Age of the Universe

Hey Percy."That they display different times contradicts the rest of your explanation, especially where you state, "Each frame of reference will measure the same amount."There is no contradiction.We will consider the balloon again only this time we will elaborate.This balloon starts with its center at the origin of the universe and as it expands space through time the present resides at the surface of an immense sphere that grows a larger space with longer times away from origin.Now freeze the balloon.Every point on the surface of the ballon can measure its distance back to center (origin of universe) to be the same in terms of light years.
Because the speed of light is constant and limited the only information we can glean is from looking at the universe as it appears to us in our frame of reference.It is for this reason that we seen things as they were in the past.Every point in space is subject(presumably) to the same resrictions.
Now,back to the planes which are occupying the same reference frame.
They are together the same distance in light years from the BB.Now,please bear in mind that this sphere is moving and getting larger and older constantly.If we take the airport where they begin as being a point on the sphere,when plane B takes off it is displacing itself into another frame of reference,however,it is still moving with the rest of the universe. If Plane A on the ground can be considered to trace a straight line through spacetime during Plane B's flight then plane'B's flight path takes a curved line out to its farthest point and back to plane A.
Upon return when the clocks are compared and the two clocks are found to differ slightly the only variable has been Plane B's flight path.The only thing we can conclude is that what the clocks have measured is the difference between the reference frames.This difference can be interpreted as a result of the limited speed in exchange of information from one frame of reference to another.
The difference in the clocks recordings are a reflection of the ratio between the velocity of Plane B through a dynamic spacetime to the speed of light, spacetimes upper limit of information transfer.My brain is feeling the burn.Please help point out any inconsistancies and I am quickly learning it is far easier to grasp a concept than to teach it.[This message has been edited by sidelined, 10-23-2003]

This bit is wrong. We are discussing time and distance in the 4 dimensions of our universe. In the balloon analogy that is the 2 dimensional surface of the ballooon. The centre of the balloon in 3 space is not part of the balloon 'universe'. The big bang isn't at the center of our 4D space time it is "everywhere". There is no "center" to the universe. Just as there is no special starting place on the balloons surface.

But you don't really believe that small effects and zero effects are the same thing, do you? A little gravity for a few billion years, it adds up. The differences in the passage of time will not be small.I'd have to agree that most of space is nearly empty and far from large conglomerations of matter, and that the age of the universe measured from these places might be fairly similar, but certainly not identical. And while some reference frames are in deep space and have experienced little gravity, others are at the event horizon of black holes.But I only mentioned acceleration to note that gravitational and inertial acceleration are indistinguishable from the point of view of Einsteinian relativity. It only take relative motion for relativistic effects like time dilation to be experienced, so when you say this: I won't address the part about the expansion of space because I don't think it's relevant. What's significant is that even without any acceleration (impossible, of course - everything is always in a gravity field, even if a small one) the different relativistic effects of different motions guarantee different time dilations.The clock experiment I keep describing for sidelined tells us that time is different in different reference frames. You've got two clocks in the same reference frame that once were synchronized and now display two different times after one goes on a brief trip. If clocks in the same reference frame can come to differ, than most certainly clocks in different reference frames will differ.--Percy

Percy, you have got it right, but I would like to emphasize a few points here.
Relativistic travel is RELATIVE. If two observers are in relative motion, each will see the other's clock running slow. It is the CHANGES in motion, where one leaves the other, then turns around and comes back, which create inertial/gravitational effects which result in their clocks disagreeing on the traveller's return.
A gravitational field does slow clocks down. Our clocks run slower than those out in space. So our measure for the age of the universe is a little lower than the 'real' age. But we can compute this and correct out estimates - but who cares, when the uncertainty in the age estimates is billions of times larger.
So if you sit still close to an event horizon, a la Humphreys' theory, then your clock might measure 6000 years since the big bang. But the rest of Humphreys' theory is crap. The whole scene of the universe being inside an event horizon and expanding out through it while it contracts is ridiculous. Energy can 'come out' of a black hole only throught Hawkins' fuzzy black hole process, at the quantum level.
Mike.

Hey NosyNedWe are discussing time and distance in the 4 dimensions of our universe. In the balloon analogy that is the 2 dimensional surface of the ballooon. The centre of the balloon in 3 space is not part of the balloon 'universe'My apologies, I do understand the limitations of the 2d ballon however I don't believe it would affect the outcome of the thought experiment but it does complicate the way the universe actually appears.
I was,of course,requiring of the reader to imagine the passage of time as being represented in the expansion of the balloon.Since the sticking point was how we explained the discrepancy of how when both planes were back in the same inertial frame of reference the clocks were differing by a little I had hoped to show that it was the measurement of the displacement between them and not a measurement of their event-locations displacement from the BB.It might be useful to imagine the same scenario using instantaneous transmission of information,that is,no limit on the speed of light and play it through.

