Happy Atheist Forum

I've looked and haven't been able to find an answer to this. But, is there empty space outside the farthest galaxies in the universe? If so how much of it?

This is the edge of space question isn't it? Hubble discovered the universal red shift (its all moving away from us;fast!). There is the microwave radiation (residue of the hot start) and expansion (the reason the sky is dark at night, even when everywhere you look you see a star or galaxy). So if one posits a start and expansion there is nothing outside the universe as the universe encompasses all reality, the universe is expanding but not into something as it comprises all of something in the first place.

Also you have to consider that when you look further away you look further back in time. The earliest galaxies will be found a long way away and long dead by now but there would be a gap between them and the 'edge' of reality but the difference would remain proportionately identical over time.

Quote from: "Tank"So if one posits a start and expansion there is nothing outside the universe as the universe encompasses all reality, the universe is expanding but not into something as it comprises all of something in the first place.

Negative.  There is nothing that says there can't be something outside of our universe.  What that something is is unknown, but there is no way to tell.

Quote from: "PoopShoot"

Quote from: "Tank"So if one posits a start and expansion there is nothing outside the universe as the universe encompasses all reality, the universe is expanding but not into something as it comprises all of something in the first place.

Negative.  There is nothing that says there can't be something outside of our universe.  What that something is is unknown, but there is no way to tell.

Quote from: "PoopShoot"

Quote from: "Tank"So if one posits a start and expansion there is nothing outside the universe as the universe encompasses all reality, the universe is expanding but not into something as it comprises all of something in the first place.

Negative.  There is nothing that says there can't be something outside of our universe.  What that something is is unknown, but there is no way to tell.

I agree with PS, There could be universes popping in and out of existence like bubbles. All with different laws, and some not able to sustain itself and some like our universe which can.

Are you not open to the idea of outside universes Tank?

Okay, let me go more in depth to my question, I'm sorry I didn't go in enough detail. Is there any "nothing" outside our farthest galaxies? If you watch Lawerence Krauss' "A universe from nothing" he explains nothing very well, and how nothing, really isn't nothing. So, if there is, how much or how far of nothing is there? (Nothing as in dark energy and dark matter)

Quote from: "Tank"

Quote from: "PoopShoot"

Quote from: "Tank"So if one posits a start and expansion there is nothing outside the universe as the universe encompasses all reality, the universe is expanding but not into something as it comprises all of something in the first place.

Negative.  There is nothing that says there can't be something outside of our universe.  What that something is is unknown, but there is no way to tell.

"Universe" is a term that does imply containment of all existence, but to make the argument you are (by virtue of your underlining), you must assume that we can see that there is nothing beyond space.  It is possible that there are other universes, or that we are in a layered universe wherein we can only see our own layer, or something similar to that.  It is possible that the term "universe" is technically incorrect.

Outside of everything there is nothing.

Quote from: "Will"Outside of everything there is nothing.

Of course, but what is outside of the visible universe?

Quote from: "Will"Outside of everything there is nothing.

How do we discern "everything"? And how do we discern "nothing"?

When I check back here in a few hours, I expect you guys to have this thing sorted.

Quote from: "The Magic Pudding"When I check back here in a few hours, I expect you guys to have this thing sorted.

Better cross your fingers.

Quote from: "tymygy"

Quote from: "The Magic Pudding"When I check back here in a few hours, I expect you guys to have this thing sorted.

Better cross your fingers.

and hold your breath.

I had a really cool discussion with my son about this today, discussing the foam idea, and also the idea of nested universes.  He really tickles me when he thinks about this sort of stuff.

Quote from: "Thumpalumpacus"I had a really cool discussion with my son about this today, discussing the foam idea, and also the idea of nested universes.  He really tickles me when he thinks about this sort of stuff.

It's truly a fascinating concept isn't it?

It makes me feel so insignificant, and that everything I do is so small and meaningless compared to the big picture, is quite humbling.  

Correct me if I'm wrong here but aren't the Universe and the Observable Universe two seperate things in terms of being able to test and observe that is? As in we can't actually observe all the universe because it's constantly expanding and we are limited to light speed observations of what was but not what is.

Quote from: "PoopShoot"Of course, but what is outside of the visible universe?

Outside the visible universe? More universe! There's a lot we can't yet see.

