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Meredith posted on 1/9/2002

Where does time go? Why does it go? Why does it pass? Why is it so important?
 

Chris Forbes-Ewan responded:
 Need more what ... time? :-)

Don't we all!

Try the latest Scientific American:  www.scientificamerican.com

and click on the articles about time.

Also see the NS article below (but be warned, this is a long article).

Source: New Scientist 16 October 1999

Surely nothing is possible without time? But according to physicist Julian Barbour, it doesn't even exist

Time seems to be the most powerful force, an irresistible river carrying us from birth to death. To most people it is an inescapable part of life, a fundamental element of the Universe.

But I think that time is an illusion. Physicists struggling to unify quantum mechanics and Einstein's general theory of relativity have found hints that the Universe is timeless. I believe that this idea should be taken seriously. Paradoxically, we might be able to explain the mysterious "arrow of time"--the difference between past and future--by abandoning time. But to understand how, we need to change radically our ideas of how the Universe works.

Let's start with Newton's picture of absolute time. He argued that objects exist in an immense immobile space, stretching like a block of glass from infinity to infinity. His time is an invisible river that "flows equably without relation to anything external". Newton's absolute space and time form a framework that exists at a deeper level than the objects in it.

To see how it works, imagine a universe containing only three particles. To describe its history in Newton's terms, you specify a succession of sets of 10 numbers: one for time and three for the spatial coordinates of each of the three particles. But this picture is suspect. As the space-time framework is invisible, how can you determine all the numbers? As far back as 1872, the Austrian physicist Ernst Mach argued that the Universe should be described solely in terms of observable things, the separations between its objects.

With that in mind, we can use a very different framework for the three-particle Universe-a strange, abstract realm called Triangle Land. Think of the three particles as the corners of a triangle. This triangle is completely defined by the lengths of its three sides--just three numbers. You can take these three numbers and use them as coordinates, to mark a point in an abstract "configuration space"

Each possible arrangement of three particles corresponds to a point in this space. There are geometrical restrictions--no triangle has one side longer than the other two put together--so it turns out that all the points lie in or on a pyramid. At the apex of Triangle Land, where all three coordinates are zero, is a point that I call Alpha. It represents the triangle that has sides all of zero length (in other words, all three particles are in the same place).

In the same way, the configurations of a four-particle universe form Tetrahedron Land. It has six dimensions, corresponding to the six separations between pairs of particles--hard to conceive, but it exists as a mathematical entity. And even for the stupendous number of particles that make up our own Universe, we can envisage a vast multidimensional structure representing its configurations. In collaboration with Bruno Bertotti of Pavia University in Italy, I have shown that conventional physics still works in this strange world. As Plato taught that reality exists as perfect forms, I think of the patterns of particles as Platonic forms, and call their totality Platonia.

Platonia is an image of eternity. It is all the arrangements of matter that can be. Looking at it as a whole, there seems to be no more river of time. But could time be hiding? Perhaps there is some sort of local time that makes sense to inhabitants of Platonia.

In classical physics, something like time can indeed creep back in. If you were to lay out all the instants of an evolving Newtonian universe, it would look like a path drawn in Platonia. As a godlike being, outside Platonia, you could run your finger along the path, touching points that correspond to each different arrangement of matter, and see a universe that continuously changes from one state to another. Any point on this path still has something that looks like a definite past and future.

Now's the place

But we know that classical physics is wrong. The world is described by quantum mechanics--and in the arena of Platonia, quantum mechanics kills time.

In the quantum wave theory created by Schrödinger, a particle has no definite position, instead it has a fuzzy probability of being at each possible position. And for three particles, say, there is a certain probability of their forming a triangle in a particular orientation with its centre of mass at some absolute position. The deepest quantum mysteries arise because of holistic statements of this kind. The probabilities are for the whole, not the parts.

What probabilities could quantum mechanics specify for the complete Universe that has Platonia as its arena? There cannot be probabilities at different times because Platonia itself is timeless. There can only be once-and-for-all probabilities for each possible configuration.

In this picture, there are no definite paths. We are not beings progressing from one instant to another. Rather, there are many "Nows" in which a version of us exists--not in any past or future, but scattered in our region of Platonia.

