The present time

[md65536]

Perhaps someone could take up the banner of discussing how "the present" (or "it's always now") isn't a tautology and can be quantified, in keeping with sound physics principles

I disagree with this.

 

The phrase "it's always now" implies a moment referred to by "it", which is implicitly "now".

"Now is always now" is a tautology, as long as "now" is defined.

Further, "now" or "the present" is defined relative to an observer and a specific observation (ie. a point in spacetime and a frame of reference for the observer whose lightcone's apex is at that point). Anywhere that an observer can make a statement about the present (referring to the spacetime location of the observer), the present is defined.

So it's a tautology according to any observer.

Experimentally, how could you ever find a counterexample???

 

 

On the other hand...

 

It can easily be made not a tautology, but to do so you must speak of two different possible "presents"... ie where "it" refers to something other than "now", for example to different spacetime points or frames of reference.

"Tomorrow is now" or "Tomorrow will soon be now" is not a tautology (tomorrow's present can be observed in different ways depending on the observer's frame of reference and won't be the same as today's present).

"Your present is my present" is not a tautology.

But I think these cases are excluded by the implicit meaning of "the present" (which is that it refers to some single moment or Cauchy surface which is not universally experienced).

 

 

Technically, a person does not have one single spacetime location and frame of reference, and so just as "the present" isn't the same for different people, it's not the same throughout a person. So while we can define a "present" for a person by a single point, that present is only approximate for the whole person.

[owl]

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Moderator Note

You wrote this knowing it's not. This is a mainstream science thread, and it will deal with mainstream science, not your own theory.

Ending your off-topic posts with a disclaimer won't change the fact you're off topic and against the rules.

 

Stick to your thread, owl.

 

The rest, please get back on the original topic. If you want to discuss the implications of owl's theory, you can do so in the Speculation thread.

I really, truly don't get it. This thread topic is on what "the present time" means, and that is what people have been discussing, including me.

I wonder how "presentism" is not relevant? (not "my" theory but for clarity on its lack of local boundaries.)

 

Does "Stick to your own thread" mean that I am not now allowed to participate in threads other than my own?

 

Anyway... in confused compliance, this IS my last post in this thread.

[DrRocket]

Doctor Rocket maybe I will call your bluff afterall.

 

You have admitted yourself that time description is a local event. It is also a local, real variable. Events only ever happen in the present moment and observations made in real time. Perhaps you would like to tell me why a universal present is ''obsurd.''

 

 

That is quite saimple, as the context is general relativity, and your claim is for a universal present.

 

Spacetime is a curved Lorentzian manifold. There is no global chart for that manifold. There is therefore no universal notion of either "time" or "space". Both are local, not universal, concepts.

 

The fact that time is a local real variable is completely irrelevant. We are talking about a Lorentzian manifold and all coordinates are therefore described as real quantities -- that comes with the definition of a smooth manifold.

 

That is what general relativity is all about.

 

Who said that presentism implies a universal present?

 

 

owl and Mystery111

 

Perhaps someone could take up the banner of discussing how "the present" (or "it's always now") isn't a tautology and can be quantified, in keeping with sound physics principles[/modnote]

 

As a local concept "the present" is essentially a definition, not really a tautology as there is no logical sentence. But "the time is now" is pretty much a tautology, so you did capture the flavor. The fact that our direct experience is with "now" is a triviality.

 

But the assertion thast was made was for a universal notion of "the present" which requires a universal notion of time. In general relativity there is no such thing as a universal time (or even universal space). Both time and space are local concepts. "Time here" and "time there" have no clear meaning.

 

Now I know that you work daily with synchronozed clocks. You can do that in special relativity. Special relativity deals with flat spacetime. General relativity is locally just special relativity, and that local approximation is very good indeed, so long as you deal with small gravitational effects and modest distances. But it fails on very large scales and in the presence of high spacetime curvature -- hence is not valid for the universe as a hole or in highly curved regions such as associated with black holes.

 

Note that "almost flat" or "flat on the largest scale" which may or may not describe the universe are clearly not true on small scales (else there would be no gravity", and hence are irrelevant to the specific issue that has been raised. .

