Time Explained

[ChildInAZoo]

I am just feeling around here..Time to dig out the Julian Arbour article I think.

I think that you mean Julian Barbour. I have looked at some of his work with manifolds and trying to make them time-free, as it were. Unless (and sometimes even if) one is really good at math, it is mind-numbing stuff. I am sure that he has some more accessible stuff out there. He is much more of an anti-realist about time than I am.

[Brain Man]

I am just feeling around here..Time to dig out the Julian Arbour article I think.

I think that you mean Julian Barbour. I have looked at some of his work with manifolds and trying to make them time-free, as it were. Unless (and sometimes even if) one is really good at math, it is mind-numbing stuff. I am sure that he has some more accessible stuff out there. He is much more of an anti-realist about time than I am.

Barbour..its been a while..I found the original new scientist article...from ten years ago..(where did the time go ?). In it he talks about platonia which im still trying to figure and a distribution of localised "time capsules"

The man himself, this should be interesting..

[Brain Man]

MrJobby, I am also very interested in this subject, and I don't claim to be an expert. I'm more of an enthusiastic seeker of knowledge.

It appears to me that time may exist, for us, as both a subjective and objective thing. We create our perception of time by having experiences. When you write "Time is an internal and localised self-reference," it sounds like that's what you're talking about. Does the past exist outside of our subjective experience?
For us, as perceivers, the past has already happened; it exists in the form of memories. We can look at what exists in present tim and attempt to "connect the dots" to put together what has happened since the Big Bang, since Jesus came on the scene, since Darwin, Einstein, whatever, but we are still doing it from here and now and considering what happened there and then.

Does time exist outside of our subjective experience? I'm more than willing to believe that's true, but, if it is true, how do we define and describe the characteristics of time other than it exists in a context that includes space, the two go together. In a way, this reminds me of trying to understand something like gravity. We know something called gravity exists because at least some of its attributes can be demonstrated in the real world, but do we understand gravity? Not yet...

Ive no idea how to do that, but maybe how the brain does it, is a good place to begin.

This is one of the best so far. Most models for the brain and time cover the second range. This one by some respected neuroscientists covers our long term perception of time.

http://ntp.neuroscience.wisc.edu/facult ... pton10.pdf

Basically they propose that the hippocampus builds a linear narrative of time within our minds that lasts about a season, which is consolidated by the day night cycle in a conveyor belt manner...first in, last out over a season..then its shunted off the conveyor to remain for long term recall.

so we have a linear sense of time that long. It makes sense as we had to evolve a planning capacity which could get us through a winter season..

Also try to remember a few things you did in the last three months. You can feel the sequence. Then try and remember a few things you did before the winter. It harder to run that into a linear sequence.

[Xamonas Chegwé]

I am just feeling around here..Time to dig out the Julian Arbour article I think.

I think that you mean Julian Barbour. I have looked at some of his work with manifolds and trying to make them time-free, as it were. Unless (and sometimes even if) one is really good at math, it is mind-numbing stuff. I am sure that he has some more accessible stuff out there. He is much more of an anti-realist about time than I am.

He does mean Barbour. I have his book, The End Of Time. It is interesting but very heavy going if you are not at least a little familiar with relativity, QM and a lot of other stuff. For a pop-sci book, it shoots far over the head of its target audience. I just finished reading it for the second time and it made a lot more sense than the first time through - but it still hurt my head in places! The trouble is that he has excised most of the maths from the topic in order to try and make it accessible - personally, I would have found a few more formulae would have made it more accessible.

[Brain Man]

A discusson on barbours theory here.

http://lesswrong.com/lw/qo/relative_con ... ion_space/

If i have got this right a barbour "time capsule" could be any kind of space which is reliant on its own point of self reference..or alpha point as he puts it.

[Brain Man]

I am just feeling around here..Time to dig out the Julian Arbour article I think.

