Question about expansion & the age of the universe...

[six_strings]

I really have two questions here, but I don't to be accused of spaming or pushing out other peoples posts...<br /><br />1) If the universe is expanding faster then light speed, how is it we can see <b><i>any</i></b> distant objects?<br /><br />2) If the most distant objects we observe are 13 billion light years away, how could the object get that far away from us in only 750 million years? wouldn't the object have to be going faster then light also?<br /><br /><br /> <div class="Discussion_UserSignature"> </div>

 

[six_strings]

Another thing I wonder about is if we were to hypothetically be able to travel 99% the speed of light towards this object, if the expansion is so fast that even as we travel towards this object it is still receding, we could never actually reach it? Would it just appear like a carrot (not actually a carrot, heh) being dangled in front of us?<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[six_strings]

On my second question there I understand that you might say the object <b><i> itself </i></b>is not travelling that fast but empty void (space) is propagating between us, to make it appear to be travelling away from us... But, wouldn't the light or radiation still have to cover this distance? <br /><br />And what the heck could be <b><i> making </i></b> space itself? And if that is the case, wouldn't that mean that empty space actually is <b><i> something </i></b> tangible?<br />There must be an inside and outside to our universe?<br /><br />And, if there is an <b> outside </b> to our universe, that really makes the mind boogle! <img src="/images/icons/smile.gif" /><br /><br />Very puzzling for me.... <div class="Discussion_UserSignature"> </div>

 

[alokmohan]

Faster than light travel is absurd.Not permitted as per general theory of relativity.

 

[six_strings]

Very True Alokmohan, <br />How do you explain the furthest known galaxy at 78 billion light years away, and the age of the universe is only 13.7 (approx) billion light years old? Observations suggest space is propagating faster then light, if I understand correctly. That's what these two questions are about... Not really faster then light <b><i>travel</i></b>... But rather, if the gap is widing between us so fast, how can we even observe these far objects?... <div class="Discussion_UserSignature"> </div>

 

[lukman]

True, I never got a reasonable explanation. Yes space expand greatly makes matter seemed to move away FTL, but all the distance and age of universe do not sound right to me. <br /><br />For instance: Object seen at 13.5bly when it was 750million years old, and they are now 75bly away, so think and think... 750million years after big bang, matters were away 13.5bly by their own speed and space expansion. Instead of slower, around 13billions years later, matters manage to put on extra 62bly. So, if scienctist suggest that our universe is still accelerating away from each other.... few million km/hours is insignificant. Are the speed already counting space expansion?<br /><br />Very confusing, and the answer (like always) : we can not look at the universe in 3D, it has to be />3D....<br />So, we are living in 3D world, why would scientist gave us those number that actually cannot be used in 3D way. <div class="Discussion_UserSignature"> </div>

 

[lukman]

The 13bly objects that we observed are now around 78bly away due to expanding universe. The informations can be otained by many sources. Infact scientist proudly announced that our universe is 78bly+78bly wide. <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

The 78 billion ly figure is termed the <b> comoving distance </b>.<br /><br />It is the estimate of the true distance to the objects at the edge of our observable universe. We see them 13.5 billion ly away, but thats where they were 13.5 billion years ago. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[lukman]

But rather, if the gap is widing between us so fast, how can we even observe these far objects?...<br />- True, that is why we can not see the object further than the age of the universe, i.e. our universe is 15billion years, so, we can only see object with distance <15billion light year which are actually our very early ages of the universe, and so called "comoving distance" -) has moved them to around 75bly away. <div class="Discussion_UserSignature"> </div>

 

[six_strings]

In reply to all,<br /><br />So, it really does boggle the mind, doesn’t this still leave the question of how the far objects/galaxies got some 13 bil LY’s in only 75 mil LY’s? (Or 2 bil LY’s, depending on the model you use) <br /><br />Inflation? That is a crazy amount of space if that’s the explanation… <br /><br />So, what would happen if we tried to venture to these far galaxies? The horse and carrot?<br /><br />Also, does anyone know what this rate of expansion is? They must be able to measure this if they can estimate the distant galaxies at 78 bil LY’s… Why isn’t this “expansion’ observable or apparent in our local area? Where is it coming from??? <br /> <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

