How big?

[cosmicdustbunnie]

How much universe can we see compared to how much we think there is? <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000">*<font color="#ff6600">t</font><font color="#ffcc00">w</font><font color="#00ff00">i</font><font color="#00ffff">n</font><font color="#00ccff">k</font><font color="#993366">l</font><font color="#0000ff">e </font><font color="#800080">t</font><font color="#ff00ff">w</font><font color="#ff0000">i</font><font color="#ff6600">n</font><font color="#ffcc00">k</font><font color="#00ff00">l</font><font color="#00ffff">e</font><font color="#993366">*</font></font></p> </div>

 

[bearack]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>How much universe can we see compared to how much we think there is? <br />Posted by cosmicdustbunnie</DIV><br /><br />Cosmic, a new avatar?&nbsp; </p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <p><br /><img id="06322a8d-f18d-4ab1-8ea7-150275a4cb53" src="http://sitelife.space.com/ver1.0/Content/images/store/6/14/06322a8d-f18d-4ab1-8ea7-150275a4cb53.Large.jpg" alt="blog post photo" /></p> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>How much universe can we see compared to how much we think there is? <br /> Posted by cosmicdustbunnie</DIV></p><p>&nbsp;</p><p>It really depends on how you interpret "see".&nbsp; We can 'see' 13+ billion light years away, but that's not really a physical distance.&nbsp; That's just how long it took the photons to reach our instruments, not how much physical space they travelled through.</p><p>What we are causally connected to, depending on your source, is a sphere with a radius of about 46 billion light years.&nbsp; A galaxy we might view through a telescope at a distance of 12 billlion light years could be, in terms of it's location today, 40+ billion light years distance.&nbsp; Because of the metric expansion of space, that particular galaxy may have been only several 100 million years distant when it emitted it's light.&nbsp; Those photons, however, had to travel through an expanding space that took 12 billion years to traverse.</p><p>In the inflationary model of the universe, the Universe is, quite likely, much, much larger than the observalbe universe.&nbsp; But since that part of the Universe is causally disconnected (that space is expanding faster than the speed of light), we can never know how much there is.&nbsp; All we can do is work with and interact with our observable universe... beyond that is more a question of philosophy.&nbsp;</p><p>One thing that can confuse some folks, when describing the universe, is using the term Light Year as a distance reference when we should be using megaparcecs (combination of parallex and arcseconds).</p><p>Sort of like us Yanks using miles instead of kilometers <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-laughing.gif" border="0" alt="Laughing" title="Laughing" />. </p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[bearack]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;It really depends on how you interpret "see".&nbsp; We can 'see' 13+ billion light years away, but that's not really a physical distance.&nbsp; That's just how long it took the photons to reach our instruments, not how much physical space they travelled through.What we are causally connected to, depending on your source, is a sphere with a radius of about 46 billion light years.&nbsp; A galaxy we might view through a telescope at a distance of 12 billlion light years could be, in terms of it's location today, 40+ billion light years distance.&nbsp; Because of the metric expansion of space, that particular galaxy may have been only several 100 million years distant when it emitted it's light.&nbsp; Those photons, however, had to travel through an expanding space that took 12 billion years to traverse.In the inflationary model of the universe, the Universe is, quite likely, much, much larger than the observalbe universe.&nbsp; But since that part of the Universe is causally disconnected (that space is expanding faster than the speed of light), we can never know how much there is.&nbsp; All we can do is work with and interact with our observable universe... beyond that is more a question of philosophy.&nbsp;One thing that can confuse some folks, when describing the universe, is using the term Light Year as a distance reference when we should be using megaparcecs (combination of parallex and arcseconds).Sort of like us Yanks using miles instead of kilometers . &nbsp; <br />Posted by derekmcd</DIV></p><p>That was kind of my thinking, if I read your response right. With the universe expanding, there is no real way to see the end because the protons we see now are billions of years old with billions of years of expansion still occuring.</p><p><br /><br />&nbsp;</p> <div class="Discussion_UserSignature"> <p><br /><img id="06322a8d-f18d-4ab1-8ea7-150275a4cb53" src="http://sitelife.space.com/ver1.0/Content/images/store/6/14/06322a8d-f18d-4ab1-8ea7-150275a4cb53.Large.jpg" alt="blog post photo" /></p> </div>