This may sound like the "many worlds" interpretation of quantum mechanics, published in 1957 by Hugh Everett of Princeton University. But in that scheme time still exists: history is a path that branches whenever some quantum decision has to be made. In my picture there are no paths. Each point of Platonia has a probability, and that's the end of the story.

A similar position was reached by much more sophisticated arguments more than 30 years ago. Americans Bryce DeWitt and John Wheeler combined quantum mechanics and Einstein's theory of general relativity to produce an equation that describes the whole Universe. Put into the equation a configuration of the Universe, and out comes a probability for that configuration. There is no mention of time. Admittedly, the Wheeler-DeWitt equation is controversial and fraught with mathematical difficulties, but if quantum cosmology is anything like it--if it is about probabilities-the timeless picture is plausible.

So let's take seriously the idea of a "probability mist" that covers the timeless Platonic landscape. The density of the mist is just the relative probability of the corresponding configuration being realised, or experienced, as an instantaneous state of the Universe--as a Now. If some Nows in Platonia have much higher probabilities than others, they are the ones that are actually experienced. This is like ordinary statistical physics: a glass of water could boil spontaneously, but the probability is so low that we never see it happen.

All this seems a far cry from the reality of our lives. Where is the history we read about? Where are our memories? Where is the bustling, changing world of our experience? Those configurations of the Universe for which the probability mist has a high density, and so are likely to be experienced, must have within them an appearance of history--a set of mutually consistent records that suggests we have a past. I call these configurations "time capsules".

Present past

An arbitrary matter distribution, like dots distributed at random, will not have any meaning. It will not tell story. Almost all imaginable matter distributions are of this kind; only the tiniest fraction seem to carry meaningful information.

One of the most remarkable facts about our Universe is that it does have a meaningful structure. All the matter we can observe in any way is found to contain records of a past.

The first scientists to realise this were geologists. Examining the structure of rocks and fossils, they constructed a long history of the Earth. Modern cosmology has extended this to a history of the Universe right back to the big bang.

What is more, we are somehow directly aware of the passing of time, and we see motion--a change of position over time. You may feel these are such powerful sensations that any attempt to deny them is ridiculous. But imagine yourself frozen in time. You are simply a static arrangement of matter, yet all your memories and experience are still there, represented by physical patterns within your brain--probably as the strengths of the synapse connections between neurons. Just as the structure of geological strata and fossils seem to be evidence of a past, our brains contain physical structures consistent with the appearance of recent and distant events. These structures could surely lead to the impression of time passing. Even the direct perception of motion could arise through the presence in the brain of information about several different positions of the objects we see in motion.

And that is the essence of my proposal. There is no history laid out along a path, there are only records contained within Nows. This timeless vision may seem perverse. But it turns out to have one great potential strength: it could explain the arrow of time.

We are so accustomed to history that we forget how peculiar it is. According to conventional cosmology, our Universe must have started out in an extraordinarily special state to give rise to the highly ordered Universe we find around us, with its arrow of time and records of a past. All matter and energy must have originated at a single point, and had an almost perfectly uniform distribution immediately after the big bang.

Hitherto, the only explanation that science has provided is the anthropic argument: we experience configurations of the Universe that seem to have a history because only these configurations have the characteristics to produce beings who can experience anything. I believe that timeless quantum cosmology provides a far more satisfying explanation.

In Platonia, there are no initial conditions. Only two factors determine where the probability mist is dense: the form of some equation (like the Wheeler-DeWitt equation) and the shape of Platonia. And by sheer logical necessity, Platonia is profoundly asymmetric. Like Triangle Land, it is a lopsided continent with a special point Alpha corresponding to the configuration in which every particle is at the same place.

>From this singular point, the timeless landscape opens out, flower-like, to points that represent configurations of the Universe of arbitrary size and complexity. My conjecture is that the shape of Platonia cannot fail to influence the distribution of the quantum probability mist. It could funnel the mist onto time capsules, those meaningful arrangements that seem to contain records of a past that began at Alpha.

