Cosmic Microwave Background Radiation

[SLOW6]

<p>&nbsp;</p><p>NB to MODs, I Accidentally posted this thread in&nbsp;the 'Lounge' area... Sincerely Sorry! Had too many tabs open and made the mistake. Please delete that thread if possible&nbsp;</p><p>Hey guys, I have another question. Bare with me on this one. I have posed the question at the end of a few statements that I am working with in my head. I've numbered them so they can be referenced easily if there's something im missing or have misunderstood. </p><p>1) So from my understanding, our strongest and most powerful telescopes (hubble?) have imaged 'embryonic' galaxies 13.7+ billion light years away on the far edges of our visible Universe.</p><p>2) If we try to peer any further we only pickup what's known as Cosmic Microwave Background Radiation. This radiation is what is left over from&nbsp;the big bang, and we can NEVER hope to see past this point. Just off on a tangent a little here. I've read that apart from the total gravity of the universe guesstimate equation or whatever you'd like to call it, that the CMB is also in confirmation with an Infinite Universe and not a Finite Universe that curves back in on itself. I'm pretty sure I read that they mapped the CMB to a certain degree to try and search for any 'mirror' images of parts of the CMB to discredit the Finite Universe theory? </p><p>3) Now im pretty sure that this veil of radiation is the same in all directions, implying we are in the centre and that the radius of roughly 14billion light years is the limit before we hit the radiation. </p><p>4) Now&nbsp;I&nbsp;HAVE&nbsp;got my head around the fact that it may SEEM like we are in the centre of the universe due to the CMB surrounding us in all directions at roughly the same distance, but it is in fact our own cosmic bubble. Im also following the lines that a person or race on an alternate planet elsewhere in the universe is at the centre of&nbsp;THEIR own Visible Universe.</p><p>5) I've also been told that the visible Universe from our 'bubble' isn't special in any way shape or form. That its just like a horizon view on a ship at sea, that the person can only view a certain and equal distance in each direction but there's nothing 'special' about that circumference of vision. In fact if we were able to teleport to the edge of our bubble then we would be revealed with a further 14+billion light years of galaxies and stars, and if teleported to the edge&nbsp;again, the same, and so on and so on...</p><p>So my question, I guess, IS... How can the CMB be cause by the Big Bang that if we DID reach it, it would just jump out a further 14billion light years???? Also, is it fair to assume that even if there was a cosmic bubble in the Universe lying 50billion light years away that was teaming with life, we would never hope to be able to see it unless our cosmic bubbles passed through each other? Could it be something more simple but difficult to understand such as Light having a limit to the distance it can travel? I know its a constant but im just throwing it out there... Sorry if im not making sense! haha...</p><p>And (HERES THE BIG ONE)... how come its possible to look back 14billion light years and see galaxies in their 'embryonic' stages at the dawn of their existance etc (as though were looking back in time) WHEN, IF we teleported to that point there would be more and more visible universe from that point? It contradicts itself to me. CMB with young galaxies = the beginning yet if we went there, the universe would continue and there would be more galaxies and stars??? ARGHHHHH!!!!!!</p><p>Thanks </p> <div class="Discussion_UserSignature"> <strong><em>In an infinite Universe, any point can be said to be the centre as there are an infinite number of stars either side of that point... </em></strong> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>1) So from my understanding, our strongest and most powerful telescopes (hubble?) have imaged 'embryonic' galaxies 13.7+ billion light years away on the far edges of our visible Universe.</DIV></p><p>I believe recently, a young, protogalaxy was imaged at about 13 Gly (billion light years) distance.&nbsp; In other words, from the time the light was emitted by the galaxy to the time it reached the HST, it took 13 Gyr (billion years). </p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>2) If we try to peer any further we only pickup what's known as Cosmic Microwave Background Radiation. This radiation is what is left over from&nbsp;the big bang, and we can NEVER hope to see past this point. Just off on a tangent a little here. I've read that apart from the total gravity of the universe guesstimate equation or whatever you'd like to call it, that the CMB is also in confirmation with an Infinite Universe and not a Finite Universe that curves back in on itself. I'm pretty sure I read that they mapped the CMB to a certain degree to try and search for any 'mirror' images of parts of the CMB to discredit the Finite Universe theory?</DIV> </p><p>The CMBR was emitted when the observable universe was about 380,000 - 400,000 years old.&nbsp; Prior to that, the observable universe was considered opaque due to its density.&nbsp; The photons being created had no where to travel.&nbsp; They were constantly being absorbed, emitted and reabsorbed unitl the density was low enough for them to escape.&nbsp; This is referred to as the 'surface of the last scattering'.&nbsp; The surface of the last scattering is considered to be the wall that we can never peer past.&nbsp; However, it is also theorized that there should be a cosmic neutrino background that would have been emitted approx. 2 seconds after the big bang.&nbsp;&nbsp; That energies of the neutrinos would be so low coupled with the fact that neutrinos are notoriously difficult to detect, it's not likely we will detect this background radiation anytime soon... if it even exists.</p><p>The mirror imaging your are referring to is the 'cosmic hall of mirrors' effect.&nbsp; Basically, if there is a curvature to the topology of observable universe, then it could very well be smaller than it appears and some of these distant galaxies are simply younger versions of galaxies that are much closer to us.&nbsp; Essentially, the light emitted by these galaxies have had time to circumnavigate.