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TobiasTheViking
2009-Jan-01, 04:53 PM
Now, i realize we don't understand quantum gravity yet, so it may be hard to answer this question, but i still think it is doable.

Relativity says that as energy increases time goes slower, and i think it also says that the force of gravity increases with energy/mass.

So, I'm wondering, at the period between the big bang and 10^–43(the plank epoc), that would take plank time to pass from the reference frame of being inside the universe.

But, and i know this is impossible, if one could be "outside" the universe(or just in a pocket of space without all that energy), and was looking in at it... how long would it look for someone in that reference frame.

reference frame 1: all the energy of the big bang
reference frame 2: lets say 3k energy(as it is now)

rf1 would take 1 plank time
rf2 would take how long?

Is it even possible to calculate it?

And yes, i do realize the question as such makes little to no sense(can't be outside the universe, and if you are in it will take 1 plank time regardless)

Sincerely
Me :)

TobiasTheViking
2009-Jan-01, 08:08 PM
Too stupid a question?

tommac
2009-Jan-01, 08:23 PM
Too stupid a question?

possibly.

you cant look into the universe from the outside. If time and space dont exist then what does looking into even mean?

Are you trying to ask ... if there was as great/compact a mass as there was at the big bang how would 1 plank time at that location in space-time translate relative to our time?

Really I think there are parts of the universe that are less than 1 planck time after the big bang.
Wouldnt primordial black holes still be experiencing the earliest stages of the big bang?

Cheap Astronomy
2009-Jan-01, 09:37 PM
Relativity says that as energy increases time goes slower, and i think it also says that the force of gravity increases with energy/mass.

I'm not sure relativity says that time goes slower with increasing energy. To an external observer a clock in a fast moving object or in a gravity well goes slower. The force of gravity (http://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation) doesn't necessarily increase with energy either - it is normally expressed in terms of distance from a centre of mass.

Anyway it's not that your question is stupid, it's just not clear what your question is.

Maybe you are fishing for thinking about whether the rate of time (and/or the speed of light) has changed since the big bang. This is highly speculative thinking not based on any hard evidence - it tends to be used as a gambit in creationist psuedoscience to argue why the earth is only 6k years old.

Tensor
2009-Jan-01, 10:12 PM
The force of gravity (http://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation) doesn't necessarily increase with energy either - it is normally expressed in terms of distance from a centre of mass.

You're looking at Newtonian gravity. General Relativity uses Energy, not mass, to determine gravity. It comes in the GR equations through the Stress-Energy tensor. The mass is converted to energy by multiplying the mass by c2 and then taking the total pressure from the three orthogonal directions through a point. From that ( and a few constants), you get the curvature of space (which is gravity in GR) from the Ricci Tensor on the other side of the equations.

Cheap Astronomy
2009-Jan-01, 11:24 PM
Fair enough - I am just questioning the validity of the statement 'the force of gravity increases with energy/mass'.

For example, I'm thinking that the energy density at the centre of the sun is a lot more than at the surface, but the nett force of gravity there is zero. I have no idea how to express this in terms stress-energy tensors, but assume it remains true?

TobiasTheViking
2009-Jan-02, 12:21 AM
you cant look into the universe from the outside. If time and space dont exist then what does looking into even mean?
yeah, i know, and said that in my OP.

Are you trying to ask ... if there was as great/compact a mass as there was at the big bang how would 1 plank time at that location in space-time translate relative to our time?
Yes, basically.

Maybe you are fishing for thinking about whether the rate of time (and/or the speed of light) has changed since the big bang. This is highly speculative thinking not based on any hard evidence - it tends to be used as a gambit in creationist psuedoscience to argue why the earth is only 6k years old.
Yes, kinda.. but I'm not asking the hypothetical "what if rate of time has changed" or "what if the speed of light has changed".

I'm asking specifically "how has the rate of time changed due to the consequences of general relativity"?

And I'm not going to turn this into any ATM thing at all.. nor a religious 6k year old thing. I just like science :) i have no hypothesis, or any intention of making one.

----

So, i think my question is "has the rate of time changed since the big bang because relativity?"

I think the reason it became a bit mudied in my OP is because if there is any rate of time change, it won't be noticed as long as you are in the same reference frame as... well... the universe is in.

So i was trying to say that we have a fixed reference frame (us here on earth now), has the rate of time changed since the big bang because of relativity, compared to this reference frame(lets imagine we always have been in the reference frame we are in now, and it won't change with time).

It still sounds cryptic to me :(

Cheap Astronomy
2009-Jan-02, 01:00 AM
OK - understood.