I think that you mean Julian Barbour. I have looked at some of his work with manifolds and trying to make them time-free, as it were. Unless (and sometimes even if) one is really good at math, it is mind-numbing stuff. I am sure that he has some more accessible stuff out there. He is much more of an anti-realist about time than I am.

He does mean Barbour. I have his book, The End Of Time. It is interesting but very heavy going if you are not at least a little familiar with relativity, QM and a lot of other stuff. For a pop-sci book, it shoots far over the head of its target audience. I just finished reading it for the second time and it made a lot more sense than the first time through - but it still hurt my head in places! The trouble is that he has excised most of the maths from the topic in order to try and make it accessible - personally, I would have found a few more formulae would have made it more accessible.

I havent seen enough of his work to understand if the time capsules are generalized outside of our big bang universe concept and applied anywhere else. Does he propose that any physical system which relies on its own point of self reference be considered to have an alpha point ?

i.e. Harley Borgais

http://www.freeornottobe.org/freeornott ... ivity.html

(if i intepreted him right), proposes that time dilation and hence an alpha point would occur at the south pole of a dipole ...in relation to the north.

Or that a black hole could that be an alpha point for our galaxy ?

[Brain Man]

Farsight..come back..

youre the time expert...Help us out with Barbours "Alpha points" ....

[Brain Man]

Childin the Zoo...Dont go away.. do u understand Barbours alpha points ?

[Brain Man]

ahh well it was worth a try.

I'll leave this for farsight if he returns.

http://www.physorg.com/news185104066.html

Apparently black holes determine and regulate the structure and growth of their galaxies by their spin. OK astronomy is not my subject but im wondering if this theory is true, the the black hole can be considered an alpha point for a galaxy, because a single point which regulates the spin of the stars in that galaxy is then controlling the motion of that galaxy ?

[b]Black hole spin may create jets that control galaxy

February 11, 2010 by Morgan Bettex

An artist's drawing shows a large black hole pulling gas away from a nearby star. Image Credit: NASA E/PO, Sonoma State University, Aurore Simonnet

(PhysOrg.com) -- Scattered throughout every galaxy are black holes, regions that gobble up matter and energy. Although we can't see black holes, scientists can infer their size, location and other properties by using sensitive telescopes to detect the heat they generate. This heat, which we see as X-rays, is produced as material spirals around a black hole faster and faster until it reaches a point of no return -- the "event horizon" -- from which nothing, not even light, can escape.

In addition to a galaxy’s collection of black holes, which includes black holes up to 10 times the sun’s mass, there is a supermassive black hole embedded in the heart of each galaxy that is roughly one million to one billion times the mass of the sun. About 10 percent of these giant black holes feature jets of plasma, or highly ionized gas, that extend in opposite directions of the black hole. By spewing huge amounts of mostly kinetic energy, or energy created by motion, from the black holes into the universe, the jets affect how stars and other bodies form, and play a crucial role in the evolution of clusters of galaxies, the largest structures in the universe.

“This black hole in the center of the cluster is affecting everything else in that cluster,” said Dan Evans, a postdoctoral researcher at MIT Kavli Institute for Astrophysics and Space Research (MKI), who studies supermassive black holes and their jets. Because a jet gently heats the gas it carries throughout a galaxy cluster, it can slow and even prevent stars, which are created by the condensation and collapse of cool molecular gas, from forming, thereby affecting the growth of galaxies, Evans explained. “Without these jets, clusters of galaxies would look very different.”

How these jets form remains one of the most important unsolved mysteries in extragalactic astrophysics. Now Evans may be one step closer to unlocking that mystery.

The importance of spin

For two years, Evans has been comparing several dozen galaxies whose black holes host powerful jets (these galaxies are known as radio-loud active galactic nuclei, or AGN) to those galaxies with supermassive black holes that do not eject jets. All black holes — those with and without jets — feature accretion disks, the clumps of dust and gas rotating just outside the event horizon. By examining the light reflected in the accretion disk of an AGN black hole, he concluded that jets may form right outside black holes that have a retrograde spin — or which spin in the opposite direction from their accretion disk. Although Evans and a colleague recently hypothesized that the gravitational effects of black hole spin may have something to do with why some have jets, Evans now has observational results to support the theory in a paper published in the Feb. 10 issue of the Astrophysical Journal.

