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Author Topic:   Age of the Universe
Percy
Member
Posts: 22393
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 16 of 103 (62112)
10-22-2003 10:11 AM
Reply to: Message 13 by sidelined
10-21-2003 6:24 PM


sidelined writes:
This is the source of confusion. In this thoght experiment one traces a bit less time between itself and another location-event in space-time not the big bang.
This still doesn't sound right to me. We have two synchronized atomic clocks on the ground. They both say the big bang was x seconds ago. One goes up in an aircraft and returns and it says that y seconds have gone by during the trip, and that therefore the big bang was x+y seconds ago. The one that remained on the ground says that z seconds have gone by during the trip, y<>z, and that therefore the big bang was x+z seconds ago.
Let us remember that at the location-event that signifies our universes' beginning everything you can find within the universe today was all there then.
The entire universe once existed in a single reference frame with a single time frame, but then it expanded into many relativistically moving reference frames. The rate of the passage of time varies between reference frames as a function of their relative motion. Relativity tells us that there is no absolute reference frame, for either location or time, and that there can be no single correct answer for the age of the universe.
--Percy

This message is a reply to:
 Message 13 by sidelined, posted 10-21-2003 6:24 PM sidelined has replied

Replies to this message:
 Message 18 by sidelined, posted 10-22-2003 11:08 AM Percy has replied
 Message 27 by zephyr, posted 10-22-2003 5:08 PM Percy has not replied

  
Percy
Member
Posts: 22393
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 17 of 103 (62118)
10-22-2003 11:00 AM
Reply to: Message 14 by JustinC
10-21-2003 7:15 PM


JustinCy writes:
quote:
JustinCy writes:
So did time happen x bya? Or does the t-dimension streth back x by?
Yes.
Which question are you saying yes to? Or was that a joke?
It appears to be the same question stated two different ways. Time began x bya, so naturally the time dimension stretches back x by.
Isn't every place in the universe equidistant to the BB in all axes? So it wouldn't necessarily matter exactly where you were, right?
I believe relativity says no, even in the same reference frame.
Many atomic clocks use the vibrations of a cesium atom to measure the passage of time. Take two hypothetical cesium atoms that formed at the same time as the big bang (impossible, but we're being hypothetical) and say that they're now resting on your desk, each in a device that maintains a count of the number of vibrations. You don't know how many vibrations they've had since the big bang, but we somehow know that each cesium atom has experienced the exact same number of vibrations since the big bang, and that this number of vibrations is a measure of the age of the universe. Now you send one of the cesium atoms up in an aircraft along with the vibration counting device, and when it comes back you find that the number of vibrations it experienced is less than the one that remained on the ground. Which cesium atom's vibration count is the correct one for the age of the universe?
--Percy

This message is a reply to:
 Message 14 by JustinC, posted 10-21-2003 7:15 PM JustinC has replied

Replies to this message:
 Message 45 by JustinC, posted 10-25-2003 6:21 PM Percy has replied

  
sidelined
Member (Idle past 5908 days)
Posts: 3435
From: Edmonton Alberta Canada
Joined: 08-30-2003


Message 18 of 103 (62119)
10-22-2003 11:08 AM
Reply to: Message 16 by Percy
10-22-2003 10:11 AM


Ok. When the plane returns it will be back in its own reference frame.the plane will have recorded the difference that exists between the ground A and the location-event above arth at B.
When it is back in its own reference frame it will, as a result of having travelled to B, be a very tiny fraction of a second younger than the the plane that remained on the ground.
The best illustration is to imagine at this time in the universes history all the points in space are on the surface of an expanding balloon. In the center of the ballon is the BB origin.As time goes on all points on the balloon remain an equal distance away from the center.
There is no absolute reference frame since each point in space is measuring from its reference frame.To go to another reference frame requires that we go to point B and back again while the universe continues its expansion.When we return our reference frame is in a new space-time location from when we left.This is because of a limited speed at which we can travel.MAXIMUM 300,000 KPH
If there were no speed limit one could go from point a to point b without the passage of time then all reference frames could be coordinated to a single time frame.
[This message has been edited by sidelined, 10-22-2003]
[This message has been edited by sidelined, 10-22-2003]

