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What makes the time go?





jajarvin
What makes the time go?

Why does the time not stop?
Bikerman
What makes you think that it moves? If you take a pure relativistic perspective then time is intertwined with space and doesn't move at all. All the time that has been and all the time that will be is already out there - it is US that move through IT, and the faster we move through space the slower we move through time (and via versa) with the sum of the two speeds always being the speed of light (c).
Pippo90
The right physical answer should be entropy.

http://en.wikipedia.org/wiki/Entropy_(arrow_of_time)
kelseymh
jajarvin wrote:
What makes the time go?


Sometimes a pendulum, sometimes a spring, and nowadays usually batteries.

Quote:
Why does the time not stop?


Because someone pulls the counterweights, or winds the spring, or changes the batteries. When they forget, the clock stops.
kelseymh
Bikerman wrote:
What makes you think that it moves? If you take a pure relativistic perspective then time is intertwined with space and doesn't move at all. All the time that has been and all the time that will be is already out there - it is US that move through IT, and the faster we move through space the slower we move through time (and via versa) with the sum of the two speeds always being the speed of light (c).


I think you mean the sum in quadrature, right? The interval (s) is determined by the Minkowski sum ds^2 = dx^2 - dt^2 (c=1, of course), and the "interval velocity" is determined the same way.
Bikerman
No I don't think so. Entropy is one of the only physical 'systems' that has a clear direction. Most physics works both ways in the temporal axis with no obvious distinction. So Kinematics formulae describe motion but don't 'care' about the direction of time - there is no inherent direction in the equations. This symmetry (T-Symmetry) applies to much of physics - but not entropy - or more precisely the 2nd law of thermodynamics. . entropy has a direction - run the time axis one way and it increases, run it the other way and it decreases..hence the 'arrow of time'.
BUT this is not so straightforward - this is actually an area which I studied many years ago - as a problem in infomatics/computer science rather than a pure physics problem.
This is actually a very 'deep' area in computing and many technical areas have Shannon entropic treatment of information flows close to their heart - quantum computing, reversible algorithmic & heuristic interplays....lots of stuff that is at the academic edge of my subject - once I was able to talk intelligently about papers of the time, though certainly not a 'player'. Nowadays I've completely lost touch with this area of my subject and I'll probably get a visit from the Computing Police if I try to go too deep - bullshitting without a license is still a pretty serious matter in Computer Science - and NEVER, EVER call a Computer Scientists someone in 'IT', or, worse, 'Communications' unless you have a strong stomach and are able to watch grown men (mostly) alternating between poles of extreme anger and ferocious Pedagogical efforts, aimed at showing you just how insane any such association is...
A simple way in is the Maxwell Demon thought exercise.
Maxwell imagined a 'demon' with a simple rule, standing as doorkeeper between two areas. The rule is - fast pass and slow go. So particles going fast are allowed through, slow ones are 'bounced'. The scientifically literate will immediately realise that this is just another way of saying 'hot goes through' and 'cold reflects back'. The effect would be to reverse entropic flow and thus completely bollox the arrow of time...OR SO IT MIGHT SEEM....
You now get into the shallow end of a whole set of positions and arguments that are still very much live, and in some cases, still very 'hot'. I know at least 2 academics who ended a 15 year friendship over this question and, last I heard, were resolute in their determination to carry this feud to the grave.
You start with simple model of phase space using the Boltzmann metric (basically the log of phase space is Boltzmann's classic 'measure' of entropy). This can be related to the Shannon informational content of that same phase space (which we actually call the Shannon Entropy, and here is starts to get interesting, complicated and mathematical all at once.

