Defining Time: Our Everyday Mystery

[jeebs]

I'm reading through that paper, and there's a passage I don't understand:

'In particular, nothing in physical equations that deal with time says that the past is more
certain than the future, just like nothing in physical equations that deal with space says
that the left is more certain than the right, or just like that nothing in physical equations
that deal with temperature says that a lower temperature is more certain than a higher
temperature. In other words, nothing in these equations says that time, unlike other
variables, has a property of “lapsing” or “flowing”.'

What is meant by "more certain" in this context? the paper goes on about "time lapsing" all the way through so I'm stuck here.

 

[3nder]

we needed something to measure 'now', 'then' and 'after'. that's all time is, a measurment

 

[MJA]

The only thing more certain than the past or the future is now.

=

 

[Pilot7]

All the confusion about time stems from the existence of two different notions of time, only one of which has to do with physics:
http://www.fqxi.org/data/essay-cont...f?phpMyAdmin=0c371ccdae9b5ff3071bae814fb4f9e9

Yea, I dare say this is definitely the orthodox view. However, this paper is quite weak on several points and arguments, and it fails to reference a number of points even raised in its own bibliography. I will try to offer a critique in more detail when time (!) allows.

In a nut shell though: Yes, there are (at least) two times. And physics clearly concerns itself with one of those. The question of whether it concerns itself with the second is, however, an open question. It certainly is easier to just sweep it under the rug and give it to the "psychologists" to sort out (and I assure everyone that they have produced *nothing* up to around 2001 when I last checked carefully). But there are several problems in physics that may require a better development of our theoretical concept of time, including the so-called "Problem of Time" in quantum gravity and cosmology. But also QT generally (eg quantum zeno effect). Or the relationship between information in quantum systems over time.

I also take quite some issue with the hand waving reduction of all the so called "arrows of time" (most of which we should call "asymmetries in time") to Newton's 2nd Law. That is not so clear, and just because a few cited physicists think it so, don't make it so, and certainly not when it remains an open issue with advocates on both sides. For example the K-Meson I believe is an instance where something quite otherly may be going on. In any case, I will offer a more rigorous critique or cite a paper (mine, now that i think of it) later.

 

[Pilot7]

Fair enough on the Philosopher bit. ...but I am going through an "annoyed by Philosophers" phase - a separate issue and my problem entirely!
...My tie-in with Maths applies here because Maths is a very similar thing which can be thought of as external to the real world but which gives us a way of understanding things.
...
Could it be that the only thing that could make time something more than 'just Maths' could be the fact that we all agree on the direction in which we are using it and that all our experiments seem to indicate a single arrow of direction?

I appreciate your struggle with the definitions at the end of your last post. We are approaching the regions of "what do we mean by mean by mean?" (was it Monty Python?).

With a name like sophiecentaur, how can you be too down on philosophers? ;-) Unless of course you are one, in which case I quite sympathize <grin>. If not, please forgive the slight :-)

The maths analogy is a very interesting one in this context. I have just been over reviewing various blogs on Cohen's axiom of choice work, so I am a bit primed (no pun intended). However, at root of basic mathematics (ie forget all that fancy infinite cardinality stuff--just intuitionist mathematics), most of it does reduce to a complete and consistent first order logic, meaning we don't need to speculate about the Platonic heavens. However, Peano's fifth axiom, corresponding to "mathematical induction" is crucial to get the sort of mathematics we need for basic physics to work (including Hilbert spaces, etc.). This axiom is really an infinite number of first order axioms, and so it is really an article of faith that we accept it is true. A closer look at it, we find that is has an uncanny parallel to something like a Kantian intuition of time... (BTW--this is not my idea, I think it was Poincare who first published something on this). And it is this "axiom" which also makes arithmetic Goedel incomplete... So whether coincidence or serendipity...

Yes, I also came to this kind of conclusion about the direction. I worked this angle in a paper/talk some years ago, arguing that direction should perhaps be adopted as kind of quality in physics (but not this or that direction, just that some set of phenomena have *some* direction). Trying to make "process" sharp without digressing into the meaning of "meaning" and "is" has been very difficult--this is what I was really trying to do in PhD work. Sadly, I was not successful, but I would have to go way out on a rather esoteric limb about why it seems so difficult. And of course I might fall off that limb in the process :-)

 

[MJA]

One Axiom

There is only One mathematical equation
That defines nature truly or absolute
The solution is only =
Or equal
And the lion simply One.
Beyond this simple equation
There is only theoretically division
Complexities faiths and uncertainties
The quantum mechanics of a lost mankind.

=
MJA

 

[sophiecentaur]

And that's Physics?

 

[WannabeNewton]

One Axiom

There is only One mathematical equation
That defines nature truly or absolute
The solution is only =
Or equal
And the lion simply One.
Beyond this simple equation
There is only theoretically division
Complexities faiths and uncertainties
The quantum mechanics of a lost mankind.

=
MJA

Say what?

 

[Pilot7]

One Axiom... The quantum mechanics of a lost mankind.MJA

Planet physics and planet poetry
Surely we have license to live on either, neither or both
tho anyways and always turning about the same sun
held in check by some mysterious, ineffable oath

No doubt, every momentous angle only an allegory
and every sun rise purely theoretical
yet still do our days proceed
a matter also practical

So true 1x1=1 no more, no less than One's division with itself
and perhaps it is rather a lion lying behind the curtain
the wizard but a trick for those on a trek who seek
brains, heart, courage or what we might call certain

But tell me this and tell me true
since when was mankind lost?
and wherever did we lose him?
and whatever were we thinking?