While researchers know that the mass of a black hole is intimately linked to the galaxy in which it is located, they have, until now, known little about the role of its second fundamental property — spin. With this paper, Evans asserts that spin is crucial to understanding the dynamics of a black hole’s host galaxy because it may actually create the jet that regulates the growth of that galaxy and the universe.

“It’s the first convincing galaxy of this type seen at this angle where the result is pretty robust,” said Patrick Ogle, an assistant research scientist at the California Institute of Technology, who studies AGN. Ogle believes Evans’s theory regarding retrograde spin is among the best explanations he has heard for why some AGN contain a super-massive black hole with a jet and others don’t.

Although Evans has suspected for nearly five years that retrograde black holes with jets are missing the innermost portion of their accretion disk, it wasn’t until last year that computational advances meant that he could analyze data collected between late 2007 and early 2008 by the Suzaku observatory, a Japanese satellite launched in 2005 with collaboration from NASA, to provide an example to support the theory. With these data, Evans and colleagues from the Harvard-Smithsonian Center for Astrophysics, Yale University, Keele University and the University of Hertfordshire in the United Kingdom analyzed the spectra of a supermassive black hole with a jet located about 800 million light years away in an AGN named 3C 33.

Astrophysicists can see the signatures of X-ray emission from the inner regions of the accretion disk, which is located close to the edge of a black hole, as a result of a super hot atmospheric ring called a corona that lies above the disk and emits light that an observatory like Suzaku can detect. In addition to this direct light, a fraction of light passes down from the corona onto the black hole’s accretion disk and is reflected from the disk’s surface, resulting in a spectral signature pattern called the Compton reflection hump, also detected by Suzaku.

But Evans’ team never found a Compton reflection hump in the X-ray emission given off by 3C 33, a finding the researchers believe provides crucial evidence that the accretion disk for a black hole with a jet is truncated, meaning it doesn’t extend as close to the center of the black hole with a jet as it does for a black hole that does not have a jet. The absence of this innermost portion of the disk means that nothing can reflect the light from the corona, which explains why observers only see a direct spectrum of X-ray light.

The researchers believe the absence may result from retrograde spin, which pushes out the orbit of the innermost portion of accretion material as a result of general relativity, or the gravitational pull between masses. This absence creates a gap between the disk and the center of the black hole that leads to the piling of magnetic fields that provide the force to fuel a jet.
[/b]

[Farsight]

"Since 1967, the second has been defined to be the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. This definition refers to a caesium atom at rest at a temperature of 0 K (absolute zero), and with appropriate corrections for gravitational time dilation."

Can someone tell me what 'at rest' means? Edit: I'm assuming that it means at rest in the chosen referenceframe, so the length of a second is only valid for that frame of reference?

I sure that's right. Note that the quote above comes from the official definition which you can find on wiki.

[Farsight]

Having read a bit more of the posts on this, as far as I can see Farsight is just stating exactly what I thought time was, a property of energy. By all the anti posts, it appears that people believe this to be wrong. So how come nobody has explained what time ACTUALLY IS? Surely if you disagree with his claims, you can enlighten me? I'd be interested to know where I've been going wrong.

Good one, mistermack. I haven't really said anything new here. It goes as far back as Aristotle. There's also Presentism from 1908. There's different ways to express it of course, but it always comes back to time is a measure of change or motion. And of course energy causes motion.

[Farsight]

What a weird co-incidence, i was pointing out some problems to Amrit on a paper he hotlinked (on time and the brain) in facebook last week, then thought i need to track down John duffield and get a full grip of his take on time. I do get the impression it really is a small club working on original stuff these days.