 

[centsworth_II]

<p><font color="#666699"><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'> All we can do is work with and interact with our observable universe... beyond that is more a question of philosophy. <br /> Posted by derekmcd</DIV></font></p><p>We may well be at the stage where we can see as far as we ever will be able to.&nbsp; We can see as far as the laws of physics allow.&nbsp; Within that, there is still much that we haven't yet seen.&nbsp; The volume is so vast that we have just started to image it. And of course the mystery of dark energy and dark matter remains.&nbsp; </p> <div class="Discussion_UserSignature"> </div>

 

[centsworth_II]

<p><font color="#666699"><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>How much universe can we see compared to how much we think there is? <br /> Posted by cosmicdustbunnie</DIV></font></p><p>Imagine standing in a dark room.&nbsp; You can barely see your hand in front of your face.&nbsp; You hold a candle that puts out just enough light to barely see how far away the walls are, but the light is too dim to see all the small objects between you and the walls.&nbsp; So you know the size of the room, but not what it contains.&nbsp; This is similar to the cosmic background radiation studies.</p><p>You also have a laser light that can shoot a bright, narrow beam all the way to the wall.&nbsp; It is bright enough to see small bits of dust floating in the room, but only those along the narrow beam.&nbsp; This is similar to the Hubble deep field study.</p><p>Putting the two together, we have a good idea of the size of the visible universe and the visible material it contains, but we have actually only looked at a tiny fraction of that material.&nbsp;</p> <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>We may well be at the stage where we can see as far as we ever will be able to.&nbsp; We can see as far as the laws of physics allow.&nbsp; Within that, there is still much that we haven't yet seen.</p><p> Posted by centsworth_II</DIV></p><p>There's different ways you can look at.</p><p>1.&nbsp; There is a limit to how far back in time we can look.&nbsp; That wall is ~300k years after the proposed beginning of time.&nbsp; Prior to this, the universe was too dense for photons to escape making it opaque.&nbsp; The oldest stuff we can look at is the Cosmic Microwave Background Radiation. &nbsp;</p><p>2.&nbsp; The most distance galaxy clusters we can see are, in the "now" time, some 40+ billion light years away.&nbsp; We see them as they were ~12 billion years ago.&nbsp; As the universe ages, light has more time to reach us.&nbsp; The logical conclusion being that older and more galaxy clusters could come into view as the universe ages.&nbsp; Our observable is getting bigger. </p><p>3.&nbsp; We are limited by the metric expansion of space.&nbsp;&nbsp; With&nbsp; space expanding, the co-moving distance between us and distant clusters are always increasing at an ever quickening pace.&nbsp; The farther away, the quicker the expansion.&nbsp; The metric expansion of space can make some of those same galaxies that we can currently 'see' within our light cone will begin to recede faster than light.&nbsp; There not travelling through space faster than light... just the expansion of space between us is.</p><p>4.&nbsp; The ultimate limit is due to causality.&nbsp; Stuff outside our observable universe has been and always will be beyond interaction.&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[centsworth_II]

<p><font color="#666699"><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>As the universe ages, light has more time to reach us.&nbsp; The logical conclusion being that older and more galaxy clusters could come into view as the universe ages.<br /> Posted by derekmcd</DIV><br /></font>We can already see the oldest galaxies in the universe, when they were young.&nbsp; I get the impression that the age of galaxy formation was over in the first few billion years and that all the galaxies that will ever exist in our observable universe are already available for observation by us.&nbsp; Leaving aside collisions combining, and ripping apart existing galaxies.</p><p>The observable universe will be about 20 billion years old when the Earth is obliterated by our dying sun.&nbsp; So at best, we could only see the galaxies age another 6 billion years before that event. </p> <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

<p><strong>"We can already see the oldest galaxies in the universe, when they were young."</strong>&nbsp; </p><p>&nbsp;This is true.&nbsp; I could've worded my statement a bit better by not referring to the clusters as older.&nbsp; The oldest galaxies age along with us.</p><p>&nbsp;</p><p><strong>"I get the impression that the age of galaxy formation was over in the first few billion years and that all the galaxies that will ever exist in our observable universe are already available for observation by us."</strong></p><p>The observable universe doesn't necessarily refer to what we can visibly see through our telescopes.&nbsp; Only that it is still causally connectioned to us.&nbsp; There may be galaxies that are further out, but their light simply hasn't reached us yet.&nbsp; As long as the co-moving distance between us is expanding less than C, it will come into view in the future.<br /><br /></p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[centsworth_II]