Quote from: "tymygy"How do we discern "everything"? And how do we discern "nothing"?

Everything is all spacetime. Nothing is a lack of spacetime.

Quote from: "Will"Everything is all spacetime. Nothing is a lack of spacetime.

Are you telling me that every time I run out of underpants its because of a lack of spacetime? I'm telling you it's because I didn't do the laundry.

Quote from: "AlP"

Quote from: "Will"Everything is all spacetime. Nothing is a lack of spacetime.

Are you telling me that every time I run out of underpants its because of a lack of spacetime? I'm telling you it's because I didn't do the laundry.

But your underwear still exist...in the dirty laundry. Thats totaly diferent from nothing/non-existance/lack of space time. I'm telling you if somehow your underwear lacked or ceased to have space time they would not and by deffinition could not exist.

Quote from: "Tanker"Correct me if I'm wrong here but aren't the Universe and the Observable Universe two seperate things in terms of being able to test and observe that is? As in we can't actually observe all the universe because it's constantly expanding and we are limited to light speed observations of what was but not what is.

Do you mean we don't know whats really going on in the universe because we're taking pictures as it looked billions of years ago?

Quote from: "Will"

Quote from: "PoopShoot"Of course, but what is outside of the visible universe?

Outside the visible universe? More universe! There's a lot we can't yet see.

Right.  Let's put it a different way, mr. literal.  If you were to teleport to the edge of space, you know, that place with all the blue bubbles in Star Trek, anyway, go there, what's past it?  What evidence is there that our little expanding bubble of spacetime is the ONLY expanding bubble of spacetime?

Quote from: "Will"Everything is all spacetime. Nothing is a lack of spacetime.

does that include parallel universes?

And nothing is not really nothing, like I said before, go watch Lawerence Krauss' video "A Universe from Nothing", wonderful explanations on what "nothing" really is.

Quote from: "PoopShoot"Right.  Let's put it a different way, mr. literal.  If you were to teleport to the edge of space, you know, that place with all the blue bubbles in Star Trek, anyway, go there, what's past it?  What evidence is there that our little expanding bubble of spacetime is the ONLY expanding bubble of spacetime?

^like.

Quote from: "Tanker"But your underwear still exist...in the dirty laundry.

Oh that's where I put them! I knew philosophy would turn out to be useful for something.

Quote from: "tymygy"

Quote from: "Tanker"Correct me if I'm wrong here but aren't the Universe and the Observable Universe two seperate things in terms of being able to test and observe that is? As in we can't actually observe all the universe because it's constantly expanding and we are limited to light speed observations of what was but not what is.

Do you mean we don't know whats really going on in the universe because we're taking pictures as it looked billions of years ago?

Partialy. The universe is what about 13.7 billion lightyears across? By the time we saw the edge about an aditional 7 billion years would have passed (assuming we're near the center)and the universe would be much larger and the "edge" would no longer be the edge. It's like a never ending game of 'catch up' that we will never win. We can make predictions and educated guesses but we can literaly never see the "edge".

Imagine it like this we have maps of every city but what if acurate maps couldn't be completed and distibuted for at least 100 years after comissioning. While the map would be an acurate depiction of a city 100 years in the past, under this circumstance we would never know how large the city had become because our information would always be hopelessly out of date. We could make predictions about the cities size and growth patterns because we have evidence and records for how a city does grow but we could never 'know' it's actual size or dimensions.

(I know there isn't an "edge" persay just like there isn't a "before" the big bang. However it's alot easier then "the amorpheous limit to space and time as we know them".)

Quote from: "Tanker"(I know there isn't an "edge" persay just like there isn't a "before" the big bang. However it's alot easier then "the amorpheous limit to space and time as we know them".)

If you're pedantic.

Quote from: "AlP"Are you telling me that every time I run out of underpants its because of a lack of spacetime? I'm telling you it's because I didn't do the laundry.

The question seems to be what exists out of what we understand to be the universe. I understand the universe to be spacetime, a thing governed by laws and filled with matter and energy. Based on our current knowledge, everything is within spacetime. Maybe some day we'll discover something else, but for now the best guess would seem to be boxers because briefs are uncomfortable. I think I lost my train of thought there.

