How old is the Universe?

[idav]

I think one of the things you're asking is, if time is relative and all that, then how can they put a fixed time on the universe, like 13.7 billion years? 13.7 billion years relative to which reference frame?

The answer is that the reference frame they use to determine this age, is one that follows along with the expansion of the universe. It's the reference frame for which the background cosmic radiation has always been nearly isotropic (uniform in all directions). Basically, it's the reference frame that moves along with the expansion of the universe, at rest relative to the universe, from the beginning. If people were to measure the age of the earth, the reference frame they'd use as being most appropriate would be the reference frame that has always co-moved with the earth and therefore never moved relative to the earth. Similarly, if people were to measure the age of the universe, the reference frame they'd use as being the most appropriate would be the reference frame that has always co-moved with the universe, which means never having moved within the universe, and always just moving along with the expansion of the universe itself.

I think the second part of the question has to do with a misinterpretation of what it means for the universe to expand faster than the speed of light. The expansion of the universe through any finite amount of space is relatively slow. The expansion is not itself occurring at the speed of light. However, due to the vast distances in the universe, objects that are very far away from each other can move away from each other faster than the speed of light, due to the cumulative effect of expansion between them.

For example, if I take a rubber band and stretch it at a rate of 1 millimeter per second per centimeter of length, and my rubber band is 1 trillion centimeters long, then two points on each end of this rubber band will be expanding away from each other exceedingly quickly even though the speed of expansion at any one point is quite slow.

This is some great info which helps a bit. What I find strange is that we as in our galaxy is moving away from the center of the universe at the speed of light, so where does the observer come into play? Is time really going as fast as we think it is?

 

[PolyHedral]

This is some great info which helps a bit. What I find strange is that we as in our galaxy is moving away from the center of the universe at the speed of light, so where does the observer come into play? Is time really going as fast as we think it is?

There is no center of the universe.

 

[Gjallarhorn]

There is no center of the universe.

At least, no center of the universe within the universe.

 

[Penumbra]

This is some great info which helps a bit. What I find strange is that we as in our galaxy is moving away from the center of the universe at the speed of light, so where does the observer come into play? Is time really going as fast as we think it is?

I'm not sure if your viewing it like this, so I apologize of this is not news to you, but it may clarify some things: Many people seem to misunderstand the (perhaps poorly named) Big Bang to mean that space existed already, and that matter exploded into existence, and that there is therefore some center from which we are all flying away from. But that's not how the Big Bang theory works.

There is no spatial center of the universe in the Big Bang Model, because the whole concept of the Big Bang is that the universe itself expanded from a singularity to what it is today. That is, spacetime itself expanded from nearly nothingness. The Big Bang was determined to have occurred by observing that the universe is expanding, and that therefore if one were to follow this trend back to the "beginning", one would have a singularity.

-So there is no "center" of the universe from which we are flying away from. The model proposes that all that exists, previously existed as a singularity or nearly so, and so we're all part of the center.

-Similarly, because there is no center, there is no center that we're moving away from at the speed of light. Galaxies do indeed move through space, but not nearly at the speed of light. In addition to their movements, the cumulative effects of the expansion of space result in galaxies increasing in distance away from each other at sometimes faster than light speed, but they're not moving through space at this speed, and therefore the time dilation in the theory of relativity is not involved. General relativity, and the concept of time dilation that comes with it, concerns objects moving through space, not spatial expansion.

-A way to think of this is to imagine two ants walking on the previously described expanding rubber band. If the ants represent any object that can move through space, and the rubber band represents space itself, then certain rules of physics concern their ability to walk on the rubber band, including general relativity. But other rules, possibly related ones, concern the rubber band's ability to stretch. The rate at which each ant moves via their own walking on the rubber band, is different from the rate at which the ants are moving in terms of absolute distance. They could be walking towards each other and yet moving away from each other if I'm expanding the rubber band between them.

-Time appears to move to one object compared to another object based on how those objects are moving compared to each other. The measurement of the age of the universe uses the reference frame that doesn't move through the universe but that instead remains in a way that the expansion is isotropic, and therefore has no time dilation compared to the universe as far as I understand it. If other objects (and their reference frames) are moving about, then their rate of time change can differ from other objects and reference frames.

 

[apophenia]

There is no spatial center of the universe in the Big Bang Model, because the whole concept of the Big Bang is that the universe itself expanded from a singularity to what it is today. That is, spacetime itself expanded from nearly nothingness. The Big Bang was determined to have occurred by observing that the universe is expanding, and that therefore if one were to follow this trend back to the "beginning", one would have a singularity.

