
After the shot, the system of balls represents a system with greatly-increased entropy (disorder). This is what happens when we make a quantum observation: interference terms dissipate into the "heat bath" environment, and all coherence is lost in the confused mess. The situation is now one of thermal irreversibility: it is extremely unlikely the original ordered situation could re-form itself. We therefore only see the collapse of the wavefunction operating the forward time direction (for the same reason we don't see broken eggs mending themselves).

So once again the underlying physical principles appear to be time symmetric, with no fundamental preference for either the forward or backward time direction. The apparent arrow of time produced by the "collapse of the wavefunction" is once again shown to be a result of increasing entropy. As Andreas Albrecht explains in his arXiv paper astro-ph/0210527 (when considering decoherence in the double-slit experiment): "A double-slit electron striking a photographic plate is only a good quantum measurement to the extent that the photographic plate is well constructed, and has a very low probability of re-emitting the electron in the coherent 'double slit' state. Good photographic plates are possible because of the thermodynamic arrow of time: the electron striking the plate puts the internal degrees of freedom of the plate into a higher entropy state, which is essentially impossible to reverse. Furthermore, different electron positions on the plate become entangled with different states of the internal degrees of freedom, so there is essentially no interference between positions of the electron. From this point of view, the quantum mechanical arrow of time is none other than the thermodynamic arrow of time."
Why can't we remember the future?

If physical processes all appear to be time-reversible at a fundamental level, we might ask the question "Why can't we remember the future?" After all, we can remember the past, and physics seems to make no distinction between past, present, and future. So why don't we already have prior knowledge of what is going to happen in the future?

In order to answer this question, we shall consider the reasoning of James Hartle which is based around the radiative arrow of time:
The Radiative Arrow of Time

In his arXiv paper "The Physics of Now" (gr-qc/0403001), James Hartle makes the point that the reason we can't remember the future is because we have not yet received any information about future events. This thinking is based on the idea of a "light cone", the shape of which is defined by the speed of light:

At first glance, this might seem a very straightforward explanation of why we are unable to remember the future: it takes time for a light ray (photons) carrying information to reach us from a distant event. Basically, in the future we will have more information about distant events than we have at present. It is hard to imagine a situation in which light behaves differently - it would appear that light will always take time to travel from a point A to a point B:

This principle - that light will always take time, travelling forwards in time between two points - is called the radiative arrow of time (also known as the electromagnetic arrow of time). But this apparently clear-cut principle is not as clear-cut as it first appears. It turns out that the "world line" of the photon is the same for a photon travelling forwards in time from point A to B as it is for a photon travelling backward in time from point B to point A:
The world line of a photon (position of the photon at any given point in time) is the same for a photon going forwards in time from point A to point B as it is for a photon going backward in time from point B to point A.

In fact, if we temporarily forget about the little arrows on the world lines (which indicate "cause" and "effect") then we see that the world lines of both the forward and backward photons are precisely identical:
With the little arrows removed from the world lines, the paths of the photons going backward and forward in time are shown to be identical.

This principle is clearly illustrated by a Feynman diagram of particle interactions which can be rotated at will, showing particle interactions work exactly the same backward in time as forward in time:

It makes no sense to talk about the entropy of a single photon (entropy is a statistical property of a large group of particles), so a single photon has no arrow of time. However, we do not receive our information about distant events in the form of single photons. Rather, it appears we receive information in the form of light rays which are composed of billions of photons (bosons are quite happy to congregate in the same state, and gather together in a cooperative fashion to create light rays - see the It's a Small World page). For this reason, studies of the radiative arrow of time have concentrated on studying the Maxwell electromagnetic field equations which treats light as a field with a wave nature (rather than considering the path of individual particles).

It is often quoted that Maxwell's electromagnetic field equations are time-reversible and so allow for advanced (backward-in-time) waves as well as retarded (forward-in-time) waves (see here). However, in practice it is much easier to produce a retarded wave than an advanced wave, and this reveals the limitations of Maxwell's equations as a full description of the behaviour of light. We need to combine Maxwell's equations with something else in order to derive a radiative arrow of time.

