How can we see light from very early stars? Shouldn't it have passed us already?

rdsspam · Mar 13, 2008

Hello all,  This has been bugging me for a while, so I hope someone can clear this up for me... http://news.nationalgeographic.com/news/2007/07/070710-first-stars.htmlIn the above story, and many others like it, astronomers talk about seeing light from the very beginning of the universe, 13+ billion years old and 13+ billion light years away. So, if that was near the beginning, and in the beginning all matter (including what would in 13+ billion years become us) was concentrated over a lot less distance than it is now, how is it that the light is just reaching us now?  For us to see it, light has to travel toward us so how did we get in front of the light from our own 13 billion year old past? Thanks! -Richard.

SpeedFreek · Mar 13, 2008

Check out this link - The Distance Scale of the Universe.You are correct - it is theorised that when the galaxies first formed, our observable universe was a lot smaller than it is today, and so those most distant galaxies would have been a lot closer to this point in space (where our galaxy formed) at the time.The thing is, the universe was expanding at a huge rate, early on in its history. So although a galaxy at the edge of our observable universe may have been only 1 billion light years away when it emitted the light we are now seeing, that light was travelling through space as the universe expanded and so the distance to here was increasing too and it took that light 13 billion years to get here. That distant galaxy is theorised to be something over 25 billion light years away, now.   <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

Saiph · Mar 14, 2008

A short way of thinking about it is: Current evidence points towards the universe being 13 billion years old.  So any light from an object 13 billion ly away, has to be some of the earliest light from the earliest sources. Some of thier light has already passed us, but we are still getting some. If expansion is correct (and I put my weight behind it) the sources are actually further than 13 billion ly, as speedfreek mentioned.  <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

qso1 · Mar 18, 2008

On a much smaller scale, consider the star betelguese. We see its light because it continuously emits light. But one day it is expected to go supernova and become a nebula. It is possible that event happened already, perhaps 300 years ago. But the light from that event is still enroute and won't reach us for another century if the roughly 400 light year distance for the juice figure is accurate.Now its just a matter of applying that to the larger scale Universe.  <div class="Discussion_UserSignature"> My borrowed quote for the time being:There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened. </div>

tdmikey · Mar 18, 2008

How did they figure that our universe is moving faster than light in the first place?   With the link it seems to annotate for the first 10 billion years we were moving faster than light.  Then it so called "caught up" to us.  My opinion is the light was continuously hitting us (and still is) as we were moving further apart. <div class="Discussion_UserSignature"> "But you cant stop nothing, if you got no control, of the thoughts in your mind, that you kept and you know. You dont know nothing, that you didnt need to know, the wisdom's in the trees, not the glass window." "Breakdown" by Jack Johnson </div>

SpeedFreek · Mar 18, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>How did they figure that our universe is moving faster than light in the first place?   With the link it seems to annotate for the first 10 billion years we were moving faster than light.  Then it so called "caught up" to us.  My opinion is the light was continuously hitting us (and still is) as we were moving further apart. Posted by tdmikey</DIV>Let me illustrate how the metric expansion of the universe works.Imagine a volume of space (don't worry about the edges of the volume, it is actually irrelevant!). Now fill that volume with a 3 dimensional grid of points, all 1 meter apart from each other. Whatever point you put yourself upon, whether you look up, down, left, right, backwards or forwards, you see points at 1, 2, 3, 4, 5 (and so on) meters away from you in each direction.Now, taking 1 second, expand that volume of space to twice its original size and imagine that the grid of points expands with the volume. So after 1 second, you now have points that are 2, 4, 6, 8, 10 (and so on) meters away from you in each direction. The distance between each point took 1 second to double.So, the nearest point from you moved from 1 to 2 meters away whilst the point that was 5 meters away moved to become 10 meters away, all in the same amount of time. So the nearest point receded from you at 1 meter per second, whilst the 5th point away receded from you at 5 meters per second.If you think about it, if the volume is large enough, a point at a certain very large distance from you will have receded from you at 300,000,000 meters per second, which is around the speed of light! Any points more distant than that will have receded from you faster than light!But remember, none of those points moved through the space in that volume, the space expanded and the points "lodged" within it were drawn further apart by that expansion.This is a very simplified example of how the metric expansion of the universe works. I used a single rate of expansion where distances doubled in 1 second, but we think the rate of expansion has been changing throughout the universe's history - very fast at the beginning (where distances at the microscopic scale were increasing at the speed of light) and decelerating until around 6 billion years ago, when it seems the expansion started to accelerate. Now, the rate of expansion was extremely fast when the observable universe was very small, and right from the start the edge of our observable universe was receding from this point in space at a rate that is apparently faster than the speed of light.By the time that galaxies formed, it is theorised that our observable universe was at least 1 billion light years in radius. So the light from a galaxy that formed right on the edge of our observable universe started its journey over 13 billion years ago, but only reaches us today. Yes, some of that light may have already passed us, but when the galaxy formed it was over 1 billion light years away, so in a static universe it would have taken 1 billion years before we even saw that galaxy.But the universe is not static, so the light from those most distant galaxies has taken most of history to reach us.Also, from the point of view of one of those galaxies, our galaxy (or whatever was here over 13 billion years ago) is at the edge of their observable universe, and we seem to be receding from them at superluminal speeds! <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