This is, of course, only speculation, but quantum mechanics supports it. In 1929, the British physicist Nevill Mott and Werner Heisenberg from Germany explained how alpha particles, emitted by radioactive nuclei, form straight tracks in cloud chambers. Mott pointed out that, quantum mechanically, the emitted alpha particle is a spherical wave which slowly leaks out of the nucleus. It is difficult to picture how it is that an outgoing spherical wave can produce a straight line," he argued. We think intuitively that it should ionise atoms at random throughout space.

Mott noted that we think this way because we imagine that quantum processes take place in ordinary three-dimensional space. In fact, the possible configurations of the alpha particle and the particles in the detecting chamber must be regarded as the points of a hugely multidimensional configuration space, a miniature Platonia, with the position of the radioactive nucleus playing the role of Alpha.

Ageless creation

When Mott viewed the chamber from this perspective, his equations predicted the existence of the tracks. The basic fact that quantum mechanics treats configurations as whole entities leads to track formation. And a track is just a point in configuration space--but one that creates the appearance of a past, just like our own memories.

There is one more reason to embrace the timeless view. Many theoretical physicists now recognise that the usual notions of time and space must break down near the big bang. They find themselves forced to seek a timeless description of the "beginning" of the Universe, even though they use time elsewhere. It seems more consistent and economical to use an entirely timeless description.

But for these ideas to be more than speculation, they should have concrete, measurable results. Fortunately, Stephen Hawking and other theorists have shown that the Wheeler-DeWitt equation can lead to verifiable predictions. For example, established physical theories cannot predict a value for the cosmological constant, which measures the gravitational repulsion of empty space. But calculations based on the Wheeler- DeWitt equation suggest that it should have a very small value. It should soon be possible to measure the cosmological constant, either by taking the brightness of far-off supernovae and using that to track the expansion of the Universe, or by analysing the shape of humps and bumps in the cosmic microwave background. And a definitive equation of quantum cosmology should give us a precise prediction for the value of the constant. It is a distant prospect, but the nonexistence of time could be confirmed by experiment.

The notion of time as an invisible framework that contains and constrains the Universe is not unlike the crystal spheres invented centuries ago to carry the planets. After the spheres had been shattered by Tycho Brahe's observations, Kepler said: "We must philosophise about these things differently." Much of modern physics stems from this insight. We need a new notion of time.

Julian Barbour is an independent theoretical physicist who lives near Oxford

Further reading:

Time  Our minisite produced in collaboration with the National Physical Laboratory, the UK's National Standards Laboratory.
Julian Barbour's The End of Time is published by Weidenfeld & Nicolson.

Ben Morphett added:

Time is Nature's way of making sure that everything doesn't happen at once.

For more detail, see this month's Scientific American, which is devoted to
the subject of time.
 

Jim Edwards replied

I can recommend three books on time:
   "A Brief History of Time"  by Stephen Hawking
   "The Birth of Time"  by John Gribbin
   "The End of Time"  by Julian Barbour

Gribbin's book is the most accessible.  It is actually the story of how astronomers learnt to calculate the age of the universe, a story in which Gribbin himself had a part.  It is written in his usual easy to read style.

Hawking's book is famous for being the book that everyone has but no-one has finished.  I found it difficult, but not impossible.  I am now re-reading it in the illustrated edition.  It is more a history of the universe and how our understanding of it has changed.

Compared to Barbour's book, Hawking's is a piece of cake.  I am still wading through "The End of Time" of which the NS article is but a taste.  It is a real desert island book, needing lots of (yes) time and no distractions to get your head around some pretty mind-boggling concepts.

I once read a book called "Flatland" by I've forgotten whom, which describes a 2 dimensional world whose characters try to imagine a 3D world.  It helped to put time into perspective.

In M Theory, as I understood it from the Compass programme, there are 10 spacial dimensions and one of time.  Why only one?

I haven't read the others, but I enjoyed Hawking's book (although it seemed to become more complex as 'time' went on and I got further into it).

One you haven't mentioned, which is also not for faint hearts (or intellects) is Paul Davies' book "About Time". I found it to be infuriating (because there were parts I had no hope of understanding), yet as addictive as chocolate or red wine (and perhaps even more fascinating!)