Quote from: "PoopShoot"Right.  Let's put it a different way, mr. literal.  If you were to teleport to the edge of space, you know, that place with all the blue bubbles in Star Trek, anyway, go there, what's past it?  What evidence is there that our little expanding bubble of spacetime is the ONLY expanding bubble of spacetime?

Because spacetime is moving right along with matter and energy from what we understand to be the Big Bang. If that's moving right along with the chunks, there's reason to believe the expansion encompasses everything. It's certainly not something we know for sure, but if I'm up on astronomy and physics, it's our best hypothesis at this point.

Quote from: "tymygy"does that include parallel universes?

We know basically nothing about parallel universes. I could only guess as to their nature.

Quote from: "tymygy"And nothing is not really nothing, like I said before, go watch Lawerence Krauss' video "A Universe from Nothing", wonderful explanations on what "nothing" really is.

No, I mean real nothing. A complete lack of anything, not just matter and energy, but physical laws. It's not a place one can visit (as visiting would require space and time), in fact it's probably beyond our current comprehension.

Quote from: "PoopShoot"

Quote from: "Tanker"(I know there isn't an "edge" persay just like there isn't a "before" the big bang. However it's alot easier then "the amorpheous limit to space and time as we know them".)

If you're pedantic.

Shouldn't that be "unless your pedantic"? Lol. It was preemptive self-correcting I was getting flash backs to discussions about the big bang and people correcting me when I say "before" when they know perfectly well what I meant and that I wasn't being literal. So I thought I'd kill the fire before the smoke.

Quote from: "Will"No, I mean real nothing. A complete lack of anything, not just matter and energy, but physical laws. It's not a place one can visit (as visiting would require space and time), in fact it's probably beyond our current comprehension.

I'm not sure I follow.

So, if it requires space and time, its not in our universe. But how can we "nothing" exists?

Your right, the concept of nothing, if it is real, is far surpassing our comprehension because it would be based on zero evidence and assumptions. (Am I wrong?)

And another thing, if nothing exists, does it exist? We can't see it, feel it, hear it, smell it, etc. So its not testable, and will forever remain a mystery.

Quote from: "Tanker"The universe is what about 13.7 billion lightyears across?

Universe Measured: We're 156 Billion Light-years Wide! (http://www.space.com/scienceastronomy/mystery_monday_040524.html)

QuoteIf you've ever wondered how big the universe is, you're not alone. Astronomers have long pondered this, too, and they've had a hard time figuring it out. Now an estimate has been made, and its a whopper.

The universe is at least 156 billion light-years wide.

In the new study, researchers examined primordial radiation imprinted on the cosmos. Among their conclusions is that it is less likely that there is some crazy cosmic "hall of mirrors" that would cause one object to be visible in two locations. And they've ruled out the idea that we could peer deep into space and time and see our own planet in its youth...

Interesting stuff, things are often not what they appear to be!

Quote from: "Tank"

Quote from: "Tanker"The universe is what about 13.7 billion lightyears across?

Universe Measured: We're 156 Billion Light-years Wide! (http://www.space.com/scienceastronomy/mystery_monday_040524.html)

QuoteIf you've ever wondered how big the universe is, you're not alone. Astronomers have long pondered this, too, and they've had a hard time figuring it out. Now an estimate has been made, and its a whopper.

The universe is at least 156 billion light-years wide.

In the new study, researchers examined primordial radiation imprinted on the cosmos. Among their conclusions is that it is less likely that there is some crazy cosmic "hall of mirrors" that would cause one object to be visible in two locations. And they've ruled out the idea that we could peer deep into space and time and see our own planet in its youth...

Interesting stuff, things are often not what they appear to be!

Thanks I think I mixed the age with the size. Lol.

A couple of points:

1. There are two very distinct definitions of the word 'universe'. The first is roughly 'that which arose from the big bang', while the other is 'that which is'. cosmologists often employ the former, but that's largely because they tend to write for people who understand what they're talking about, and of course they're not accustomed to having their words equivocated by propagandists for doctrine in the same way that, for example, evolutionary biologists are. If your question is 'what lies outside that which arose from the big bang (hereinafter referred to as 'the cosmos' for brevity)?' the answer is that we don't know, but we have some good ideas. If the question is actually, 'what is our the cosmos expanding into?' the answer is 'not precisely nothing'. It's as close to 'nothing' as can be actually achieved, but it still isn't precisely nothing, because that's not possible.