weeman · Mar 18, 2008

Speedfreek: Also, from the point of view of one of those galaxies, our galaxy (or whatever was here over 13 billion years ago) is at the edge of their observable universe, and we seem to be receding from them at superluminal speeds! That's what I've often wondered. Isn't it deceiving to say that the distant universe is actually receding from us at more than the speed of light? Because then it gets newcomers in the study of astronomy asking: How can it recede at more than the speed of light if all physicists say that nothing travels faster than light? As it appears to our most distant galaxies, it is us who are receding at more than the speed of light, not them. So how can we say that the distant galaxies are receding at more than the speed of light? It only appears that way due to the metric expansion of space as implied in your model. <div class="Discussion_UserSignature"> Techies: We do it in the dark. "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." -Albert Einstein </div>

SpeedFreek · Mar 18, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Speedfreek: Also, from the point of view of one of those galaxies, our galaxy (or whatever was here over 13 billion years ago) is at the edge of their observable universe, and we seem to be receding from them at superluminal speeds! That's what I've often wondered. Isn't it deceiving to say that the distant universe is actually receding from us at more than the speed of light? Because then it gets newcomers in the study of astronomy asking: How can it recede at more than the speed of light if all physicists say that nothing travels faster than light? As it appears to our most distant galaxies, it is us who are receding at more than the speed of light, not them. So how can we say that the distant galaxies are receding at more than the speed of light? It only appears that way due to the metric expansion of space as implied in your model. Posted by weeman</DIV>You are exactly right. Nothing actually moves through space faster than light, which is why I always try to use terms like "apparently receding" or "seem to be receding".Nothing can move across the geometry of space faster than light, but the geometry of space can stretch over time in such a way that objects that are "at rest" within their local frame of reference will calculate that objects distant from themselves have apparently receded from them faster than the speed of light.

<div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

tdmikey · Mar 19, 2008

Is there any proof that “new ancient light” has been found?  That is now catching up to us.  I know that we will be able to see more with the newer telescopes than what we have had but that doesn’t mean that the light wasn’t there.  It is just saying that we can now see further.    I understand the possibility that both the distant galaxy and our galaxy are receding away from each other at a velocity that is faster than C.  I am just trying to think out of the box.  What if the universe was just spinning and not expanding like galaxies spin?  Has every object been verified to be receding away from us?  How can this be true if we have galaxies out there now colliding into each other?  And we are supposed to be colliding into another galaxy in umpteen million years.  Wouldn’t that disprove the logic that all objects are receding  away from each other?  So we can look back in time to the early universe, if we get back to the starting point do you think that we will be able to see the “big bang” theory?  Or do you think we will see a big quasar that’s spitting out material for new galaxies?    Sorry bout all the questions.  Mike"But you cant stop nothing, if you got no control, of the thoughts in your mind, that you kept and you know.  You dont know nothing, that you dont need to know, the wisdom's in the trees, not the glass windows."  "Breakdown" by Jack Johnson <div class="Discussion_UserSignature"> "But you cant stop nothing, if you got no control, of the thoughts in your mind, that you kept and you know. You dont know nothing, that you didnt need to know, the wisdom's in the trees, not the glass window." "Breakdown" by Jack Johnson </div>

