Timeless GR

[paddoboy]

I say my ''eyes'' because I feel this is the right way. I am almost certain time is not fundamental, so has a number of important physicists including Dirac.
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I'm no psychiatrist but in reality you must be extremely uncertain about the position you hold, considering the aggressive tactics you see the need to display, in your efforts to bulldoze your message across to all and sundry.
The same tactics are used by other alternative theorists here of late.

 

[Grumpy]

BlackHoley

It's not a question of whether time is applicable to GR because the facts are it doesn't have a global time parameter.

Ah, here's your dodge. It is true that the Universe has no global time. It is also true that time exists for every frame and it's all Relative time as described by GR. Farsight tried the same dodge, saying that because coordinate speed changes that lightspeed through spacetime(c) changes, and it doesn't. Time is part of spacetime(as described by GR), it exists, but each frame travels through it at it's own Relative pace. There is no global(we call it absolute)time. But time exists nonetheless.

Grumpy

 

[arfa brane]

The square root of -1 exists, but is it physical? Is it part of the structure of spacetime?

If it isn't, then why can we use $$ t = i\tau $$ to get a useful result? Would this work with spatial dimensions, and why would or wouldn't it?

 

[paddoboy]

BlackHoley



Ah, here's your dodge. It is true that the Universe has no global time. It is also true that time exists for every frame and it's all Relative time as described by GR. Farsight tried the same dodge, saying that because coordinate speed changes that lightspeed through spacetime(c) changes, and it doesn't. Time is part of spacetime(as described by GR), it exists, but each frame travels through it at it's own Relative pace. There is no global(we call it absolute)time. But time exists nonetheless.

Grumpy

Bingo!!!! and Bingo again!!!
And so far in this post, I think that is the first time he has mentioned "global time" .....Like I said, the thread was started just to get a raise out of people, the same smart arse methodology attempted by Farsight and undefined.
Birds of a feather and all that.........

 

[brucep]

BlackHoley



Ah, here's your dodge. It is true that the Universe has no global time. It is also true that time exists for every frame and it's all Relative time as described by GR. Farsight tried the same dodge, saying that because coordinate speed changes that lightspeed through spacetime(c) changes, and it doesn't. Time is part of spacetime(as described by GR), it exists, but each frame travels through it at it's own Relative pace. There is no global(we call it absolute)time. But time exists nonetheless.

Grumpy

The FLRW time coordinate is a global comoving proper frame time coordinate. The tick ratio with the clock at boundary is 1 as the universe evolves cosmologically. It's modeled that way for obvious reason. Then we can predict how old the universe is as measured by a clock in the bkkpr frame at boundary. We get to determine how we model the rate of change. Which metering stick we use. I think we called the Newton metering stick 'universal time'. Which predicts all clocks tick at the same rate regardless of relative velocity and position in the gravitational field. Logical choice but eventually shown to be inadequate for describing all natural phenomena.

 

[brucep]

The square root of -1 exists, but is it physical? Is it part of the structure of spacetime?

If it isn't, then why can we use $$ t = i\tau $$ to get a useful result? Would this work with spatial dimensions, and why would or wouldn't it?

A meaningful reason for choosing a coordinate system, and a method for metering the measurements made with respect to the coordinate system, is whether it will describe natural phenomena in a useful scientific way. Hawking had a cosmological model, he called the 'No Boundary Proposal', which metered the evolution of the cosmology with imaginary numbers. It worked fine but the cosmology was eventually ruled out based on falsified predictions for the CMBR power spectrum. Lots of cosmological models were ruled out by the empirical measurements made in the great cosmological experiments.

 

[BlackHoley]

I'm no psychiatrist but in reality you must be extremely uncertain about the position you hold, considering the aggressive tactics you see the need to display, in your efforts to bulldoze your message across to all and sundry.
The same tactics are used by other alternative theorists here of late.

You sound a little delicate... paddo. My attacks have hardly been aggressive... More astounded at times by the moronic comments... mainly due to lack of physics knowledge.

That's not harsh dear, it's the truth.

 

[BlackHoley]

The square root of -1 exists, but is it physical? Is it part of the structure of spacetime?

As I understand physics, there is no indication $$t$$ even exists externally. It's not an observable like $$x$$. The imaginary coefficient makes it look mysterious, but trust me, the imaginary number is even more real that the time variable!

If it isn't, then why can we use $$ t = i\tau $$ to get a useful result? Would this work with spatial dimensions, and why would or wouldn't it?

Because time is still a useful tool... and don't let imaginary numbers confuse you either, they have applications all over physics and a lot of physics wouldn't work without their application. The imaginary number is indeed... mysterious but it doesn't weigh any important revelations about time in general.

 

[BlackHoley]

Arfa.... just like a Wick Rotation... just a nice mathematical procedure, nothing more.

 

[BlackHoley]

Because time is still a useful tool... and don't let imaginary numbers confuse you either, they have applications all over physics and a lot of physics wouldn't work without their application. The imaginary number is indeed... mysterious but it doesn't weigh any important revelations about time in general.

