# Is There A Universal Now?

(Biff transmits at 12:00)
Lets say Biff's signal takes 3 min transit time.
(So you receive the message at 12:03)
You don't know the time on Venus at 12:00.
(You know it at 12:03)
(The stuff in red was added by mlf for clarification.)

That's correct. The "array of clocks" method will always tell the PIO what the distant person's (DP's) age tau1 was at some previous time T1 in the PIO's life, not at his current age. When the PIO gets the HF's message, the PIO is age T2 > T1. But that nevertheless DOES accomplish the job of telling the PIO how old the DP was when the PIO was T1 ... he doesn't know the correct answer for a while, but he DOES eventually know what it was.

But the PIO doesn't have to wait for that (correct) information: he can determine the answer IMMEDIATELY by just using the time dilation equation (TDE) for an inertial observer. The value of the array of clocks method is that it INSURES that that answer is completely real and MEANINGFUL to the PIO, because that answer can't be wrong unless the PIO's and the HF's clocks (and their ages) aren't actually synchronized. But those clocks were synchronized using only the assumption that the speed of light is 186,000 miles per second in that PIO's inertial frame. So if those clocks aren't synchronized, then the speed of light isn't 186,000 miles per second. And if that were the case, special relativity itself would be wrong.

The answer is a "yes", the universe in toto has a single NOW at all times.

If it does, then special relativity is incorrect. I'm confident that special relativity is correct.

Line 1 is a contradiction of terms (past and present tense).

Please don't go all pedantic on me

NOW is in existence - hope you are in agreement there

PAST is not in EXISTENCE (EXISTENCE being the operative word)

For you, the past is events you are aware o

True but those events ARE MO LONGER IN EXISTENCE

The most distant stars appear as the youngest.

I would contend the totality of the Universe was born at BIG BANG. The FORM of Universe began to change at the same instance

The most distant stars may APPEAR as the youngest but that is the effect of the INFORMATION about them being delayed in its delivery to you due to the distance said information has to travel

Taking said delay into account brings said distant stars equal to your NOW moment and the only moment in existence

The Universe from such a perspective has no age

Doing, what I sometimes ask others not to indulge in, the age of the Universe could be considered as a collectively shared past

Write4U, I will be using the image you posted, assuming that since you posted it, it makes sense to you.

Let's call the system in which the drawn axes are stationary system K. The "now" of system K can be represented by an orthogonal plane (shown in orange) that intersects the time axis at one place, the time of "now" throughout that system, as follows:

Now let's consider a system in which the drawn axes are moving at some constant velocity, and call that system system K' (K prime). The "now" of system K' can be represented by an inclined plane (shown in red this time) that intersects the time axis at the same place, as follows:

The events which system K considers to be simultaneous (now) are wherever the orange plane intersects the worldlines, worldsheets, or world volumes. Likewise, the events which system K' (K prime) considers to be simultaneous (now) are wherever the red plane intersects the worldlines, worldsheets, or world volumes.

Notice that the same 3-dimensional diagram can be "sliced" different ways by inclining the plane of "now" at different angles. There are an infinite number of hypothetical systems in which the axes are moving at an infinite number of different constant velocities, and each has its own "now" particularly for distant events. That is called "relativity of simultaneity" is special relativity, and it changes the Newtonian concept of what "now" means considerably.

If it does, then special relativity is incorrect. I'm confident that special relativity is correct.
Special Relativity only applies to an observer. Without an observer the Universe itself has a chronological continuity of NOWs, each Now consisting of a 2d plane (brane).

Notice that the same 3-dimensional diagram can be "sliced" different ways by inclining the plane of "now" at different angles.
Can it? Who says?
I notice you qualified an infinite number of "hypothetical" systems. But there is only one NOW for each system, no?

I don't have to introduce an orange "what if". I see the blue 2D brane that is chronologically stacking for each instant of its existence (NOW). The top of the world volume is just another 2D brane of NOWs.

Each blue 2D brane is a set of NOWS for ALL particles, strings, and pattern contained in that 2D plane.. You cannot say that part of the brane's existence increases at a faster rate than its constituent parts.

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Special Relativity only applies to an observer. Without an observer the Universe itself has a chronological continuity of NOWs, each Now consisting of a 2d plane (brane).

Special Relativity (SR) does not rely on any observers. The two systems I described, K and K', do not have to have any observers in them. They only have to have space and time, which are represented by the axes in your diagram.