derekmcd · Mar 19, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Is there any proof that “new ancient light” has been found? Posted by tdmikey</DIV> Not that I am aware of.  Not to say that it hasn't happened, though.  The 'observable' universe is expanding daily.  That would lead be to believe new light should be visible.  The problem lies with the distances involved.  The next galaxy that should become viewable beyond the most distant current galaxy could still be thousands of light years further.  We simply haven't been around long enough to witness such an event.  It is, likely, though that the light from a 'new' galaxy would be too far redshifted to be seen. Replying to: <DIV CLASS='Discussion_PostQuote'>What if the universe was just spinning and not expanding like galaxies spin? Posted by tdmikey</DIV> Spinning relative to what?  A spinning universe implies there is an axis about which it rotates.  This has not been observed and may never be even if it is. Replying to: <DIV CLASS='Discussion_PostQuote'>Has every object been verified to be receding away from us?  How can this be true if we have galaxies out there now colliding into each other?  And we are supposed to be colliding into another galaxy in umpteen million years.  Wouldn’t that disprove the logic that all objects are receding  away from each other?Posted by tdmikey</DIV> So far... yes (at least enough to keep Hubble's law as a reasonable explanation).  Every galaxy cluster has been observed to be receding via the metric expansion of space.  Galaxies do collide and will continue to do so due to local gravity overcoming this metric expansion.  Andromeda is within the local gravity of the Milky Way (as are others) and is recognized to be blue shifted (getting closer).  Best guesses say the Andromeda galaxy may collide with us in about 3 billion years. Replying to: <DIV CLASS='Discussion_PostQuote'>So we can look back in time to the early universe, if we get back to the starting point do you think that we will be able to see the “big bang” theory?  Or do you think we will see a big quasar that’s spitting out material for new galaxies?Posted by tdmikey</DIV> There is a limit to what we can see when referring to the age of the Universe.  The Universe didn't become visible until about 380,000 years after the big bang when it expanded and cooled down enough for photons to scatter and begin their travels. Replying to: <DIV CLASS='Discussion_PostQuote'>Sorry bout all the questions. Posted by tdmikey</DIV> Welcome to SDC and don't ever stop asking questions.  You can never ask too many.    <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

tdmikey · Mar 19, 2008

Not to be a stickler but .... Replying to: <DIV CLASS='Discussion_PostQuote'> The problem lies with the distances involved.  Posted by derekmcd</DIV>  If we cannot “view” the “edge of the observable universe” then we can’t really say that the light has not reached us yet, we just cannot observe it. Replying to: <DIV CLASS='Discussion_PostQuote'> Spinning relative to what?  A spinning universe implies there is an axis about which it rotates.  This has not been observed and may never be even if it is. Posted by derekmcd</DIV>Spinning period.  Everything visible from moons, to galaxies spin, why can’t the universe?  Yes as time goes by we will be further away from another galaxy (as the moon gets further away from Earth) but we are all being kept together due to my opinion “gravity” not dark matter.   I don’t want to sound completely ******** but I think anything with mass and spins has some form of gravity and that’s why I can imagine the universe spins.  Could it be that ,Dark Matter = Gravity?  Can’t see either one of them.  It’s everywhere and nowhere all at once. Replying to: <DIV CLASS='Discussion_PostQuote'>  So far... yes (at least enough to keep Hubble's law as a reasonable explanation).  Every galaxy cluster has been observed to be receding via the metric expansion of space.  Galaxies do collide and will continue to do so due to local gravity overcoming this metric expansion.  Andromeda is within the local gravity of the Milky Way (as are others) and is recognized to be blue shifted (getting closer).  Best guesses say the Andromeda galaxy may collide with us in about 3 billion years.  Posted by derekmcd</DIV> So we shouldn’t be so jumpy to say that alls receding away from us.  My opinion, I would say we are pulling away from a point of least resistance from the observers (next galaxies) point of reference due to the lack of 2 central gravity fields pull on each other. Replying to: <DIV CLASS='Discussion_PostQuote'> There is a limit to what we can see when referring to the age of the Universe.  The Universe didn't become visible until about 380,000 years after the big bang when it expanded and cooled down enough for photons to scatter and begin their travels. Posted by derekmcd</DIV> So basically if we go back far enough then all we would see is extreme white or extreme dark?  Couldn’t that suggest we started out as a “quasar” or a “black hole.”   When the black hole was finished it “exploded.”  Here is another one of my ******** “theories.”  I have to start out with, “It is my opinion that, a black hole doesn’t hold anything in its core but breaks down everything sucked in, to its basic elementary particles due to the extreme gravitational pull and shoots them out of the “jets.”  The jets area is either directly at the north or south pole due to lesser gravity at these points.  I actually thought about that before the “jets” we seen.  Those basic particles are the building blocks to creating new universes.Have any tests been run to see if there is less gravity at the poles of Earth?Sorry I am everywhere with my thoughts today.  I cant stop thinking about everything. Replying to: <DIV CLASS='Discussion_PostQuote'> Welcome to SDC and don't ever stop asking questions.  You can never ask too many.    Posted by derekmcd</DIV> Thanks for the welcome.  And thank you for taking the time to reply. I’m trying to sound very educated and I apologize if people are confused with how I put things using uneducated terms.    <div class="Discussion_UserSignature"> "But you cant stop nothing, if you got no control, of the thoughts in your mind, that you kept and you know. You dont know nothing, that you didnt need to know, the wisdom's in the trees, not the glass window." "Breakdown" by Jack Johnson </div>