Edited November 9, 2011 by DrRocket

[michel123456]

The fact that our direct experience is with "now" is a triviality.

 

No, it is comparable to the fact that up is up and down is down. It looks trivial until one asks himself why apples fall down.

In this case one has to ask himself why our direct experience is now.

[swansont]

I really, truly don't get it. This thread topic is on what "the present time" means, and that is what people have been discussing, including me.

I wonder how "presentism" is not relevant? (not "my" theory but for clarity on its lack of local boundaries.)

 

Does "Stick to your own thread" mean that I am not now allowed to participate in threads other than my own?

 

Anyway... in confused compliance, this IS my last post in this thread.

 

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Moderator Note

Because it was posted in physics, the thread topic is on what "the present time" means in a physics context. When you are posting off-topic or speculative material, yes, it means stick to your own threads on the topic — if you wish to discuss this in the context of the ontology, you have a thread for that. Do not steer this thread in that direction. If you wish to discuss the subject in a somehow physics-related way, then you are welcome to. But as soon as the discussion turns to anything that contradicts relativity or is based on philosophy, you are off-topic.

[DrRocket]

No, it is comparable to the fact that up is up and down is down. It looks trivial until one asks himself why apples fall down.

In this case one has to ask himself why our direct experience is now.

 

No it is comparable to the fact that up and down are measured relative to your present location, which is neither up nor down -- a trivial fact.

[Mystery111]

That is quite saimple, as the context is general relativity, and your claim is for a universal present.

 

Spacetime is a curved Lorentzian manifold. There is no global chart for that manifold. There is therefore no universal notion of either "time" or "space". Both are local, not universal, concepts.

 

The fact that time is a local real variable is completely irrelevant. We are talking about a Lorentzian manifold and all coordinates are therefore described as real quantities -- that comes with the definition of a smooth manifold.

 

That is what general relativity is all about.

 

 

 

 

 

 

What is ''Universal Present'' to you exactly? I have said an ''Eternal Present'' - I know what is meant by this, do you? You do realize that the past and future don't really exist simultaneously to the current present frame right?

 

''The fact that time is a local real variable is completely irrelevant. ''

 

Do as you say then.... it was you who mentioned time being local and does not apply to the universe as a global time; which by the way, global time results in singularities. Global Time does not manifest itself and maybe this is reflected in the Wheeler deWitt equation where the time derivative vanishes.

 

Oops, I better be careful not use too many buzzwords. It seems to confuse you

 

 

 

Note that "almost flat" or "flat on the largest scale" which may or may not describe the universe are clearly not true on small scales (else there would be no gravity", and hence are irrelevant to the specific issue that has been raised. .

 

 

I still don't understand why the flatness of the universe was brought up. Nor do I understand your objection to my statement that there is atleast 100,000th degree of an error for flatness in all directions, (making the universe almost flat). My statement is absolutely correct within the framework of Astrophysics, but I can't fathom why you even brought it up Rocket maybe you could elucidate.

[DrRocket]

What is ''Universal Present'' to you exactly? I have said an ''Eternal Present'' - I know what is meant by this, do you? You do realize that the past and future don't really exist simultaneously to the current present frame right?

 

''The fact that time is a local real variable is completely irrelevant. ''

 

Do as you say then.... it was you who mentioned time being local and does not apply to the universe as a global time; which by the way, global time results in singularities. Global Time does not manifest itself and maybe this is reflected in the Wheeler deWitt equation where the time derivative vanishes.

 

The issue is not whether we exist eternally in the present. That is a triviality. The issue lies with the assertion that there is a global notion of "present", hence time, valid throughout the universe. There is, in fact, no such notion.

 

Your emphasis was on the word real, which merely comes for free with a Lorentzian manifold. I had already, several times, pointed out that a time coordinate is purely local, an approximation taken from the tangent space to the spacetime manifold at av given point.

 

Global time does not result in singularities. Wherever did you get such a notion ? You can get a global notion of time from a homogeneous and isotropic spacetime. It is not really time, but it suffices for many purposes in cosmology. But the spacetime in which we live is neither homogeneous nor isotropic.