Paul Williams responded:

Just some metaphysics:

Time is arguably an human concept.
It appears that for macroscopic objects (like humans) there is an arrow of time.
This reality (for reality it is for us) comes from the 2nd law of thermodynamics.
Basically, the total entropy of the universe always increases.
The thermodynamic arrow of time moves onwards into the future and backwards, it seems, to a time which equals zero.

Einstein showed that our understanding of the 'present time' has no universal meaning.
From our situation (in space-time) it does - locally - to us.
Our point of view matters very little.
How our understanding of time equates to when the universe began - or will end - may well be a moot point.

Time is how we define it - so it really is all about us.
All our ideas about the *reality* of space-time and the Universe are merely our models.
They are models which appear to work O.K. but models they remain.

One thing seems certain though - we and everything we know will eventually 'wind down' until nothing ever happens again.

Never mind...

Paul Williams replied:

Following on from this thought, (time as a discrete set of
events) we would never know experientially whether the events
are actually sequential! :))

(My brain hurts...)

Peter Macinnis noted:

I thought everybody knew that time was invented by historians to stop everything happening at the same time.

It was a similar motivation that led to geographers inventing space.

David Drury observed:

To Quote "Rosencrantz and Guildenstern Are Dead"...

Rosencrantz: I don't believe in it anyway.
Guildenstern: What
Rosencrantz: England
Guildenstern: Just a conspiracy of cartographers then.

Margaret Ruwoldt commented:

Isn't geography just history enacted very, very slowly?

Peter Macinnis replied:

I realise some may argue that this is degenerating into non-science, but this is not the case.

Tycho Brahe had the endearing quality of having been related to two noble Danish families - called Rosencrantz and Guildenstern.

So there.

and:

Richard Gillespie corrected:

No that's geology, geographers invented place names so the historians had somewhere to talk about.

Margaret Ruwoldt belatedly inserted:

Now hang on a minute, you can't fool me, Richard: geography = slow
history, geology = slow physics.

   ;-)

But I like the place-names idea :-)

At 16:17 31/05/04 +1000, Zero wrote:

It's not our fault -- the coloured pencils made us do it, as they moved in mysterious ways.

What's a Pratchett, anyhow? Sounds like something used to reburnish the knurled knobs on a sneedled flipsock . . . which is mort to the point.

To which Zero Sum replied:

Oh, god! Where did I put my dried frog pills...

Gerald Cairns replied:

If you run out I am sure I will be able to assist but you will need faith cos I am not a registered medic!

On real time, a question without notice, probably to Richard Gillespie.  I have just been at the International Commission on Stratigraphy (ICS) site (http://www.stratigraphy.org/) while digging for stuff on the
Vendian/Ediacaran stoush.

I was wondering: where is the MOST respected liste of end dates for the assorted geological ages and eras?  I seem to be seeing a bit of variety -- just a few million years here and there, but where should I go for the most reliable set of dates?

Tristan wrote:

Using the concept of a Planck length would this imply that in between these incredibly small pulses of time there in fact exists a brief period wherein there is in effect "no time" occurring or alternatively time stops for a brief period until the next Planck length begins?

Zero Sum replied:

I don't think so.  You are still thinking of time as a universal flow.  It isn't.  It is local and represents a (possible) transition from one state to the next.  A photon travels one Planck length in one Planck time.

'Tis why the speed of light en vacuo cannot be exceeded...

No event can take less than the Planck time as there is no 'less'.

There cannot be a period of "no time" because you are using circular semantics.  A 'period' is a measure of time and is therefore of duration one or more Planck times.

The Planck time is to the Universe (or any single locality in it) like the frequency of a computer's clock is to the computer's CPU.  Indivisible at that point.

Chris Forbes-Ewan responded:

It was after the death of an eminent scientist (one so eminent I can't recall his name at the moment). Einstein wrote a letter to the deceased scientist's widow, including the following:

"Now he has departed from this strange world a little ahead of me.

"That means nothing. People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion."

The source of the quote is:

http://www.heartquotes.net/Einstein.html

The circumstances of the quote are from reading done so long ago, I can still remember it.