SpeedFreek · Mar 19, 2008

"What if the universe was just spinning and not expanding like galaxies spin?"What if it is? We have no way of knowing, having nothing to compare any universal motion against. Spin and gravity aren't connected in the way you seem to think. If the Earth were to stop revolving, we would not all fall off! We would still feel the same gravity - gravity is a function of mass.

"Has every object been verified to be receding away from us?  How can this be true if we have galaxies out there now colliding into each other?  And we are supposed to be colliding into another galaxy in umpteen million years.  Wouldn’t that disprove the logic that all objects are receding  away from each other?"No, only galaxies outside of the supercluster of galaxies of which the milky way is a member recede from us. Galaxies tend to clump together into clusters due to gravity and it is the distance in between clusters that increases over time, not distances between galaxies within clusters. "So we can look back in time to the early universe, if we get back to the starting point do you think that we will be able to see the “big bang” theory?"We can only see back as far as the "surface of last scattering" where the CMBR was emitted when the universe was only around 380,000 years old. This is a "wall of light" but that light has been stretched due to the expansion of the universe, stretched so much that it has been shifted into microwaves. It is estimated that light from the CMBR has  been stretched to around 1100 times its original wavelength, and so we think the observable universe was around 1100 times smaller when the CMBR was emitted, compared to the size of the observable universe today. <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