I think there's quite a lot of people, but you don't get to hear about them. I know ex-CERN physicists who struggle to get papers into journals, and when they do, it doesn't make it to the media. Instead you get mags like New Scientist saying things like "string theory is the only game in town". And of course stuff like time travel and other such woo sells copies.

Sorry to press you on this, but basically would it be right to say that its periodicity that we are using as the main marker to create our sense of time..i.e. Even if we aren't using periodicity, we still take a reference of some kind and then basically keep repeating it?

I'd say so. I talk about motion as the most fundamental thing, but the associated periodicity is what gives us our markers. For example we count 9,192,631,770 incoming microwave peaks to define a second. The microwave radiation has to move, and you need something periodical that you can count to define a second.

Or how would you describe the process that humans go through to assign time?

I'd say time is always gauged with motion, and the motion is usually periodic. For example we count 60 seconds to define a minute, 60 minutes to define an hour, 24 hours to define a day, which of course relates to the periodic motion of the spinning earth. And it's now the year 2010. The earth has moved round the sun 2010 times (or is that 2009 times?) since our reference point.

Also why does time need to be a dimension at all then?

Because things move, because time is a cumulative measure of motion, and because you need it to specify an event. But it's only a dimension in the sense of measure. That's what a dimension used to mean. Nowadays people assume it means something you can move through.

[Farsight]

Let’s move on to sound. Imagine a super-evolved alien bat with a large number of ears, like a fly’s eye. This bat would “see” using sound, and if it was sufficiently advanced it might even see in colour. But we know that sound is pressure waves, and when we look beyond this at the air molecules, we know that sound relies on motion.

I will concede that, though I fail to see how your examples support some would-be Grand Unified Theory based on classical mechanics.

You get rather a different view of time as something that's an emergent property of motion through space. This then makes you shift your position on special relativity from space-time to space-motion, and you get a different handle on Minkowski's wrench, relating the magnetic field to motion through an electric field so you can "see" the geometric disposition of the electron's electromagnetic field. Then you read On Physical Lines of Force and see Maxwell's vortices and realise he got it back to front - they're not in the intervening space, they're what the particles are, and you bump in the Einstein-de Haas effect that demonstrates that spin angular momentum is the same as classical angular momentum. You get a different take on GR too, and see what Einstein was saying about VSL. Basically you bump into all sorts of things in a cumulative fashion and they add up to something coherent and very interesting.

You can also feel heat. Touch that stove and you feel that heat. We talk about heat exchangers and heat flow as if there’s some magical mysterious fluid in there. And yet we know there isn’t. We know that heat is another derived effect of motion.

However, that's atom-scale random motion.

No problem.

Taste is chemical in nature, and somewhat primitive. Most of your sense of taste is in fact your sense of smell. Do you know how smell works? Look up olfaction and you’ll learn about molecular shape. But the latest theory from a man called Luca Turin says it’s all down to molecular vibration, because isomers smell the same. That’s motion again.

That's demonstrably false. Chirality (chemistry) - Wikipedia There are several substances whose mirror-image variations have different smells and tastes. That agrees with the lock-and-key chemical-receptor theory and not with the molecular-vibrational-mode theory...

Fair enough. But I did mention molecular shape, and was simply reporting on what Luca Turin was advancing. See http://en.wikipedia.org/wiki/Vibration_ ... _olfaction. The point I was trying to make was how important motion is as a prelude to time. And even if Luca Turin is entirely wrong, motion is very important.

[Farsight]

So what do you think about all this. Do you think time is as irrelevant to fundamental physics as farsight proposes?

I don't think time is irrelevant, Mr Jobby. Just that it isn't what many people think it is. It's a cumulative measure of motion through space. Time exists, just like heat exists, but like heat, it's an emergent property of motion, and you can't move through it.

[Farsight]

..but do we understand gravity? Not yet...

Don't be too sure about that.