You haven't quite understood it correctly <img src="/images/icons/smile.gif" /> For simplicities sake, I will use one set of figures which of course may or may not be correct, but it will do to show the principle. Also, understand that although these are the most popular theories that tie in with our observations, but they may not be correct. There are other theories that can be considered just as valid.<br /><br />The furthest objects we see are estimated to be 13.5 billion light years away. But we are seeing those objects as they were only a relatively short while (75 million years) after the universe began. They are some of the earliest large scale objects in the universe. Their light is the oldest light we can see.<br /><br />Where you may be misunderstang is that, we are <i> now </i> around 13.5 billion light years away from where those objects were when the light we see left those objects 13.5 billion years ago. The light took that long to reach us.<br /><br />Our position in space was a lot closer to them when the light left them (75 million years after the universe began). The universe was a lot smaller then. But it has taken 13.5 billion years for their light to catch up with us, so we can say we see them as being 13.5 billion light years away. (Note the difference between years and light years). But although it is what we observe, it is an illusion of sorts.<br /><br />We estimate that those objects are <i> now </i> 78 billion light years away. So they must have moved away faster than the speed of light, to move an extra 63 billion light years in only 13.5 billion years.<br /><br />Also remember, as they are moving away from us, we are moving away from them. So someone in one of those distant galaxies would see themselves in the centre of their observable universe, with galaxies all around, just like we do. If they were looking in our direction <i> now </i> they would see us at the edge of their observable universe, 13.5 billion light years away. But we are now 78 bil <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[newtonian]

speedfreek - excellent explanation/post.

 

[newtonian]

six_strings - Yes, there could be an outside to our universe.<br /><br />How many mutually exclusive light cones were created at inflation stage?<br /><br />One model/hypothesis I have considered (independently):<br /><br />Our visible portion of universe is being 'pulled' by FTL matter in FTL light cones, aka visibility horizons, by a domino effect.<br /><br />In this model, while the light cones would be mutually exclusive like too distant dominoes, there could be cause and effect by a domino effect by overlapping light cones in between, like dominoes in between the too distant dominoes.<br /><br />In this model, acceleration of expansion is caused by perhaps ordinary gravity from FTL matter from FTL light cone portions of our universe (hence from beyond our visibility horizon).<br /><br />In effect, FTL matter pulling us by gravity tending to have us catch up.<br /><br />This could be by dark energy from FTL matter, btw.<br /><br />Either way, we could also be observing effects from outside of our universe.<br /><br />Or, for another example, we could be expanding within a much larger universe whose gravity or dark energy is causing acceleration of expansion.<br /><br />I have also noted someone posted a link on some uneveness involved. This could be caused by multiple universes also within said larger universe.<br /><br />Just scientifically speculating, btw. <br /><br />It would be nice if I hit on something accurate, btw!

 

[weeman]

What Speedfreak was saying about inflation sounds right to me. The cosmic inflation would have occured in fractions of a second, possibly within the first 10^-35 seconds after the initial big bang! <br /><br />When we see galaxies at vast distances, they show strong red shifts. Their spectrums are so far red-shifted, that it appears they are moving faster than the speed of light. However, no matter can move faster than the speed of light, correct? Well, its not necessarily the matter itself that is traveling faster than light, but rather the space between it that is traveling at extreme velocities. So, it is possible that the space between the matter in the Universe is expanding faster than the speed of light. I used a simple analogy to explain this in another thread, I will state it again.<br /><br />Lets say you are baking a loaf of bread with raisins in it (in this analogy the raisins will represent galaxies). You toss the dough into the oven, and when it comes out, the raisins will have appeared to move further apart due to the expansion of the dough. From a raisins viewpoint, it didn't necessarily move anywhere, but rather the dough between it and its neighbor pushed them apart. <br /><br />So what might be the speed limit for the expansion of the Universe? Who knows, there may not be a limit. If anyone has an answer to question please post it <img src="/images/icons/smile.gif" /> <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>

 

[metalmind]

FOR YOUR 2ND QUESTION..... IF AN OBJECT IS 1 BILLION LIGHT YEARS AWAY, IT TOOK 1 BILLION YEARS TO GET THERE . 1ST QUESTION..... YOU CAN SEE AN OBJECT IN SPACE THAT IS 1 BILLION LIGHT YEARS AWAY BECAUSE, THE LIGHT THAT YOU SEE IS 1 BILLION YEARS OLD, IT TOOK 1 BILLION YEARS FOR THE LIGHT TO GET HERE. WHEN THE BIG BANG HAPPEN, AND THINGS BEGAN TO COME TO SHAPE, THESES LIGHTS THAT STARTED SHINING KEPT SHINING FOR 1 BILLION YEARS, SO THE LIGHT THAT YOU SEE IS 1 BILLION YEARS OLD. PLEASE REPLY, METALMIND

 

[weeman]

I too have trouble with the thought that distant objects might be moving faster than light. If they are indeed moving faster than light, then it would mean the Universe is a lot younger than we think it is. <br /><br />Lets say we see a galaxy 4 billion lightyears away. If it were traveling at the speed of light, we could conclude that its actual distance might be around 8 billion lightyears. However, if the expansion of the Universe were causing it to exceed the speed of light, then it could be 10 billion lightyears away, or 20 billion, or 50 billion. <br /><br />So, then you might say that the Universe is only 750 million years old, and since the expansion is propelling it faster than the speed of light, it takes what appears to be 14 billion years for the light to reach Earth. <br /><br />However, this idea is severly flawed. If light had to travel a distance of 14 billion lightyears to reach us, and the Universe is only 750 million years old, that light would have had to have left those galaxies before they even existed, before the Universe even existed.<br /><br /> <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>