<p><font color="#666699"><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>"The observable universe doesn't necessarily refer to what we can visibly see through our telescopes.&nbsp; Only that it is still causally connectioned to us.&nbsp; There may be galaxies that are further out, but their light simply hasn't reached us yet.<br /> Posted by derekmcd</DIV></font></p><p>We have looked out (and back) with our most powerful telescopes to see the formation of the earliest galaxies, formed as soon after the big bag as galaxies could form: </p><p>Hubble glimpses early galaxy formation&nbsp; </p><p><font size="2">Telescopes Spot Early Galaxy Forming</font></p><p>&nbsp;</p><p>&nbsp;If this is the case, how could there be any farther and older galaxies to see? </p> <div class="Discussion_UserSignature"> </div>

 

[weeman]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>How much universe can we see compared to how much we think there is? <br />Posted by cosmicdustbunnie</DIV><br /><br />Really big....really, really, really, really, really, really...</p><p>[10 minutes later]</p><p>...really, really, really, really BIG!</p><p><img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-laughing.gif" border="0" alt="Laughing" title="Laughing" /></p> <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>We have looked out (and back) with our most powerful telescopes to see the formation of the earliest galaxies, formed as soon after the big bag as galaxies could form: Hubble glimpses early galaxy formation&nbsp; Telescopes Spot Early Galaxy Forming&nbsp;&nbsp;If this is the case, how could there be any farther and older galaxies to see? <br /> Posted by centsworth_II</DIV></p><p>SpeedFreek could explain this stuff far better than me.&nbsp; It, essentially, come down to:</p><p>1. There are galaxy clusters that are currently 46 billion light years (Gly) away that sent light our direction very early in the universe that is just now getting to us.&nbsp; These are the early galaxies that the Hubble Deep Field imaged. This the observable universe that is growing with time.&nbsp; We seem them at an age of 12Gly, but they are not 12gly distant.&nbsp; Because the observable universe is expanding, that light took 12Gly years to reach us even though very early in the universe they were much closer.</p><p>2. There are galaxiy clusters that are currently 62 Gly away which sent their light off very early in the unverse and haven't reached us yet, but eventually will.&nbsp; These galaxies are not yet causally disconnected from us.&nbsp; Beyond 62 Gly is our cosmological event horizon.&nbsp; These galaxies were further away and, as such, the light has taken longer to reach us than those mentioned above. </p><p>3.&nbsp; There are galaxy cluster that are beyond 62 Gly away which sent their light off very early in the universe and due to the metric expansion of space will never reach us.&nbsp; The recessional velocities of the co-moving distance is now, or will be, beyond the speed of light before it can cross our particle horizon (aka observable universe) which is expanding.&nbsp; The further the distance between the comoving object, the higher the recession velocities.&nbsp; Enough distance, it is faster than the speed of light and causaully disconnected from us.&nbsp; It's not the proper motion through space of the 2 objects that are causing the recession, rather the the expansion of space inbetween them.&nbsp; Therefore there is no violation of relativity.</p><p>&nbsp;</p><p>Here's a good pdf file.&nbsp; Download it (it's really small) and look at figure 1 on page 3.&nbsp; Shows 3 graphical representations.&nbsp; The bottom one is the one I could understand the best.&nbsp;</p><p>http://arxiv.org/abs/astro-ph/0310808</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[DrRocket]

