What is Time ?

[AusieBob]

What is time ? A question I was asked by a science student set me thinking. Some years ago a brilliant young physicjst, Joao Magueijo

calculated the exact time of the Big Bang but failed to get the deserved kudos for his work, due mainly, I believe to his not explaining the delay between the event and the beginning of time and light, so here I will attempt to do just that.

 

First we need to look at black holes, or rather, what happens at the Schwartschild Radius. It is here that both time and light cease, but

space continues right in to the singularity, so time can not be an element of space, therefore it must be tied somehow to light. Light ceases at that point due to the fact that matter exceeding light speed can neither emit or reflect light, not because light can,t escape the gravitational

force of the black hole, and without light there can be no time.

 

My second argument for time and light being intertwined is thus. Let us put a mirror on a planet 50 light years distant and shine a

light beam on it. That beam will take 100 yars to return. Here I get into the theoretical and send some space craft on the same round

trip. The first will average 50% L.S. It will take 50 years for the journey but find Earth 150 years older on it,s return. That is the 100

years it took the light beam plus the 50 years for the trip. Our second will average light speed for it,s journey, arriving back at the moment

the beam does. Although the travellers would not be a day older they would still have been absent from Earth for 100 years. I believe that

at light speed and above no time would elapse for the traveller.

 

It has been sugested that exceeding light speed would give us reverse time travel, but this is an impossibility as I will attempt to prove.

The third ship will average twice light speed. Arriving back at the moment the beam reaches the mirror our still young spacemen

would be 50 years younger than thier twins left behind. The final voyagers will average 99 times light speed, but still the light beam has

time to go one light year into space. This can be extrapolated out to the millions and still we could never return before the beam left

Earths atmosphere. I believe the above to prove my previous statement that time is an element of light, not space, and that we can

alter time only by increasing our motion by a percentage light speed.

 

Time = motion at the percentage of light speed travelled,, or simply,,, T = M / LS.

 

Back to the beginning and Prof. Joao Magueijo. He stated that the delay between the event and the beginning of light and time was due

to a change of light speed, and although his calculations were correct, it was gravity that caused the delay. The Big Bang took place when

two Super massive black holes collided and thier combined gravity meant that the matter could neither emit or refect light until it had

passed the Schwartschild radius where time and light began.

 

Is this in the realm of Science or Science Fiction. I invite comment.

[swansont]

Your scenario is at odds with the predictions of relativity, but even ignoring that, how will a round trip of 100 LY take only 50 years moving at c/2? 100 LY/c/2 = 200 years.

[juanrga]

What is time?

 

This is a difficult question. Time is, in essence, the evolution parameter of Universe as a whole.

 

Magueijo's ideas are incorrect and outdated. As many others, he is not aware of the difference between the time associated to the generator of time translations K and the x^0 in 4D-spacetime.

[MigL]

Time ceases at the Swartzchild radius of a black hole ??? Tell that to the poor sucker who is yelling at the top of his lungs "STOP ! STOP !" as he plunges into the depths of the gravitational well on his way to meet his demise at or near the singularity.

 

But seriously, time does not stop. We measure time by separation of signals received from the vicinity of the black hole. We measure light signals emitted by the object in the vicinity of the black hole and see the distance travelled per unit time decreasing as the horizon is approached. Unfortunately we are using time signals generated in our 'far-away' frame, if instead we use signals generated by the object in the vicinity of the black hole, we note that they also 'stretch'. In effect if frames are not mixed there is no discrepancy.

As a matter of fact. this time stoppage effect arises when using Swartzchild co-ordinates, but it can be made to disappear using other ( I forget the name ) co-ordinates. An excellent popularization of space-time effects in the vicinity of a black hole is Kip Thorne's 'Black Holes and Space Warps; Einstein's outrageous legacy'.

Edited May 25, 2012 by MigL

[juanrga]

As a matter of fact. this time stoppage effect arises when using Swartzchild co-ordinates, but it can be made to disappear using other ( I forget the name ) co-ordinates.

 

Kruskal & Szekeres coordinates

[between3and26characterslon]

What is time?