&nbsp; I believe there have been some recent studies and observations within the last year or so that have placed major constraints on this.&nbsp; Though not completely ruled out, it's not very likely.</p><p>You are correct that interpretations of the CMBR have the observable universe being flat or very nearly flat.&nbsp; If it is, indeed, flat, this would imply an infinite universe.&nbsp; If there is a slight positive curvature to it, it is probably so small that it wouldn't be detectable.&nbsp; Sort of like detecting the curvature of the earth observing no more than a football field. </p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>3) Now im pretty sure that this veil of radiation is the same in all directions, implying we are in the centre and that the radius of roughly 14billion light years is the limit before we hit the radiation.</DIV></p><p>On the very largest scales, the CMBR and ultimately, the observable universe is said to be homogenous and isotropic.&nbsp; However, there are anisotropies on smaller scales.&nbsp; The Wilkenson Microwave Anisotropy Probe (WMAP) has detected these.&nbsp; </p><p>This radiation is ubiquitous throughout the observable universe.&nbsp; The photons have been travelling about since the observable universe was about 380,000 - 400,000 years old.&nbsp; The CMBR is everywhere.&nbsp; It's not something we observe only at astronomical distances.&nbsp; Your radio picks it up... old analog tv pick it up.&nbsp; It was discovered using a radio telescope. </p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>4) Now&nbsp;I&nbsp;HAVE&nbsp;got my head around the fact that it may SEEM like we are in the centre of the universe due to the CMB surrounding us in all directions at roughly the same distance, but it is in fact our own cosmic bubble. Im also following the lines that a person or race on an alternate planet elsewhere in the universe is at the centre of&nbsp;THEIR own Visible Universe.</DIV></p><p>Correct... I believe this is referred to as the Hubble sphere or, simply, the Observable Universe.&nbsp; It's really no different than standing in Chicago and considering yourself the geographical center of the Earth.&nbsp; The same can be said for someone standing in Singapore, or anywhere for that matter. </p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>5) I've also been told that the visible Universe from our 'bubble' isn't special in any way shape or form. That its just like a horizon view on a ship at sea, that the person can only view a certain and equal distance in each direction but there's nothing 'special' about that circumference of vision. In fact if we were able to teleport to the edge of our bubble then we would be revealed with a further 14+billion light years of galaxies and stars, and if teleported to the edge&nbsp;again, the same, and so on and so on...</DIV></p><p>Indeed.&nbsp; This is referred to as the Copernican Principle.&nbsp; Our position in the universe is not unique or special in anyway. </p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>So my question, I guess, IS... How can the CMB be cause by the Big Bang that if we DID reach it, it would just jump out a further 14billion light years???? Also, is it fair to assume that even if there was a cosmic bubble in the Universe lying 50billion light years away that was teaming with life, we would never hope to be able to see it unless our cosmic bubbles passed through each other? Could it be something more simple but difficult to understand such as Light having a limit to the distance it can travel? I know its a constant but im just throwing it out there... Sorry if im not making sense! haha...And (HERES THE BIG ONE)... how come its possible to look back 14billion light years and see galaxies in their 'embryonic' stages at the dawn of their existance etc (as though were looking back in time) WHEN, IF we teleported to that point there would be more and more visible universe from that point? It contradicts itself to me. CMB with young galaxies = the beginning yet if we went there, the universe would continue and there would be more galaxies and stars??? ARGHHHHH!!!!!!Thanks <br /> Posted by SLOW6</DIV></p><p>You sure do pack a lot of questions into one post <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>In astronomy, you often see distances measured by redshift denoted as 'z'.&nbsp; An object at redshift z=2 has a light travel time of 10.3 billion years (Gyr).&nbsp; We see that object as it was 10.8 Gyr ago.&nbsp; As fast as light may travel, the universe is pretty darned big and light, with its finite speed, still takes time to reach us.&nbsp; When that object first emitted its light 10.8 Gyr ago, the universe was only 3.3 Gyr old.&nbsp; The objects distance from us was only 5.7 Gly distance from us.&nbsp; The reason it took 10.8 Gyr to reach us is due to the metric expansion of space and that object is now 17.1 Gly distance from us.&nbsp;&nbsp; Despite the observable universe being 13.7 gyr old, it is said to have a radius of 46 Gly or 92 Gly in diameter.&nbsp; (I used Ned Wright's calculator to get these figures).</p><p>The redshift of the CMBR is z=1100.&nbsp; Input that into the calculator I linked and you will see that this radiation was emitted very, very early in the universe when it was very close to us (we weren't around at this point, but our coordinates in space were).&nbsp; You will also notice that the current distance from us is nearly 46 Gyr.&nbsp; Considering we're seeing this radiation from all directions, that tells us it permeates all of space.&nbsp; It's one of the single, most definitive observations in support of the Big Bang theory. </p><p>You've got the right idea concerning 'cosmic bubbles passing through each other'.&nbsp; More precisely, our Hubble sphere expands into the expanding Hubble spheres of other distant objects.&nbsp; As long as this happens, their light will eventually reach us.&nbsp; IIRC, an object that is, currently, about 16 Gly distance from us is considered outside our observable universe.&nbsp; The metric expansion of space is such that our expanding Hubble spheres will never overlap and the light will never reach us.</p><p>I hope I covered everything and welcome to SDC. </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>