This message is a reply to:
 Message 16 by Percy, posted 10-22-2003 10:11 AM Percy has replied

Replies to this message:
 Message 19 by Percy, posted 10-22-2003 11:53 AM sidelined has replied

  
Percy
Member
Posts: 22393
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 19 of 103 (62129)
10-22-2003 11:53 AM
Reply to: Message 18 by sidelined
10-22-2003 11:08 AM


sidelined writes:
Ok. When the plane returns it will be back in its own reference frame.
It might be more accurate to say that the plane's reference frame and the ground's reference frame are now congruent.
The plane will have recorded the difference that exists between the ground A and the location-event above earth at B.
This doesn't feel like an accurate statement to me. The plane experienced displacements and accelerations across a broad swathe of space - there was no single location/event at point B.
When it is back in its own reference frame it will, as a result of having travelled to B, be a very tiny fraction of a second younger than the the plane that remained on the ground.
I think this is the key point. The change in age of which plane is the correct measure of the duration of the flight? I think that any criteria you apply to select one or the other will prove arbitrary.
--Percy

This message is a reply to:
 Message 18 by sidelined, posted 10-22-2003 11:08 AM sidelined has replied

Replies to this message:
 Message 20 by sidelined, posted 10-22-2003 12:40 PM Percy has replied

  
sidelined
Member (Idle past 5908 days)
Posts: 3435
From: Edmonton Alberta Canada
Joined: 08-30-2003


Message 20 of 103 (62135)
10-22-2003 12:40 PM
Reply to: Message 19 by Percy
10-22-2003 11:53 AM


The change in age of which plane is the correct measure of the duration of the flight? I think that any criteria you apply to select one or the other will prove arbitrary.
Let us say that the plane A that remains on the ground reads the following 11:14:04576684 at the time of comparison.
The plane B which left and returned reads 11:14:04576385
The difference is 0.00000299 A relative to B
The difference is -0.00000299 B relative to A
The plane A records an increase in age relative to B
The plane B records a decrease in age relative to A
They record the same displacement.They are both correct.

This message is a reply to:
 Message 19 by Percy, posted 10-22-2003 11:53 AM Percy has replied

Replies to this message:
 Message 22 by Percy, posted 10-22-2003 1:56 PM sidelined has replied

  
sidelined
Member (Idle past 5908 days)
Posts: 3435
From: Edmonton Alberta Canada
Joined: 08-30-2003


Message 21 of 103 (62136)
10-22-2003 12:44 PM


I also meant to say that you are correct about that sentence I should have put:"when the plane returns it will be back in its original reference frame."

  
Percy
Member
Posts: 22393
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 22 of 103 (62151)
10-22-2003 1:56 PM
Reply to: Message 20 by sidelined
10-22-2003 12:40 PM


Hi, Sidelined!
There are some UBB codes that making quoting pretty easy. Or you could do quoting your own way. But when you do no quoting at all it makes it difficult to separate cut-n-pasted text from your own text.
sidelined writes:
They record the same displacement. They are both correct.
I'm not sure you're thinking about this correctly. First, when you're measuring the difference between two measurements there is only one difference, not two. Second, we're discussing whether the age of the universe would measure the same in all frames of reference, so the key question isn't the difference between the two clocks, but which clock is correct. As I stated earlier, I think you'll find that any criteria you advance for choosing one over the other will prove arbitrary.
--Percy

This message is a reply to:
 Message 20 by sidelined, posted 10-22-2003 12:40 PM sidelined has replied

Replies to this message:
 Message 23 by NosyNed, posted 10-22-2003 2:26 PM Percy has replied
 Message 24 by sidelined, posted 10-22-2003 2:31 PM Percy has replied

  
NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 23 of 103 (62160)
10-22-2003 2:26 PM
Reply to: Message 22 by Percy
10-22-2003 1:56 PM


Generally it is taken that the reference frame in which no acceleration was measured is the "correct" one.
Now, I'm not sure about this, but I think that since most of the universe has not experienced any inertial accelearation the times for most of it would measure the same time to the big bang.