That means I can't even outline the discussion here because, and let me say this clearly:
THERE IS NO DAMNED WAY TO REPRESENT THE MOST IMPORTANT BLASTED LANGUAGE WE HAVE IN THIS BENIGHTED APE-MAN SYMBOLOGY AS MEDIATED BY THE INFORMATIONAL STRAIGHT-JACKET OF THE BCC FORMATTING SYSTEM APPLIED TO A SYSTEM OF CHARACTER CODING THAT WAS ANCIENT WHEN IT WAS NOTABLE MAINLY BECAUSE IT REPRESENTED THE FIRST ACT OF NEO-COLONIAL CONTROL OF IT STANDARDS BY THE SEPPOs, SHITTING BRICKS OVER SPUTNIK, IN THE TIME WHEN I WAS A FRESH-FACED STUDENT 3 DECADES AND MORE AGO...BLOODY GOD DAMNED ASCII BOLLOX.....
(Sorry, just having a little swipe at the powers that be - I keep raising the possibility of putting in a system which will encode either MATHML or LaTeX and thus allow us to conduct civilised discourse without having to put everything on my website and ferry-it in as graphics...)

The maths is quite pretty and Shannon arrives at his equations of Information content/limit/uncertainty in the same basic way that Boltzmann arrived at thermodynamic measures of the same basic notions - Boltzmann considered particles in space and considered how many states a system could be in - the microstates of phase space - which gives a measure of how ordered it currently is (how many ways could the current arrangement arise? The fewer, the less entropy, the more order). Shannon considered coin tosses and modelled what we can say, in information terms, about the repeated coin toss, as modelled mathematically, This is a simple model of entropy where 1 toss = 1 'bit' of entropy, 2 tosses = 2 entropy bits, and so on with the bit value of entropy being the same as the number of tosses. You then expand the model to tri-state, multi-state and, ultimately take it to the other extreme of infinite states. If the maths works across these, then you have a robust model. Boltzmann and Shannon both came up with robust models which are fun to play with and even more fun to relate to each other.....but WE NEED ALGEBRA FOR THAT Smile

Bikerman
kelseymh wrote:
Bikerman wrote:
What makes you think that it moves? If you take a pure relativistic perspective then time is intertwined with space and doesn't move at all. All the time that has been and all the time that will be is already out there - it is US that move through IT, and the faster we move through space the slower we move through time (and via versa) with the sum of the two speeds always being the speed of light (c).


I think you mean the sum in quadrature, right? The interval (s) is determined by the Minkowski sum ds^2 = dx^2 - dt^2 (c=1, of course), and the "interval velocity" is determined the same way.

LOL...I forgot for a moment that we had a real scientist looking at my rantings Smile Yes, of course, you are quite correct - I was guilty of two scientific sins there - firstly forgetting to check stuff that has been in my head with no company for a long time and therefore likely to be inaccurate, if not to have 'evolved' into an informational state known as Bolloxium Sollipsisium -
and more unforgivably, thinking it didn't matter if I over-simplified to the point of misrepresenting....oh, the shame...
Smile Nice to hear from you Mike - hope all is well with you and yours.?
kelseymh
Bikerman wrote:
kelseymh wrote:
Bikerman wrote:
What makes you think that it moves? If you take a pure relativistic perspective then time is intertwined with space and doesn't move at all. All the time that has been and all the time that will be is already out there - it is US that move through IT, and the faster we move through space the slower we move through time (and via versa) with the sum of the two speeds always being the speed of light (c).


I think you mean the sum in quadrature, right? The interval (s) is determined by the Minkowski sum ds^2 = dx^2 - dt^2 (c=1, of course), and the "interval velocity" is determined the same way.

LOL...I forgot for a moment that we had a real scientist looking at my rantings Smile Yes, of course, you are quite correct - I was guilty of two scientific sins there - firstly forgetting to check stuff that has been in my head with no company for a long time and therefore likely to be inaccurate, if not to have 'evolved' into an informational state known as Bolloxium Sollipsisium -
and more unforgivably, thinking it didn't matter if I over-simplified to the point of misrepresenting....oh, the shame...
Smile Nice to hear from you Mike - hope all is well with you and yours.?