 

[SLOW6]

<p>Derekmcd : Cheers for the reply... I think im following you. I sort of figured out myself that, as you said, the light from the distant galaxies has pretty much nothing to do with (or resembles) the way they appear this very instant at that distance away. They would have matured by the amount of time it took for the initial light to get here. </p><p>So, is a good analogy of this cosmic bubble / CMBR veil, having say a torch in your hand and shining it into the distance. You can see to the edge of the light but thefurther forward you walk, the further back the edge of the light travels and you can never hope to get to the edge of that light? So in other words, no matter what we do... teleportation for eases sake or light travel, we will ALWAYS no matter what, be at the centre of our own personal observable Universe... a cosmic radius of radiation?</p><p>Its just hard to grasp that!As I said before my conundrum is still trying comprehend what and where the ACTUAL edge of the Universe really is. Surely if you could somehow teleport to the edge of each observable universe at say the speed of light for a long time, your going to come to an end sooner or later!! Sorry mate, its the biggest head f#$k ive always had! Infinity is just a word but the concept is impossible to grasp (for me anyway).</p><p>I guess the word 'Universe' has a few different meanings. Long ago I would have said that the Universe is all that is out there. Now it seems this has in a way changed. That there's the observable Universe with Cosmic Bubbles and not to mention the notion of other dimensions and alternate Universes...</p><p>Just out of interest, is it also true that the speed of light is not the fastest moving thing in the Universe... I believe that the expansion of the Universe itself MUST be faster than light or how could light exist without something being there to start with? Therefore, at the dawn of time when the big bang was about to occur, this tiny ball of pure energy wouldn't have had any colour or light source as the Universe did not exist yet and so how could light have shone? Im making this worse aren't I? I assure you im not trying to. </p><p>Thanks</p><p>G</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <strong><em>In an infinite Universe, any point can be said to be the centre as there are an infinite number of stars either side of that point... </em></strong> </div>

 

[SpeedFreek]