 

The Wheeler Dewitt equation has absolutely nothing to do with the issue at hand. Nor does quantum theory, as we lack a unification of quantum theory with general relativity. Relativistic quantum theories compatible only with special relativity are not relevant.

 

Oops, I better be careful not use too many buzzwords. It seems to confuse you

 

Nope.

 

I am not confused at all by your misleading use of buzz words, and misuse of the associated concepts.. But, unlike you, I understand those concepts.

 

 

 

 

I still don't understand why the flatness of the universe was brought up. Nor do I understand your objection to my statement that there is atleast 100,000th degree of an error for flatness in all directions, (making the universe almost flat). My statement is absolutely correct within the framework of Astrophysics, but I can't fathom why you even brought it up Rocket maybe you could elucidate.

 

You did not say the universe is almost flat.

 

You said

 

It's very close to being homogeneous; It is homogeneous to 100,000th of an error in each direction of spacetime we observe.

 

Which is a reflection of local isotropy, not homogeneity, and which has nothing whatever to do with curvature.

 

Almost flat is not flat. And the difference between "almost flat" and flat makes all the difference in global spacetime topology.

 

Moreover "almost flat in all directions" from a single point does not imply flatness either. Curvature does not work that way. Better read up on differential geometry. While you are at it you might try to learn the differences among homogeneity, isotropy and flatness.

[Mystery111]

The issue is not whether we exist eternally in the present. That is a triviality. The issue lies with the assertion that there is a global notion of "present", hence time, valid throughout the universe. There is, in fact, no such notion.

 

Your emphasis was on the word real, which merely comes for free with a Lorentzian manifold. I had already, several times, pointed out that a time coordinate is purely local, an approximation taken from the tangent space to the spacetime manifold at av given point.

 

Global time does not result in singularities. Wherever did you get such a notion ? You can get a global notion of time from a homogeneous and isotropic spacetime. It is not really time, but it suffices for many purposes in cosmology. But the spacetime in which we live is neither homogeneous nor isotropic.

 

The Wheeler Dewitt equation has absolutely nothing to do with the issue at hand. Nor does quantum theory, as we lack a unification of quantum theory with general relativity. Relativistic quantum theories compatible only with special relativity are not relevant.

 

 

 

Nope.

 

I am not confused at all by your misleading use of buzz words, and misuse of the associated concepts.. But, unlike you, I understand those concepts.

 

 

 

 

 

 

You did not say the universe is almost flat.

 

You said

 

 

 

Which is a reflection of local isotropy, not homogeneity, and which has nothing whatever to do with curvature.

 

Almost flat is not flat. And the difference between "almost flat" and flat makes all the difference in global spacetime topology.

 

Moreover "almost flat in all directions" from a single point does not imply flatness either. Curvature does not work that way. Better read up on differential geometry. While you are at it you might try to learn the differences among homogeneity, isotropy and flatness.

 

''I am not confused at all by your misleading use of buzz words, and misuse of the associated concepts.. But, unlike you, I understand those concepts''

 

Mmmm bitchy Rocket. Very bitchy.

 

I am sure I understand these concepts quite well thank you. I've had some of the best teachers.

 

''The issue is not whether we exist eternally in the present. That is a triviality. The issue lies with the assertion that there is a global notion of "present", hence time, valid throughout the universe. There is, in fact, no such notion.''

 

Then you better start keeping up to track with the actual conversation (doctor?) rocket. No one mentioned anything about a universal present.

 

''Your emphasis was on the word real, which merely comes for free with a Lorentzian manifold. I had already, several times, pointed out that a time coordinate is purely local, an approximation taken from the tangent space to the spacetime manifold at av given point.''

 

No, the word ''real'' is an emphasis on the nature of time Rocket. Measurements (which defines time) are always real and local.

 

''Global time does not result in singularities. ''

 

http://www.fqxi.org/...timecontest.pdf

 

''The Wheeler Dewitt equation has absolutely nothing to do with the issue at hand.

You accuse me of not knowing buzzwords when it is quite evident you don't even know the real arguement at hand based on this reply of yours. The Wheeler deWitt equation has everything to do with a global time, where time derivative vanishes - it was the core arguement for a timeless universe as an incompatibility of GR and quantum mechanics. Please understand these subjects before you frivolously throw them away.