2. Our cosmos is thought to be about 96 billion lightyears across (although some sources put this figure considerably higher. I got this figure from Andromeda's Wake, and he generally knows this stuff, so I'll run with it). This figure is arrived at by employing the parameters of the inflationary model, and extrapolating, which does have some problems, not least that the inflationary model suffers from some 'fine-tuning' issues. Note that this 'fine-tuning' is not the same as the idea of fine-tuning employed by cretinists, although they cite the same sources. Again, when a physicist talks about fine-tuning, he's actually talking about the requirement for the values of some parameters or other to fall within a very narrow band if the model is correct. In other words, it's the model that is fine-tuned, not the universe. In this case, certain parameters, such as the rate of inflation, have to fall within a very narrow band of values to overcome the horizon problem, among other things. At this point, it isn't clear that the inflationary model is correct, and it isn't the only game in town. Apart from anything else, it assumes a physical singularity, and it isn't even clear that such an entity is even possible.

3. The observable universe is subject to a light horizon, which means in reality that what we can observe cannot be more than 13.7 billion lightyears away, meaning that the observable universe is actually 27.4 lightyears across. Beyond this horizon is simply more of the same.

4. And this is the really important one. I must have said this at least 3,000 times in the last few years on various rationalist fora, and it can't be said enough, not least because there is an assertion that has been accepted for a long time:

It is far from having been established that time began at the big bang. This assertion again arises from the picture of a physical singularity. The pronouncement came from the work of Hawking and Penrose, when they established that the equations of General Relativity showed that the big bang arose from a singularity (of the physical variety). Given that time slows in the presence of a relativistic mass, then given a large enough mass, time would stand still. There are two major problems with taking this to mean that there was no time before the big bang. The first is that, even if the cosmos arose from a genuine physical singularity, and even if time stopped at the singularity, this in no way validates the claim that there was no time before the singularity, only that the singularity didn't experience it. Given that we have entities within our cosmos that don't experience time, and yet time clearly exists, the fallacy of this line of thought is clear. Secondly, Hawking himself no longer supports that conclusion, and hasn't done since shortly afterwards, since he realised that this conclusion didn't take quantum effects into account.

5. And finally, it needs to be established what a singularity actually is. In physics generally, a singularity is simply an event which our physical theories fail to describe, for one reason or another. In the case of black hole and BB singularities, it is a place that requires both Quantum Mechanics and General Relativity to describe it. Every time that GR and QM have been brought together, the output is infinity, which is a ridiculous answer.

So, to sum up, the big bang was probably not the beginning of time. It was also probably not the beginning of our spatial dimensions, but was more likely an unfolding of them from the dimensional manifold. Until we understand the topography of the dimensional manifold much better than we do, we must be careful of categorical statements, especially categorical statements that stem from science that is thirty years or more out of date. Thirty years is an aeon in theoretical physics.

Quote from: "Tanker"

Quote from: "Tank"

Quote from: "Tanker"The universe is what about 13.7 billion lightyears across?

Universe Measured: We're 156 Billion Light-years Wide! (http://www.space.com/scienceastronomy/mystery_monday_040524.html)

QuoteIf you've ever wondered how big the universe is, you're not alone. Astronomers have long pondered this, too, and they've had a hard time figuring it out. Now an estimate has been made, and its a whopper.

The universe is at least 156 billion light-years wide.

In the new study, researchers examined primordial radiation imprinted on the cosmos. Among their conclusions is that it is less likely that there is some crazy cosmic "hall of mirrors" that would cause one object to be visible in two locations. And they've ruled out the idea that we could peer deep into space and time and see our own planet in its youth...

Interesting stuff, things are often not what they appear to be!

Thanks I think I mixed the age with the size. Lol.

It happens.

And thanks tank, I had heard it was 78 billion light-years. Half way right.  

Quote from: "Tanker"

Quote from: "PoopShoot"

Quote from: "Tanker"(I know there isn't an "edge" persay just like there isn't a "before" the big bang. However it's alot easier then "the amorpheous limit to space and time as we know them".)

If you're pedantic.