Nearly nothingness is infinitely different to nothingness.

This is why I posted the idea that we are not actually asking "how old is the universe", but "how long since the big bang".

That "nearly nothingness" is like a seed. We can ask "how old is this tree ?", but the question is actually "how long since the seed of this tree germinated ?".

Physically, a tree is one and the same as its ancestors - there is a physical continuity. So the "nearly nothingness" is also the universe just as a seed is the tree. There is no discontinuity there.

 

[Penumbra]

Nearly nothingness is infinitely different to nothingness.

This is why I posted the idea that we are not actually asking "how old is the universe", but "how long since the big bang".

That "nearly nothingness" is like a seed. We can ask "how old is this tree ?", but the question is actually "how long since the seed of this tree germinated ?".

Physically, a tree is one and the same as its ancestors - there is a physical continuity. So the "nearly nothingness" is also the universe just as a seed is the tree. There is no discontinuity there.

I specifically used the phrase nearly nothingness because the Big Bang model only has something to say starting in the split second after whatever it was that came before it. That's all the model has to say.

Anything prior to that is speculative. Oscillating universes, a multiverse producing various universes, etc. But the OP was specifically about expansion and time.

 

[apophenia]

I specifically used the phrase nearly nothingness because the Big Bang model only has something to say starting in the split second after whatever it was that came before it. That's all the model has to say.

Anything prior to that is speculative. Oscillating universes, a multiverse producing various universes, etc. But the OP was specifically about expansion and time.

I'm not disagreeing with you.

I was responding to the thread title really, and pointing out that the universe "in the split second after whatever it was that came before it", and "whatever it was that came before it" are one and the same in the manner of the seed/tree analogy given.

So we don't have a beginning, but a change of state of something, one of the states of which is this universe. I suppose that may be off-topic. Hard to say - it's a damn slippery topic.

 

[outhouse]

I'm not disagreeing with you.

I was responding to the thread title really, and pointing out that the universe "in the split second after whatever it was that came before it", and "whatever it was that came before it" are one and the same in the manner of the seed/tree analogy given.

So we don't have a beginning, but a change of state of something, one of the states of which is this universe. I suppose that may be off-topic. Hard to say - it's a damn slippery topic.

i want to agree with the seed idea, but its due to my ignorance.


reality is there was never a seed to start with, there are other dimensions that time as we know it does not. nor ever existed.


because we dont know, doesnt mean imagination has any credibility

 

[apophenia]

i want to agree with the seed idea, but its due to my ignorance.


reality is there was never a seed to start with, there are other dimensions that time as we know it does not. nor ever existed.


because we dont know, doesnt mean imagination has any credibility

I don't get what you are trying to say here. Although it is a similar remark to one you made to me often in another thread, also without any basis. i.e. you suggest that I am 'imagining things' if I reference anything which is not understood by science, as though I were thereby suggesting something supernatural or mystical. I'm not.

If there 'was never a seed to start with', then take it up with Penumbra over her phrase 'nearly nothing'. ( Or take it up with all the physicists who use that or similar phrases). As far as I understand ( and I don't claim to understand much), the idea that there was 'nothing' before the big bang is not considered correct by contemporary physicists. So I am referring to whatever this 'nearly nothing' may be, as a seed, for the sake of analogy.

How do you conceptualise what this 'nearly nothing' was ? Do you use your imagination at all in your conceptualisation ? If so, tsk tsk, you're a closet mystic with no credibility !

For the record outhouse, what is it that I am imagining which has no credibility ? Because I'm ****** if I know what you are referring to.

And please clarify what you mean by "there are other dimensions that time as we know it does not. nor ever existed. " I can't make head or tail of that. And don't use your imagination at all to answer that !

 

[Sir Doom]

I thought time was another dimension >.>

 

[InformedIgnorance]

The universe is six seconds old (prior to YOU reading this, not me posting this); that is how long ago I decided to create the universe - and you cant prove me wrong because everything that seems to be older than six seconds was created that way as part of my convoluted plan.

 

[Sir Doom]

The universe is six seconds old (prior to YOU reading this, not me posting this); that is how long ago I decided to create the universe - and you cant prove me wrong because everything that seems to be older than six seconds was created that way as part of my convoluted plan.