 

I will provide you with one reading material, which highlights the Wheeler deWitt equation. If you will not read that, then study it yourself. It is called the ''Time Problem'' of quantum mechanics. You will find massive reading on the subject.

 

There is that one peice of reading material. Enjoy, holds everything need to be known at this point about the WDW equation.

 

http://www.fqxi.org/data/essay-contest-files/Markopoulou_SpaceDNE.pdf

Edited November 10, 2011 by Mystery111

[michel123456]

No it is comparable to the fact that up and down are measured relative to your present location, which is neither up nor down -- a trivial fact.

Are you an Academic?

[swansont]

''I am not confused at all by your misleading use of buzz words, and misuse of the associated concepts.. But, unlike you, I understand those concepts''

 

Mmmm bitchy Rocket. Very bitchy.

!

Moderator Note

When I wrote to stop it, I meant stop it. I didn't do that to exercise my fingers

 

Then you better start keeping up to track with the actual conversation (doctor?) rocket. No one mentioned anything about a universal present.

 

owl did

http://www.scienceforums.net/topic/60573-the-present-time/page__st__40__p__634447#entry634447

[Mystery111]

 

owl did

http://www.sciencefo...447#entry634447

 

Well as far we can tell, there is no such thing as a ''universal present''. Unless Owl meant it very loosely to describe that there is only the present time ever in existence. I call it an eternal present - a present time in the universe for each objects frame.

[swansont]

Well as far we can tell, there is no such thing as a ''universal present''. Unless Owl meant it very loosely to describe that there is only the present time ever in existence. I call it an eternal present - a present time in the universe for each objects frame.

 

That's not the same as it not being mentioned, though, now is it? Given owl's previous posts on the matter (in this thread, even), I that you would have to work a lot harder to support your interpretation (but not here since that would be OT)

[md65536]

owl uses his own made-up definitions for presentism, time, psychologist etc.

If you're discussing these topics according to his definitions, you should know that they have very limited correlation with reality.

Edited November 10, 2011 by md65536

[Mystery111]

 

 

owl did

http://www.sciencefo...447#entry634447

 

 

I also noticed doctor rocket said I had said this as well. Which is a lie. I never said anything of sort.

 

owl uses his own made-up definitions for presentism, time, psychologist etc.

If you're discussing these topics according to his definitions, you should know that they have very limited correlation with reality.

 

Fair do's.

 

Dammit swanson. I liked your post, but still waiting for an orgasm. :/

[36grit]

If we could imagine time as bubbles of expansion, and mass entities as modulations within the frequencies. We'd see "ribbons' and paricles in a continuum of relativity. Everything flowing in patterns of least resistance.

The present time becomes relative to the cross sections of relative expansion modes, within the continuum or spectrum of relativity.

Relative to our being, and childhood understanding the present time would become the time modulation state of frequency, as is according to the lattice frame work of atoms, that encompasses our personal awarness, and the state of knowledge and frame of awareness and mind, in the given instant of time.

[DrRocket]

I also noticed doctor rocket said I had said this as well. Which is a lie. I never said anything of sort.

 

Nope

 

 

Perhaps you would like to tell me why a universal present is ''obsurd.''

 

[36grit]

if the universe is part of a larger body of universes, then a present time cross section of relativity is possible. in my humble opinion.

The lattice frame work, that holds the universes in position within it's dynamic state, will posses an algorythmic modulation that defines a present to present anomily within the mass/momentum field.

 

in other words, if you were big enough, you could probably use the universe as the crystal in your watch.

ofcourse the universe wouldn't be "Uni" any more. Just another verse within a host of verses residing within the infinite field of relativity.

A present time requires a body of relativity. If you want to talk about a present time you need to define a field of presence (or virtual presence) before you define it's present state. In other words, are we discussing the present time of a person, a chemical, an atom, solar system, galaxie, so on and so on.

It seems to me that we should be able to catagorize relativity feilds by their ability (or energy) to bend, absorb, reflect and/or produce, light (or electromagnatism).