Well, but busy. If I were simplifying, I would have written something quite similar, maybe along the lines of "the combination of the two speeds is fixed, equivalent to the speed of light." Though turns out that for a null worldline (like light), the "interval speed" is identically zero in all frames (because of that minus sign).
Bikerman
And the next question is usually the one that seems easy to the person, and to me, who is an autodidact amateur, is a pig to explain properly (unless they have at least enough maths to follow world-lines - diagrammatically or algebraically - and they don't, otherwise they wouldn't be asking Smile
'How does a photon experience time', or some variation on that apparently reasonable question. The answer I give - that you can't actually construct a frame of reference for a photon at c - well, they normally feel cheated or lied to. It is still the best answer I can give though. The more exciting answers - no time, it goes from emission to absorption in zero subjective local time, even across the galaxy - is OK until you actually LOOK at the maths rather than just shift signs around the equal sign....I don't think the answer is right, but I don't know how it could be explained better. Its a bit like 1/0 - easy, and wrong, to go with the 'lies to children' answers of 'infinity', more difficult to explain that it is actually a question that admits of no simple answer because it busts the system for giving such answers and takes us into new areas...
kelseymh
Bikerman wrote:
And the next question is usually the one that seems easy to the person, and to me, who is an autodidact amateur, is a pig to explain properly (unless they have at least enough maths to follow world-lines - diagrammatically or algebraically - and they don't, otherwise they wouldn't be asking Smile
'How does a photon experience time', or some variation on that apparently reasonable question. The answer I give - that you can't actually construct a frame of reference for a photon at c - well, they normally feel cheated or lied to.


Zero subjective time is a mathematically defensible answer: you can get it with a simple limit analysis. Since t' = t / sqrt(1 - (v/c)^2), t = sqrt(1 - (v/c)^2) t' (where t is proper time and t' is observer time). In the limit as v -> c, t goes smoothly to zero for any observer's time interval.

Your answer about not being able to construct a photon rest frame, and therefore the question is unanswerable, is formally correct, and in fact quite useful in a different context! In weak decays of particles, a neutrino and electron (or muon) are produced together. For example, pi^+ -> nu(e) e+ or nu(mu) mu+. The weak interaction can _only_ produce left-handed helicity particles (the spin is opposite the momentum direction).

But the pi^+ is spin zero, so the neutrino and electron have to have opposite spins, which means they have the _same_ helicity (since the momenta are also opposed in the pi^+ rest frame). That violates the way the weak interaction works, and therefore should not be possible. But for the massive electron (here a positron), you can boost into a frame in which the momentum flips direction, and the electron has the "right" helicity in that frame.

Why do I bring this up? Well, for the case of a massless neutrino, you _can't_ boost into or through the rest frame (it doesn't exist)! Therefore, the neutrino is never produced with the "wrong" helicity, while the electron (positron) is.
Bikerman
That's really interesting - I've learned something about particle production and, better, have a new inkling of another way of looking at the overall picture which tickles me. I've been wrestling with the basics of quantum theory in Penrose' 'Road to Reality', so the idea of looking through Relativistic concepts at quantum events is appealing and somehow satisfying.

Hmm, I know you can get to zero tune using the Lorentz frame conversion factor and equating c and v, but it somehow jars and offends me at a level which I can't entirely explain. It's a bit like the first time I came across re-normalization - I was offended by the very notion. It looked like a horrible fudge and made everything ugly. I/m still not comfortable with the notion (I know what Feynman would have said - I can almost hear him - "Just measure & compute, and don't imagine you actually understand it....nobody does". He was an incorrigible old egotist, and don't I miss him for all that..I started to learn physics for real using his lecture series long after school and college).
spinout
Hm, this might riddle a bit; can you be at several places at the same time?
Nyasro
Its a Nature controlling all of us including Time , I think So!
Bikerman
No.
kelseymh
spinout wrote:
Hm, this might riddle a bit; can you be at several places at the same time?


