Is the universe expanding or are we shrinking?

Both, it is a matter of perspective. Similarly, your eye moving or is the origin of the universe changing?

Both, it is a matter of perspective. Similarly, your eye moving or is the origin of the universe changing?

Does the universe have an origin (in that sense)?

EDIT: Appears that I am not the first to think this: martinelli.org/rexpansion

One thing strikes me as odd in that article. If we are 2 meters tall today, and 1 meter tall tomorrow, all distances are halved and you can't notice. Sure, not with a meter stick. But what about light? A meter can be defined as how much distance light travels in some short amount of time. If lengths halved, wouldn't speed of light suddenly double (i.e. it can now cover twice the distance in same amount of time)?

[quote name='EnigmaticProgrammer' timestamp='1335120187' post='4933835']
EDIT: Appears that I am not the first to think this: martinelli.org/rexpansion

One thing strikes me as odd in that article. If we are 2 meters tall today, and 1 meter tall tomorrow, all distances are halved and you can't notice. Sure, not with a meter stick. But what about light? A meter can be defined as how much distance light travels in some short amount of time. If lengths halved, wouldn't speed of light suddenly double (i.e. it can now cover twice the distance in same amount of time)?
[/quote]
I'm glad you brought that up! I'm not sure if the guy who wrote that article clarified it but I think the speed of light is not the results of higgs bosons and it is not a universal constant. I think the speed of light stems from the fact that a photon is simply the smallest self contained unit of energy in the universe. Why do you think it is that the more energetic a particle is the slower it moves? Energy its self slows time. In fact I think if you click the link at the bottom of that page where it says "Time and Clocks" it will explain this concept.

[quote name='frob' timestamp='1335121580' post='4933844']
Both, it is a matter of perspective. Similarly, your eye moving or is the origin of the universe changing?

Does the universe have an origin (in that sense)?
[/quote]

No I don't think it works like a balloon blowing up. All points were one point before inflation, so that kind of means all points can be considered the origin of the universe

No I don't think it works like a balloon blowing up. All points were one point before inflation, so that kind of means all points can be considered the origin of the universe

That depends on whether you allow an external observer or not. To an observer in the universe, any point could be the origin. To a theoretical external observer it could be a single point.

[quote name='hupsilardee' timestamp='1335445405' post='4935057']
No I don't think it works like a balloon blowing up. All points were one point before inflation, so that kind of means all points can be considered the origin of the universe

That depends on whether you allow an external observer or not. To an observer in the universe, any point could be the origin. To a theoretical external observer it could be a single point.
[/quote]

Sorry yes, that was what I was missing. No external observers allowed (Kind of reversing the strong anthropic principle to an extreme - an observer requires machinery like an eye or a camera, but these things need space to exist in, and space doesn't exist outside the universe)

Interesting. This is making sense.

If we are shrinking, while still able to observe that the universe is expanding, that means we are shrinking at a faster than rate than some other parts of the universe, which means that different parts of the universe are probably shrinking at different rates. We are all being sucked in by tiny black holes spread out everywhere.

And perhaps eventually, in a billion years or so, when all matters have gravitated back into one supermassive blackhole, since energy has been condensed so much, that's when Big Bang will occur?

And since we are shrinking at different rates, it could mean that there's not one Big Bang, but multiple Big Bangs happening at different times and locations in the universe. Even as we speak now, there's probably a spot somehwere in the universe that's experiencing another Big Bang. Of course, we are all somehow affected by the tremendous amount of energy that's released, even though it's X billions light years away.

So a Big Bang is the inverse situation of a black hole that is no longer able to contain all the energy that it has sucked in, so the black hole basically "vomits" all energy that it has sucked in, creating new stars, planets, and everything else. Then the cycle repeats!

If this is the case, we can't use light, as light does not escape black holes, to measure this phenomenon.

This is awesome. I always thought expanding universe, existence of black holes, and big bang don't make any sense. But they all connect together now.

I don't think black holes have a problem with large amounts of energy - there's nothing to say that they would 'vomit' up all their energy. In fact, black holes 'ooze' energy in the form of Hawking radiation, which contravenes your postulation that ALL energy would eventually condense into a supermassive black hole.