No way, the universe started ~33 years ago when I was born. You're all welcome, btw.

 

[PolyHedral]

I thought time was another dimension >.>

It is. Anyone who says it isn't is talking about something else, which may or may not be garbage.

 

[idav]

There is no spatial center of the universe in the Big Bang Model, because the whole concept of the Big Bang is that the universe itself expanded from a singularity to what it is today. That is, spacetime itself expanded from nearly nothingness. The Big Bang was determined to have occurred by observing that the universe is expanding, and that therefore if one were to follow this trend back to the "beginning", one would have a singularity.

-So there is no "center" of the universe from which we are flying away from. The model proposes that all that exists, previously existed as a singularity or nearly so, and so we're all part of the center.

The center I'm taking to be the reference point for the singularity that we are observing.

-Similarly, because there is no center, there is no center that we're moving away from at the speed of light. Galaxies do indeed move through space, but not nearly at the speed of light. In addition to their movements, the cumulative effects of the expansion of space result in galaxies increasing in distance away from each other at sometimes faster than light speed, but they're not moving through space at this speed, and therefore the time dilation in the theory of relativity is not involved. General relativity, and the concept of time dilation that comes with it, concerns objects moving through space, not spatial expansion.

Though we are moving rather quickly through space. The planets the solar system and galaxies are all moving through space for the same reasons space is expanding, because of the initial expansion set into motion. So objects are flying through space at the same time space is expanding.

-A way to think of this is to imagine two ants walking on the previously described expanding rubber band. If the ants represent any object that can move through space, and the rubber band represents space itself, then certain rules of physics concern their ability to walk on the rubber band, including general relativity. But other rules, possibly related ones, concern the rubber band's ability to stretch. The rate at which each ant moves via their own walking on the rubber band, is different from the rate at which the ants are moving in terms of absolute distance. They could be walking towards each other and yet moving away from each other if I'm expanding the rubber band between them.

This is a helpful analogy that goes into my comment above. What if two ants are moving at different speeds with two rubber bands also stretching at different speeds. Somebody is going to observe a time dilation regardless as long as the two moving objects are going at different speeds.

Then the other aspect is that space is stretching making the objects go further without actually going that speed? I'd have to say that if the objects are moving and time is stretching then their speed is equal to both measurements combined. So that if the ants were walking away from each other it is possible that the stretching rubber band could carry them quicker. That is how I see the objects during the beginning stages of the big bang, that they were objects moving at the speed of light likely at the same speed the space was stretching.

-Time appears to move to one object compared to another object based on how those objects are moving compared to each other. The measurement of the age of the universe uses the reference frame that doesn't move through the universe but that instead remains in a way that the expansion is isotropic, and therefore has no time dilation compared to the universe as far as I understand it. If other objects (and their reference frames) are moving about, then their rate of time change can differ from other objects and reference frames.

Could be that the stretching of the universe is actually causing the time dilation for two moving objects. If two objects are moving away from each other the time dilation should still be there regardless of how the universe is stretching. My thought is that if you moving as fast as the universe is stretching then this could be why time literally slows down. At the point of a singularity it would be similar to a black hole where time slows down to a stop. Seems the only reason there is time is because the universe is stretching. Time does some very strange things and is effected by speed and gravity so it is very fascinating and confusing. I think I understand how time is effected with moving objects but I don't really understand how a stretching space-time effects time. It all sounds very sci-fi to me.

 

[PolyHedral]

The center I'm taking to be the reference point for the singularity that we are observing.

The singularity was everywhere, and the remnants of the singularity are still everywhere; that is, the cosmic background radiation emanates from everywhere.

Though we are moving rather quickly through space. The planets the solar system and galaxies are all moving through space for the same reasons space is expanding, because of the initial expansion set into motion. So objects are flying through space at the same time space is expanding.

Contrariwise, I am still. This is the fun of motion, (and to a certain extent, rotation) being relative.

Also, the mechanisms of normal motion and the expansion of the universe are completely different. Notably, the first is well understood, the second is almost not at all.

Could be that the stretching of the universe is actually causing the time dilation for two moving objects.

It isn't, unfortunately. Time dilation is caused due to the mechanics of embedding motion in 3D space into 4D spacetime.

 

[Penumbra]

The center I'm taking to be the reference point for the singularity that we are observing.

All spacetime was once that singularity. There is no center of the universe you can use as a reference.