Thank you. You are right of course, the dimension back into the ballon could be taken as the time dimension. So the universe is the 3D balloon in that analogy.However, doing so might be a little dangerous. It is hard enough for one to get their head around what is going on. If you step outside of the surface of the balloon as being *all* there is then you have the balloon looking to much like an "explosion" and this could be confusing.The time dimension might be best kept "in" the surface of the balloon in some manner.

The time dimension is indeed embedded in the balloon itself.This is the reason I tried to limit separating time from space by saying spacetime and event-location.As in the real universe the concept of time is not separate from the movement of our three dimensions.
In my example the balloons expansion is not separate from the balloons surface itself.
Trying to explain this and keep cohesion is indeed dangerous.I am still trying to cool the brain cells.

My reply to your balloon analogy hasn't changed. Your balloon doesn't include relativistic effects. I don't think what you're trying to say has any meaning. After seeing NosyNed's response, I guess I'd have to say his observations about your balloon analogy apply here as well. I think you may have let this analogy lead you to erroneous conclusions about other things related to relativity. Your description doesn't address relativistic effects. The biggest inconsistency I see in your viewpoint is that it includes the concept of absolute time in relativity. The choice of the term "relativity" for the theory's name was not arbitrary. Your view of relativity seems to include only relative motion - it ignores the very real relativistic effects of that motion. You also have yet to reconcile the difference in time between the two clocks.If it helps, begin your next post by completing the sentence, "The clocks are different but still give us just one age for the universe because..."--Percy

Maybe it would help if you explained where your balloon analogy comes from. I don't think I've ever seen anyone explain relativity using a balloon. I wonder if you might be borrowing an analogy from cosmology and misapplying it in an relativistic context.--Percy

I admit that I may be in error as I am not speaking from any expert position but the by the way I have percieved the little bits of knowledge I have gained here and there.Let us see if we can find the error in my thinking.I used the balloon analogy that I did indeed get from another physics example some years ago.(I believe they were dealing with the red shift of starlight).In this anaolgy I was trying to place myself back at the moment of origin and follow up from there to the limits of my knowledge.So we begin with the universe that we see today compacted into a fantastically small time and place.I am assuming the four dimensions are already established since I further assume this is the impetus for the beginning of spacetime actually happening.Now I do not have any real knowledge one way or another that allows me to say the universe expands equally along all 4 dimensions.I am aware of two assumptions made by Einstein concerning special relativity.Inertial frames are introduced which, by definition, are in uniform motion with respect to each other. The whole theory is based on two postulates:-
1. The laws of physics take the same form in all inertial frames.
2. In any inertial frame, the velocity of light c is the same whether the light is emitted by a body at rest or by a body in uniform motion.Now from the second postulate we have a counterintuitive conclusion. We can no longer add velocities the way we normally would.If you are standing at the edge of the ocean and I am flying overhead the light from my airplane to you will take the same amount of time as light from you to me You need not subtract my forward motion away from you and here is why.From my vantage point in the plane I can just as readily say that you are receding from me at say,450 mph,as you can say from your point at the shoreline that I am moving away at 450 mph.as far as the speed of light is concerned.This is a relativistic effect.
Now how does this apply to clocks on board my aircraft and your watch on the ground(both are finely crafted swiss movement atomic clocks) : ).Since the speed of light is the same on board the aircraft as it is from your vantage point some physical quantity must be changing to balance things out.Now you are really going to kill me because I have to shut down my posting for the night as I am finally returning to work tomorrow after being on injury list for 6 weeks and 5 o'clock comes early.I will take up where I left off tomorrow around 8 P.M. forum time. Good night all

They don't balance out. Relativity says that time in different reference frames is different. There is no reconciliation, even when previously distinct reference frames conjoin. There is no absolute time or universal master time. There is no such thing as simultaneity in the real universe. The clock experiment is real.The conundrum that I think you're describing is that both the person in the airplane and the person on the ground perceive the other's clock as counting seconds more slowly than their own, but from the point of view of the person on the plane by the time he lands the clock on the ground has not only caught up, it is actually ahead of his own. Where and when did this catching up occur?I don't have answers for these questions at a detailed level, but there is another way of carrying out the thought experiment that might be helpful. Let us imagine that the airplane is flying overhead and that we're in radio communication with it. We use the radio link to synchronize the clocks (we know the distance between ground and plane and take the speed of light into account), let them run for one second, during which the airplane is still pretty much directly overhead, and both observers observe the other clock as running slower. Now we somehow stop the plane through sudden deceleration so that there is no longer any relative motion between ground and plane (I know planes can't come to a quick stop in mid-air, but that's why it's called a thought experiment - if it helps, imagine it has a huge, massive rocket in the nose that we fire), and we use the radio link to compare the times of the two clocks, again taking into account the speed of light distance between them.What they will both find is that the clock on the ground is now slightly ahead of the clock on the plane. It is the deceleration that does this. Remember that the greater the gravity well the greater the relativistic effects, and that inertial and gravitational accelerations are indistinguishable by relativity, so the plane's sudden deceleration is equivalent to a very short period in a very strong gravity well. In other words, during the deceleration the clock on the plane moved *much* more slowly than the clock on the ground, and even though this was for only a very short time period, it was sufficient to cause the difference.If we go back to the original experiment where the plane actually continued it's flight and landed on the ground, it is the sum of all the accelerations and decelerations experienced by the plane that cause its clock to eventually be behind the clock on the ground.--Percy

