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Author Topic:   How big is the Universe?
DevilsAdvocate
Member (Idle past 3101 days)
Posts: 1548
Joined: 06-05-2008


(2)
Message 16 of 39 (531496)
10-18-2009 8:30 AM
Reply to: Message 14 by tuffers
10-17-2009 12:38 PM


A good book to help understand the concept of spacetime
Tuffers writes:
es, I understand the idea of dots on a balloon (or raisins in a cake), although to my mind the dots are moving, because they are moving apart from each other as a consequence of the balloon enlarging. In other words, they are not moving under their own steam but they are hitching a ride on something else that's moving (the surface of the balloon in this case). That's why I still find it hard to get my head around the concept.
Actually galaxies also do move in regards to local gravitational forces as well, which is why you see some close by galaxies like Andromeda that are blue shift rather than red shifted. The local gravitational forces between our Milky Way and Andromeda are greater than the expansion forces of the expanding universe. However, this only works locally. The further we go out the faster the universe is expanding away from us. Like the balloon analogy if you put two dots really close to each they will not separate as much as if you put them on opposite sides of the balloon.
The 2 dimensional skin of the balloon in this analogy represents the 4 dimensions of spacetime itself in which everything in our universe resides. That is probably what is hanging you up. You cannot see, touch, feel, or taste the 4 dimensions of spacetime so it is hard for you to conceptualize. However we can detect it through the behavior or objects in space; specifically, the gravitational effects (relativistic effects such as rotating frames of reference, time dilation, relavistic dynamics, etc) of objects upon other objects in space. This is the whole idea behind the Theory of Relativity (both Special and General) proposed by Albert Einstein.
A good book to read that might shed some light on the matter for the average layman is 'The Fabric of the Cosmos: Space, Time, and the Texture of Reality' by Physicist Brian Greene.
Edited by DevilsAdvocate, : No reason given.
Edited by DevilsAdvocate, : correct misspellings and grammer
Edited by DevilsAdvocate, : No reason given.

One of the saddest lessons of history is this: If we've been bamboozled long enough, we tend to reject any evidence of the bamboozle. We're no longer interested in finding out the truth. The bamboozle has captured us. It is simply too painful to acknowledge -- even to ourselves -- that we've been so credulous. - Carl Sagan, The Fine Art of Baloney Detection
"You can't convince a believer of anything; for their belief is not based on evidence, it's based on a deep seated need to believe." - Carl Sagan
"It is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring." - Carl Sagan, The Demon-Haunted World

This message is a reply to:
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Stile
Member
Posts: 4295
From: Ontario, Canada
Joined: 12-02-2004


(1)
Message 17 of 39 (531661)
10-19-2009 9:32 AM
Reply to: Message 12 by Izanagi
10-17-2009 2:49 AM


Re: Warping Space Travel
Izanagi writes:
Don't give up hope yet, Stiles! You may yet get to meet the blue-skinned alien of your dreams!
Ahh... no worries. The only thing that can ever kill hope, is a lack of imagination. And the only thing that kills imagination is a lack of beer!
Didn't you ever see The Neverending Story?
For those of you who have seen it, this was news to me:
quote:
As of June 2009, plans for a new movie adaptation of the book have been announced, although only at the very earliest stages of development. No writer, director, or cast have been decided upon yet.

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 Message 12 by Izanagi, posted 10-17-2009 2:49 AM Izanagi has not replied

  
Briterican
Member (Idle past 3949 days)
Posts: 340
Joined: 05-29-2008


(1)
Message 18 of 39 (532301)
10-22-2009 2:31 PM
Reply to: Message 3 by Dr Jack
10-16-2009 6:48 AM


Fade out
Mr Jack Writes
The expansion of the universe is not primarily due to movement, but to the expansion of space itself. This expansion is not limited by the speed of light.
A fascinating implication of this is that the more distant galaxies which would appear to be receding from us at a speed in excess of the speed of light would eventually fade from observation, and the logical extension of this is that there are presently galaxies that we cannot (nor will we ever) be able to see, because the light travelling from them cannot keep up with the expansion of space and will thus never reach us.

This message is a reply to:
 Message 3 by Dr Jack, posted 10-16-2009 6:48 AM Dr Jack has not replied

Replies to this message:
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cavediver
Member (Idle past 3644 days)
Posts: 4129
From: UK
Joined: 06-16-2005


(1)
Message 19 of 39 (532303)
10-22-2009 2:56 PM
Reply to: Message 18 by Briterican
10-22-2009 2:31 PM


Re: Fade out
there are presently galaxies that we cannot (nor will we ever) be able to see
Very true - in fact, those galaxies that we can see almost certainly represent only a miniscule fraction of the total number of galaxies in existence...

