Age of the Universe

What does it mean to say the universe is x years old? On top of that, what do we mean when we say the universe, are we referring to space-time and energy? If so, how does it make sense to put an age on time?JustinC

JustinCy writes:

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What does it mean to say the universe is x years old?

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The short answer is that it means X years ago, the Big Bang that gave rise to the universe that we seem to be occupying occurred.

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On top of that, what do we mean when we say the universe, are we referring to space-time and energy?

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Yes.

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If so, how does it make sense to put an age on time?

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Quantum mechanically, yes.If our understanding of the process is accurate, there was no such thing as time until the creation of time at the Big Bang.------------------
Rrhain
WWJD? JWRTFM!

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If our understanding of the process is accurate, there was no such thing as time until the creation of time at the Big Bang.

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Wouldn't there have to be another dimension (some 'absolute' time) in which we could reference the universe's creation if we are saying it was created x years ago?Or when we say time is 14 billion years old, are we just describing how far the "t-dimension" goes back?JustinC

No. And if you think about it your suggesting makes no sense. If there is a 'other time dimension' in which our universe's creation took place then it must be orthogonal to out universe (since we cannot be aware of it) and thus our universe's time is entirely independent of this 'other' time.The term 'created' is a misnomer anyway. It's more accurate to say the big bang happened x bya than to say the universe was created x bya.

The universe has a speed limit imposed on it by its very structure.You are aware that the speed of light is the same for all observers and thast there is no "abolute time" correct?So what this means is that as we look out into space to any object we see that object as it was in the past.No information can arrive at a greater speed.This is the reason for the term known as space-time.The two are like different sides of the same coin.For instance the light from the sun's surface takes a little over 8.5 minutes to reach us.The closet star (Alpha Centauri) is 4.3 light years away.
the next nearest galaxy is 2,000,000 light years.Space -time is the four dimensional fabric that makes up our universe in general.

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The universe has a speed limit imposed on it by its very structure.You are aware that the speed of light is the same for all observers and thast there is no "abolute time" correct?

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Yes, I'm well aware of this.When we say that something is x years old, we are making a reference to its position on the t-axis, right? But when someone says the universe is x years old, it seems they are talking about the position of the t-axis on the t-axis. That doesn't seem to make sense to me.When I say 'absolute time', I just mean another dimension in which to reference the t-axis.JustinC{Note: Highest course in physics is the college course Intro. to Physics. In other words I know very little about the subject)

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No. And if you think about it your suggesting makes no sense. If there is a 'other time dimension' in which our universe's creation took place then it must be orthogonal to out universe (since we cannot be aware of it) and thus our universe's time is entirely independent of this 'other' time.

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I'm not saying there is another dimension. I'm just saying it seems there would have to be if we are giving the age of time itself.

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The term 'created' is a misnomer anyway. It's more accurate to say the big bang happened x bya than to say the universe was created x bya.

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So did time happen x bya? Or does the t-dimension streth back x by?

Yes.When I first saw this thread yesterday I thought you were trying to indirectly make a subtle point about relativity, but now that the thread has drawn some discussion it would seem not. But I wonder if the answer to the question is relative? We can answer the question of the age of the universe relative to the earth, but wouldn't it be a different answer in a different reference frame?--Percy

No because from the point of view of another place in the universe a intelligent being would find a similar age and a similar distribution of galaxies.If you follow it it does make sense.By going back further in time you have more things occupy the same location-event.
At the limit of our mathematics and physics we find that everything in the universe occupied an incrediblely small size at an unheard of fraction of time after initiation.everything you are was a part of everything else compacted in.

Your characterization seems at odds with general relativity theory to me. Since an atomic clock can go up in an aircraft and upon return no longer be sychronized with a clock that remained on the ground, in the same fashion observers in different parts of the universe should trace their history back to the big bang along different length time lines.--Percy

This would be true except since time and space are one as time flows space expands equally for the whole shebang.When the aircraft goes up it also traverses space to a location in a different frame of reference.
It requires an atomic clock in order to measure the tiny change between the two different points in space.Remember according to relativity you can start with either location and measure the same displacement and so each position views the same time change and the same space changerelative to their location in space-time.
There are all sorts of strange consequences of relativity including that mass increases as you increase your speed towards that of light.This is the reason for the unlikely possibility of travel at light speed since as you accelerate you increase in mass which requires a greater amount of accelerant until it is to great by way of diminishing returns.
I can get the mathematics to you if you wish .High school algebra would be enough.[This message has been edited by sidelined, 10-21-2003]

This still doesn't sound right to me. You start with two synchronized atomic clocks side-by-side on the ground. You send one up in an aircraft while the other remains on the ground. The aircraft returns and you again set the atomic clocks side-by-side. They are no longer synchronized, one is a bit behind the other. One traces a bit less time between itself and the big bang than the other. This implies that the amount of time that has passed since an event, including the big bang, will not measure the same in all reference frames. It will even depend upon the velocity history of your measuring instrument, be it a clock or distant galaxies.--Percy

One traces a bit less time between itself and the big bang than the other.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.If you started with two in the air,sent one to the ground and back it would measure the same change as starting on the ground.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.It was contained in a space ,as far as our physics can tell,10*-35 meters at 10*-43 second past creation.Everything started together at outrageously immense temperature all of it at once expanding in four dimensions(actually 9 or more if you really want to burst some brain cells)It is the conceptual difficulty prevalent in things like what did expand into that confuses.It didn't expand into anything,but rather,created the thing (space-time) that we percieve ourselves contained in.What occured before is meaningless since before is a time concept that has no meaning prior to a beginning in time.I shall let you stew in that and see if we can grip hold of things.

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JustinCy writes:
So did time happen x bya? Or does the t-dimension streth back x by?

Yes.

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Which question are you saying yes to? Or was that a joke?

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We can answer the question of the age of the universe relative to the earth, but wouldn't it be a different answer in a different reference frame?

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Isn't every place in the universe equidistant to the BB in all axises? So it wouldn't necessarily matter exactly where you were, right?JustinC

It is correct if you recall that it is not just distance but time as well.From any given point in the universe all other points appear to receding and accelerating relative to them.