James Hartle attempts to use Maxwell's equations to deduce the radiative arrow of time in Appendix A of his aforementioned arXiv paper gr-qc/0403001, "The Cosmological Origin of Time's Arrow". His approach (based on principles described in H. Dieter Zeh's book The Physical Basis for the Direction of Time) combines the time-symmetric Maxwell's equations with the time-asymmetric boundary conditions of the universe as a whole (he considers the asymmetrical total amount of electromagnetic radiation). The approach suggests that because there were no free electromagnetic fields at the start of the universe, but there are fields in the future, those fields must all be caused by retarded waves that have their sources in the past. However, I don't see how the radiative arrow of time can depend on the total of electromagnetic fields in the universe in this way. There's no equivalent of the second law of thermodynamics (increasing entropy) for electromagnetic fields. The total of electromagnetic field in an isolated system does not tend to increase (as is the case with entropy). The radiative arrow of time must surely depend on the increasing sum total of entropy in the universe, not the total of electromagnetic field. Surely the radiative arrow of time must have the same cause as the thermodynamic arrow of time.

At the beginning of the last century, Walter Ritz proposed that only retarded (forward-in-time) waves were physically possible (i.e., the process was fundamentally time-asymmetric). In 1908 and 1909 he had a famous argument with Einstein over this matter, as Einstein believed the process was fundamentally symmetric and could be explained by thermodynamic arguments (see here). It turns out that it is easier to create a light ray in the forward time direction as the behaviour of the billions of photons as they are produced (by an ordered source such as a light bulb) and scattered (when they reach a target) can be understood in turns of increasing entropy: "This arrow has been reversed in carefully-worked experiments which have created convergent waves, so this arrow probably follows from the thermodynamic arrow in that meeting the conditions to produce a convergent wave requires more order than the conditions for a radiative wave. Put differently, the probability for initial conditions that produce a convergent wave is much lower than the probability for initial conditions that produce a radiative wave. In fact, normally a radiative wave increases entropy, while a convergent wave decreases it." (see the Wikipedia article on the Arrow of Time). Hence, the reason we do not see convergent, advanced waves can be explained in terms of entropy.

When I turn on an electric light, for example, the photons leave the bulb in a relatively ordered form. The photons then radiate away from the bulb, redistributing themselves around the room (i.e., a radiative wave), creating a state of greater disorder - increased entropy. As Andreas Albrecht explains in his arXiv paper astro-ph/0210527: "The complete absence of the time-reverse of radiation absorption is understood to be one feature of the thermodynamic arrow of time in our world. A hillside absorbing an evening news broadcast is entering a higher entropy state, and the entropy would have to decrease for any of the troublesome time-reversed cases to take place. So in the end, the radiation arrow of time is none other than the thermodynamic arrow of time."
Could it be possible to remember the future?

If we consider the hypothetical situation in which we have found a way to circumvent the limitations imposed by the radiative arrow of time, it is interesting to ask if it could ever be possible to remember the future. And, if so, what would our "memories" by like?

In this respect, the Scottish philosopher Donald Mackay suggested an interesting "thought experiment". Mackay wondered if it could ever be possible to predict how someone will behave in the future, and, if so, what would be the consequences for human free will. If we had complete knowledge of the current state of a person's brain, would we be able to accurately predict a person's actions in the short-term future? Basically, if we are able to predict how a person will behave - and the decisions they will make - in the future then human free will is shown to be a fallacy, an illusion.