If we are shrinking, while still able to observe that the universe is expanding, that means we are shrinking at a faster than rate than some other parts of the universe, which means that different parts of the universe are probably shrinking at different rates. We are all being sucked in by tiny black holes spread out everywhere.

There is no observable difference between the universe expanding and us shrinking. The two are interchangeable.

And perhaps eventually, in a billion years or so, when all matters have gravitated back into one supermassive blackhole, since energy has been condensed so much, that's when Big Bang will occur?[/quote]
What? A billion years? Uh, no. Furthermore, as the universal expansion continues to accelerate matter will not glomp together into black holes, but gravitationally bound objects will continue to drift further and further away from all other gravitationally bound objects. Until at some point in the future, after many billionS of years the only observable object in the night sky will be the milky way galaxy. All others having fallen over the horizon of the observable universe due to the expansion of space BETWEEN them.

So a Big Bang is the inverse situation of a black hole that is no longer able to contain all the energy that it has sucked in, so the black hole basically "vomits" all energy that it has sucked in, creating new stars, planets, and everything else. Then the cycle repeats![/quote]
What? That makes no sense, it also demonstrates a fundamental lack of understanding of black holes based on modern physics. Black holes radiate, we believe, hawking radiation. The rate of emission is INVERSELY PROPORTIONAL to the size of the black hole. Because of this the larger a black hole, the longer it takes to dissipate that energy, inversely: the smaller the black hole the faster it dissipates its energy. Any black hole we can currently observe is far too large to emit sufficient hawking radiation for us to measure its temperature. This is because the universe as a whole (background radiation specifically) is hotter than the hawking radiation the black hole would emit.

We don't entirely understand the mechanics of black holes, it is entirely possible that a black hole could be the spawning ground of new universes, each being a gateway into a new inflationary space. However, there is no means for us to actually tell that until we've resolved the differences between general relativity and quantum mechanics. Specifically, until we have a working set theories for quantum gravity.

But maybe we are not shrinking, and the universe is not expanding. Maybe the speed of light is decreasing over time. If this process was sufficiently slow (millions of years), we wouldn't be able to tell. The static universe would appear to be expanding. In fact, it could even expand, but slower than we believe...

Though this is most probably not the case, light could very well decelerate over time, much like an arrow does due to air resistance. Of course most of the universe is "mostly empty", so it would be hard to argue what's causing light to decelerate, but hey... only because we can't see anything does not necessarily mean there is nothing.

What if the passing of time accelerated over time? Would we equally see the universe expanding? I think we should, as more time passes for the same distance travelled -- though time affecting time is truly a bit esoteric.

There is no observable difference between the universe expanding and us shrinking. The two are interchangeable.

I disagree. Our current theory requires dark energy in order to inflate space. If matter is stinking as a result of gravity then we can contribute the expansion of space to gravity alone without needing a new type of hypothetical particle.

But maybe we are not shrinking, and the universe is not expanding. Maybe the speed of light is decreasing over time. If this process was sufficiently slow (millions of years), we wouldn't be able to tell. The static universe would appear to be expanding. In fact, it could even expand, but slower than we believe...

I don't think that's true. If SoL would decrease, it would mean that it decreases (along with the max speed of information transfer) for everything, so the material of the abservers too. So I don't think we could experience any shrinking/expanding, as we would "expand/shrink" with the universe (if we define shrinkingh/expansion in relation with SoL)

If you mean that the Speed of Light and the Lorentz' c are not the same, than maybe we'd experience the expansion. But i don't know how would the doppler-effect be affected, my knowledge of special relativity (um... maybe the doppler stuff is described with general relativity?) is rather dusty and was quite sloppy anyway.

(To be honest, I never got to understand the doppler effect with the constant SoL thing...)

There is no observable difference between the universe expanding and us shrinking. The two are interchangeable.

This.

The erraneous assumption made by people above is that we as humans are shrinking, which would cause the speed of light to change (with relation to us). On the other hand if space itself is stretching, there's absolutely no difference as to whether it is expanding or shrinking as far as the speed of light is concerned.

Incidentally, smarter people have pondered this and turns out the number involved is, in fact, positive*.


* edit: denoting an expanding universe as opposed to a shrinking one.

(To be honest, I never got to understand the doppler effect with the constant SoL thing...)