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Perdition
Member (Idle past 3238 days)
Posts: 1593
From: Wisconsin
Joined: 05-15-2003


(1)
Message 20 of 39 (532305)
10-22-2009 2:59 PM
Reply to: Message 18 by Briterican
10-22-2009 2:31 PM


Re: Fade out
A fascinating implication of this is that the more distant galaxies which would appear to be receding from us at a speed in excess of the speed of light would eventually fade from observation
In fact, as far as I know, this is one of the side effects of the heat death of the universe as well. Everything expands to the point that we can only see the local group, and even that could be pulled apart and/or merge, a la the Milky Way and Andromeda.
Suffice to say, if you were to live for billions of years, you'd find yourself stuck between nothing and a dark place.

This message is a reply to:
 Message 18 by Briterican, posted 10-22-2009 2:31 PM Briterican has not replied

  
Buzsaw
Inactive Member


Message 21 of 39 (535607)
11-17-2009 12:05 AM


Imported Universe Response To Onifre
In Msg 318,, of the Is It Science forum, thread; Faith vs Skepticism - Why faith, Onifre posted the following quote. Since I figured a response would lead off topic to that thread, I'm importing the message here for my response since that relates more to this topic.
onifre writes:
There is a confusion in certain terms; spacetime is finite, but not the universe, it has never been shown to be so. There was never a point when there was nothing and then suddenly something, this is a religious concept that is not grounded in evidence. This has been ICANT's problem in understanding the model of the BB and origin.
To say there is an outside to the universe, would mean there is space outside the universe (in some form), and thus would still be part of our universe, since our universe represents all of existence.
To ponder any other domain - other than reality and existence - is purley imaginative, and sounds a lot like special pleading
Onifre, I deduce the following from your message:
1. "...our universe represents all of existence."
2. The universe is not finite.
3. Spacetime is finite.
4. Spacetime exists, therefore finite spacetime is within the universe which is not finite.
5. As per the above, spacetime would have an outside of but the universe no outside of.
Also this question: Was the expansion the expansion of spacetime?

BUZSAW B 4 U 2 C Y BUZ SAW.
The immeasurable present eternally extends the infinite past and infinitely consumes the eternal future.

Replies to this message:
 Message 22 by onifre, posted 11-17-2009 7:26 AM Buzsaw has replied

  
onifre
Member (Idle past 2951 days)
Posts: 4854
From: Dark Side of the Moon
Joined: 02-20-2008


(1)
Message 22 of 39 (535654)
11-17-2009 7:26 AM
Reply to: Message 21 by Buzsaw
11-17-2009 12:05 AM


Re: Imported Universe Response To Onifre
Hi Buz,
1. "...our universe represents all of existence."
2. The universe is not finite.
3. Spacetime is finite.
4. Spacetime exists, therefore finite spacetime is within the universe which is not finite.
5. As per the above, spacetime would have an outside of but the universe no outside of.
Also this question: Was the expansion the expansion of spacetime?
There is no outside of spacetime either, I didn't mean to lead you to that opinion.
What is meant by spacetime being finite is that it had a point of origin, the BB 13.7 bya. However, it didn't come from nothing. What existed before that doesn't operated under the same space and time dimensions that we experience, so it makes no sense to say when that 'started', the universe just is.
There is no outside of it, it is exitence.
And yes, spacetime is expanding, but it can equally be said that the universe is expanding because spacetime represents the universe ever since 13.7 bya.
- Oni

This message is a reply to:
 Message 21 by Buzsaw, posted 11-17-2009 12:05 AM Buzsaw has replied

Replies to this message:
 Message 23 by Buzsaw, posted 11-17-2009 9:43 AM onifre has replied

  
Buzsaw
Inactive Member


Message 23 of 39 (535667)
11-17-2009 9:43 AM
Reply to: Message 22 by onifre
11-17-2009 7:26 AM