Shouldn't that be "unless your pedantic"? Lol. It was preemptive self-correcting I was getting flash backs to discussions about the big bang and people correcting me when I say "before" when they know perfectly well what I meant and that I wasn't being literal. So I thought I'd kill the fire before the smoke.

No.  IF you're pedantic.  People who say there is no before the big bang are pointing out that time is function of space.  While this is true and there can be no time without space, the argument "there can be no before..." ignores the possibility of previous iterations of the universe as well as other means by which events may be separated.  When you're right on a technicality at the expense of the point, you're being pedantic.

I don't think we can make any conclusions at all.  If we go simply by what we can observe, then one can conclude that our universe is a bubble expanding into....something.  The big bang was probably a white hole, or the exhaust of a massive black hole.  Makes me wonder if the super-massive black holes at the center of almost every galaxy are creating universes in other dimensions.  All that matter had to come from somewhere ...

Quote from: "PoopShoot"People who say there is no before the big bang are pointing out that time is function of space.  While this is true and there can be no time without space,

Actually, this isn't true, and they'd be wrong. This is precisely what Einstein taught us. Time is not a function of space, it's an additional dimension, and space and time are facets of the same entity, spacetime.

Quotethe argument "there can be no before..." ignores the possibility of previous iterations of the universe as well as other means by which events may be separated.

This is most definitely true.

QuoteWhen you're right on a technicality at the expense of the point, you're being pedantic.

Indeed, but when the point is wrong due to a misunderstanding of the technicality, pedantry is necessary.

Maybe my logic is wrong, but unless the universe is expanding faster than the speed of light....wouldn't it only be 27.4 billion light years across?

Quote from: "DropLogic"Maybe my logic is wrong, but unless the universe is expanding faster than the speed of light....wouldn't it only be 27.4 billion light years across?

I found this interesting.

http://everyjoe.com/technology/how-can- ... s-old-191/ (http://everyjoe.com/technology/how-can-we-see-galaxies-47-billion-light-years-away-when-the-universe-is-only-13-billion-years-old-191/)

Quote from: "tymygy"

Quote from: "DropLogic"Maybe my logic is wrong, but unless the universe is expanding faster than the speed of light....wouldn't it only be 27.4 billion light years across?

I found this interesting.

http://everyjoe.com/technology/how-can- ... s-old-191/ (http://everyjoe.com/technology/how-can-we-see-galaxies-47-billion-light-years-away-when-the-universe-is-only-13-billion-years-old-191/)

K I still don't understand how they can come to these conclusions.  If every galaxy is moving away from every other galaxy, why do we observe frequent galactic collisions?  Wouldn't all the energy released by pulsars, and quasars have an effect on the surrounding space?  How can we come up with a constant rate of expansion without possibly knowing the external effects that are taking place around the objects we are measuring?  The gravity of another large body changes the speed and rotation of the original body.

Quote from: "DropLogic"Maybe my logic is wrong, but unless the universe is expanding faster than the speed of light....wouldn't it only be 27.4 billion light years across?

The universe is expanding at greater than c. More importantly, during the very early inflationary period, it expanded at considerably greater than c.

Quote from: "DropLogic"K I still don't understand how they can come to these conclusions.  If every galaxy is moving away from every other galaxy, why do we observe frequent galactic collisions?  Wouldn't all the energy released by pulsars, and quasars have an effect on the surrounding space?  How can we come up with a constant rate of expansion without possibly knowing the external effects that are taking place around the objects we are measuring?  The gravity of another large body changes the speed and rotation of the original body.

A couple of things again:

1. Every galaxy is not moving away from every other galaxy. On average, galaxies are receding from each other.
2. The rate of expansion isn't constant. Indeed, that's why dark energy is postulated, to account for the fact that expansion is accelerating.

Quote from: "hackenslash"1. Every galaxy is not moving away from every other galaxy. On average, galaxies are receding from each other.
2. The rate of expansion isn't constant. Indeed, that's why dark energy is postulated, to account for the fact that expansion is accelerating.

1. Clarify please.  To me, both of those mean the same thing.
2. I guess theorizing is the best we can do to ascertain the true size of the universe.  I don't think we're capable of understanding it yet.