<p>This link takes you to a pretty good explanation of cosmic distance scales and what they really mean.</p><p>http://www.atlasoftheuniverse.com/redshift.html</p> <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>This link takes you to a pretty good explanation of cosmic distance scales and what they really mean.http://www.atlasoftheuniverse.com/redshift.html <br /> Posted by DrRocket</DIV></p><p>I'm not sure how they came up with this in their first paragraph:</p><p><strong>"By this time, the galaxies are separated by about 26 billion light years; the pulse of light has been travelling for 13 billion years;"</strong> </p><p>The animation shows the light reaching the observer after 13 billion years... their expansion can't be representing the metric aspect of it.&nbsp; The cluster would be over 40 gly away at that point.&nbsp; They simply doubled the distance compared to the travel time.</p><p>Here's a neat calculator from Ned Wright's site:</p><p>http://www.astro.ucla.edu/%7Ewright/CosmoCalc.html</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I'm not sure how they came up with this in their first paragraph:"By this time, the galaxies are separated by about 26 billion light years; the pulse of light has been travelling for 13 billion years;" The animation shows the light reaching the observer after 13 billion years... their expansion can't be representing the metric aspect of it.&nbsp; The cluster would be over 40 gly away at that point.&nbsp; They simply doubled the distance compared to the travel time.Here's a neat calculator from Ned Wright's site:http://www.astro.ucla.edu/%7Ewright/CosmoCalc.html <br />Posted by derekmcd</DIV></p><p>I think that this numbers are off a bit.&nbsp; But the explanation as to what the different scales is meant to be is, I think, the useful part and pretty clear.&nbsp; His animation shows the galaxies receding from one another at a constant "speed", whereas with an expanding universe model the rate of recession ought to actually increase as separation increases.&nbsp; So I agree that his numbers are off.&nbsp; But the illustration of light chasing the moving, moving at a constant local velocity (c) while space expands to create the "chase" is illustrative.&nbsp; I'll give the guy credit for trying to provide an animation of a difficult thing to visualize.&nbsp; </p> <div class="Discussion_UserSignature"> </div>

 

[centsworth_II]