However, Mackay suggested that it would be impossible to predict a person's future decisions if that predicted future was made known to the person. This is because the person could then choose to act in a different way from how you have told him he will behave. This is described by John D. Barrow in his book Impossibility: "Consider a person who is asked to choose between soup or salad for lunch. If we introduce a brain scientist who not only knows the complete state of this person's brain, but that of the entire universe as well at present, we could ask whether this scientist can infallibly announce what the choice of lunch will be. The answer is 'No'. The subject can always be stubborn, and adopt a strategy that says 'If you say that I will choose soup, then I will choose salad, and vice versa'. Under these conditions it is logically impossible for the scientist to predict infallibly what the person will choose if the scientist makes his prediction known."

So if a person gains access to knowledge about his future behaviour, it would appear that it becomes impossible to predict that future. But this knowledge about future behaviour is precisely what a person will gain if he is able to remember the future. So if a person is able to remember the future, he could then choose to act in a different way to how his memory of the future tells him he will act! There would appear to be a logical inconsistency here: if a person is able to remember the future, then those memories of the future instantly become unreliable. Therefore, it would appear to be impossible to "remember the future".

As an example, here's how Dilbert might behave if he could remember the future:

This logical inconsistency prohibiting you from remembering the future (based on Mackay's reasoning) arises because the following two statements cannot both be true:

1. You can receive - or "remember" - information about events in the future.
2. You have "free will" in determining your future actions, i.e., you have complete choice in selecting your future actions from a range of possibilities.

However, it might be possible to remember the future (the first of those two statements being true) if the second statement is, in fact, false. Maybe you have no freedom of choice in choosing your future actions - maybe "free will" is just an illusion. Indeed, if all of spacetime is laid-out as an unchanging four-dimensional "block universe" then your future actions are just as determined - just as "set in stone" - as your past actions.
Block Time

For more information about this, see this Scientific American article by Paul Davies.

As Michael Lockwood says in his book The Labyrinth of Time: "To take the spacetime view seriously is indeed to regard everything that ever exists, or ever happens, at any time or place, as being just as real as the contents of the here and now. And this rules out any conception of free will that pictures human agents, through their choices, as selectively conferring actuality on what are initially only potentialities."

So now let's proceed on the basis that our sense of free will is just an illusion, and the future is fixed - a scenario which contains no logical inconsistencies and thus allows us (at least in theory) to "remember the future". We can then ask what form these "memories of the future" might take.

In our everyday experience, our memories of the past seem set in stone, but we have no recollection of the future. It is this distinction, this lack of recollection of the future, that gives us an impression of free will: the past is set in stone, but the future is undecided and we have yet to choose which path it takes. However, in a block universe the future is just as set in stone as the past, and our memories of the future would take exactly the same nature as our memories of the past: an unchanging future, set in stone.
In our everyday experience, we can remember the past (memories which appear fixed - like photos in frames), but not the future. Hence we get the impression of free will: the future is apparently undetermined - we feel free to select our future actions from a range of possibilities.
The fact that we can remember the past - yet have no recollection of the future - is the reason why we feel the "flow" of time: we get a false impression that the "unreal" future has become the "real" past.
If we were able to remember the future, we would find our memories of the future are also unalterable, just like our memories of the past. Our notion of free will would then be revealed as just an illusion.

You might think that would be rather unsettling, knowing that you are constrained to follow only one particular path of action, and have no choice in the matter. You might imagine that you would feel manipulated and controlled in your future actions - a rather scary feeling. However, I would imagine that the fact that you now have memories of both the past and future would mean that you would no longer feel a "flow" of time: we would feel perfectly balanced between "past" and "future", with no "motion" involved. Maybe that would be less scary?