Quote from: "DropLogic"

Quote from: "hackenslash"1. Every galaxy is not moving away from every other galaxy. On average, galaxies are receding from each other.
2. The rate of expansion isn't constant. Indeed, that's why dark energy is postulated, to account for the fact that expansion is accelerating.

1. Clarify please.  To me, both of those mean the same thing.
2. I guess theorizing is the best we can do to ascertain the true size of the universe.  I don't think we're capable of understanding it yet.

If 99 Galexies are moving away from each other and 2 are moving towards each other, on average galaxies are moving away from each other. This can be seen in rivers. A rivers average flow is one way but there can be local eddies where water can flow back the other way. Galactic movement is not homogeneous as gravity interactions can sling Galaxies around each other and into each other. Our Galaxy will merge with the Andromada galaxy way into the future. Local behaviour can go against the general trend.

Quote from: "Tank"

Quote from: "DropLogic"

Quote from: "hackenslash"1. Every galaxy is not moving away from every other galaxy. On average, galaxies are receding from each other.
2. The rate of expansion isn't constant. Indeed, that's why dark energy is postulated, to account for the fact that expansion is accelerating.

1. Clarify please.  To me, both of those mean the same thing.
2. I guess theorizing is the best we can do to ascertain the true size of the universe.  I don't think we're capable of understanding it yet.

If 99 Galexies are moving away from each other and 2 are moving towards each other, on average galaxies are moving away from each other. This can be seen in rivers. A rivers average flow is one way but there can be local eddies where water can flow back the other way. Galactic movement is not homogeneous as gravity interactions can sling Galaxies around each other and into each other. Our Galaxy will merge with the Andromada galaxy way into the future. Local behaviour can go against the general trend.

I got 99 problems but a galaxy-crashing-into-my-galaxy-in-my-lifetime ain't one.

Quote from: "DropLogic"I got 99 problems but a galaxy-crashing-into-my-galaxy-in-my-lifetime ain't one.

BEST. POST. EVER.

Quote from: "DropLogic"1. Clarify please.  To me, both of those mean the same thing.

OK, let me explain. On average means 'in general, but not without exception'. This means that, in general, but not without exception, galaxies are receding from each other. Locally, some galaxies are approaching each other. It should be noted also that they aren't actually moving, but that space is expanding between them, giving the illusion of moving. For example, the galaxies that are receding from us aren't moving in relation to us, but Andromeda is actually moving in relation to us, which is why it's headed straight for us. If it were just the expansion of the cosmos involved in the latter, it wouldn't be on a collision course.

Quote2. I guess theorizing is the best we can do to ascertain the true size of the universe.  I don't think we're capable of understanding it yet.

We're capable of understanding a good deal more than you might think, and the size of the universe is pretty well understood to within certain error bars.

Quote from: "hackenslash"It should be noted also that they aren't actually moving, but that space is expanding between them, giving the illusion of moving.

Ok, this makes a lot more sense to me now.  Thank you for explaining.

My back yard is quite dark at night.  Usually at around 2:30 am, i'll go out on the deck with my dogs and stare up for 30-40 minutes; at least when it's a clear night.  The universe overwhelms my feeble mind almost to the point of panic sometimes.  I wish I had a better understanding of why it works this way.  Could you recommend some books for an astronomy/physics/quantum layman?

Quote from: "DropLogic"

Quote from: "hackenslash"It should be noted also that they aren't actually moving, but that space is expanding between them, giving the illusion of moving.

Ok, this makes a lot more sense to me now.  Thank you for explaining.

My back yard is quite dark at night.  Usually at around 2:30 am, i'll go out on the deck with my dogs and stare up for 30-40 minutes; at least when it's a clear night.  The universe overwhelms my feeble mind almost to the point of panic sometimes.  I wish I had a better understanding of why it works this way.  Could you recommend some books for an astronomy/physics/quantum layman?

An excellent place to start would be the book that has recently hit the top of my recommended reading list, the brilliant Why Does E=MC2 by Brian Cox and Jeff Forshaw. Once you've got to grips with that, Hawking's A Brief History Of Time is excellent, although some of it is a little outdated now. Brian Greene's Fabric Of The Cosmos is very good, apart from a very woolly treatment of entropy throughout.

Let me know when you've read those, and I'll recommend some more advanced reading.

