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Expanding Universe


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#16    joc

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Posted 13 December 2007 - 06:16 AM

Torgo,
I know you think you believe what you just wrote.  But the universe isn't 13.7 Billion years old either.  There is no way to know that.  For all we know....the farthest Galaxies we know of are just scratching the surface of what is.

I have the answer:

There is only one star.  The sun.  Everything else is done with mirrors! tongue.gif

I don't even pretend to know all the scientific knowledge that went into your post and how the theories of the BB and the EU are arrived at.   I don't care either.  What I know is that we don't know.  We can't know.  We know what we think we know...but we don't know.

But just for fun...let's say that BB and EU are correct.  So what you are telling me is that about 14 billion years ago it all began....for the first time?  or the hundredth billionth time?  I mean really...what's 14 billion years?  It isn't even a fraction really of 478 Trillion years.   ANd how fast was the Universe traveling at the moment of the BB?  Faster than the speed of light itself?  That btw is a question I am really actually asking you...because if it wasn't faster than the speed of light itself...how could there be galaxies trillions of light years away?  And if it was faster than the speed of light...well, just explain that one plz. original.gif

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#17    Torgo

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Posted 13 December 2007 - 12:42 PM

joc on Dec 13 2007, 01:16 AM, said:

Torgo,
I know you think you believe what you just wrote.  But the universe isn't 13.7 Billion years old either.  There is no way to know that.  For all we know....the farthest Galaxies we know of are just scratching the surface of what is.

I have the answer:

There is only one star.  The sun.  Everything else is done with mirrors! tongue.gif

I don't even pretend to know all the scientific knowledge that went into your post and how the theories of the BB and the EU are arrived at.   I don't care either.  What I know is that we don't know.  We can't know.  We know what we think we know...but we don't know.

But just for fun...let's say that BB and EU are correct.  So what you are telling me is that about 14 billion years ago it all began....for the first time?  or the hundredth billionth time?  I mean really...what's 14 billion years?  It isn't even a fraction really of 478 Trillion years.   ANd how fast was the Universe traveling at the moment of the BB?  Faster than the speed of light itself?  That btw is a question I am really actually asking you...because if it wasn't faster than the speed of light itself...how could there be galaxies trillions of light years away?  And if it was faster than the speed of light...well, just explain that one plz. original.gif


We've got no idea as to the size of the universe.  Personally, unless evidence appears to the contrary I'm going with infinite.  I do so because as near as we can tell space is not curved at large scales, meaning it cant curve around in a fifth dimension to double back on itself.  However, what matters is that we can only see a finite distance in every direction, indicating that light has had a finite time to travel which we can calculate.

We also cannot know anything, at least with current physics, about any possible other universes.  It's just something we can't test right now.  So I can't really say anything about that than it is entirely possible they exist but it doesn't really enter into study of this universe except possibly for the exact instant it came into being.

The thing about the big bang is that it appears to be a question of SPACE stretching rather than objects moving through space; objects moving though space have to obey general relativity while if there is something driving changes in space itself, space can do whatever it wants.  We see this as incredibly intense redshifts at the edge of the observable universe, using the doppler effect we see this as an apparent velocity approaching that of light.  

We CANNOT see anything trillions of lightyears away.  The "cosmic horizon", how far we can see, is about 50 billion lightyears away.  This is what you get when you take the distance we can see and use some calculus and integrate the expansion rate times distance - everything we can see (much of which is far back in time) will have expanded from 13.7 billion lightyears in radius to 50 billion lightyears in radius by now.



#18    joc

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Posted 13 December 2007 - 12:52 PM

Quote

We've got no idea as to the size of the universe. Personally, unless evidence appears to the contrary I'm going with infinite.

Respectfully, how can one limit an infinite universe to a finite number of 13.7?  I understand from the next quote how one arrives at that number but...it makes no sense to me.  Not really.  Not mathmatically speaking (although I haven't a clue about calculus) but 'logically' speaking.

Quote

This is what you get when you take the distance we can see and use some calculus and integrate the expansion rate times distance - everything we can see (much of which is far back in time) will have expanded from 13.7 billion lightyears in radius to 50 billion lightyears in radius by now.

And this is because 'space' is expanding?

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#19    rideron

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Posted 13 December 2007 - 01:18 PM

Torgo on Dec 13 2007, 02:27 AM, said:

The big bang is NOT a bunch of mass originating at one point and spweing out into space.  As near as we can tell matter and space originated together with matter embedded in space throughout.  Since that time the space has stretched moving the matter further and further apart decreasing the overall density of the universe and stretching light out to longer and longer wavelengths - hence the Doppler shift.  