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Somehow it seems that we should be able to "remember the future" as an act of out will, or choice in the present. I see remembering the future as imagining it. The whole "secret" thing or law of attraction. What do I want to "be my life?", experiencing what I want by "remembering" it. Somehow imagination and memory seem intertwined. I just tend to believe that freewill and the future already existing could be compatible. As a Christian, I believe that God already knows the future, therefore knows everything we will do in our lifetimes. For us to visualize a desire as actual, could that be using our memory in reverse? I don't know if you can make any sense of this, but maybe it will stimulate your thinking. I would be curious to hear your response. I guess I'll have to revisit this sight to see if anyone has commented. - Francine, 17th February 2008
Hi Francine, thanks for your comment. Donald Mackay (who I mentioned in the text) was also a Christian and proposed his theory to prove that there was such a thing as free will (see http://www.asa3.org/ASA/topics/Philosophy/PSCF12-99Feucht.html , though my version is perhaps clearer). Basically, as I described above, Mackay suggested that it would be impossible to predict a person's future decisions if that predicted future was made known to the person. However, as I described, I think there's a flaw in Mackay's argument in that he assumes the person would have freedom to take various future paths - something perhaps not possible in a block universe. This is covered very well in John D. Barrow's book "Impossibility" which I can recommend to you.

Here's another extract from "Impossibility" which you might find interesting: "Is it possible to pray for the past to be changed? Few Christian theologians would support this idea if the past was known to the person praying; but what if an event has occured about which the outcome is still unknown to you? Or what about an outcome, like an examination result, that has already been decided, but which has yet to be announced? In his book on miracles, C.S. Lewis, an influential popular writer on theological questions, sided with the idea tha it was rational to pray for events whose outcome had already been decided, because from a God's-eye perspective your future intercession could be an ingredient in the global events which may affect the outcome of the event being prayed for. Lewis was adopting what physicists call the 'block universe' picture of spacetime, in which the entire spacetime alread exists as a complete entity. He conceived of the whole of space and time as viewed externally by God, and so all prayers were known by God before they were made. This would permit free will to be retained together with a doctrine of God's omniscience. God's foreknowledge does not predestine our actions. Rather it is our actions that determine God's foreknowledge. We introduce these interesting theological questions to show that the questions of changing the past and making sense of the resulting coherence of the universe are not questions that lie solely in the realm of physics." - Andrew Thomas, 17th February 2008
This is a brilliant article- mind boggling
I definately believe that by praying we can ask God to change the past if that result is unkown to us. But am confused as to why this would only be possible if we dont know the outcome.
Any thoughts ?

Dr Walia - hardeep walia, 18th February 2008
Hardeep, the question of "why this would only be possible if we dont know the outcome" - I can see a kind of logic behind this conclusion in that if we knew the outcome already, and then that outcome changed, we would have an inconsistency in the system: an event which both occurred and didn't occur. At least if we didn't know the outcome then we wouldn't have that logical inconsistency in our heads. But could it be said that the other outcome happened, even though we were not aware of it? Basically, if we are not aware of the event, does it actually happen, does it have reality? That then introduces ideas of the observer somehow "creating reality" by their observation - ideas from quantum mechanics. Yeah, "mind-boggling", as you say! - Andrew Thomas, 18th February 2008
Hello, I love the way things are explained on this website. I would like to state that I had found a way to disprove time prior to reading any philosophical/theoretical/mathematic findings outside of my own, aside from a small article written by a friend of mine about writings from a philosopher by the name of Plato regarding reality. My goal now is to apply my findings with all applicable findings relating to reality and the function of the universe. This website has giving me so much that I want to thank you for your assistance. THANK YOU! My first mark is, without a doubt, an explanation as to how we are unable to remember what we call the future. - Kevin, 8th April 2008
Thanks, Kevin. Good luck with your theory of time. Be sure to post back here when you finish. - Andrew Thomas, 8th April 2008
Thanks for the great insight and many questions and paradoxes raised here. I am not a very bright fellow, but I have always had the strange sense that all of history which includes my memories are being constantly rewritten so to speak. Our memory of time, space and reality could be changing constantly at the quantum level. What seems like fixed and solid memories may really have changed many times over in the past few seconds. It would explain a lot of things if this is the case. Parallel universes could be constantly forming and collapsing all the time. We may be praying for things that we think are future but are really neither past or future, but from God's perspective there is no "Arrow of Time."---just the eternal now.The cause and effect of all things could be operating completely outside our concept of time moving forward. It would explain Jesus comment,"With God all things are possible!" - Rodney , 29th April 2008
Nice comment Rodney - Michael, 2nd May 2008
I've been listening to CDs of Vishal Mangalwadi's 2007 lectures at the U of Minnessota: "Must The Sun Set On The West". He says that God is outside of the universe he created, so he is not bound by the logic, for instance, or time, space, and energy, as we know it. That's why we need to "see what is there" rather than figuring it out in our minds, and why we cannot "know" the future unless he tells us. - Addamstaft, 9th June 2008
About Temporal Communication. I believe this may be how I have seen the future before.