That is correct there is no absolute time.Time is the property that changes to preserve the paradox brought on by the speed of light being constant in all inertial reference frames.Anyone remaining on the earth's surface maintains the same inertial reference frame[except for tiny changes due to different latitudes and elevations].
When a plane goes up into the air time slows down through a process called time dilation.A person in the plane would see the clock of the person on the ground speed up while someone on the ground would see the planes clock slow down(as judged after the fact by the atomic clocks relative to one another)
The clock that went up in the plane slowed down relative to the ground.The clock that remained on the ground sped up by an equal amount relative to the plane.Both changes are equal in magnitude.
This is the formula for tracking those changes.t'=t*[(Sqrt)1-V*2/C*2]t'is the dilated time
t is staionary time
v is velocity (in this case the plane)
c is the speed of lightWe can set t to equal 1 since we are interestedi n solving for t'.
let us assume a velocity for the plane of 100 meters per second
speed of light is 300,000 kilometers per secondNow without doing the math we understand that the answer is going to be exceedingly small which is why they used the atomic clocks.Now as for the issue of location in spacetime as relates to the BB.
Can you see now that since time slows down for the plane relative to the ground by the same amount that time speeds up for the ground relative to the plane that the efect cancels itself out?

sidelined writes: Anyone remaining on the earth's surface maintains the same inertial reference frame[except for tiny changes due to different latitudes and elevations].
When a plane goes up into the air time slows down through a process called time dilation.A person in the plane would see the clock of the person on the ground speed up while someone on the ground would see the planes clock slow down(as judged after the fact by the atomic clocks relative to one another)
The clock that went up in the plane slowed down relative to the ground.The clock that remained on the ground sped up by an equal amount relative to the plane.Both changes are equal in magnitude.
This is the formula for tracking those changes.t'=t*[(Sqrt)1-V*2/C*2]t'is the dilated time
t is staionary time
v is velocity (in this case the plane)
c is the speed of lightWe can set t to equal 1 since we are interestedi n solving for t'.
let us assume a velocity for the plane of 100 meters per second
speed of light is 300,000 kilometers per secondNow without doing the math we understand that the answer is going to be exceedingly small which is why they used the atomic clocks.Now as for the issue of location in spacetime as relates to the BB.
Can you see now that since time slows down for the plane relative to the ground by the same amount that time speeds up for the ground relative to the plane that the efect cancels itself out?This is a very interesting topic but there is another way to illustrate length contraction which indicates how closely related it is to time dilation. We can use the time dilation result to shows directly that length contraction is a necessary consequence of time dilation. Two different inertial observers, one sitting on a train moving through a station with uniform velocity V and the other at rest in the station, want to measure the length of the station's platform. Consider what each observer measures:The ground observer in frame S measures the length to be delta x, a proper length in this case. He claims that the passenger covered this distance in a time interval.

quote:

---

When a plane goes up into the air time slows down through a process called time dilation.A person in the plane would see the clock of the person on the ground speed up while someone on the ground would see the planes clock slow down(as judged after the fact by the atomic clocks relative to one another)
The clock that went up in the plane slowed down relative to the ground.The clock that remained on the ground sped up by an equal amount relative to the plane.Both changes are equal in magnitude.
This is the formula for tracking those changes.

---

This doesn't seem right to me. If the plane and the earth are each inertial reference frames (all IRF's are equal), then: 1.) the person on the ground would see the clock slow down on the plane, and 2.) the person on the plane would see the clock slow down on the ground.JustinC

quote:

---

It appears to be the same question stated two different ways. Time began x bya, so naturally the time dimension stretches back x by

---

In order for time to begin, doesn't there need to be a dimension to reference 'begin'? This is what I don't get. Physicists say the universe-space-time and energy-began 14 billion years ago. To me, though, it doesn't make sense to say that time 'began', because when we say 'began' we mean 'began to exist in time'. It doesn't seem like you can use it in any other context.Now saying the the time-dimension stretches back 14 by doesn't seem to imply that it 'began' to exist at any point.