From our point of reference there are all sorts of differences in the perceived (and measurable) rate of time in different locales.

E.g time approaches zero as you approach the event horizon of a black hole etc. However, if you are the one approaching the black hole, then time seems unchanged for you, it looks like the rest of the universe is speeding up (although you may be too busy dying to notice).

So, 'has the rate of time changed since the big bang because of relativity' - from a fixed frame of reference? Well, yes, with respect to changing localised conditions (like a black hole forming) in different points of reference. But in an absolute sense there is no reason to think the rate of time has changed since the big bang.

In any case, as Tommac noted, there is no reference point where you can measure an absolute rate of time - the whole idea of relativity is that there is no absolute frame of reference.

TobiasTheViking
2009-Jan-02, 01:20 AM
Yeah, i know that. And i know there is no absolute frame of reference. That is why i said the reference frame of the observer should be our current reference frame(and then ignore that it would change when we rewind back to the big bang)

But can we calculate how long the plank era of the big bang would last from our reference frame right now(and i also know that is impossible).. the plank era would be 1 plank time.. but, from our reference frame, how long would that take.. 10plank time? 100? maybe an entire second.

I realize that isn't really of great importance, but i'm interested.

spratleyj
2009-Jan-02, 01:49 AM
Now, i realize we don't understand quantum gravity yet, so it may be hard to answer this question, but i still think it is doable.

Relativity says that as energy increases time goes slower, and i think it also says that the force of gravity increases with energy/mass.

So, I'm wondering, at the period between the big bang and 10^–43(the plank epoc), that would take plank time to pass from the reference frame of being inside the universe.

But, and i know this is impossible, if one could be "outside" the universe(or just in a pocket of space without all that energy), and was looking in at it... how long would it look for someone in that reference frame.

reference frame 1: all the energy of the big bang
reference frame 2: lets say 3k energy(as it is now)

rf1 would take 1 plank time
rf2 would take how long?

Is it even possible to calculate it?

And yes, i do realize the question as such makes little to no sense(can't be outside the universe, and if you are in it will take 1 plank time regardless)

Sincerely
Me :)

I'm confused - are you asking if there was time dilation during the big bang?

TobiasTheViking
2009-Jan-02, 02:10 AM
yes, if there was time dilation compared to our current reference frame(even though that doesn't really make sense), and how long the plank era would last from our current perspective.

Durakken
2009-Jan-02, 02:18 AM
Tobias,

as to what you might see if you could perceive outside of the universe at the beginning of the universe...If you applied 3D shapes what you might see is a cone shape that is made of something like a pearl necklace.

As far as I know you wouldn't see it be formed. You would just see this cone getting ever bigger as the pearls get bigger and each on create two more. This process would continue at a constant rate as there is nothing that I know of that could be seen as a process of higher dimensions that are similar to gravity or anything like that that interupts this process, but then even if there were i don't think we'd detect it...so to the level that we know that is similar to what you would perceive if you looked at the universe from outside it... at least i think it is.

Though others will correct me if i be wrong...

Cheap Astronomy
2009-Jan-02, 02:31 AM
Yeah, i know that. And i know there is no absolute frame of reference. That is why i said the reference frame of the observer should be our current reference frame(and then ignore that it would change when we rewind back to the big bang)

But can we calculate how long the plank era of the big bang would last from our reference frame right now(and i also know that is impossible).. the plank era would be 1 plank time.. but, from our reference frame, how long would that take.. 10plank time? 100? maybe an entire second.

I realize that isn't really of great importance, but i'm interested.

Sure - I am interested too. I think the answer is that it would take 1 planck epoch (http://en.wikipedia.org/wiki/Planck_epoch).

There's a mixing of physical concepts here, since I understand a planck epoch to be a quantum physics term referring to a time period in which the uncertainty principle allows zero nett energy quantum fluctuations to occur. This concept just doesn't fit with classical relativity.

I'm not sure any of this can be effectively discussed in plain English, but I think you could say that from a relativity perspective, the clock starts after the big bang - the planck epoch is not a measurable/meaningful time period. So it's not a time period that would be compressed or dilated from any frame of reference (i.e. it's not a time period).

However, you can't use relativistic principles to debunk quantum physics principles or vice versa. We have to live with dualism until someone gets that theory of everything up and running.

speedfreek
2009-Jan-02, 02:35 AM
yes, if there was time dilation compared to our current reference frame(even though that doesn't really make sense), and how long the plank era would last from our current perspective.