 

The best explanation I heard is it's the stuff stopping everything happening all at once

[qft123]

What is time ? A question I was asked by a science student set me thinking. Some years ago a brilliant young physicjst, Joao Magueijo

calculated the exact time of the Big Bang but failed to get the deserved kudos for his work, due mainly, I believe to his not explaining the delay between the event and the beginning of time and light, so here I will attempt to do just that.

 

First we need to look at black holes, or rather, what happens at the Schwartschild Radius. It is here that both time and light cease, but

space continues right in to the singularity, so time can not be an element of space, therefore it must be tied somehow to light. Light ceases at that point due to the fact that matter exceeding light speed can neither emit or reflect light, not because light can,t escape the gravitational

force of the black hole, and without light there can be no time.

 

My second argument for time and light being intertwined is thus. Let us put a mirror on a planet 50 light years distant and shine a

light beam on it. That beam will take 100 yars to return. Here I get into the theoretical and send some space craft on the same round

trip. The first will average 50% L.S. It will take 50 years for the journey but find Earth 150 years older on it,s return. That is the 100

years it took the light beam plus the 50 years for the trip. Our second will average light speed for it,s journey, arriving back at the moment

the beam does. Although the travellers would not be a day older they would still have been absent from Earth for 100 years. I believe that

at light speed and above no time would elapse for the traveller.

 

It has been sugested that exceeding light speed would give us reverse time travel, but this is an impossibility as I will attempt to prove.

The third ship will average twice light speed. Arriving back at the moment the beam reaches the mirror our still young spacemen

would be 50 years younger than thier twins left behind. The final voyagers will average 99 times light speed, but still the light beam has

time to go one light year into space. This can be extrapolated out to the millions and still we could never return before the beam left

Earths atmosphere. I believe the above to prove my previous statement that time is an element of light, not space, and that we can

alter time only by increasing our motion by a percentage light speed.

 

Time = motion at the percentage of light speed travelled,, or simply,,, T = M / LS.

 

Back to the beginning and Prof. Joao Magueijo. He stated that the delay between the event and the beginning of light and time was due

to a change of light speed, and although his calculations were correct, it was gravity that caused the delay. The Big Bang took place when

two Super massive black holes collided and thier combined gravity meant that the matter could neither emit or refect light until it had

passed the Schwartschild radius where time and light began.

 

Is this in the realm of Science or Science Fiction. I invite comment.

 

Time is something that helps us to distinguish between two actions that have happened.. Time is a continuation of progress of events that occur in the past, future and the present.....

 

Is time travel possible???

[the asinine cretin]

Plug for Sean Carroll's book.

 

From Eternity to Here: The Quest for the Ultimate Theory of Time

 

[mindless]

Your introduction has two strands, the first is "what is time?" and the second is a series of speculations about supraluminal travel. The relativistic notion of time is covered brilliantly in the Wikibook called "Special Relativity". The bit on the nature of time begins at link: http://en.wikibooks.org/wiki/Special_Relativity/Spacetime#The_modern_approach_to_special_relativity

 

As for time and light being closely interrelated, this relationship comes from the postulate that the space-time interval is invariant between observers - look at the link above to understand this postulate.

 

This book also has a section on travelling faster than the speed of light, the link is at: http://en.wikibooks.org/wiki/Special_Relativity/Faster_than_light_signals,_causality_and_Special_Relativity

 

It points out that if travel at faster than light speed is possible then either Special Relativity is true or Causality is true but not both. Curiously Causality is less well founded in observation and theory than Special Relativity so if we ever did find a signal travelling at more than light speed my money would be on a violation of Causality...

 

So what is time? Relativity tells us that it fulfils the criterion for being a dimension and common sense tells us that it is involved in change and causality. My guess is that the "time of change" is highly correlated with the dimensional time of relativity but is not the same physical phenomenon.

[studiot]

No one has any proof that the laws of subluminal mechanics can be extended beyond c.

All is supposition at superluminal speeds.

 

Equally when discussing 'time travel' people inherently mean a different form of mechanics (wrongly I think) from that involved in space travel.

To whit they say the train travals from London to Glasgow.