 

[sophiecentaur]

If it's not the cough that carries you off, it's the coffin they carry you off in.
And that's Phisic.

 

[Pilot7]

You can lead a horse to water but you can't make him drink.
And that's physics,=

:rofl:

You can ALSO sing to him... Sooner or later, he will drink! Probably when he forgets himself. Or just gets really thirsty.

But in truth, I suspect the trick of it all lies in timing...

 

[pallidin]

"Time" is a quantifiable measurment of "change"
Without "change" time does not, and can not, exist...

Think about that for a few minutes :)

 

[Pilot7]

"Time" is a quantifiable measurment of "change"
Without "change" time does not, and can not, exist...

Think about that for a few minutes :)

Okay, I'll byte. However, I find both its miraculous event-ness and my ignorance of its true nature remain... unchanged.

Somewhere under the phenomenology of watching a clock (during, for example, a physical experiment) we have an experience like "clock hand pointing to 2" along with the experience of a "memory" (whatever that is) of an experience of it point to 1, possibly also a certain fuzziness in our present experience that seems to corraborate or reinforce our intuition that "another experience is coming and will likely involve the hand point to 3" or some such.

This is what it is happening when we look at the grand daddy of clocks, such as one that measures Cesium decay or whatever it is that they use these days. We have a memory of state A, we have an experience of state B, and that experience itself has a fuzziness or unreliability about it that suggests a state C.

This begs some questions: what (really) is a memory? And how is that the fuzziness of measure in the case of time nevertheless seems to lead us to speculate on some other exact measure?

Notice, I don't bother with the usual question of what is experience here--still a valuable question to answer in physics no doubt, but not the only way to crack this egg.

What is a memory? You are not allowed to make references here to the various neurons of the hippocampus or whatever, for what we mean by memory is the experimenter's memory, a phenomenological state which defines what we mean by experiment results. To require a reference to biology or psychology is thus throw the whole of all experimental physics under the bus of conjecture, since its certainty and veracity can be adduced to be no more than is accorded the current neurophysiological model of brain and memory...

In addition, in all the instances in physics where there is an uncertainty of measurement, there are normally two kinds: those based on epistemic ignorance typically resulting in bell curves for best modelling; and quantum uncertainties, which usually offer further boundary conditions for the uncertainty (eg we know an electron will "exist" within some region according to some probability distribution, but we may know definitively that it is not a certain points. Okay, this sort of uncertainty might be epistemic or metaphysical, depending on one's interpretative preferences for wave collapse and the measurement problem. There is also a third kind of uncertainty that is not really physical, but philosophical, for example regarding certain choices made GRT about paths or the many interpretive issues that result in quantum theory.

But the "fuzziness" of time (or "now") does not look like any of these three other kinds of fuzziness. When we see a clock hand at 2 in a "fuzzy" way, we mean to say not just that it IS probably not 2, but likely closer to 3, even that "it is 3". This is an odd kind of uncertainty, for we find ourselves rather certain of the real result while watching the hand creep forward. I am of course trying to characterize the "flow of time" in a physical way here...

Okay, I've ruminated too much now, and the hour grows late :-)

 

[nasijen]

Time is life.

 

[Selraybob]

But the "fuzziness" of time (or "now") does not look like any of these three other kinds of fuzziness. When we see a clock hand at 2 in a "fuzzy" way, we mean to say not just that it IS probably not 2, but likely closer to 3, even that "it is 3". This is an odd kind of uncertainty, for we find ourselves rather certain of the real result while watching the hand creep forward. I am of course trying to characterize the "flow of time" in a physical way here...

Pilot, I still don't see how all this 'fuzzy' talk has anything to do with Time. It might have something to do with how well we can lock something down and how accurately we can count the changes that the counters are counting, but nothing I see about Time. So even though there are a lot of super smart people who've thought about this a whole lot more than I have. It all still comes down to this:

Change --> Count --> Time --> Speed

It happened it that order, not going backwards from C or little t to get some deep mystical meaning. It started with change. It doesn't matter if it's a movement change or some chemical state change or the number of electrons change. Something's changing.

Then someone saw the changes that seemed to repeat and started counting them. It could be moons or suns or electrons spitting off. Someone saw the sun move, compared it to the end of the earth, and thought, huh, the sun's at the end of the earth.

After people started noticing the changes, they started noticing the ones that repeated, then putting marks on the wall or somewhere to record the counts of those changes. They thought, huh, I think something in this acorn in my head's telling me that I saw that sun over the horizon before now. I'll mark the wall every time I see it, just to make sure my acorn's working okay.

And then some brilliant person went and announced to everyone that all these marks we see on the walls are called Time, and not counts of the sun going down.

And once you had Time and people started dividing the days into little pieces, you started to get speed (and rate, frequency, velocity too) -- the count of distance divided by the so-called change in Time, which is just a count of some counting device. To get speed you needed two counts.

Which is why Heisenberg was right. You can't get speed at anyone time, because you need two counts, and when you divide those two counts, you get the calculated speed BETWEEN the two counting spots, not at the end of one or at the beginning.