<p><font color="#666699"><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>1. There are galaxy clusters that are currently 46 billion light years (Gly) away that sent light our direction very early in the universe that is just now getting to us.&nbsp; These are the early galaxies that the Hubble Deep Field imaged. Posted by derekmcd</DIV></font></p><p>This much, I get.&nbsp; But what confuses me is statements like, "Recently using the Keck telescope, a team... found six star forming galaxies about 13.2 billion light years away and therefore created when the universe was only 500 million years old..." </p><p>I took such statements to mean that we can see -- with great effort -- back to the time of galaxy formation, and that&nbsp; there is simply nothing to see beyond that.&nbsp; Nothing with structure enough to resolve in any case. </p><p>Maybe it's a mistake on my part to think that we have seen back to the entire time of galaxy formation and have seen nothing past that simply because that is a time prior to galaxy formation and there are no galaxies to be seen.&nbsp;</p><p>&nbsp;</p><p><font color="#666699">Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>2. There are galaxiy clusters that are currently 62 Gly away which sent their light off very early in the unverse and haven't reached us yet, but eventually will. Posted by derekmcd</DIV> </font></p><p>It seems that by definition, we do not know that such galaxies exist because we cannot see them.&nbsp; I suppose that current theory holds that the conditions were right for galaxy formation at a time which we have not yet observed and so galaxies were formed that we cannot yet see?&nbsp; Or could it be that the region that currently lies between 40 and 62 billion light years away is from a time and space before the era of galaxy formation?</p><p>&nbsp;</p><p><font color="#999999">Also, in another discussion on SDC, I think the consensus (here) was that the expansion of space "slid" past any matter occupying that space.&nbsp; if so, it seems that a large part of that 40 to 62 billion light year region would be occupied by expanded space but no matter -- at least at the scale of galaxies.<font color="#000000"> Edit: After thinking, the expanding space would slide past the gravitationally bound galaxies in a cluster, but not past the clusters themselves.</font></font></p><br /><p>&nbsp;</p><p>&nbsp; </p><p>&nbsp;</p> <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'><font color="#808080">This much, I get.&nbsp; But what confuses me is statements like, "Recently using the Keck telescope, a team... found six star forming galaxies about 13.2 billion light years away and therefore created when the universe was only 500 million years old..." I took such statements to mean that we can see -- with great effort -- back to the time of galaxy formation, and that&nbsp; there is simply nothing to see beyond that.&nbsp; Nothing with structure enough to resolve in any case.</font></DIV></p><p>This is correct and here we are dealing with distance as measured by light-travel time. </p><p>&nbsp;</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'><font color="#808080">Maybe it's a mistake on my part to think that we have seen back to the entire time of galaxy formation and have seen nothing past that simply because that is a time prior to galaxy formation and there are no galaxies to be seen.&nbsp;&nbsp; It seems that by definition, we do not know that such galaxies exist because we cannot see them.&nbsp; I suppose that current theory holds that the conditions were right for galaxy formation at a time which we have not yet observed and so galaxies were formed that we cannot yet see?</font></DIV></p><p>We assume that when galaxies formed, they formed throughout the universe as we assume the universe is, at the large scales, homogeneous and isotropic. We are currently receiving only CMBR from the edge of our observable universe, CMBR radiation that was emitted nearly 13.7 billion years ago when the observable universe is estimated to have been a volume only around 40 million light years in radius, but we assume that volume has since expanded and has a current (co-moving) radius of around 46 billion light years.</p><p>If the galaxies have formed throughout the universe then we can assume that there are galaxies that are currently at the edge of our observable universe, at co-moving coordinates from which we have only received radiation that was emitted nearly 13.7 billion years ago.</p><p>&nbsp;</p><p>&nbsp;Replying to:<BR/><DIV CLASS='Discussion_PostQuote'><span style="color:#808080">Or could it be that the region that currently lies between 40 and 62 billion light years away is from a time and space before the era of galaxy formation?</span></DIV></p><p>Those are co-moving distances. The light-travel time distances between 13.7 billion years ago and when galaxies formed, perhaps 100 - 500 million years later, are the places where we would be looking at space before the era of galaxy formation.</p><p>The co-moving region between 40 and 62 billion light years away contains coordinates from which we will in the future receive radiation or light that was emitted in the distant past. We assume there are galaxies in that region now, and we expect to receive firstly CMBR from those coordinates and eventually light from galaxies that formed at those coordinates.</p><p><br />The co-moving region that is currently beyond 16 billion light years away, beyond the cosmological event horizon, represents the region from which we will never receive light that is emitted today, although we will receive older light from that region that is already on its way towards us but was emitted when that region was closer to us.&nbsp;</p><p>&nbsp;</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'><span style="color:#808080">Also, in another discussion on SDC, I think the consensus (here) was that the expansion of space "slid" past any matter occupying that space.&nbsp; if so, it seems that a large part of that 40 to 62 billion light year region would be occupied by expanded space but no matter -- at least at the scale of galaxies. Edit: After thinking, the expanding space would slide past the gravitationally bound galaxies in a cluster, but not past the clusters themselves.</span>&nbsp;&nbsp; &nbsp; <br /> Posted by centsworth_II</DIV></p><p>Using the cosmological principle, if you put yourself in a galaxy that is between 40 and 62 billion light years away right now, the universe there should look pretty similar to the universe here.</p><p>&nbsp;</p><p>Light-travel time distance: The time that light has been travelling for</p><p>Co-moving distance: The distance away that a coordinate in space is estimated to be, right now (or at a specified time).</p><p>(Sorry if this post isn't very clear, I was out in the sun today and my head is a little muzzy!)<img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-embarassed.gif" border="0" alt="Embarassed" title="Embarassed" /> </p> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[centsworth_II]

<font color="#666699"><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>(Sorry if this post isn't very clear, I was out in the sun today and my head is a little muzzy!) <br /> Posted by SpeedFreek</DIV></font><br />It all sounds pretty clear, even if I don't quite get it at first read.&nbsp; It's going to take awhile for this stuff to sink in. <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