Then yes, in the sense you seem to be meaning here, there is time-dilation compared to our current reference frame. A classic example of this is the time-dilation of Type 1a supernovae (SN1a).

If we see the duration of a SN1a at redshift z=2 as twice that of a SN1a at redshift z=1, due to the expansion of the universe, then from our current reference frame, events at z=2 take twice as long as the same event would take at z=1.

The CMBR is throught to have a redshift value of around z=1100, so the universe is now around 1100 times larger than it was when the CMBR was emitted. The wavelengths of light we receive from that emission have been stretched to 1100 times their original length (which is why they are now in the microwave spectrum) and so if there were an event to see there, we would see it time dilated to 1100 times its proper duration.

I wouldn't like to extrapolate that back all the way to the planck era though!

But I suspect this is not the kind of time-dilation you meant at the start of this thread as this is cosmological time-dilation rather than gravitational (are they the same?), and our current reference frame is not that of an observer "outside" the universe.

TobiasTheViking
2009-Jan-02, 03:05 AM
Tobias,

as to what you might see if you could perceive outside of the universe at the beginning of the universe...If you applied 3D shapes what you might see is a cone shape that is made of something like a pearl necklace.

But i'm really only interested in the time aspect, not the shape it would be from outside.

Sure - I am interested too. I think the answer is that it would take 1 planck epoch (http://en.wikipedia.org/wiki/Planck_epoch).
.
No, plank time is the smallest unit of time that makes any kind of sense, you can't have time smaller than that. so plank time is a measurable/meaningful time period. Anything smaller than that, though, isn't.

But the plank epoch takes 1 plank time(in the current BB model anyways), from the reference frame of being within the universe, in a reference frame that is so small, so dense, so filled with energy.

So i'm thinking, from a reference frame that is in the same movement as the universe(i know, doesn't make sense as such). A reference frame where the only difference compared to the reference frame of the plank epoch, is size, density, and energy(heat). And lets use earth right now as an example(or just the vacuum of space at the L2 point).
If we could, hypothetically, have that reference frame compared to the plank epoch, how long would the plank epoch take viewed from that reference frame. At the time of the BB it took 1 plank time. but viewed from a reference frame with less energy(background radiation of 3k), less mass(a few atoms per cubic meter), how long would it appear to take?

Then yes, in the sense you seem to be meaning here, there is time-dilation compared to our current reference frame. A classic example of this is the time-dilation of Type 1a supernovae (SN1a).

you are right, i don't mean time dilation from expansion, i mean time dilation from general relativity(as in, time passes slower near the event horizon of a black hole because of the gravitational attraction, or in a ship moving at .99c because of the speed).. I'm solely asking about that, not about time dilation.

---

If you think my questions are too irrelevant/stupid/inane, just tell me and i'll let it go :)

Cheap Astronomy
2009-Jan-02, 03:13 AM
The CMBR is throught to have a redshift value of around z=1100, so the universe is now around 1100 times larger than it was when the CMBR was emitted. The wavelengths of light we receive from that emission have been stretched to 1100 times their original length (which is why they are now in the microwave spectrum) and so if there were an event to see there, we would see it time dilated to 1100 times its proper duration.

.

I don't agree. If you stretch an area of 'empty space' by 1100 times - there is no reason to think time will be dilated within that space. Time will be dilated differently in local regions depending on mass distribution etc.

How about we forget the universe and redefine the question to consider an observable, but isolated, system with perfectly isotropic energy density and then expand the system (with an expectation that the energy density of the system decreases but remains perfectly isotropic).

Does this expansion lead to time dilation at a system level from the perspective of an external observer? I don't think so. I think there would just be localised relativistic changes (e.g. the middle of the system versus it's outer edges).

Durakken
2009-Jan-02, 03:24 AM

But i'm really only interested in the time aspect, not the shape it would be from outside.

That's just the thing in that view point the formation that would see is time taking place rather than being in time. The "time" it takes takes for it to go from point A to point B would be instant or at a constant rate as there are no known things that would slow the process.

TobiasTheViking
2009-Jan-02, 03:44 AM
That's just the thing in that view point the formation that would see is time taking place rather than being in time. The "time" it takes takes for it to go from point A to point B would be instant or at a constant rate as there are no known things that would slow the process.

blueshift
2009-Jan-02, 03:44 AM
First, when two events occur that are within 10^-33 cm. there is no way to distinguish which event came first. You divide that number by the speed of light and you come up with 10^-43 seconds. That is why scientists discourage any attempt to talk about "what happened before that time". It can't be measured.