 

[weeman]

Tigerbiten, <br />I see what you're saying about the photon traveling against the expansion of the Universe. So this certainly would mean that it takes longer for the photon to reach us in an expanding Universe than if it were traveling in a non-expanding Universe; correct? <br /><br />Wouldn't this mean that the Universe is a lot older than we think? If light were traveling through a static universe (non-expanding), then it would take the actual 14 billion lightyears to reach us. However, in an expanding Universe, with your idea that it's traveling against the expansion, then it would take longer than 14 billion years to reach us.<br /><br />The fact that we can see the light from the Universe certainly has to mean that it can't be expanding faster than light. Lets say the expansion is equal to the speed of light, then the photon should never be able to reach us, because the expansion directly equals its speed.<br /><br /> <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>

 

[weeman]

So then what would happen if you were to travel beyond 1.7 billion lightyears? According to the distance of megaparsecs relative to our location in the cosmos, you should technically break the speed of light beyond 4,222 megaparsecs.<br /><br />We would never be able to see galaxies that are actuallly at a distance that is geater than 1.7 billion lightyears from Earth, because the expansion would be greater than the speed of light. This would have to mean that the Universe is expanding. All galaxies that appear 14 billion lightyears away, were actually at a distance that is less than 1.7 billion lightyears from Earth when the light left them. <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>

 

[weeman]

Actually, in reply to my own post, I was thinking that what I said might not actually be true.<br /><br />I said that light that appears to be 14 billion lightyears away might have actually been at a distance less than 1.7 billion lightyears. However, wouldn't it mean that the objects were actually at a distance of 14 billion lightyears when the light left them? We can theoretically come up with accurate distances using cepheid variables. If cepheid variables can certainly give us accurate calculations, then objects that are at 14 billion lightyears were actually at that distance when their light left. This would mean that if they were indeed 14 billion lightyears away, and the Universe is expanding, the objects we see could very well be over 100 billion lightyears away when the light finally reaches us! Or maybe even far more than that; who knows?<br /><br />However, like I said in my previous post; how could we see them if they were actually at a distance of 14 billion lightyears? If 1.7 billion lightyears from Earth means that the expansion is equal to the speed of light, how could we see something that is at 14 billion lightyears? This would almost have to mean that the expansion tops out at slightly less than the speed of light, and these objects that we see at 14 billion lightyears have taken a very very very long time to reach Earth.<br /><br />Well, I said it, and now I have a headache from this thought <img src="/images/icons/smile.gif" /> <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>

 

[smythet]

My first post and thinking out loud here, so please bear with me on this...<br /><br />At the time of the Big Bang (BB), laws of physics (as we understand them) did not function properly. Thus, measuring distances / intervals during some period following the BB would be difficult, at best. The gravity well would have been so large that, according to known physics, nothing could have escaped it. But, of course, it did. We're here. So, something that defies physics explodes and allows the universe we're in to exist.<br /><br />With regards to the acceleration of matter away from us, could it not be explained simply as measuring the initial velocities of matter following the BB? For instance, when a bomb goes off, the matter fllies away from the blast with the highest velocities in the first few moments. Since we're looking "a great distance" back in space/time, would not those "moments" also yield the highest velocities? <br /><br />Could it be that when we peer deep into space/time and gleen bits of information from the barely visible images of our beginnings, we're assuming the matter we're seeing has accelerated "out of sight"? <br /><br />Would it more likely be that the images we're seeing are the red-shifted rays of energy being slowed by our own galaxy - looking through the back of the picture, so to speak?<br /><br />Could it be possible that the deeply red-shifted images are simply the first pictures of the early matter beginning to slow and start the long spiral back toward that singularity we identify with the BB?<br /><br />The further we look into the universe, the faster things seem to move away from us. To me, this makes perfect sense since we're looking back in time and getting closer to era of the BB. Things "should" be moving away from the event faster than they are today - and this is what we're seeing.<br /><br />It also makes sense that when looking that far back in time over those great distances, we have no idea what's happening "out there" today because we h

 

[alokmohan]

We see distant things when they were in past era.We cant know the present.Our knowlefge can know only upto this.