Re: Imported Universe Response To Onifre
onifre writes:
There is no outside of spacetime either, I didn't mean to lead you to that opinion.
You haven't led me to that opinion. That was the deduction which your statements conveyed.
onifre writes:
What is meant by spacetime being finite is that it had a point of origin, the BB 13.7 bya. However, it didn't come from nothing. What existed before that doesn't operated under the same space and time dimensions that we experience, so it makes no sense to say when that 'started', the universe just is.
There is no outside of it, it is exitence.
If the universe just is and just was, having existed under different space and time dimensions, the Buzsaw unbounded space eternal universe hypothesis is beginning to look more scientific. I like that.
Now, if we can just accept the possibility that God just (eternally) was, just is, and just (eternally) will be, perhaps creationists and secularists will begin to tolerate one another in a more congenial manner here at EvC.
onifre writes:
And yes, spacetime is expanding, but it can equally be said that the universe is expanding because spacetime represents the universe ever since 13.7 bya.
Deduction so far, as per your statements:
1. The universe is not finite and existed, having had non-finite existing space, non-finite existing time and no outside of (unbounded).
2. Spacetime is a finite period of time when the universeexisting space and time, previously having existing different non-finite time and dimension began to expand, for no explicable reason.
3. Since spacetime, which represents the universe began expanding as a submicroscopic area the not finite universe, having existing space and time was sub-microscopic dimensionally at the time of the beginning of expansion.
4. The not finite universe allegedly became inexplicably finite when the expansion began.
5. Contradiction:
a. The universe is not finite.
b. Spacetime is finite.
c. Existing finite expanding spacetime is the existing not finite (abe: spacetime) universe.
Edited by Buzsaw, : as noted
Edited by Buzsaw, : fix previous edit.

BUZSAW B 4 U 2 C Y BUZ SAW.
The immeasurable present eternally extends the infinite past and infinitely consumes the eternal future.

This message is a reply to:
 Message 22 by onifre, posted 11-17-2009 7:26 AM onifre has replied

Replies to this message:
 Message 24 by greyseal, posted 11-17-2009 10:57 AM Buzsaw has replied
 Message 25 by onifre, posted 11-17-2009 11:13 AM Buzsaw has replied

  
greyseal
Member (Idle past 3862 days)
Posts: 464
Joined: 08-11-2009


(1)
Message 24 of 39 (535679)
11-17-2009 10:57 AM
Reply to: Message 23 by Buzsaw
11-17-2009 9:43 AM


Re: Imported Universe Response To Onifre
buzsaw writes:
onifre writes:
There is no outside of spacetime either, I didn't mean to lead you to that opinion.
You haven't led me to that opinion. That was the deduction which your statements conveyed.
no, you misunderstand what onifre meant by "finite". He meant finite as in "had a beginning", not as in "it has an edge".
If the universe just is and just was, having existed under different space and time dimensions, the Buzsaw unbounded space eternal universe hypothesis is beginning to look more scientific. I like that.
the universe IS - I'm not sure about the "just" part. It has been since approximately 13.7 billion years ago.
"before" and "outside" are words that don't work so very well when you attempt to apply them to the universe.
I could be wrong, but from what I understand the agreement is that now it's here it could be eternal, and now it's here it is unbounded and infinite in extent and has been for all of it's existence.

This message is a reply to:
 Message 23 by Buzsaw, posted 11-17-2009 9:43 AM Buzsaw has replied

Replies to this message:
 Message 26 by Buzsaw, posted 11-17-2009 11:49 AM greyseal has not replied

  
onifre
Member (Idle past 2951 days)
Posts: 4854
From: Dark Side of the Moon
Joined: 02-20-2008


(2)
Message 25 of 39 (535684)
11-17-2009 11:13 AM
Reply to: Message 23 by Buzsaw
11-17-2009 9:43 AM


Re: Imported Universe Response To Onifre
Hi Buz,
You haven't led me to that opinion. That was the deduction which your statements conveyed.
Fair enough, just know that that wasn't what I was trying to convey.
If the universe just is and just was, having existed under different space and time dimensions,
No, just existed; no space or time.
the Buzsaw unbounded space eternal universe hypothesis is beginning to look more scientific. I like that.
Similar to Hawking's No-Boundary universe? - Me thinks the gentleman in the wheelchair worked out the math before you, Buz.
Now, if we can just accept the possibility that God just (eternally) was, just is, and just (eternally) will be, perhaps creationists and secularists will begin to tolerate one another in a more congenial manner here at EvC.
Why go the extra step? Its suffice to say the universe is; there is no need to add to the equation your particular mythical entity - however, if it makes you personally feel better, then postulate away ... just don't expect people to take you on faith.
1. The universe is not finite and existed, having had non-finite existing space, non-finite existing time and no outside of (unbounded).
If this is in reference to Hawking's no-boundary universe, its size (as we define it) that is finite, not the universe - We stop defining size at Plank scale.
began to expand, for no explicable reason.
Huh? The reasons are known. Who said the reasons were unknown?
4. The not finite universe allegedly became inexplicably finite when the expansion began.
You are misunderstanding and confusing certain terms.
Spacetime is finite in size, Plank scale, the universe has always existed - In other words, existence has always existed.
- Oni