It's actually quite simple. Think of a moving car - when shining a light (IR, visible, whatnot) at the car, as it is reflected back, it becomes shifted in spectrum towards either "blue" or "red". This is because light behaves like a wave that can be stretched or shrunk in frequency. In very simple terms "as a photon is not a point particle, it takes a certain amount of time to bounce back - if the object is moving away, the photon takes longer to bounce back, becoming stretched and vice versa.".

The same principle applies on a cosmological scale - if a star is moving away from us, the light emitted from it is shifted due to the light source's movement - if it's moving away, the frequency is stretched; if it's moving towards us, the frequency is shrunk while the speed of light remains constant. The trouble here is that we can't use a spotlight to gauge a star's distance, so type Ia supernovae are used instead, which are known to have a very specific range of luminosity and hue. As such this luminosity is primarily dependent on distance while the size of the star (and the hue of the supernova) is known to be roughly constant. By comparing type Ia supernovae at different distances it is possible to plot out a relative scale of hues, which implies that galaxies that are further away emit light that is shifted increasingly towards red and are hence moving away from us faster than the ones that are closer to us. Hence, the logical conclusion is that space must be expanding.

Here the balloon equivalence mentioned above is actually a fairly good one aside from the fact that as far as we know space has zero curvature (it's flat), although that might be due to the fact that we can see such a small portion of space that it's impossible for use to properly detect curvature.

The same principle applies on a cosmological scale - if a star is moving away from us, the light emitted from it is shifted due to the light source's movement - if it's moving away, the frequency is stretched; if it's moving towards us, the frequency is shrunk while the speed of light remains constant. The trouble here is that we can't use a spotlight to gauge a star's distance, so type Ia supernovae are used instead, which are known to have a very specific range of luminosity and hue. As such this luminosity is primarily dependent on distance while the size of the star (and the hue of the supernova) is known to be roughly constant. By comparing type Ia supernovae at different distances it is possible to plot out a relative scale of hues, which implies that galaxies that are further away emit light that is shifted increasingly towards red and are hence moving away from us faster than the ones that are closer to us. Hence, the logical conclusion is that space must be expanding.

Furthermore, since we already knew that space was expanding (due to Edwin Hubble), we were then able to take our knowledge and apply it to see if we could calculate the rate at which the expansion of the universe was slowing down (due to gravitational effects). The answer was that objects that were further from us than nearer ones were red shifted FURTHER than they should have been. Thus we were able to conclude that not only was the universe expanding, but it was expanding at an increasing rate.

Here the balloon equivalence mentioned above is actually a fairly good one aside from the fact that as far as we know space has zero curvature (it's flat), although that might be due to the fact that we can see such a small portion of space that it's impossible for use to properly detect curvature.

Indeed, or it could be that space takes on a manifold of different geometries in areas outside of our current observable universe, depending on the gravitational gradient, matter amounts, dark matter, energy, etc. You can imagine a universe in which some areas are locally flat, others are hyperbolic and still others are approaching spherical (other areas could be spherical in fact, but the result would appear as though it were a black hole of significant size, if its observable at all).

[quote name='irreversible' timestamp='1335706891' post='4935823']
The same principle applies on a cosmological scale - if a star is moving away from us, the light emitted from it is shifted due to the light source's movement - if it's moving away, the frequency is stretched; if it's moving towards us, the frequency is shrunk while the speed of light remains constant. The trouble here is that we can't use a spotlight to gauge a star's distance, so type Ia supernovae are used instead, which are known to have a very specific range of luminosity and hue. As such this luminosity is primarily dependent on distance while the size of the star (and the hue of the supernova) is known to be roughly constant. By comparing type Ia supernovae at different distances it is possible to plot out a relative scale of hues, which implies that galaxies that are further away emit light that is shifted increasingly towards red and are hence moving away from us faster than the ones that are closer to us. Hence, the logical conclusion is that space must be expanding.

Furthermore, since we already knew that space was expanding (due to Edwin Hubble), we were then able to take our knowledge and apply it to see if we could calculate the rate at which the expansion of the universe was slowing down (due to gravitational effects). The answer was that objects that were further from us than nearer ones were red shifted FURTHER than they should have been. Thus we were able to conclude that not only was the universe expanding, but it was expanding at an increasing rate.
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Just give the idea that we are shrinking a bit more thought. When an object falls toward a planet its speed keeps increasing unless it hits wind resistance. Now imagine billions of points in space all falling in on each other without any wind resistance. They would endlessly speed up and clumps of points in the distance would appear to be getting further away at a faster and faster rate.