They mean the whole train - all the carriages engine etc.

They don't mean one carriage is removed from the middle of the train and displaced by itself to Glasgow.

 

Yet when people talk of time travel this is exactly the scenario they are proposing by the statement the train travels to Glasgow.

 

 

[Aethelwulf]

This is a difficult question. Time is, in essence, the evolution parameter of Universe as a whole.

 

Magueijo's ideas are incorrect and outdated. As many others, he is not aware of the difference between the time associated to the generator of time translations K and the x^0 in 4D-spacetime.

 

Never mind Maguejo, I'd be concerned with your answer.

 

Time is local - there is no global time in General Relativity. So it cannot be an ''evolution parameter of the universe as a whole''. Time vanishes in GR because world lines are static and diffeomorphism invariance is not even a true time evolution, motion arises as a symmetry of the theory.

[juanrga]

Never mind Maguejo, I'd be concerned with your answer.

 

Time is local - there is no global time in General Relativity. So it cannot be an ''evolution parameter of the universe as a whole''. Time vanishes in GR because world lines are static and diffeomorphism invariance is not even a true time evolution, motion arises as a symmetry of the theory.

 

If you read my message you would notice at least three things: (i) Nowhere in my message I mentioned General Relativity, because the general relativistic concept of time is very far from being fundamental; (ii) I wrote about the generator K (K is not H) and (iii) I differentiated evolution time (sometimes denoted by [math]\tau[/math]) from x⁰.

 

Note: The notation is standard and can be found in papers and books, but for avoiding further misreadings... let me add that [math]\tau[/math] is not proper time and K is not Kelvin.

Edited June 19, 2012 by juanrga

[Aethelwulf]

If you read my message you would notice at least two things: (i) I wrote about the generator K (K is not H) and (ii) I differentiated evolution time (sometimes denoted by [math]\tau[/math]) from x⁰.

 

Note: The notation is standard and can be found in papers and books, but before someone adds some new misunderstanding... let me add that [math]\tau[/math] is not proper time.

 

I don't know what you are arguing. You explicitely said that time is the evolution of the universe - this is wrong. When you quantize the EFE's, you get the WDW-equation

 

[math]H|\psi> = 0[/math]

 

Does not allow a global time translation of the universe.

 

If you read my message you would notice at least three things: (i) Nowhere in my message I mentioned General Relativity, because the general relativistic concept of time is very far from being fundamental;

 

You've edited a part of thus:

 

If you are now talking about ''fundamental things''it would best not to talk about ''the universe as a whole''. Global concepts are less fundamental than the Local concepts. Time is local strictly. You can't talk about ''time for the universe as the whole'' as you put it and I strongly stated why.

Edited June 19, 2012 by Aethelwulf

[juanrga]

I don't know what you are arguing. You explicitely said that time is the evolution of the universe

 

You misquote me. I said: "Time is, in essence, the evolution parameter of Universe as a whole". That is different than what you write above!

 

When you quantize the EFE's, you get the WDW-equation

 

[math]H|\psi> = 0[/math]

 

Does not allow a global time translation of the universe.

 

You've edited a part of thus:

 

If you are now talking about ''fundamental things''it would best not to talk about ''the universe as a whole''. Global concepts are less fundamental than the Local concepts. Time is local strictly. You can't talk about ''time for the universe as the whole'' as you put it and I strongly stated why.

 

I am talking about the fundamental generator of time translations, which is usually denoted by K. I also said that K is not H.

 

The Wheeler & deWitt equation is related to x⁰, but I also said to you that this is not the fundamental time of universe. The WdW is a rather discredited and trivial equation. In more fundamental treatments, it is substituted by a more general and sophisticated equation as the Stueckelberg-Schrödinger equation, for instance,

 

[math]i\hbar \frac{\partial |\Psi\rangle}{\partial \tau} = K |\Psi\rangle[/math]

 

where [math]|\Psi\rangle[/math] is defined in a generalized Hilbert space beyond the scope of the WdW. Here [math]\tau[/math] is Universe time.

Edited June 19, 2012 by juanrga

[Aethelwulf]

I'm sorry, I've never heard of it.