Secondly, reference frames are not the same thing as reference points.In special relativity anyone who is walking or moving at all is not in the same reference frame as the earth is. You have to be sharing the same motion to be in the same reference frame. Two boxers are not in the same reference frame. They are in the same ring. In the Twin Paradox experiment the distant star that the traveling twin flies toward is in the same reference frame as earth.

Thirdly, on a universal scale special relativity breaks down and does not apply. The universe would have to be moving relative to something and if it was then that something would have to be a part of the universe. So for the universe time is not relative and the universe is a special reference frame.

Lastly, all of this has nothing to do with supersymmetry.

speedfreek
2009-Jan-02, 03:53 AM
I don't agree. If you stretch an area of 'empty space' by 1100 times - there is no reason to think time will be dilated within that space. Time will be dilated differently in local regions depending on mass distribution etc.

I think you might have misunderstood me, as I was referring to the effect of the expansion of the universe on our observations of supernovae, as shown in studies such as:

Time Dilation in Type Ia Supernova Spectra at High Redshift (http://arxiv.org/abs/0804.3595)

The higher the cosmological redshift of the event we are looking at, the more that event is time-dilated, relative to our current frame and this is due to the expansion of the universe or perhaps more accurately it is due to the difference in the scale of the background metric between the two frames of reference involved.

The upshot of this is that, for an event of a given duration (like an ideal type of supernovae that always burns for the same duration at a given distance), we will see that event elapse over a longer duration, the higher the cosmological redshift.

But this is really sidetracking from the original question.

TobiasTheViking
2009-Jan-02, 03:56 AM
I mentioned supersymmetry because the forces would be united at that point, hence i wondered about the effect of it.

but you first point. If a spaceship is moving past me at .99999c, then i will see time as slowed down in the ship. that means 1 second on the ship takes, lets say 10 secondm, from my reference frame.

Now lets say we do an experiment on the ship

As of 2006, the smallest unit of time that has been directly measured is on the attosecond (10^−18 s) time scale, or around 10^26 Planck times.

http://en.wikipedia.org/wiki/Planck_time

From my reference frame, wouldn't i see that expirement measuring the time scale to 10^27 planck times?(since i said above 1s for the ship would be 10s for me)?

your other points i totally agree with. But i don't have the language to say this in a more correct way than i have done.

Cheap Astronomy
2009-Jan-02, 04:25 AM
I will reiterate my 2c worths above.

1) There are limits to how much you can mix quantum and relativity concepts.

2) Fair enough - Planck time is quantifiable, but it is not reducable. From a relativity perspective, there is no sequence of events within the Planck epoch that can be sped up or slowed down from the perspective of an external observer. Relativity does not recognise it as a time interval that can be dilated.

3) I think the 'closed system with isotropic energy density' model proposed above is a much easier way to deal with your original question and I think the answer is no. Speedfreak's supernovae (real world) example leads to much the same conclusion.

Durakken
2009-Jan-02, 09:47 AM

For there to be general relativity there has to be light and or gravity...and thus time.

If we're outside of the universe there is no light probably. There may be some other thing that says nothing can move faster than this. And that depends on how "time" works in upper dimensions. To that perspective is it the 7th and 8th dimension or is it simply the 6th and 7th or is there no time at all?

Your question is somewhat like asking a computer how long a second is within a program that a second is broken up into 30 frames / second.

If you have a processor that is 2GHz...a second to it is 2,000,000,000 iterations. But if the program is complex then there are other things that keep that from being accurate. Then the program itself says you will only draw things every time 1/30 of those iterations pass or every 66,666,667 iterations.

The program is our universe. It says we have 30 frames in a second. If we switch the processor to a 3GHz processor our program still says we have 30 frames in a second, but the new processor says there are now 3,000,000,000 iterations in a second and every 1/30 there are now 100,000,000 process that happen in it.

Of course if there is no time in the upper dimensions then it becomes a matter of a measurement than a matter a speed of any sort... Everything just is. The universe has already expanded to it's maximum state and beyond. That cone is so immense even though there is no time you could still never reach to the end point of it.

And when you ask how long is a second instead of someone trying to count out so as to let time pass they might just go up to that cone of pearls, pull out a couple billion and stretch them out saying this is how long a second is.

GR only effects those inside the universe who have to play by the rules of time of the universe, not those who are outside the universe with their own rules. And the universe itself doesn't follow the rules of what inside of it but rather since it is an object of at least 8 dimensions, if we say it experiences time, it has it's own concept of time that those within it wouldn't quite understand or be effected noticeably by.