Ivan Sayer posted:

The reason I wanted chapter and verse was to check by conning the context, whether he was making a slip-up or a po-faced joke.  (No time, no persistence,- no persistence no illusion).  I suspect the latter.  Chris has yet to tell us what he believes about that - or perhaps he did.

I can't dig it up at the moment, but I also seem to remember that he is quoted as saying "When I try to do metaphysics I have the impression of trying to chew something that isn't really in my mouth."

and:

One of these days, when I've nothing better to do, I might give it a try.
I remember his interview with Padams on LNL.  One of the first things he said was that he knew, when the idea first came to him that it was going to take him a long time to get the book written.  At the moment I'm busy - experiencing a belated discovery of Stephen Jay Gould.

Richard Gillespie responded:

Peter Macinnis' question without notice:

I'm regrettably not your most respected source for data not in radiocarbon time, or at best not older than Late Pleistocene.

Chris Forbes-Ewan wrote:

According to Julian Barbour (in New Scientist, 16 October 1999) you may both be correct:

"One of the most remarkable facts about our Universe is that it does have a meaningful structure. All the matter we can observe in any way is found to contain records of a past.

"The first scientists to realise this were geologists. Examining the structure of rocks and fossils, they constructed a long history of the Earth. Modern cosmology has extended this to a history of the Universe right back to the big bang."

In the parallel thread "Time", Zero Sum posted:

Got my doubts...

Supersymmetry suggest to me that it is indeed and illusion, that every possible configuration of matter and energy came into being at the same "time" (because there isn't any) and our "arrow of time" is conciousness
moving from one possibility (universe) to an (note the AN) adjacent one.

Seems the only rational explanation seeing the things that are currently being revealed and resolved.

Since the Copenhagen and Many Worlds have gone "out the window" there doesn't seem much left but the Transactional (shudder) and I have some severe reservations about that.

Douglas Adams I think.

and:

What is important to note I think, is that the 'tick' (the Planck time) occurs for each and every locality (Planck length - distance quanta).

Every possible locality runs its own clock.  They both become distorted in 'stressed' spacetime. Hence the 'speed' of light varies...

Or so I understand it...

More accurate to say that our model contains a continuity that may not exist in the widest reality.

Paul Williams commented:

Zero Sum replied:

Paul, I don't think I was delving into metaphysics.  I drew no conclusions,
merely stated what I belive we purport to understand.

Nolo contendre...  But it is a strawman...

And the point that I was making was that Planck time is just one dimension of the grain, the Planck length is another.  Inseperable.

>
It is quite possible to describe some things with reasonable accuracy in any language provided the terms and operators are defined.  The language we mostly use to describe these things is mathematics, but we only know a subset of all the mathematics there are.  The descriptions can be quite accurate though.  In fact most of those descriptions are in subsets of the sum of the mathematics we understand.

Now, that (above paragraph) is indeed metaphysics but if you want evidence that it is true - In a right angled triangle the square of the hypotenuse equals the sum of the squares of the other two sides.

Not everything in English is metaphysics.  Nor is English useless at being precise (when used in a correct and precise manner).

Angus commented:

If mathematics is discovery (rather than just a model) of how the universe works, then is it not possible that time is continuous but not measureable as such? ie integration of infinitely thin slices is how time 'is' divided. I don't suppose there is a simple method of disproving this or proving otherwise?

Zero Sum responded:

It is precisely because the question cannot be answered that it cannot be so...

The Planck time is the minimum time taken for the least thing to happen (ie. a photon to move one Planck length).  This time is not divisible, it is the "width of the present".

Paul Williams replied:

I've been thinking upon this Zero.
There are certain things, which with great certainty, we can say are true/real - if as you say the terms and operators are (strictly) defined.

This is from a mathematician on another list:

"To give an example.  Suppose I want to prove (in classical synthetic geometry) that any for any rectangle there is a square of the same area."