This message is a reply to:
 Message 22 by Percy, posted 10-22-2003 1:56 PM Percy has replied

Replies to this message:
 Message 25 by Percy, posted 10-22-2003 2:41 PM NosyNed has replied

  
sidelined
Member (Idle past 5908 days)
Posts: 3435
From: Edmonton Alberta Canada
Joined: 08-30-2003


Message 24 of 103 (62162)
10-22-2003 2:31 PM
Reply to: Message 22 by Percy
10-22-2003 1:56 PM


Hey Percy!
I am sorry about the lack of quotation marks.I was probably still trying to bring my caffeine up to operational levels.
Anyway in post #18 I made the analogy of a balloon as being our universe.If we imagine that each point on the balloons surface represents a point in space then all points in space-time are displaced from center by the same amount i.e. As the expansion continues all points on the balloon grow further apart but retain the same distance from center.
I was trying to illustrate that the two clocks are both correct.Since we showed that they were both displaced by the same amount but with opposite signs( 0.00000299 and -0.00000299 )the two cancel out and we find that both locations are measuring the same amount of time relative to the BB though not relative to one another.
Clear as mud yet?

This message is a reply to:
 Message 22 by Percy, posted 10-22-2003 1:56 PM Percy has replied

Replies to this message:
 Message 26 by Percy, posted 10-22-2003 2:49 PM sidelined has replied

  
Percy
Member
Posts: 22393
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 25 of 103 (62165)
10-22-2003 2:41 PM
Reply to: Message 23 by NosyNed
10-22-2003 2:26 PM


NosyNed writes:
Generally it is taken that the reference frame in which no acceleration was measured is the "correct" one.
That can be offered as a convention, and it *is* the simplest, but both clocks in the example are in accelerating reference frames.
Now, I'm not sure about this, but I think that since most of the universe has not experienced any inertial accelearation the times for most of it would measure the same time to the big bang.
I must be missing something, this looks dead wrong. First, inertial and gravitational acceleration are indistinguishable from the point of view of relativity. Second, every object affected by gravity experiences acceleration, and gravity affects all objects in the universe, even very remote ones.
--Percy

This message is a reply to:
 Message 23 by NosyNed, posted 10-22-2003 2:26 PM NosyNed has replied

Replies to this message:
 Message 30 by NosyNed, posted 10-23-2003 5:44 PM Percy has replied

  
Percy
Member
Posts: 22393
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 26 of 103 (62166)
10-22-2003 2:49 PM
Reply to: Message 24 by sidelined
10-22-2003 2:31 PM


sidelined writes:
Anyway in post #18 I made the analogy of a balloon as being our universe.If we imagine that each point on the balloons surface represents a point in space then all points in space-time are displaced from center by the same amount i.e. As the expansion continues all points on the balloon grow further apart but retain the same distance from center.
This is useful as a visual aid, but not helpful in this circumstance since it ignores the effects of relativity.
I was trying to illustrate that the two clocks are both correct.Since we showed that they were both displaced by the same amount but with opposite signs( 0.00000299 and -0.00000299 )the two cancel out and we find that both locations are measuring the same amount of time relative to the BB though not relative to one another.
What you showed was that A-B = -(B-A). I'm afraid I don't understand how that tells us anything useful.
The relevant question is which clock is correct. Before the plane trip both clocks were in synchrony, after the trip they're not. Which clock tells us how much older the universe is since the plane trip began? As I keep saying, I believe that any criteria you apply in making a choice will prove arbitrary.
--Percy

This message is a reply to:
 Message 24 by sidelined, posted 10-22-2003 2:31 PM sidelined has replied