The classic example to ilustrate this is a balloon.  Take a sharpie and put little dots all over it.  These are collections of matter, like galaxies.  Blow up the balloon, or take your hands and stretch it out - the dots do not explode out from any point, they just get further and further away while the rubber they're on gets bigger.

As near as we can see the universe has no edge.  We can only see a finite distance away but that is because light has had a finite time to travel since the universe became transparent to light when it cooled down enough for the initial plasma to combine into neutral gas molecules.


The background radiation we see is NOT the radiation from the (nonexistant) "Explosion" of the big bang.  What it IS is the heat glow of the universe at the moment it became transparent to light, redshifted down into the microwaves by the expansion of space.



O.K. so "matter and space originated together with matter embedded in space throughout" and I get the illustration of the expanding balloon with dots all over it; but you are sidestepping my  original question:  To use your analogy  we have an 'expanding balloon', but what is it into which the balloon is expanding????  If all reality creation matter and space is the balloon itself????


#20    joc

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Posted 14 December 2007 - 06:12 PM

rideron on Dec 13 2007, 01:18 PM, said:

O.K. so "matter and space originated together with matter embedded in space throughout" and I get the illustration of the expanding balloon with dots all over it; but you are sidestepping my  original question:  To use your analogy  we have an 'expanding balloon', but what is it into which the balloon is expanding????  If all reality creation matter and space is the balloon itself????

I don't think the balloon is a good analogy at all because the space on the 'inside' of the balloon doesn't stretch..only the balloon itself.  

I do understand however that if the Big Bang occurred...then the Light from that Explosion would be traveling outwards at the speed of light...but the star systems themselves would be traveling...?...how fast is the Universe therefore theorized to be expanding?

And how do we have any clue where we are exactly in an infinite Universe?  If we don't have a clue...how can we theorize about the beginning of it?

Edited by joc, 14 December 2007 - 06:12 PM.

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#21    Torgo

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Posted 16 December 2007 - 03:36 AM

joc on Dec 14 2007, 01:12 PM, said:

I don't think the balloon is a good analogy at all because the space on the 'inside' of the balloon doesn't stretch..only the balloon itself.  

I do understand however that if the Big Bang occurred...then the Light from that Explosion would be traveling outwards at the speed of light...but the star systems themselves would be traveling...?...how fast is the Universe therefore theorized to be expanding?

And how do we have any clue where we are exactly in an infinite Universe?  If we don't have a clue...how can we theorize about the beginning of it?


You're right about the balloon analogy, it falsely implies that there is a known volume with at least one more dimension containing our universe.  All we can tell about our universe is that the coordinate system we call space is expanding.  In fact, the idea that the universe is somehow expanding into another higher-dimensional volume is probably meaningless - it can completely be described as the coordinate system shifting (more space appearing between any two given points) with time.

As for light from the "explosion", again there was no explosion.  We just started out hot and dense and have ended up cold and diffuse.  However, this hot and dense state certainly did put out a lot of light and radiation just from blackbody radiation... and we see this coming at us from all directions at once, EXTREMELY uniformly.  This is the cosmic microwave background radiation I mentioned earlier, the light that's spectrum indicates that it was extremely hot when the light was emitted but as space has stretched the light has redshifted all the way to the microwaves.

Asking "where we are in an infinite universe" is meaningless - there are an infinite number of places to be and you cant pick one as special over any other.  However, again we probably cannot ever know the true extent of the universe just because of the speed of light.  We can only see a finite distance in any given direction.  If the universe wraps around and is interconnected, like the surface of a sphere, EVENTUALLY light will be able to make it all the way around but who knows how big it could be.  The fact though that space on large scales is very nearly euclidean seems to indicate that the universe is either infinite or extremely large.


#22    joc

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Posted 16 December 2007 - 03:54 AM

Torgo on Dec 16 2007, 03:36 AM, said:

You're right about the balloon analogy, it falsely implies that there is a known volume with at least one more dimension containing our universe.  All we can tell about our universe is that the coordinate system we call space is expanding.  In fact, the idea that the universe is somehow expanding into another higher-dimensional volume is probably meaningless - it can completely be described as the coordinate system shifting (more space appearing between any two given points) with time.