"Consider rectangle ABCD.  Construct (via compass and straightedge, of course) the straight line A'B'C' where A'B'=AB, B'C'=CB in length. Construct (in the standard way) the midpoint  O  of this line.  Construct the circle centered at  O  with radii  OA'  and OC' (i.e., A'C' is the diameter). Construct the perpendicular to A'C' passing through B'.  Let E be one of the points where this perpendicular intersects the specified circle.
Then A'EC' is a right triangle (standard theorem) and EB' an altitude. Inspecting similar triangles, we see that EB':A'B' = B'C':EB'.  That is, EB' is the mean proportional between A'B' and B'C', which is to say that EB' is the mean proportional between AB and BC.  Thus the square on EB' is equal (in area) to the rectangle ABCD.  QED."

"Now, obviously, I have used archaic language here (and an example that doesn't invoke the machinery of modern mathematics).  But the point is that the "constructed" entities--line a'B'C', point O  , the circle centered at O with radius OA', the perpendicular at B' and so forth, are no less "real" than the original rectangle ABCD.  Of course, I could rephrase everything (a donkey-work exercise) so that all these entities are solidly embedded in the universe of standard axiomatic set theory, but I won't trouble you with that kind of tedium.  But it remains clear that in making the constructions stipulated, I am merely pointing to certain entities (guaranteed by the
axioms) which help to make the existence of the stipulated square sufficiently evident."

Alan Emmerson wrote:

Enlighten me please. Why the elaborate "proof" ?  Is it not sufficient to observe that a square may have any area; and that therefore  some square must have the area of the given rectangle?

Zero Sum replied:

Well, I sort of take the 'informational" approach to the universe. In my terms, velocity isn't bounded by the speed of light but by the speed of information transmission, which of course will be concordant (see other posts upon Planck length/time).

All we can ever see is patterns of information.   That is all we can ever know or describe.  Given that, the term 'real' has rather limited meaning (if any at all).  But really there is no need to assume that anything other than patterns exist.  The media that 'holds the pattern' will always be imperceptible (if indeed it needs to exist at all).

So the difference between physics and metaphysics comes only when you try to speculate on the media.

and:

No, you cannot 'observe' that a square may have any area because you cannot observe all possible squares.

Now if you were to demonstrate a proof that a square could have any  possible area then your proof (above) would logically follow.

The difference between intelligence and reasoning is demonstrated.  That is why it is so difficult (impossible?) to create an AI with conventional programming.

Janet Comyn wrote:

The philosopher Immanuel Kant suggested that time (and space) are forms, rather than objects, of human perception.  We have a sense, proprioception,  which locates our body in space.  Perhaps we have a similar sense, which  locates us in 'time'.  To mis-quote "The truth is not out there".

And getting back to the origins or the theme, surely animals that migrate have a sense of time.

Kevin Phyland posted:

Did I not see something with regard to quantum entanglement that seems to violate, if not causality, at least that the maximum speed of information transmission is c? (a verrry loose definition of information I guess)

Hoping for enlightenment either from within or without

Zero Sum replied:

I think that depends on your interpretation.  However, regardless of interpretation, I have not seen even a theoretical mechanism that suggests a method of passing information faster than the speed of light.

The transactional interpretation requires 'backwards in time handshaking' but even there the information transmitted is 'reserved' information, unmeasurable, unknown and unknowable to us.

Is this because we extrapolate from insufficient information and that insufficient information must (almost) always be the case?

I haven't looked into AI for some time now.
I recall that the IBM 'Deep Blue' chess computer used brute number crunching to gain a victory or two over very good human opponents.

When I was quite young, I played thousands of chess games. At my very best (I believed that) it was possible to visualise all the parameters involved at 3 moves ahead (in a complex middle-game) [Logical opening moves are so standard that it seemed easy to see]

The often quoted '6 moves ahead' is impossible for a human, I believe.
What *seems* to happen when one is *experienced* is that opponent's unlikely (non-advantageous) moves are filtered out. When this happens, 5 - 6 moves ahead is perhaps possible.

I guess what I'm attempting to say is that we actually do not cogitate every possibility at all.
We jump to conclusions based on experience.
Those who we may consider to be clever/intelligent may perhaps be those who's brains have the facility to cut out much of the 'crap'?
'Efficient memory' no doubt comes to the fore here.

I would be interested in feedback on this, as I 'really/truly' do not know...

Cheers
Paul (who hasn't played chess for close to 20 years now)