Sorry didn't fully answer your question...


... yes you can make space an imaginary dimension, that's how you get back back the definition of Minkowski spacetime! You have four dimensions of space and one of them is imaginary.

 

[BlackHoley]

BlackHoley



Ah, here's your dodge. It is true that the Universe has no global time. It is also true that time exists for every frame and it's all Relative time as described by GR....

No, if you are talking about frame of references, then there is a local time experienced by moving matter as in special relativity.

I am several steps ahead such questions. I know how to model local time in special relativity, that's easy and it's the only time that appears to be existent. What is local time? Matter have natural clocks... to us, it's a subjective experience of time. Local time, however, doesn't have to imply time needs to exist for the universe.

 

[BlackHoley]

And it's a bit strange you say it was a dodge... I have never dodged this. In fact I have said quite a few times only local time appears real in the sense, we can actually measure clocks in matter (frames of reference) relative to other clocks.


edit (this sense, measure isn't meant to mean, observable)

 

[paddoboy]

Despite the bullshit you see the need to bulldoze through, most people, scientists and laymen alike, still see time as part and parcel of space, the Universe and GR that describes it.
That is logical common sense and is supported by the reputable links I have given.

At best, your opinion is just a matter of interpretation, and at worst just plain wrong.

 

[BlackHoley]

Despite the bullshit you see the need to bulldoze through, most people...

I'm sure Grumpy just did what most people can do... search for what I am saying for themselves. I am sure half of your ignorance is that you never read any of the links provided. If you did, you'd have a far superior knowledge of time.

 

[Russ_Watters]

And it's a bit strange you say it was a dodge... I have never dodged this. In fact I have said quite a few times only local time appears real in the sense, we can actually measure clocks in matter (frames of reference) relative to other clocks.


edit (this sense, measure isn't meant to mean, observable)

Seems to contradict where you said flatly and repeatedly that there is no time in GR.

 

[BlackHoley]

Seems to contradict where you said flatly and repeatedly that there is no time in GR.

If you ask me if time exists in the universe, I have to be honest and say there is no cosmological $$t$$.

If we are talking about moving observers (or by measuring the electron clock due to Zitter motion), there is a successful model of time.

Now, Hawking reminds us, there must be aspects of the universe which are quantum mechanical, such as the field of quantum cosmology. Quantum-mechanically speaking, time disappears from GR. When you quantize Einstein's equations, you get back the Wheeler de Witt equation, which tells us that whatever time is, it is not fundamental.

So sure, talk about time all you want in the context of moving observers or measuring an electron clock due to zitter motion, it makes no difference because the fundamental theory of gravity is essentially timeless.

So I define two concepts:

Induced time to explain the local phenomenon which can be modeled very successfully using the laws of relativity and fundamental time which in the context of GR, has none.

 

[wellwisher]

The universe has a global time one can infer from the speed light; same in all references. The frequency of the light (like the ticking of a clock) is not global, but changes with reference. There are two effects coming from photons, one is global and one is not.

Here is an interesting thought experiment. Say a team of humans were launched into space on a space ship moving near the speed of light. There are SR effects like in the twin experiment with their time slowing relative to the earth. These humans have lived in this frame for generations and finally the young adults decide to make this their zero state, instead of use the earth. They have never seen the earth, like their grandparents and decide to modernize the frame. It is all relative, correct?

Generations later, their grandchildren return to the earth and this newest generation of scientists, who only know the space ship as the zero reference of their universe, apply SR to the earth reference. They first use a positive relative velocity and then a negative velocity (squared), but the results come out the same and say the earth has the time dilation. However, when they do physical experiments (family tree count) the specimens (twins from many generation) show the reverse is true and they have the time dilation. How do they explain this, without a global reference?

 

[BlackHoley]

...that there is no time in GR.

And of course, there isn't any clock to the universe. GR doesn't use a time parameter to describe cosmological evolution.

Local experience of time is certain between observers in the context of SR but it cannot be extended to GR in this way, so there must be reasons (some given above) that time is an emergent phenomenon.

 

[BlackHoley]

The universe has a global time one can infer from the speed light; same in all references. The frequency of the light (like the ticking of a clock) is not global, but changes with reference. There are two effects coming from photons, one is global and one is not.

No no no no... you can't define clocks using light in relativity, they follow null geodesics.

 

[BlackHoley]

No no no no... you can't define clocks using light in relativity, they follow null geodesics.

Let me refine the problem for you, the universe didn't have any matter fields to define time in relativity. Consider what I said in another thread, you can gauge all matter using a meld of Einstein and Planck's equations to find there is a frequency associated to matter. This is how relativity defines a clock or by some moving observer (like a human measuring light signals from another inertial source).

Light in itself however, cannot act as a clock for the universe. The only time, time itself appears in relativity in the evolution of the universe, is when electroweak symmetry breaking occurred and matter appears. The universe has already grown quite large by this ''instant'', with only radiation fields in it. Again, radiation fields are in fact static, no time passes for them and so the early universe having a cosmological time is even inconsistent in this sense as well with SR.