Though we are moving rather quickly through space. The planets the solar system and galaxies are all moving through space for the same reasons space is expanding, because of the initial expansion set into motion. So objects are flying through space at the same time space is expanding.

Motion of objects through space, and the expansion of space between objects, are two very different types of "motion". So to say they occur for the same reasons, as far as current physics are concerned, is not accurate.

Motion due to objects moving with velocity through space, and "motion" due to expansion of space itself between objects, are fundamentally different concepts.

This is a helpful analogy that goes into my comment above. What if two ants are moving at different speeds with two rubber bands also stretching at different speeds. Somebody is going to observe a time dilation regardless as long as the two moving objects are going at different speeds.

In this case, if the ants represent objects that can move through space and the rubber band is space itself, time dilation occurs for the ants motion along the rubber band, but not for the stretching of the rubber band itself.

Then the other aspect is that space is stretching making the objects go further without actually going that speed? I'd have to say that if the objects are moving and time is stretching then their speed is equal to both measurements combined. So that if the ants were walking away from each other it is possible that the stretching rubber band could carry them quicker. That is how I see the objects during the beginning stages of the big bang, that they were objects moving at the speed of light likely at the same speed the space was stretching.

Could be that the stretching of the universe is actually causing the time dilation for two moving objects. If two objects are moving away from each other the time dilation should still be there regardless of how the universe is stretching. My thought is that if you moving as fast as the universe is stretching then this could be why time literally slows down. At the point of a singularity it would be similar to a black hole where time slows down to a stop. Seems the only reason there is time is because the universe is stretching. Time does some very strange things and is effected by speed and gravity so it is very fascinating and confusing. I think I understand how time is effected with moving objects but I don't really understand how a stretching space-time effects time. It all sounds very sci-fi to me.

If an object tries to move through space and accelerate, then as it approaches the speed of light, it will need more and more energy. It becomes exponential, and infinite energy is needed to reach the speed of light, and therefore the speed of light cannot be reached by objects with mass. As an object gets closer to the speed of light, time dilation occurs, but also length contraction. Objects will become infinitesimally short as they approach the speed of light.

When space itself is expanding between objects, however, this not the case. The objects are not moving through space, and therefore these various effects of relativity don't come into play. Objects can move away in distance from each other faster than the speed of light due to the expansion of space, but they're not moving through space at the speed of light and therefore the effects of relativity are not apparent. So they don't need infinite energy to do this and they don't become infinitesimally short or experience that sort of time dilation. And as previously stated, the rate of expansion is fairly slow. It only becomes a major thing over absolutely immense distances.

Motion of objects through space is fundamentally different than increases in distance of objects due to spatial expansion. Treating these as the same type of motion as though they follow the same type of physics for what they're doing would be incorrect as far as current physical models and evidence are concerned.

 

[apophenia]

As an object gets closer to the speed of light, time dilation occurs, but also length contraction. Objects will become infinitesimally short as they approach the speed of light.

Does that mean the atoms and molecules which constitute these objects become 'shorter' ? My mind can't seem to wrap around that. By 'short' do you mean the change only occurs in the longitudinal axis (direction of acceleration) of the object ? Are particles considered 'objects', and do particles become infinitesimally short ?

Forgive my humungous ignorance BTW. I realise that any questions I am likely to ask about this will probably make anyone with some understanding roll their eyes.

 

[PolyHedral]

Does that mean the atoms and molecules which constitute these objects become 'shorter' ? My mind can't seem to wrap around that. By 'short' do you mean the change only occurs in the longitudinal axis (direction of acceleration) of the object ? Are particles considered 'objects', and do particles become infinitesimally short ?

Forgive my humungous ignorance BTW. I realise that any questions I am likely to ask about this will probably make anyone with some understanding roll their eyes.

Yes, for all of those. "Spherical" particles flatten out like pancakes when travelling at speeds close to c.

 

[apophenia]

Yes, for all of those. "Spherical" particles flatten out like pancakes when travelling at speeds close to c.

OK. So given that molecules have complex 3D shapes determined by the way the atoms share electrons, presumably the molecules would come unstuck and be reduced to a thin cloud of disconnected pancaked-shaped particles ? In other words the idea of a spaceship approaching the speed of light is impractical if for no other reason than the craft and its occupants would be reduced to a soap-bubble thin smear of particle soup ?

 

[PolyHedral]

Assuming you can get them up to that speed slow enough not to soup them, then no. The electron orbits get bent out of shape too, so the whole thing stays in one piece.