It is a common misconception that SR describes some types of optical effects which observers see when they are moving at a very fast speed relative to something else. That is not what SR is all about. For example, the well known "length contraction" of SR has nothing to do with an observer seeing an object's length as shorter. The object truly is shorter in length when the locations of both ends of the object are measured simultaneously (there is that word again) in different reference frames, such as system K and system K'. It is the result of relativity of simultaneity being a real thing.

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Yes but a brane K does not have K' as a constitutional part. K' Is a brane in and of itself.
I am not talking about 3D systems. I am talking about 2D branes.

Besides, systems are observers in their own right. No anthropomorphization is necessary.

Each 2D brane must consist of the same NOWs relative to each particle in that brane, else it would not be a 2D object, no?

Moreover what is 13.7 billion years about if not all of the Universe is 13.7 billion years old since its beginning.

How old is the universe and how do we know?

We do not know the exact age of the universe, but we believe that it is around 13 billion years - give or take a few billion. Astronomers estimate the age of the universe in two ways: (a) by looking for the oldest stars; and (b) by measuring the rate of expansion of the universe and extrapolating back to the Big Bang.
You Can't Be Older Than Your Mother
If we compare the various age determinations, there is a potential problem. If the astronomers who estimate that 1/H0 is as small as 10 billion years are correct, then the age of the universe would be less than the age of the oldest stars. This contradiction implies that either the Big Bang theory is incorrect or that we need to modify the theory of General Relativity or that we need to change our beliefs about stellar evolution. Most astronomers believe that this crisis will pass as soon as our measurements improve. Although the numbers are still very uncertain, the different data sets are starting to converge at an age for the universe of about 12 to 13 billion years.
UPDATE!
Measurements made by NASA's WMAP spacecraft have shown that the universe is 13.7 billion years old, plus or minus about 130,000 years. They were able to do this by making detailed observations of the fluctuations in the cosmic microwave background and using that information in Einstein's Theory of General Relativity to 'run the clock backwards to time equal zero'
https://starchild.gsfc.nasa.gov/docs/StarChild/questions/question28.html

Personally, I like this model;

The new finding suggests that the universe has slowed down and speeded up, not just once, but 7 times in the last 13.8 billion years, on average emulating dark matter in the process.
The ringing has been decaying and is now very small – much like striking a crystal glass and hearing it ring down.
https://earthsky.org/space/is-our-universe-ringing-like-a-crystal-glass/

Note: 7 oscillations have been depicted in the model.

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Can you please also exactly WHAT it is you are measuring
We measure the as constant as possible repetitive MOTION of something to get a duration as a base duration for a time system, maybe its virtual time system.

What are a couple of properties of TIME
MOTION is the closest physical thing I can think of...

Kinetic energy / Motion causes physical change

Write4U,

What I am talking about, (and what Mike Fontenot is talking about as well), is not related to the expansion of the universe. If what you are talking about is, then we are not all talking about the same things.

Each 2D brane must consist of the same NOWs, else it would not be a 2D object, no?

Did you look at your own space time diagram? The brane has 2 spacial dimensions, but there is also a time dimension. So the brane is represented through time as a world volume.

If you are stationary with respect to the brane, then according to you all parts of the brane are simultaneous as per the ORANGE plane that I added to the diagram. Let's say that there are 2 events, one at the left end of the brane, and another at the right end of the brane, and let those events be simultaneous according to you. So they can be located where the orange plane intersects the world volume, and they are simultaneous according to you.

If I am moving with respect to you along the left-right axis of the brane, then all parts of the brane are simultaneous as per the RED plane that I added to the diagram. For those same 2 events, one at the left end of the brane, and the other at the right end of the brane, those events are not simultaneous according to me, because they cannot both be located where the red plane intersects the world volume, not even if I move the red plane to a different time, because the red plane is still inclined on an angle to the orange plane.

That is one way to understand length contraction in SR. The trailing end of the moving object is relatively ahead in time, and the leading edge of the moving object is relatively behind in time, so the object takes up less length when it is relatively moving, compared to when it is relatively stationary and both ends are at the same time.

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What I am talking about, (and what Mike Fontenot is talking about as well), is not related to the expansion of the universe. If what you are talking about is, then we are not all talking about the same things.
I am not talking about anything but duration of existence of the Universe from the BB to NOW,
I keep it simple . Does the Universe have a singular timeline associated with its very existence from BB to NOW? If not, what part of the Universe that does not lie in the past is not experiencing NOW?