This message is a reply to:
 Message 23 by Buzsaw, posted 11-17-2009 9:43 AM Buzsaw has replied

Replies to this message:
 Message 27 by Buzsaw, posted 11-17-2009 11:52 AM onifre has not replied

  
Buzsaw
Inactive Member


Message 26 of 39 (535692)
11-17-2009 11:49 AM
Reply to: Message 24 by greyseal
11-17-2009 10:57 AM


Re: Imported Universe Response To Onifre
greyseal writes:
no, you misunderstand what onifre meant by "finite". He meant finite as in "had a beginning", not as in "it has an edge".
Hi, Greyseal. That doesn't help much.
Continuum contradiction:
1. Spacetime had a beginning, i.e. is finite
2. The universe is not finite, i.e. had no beginning, having existed before spacetime expansion with different space and time dimensions.
3. Once not finite space and time universe is the existing finite spacetime, not finite universe.
greyseal writes:
the universe IS - I'm not sure about the "just" part. It has been since approximately 13.7 billion years ago.
So you're alleging that the universe, both which have been since 13.7 bya are now one and the same, spacetime being finite and the universe not finite yet both being the one and same expansion? How does that work?
greyseal writes:
"before" and "outside" are words that don't work so very well when you attempt to apply them to the universe.
Yah, I know. Inexplicable, aspects of theories never seem to work well for the theorists.
greyseal writes:
I could be wrong, but from what I understand the agreement is that now it's here it could be eternal, and now it's here it is unbounded and infinite in extent and has been for all of it's existence.
Mmm, then why have I wasted so much time and bandwidth over the past seven years promoting an unbounded infinite universe here at EvC?

BUZSAW B 4 U 2 C Y BUZ SAW.
The immeasurable present eternally extends the infinite past and infinitely consumes the eternal future.

This message is a reply to:
 Message 24 by greyseal, posted 11-17-2009 10:57 AM greyseal has not replied

Replies to this message:
 Message 28 by onifre, posted 11-17-2009 12:55 PM Buzsaw has not replied

  
Buzsaw
Inactive Member


Message 27 of 39 (535693)
11-17-2009 11:52 AM
Reply to: Message 25 by onifre
11-17-2009 11:13 AM


Re: Imported Universe Response To Onifre
Hi Onifre. I was compliling my message as you posted, so didn't see it before responding to Greyseal. I have to go now, but will study your response when I can get to it.

BUZSAW B 4 U 2 C Y BUZ SAW.
The immeasurable present eternally extends the infinite past and infinitely consumes the eternal future.

This message is a reply to:
 Message 25 by onifre, posted 11-17-2009 11:13 AM onifre has not replied

  
onifre
Member (Idle past 2951 days)
Posts: 4854
From: Dark Side of the Moon
Joined: 02-20-2008


(2)
Message 28 of 39 (535707)
11-17-2009 12:55 PM
Reply to: Message 26 by Buzsaw
11-17-2009 11:49 AM