[quote name='Washu' timestamp='1335721039' post='4935851']
[quote name='irreversible' timestamp='1335706891' post='4935823']
The same principle applies on a cosmological scale - if a star is moving away from us, the light emitted from it is shifted due to the light source's movement - if it's moving away, the frequency is stretched; if it's moving towards us, the frequency is shrunk while the speed of light remains constant. The trouble here is that we can't use a spotlight to gauge a star's distance, so type Ia supernovae are used instead, which are known to have a very specific range of luminosity and hue. As such this luminosity is primarily dependent on distance while the size of the star (and the hue of the supernova) is known to be roughly constant. By comparing type Ia supernovae at different distances it is possible to plot out a relative scale of hues, which implies that galaxies that are further away emit light that is shifted increasingly towards red and are hence moving away from us faster than the ones that are closer to us. Hence, the logical conclusion is that space must be expanding.

Furthermore, since we already knew that space was expanding (due to Edwin Hubble), we were then able to take our knowledge and apply it to see if we could calculate the rate at which the expansion of the universe was slowing down (due to gravitational effects). The answer was that objects that were further from us than nearer ones were red shifted FURTHER than they should have been. Thus we were able to conclude that not only was the universe expanding, but it was expanding at an increasing rate.
[/quote]

Just give the idea that we are shrinking a bit more thought. When an object falls toward a planet its speed keeps increasing unless it hits wind resistance. Now imagine billions of points in space all falling in on each other without any wind resistance. They would endlessly speed up and clumps of points in the distance would appear to be getting further away at a faster and faster rate.
[/quote]

A generally fine argument and while on the surface expansion and collapse might seem indistinguishable, there are still "telltale" properties of the universe that defy this hypothesis. The most effective one I can think of right off the bat is the arrow of time.

In a nutshell the principle behind the arrow of time is entropy (the first law of thermodynamics), which suggests that the universe is forever moving towards a state of increasing disorder/entropy. While there may be no actual known reason as to why time flows in one direction or another, or even solid proof that we can recognize the flow of time based on its directionality, it seems obvious that time is in fact flowing forward. This is a sign as indicated by causality and our perception of causality: things that cause other things to happen do, in fact, happen before things that depend on them.

While the laws of physics are NOT time-variant (that is, the laws of physics actually can and do apply both in a forward and reverse direction of time - eg both a dropping egg shattering and a shattered egg flying up to your hand un-breaking are allowed by the laws of physics, including quantum physics), our existence is, at least for now, bound by a forward motion of time. The only case this can be wrong is if things "are meant" to happen the other way around and we just don't know it and what we perceive as forward motion and causality are actually the reverse. If you want to tackle this one, go ahead - I'll pass

Note that while the laws of thermodynamics really may be wrong at the end of the day (!), they have never been so far and saliently support (read: require) an expanding universe as opposed to a forward arrow of time moving towards decreased entropy.



TO RECAP: a shrinking universe moving forward in time (towards increased entropy) implies that either the laws of thermodynamics (that is, the first one) are wrong and the universe had to start out in a state of maximum disorder. Moreover, the assumed arrow of reversed time that would occur with the big crunch would actually be the forward direction (which is, according to present science, not impossible as there is no one reason as to why the arrow of time flows in a particular direction (or that it flows at all)). The likelier solution, however, (I think Okkam's razor was referenced above) is the case that the universe is in fact expanding and the arrow of time is pointing forward.

Note how there is no one single answer at this time (which is why it's impossible to completely disprove the idea of a shrinking universe) as ultimately the jury really is out on this one (with M-theory being our best bet at tackling this problem) - however, entropy and the arrow of time do make a more than compelling case against a shrinking universe.*


* for further reading or if you're even more interested about this.