<p>A lot of what you are asking boils down to a simple question - how straight is a straight line?</p><p>On the surface of the Earth, if you draw a long enough straight line you end up back where you started. This is because your straight line is being drawn on a curved surface. So what if the universe were "curved" in the same way?</p><p>On a local level we think of the ground as being flat, but if we examine that ground at a large enough scale we notice it is part of a curved surface and the same might be true of the universe. The surface of the Earth is two dimensional, but that surface is wrapped around a three dimensional object - a sphere.</p><p>But what if we take this principle and step it up a dimension? What if the three spacial dimensions of our universe were "wrapped" around a fourth dimension? If that fourth dimension was perfectly flat then any straight line in our three spacial dimensions would continue to infinity, but what if that fourth dimension had some curvature? If our three spacial dimensions were wrapped around a four dimensional sphere, then any straight line across our universe would actually be part of a large curve and there would never be an "edge" to the universe, just as there is no edge to the surface of the Earth. </p><p>So far astronomers have thought of a few methods to look for evidence of curvature and have found that the observable universe seems to be within 2% of being flat. That 2% represents a margin of error, but also allows us the possibility that our observable universe is a very small part of a curved universe, where the radius of that curvature is far larger than our observable universe.</p><p>The accelerating rate of expansion means that light will never be able to "circumnavigate" the whole universe, but there remains the possibility that the path light takes through the universe is ever-so-slightly curved and that if we were able to follow that path, we would end up coming back to the origin of that path from the opposite direction, rather like the way that pac-man exits the videogame screen on one side and enters on the other.</p><p>This is just one of the possibilities.</p><p>To the question of light being the fastest thing in the universe, a key point to remember is that <strong>nothing ever overtakes a photon</strong>. Distant galaxies may recede from this point in space faster than light, but in their local area they could consider themselves to be at rest, just as we do here. From their point of view it would be our Milky-Way galaxy, seen as it looked billions of years ago, that is receding from <em>them</em> faster than light, but we are not overtaking photons here! </p> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[brellis]

<p>hi Speedy</p><p>Once again, you explain the cosmic stuff so very well.&nbsp; Thanks! </p> <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[SpeedFreek]

I think Derek deserves more applause for his post than I do for mine, but thanks for the thanks! <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-embarassed.gif" border="0" alt="Embarassed" title="Embarassed" /> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[brellis]

yes, I agree, sorry Derek! <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[neilsox]

<p>

&nbsp; or race on an alternate planet elsewhere in the universe is at the centre of&nbsp;THEIR own Visible Universe.5) I've also been told that the visible Universe from our 'bubble' isn't special in any way shape or form. That its just like a horizon view on a ship at sea, that the person can only view a certain and equal</p><p>Unless the theory has changed, the Universe is receding from us at the speed of light, 13.8 billion&nbsp;light years away, so we can't know what is beyond, and won't know later as light coming our way from 13.8 billion light years will never arrive, unless the&nbsp; universe changes from expansion to big crunch = thought unlikely. There could, therefore be lots of universe beyond 13.7 light years in some directions and very little in other directions. We are likely 13,7 light years or more from an edge, but possibly not close to the center. In some geometries, the Universe has neither center nor edge, but I can't claim to understand that.&nbsp;&nbsp; Neil</p>

 

[SpeedFreek]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Unless the theory has changed, the Universe is receding from us at the speed of light, 13.8 billion&nbsp;light years away, so we can't know what is beyond, and won't know later as light coming our way from 13.8 billion light years will never arrive, unless the&nbsp; universe changes from expansion to big crunch = thought unlikely. There could, therefore be lots of universe beyond 13.7 light years in some directions and very little in other directions. We are likely 13,7 light years or more from an edge, but possibly not close to the center. In some geometries, the Universe has neither center nor edge, but I can't claim to understand that.&nbsp;&nbsp; Neil <br /> Posted by neilsox</DIV></p><p>You almost got it right (current theory), but the horizon where on object is receding from us at the speed of light (the Hubble Distance) is not a barrier that stops us seeing any further. Consider that, to a galaxy just beyond that conceptual barrier, the space around it acts pretty much like the space around our own galaxy. Nothing is moving at the speed of light there, except for light itself and the light from that distant galaxy can easily start heading in our direction.</p><p>If the light from a distant object beyond the Hubble distance is close enough to that horizon, it will easily cross it and we will eventually see it.</p><p>The horizon you are looking for is the "cosmological event horizon". Here, any <span style="font-style:italic">light</span> that has been emitted in our direction is receding from us at the speed of light. The light itself is moving away at the speed of light and will never reach us, due to the acceleration of the expansion of the universe.</p><p>The cosmological event horizon is currently thought to be around 16 billion light years away and we will never see any event that happens <em>now</em>, if that event happens at a distance further than 16 billion light years away.</p><p>Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe</p> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>