Quote from: "hackenslash"It should be noted also that they aren't actually moving, but that space is expanding between them, giving the illusion of moving.

Exactly, Think of it like a balloon being blown up, if you draw small galxies all over the balloon and start blowing it up, they will start growing in distance in relation to each other. The spots didn't move at all, but the space that the spots were occupying became larger therefore making it scale to its size on which it originally started.

Quote from: "tymygy"

Quote from: "hackenslash"It should be noted also that they aren't actually moving, but that space is expanding between them, giving the illusion of moving.

Exactly, Think of it like a balloon being blown up, if you draw small galxies all over the balloon and start blowing it up, they will start growing in distance in relation to each other. The spots didn't move at all, but the space that the spots were occupying became larger therefore making it scale to its size on which it originally started.

If that is true, and galaxies stay constant in size themselves...what about the space within galaxies?  Does that not expand because of gravity's influence?

Quote from: "DropLogic"

Quote from: "tymygy"

Quote from: "hackenslash"It should be noted also that they aren't actually moving, but that space is expanding between them, giving the illusion of moving.

Exactly, Think of it like a balloon being blown up, if you draw small galxies all over the balloon and start blowing it up, they will start growing in distance in relation to each other. The spots didn't move at all, but the space that the spots were occupying became larger therefore making it scale to its size on which it originally started.

If that is true, and galaxies stay constant in size themselves...what about the space within galaxies?  Does that not expand because of gravity's influence?

I never said anything about galaxies having a constant size. I'm talking about all the matter in the galaxy. the galaxy as a whole, doesn't move by itself, the space around it expands.

Gravity is what holds the galaxy together. So no the space inside the galaxy is not affected in the same way.

Quote from: "DropLogic"

Quote from: "tymygy"

Quote from: "hackenslash"It should be noted also that they aren't actually moving, but that space is expanding between them, giving the illusion of moving.

Exactly, Think of it like a balloon being blown up, if you draw small galxies all over the balloon and start blowing it up, they will start growing in distance in relation to each other. The spots didn't move at all, but the space that the spots were occupying became larger therefore making it scale to its size on which it originally started.

If that is true, and galaxies stay constant in size themselves...what about the space within galaxies?  Does that not expand because of gravity's influence?

The same thought crossed my mind regarding the expanding galaxies and went on to consider if I am also expanding? The answer is; apparently not. Trouble is I can't bloody remember where I found out that galaxies don't expand.  

Indeed. Galaxies are gravitationally bound, so are not subject to cosmic expansion.

Quote from: "hackenslash"Indeed. Galaxies are gravitationally bound, so are not subject to cosmic expansion.

That's what they said, I'm glad somebody else knew it!

Quote from: "hackenslash"Indeed. Galaxies are gravitationally bound, so are not subject to cosmic expansion.

Does this not imply that gravity is an aberration and that expansion is the norm? Thus as the universe expands, and the effects of gravity are diluted, that accelerating expansion would be expected to occur?

Quote from: "Tank"

Quote from: "hackenslash"Indeed. Galaxies are gravitationally bound, so are not subject to cosmic expansion.

Does this not imply that gravity is an aberration and that expansion is the norm? Thus as the universe expands, and the effects of gravity are diluted, that accelerating expansion would be expected to occur?

Just because the universe expands does not mean gravity will be "diluted". Gravity depends on the amount of mass of an object(s) and the amount of mass will constitute for the strength of gravity, not the space around it.

Quote from: "tymygy"

Quote from: "Tank"

Quote from: "hackenslash"Indeed. Galaxies are gravitationally bound, so are not subject to cosmic expansion.

Does this not imply that gravity is an aberration and that expansion is the norm? Thus as the universe expands, and the effects of gravity are diluted, that accelerating expansion would be expected to occur?

Just because the universe expands does not mean gravity will be "diluted". Gravity depends on the amount of mass of an object(s) and the amount of mass will constitute for the strength of gravity, not the space around it.

The effect of gravity is expressed as square law, doubling the distance reduces the effect by a factor of four. As the universe is expanding the galaxies are moving apart this will dilute the effect of gravity as the existing mass is expressing gravity within a greater volume.

Kip Thorne's Black Holes and Time Warps is a little more esoteric, but packed with info.