Replies to this message:
 Message 28 by sidelined, posted 10-23-2003 1:43 PM Percy has replied

  
zephyr
Member (Idle past 4550 days)
Posts: 821
From: FOB Taji, Iraq
Joined: 04-22-2003


Message 27 of 103 (62191)
10-22-2003 5:08 PM
Reply to: Message 16 by Percy
10-22-2003 10:11 AM


quote:
Relativity tells us that there is no absolute reference frame, for either location or time, and that there can be no single correct answer for the age of the universe.
(emphasis added) My face probably looked kinda funny when I read that.
I've studied relativity and at least in the basic sense I understand pretty well, but that conclusion kinda threw me for a second. Just think about it. I was reluctant to accept it, but hey... I'm optimized for spearing ungulates on the savannah.

This message is a reply to:
 Message 16 by Percy, posted 10-22-2003 10:11 AM Percy has not replied

  
sidelined
Member (Idle past 5908 days)
Posts: 3435
From: Edmonton Alberta Canada
Joined: 08-30-2003


Message 28 of 103 (62382)
10-23-2003 1:43 PM
Reply to: Message 26 by Percy
10-22-2003 2:49 PM


Both clocks are correct.The universe is the age it is only in terms of the frame of reference.Because the speed of light is constant for all reference frames the spacetime position of ALL frames of reference relative to the BB is the SAME.Each frame of reference will measure the same amount.If you could freeze the universes spacetime motion and could travel backwards through SPACETIME and go to any other eventlocation in the universe somewhere/somewhen else when/where you froze it you would have the same SPACETIME measurment as where you left from to within 10 *-35 meters/10*-43sec error in measurement.(Planckspace/Plancktime)
It is when you move from one event location to another while the universe is in motion that you lose sight of this.Again because the speed of light is limited when you go to another frame of reference you traverse spacetime by an amount equal to the discpency recorded by the clocks.
I am not sure if I have done anything but confuse you.
I will search the web to locate an example that perhaps tackles it in another way because it really requires you to view the world in a counterintuitive way.

This message is a reply to:
 Message 26 by Percy, posted 10-22-2003 2:49 PM Percy has replied

Replies to this message:
 Message 29 by Percy, posted 10-23-2003 3:47 PM sidelined has replied

  
Percy
Member
Posts: 22393
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 29 of 103 (62399)
10-23-2003 3:47 PM
Reply to: Message 28 by sidelined
10-23-2003 1:43 PM


Hi Sidelined,
It seems to me that you're ignoring a logical contradiction when you say this:
Both clocks are correct. The universe is the age it is only in terms of the frame of reference. Because the speed of light is constant for all reference frames the spacetime position of ALL frames of reference relative to the BB is the SAME. Each frame of reference will measure the same amount.
I agree both clocks are correct, but that's only because there is no set of non-arbitrary criteria that would allow you to select which displays the correct time. That they display different times contradicts the rest of your explanation, especially where you state, "Each frame of reference will measure the same amount." The clocks have been briefly in different reference frames, yet do *not* measure the same amount of time. You have to reconcile your viewpoint with the results of the clock experiment, which, as I'm sure you know, has been performed.
--Percy

This message is a reply to:
 Message 28 by sidelined, posted 10-23-2003 1:43 PM sidelined has replied

Replies to this message:
 Message 31 by sidelined, posted 10-23-2003 6:02 PM Percy has replied

  
NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 30 of 103 (62411)
10-23-2003 5:44 PM
Reply to: Message 25 by Percy
10-22-2003 2:41 PM


but most of the points in the universe are subject to negligable gravity effects ( I think???) and most of it has been moved by the expansion of space not by an inertial acceleration. So most points will measure the same time back to the big bang. That is my conjecture at least.

This message is a reply to:
 Message 25 by Percy, posted 10-22-2003 2:41 PM Percy has replied

Replies to this message:
 Message 33 by Percy, posted 10-23-2003 7:57 PM NosyNed has not replied

  
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