I know, crazy.. right? Well I have an IQ of 130, have not been abducted by aliens, and am not considered weird by my fellow man..haha

I had a dream that I hit my bosses truck with my car on the driver side back. Then I woke up and in the morning and my bosses son told me he hit my car with my bosses truck in the drivers side back. The damage looked just like the dream. It is statistically impossible that this was a coincidence--especially because I have had this type of thing about 6 times on big stuff and hundreds of times on small stuff. (it was reversed but that happens in dreams). It was so astonishing I didnt even get mad my car was hit.

I theorized that I was actually in touch with the John of my future. Up until now I have ever heard anyone mention that this is how the future is seen by some people in some cases. Its like I pick up stray thoughts from the future me every now and then.

Another time a friend told me someone robbed his house. I went home and I thought real hard for a minute to intentionally "see" who did it. The name I came up with was a person who was never known as a thief and I hadnt seen him in maybe a year. I didnt say anything.

Well, 2 weeks later my friend told me that guy did it. I turned white. I dont think I saw him rob the house--I recalled the future conversation of being told he did it. I dont actually know if he did it... I just know he thinks the guy did it.

The other possibility is God allows us to know things. As a christian I know he can do this--I just dont know if thats the case here.

Either way--it proves the future already exists. There simply is no other explanation. I know its easy for people who havnt had these experiences to say Im misreading this--but I'm perceptive enough to know its real.

The real question you ask is could I have changed the future? Well, the missing component in people's search for the answer is God. If there is someone Outside Time who is in control --all the problems go away. In other word--if we do see the future..we see it for a reason. So whether we see it to confirm there is a God--or to prevent us from flipping out when something bad happens--or to actually prevent something for some unknown purpose...its up to God who knows all possible outcomes.

Anyway..very cool website my friend. - John R, 5th July 2008
That's a coincidence, because I had a dream last week about perfect surfing waves outside my flat (I'm a keen surfer, and we hardly ever get perfect waves here). And the next evening we had perfect waves just like in my dream! It really was a bit weird. I do suspect dreams tap into the enormous potential of the unconscious human mind in a way which we don't yet understand. Your experiences seem to bear that out. - Andrew Thomas, 5th July 2008
"The other possibility is God allows us to know things. As a christian I know he can do this--I just dont know if thats the case here. "
- Andrew, 14th September 2008
Without bringing religion into it, every scientist should know about the very strong evidence that already exists for precognition, in dreams or otherwise, including many carefully controlled experiments. See for example Dean Radin's books "Entangled Minds" and "Conscious Universe" (both with many good references) or any of several peer-reviewed journals such as the Journal of the Parapsychological Assn, and the Journal of the American Society for Psychical Research. We *can* indeed "remember the future", but it is difficult exactly because of the increasing entropy argument given above. - Richard Shoup, 15th September 2008
Thanks very much for those references, Richard. - Andrew Thomas, 15th September 2008
Very interesting page … so we could have the basis to explain “Déjà vu” as well as “Human Intuition” : both phenomena could be interpreted as a malfunctioning (maybe intentionally left) in the process which prevents us to remember the future. - Gabriel, 29th September 2008
That's a good point, Gabriel. Yes, I suppose déjà vu could be thought of as "remembering the future" as you feel that your current situation is already in your memory. This implies that there was a point in the past when you could have "remembered the future". - Andrew Thomas, 29th September 2008



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