 

[smythet]

My point exactly.<br /><br />If we're to assume the images they've taken of matter/energy some 13.2B LY away are from a mere 750M years following the BB, then the origin of the BB must have been roughly 12.5B LY away from us (toward the objects in the images). Assuming the objects (and us) are flying away from the BB at near light speed and slowing over time, our view of the universe must be very egg-like in shape with our position somewhere near the larger end of center. Why?<br /><br />The matter blown away from us - on the opposite side of the BB - would have velocities greater than light and be invisible to us. Those particles would remain out of our field of view until such time as the sum of our velocities had reduced to sub-light and sufficient time passed to allow the light to reach us. Possibly tens or hundreds of billions of years.<br /><br />The matter/energy blown tangientially to our direction of travel would suffer the same visual consequences, but appear to us much sooner than matter opposed to us.<br /><br />The matter/energy blown most closely to our direction would either remain visible and somewhat redshifted if it were blown out before us, or blue shifted if it were blown out after us. This would be true of some of the near tangiential matter/energy, as well. But, not nearly so much as matter/energy coresponding with our blast direction.<br /><br />Angular velocity comes into play here, as well. Every object in the universe has spin and this was derived from the spin associated with the singularity (which must have been incredible!). Simply looking at redshift/blueshift and extrapolating a direction toward the center would miss the mark without angular velocity. So, our straight-line vision into the distances of space must take into account light bending around gravity wells (which we usually do not get to see) and distortions in redshift/blueshift caused by the big spin.<br /><br />Since our view of the universe is limited by the speed of light with regards

 

[Mee_n_Mac]

<font color="yellow"><i>"If we're to assume the images they've taken of matter/energy some 13.2B LY away are from a mere 750M years following the BB, then the origin of the BB must have been roughly 12.5B LY away from us (toward the objects in the images). Assuming the objects (and us) are flying away from the BB at near light speed and slowing over time, our view of the universe must be very egg-like in shape with our position somewhere near the larger end of center."</i></font><br /><br />Hmmm, there's something I don't think you're understanding but I don't know if I've got the right words to explain it better. Let me start with the ~12.5B LY above. I presume you got this by subtracting the 0.75BY from the 13.2B LY. But that's not the way to understand it. Let me use a too simple analogy to make the underlying point. Say you start out on a walk to a neighbors house and it's 1 mile away. You walk at 1 mile an hour. You'd expect to arrive 1 hour after you start. But someone pulls a fast one on you and they stretch the distance and the road as you are walking. By the time you get to your neighbor's house it's been stretched so it took you 10 hours to make the trip. You could say the trip distance was 10 walk-hrs and still have the original distance be 1 mile from you. 1 second after you started your trip you were still about 1 mile away and yet it took you 10 hrs to complete the trip. Mebbe I better stop here.<br /><br />Second there is no single "center" of the Big Bang (as goes the theory). You, right now, are at the center of your Big Bang. You look out and everything is running away from you. Some alien on a planet 5B LY from us is also at the center it's BB. Everything it sees is running away from it. Our 2 observable universes overlap to some degree and yet you get to see things he can't and visa-versa. No doubt there's a website with pictures and diagrams and better words then I've used. Perhaps someone else might provide a link.<br></br> <div class="Discussion_UserSignature"> <p>-----------------------------------------------------</p><p><font color="#ff0000">Ask not what your Forum Software can do do on you,</font></p><p><font color="#ff0000">Ask it to, please for the love of all that's Holy, <strong>STOP</strong> !</font></p> </div>

 

[SpeedFreek]

You talk about an "origin of the Big-Bang". If BB theory is correct then this is not a specific position inside our universe. If the <i> whole </i> universe was created from the Big-Bang, then the whole universe was once at the "point of origin". How can any point inside that universe be deemed to be the point of origin?<br /><br />When we look towards the edge of our visible universe, in <b> any </b> direction, we are looking towards the Big-Bang. The <i> beginning </i> of time and the universe is in every direction outside our visible universe, and the only place that is <i> now </i> is here on Earth, in the centre of our visible universe. Everywhere we look, we look back in space and time, towards the direction of the beginning.<br /><br />Now I'm repeating myself so I will shut up! <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[smythet]

If the "rubber space" theory is true, at what point does it become impossible to traverse our planet, let alone travel to the nearest star? That should be calculable. After all, the expansion rate grows with distance and this growth rate is stretching the existing space from "here" to "there". At some point, our planet - which is being stretched in every direction at the same rate/time - is growing larger and larger (and so are we - wow, giants, or maybe we already are?).<br /><br />Also, the stretching is occuring more rapidly here than it is for someone on another planet in another galaxy - possibly even at or beyond the speed of light (we're each seeing the same thing from "our" positions, right?). <br /><br />If it's true.<br /><br />But, then again, this all sounds like space within an event horizon - not following the laws of physics at all. And yet, we have things here on Earth and within our neighborhood that do follow those laws. Interesting...<br /><br />tom