[quote name='EnigmaticProgrammer' timestamp='1335722049' post='4935858']
[quote name='Washu' timestamp='1335721039' post='4935851']
[quote name='irreversible' timestamp='1335706891' post='4935823']
The same principle applies on a cosmological scale - if a star is moving away from us, the light emitted from it is shifted due to the light source's movement - if it's moving away, the frequency is stretched; if it's moving towards us, the frequency is shrunk while the speed of light remains constant. The trouble here is that we can't use a spotlight to gauge a star's distance, so type Ia supernovae are used instead, which are known to have a very specific range of luminosity and hue. As such this luminosity is primarily dependent on distance while the size of the star (and the hue of the supernova) is known to be roughly constant. By comparing type Ia supernovae at different distances it is possible to plot out a relative scale of hues, which implies that galaxies that are further away emit light that is shifted increasingly towards red and are hence moving away from us faster than the ones that are closer to us. Hence, the logical conclusion is that space must be expanding.

Furthermore, since we already knew that space was expanding (due to Edwin Hubble), we were then able to take our knowledge and apply it to see if we could calculate the rate at which the expansion of the universe was slowing down (due to gravitational effects). The answer was that objects that were further from us than nearer ones were red shifted FURTHER than they should have been. Thus we were able to conclude that not only was the universe expanding, but it was expanding at an increasing rate.
[/quote]

Just give the idea that we are shrinking a bit more thought. When an object falls toward a planet its speed keeps increasing unless it hits wind resistance. Now imagine billions of points in space all falling in on each other without any wind resistance. They would endlessly speed up and clumps of points in the distance would appear to be getting further away at a faster and faster rate.
[/quote]

A generally fine argument and while on the surface expansion and collapse might seem indistinguishable, there are still "telltale" properties of the universe that defy this hypothesis. The most effective one I can think of right off the bat is the arrow of time.

In a nutshell the principle behind the arrow of time is entropy (the first law of thermodynamics), which suggests that the universe is forever moving towards a state of increasing disorder/entropy. While there may be no actual known reason as to why time flows in one direction or another, or even solid proof that we can recognize the flow of time based on its directionality, it seems obvious that time is in fact flowing forward. This is a sign as indicated by causality and our perception of causality: things that cause other things to happen do, in fact, happen before things that depend on them.

While the laws of physics are NOT time-variant (that is, the laws of physics actually can and do apply both in a forward and reverse direction of time - eg both a dropping egg shattering and a shattered egg flying up to your hand un-breaking are allowed by the laws of physics, including quantum physics), our existence is, at least for now, bound by a forward motion of time. The only case this can be wrong is if things "are meant" to happen the other way around and we just don't know it and what we perceive as forward motion and causality are actually the reverse. If you want to tackle this one, go ahead - I'll pass

Note that while the laws of thermodynamics really may be wrong at the end of the day (!), they have never been so far and saliently support (read: require) an expanding universe as opposed to a forward arrow of time moving towards decreased entropy.



TO RECAP: a shrinking universe moving forward in time (towards increased entropy) implies that either the laws of thermodynamics (that is, the first one) are wrong and the universe had to start out in a state of maximum disorder. Moreover, the assumed arrow of reversed time that would occur with the big crunch would actually be the forward direction (which is, according to present science, not impossible as there is no one reason as to why the arrow of time flows in a particular direction (or that it flows at all)). The likelier solution, however, (I think Okkam's razor was referenced above) is the case that the universe is in fact expanding and the arrow of time is pointing forward.

Note how there is no one single answer at this time (which is why it's impossible to completely disprove the idea of a shrinking universe) as ultimately the jury really is out on this one (with M-theory being our best bet at tackling this problem) - however, entropy and the arrow of time do make a more than compelling case against a shrinking universe.*


* for further reading or if you're even more interested about this.
[/quote]

Again I disagree. The universe started out very hot (entropy) and over time it has lost entropy. In the future the universe will become more ordered. The reason for this is a concept known as emergence. Please watch this video for a better understanding. Evidence for emergence can be seen all around us but the increase in entropy as time moves forward has no evidence.

I like to think of the universe as a snowflake:


Each new branch is a new universe formed through a black hole. As time moves forward entropy is lost and order is increased. Eventually order will become so great that there is nothing but black holes in the universe and these black holes will interact with each other to form a much larger and more complex system. This process of complexification likely continues in to infinity.

Also the way you are looking at entropy is wrong. Entropy is not disorder.