No. That requires infinite velocity in your own rest frame, and is therefore excluded.
asnani04
For the answer, you'll have to dwell into Relativity.
LxGoodies
Bikerman wrote:
the faster we move through space the slower we move through time


This reminds me of a discussion on another forum about space travel. SF-authors always seems to assume, that travel to distant star systems would require several generations of astronauts on the ship, growing up for centuries, unless there is some magic device available, like warp engine or worm holes to speed up the travelling.

Now suppose it would be acceptable to travel like 2 years..

Take 253 days to accelerate at 1G to near c.. and 253 days to come to a stop again.. If we take the full 2 years to travel, 224 days in ship time would remain, to travel at some speed, near c. If you would just sufficiently approach v=c, would it be possible to reach any place in the Milky Way, within these 224 days ? It would make colonisation of space feasable..

Lx
kelseymh
LxGoodies wrote:
Bikerman wrote:
the faster we move through space the slower we move through time


This reminds me of a discussion on another forum about space travel. SF-authors always seems to assume, that travel to distant star systems would require several generations of astronauts on the ship, growing up for centuries, unless there is some magic device available, like warp engine or worm holes to speed up the travelling.


One of the reasons for that is to try to preserve "simultaneity" in the face of relativity. You can certainly travel relativistically, and reach anywhere in the Milky Way (in fact, anywhere in the observable Universe!) in a reasonable amount of proper time (say, a few years).

The problem, as I think you know, is that the duration of your trip for home-bound observes becomes arbitrarily long. For colonists on a one-way trip, that's not a big deal. However, if the author is trying to construct an "empire", where the travelers can communicate with the home world, and can both leave relatives/family behind and return to them after travel, relativity is a real downer. You go off to explore Sagittarius A* for a year or two, and when you get back your great-great-great-great-grandchildren are there to say hello.

So, if you want to explore arbitrary distances, you either need to use "magic" (wormholes, or give up relativity) or your accept that the journey is absolutely one way.
ashu_g
Einstein has already proved that time varies from observer to observer.
To me time seems like a fractal. A perception of 1 minute for us might be eternity for an ant. On the other hand nothing possible might change in a rocky in a minute (which might seem rather devoid of activity to us) but is frantic with activity if seen over 1000 human years (formation of canyons etc).
So i guess time has practically not moved for someone in the higher order of the fractal while looking at someone in the lower order.
Besides, seconds, minutes, years are human defined references for time.
Bikerman
What have fractals got to do with this? Different doesn't mean fractal. Fractal has a specific meaning - a set in which the members have fractal dimensions greater than their topological dimensions. Time is unidimensional (if current physics is correct) with no topology as such (or a linear topology if you like) and the very concept of 'fractal time' therefore would seem to me to be gibberish.
spinout
So if I am a 3 dimensional creature I can be at a 2 dimensional world at several places at the same time, and a 4 dimentional creature could do the same in a 3 dimenstional world I guess. Or is this wrong?
kelseymh
spinout wrote:
So if I am a 3 dimensional creature I can be at a 2 dimensional world at several places at the same time, and a 4 dimentional creature could do the same in a 3 dimenstional world I guess. Or is this wrong?


It's wrong.
spinout
Well a 3 dimensional ascpect of a 2D world is correct atleast - but the 4D to 3D is harder to imagine, still there is a lot of movies taken up the 4D to 3D aspect, and the graphics look a bit odd. I suppose the mathematic idea of how such an aspect would look like gets a bit funny looking, and especially on the moviescreen.
Bikerman
The mathematics are simple(ish) but visualising is a different issue - you can't visualise 4D in a 3D world. All you can do is give analogies.
dansm01
What makes time go is the expansion of the universe. Since the big bang, time and space have expanded to the current size, which is around 14 billion light years. While it's hard for we humans to experience space expansion, in the time dimension it's obvious. In the universe, there's more time now than there was a year ago. In fact, in the time dimension, we're located at the very edge of the universe, between being and nothingness. We're riding the crest of the time wave, as the universe expands to god-knows-where.
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