 

 

Since you will be better read than me on the subject, can you tell me how [math]\tau[/math],this evolution parameter defines time? How is it applied to the universe as a ''whole''?

 

I'm reading this right now to get some idea on it http://www.platonia.com/complex_numbers.pdf

Edited June 19, 2012 by Aethelwulf

[juanrga]

I'm sorry, I've never heard of it.

 

Since you will be better read than me on the subject, can you tell me how [math]\tau[/math],this evolution parameter defines time? How is it applied to the universe as a ''whole''?

 

A basic introduction is given at http://en.wikipedia....vistic_dynamics. Therein "coordinate time" is the x⁰ and the "invariant evolution parameter" or "parametrized time" is [math]\tau[/math]. This fundamental time [math]\tau[/math] is defined globally, for the universe as a whole, and it coincides with the quantum mechanical concept of time.

 

Wheeler and DeWitt confounded the "t" in quantum mechanics with the "t" in general relativity and developed the nonsensical WdW equation, which leads to nonsensical claims about a timeless universe...

Edited June 20, 2012 by juanrga

[Aethelwulf]

A basic introduction is given at http://en.wikipedia....vistic_dynamics. Therein "coordinate time" is the x⁰ and the "invariant evolution parameter" or "parametrized time" is [math]\tau[/math]. This fundamental time [math]\tau[/math] is defined globally, for the universe as a whole, and it coincides with the quantum mechanical concept of time.

 

Wheeler and DeWitt confounded the "t" in quantum mechanics with the "t" in general relativity and developed the nonsensical WdW equation, which leads to nonsensical claims about a timeless universe...

 

I have been reading more on this subject and I am not convinced that this is a viable approach for quantum theory in its treatment of gravitational physics. The Hamiltonian and momentum contraints of General Relativity yield the so-called ''nonesensical'' idea's you refer to, the timeless scenarios. However, many physicists feel there is a deep meaning to this, and is rooted much deeper than timeless equations like the time dependant Schrodinger Equation which is the analogue equation of the WDW equation. The reason why is because not only does time vanish but also complexification. The WDW is inherently real and if this approach is true it has massive implications for quantum gravity (many of them I bet are overlooked by scientists today).

 

I'd like to see a more rigorous reason for a time parameter/ evolution parameter or whatever name you wish to dub [math]\tau[/math] (Personally I prefer a Parameterized Time.) . How do you derive the equation above from the WDW-equation? Notice that your complexification in the Stueckelberg-Schrödinger equation is achieved by making mention of time again in your universe. Why should we take it seriously rather than the WDW equation which has been derived from as one might see it, General relativistic first principles? I have read that this evolution parameter may have physical measurable properties. A bizarre statement if [math]t \rightarrow \tau[/math], since [math]t[/math] is not an observable - then it made talk of designing evolution parameter clocks... which is just another clock on the wall? This doesn't mean you can ''observe time''. I blame the wiki article for bad use of language. I have noticed one thing - it all heavily relies on the so called, ''reversibility of time''. Since it is a much abused concept, I am not convinced by this approach one bit - I also notice that the wiki article tries to justify reversibility by noting that antiparticles in a Feynman Diagram appear to move back in time.

 

No self-serving scientist actually believes this though.

 

I'd also like to note that whether you think it is nonsensical or not, timelessness is a growing phenomenon that is being appreciated by more and more physicists. I don't find it nonsensical. I think what is nonsensical is to believe time exists outside of the mind, objectively and independently of a recording device.

 

I notice also in the WIKI article, it says as a hypothesis:

 

 

''Hypothesis I

Assume t = Einsteinian time and reject Newtonian time.''

 

 

What's hypothetical about this? This is what has happened. Einsteinian time overthrew Newtonian time a while back now. Newtonian time consisted of absolute clocks in the universe - he also perceived time as something which inexorably flowed from past to future. Both these concepts have been shown to be the wrong kind of view of time, so I don't understand why this all stands on ''hypothesis 1'', also, even if one considers the coordinate time, it's use is really only valid for local events. Einstein showed that whilst you can view time as a component of the metric, his general relativity was in essence rooted from timeless propositions, world lines which where static for instance.