Re: Imported Universe Response To Onifre
Hi Buz,
I'll try to explain a bit further, as I kinda understand your position a bit better.
1. Spacetime had a beginning, i.e. is finite
What is meant by "spacetime" is a description of the geometry of the universe, ie. Minkowski spacetime. That is finite in size down to Plank scale.
This had an origin, the Big Bang.
2. The universe is not finite, i.e. had no beginning, having existed before spacetime expansion with different space and time dimensions.
Sort of, but necessarily with different space and time dimensions; remember, as dimensions, space and time are experienced by things with mass, to speak of it any different is losing the meaning of what space and time dimension are.
There is no "time" as in beginning and end in our universe (or rather, no beginning or end to existence it has always been, there has always been something instead of nothing); there is no back in time or forward in time; these concepts are only relevant to thing which experience it. So to say "before the universe began" is nonsensical because time is a non-factor to existence itself.
So you're alleging that the universe, both which have been since 13.7 bya are now one and the same, spacetime being finite and the universe not finite yet both being the one and same expansion?
Actually, they are both different yet both the same - this may get confusing, and it is also where I get confused a bit as well. So if I screw this up I'd hope it gets caught by someone with more knowledge than me.
The universe from this point forward will be regarded as "existence" (ie. something instead of nothing) - spacetime will describe the geometry (Minkowski) of the observable universe.
In this sense, existence has always existed, but spacetime geometry had its origin at the BB - which is the point where we can describe the "space" of it because it expanded past Plank scale. Smaller than this scale, and we lose the ability to describe "space".
Mmm, then why have I wasted so much time and bandwidth over the past seven years promoting an unbounded infinite universe here at EvC?
I think the confusion comes in when the conversations are trying to describe spacetime as infinte, when it obviously is not. However, it can expand to infinium, and thus we can have spacetime (geometry) that has a finite origin but an infinite "future" so to speak.
You have to be careful how you word things. If you say universe, as we experience it (4D spacetime) then yes, it is finite in origin. But, if you mean universe as in existence (ie. something instead of nothing) then that has always exited - ie. existence has always existed.
This is where conversations overlap between physics and philosophy, and many (including myself) get confused. To postulate a "time" before existence is nonsensical, but fun for philosophical musing. To postulate a "time" before spacetime, is sensical and is what theoreical physicist are pondering and coming up with hypothesis for (String, M-Theory, multi-verse, etc.). It can get confusing when you overlap the two fields of study.
The BB did not create existence, but, it is a moment in the history of the existence of the universe - the moment when spacetime expanded.
I hope this cleared it up a bit more for you, and I hope I explained it right.
- Oni

This message is a reply to:
 Message 26 by Buzsaw, posted 11-17-2009 11:49 AM Buzsaw has not replied

Replies to this message:
 Message 30 by cavediver, posted 11-17-2009 4:32 PM onifre has replied
 Message 34 by DevilsAdvocate, posted 11-19-2009 6:09 AM onifre has not replied

  
CosmicChimp
Member
Posts: 311
From: Muenchen Bayern Deutschland
Joined: 06-15-2007


(1)
Message 29 of 39 (535722)
11-17-2009 3:06 PM
Reply to: Message 3 by Dr Jack
10-16-2009 6:48 AM


Hi Mr Jack,
What exactly are the implications of expanding space-time. I've read here in this thread, and elsewhere the ideas of inflation and galaxies racing away from each other even at very high speeds etc; but I am interested in the effect of expanding space-time upon gravity. Are there any inferences to be made?
Edited by CosmicChimp, : space -> space-time

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cavediver
Member (Idle past 3644 days)
Posts: 4129
From: UK
Joined: 06-16-2005


(2)
Message 30 of 39 (535736)
11-17-2009 4:32 PM
Reply to: Message 28 by onifre
11-17-2009 12:55 PM


Re: Imported Universe Response To Onifre
What is meant by "spacetime" is a description of the geometry of the universe, ie. Minkowski spacetime.
Minkowski space-time is the space-time of Special Relativity. Our Universe is not Minkowskian except over small distances. Same way that the ground is not Euclidean (we live on a spheroid) but appears Euclidean over small enough distances.
That is finite in size down to Plank scale.
I think I know what you are saying here, but the Planck Scale is a scale in the same sense as the atomic scale, and refers to lengths on the order of the Planck Length (1.6 x 10-35) We sometimes use the phrase, *THE* Planck Time, to refer to the earliest moments of the Universe following T=0, but *A* Planck time is simply the geometric length of time, 5.4 x 10-44secs.
I think the confusion comes in when the conversations are trying to describe spacetime as infinte, when it obviously is not. However, it can expand to infinium
No, it could well be infinite in extent spatially at all times T>0 (at T=0, length has no meaning - but that doesn't mean zero-sized!), irrespective of expansion.
The Big Bang space-time (with Cosmological Constant) is finite in extent in the negative time direction, infinite in extent in the positive time direction, and finite or infinite in extent in the spatial directions. If finite, it wraps back on itself as there is no edge.

This message is a reply to:
 Message 28 by onifre, posted 11-17-2009 12:55 PM onifre has replied

Replies to this message:
 Message 31 by onifre, posted 11-18-2009 12:29 PM cavediver has not replied
 Message 32 by Buzsaw, posted 11-18-2009 11:26 PM cavediver has not replied
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