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Old 07-19-2012, 08:50 AM
 
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NightBazaar, i figured that you could answer this for me as your very knowledgeable on astronomy and so my question is that ''just how can the universe be estimated at 46 billion light years in size and yet is only 14 billion years old''? Doesn't that imply that the universe is expanding faster than the speed of light? What am i missing here?
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Old 07-19-2012, 12:20 PM
 
Location: Arizona, The American Southwest
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Originally Posted by 6 Foot 3 View Post
NightBazaar, i figured that you could answer this for me as your very knowledgeable on astronomy and so my question is that ''just how can the universe be estimated at 46 billion light years in size and yet is only 14 billion years old''? Doesn't that imply that the universe is expanding faster than the speed of light? What am i missing here?
Hey 6 Foot 3, how are ya? Well, I think Captain Kirk can answer that question..

Seriously, the mysteries of the universe will be probably never be answered, all I know is that the universe may be infinite, and God only knows what lies billions of light years from our own solar system and galaxy.
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Old 07-19-2012, 04:47 PM
 
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Originally Posted by Magnum Mike View Post
Hey 6 Foot 3, how are ya? Well, I think Captain Kirk can answer that question..
LOL ... maybe i should have asked the Enterprise's computer (Gene Roddenberry's wife's voice) up on it's bridge .

Magnum Mike keep on rockin and rollin buddy .
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Old 07-20-2012, 12:28 PM
 
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Originally Posted by 6 Foot 3 View Post
NightBazaar, i figured that you could answer this for me as your very knowledgeable on astronomy and so my question is that ''just how can the universe be estimated at 46 billion light years in size and yet is only 14 billion years old''? Doesn't that imply that the universe is expanding faster than the speed of light? What am i missing here?
You're right. It points to the expansion of the universe being faster than the speed of light. Although objects within the universe is limited by the speed of light, the universe itself is not required to be constrained by that limit. Following the Big Bang, a rapid expansion of space, known as inflation, is thought to have been many times faster than light speed. The size of the universe jumped from the size of a proton to the size of a galaxy in an extremely short period of time. Following the Inflation Epoch, the growth of the universe began to slow down to what is called "expansion" as it became larger. There is some thought that the inflationary epoch may have given rise to the dimensions of the universe. Inflation is a hypothesis that was first proposed and coined by Alan Guth in 1980 and has been widely accepted as a plausible explanation in the evolution of the universe.

A brief note about the expansion. The FTL speed of expansion is observed at large or global scales of the universe. At local scales, even though the rate of expansion is the same, it's not noticable to us because things are much closer together. Regardless, if the universe does not contract, then distant object will eventually vanish forever from our view. We live in a unique period of time in the universe's evolution, with stars and galaxies, to observe so many things in the universe. In the far distant future, assuming that the universe continues expanding forever, any intelligent forms of life will have no idea that there's anything else beyond their local field of view. No other galaxies to see, and no idea how the universe began. To them, their galaxy would appear to be all there is to the universe.

I think it's probably fair to suggest that Dark Energy played a role in the continued expansion of space but slowed down because of gravity. Oddly, instead of the universe continuing to slow down, gravity began to lose its grip, and it's thought the expansion of space in the universe began to speed up (accelerate) somewhere between 5 to 7 billion years ago. If gravity had been able to maintain its strength, the expansion would've continued slowing down. The growth of the space would have either stopped or reversed into a Big Crunch. It's worth noting that it's possible Gravity could still cause a Big Crunch, but for now, the money seems to be in favor of an infinite expansion.
The Expanding Universe: From Slowdown to Speed Up: Scientific American
Astronomy: acceleration of the universe, hubble time, hubble constant
NASA - Dark Energy Changes the Universe


The universe as we see it today includes two things, the observable universe (everything we can see) and the actual universe (beyond the particle horizon). The observable universe is pretty much all we have to go by. There are probably galaxies forming beyond what we can see, but they are so far that the light emitted from them can never reach us, especially because space continues to expand. The more it expands, the faster objects drift away from our position in the universe. We don't really know how large the actual universe is, nor do we know if there's a limit or if it's just part of an infinite space. We don't know if the expansion of the universe is a part of what's called an eternal inflation or not. If the idea of eternal inflation is true, then it suggests that other universe-like structures can also come into existence all the time, a multiverse.

While it seems strange that the size of the observable universe may be about 46 billion years while the age of the universe is around 13.75 billion years old, we still have to take into account the Inflationary epoch which was many times faster than the speed of light, as well as the accelerated expansion of space. A fudge factor has to be included. In other words, we don't really know the size of the universe. It could be much larger than we think it is. Still, we can make a reasonable guess based on the rate of expansion today compared with the rate of expansion in the past to determine the expansion (and therefore the volume) in the future to give a fair guess as to how large the universe is today. Tools like the WMAP have been a big help. Critical density helps determine the shape of the universe.
By what method is the size (or volume) of the universe at the moment of the big bang (or shortly thereafter) determined? Related to this, how is the size of a black hole determined?
Measuring the Size of the Universe
Origin and Destiny of the Universe - Introduction
NOVA | How Big Is the Universe?