I am not talking about parts of the Universe. I am talking about a very simple chronology of the wholeness from the beginning of time to the present NOW (13.7 B)

Humans are uniquely unqualified to judge NOW altogether.
Any observation we make is already in the past!

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We measure the as constant as possible repetitive MOTION of something to get a duration as a base duration for a time system, maybe its virtual time system.

As in

One second is the time that elapses during 9,192,631,770 (or 9.192631770 x 109 in decimal form) cycles of the radiation produced by the transition between two levels of the cesium-133 atom.

https://www.techtarget.com/whatis/definition/second-s-or-sec?amp=1

MOTION is the closest physical thing I can think of...

Kinetic energy / Motion causes physical change

Don't think you can count motion as being physical. If you wish to count motion as being physical I will ask you the same question I asked about TIME

Please name some properties of motion

So the brane is represented through time as a world volume.
No it isn't. The brane is 2 dimensional and is only a single instant in time. When you stack 13.7 billion years of 2 D branes you create a 3D world-volume , but each brane is a single instant in time throughout the entire 2 D surface plane.
If you stack single particles you get a 1 dimensional worldline. If you stack 1 dimensional strings you get a 2D worldsheet.

With your description, I get visions of a patchwork quilt Universe...

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Special Relativity only applies to an observer. Without an observer the Universe itself has a chronological continuity of NOWs, each Now consisting of a 2d plane (brane).

Besides, systems are observers in their own right. No anthropomorphization is necessary.

Does the universe not count as a system?

Not that I agree with you. SR does not rely on an observer.

I hope your self contradiction is apparent...

Does the universe not count as a system?

Not that I agree with you. SR does not rely on an observer.

I hope your self contradiction is apparent...
There is no contradiction.

The Universe is a system, but the wholeness of the Universe is a singular system and only relative to itself.
It is its own observer and that is always @ NOW.

btw. I am not the one who introduced relativism. Quite the opposite. I am speaking of a straight linear chronology of existence. A singular wholeness cannot be of a different age than it's own chronology of NOWs.

That would require an observer from a different POV. And that model is not necessary to answer the OP question.
All other models are interesting, to be sure, but IMO, not relevant to the OP.

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No it isn't. The brane is 2 dimensional and is only a single instant in time. When you stack 13.7 billion years of 2 D branes you create a 3D world-volume , but each brane is a single instant in time throughout the entire 2 D surface plane.
If you stack single particles you get a 1 dimensional worldline. If you stack 1 dimensional strings you get a 2D worldsheet.

Let me try to explain this to you one more time. Let's say you put a clock on the left end of the brane and another clock on the right end of the brane. You synchronise those clocks using Einstein's synchronisation method, so that they display the same time as one another in the reference frame where the brane is stationary. In that frame, the simultaneity plane is the ORANGE plane that I drew on your diagram. Now, in the reference frame where the brane is moving at constant speed, the simultaneity plane is the RED plane that I drew, and those two clocks are not displaying the same time as one another simultaneously. That is because simultaneity is relative to each frame of reference. Get it yet?

It is the same brane, but there are an infinite number of possible reference frames to chose from. Depending on the reference frame you choose, the two clocks can be perfectly synchronised, or drastically out of synch, or anything in between. So there is no universal now that everyone can agree upon.

It has nothing to do with quilts.

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Here is a diagram showing the clock synch method in the reference frame of the brane:
Code:
Clock 1------central light source------Clock 2
Clock 1-----<central light source>-----Clock 2
Clock 1----<-central light source->----Clock 2
Clock 1---<--central light source-->---Clock 2
Clock 1--<---central light source--->--Clock 2
Clock 1-<----central light source---->-Clock 2
Clock 1<-----central light source----->Clock 2
0:00000------central light source------0:00000
0:00001------central light source------0:00001
0:00002------central light source------0:00002
0:00003------central light source------0:00003
The clocks are syncronised in this reference frame.

And here is a diagram showing the SAME clock synch method for the SAME clocks, the only difference is that this happens to be a reference frame where the brane is moving at constant speed:
Code:
Clock 1------central light source------Clock 2
Clock 1----<-central light source>-----Clock 2
Clock 1--<---central light source->----Clock 2
Clock 1<-----central light source-->---Clock 2
0:00000------central light source--->--Clock 2
0:00001------central light source---->-Clock 2
0:00002------central light source----->Clock 2
0:00003------central light source------0:00000
0:00004------central light source------0:00001
0:00005------central light source------0:00002
0:00006------central light source------0:00003
The clocks are NOT syncronised in this reference frame.