As for light from the "explosion", again there was no explosion.  We just started out hot and dense and have ended up cold and diffuse.  However, this hot and dense state certainly did put out a lot of light and radiation just from blackbody radiation... and we see this coming at us from all directions at once, EXTREMELY uniformly.  This is the cosmic microwave background radiation I mentioned earlier, the light that's spectrum indicates that it was extremely hot when the light was emitted but as space has stretched the light has redshifted all the way to the microwaves.

Asking "where we are in an infinite universe" is meaningless - there are an infinite number of places to be and you cant pick one as special over any other.  However, again we probably cannot ever know the true extent of the universe just because of the speed of light.  We can only see a finite distance in any given direction.  If the universe wraps around and is interconnected, like the surface of a sphere, EVENTUALLY light will be able to make it all the way around but who knows how big it could be.  The fact though that space on large scales is very nearly euclidean seems to indicate that the universe is either infinite or extremely large.

Very interesting Torgo!  The word Bang...implies an explosion of sorts...which is how I have always heard and perceived it.  Your description of it makes since to me...especially in the 'belief' that I have that God created the Universe....in Genesis before the Earth and Sun were created God said ...let there be light.   Perhaps this was the light you talk about...it also describes Darkness upon the face of the Deep.  If there was Darkness upon the face of the Deep...and God said let there be Light...could that not be interpreted as your definition of Big Bang?

Edited by joc, 16 December 2007 - 03:55 AM.

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#23    Cradle of Fish

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Posted 16 December 2007 - 02:06 PM

joc on Dec 13 2007, 06:16 AM, said:

I don't even pretend to know all the scientific knowledge that went into your post and how the theories of the BB and the EU are arrived at.   I don't care either.  What I know is that we don't know.  We can't know.  We know what we think we know...but we don't know.


If we all thought like that we'd all still be living in caves in Africa, scared of fire.

You're quite confident that we dont know all this, how do you know we dont know? You cant know. The only thing we know is that you cant know whether or not we dont know.

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#24    joc

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Posted 16 December 2007 - 02:15 PM

Cradle of Fish on Dec 16 2007, 02:06 PM, said:

If we all thought like that we'd all still be living in caves in Africa, scared of fire.

You're quite confident that we dont know all this, how do you know we dont know? You cant know. The only thing we know is that you cant know whether or not we dont know.



Were we ever really scared of fire?  We cannot 'know' the origin of the Universe.   We can theorize, we can guess, we can come to a general agreement of theories...but we cannot know.   Can one explain with any certainty what existed prior to the origin?  Many just hear the theory and except it as fact.  I accept as fact that one can theorize but not know with absolute certainty.

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#25    Torgo

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Posted 19 December 2007 - 04:55 AM

joc on Dec 16 2007, 09:15 AM, said:

Were we ever really scared of fire?  We cannot 'know' the origin of the Universe.   We can theorize, we can guess, we can come to a general agreement of theories...but we cannot know.   Can one explain with any certainty what existed prior to the origin?  Many just hear the theory and except it as fact.  I accept as fact that one can theorize but not know with absolute certainty.


You can say the same thing about any scientific idea or discovery.  We do not "know with absolute certainty" that electrons exist.  We do not even "know with absolute certainty" that gravity always works the way the law of gravity describes it does.  However, the theory of quantum electrodynamics explains down to as many decimal places we can measure exactly how electrical charge and current behaves, and the theory of gravity has, so far, explained large-scale motion in the universe.  The big bang theory came about the same way as these other theories - looking at evidence, proposing models to explain them, and testing these models.  The big bang theory has held up over and above any other model of the universe's history and origins.  That is why we believe it is true.  If more evidence that comes to light that shows it cannot be true, it will be discarded.  However, it has been rather closely confirmed.

Example:  the redshift of galaxies has been known for a long time, and it suggested that some time in the distant past the universe was quite dense.  When you squeeze gas into a smaller volume, it heats up.  Therefore, the universe should've been hot long ago.  

The microwave background radiation was not well measured until the COBE satellite went up to measure it.  When they measured it, they looked at the shape of its spectrum because they knew they could not use its frequency to look at the temperature of the early universe - it would have redshifted.  If the universe used to be hot, the shape of the spectrum should be that of a hot gas while being shifted to the long wavelengths.  And that is exactly what they found.

Edited by Torgo, 19 December 2007 - 04:58 AM.