 

 

Interestingly, there is not even a past or future in relativity. In physics today most of us come to realize all you can really talk about is a present moment which is unceasing. That's perhaps the most solid kind of time you may ever be able to talk about.

 

 

Edited June 20, 2012 by Aethelwulf

[juanrga]

How do you derive the equation above from the WDW-equation?

 

I emphasized in my previous message #14 (which you read and replied) that the SS equation is more fundamental and general than the WdW equation. I did also explicit that the SS equation is "defined in a generalized Hilbert space beyond the scope of the WdW"... Evidently your above question is nonsensical.

 

You also misread the Wiki article, which shows that it is not my fault.

Edited June 21, 2012 by juanrga

[Aethelwulf]

 

 

You also misread the Wiki article, which shows that it is not my fault.

 

Quite possibly so.

 

I emphasized in my previous message #14 (which you read and replied) that the SS equation is more fundamental and general than the WdW equation. I did also explicit that the SS equation is "defined in a generalized Hilbert space beyond the scope of the WdW"... Evidently your above question is nonsensical.

 

 

Bolded by me.

 

How so?

 

Also you make a point saying the SS equation is defined in a Hilbert Space beyond the scope of the WDW equation. It is true the wave function of the WDW equation is no longer a spatial function, however, the operator H is a relativistic case which does act on the Hilbert Space.

 

You've made no comments on the complexifying of the SS equation, or the deep phyiscal meaning I purported to when physicists view quantum gravity under the non-complex wave function.

 

( I realize in post 14 I said the time dependant SE is the analogue of the WDW equation - this is a mistake, I meant the time independEnt case).

[abdullah faris]

Your scenario is at odds with the predictions of relativity, but even ignoring that, how will a round trip of 100 LY take only 50 years moving at c/2? 100 LY/c/2 = 200 years.

 

why not we consider time just as a massurement tool and not relate it to any thing as directly propportional. my day is a lenght which i describe as 24 hours but but a turtle might feel it as 12 hours and thats why he lives like that. some of the lenghts we define as meters,inches, and so on but for an aunt my mile could pose as a light year. so a massuring tool shouldnt be given more respect then this . why cant we say if our earth stay static or i dont travel with it while moving in the orbit and also i slouldnt feel any atmospheric pressure on me so i might not even go OLD and not die. these constants arround me are killing me which i describe in time..

[pmb]

why not we consider time just as a massurement tool

That's the way most people percieve it to be, including myself.

 

and not relate it to any thing as directly propportional. my day is a lenght which i describe as 24 hours but but a turtle might feel it as 12 hours and thats why he lives like that.

That's called personal time which is seperate and distinct than objective time, which is the time that we all agree on.

[Aethelwulf]

That's the way most people percieve it to be, including myself.

 

 

That's called personal time which is seperate and distinct than objective time, which is the time that we all agree on.

 

I concur, I see it nothing as a good measurement tool. And this personal time has also been called Asymptotic Time.

[swansont]

why not we consider time just as a massurement tool and not relate it to any thing as directly propportional. my day is a lenght which i describe as 24 hours but but a turtle might feel it as 12 hours and thats why he lives like that. some of the lenghts we define as meters,inches, and so on but for an aunt my mile could pose as a light year. so a massuring tool shouldnt be given more respect then this . why cant we say if our earth stay static or i dont travel with it while moving in the orbit and also i slouldnt feel any atmospheric pressure on me so i might not even go OLD and not die. these constants arround me are killing me which i describe in time..

There are a lot of things that depend on people agreeing what time it is, at varying levels of precision. From meetings, to commerce requiring time-tags, to communications, to GPS.

[burhan hafiz]

Time is a thing that never stops but slows down ...... And never comes back

[Mynameson]

LOL I guess the geniuses gave a reply to that question..It's the forth dimension and the one that doesn't let two events to happen at the same time.It's completely another thing our perception of time.There was a theory that assumed that time was something that couldn't be manipulated that it was time which made the events that the events didn't happen by gravitational force or else but time had to go that way so it did. But its a crap theory at last.