It's outdated now, but I have very fond memories of reading "Coming of Age in the Milky Way" by Timothy Ferris.

Quote from: "Tank"

Quote from: "tymygy"Just because the universe expands does not mean gravity will be "diluted". Gravity depends on the amount of mass of an object(s) and the amount of mass will constitute for the strength of gravity, not the space around it.

The effect of gravity is expressed as square law, doubling the distance reduces the effect by a factor of four. As the universe is expanding the galaxies are moving apart this will dilute the effect of gravity as the existing mass is expressing gravity within a greater volume.

Do you mean from each other? Or the galaxy itself is "unwinding"?

From each other.  Gravity is a spatial sink-hole.

Quote from: "tymygy"

Quote from: "Tank"

Quote from: "tymygy"Just because the universe expands does not mean gravity will be "diluted". Gravity depends on the amount of mass of an object(s) and the amount of mass will constitute for the strength of gravity, not the space around it.

The effect of gravity is expressed as square law, doubling the distance reduces the effect by a factor of four. As the universe is expanding the galaxies are moving apart this will dilute the effect of gravity as the existing mass is expressing gravity within a greater volume.

Do you mean from each other? Or the galaxy itself is "unwinding"?

In general the galaxies are moving apart from each other due to the volumetric expansion of the universe. Any one galaxy my be growing or shrinking within itself based on the matter within it. Any pair or group of Galaxies may be gravitationally bound together and they could be moving in any relative direction to each other.

EDIT

Here are two galaxies doing a gravitational tango

(https://www.happyatheistforum.com/forum/proxy.php?request=http%3A%2F%2Fimgsrc.hubblesite.org%2Fhu%2Fdb%2Fimages%2Fhs-2005-12-a-web_print.jpg&hash=9a9e67307af2bc1c0d45d5aaf672d172b63f2ae8)

These two have been merging for a long time.

(https://www.happyatheistforum.com/forum/proxy.php?request=http%3A%2F%2Fimgsrc.hubblesite.org%2Fhu%2Fdb%2Fimages%2Fhs-2006-46-a-large_web.jpg&hash=20b9ce579a91e968f178ee0c1aeab11ad954115c)

More images at the Hubble site here http://hubblesite.org/gallery/album/galaxy (http://hubblesite.org/gallery/album/galaxy)

Quote from: "Tank"

Quote from: "hackenslash"Indeed. Galaxies are gravitationally bound, so are not subject to cosmic expansion.

Does this not imply that gravity is an aberration and that expansion is the norm? Thus as the universe expands, and the effects of gravity are diluted, that accelerating expansion would be expected to occur?

See my post on dark matter/energy for this. In the absence of a driving force behind expansion, it would be expected to slow under gravity or remain constant as the effects of gravity are reduced by distance. The fact that expansion is actually accelerating tells us something must be going on, because that requires repulsion in some form, which is what dark energy is.

Quote from: "hackenslash"

Quote from: "Tank"

Quote from: "hackenslash"Indeed. Galaxies are gravitationally bound, so are not subject to cosmic expansion.

Does this not imply that gravity is an aberration and that expansion is the norm? Thus as the universe expands, and the effects of gravity are diluted, that accelerating expansion would be expected to occur?

See my post on dark matter/energy for this. In the absence of a driving force behind expansion, it would be expected to slow under gravity or remain constant as the effects of gravity are reduced by distance. The fact that expansion is actually accelerating tells us something must be going on, because that requires repulsion in some form, which is what dark energy is.

So...for a short time after the big bang, space expanded faster than c, but it slowed down?  But is still accelerating?  When did dark matter come into play? Is space still expanding faster than c?

Yes, the universe is expanding at greater than c, because the expansion is not subject to that limitation. It isn't actually travelling, in the same way that the galaxies receding from us aren't travelling. The recession is a result of the expansion of space, and no actual travel is occuring.

Dark matter has always been in play. It's useful to know what dark matter actually is, which you can find in my post about gravity (http://www.happyatheistforum.com/viewtopic.php?p=78541#p78541).

As for the bit about the early expansion of the cosmos, it is necessary to deal with what is known as the 'inflaton' field, which would require quite a long essay. This is actually one of the things that Brian Greene deals with really well in Fabric of the Cosmos, so worth a read just for that.