derekmcd · Mar 19, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Not to be a stickler but .... If we cannot “view” the “edge of the observable universe” then we can’t really say that the light has not reached us yet, we just cannot observe it. Posted by tdmikey</DIV> First, keep in mind that everything in the observable universe is not visible in the 'now' time.  It simply means that radiation from sources can still reach us as they have not gone beyond our visible event horizon via metric expansion overcoming the speed of light.Second, I think the case can be made for both light having not reached us yet AND not having the technology to observe it.  Replying to: <DIV CLASS='Discussion_PostQuote'> Spinning period.  Everything visible from moons, to galaxies spin, why can’t the universe?Posted by tdmikey</DIV> Again... Spinning relative to what?  This implies there is something outside the universe in order to be able to observe it spinning.  It also implies there is an axis about which the universe rotates, further implying there is a geographical center to the universe.  A rotating universe just doesn't fit with what we currently observe. Replying to: <DIV CLASS='Discussion_PostQuote'>Yes as time goes by we will be further away from another galaxy (as the moon gets further away from Earth) but we are all being kept together due to my opinion “gravity” not dark matter.   I don’t want to sound completely ******** but I think anything with mass and spins has some form of gravity and that’s why I can imagine the universe spins.  Could it be that ,Dark Matter = Gravity?  Can’t see either one of them.  It’s everywhere and nowhere all at once.  So we shouldn’t be so jumpy to say that alls receding away from us.  My opinion, I would say we are pulling away from a point of least resistance from the observers (next galaxies) point of reference due to the lack of 2 central gravity fields pull on each other.  Posted by tdmikey</DIV> The moon's orbit is receding from the Earth due tidal forces and the conservation of angular momentum between the two bodies.  This has nothing to do with galaxies receding from each other due to the expansion of the universe.Dark matter is simply a term used to describe the forces seen within a galaxy.  Galaxies require more mass than what is observed.  Without this extra matter, the observed rotational velocities would overcome gravity and start flying apart.  Dark matter keeps the galaxy together. Replying to: <DIV CLASS='Discussion_PostQuote'> So we shouldn’t be so jumpy to say that alls receding away from us.  My opinion, I would say we are pulling away from a point of least resistance from the observers (next galaxies) point of reference due to the lack of 2 central gravity fields pull on each other.  Posted by tdmikey</DIV> Not sure what you mean with this... Replying to: <DIV CLASS='Discussion_PostQuote'>So basically if we go back far enough then all we would see is extreme white or extreme dark?  Couldn’t that suggest we started out as a “quasar” or a “black hole.”   When the black hole was finished it “exploded.”  Posted by tdmikey</DIV> The farthest 'back' that we can see is the Cosmic Microwave Background Radiation (CMB) and we can't see it in a 'visible' sense as it is redshifted into the microwave part of the spectrum.  This CMB and the cosmological constant are what suggest the big bang model currently fits best with what is observed.  The big bang doesn't suggest we started as a black hole, but rather a singularity that expanded and not exploded.  An explosion suggests a center. Replying to: <DIV CLASS='Discussion_PostQuote'>Here is another one of my ******** “theories.”  I have to start out with, “It is my opinion that, a black hole doesn’t hold anything in its core but breaks down everything sucked in, to its basic elementary particles due to the extreme gravitational pull and shoots them out of the “jets.”  The jets area is either directly at the north or south pole due to lesser gravity at these points.  I actually thought about that before the “jets” we seen.  Those basic particles are the building blocks to creating new universes. Posted by tdmikey</DIV> The "jets" we observe are not from within the black hole.  The are a consequence of the accretion disks surrounding black holes.  This matter in the accretion disk is superheated and accelerated to such a state they are ejected via x-ray jets and near the speed of light via the poles of the black hole (this is likely due to the magnetic field of a rotating black hole). Replying to: <DIV CLASS='Discussion_PostQuote'>Have any tests been run to see if there is less gravity at the poles of Earth? Posted by tdmikey</DIV> The earth is an oblate spheroid, so you are actually closer to the center of mass at the poles and thus the gravity is a bit stronger.  <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

lukman · Mar 21, 2008

NASA has detected the brightest cosmic explosion ever recorded -- a massive burst of energy 7.5 billion light years away that could be seen with the naked eye from Earth, the US space agency said Thursday. The burst, named GRB 080319B, was among a record four bursts detected by Swift on Wednesday, the same day of the death of prolific science fiction writer Arthur C. Clarke who wrote "2001: A Space Odyssey." http://news.yahoo.com/s/afp/20080321/sc_afp/usspace;_ylt=Any8gudVtCaW6egNEgPAeB4PLBIF <div class="Discussion_UserSignature"> </div>

derekmcd · Mar 21, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>NASA has detected the brightest cosmic explosion ever recordedPosted by lukman</DIV> We've got a thread on GRB here at This Link  <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

neilsox · Mar 31, 2008

The earth is an oblate spheroid, so you are actually closer to the center of mass at the poles and thus the gravity is a bit stronger.  Posted by derekmcd[/QUOTE]Maybe not, as centripical force subtracts from the gravity near the Equator, but not at the poles. You weigh less at the Equator than at the poles.  Neil

derekmcd · Apr 1, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Maybe not, as centripical force subtracts from the gravity near the Equator, but not at the poles. You weigh less at the Equator than at the poles.  Neil Posted by neilsox</DIV> It's really a combination of both, but if I had to guess (and I really am only guessing), I would say the oblateness of the earth has more of an effect than centripetal acceleration.  I could very well be wrong, though.  <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

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How can we see light from very early stars? Shouldn't it have passed us already?

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