#26    Sagredo

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Posted 19 December 2007 - 07:17 AM

Torgo on Dec 18 2007, 08:55 PM, said:

You can say the same thing about any scientific idea or discovery.  We do not "know with absolute certainty" that electrons exist.  We do not even "know with absolute certainty" that gravity always works the way the law of gravity describes it does.  However, the theory of quantum electrodynamics explains down to as many decimal places we can measure exactly how electrical charge and current behaves, and the theory of gravity has, so far, explained large-scale motion in the universe.  The big bang theory came about the same way as these other theories - looking at evidence, proposing models to explain them, and testing these models.  The big bang theory has held up over and above any other model of the universe's history and origins.  That is why we believe it is true.  If more evidence that comes to light that shows it cannot be true, it will be discarded.  However, it has been rather closely confirmed.

Example:  the redshift of galaxies has been known for a long time, and it suggested that some time in the distant past the universe was quite dense.  When you squeeze gas into a smaller volume, it heats up.  Therefore, the universe should've been hot long ago.  

The microwave background radiation was not well measured until the COBE satellite went up to measure it.  When they measured it, they looked at the shape of its spectrum because they knew they could not use its frequency to look at the temperature of the early universe - it would have redshifted.  If the universe used to be hot, the shape of the spectrum should be that of a hot gas while being shifted to the long wavelengths.  And that is exactly what they found.


Very well put Torgo! People need to remember that Science is not about "proving" things or about absolute certainty. Theorems are proved in Mathematics (given a set of axioms). Theories in science (e.g. Big Bang cosmology, Evolution) are explanatory frameworks prposed to account for a range of experimental observations. Scientific theories are accepted to the extent that they successfully explain all or most of the relevant observations and are in general harmony with other accepted theories. Scientific theories, as such, can never be proven true. After all, a new observation could always be made which would contradict them. Or an even better theory might come along tomorrow.


#27    Lovelynice

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Posted 31 December 2007 - 12:27 PM

Torgo on Dec 12 2007, 03:49 PM, said:

Interestingly enough, looking at the redshifts and intensities of supernovas in distant galaxies that are known to always have the same intensity and spectrum, it has come to light that the universe's expansion is actually ACCELERATING.  No one KNOWS why this is, but this is the observation that "dark energy" has been proposed to explain.


But why take redshifts as the evidence of both distance and acceleration, when there might be other possible causes for the redshifting?


#28    Raptor

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Posted 31 December 2007 - 01:07 PM

Torgo on Dec 13 2007, 12:42 PM, said:

We've got no idea as to the size of the universe.  Personally, unless evidence appears to the contrary I'm going with infinite.  I do so because as near as we can tell space is not curved at large scales, meaning it cant curve around in a fifth dimension to double back on itself.  However, what matters is that we can only see a finite distance in every direction, indicating that light has had a finite time to travel which we can calculate.


That's news to me, I always thought that the idea of a finite yet unbounded universe was commonly accepted. Is there a particular theory (hypothesis?) that deals with the whole of space being curved back on itself, or is it just an interpretation of general relativity? I'd like to read more about it.


#29    Lord Of The Dragons

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Posted 31 December 2007 - 10:32 PM

Raptor on Dec 31 2007, 01:07 PM, said:

That's news to me, I always thought that the idea of a finite yet unbounded universe was commonly accepted. Is there a particular theory (hypothesis?) that deals with the whole of space being curved back on itself, or is it just an interpretation of general relativity? I'd like to read more about it.


Ever had one of those moments where something screams at you but, for the life of you, you can't remember what it is?
That's what happened to me when I read your post. I can answer your question, I just can't remember it. laugh.gif
I think it has to do with Quantum Mechanics. Relativity allows for Wormholes in space. Yet, according to Quantum Mechanics, Wormholes can only exist if Space/Time is curved.
Again, I'm not too sure about this, I only post it in case it might jog someone else's memory and provide us with the right answer. Then I can justifiably kick myself for not remembering in the first place. grin2.gif

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#30    Lovelynice

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Posted 03 January 2008 - 02:27 AM

Lovelynice on Dec 31 2007, 09:27 PM, said:

But why take redshifts as the evidence of both distance and acceleration, when there might be other possible causes for the redshifting?



Nobody seems to want to answer this question, or discuss it.

I see the problem is that without the excuse of redshifting being being blamed solely on an object moving away, and not on other possible reasons such as the depletion of energy through entropy and distance, gravitational distortion, or cosmic dust, there is no real evidence for the claim that the further away glaxies are, the faster they are moving away. The expanding universe claim depends on redshshift, but if redshift is caused by something else besides movement away, not just movement, then there doesn't seem to be much evidence for an expanding universe.

Edited by Lovelynice, 03 January 2008 - 02:28 AM.





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