Age of the universe - Wikipedia, the free encyclopedia


The universe contains what appear to be weirdness in our thinking to our experience of everyday life. The universe is not just about space, but it's also about time. The behavior of time is what stumps me. Our view of the universe and everything else is always a view of the past, of how things were a little while ago, even if it's just a matter of microseconds, because it takes time for the light (direct or reflected) to reach our eyes. The more distant an object is, the farther back in time it is when we see it. That's our view of the Present or Now Time.
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Old 07-21-2012, 08:19 AM
 
13,138 posts, read 37,038,382 times
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Originally Posted by NightBazaar View Post
While it seems strange that the size of the observable universe may be about 46 billion years while the age of the universe is around 13.75 billion years old, we still have to take into account the Inflationary epoch which was many times faster than the speed of light, as well as the accelerated expansion of space. A fudge factor has to be included. In other words, we don't really know the size of the universe. It could be much larger than we think it is. Still, we can make a reasonable guess based on the rate of expansion today compared with the rate of expansion in the past to determine the expansion (and therefore the volume) in the future to give a fair guess as to how large the universe is today.
NB Thanks !!

Question: I know that you've talked about the Big Bang Background Radiation before however i'm still a bit perplexed as to how they did/can measure it (WMAP)? So for example lets look at a pond of water and lets say that i drop a rock in the center of it and so in the drop zone where it landed the ripple or shockwaves from it will traverse in all directions to the edge of the pond and will eventually disappear. So my perplexion is that when the Big Bang occured wouldn't the background radiation shockwave also had traversed from the Planck Epoch out towards the known edge of the universe and should had eventually disappeared as well as akin to the 'rock dropped into the pond'' example and if so then how can they measure something that has long dispearsed?

So what am i not understanding here?
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Old 07-21-2012, 04:49 PM
 
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Originally Posted by 6 Foot 3 View Post
NB Thanks !!

Question: I know that you've talked about the Big Bang Background Radiation before however i'm still a bit perplexed as to how they did/can measure it (WMAP)? So for example lets look at a pond of water and lets say that i drop a rock in the center of it and so in the drop zone where it landed the ripple or shockwaves from it will traverse in all directions to the edge of the pond and will eventually disappear. So my perplexion is that when the Big Bang occured wouldn't the background radiation shockwave also had traversed from the Planck Epoch out towards the known edge of the universe and should had eventually disappeared as well as akin to the 'rock dropped into the pond'' example and if so then how can they measure something that has long dispearsed?

So what am i not understanding here?
What the WMAP was measuring were differences in temperature left over from the radiant heat of the Big Bang. It was to give a 'picture' of the early universe. The variations show warm and cool patches. Heat from other sources, like the Milky Way, had to be subtracted to provide the ancient image. As far as I know, it wasn't aimed at determining how large the universe is, but rather a look back in time. The CMBR is everywhere, but so far, no ripples or shockwaves have been found. There is no known edge of the universe.

What we seem to have in terms of size is limited to the observable universe. If you were anywhere else in the universe, you'd be restricted in the same way. There may well be a staggering number of other galaxies that have formed so far beyond that the light from them will never reach us, especially because of the continued acceleration of space. We may never know how large the actual universe is. We can come pretty close to determining the age of the universe, and we have a pretty good idea how far objects are from us, but we still can't be completely certain about the size of the universe. We continue to discover objects much farther than imagined could be possible.

Getting more to the point of how it's done, it's a bit complex as there are a number of methods that can be used, so here are a couple of vids that deal with the subject that can explain it much better than I can.

The first one explains how vast distances are measured.
How do we measure the vast distances of the Universe?


This one is from SpaceRip which tries to answer the question of how large the universe is. It might be far bigger than we can imagine.


How Large is the Universe? - YouTube
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Old 07-22-2012, 12:44 PM
 
Location: Texas
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Originally Posted by 6 Foot 3 View Post
NB Thanks !!

Question: I know that you've talked about the Big Bang Background Radiation before however i'm still a bit perplexed as to how they did/can measure it (WMAP)? So for example lets look at a pond of water and lets say that i drop a rock in the center of it and so in the drop zone where it landed the ripple or shockwaves from it will traverse in all directions to the edge of the pond and will eventually disappear. So my perplexion is that when the Big Bang occured wouldn't the background radiation shockwave also had traversed from the Planck Epoch out towards the known edge of the universe and should had eventually disappeared as well as akin to the 'rock dropped into the pond'' example and if so then how can they measure something that has long dispearsed?

So what am i not understanding here?
Do you think Dark Energy can move light as much as they can with matter? It doesn't seem that way to me.
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Old 07-22-2012, 07:55 PM
 
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With the rock dropped in the pond analogy, the pond is finite and bounded, so the wave will dissipate around the edge.
The universe, however, while being finite, is unbounded, so the waves of the background radiation will, if uninhibited, continue to propagate with their wavelength increasing due to the expansion of space-time.
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Old 07-23-2012, 10:46 AM
 
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Originally Posted by NightBazaar View Post
but we still can't be completely certain about the size of the universe.
The Big Bang Cosmic Inflation must had been incredible as they stated in the video that the universe minimum diameter is estimated around 156 billion light years across as that is just friggin huge.

Thanks again for all your posted info knowledge here NB .
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Old 07-23-2012, 10:49 AM
 
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Originally Posted by Brian.Pearson View Post
Do you think Dark Energy can move light as much as they can with matter? It doesn't seem that way to me.
I'm wondering if the force behind Dark Energy is the same force that was behind Cosmic Inflation.
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