These are not drawn to any specific scale, they are just to get you thinking about what is really going on. Remember, the speed of light is constant regardless of the speed of the light source. This is part of Einstein's great insight that lead to SR. And part of SR is the idea that simultaneity is relative to the reference frame you choose.

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Get it yet
Yes, I get it. You cannot divorce yourself from relativity between two observers.

I am not talking about Two observers or Two clocks or Two horse-and-buggies.

I am talking about ONE clock that keeps track of the age of the universe in toto, not how that may appear to a second or a thousand other clocks placed in positions relative to the one primary clock that records the chronology of the Universe's existential NOWs.

One clock for the entire universe, the prime Universal clock, the one that reads 13.7 billion years, get it?

All other individual measurements are secondary to the primary existential chronological measurement.

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Here is a diagram showing the clock synch method in the reference frame of the brane:
Code:
Clock 1------central light source------Clock 2
Clock 1-----<central light source>-----Clock 2
Clock 1----<-central light source->----Clock 2
Clock 1---<--central light source-->---Clock 2
Clock 1--<---central light source--->--Clock 2
Clock 1-<----central light source---->-Clock 2
Clock 1<-----central light source----->Clock 2
0:00000------central light source------0:00000
0:00001------central light source------0:00001
0:00002------central light source------0:00002
0:00003------central light source------0:00003
The clocks are syncronised in this reference frame.

And here is a diagram showing the SAME clock synch method for the SAME clocks, the only difference is that this happens to be a reference frame where the brane is moving at constant speed:
Code:
Clock 1------central light source------Clock 2
Clock 1----<-central light source>-----Clock 2
Clock 1--<---central light source->----Clock 2
Clock 1<-----central light source-->---Clock 2
0:00000------central light source--->--Clock 2
0:00001------central light source---->-Clock 2
0:00002------central light source----->Clock 2
0:00003------central light source------0:00000
0:00004------central light source------0:00001
0:00005------central light source------0:00002
0:00006------central light source------0:00003
The clocks are NOT syncronised in this reference frame.

These are not drawn to any specific scale, they are just to get you thinking about what is really going on. Remember, the speed of light is constant regardless of the speed of the light source. This is part of Einstein's great insight that lead to SR. And part of SR is the idea that simultaneity is relative to the reference frame you choose.

Oh my, you say this and then proceed to present a model (pattern) of a quilt.

The Essential Relationship between Mass and Energy
In Newtonian mechanics, the mass, time, length and energy are independent respectively; but in the special relativity, these four quantities all have something to do with speed, and mass and energy can convert into each other, which makes the physics academia in a great mess.
Therefore, people should do everything from the angle of philosophy, discuss the original relationship between mass and energy and clean the false influence of the special relativity.

First, there is rarely any reason for using a scenario with more than one spatial dimension. Stick to one spatial dimension.

When you do that, you get the well-known Minkowski diagram. In the simplest case of all, the horizontal axis would correspond to the worldline of the (unaccelerated) "home" twin ... i.e., it would be her time axis, along which she progresses as she gets older. Label that axis "T". The vertical axis would give (according to her) the distance from her to various objects that might be of interest. Label that axis "X". Most people reverse those axes, with "T" vertical and "X" horizontal, but I prefer showing the independent variable horizontally, just like we ordinarily do in Newtonian physics ... why make special relativity look different where it doesn't have to be.

Then, take the simplest case where there is an unaccelerated "traveling" twin (he), who passes the home twin (she) at the (X=0, T=0) point with a velocity of "v" relative to her, and maintains that velocity forever. In that case, the worldline of the traveler on the diagram would be a straight line rising forever to the right, with slope equal to the tangent of the velocity "v". For example, for v = 0.57735c, the angle is 30 degrees (which makes it easy to draw).

Now, one of the most fundamental results in all of special relativity is that if two inertial observers are moving a relative speed of v, they EACH will conclude that the other is ageing SLOWER than they are, by the factor gamma, where

gamma = 1 / (sqrt[1 - v^2]).

For v = 0.57735c, gamma = 1.2247.

The point is, in special relativity, the twins moving relative to each other WILL NOT AGREE about their current ages ... i.e., they disagree about "NOW-at-a-distance". If your results disagree with that, then you are NOT doing special relativity.