<p><strong>"This much, I get.&nbsp; But what confuses me is statements like, "Recently using the Keck telescope, a team... found six star forming galaxies about 13.2 billion light years away and therefore created when the universe was only 500 million years old..." I took such statements to mean that we can see -- with great effort -- back to the time of galaxy formation, and that&nbsp; there is simply nothing to see beyond that.&nbsp; Nothing with structure enough to resolve in any case."</strong></p><p>As SpeedFreek mentioned, you really aren't wrong in thinking this way.&nbsp; You are using Time as a measure stick, however.&nbsp; But, lets fast forward 1 billion years.&nbsp; The universe is now 14.7 billion years old and we are still here on earth using the same telescopes.&nbsp; That same galaxy that was 13.2 billion years old is now 14.2 billion years old, but it has aged and evolved 1 billion years.&nbsp; At the same time, we should be able to see back in time to 14.2 years ago and see new galaxies forming.&nbsp; It's not they are any more 'new' than than the same one you saw a billion years ago, it just took an extra billion years for that light to show up because it was further away. </p><p><strong> Maybe it's a mistake on my part to think that we have seen back to the entire time of galaxy formation and have seen nothing past that simply because that is a time prior to galaxy formation and there are no galaxies to be seen."&nbsp;</strong></p><p>Not a mistake at all.&nbsp; We can't see past a certain <strong><em>time</em></strong>.&nbsp; We are, indeed, limited to how far we can see simply because the universe is so large.&nbsp; Light takes time to reach us. </p><p><strong>"It seems that by definition, we do not know that such galaxies exist because we cannot see them.&nbsp; I suppose that current theory holds that the conditions were right for galaxy formation at a time which we have not yet observed and so galaxies were formed that we cannot yet see?"</strong></p><p>Again, you are using time as a measuring stick.&nbsp; The Universe is presumed to be larger than our observable universe.&nbsp; The logical leap, considering homogenous nature of the observable universe, is that there are galaxies (galaxy clusters is more precise as at these distances we don't have the resolution to make out individual galaxies) that we can not yet see because light simply has not had the time to reach us yet. </p><p><strong>"</strong><strong>Or could it be that the region that currently lies between 40 and 62 billion light years away is from a time and space before the era of galaxy formation?"</strong></p><p>No.&nbsp; Light from this region is simply too far away from us and hasn't had the time to reach us, but it will.&nbsp; The universe just hasn't aged enough yet.&nbsp;</p><p><strong> Also, in another discussion on SDC, I think the consensus (here) was that the expansion of space "slid" past any matter occupying that space.&nbsp; if so, it seems that a large part of that 40 to 62 billion light year region would be occupied by expanded space but no matter -- at least at the scale of galaxies. Edit: After thinking, the expanding space would slide past the gravitationally bound galaxies in a cluster, but not past the clusters themselves."</strong> &nbsp; &nbsp; <br /><br />The Universe is thought to be homogenous in that galaxy clusters are evenly distributed throughout the entirety of the Universe.&nbsp; As for the question from the other thread, I don't think that can be answered until we understand the mechanisms behind the expansion and acceleration. </p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[Boris_Badenov]

<font size="2"><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>How much universe can we see compared to how much we think there is? <br />Posted by cosmicdustbunnie</DIV><br /><br /></font><div><font size="2">The size of Universe take a tour..</font></div><div><font size="2">http://www.youtube.com/watch?v=iZJb6yFDKIw&feature=related</font></div><div></div><div><font size="2">Millennium Simulation: "The Largest Model of Our Universe"</font></div><div><font size="2">http://www.youtube.com/watch?v=W35SYkfdGtw&feature=related</font></div> <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The size of Universe take a tour..http://www.youtube.com/watch?v=iZJb6yFDKIw&feature=relatedMillennium Simulation: "The Largest Model of Our Universe"http://www.youtube.com/watch?v=W35SYkfdGtw&feature=related <br /> Posted by boris1961</DIV></p><p>Nice ones Boris... I hadn't seen either of those yet.&nbsp; I've always been a fan of the old powers of ten video.&nbsp; Rather dated, but still effective whenever I need to reminded how insignificant I am (more so than I already am).</p><p>http://www.youtube.com/watch?v=BBsOeLcUARw&feature=related</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[majornature]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>That was kind of my thinking, if I read your response right. With the universe expanding, there is no real way to see the end because the protons we see now are billions of years old with billions of years of expansion still occuring.&nbsp; <br />Posted by bearack</DIV></p><p>Exactly.&nbsp; And by Earth and it's inhabitants being a speck in this Universe, we'll never know it's true age or size.&nbsp; It's seem the farther we can look, the faster the universe seem to expand.</p> <div class="Discussion_UserSignature"> <font size="2" color="#14ea50"><strong><font size="1">We are born.  We live.  We experiment.  We rot.  We die.  and the whole process starts all over again!  Imagine That!</font><br /><br /><br /><img id="6e5c6b4c-0657-47dd-9476-1fbb47938264" style="width:176px;height:247px" src="http://sitelife.space.com/ver1.0/Content/images/store/14/4/6e5c6b4c-0657-47dd-9476-1fbb47938264.Large.jpg" alt="blog post photo" width="276" height="440" /><br /></strong></font> </div>