Infinite Space

spacekud · May 8, 2007

NO! not really lol. But I guess I have to accept this little fact, I do understand what your saying now. We need to see more to learn more. Our technology only goes so far, but our minds are boundless.

SpeedFreek · May 8, 2007

Heheh, yes I know how you feel! <img src="/images/icons/smile.gif" /> But remember, we would never be able to say for sure that the universe was infinite or that there were an infinite number of galaxies or that space stretches out to infinity. Why? Well, how can you say something is infinite? Just because you never find the end of something, it doesn't mean it doesn't end. It only means you haven't found the end yet! How could you say for sure? <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

spacekud · May 9, 2007

But if you say it that way and we do find the end some way or another hypothetically speaking, it does end... so what would be the stopping point? Heh sorry I'm making things very difficult I just wonder a lot my apologies.

derekmcd · May 9, 2007

Don't ever be afraid to ask the 'difficult' question. Just be prepared for unsatisfying answers. The question you are asking is such a question that we are still trying to find out if it is even knowable. Similar to asking what came before the Universe. Even asking the question 'Is there a God' is knowable; He just needs to present himself. The other two questions can't just present themselves... we have to physically search for them. With that said, scientists can indeed make very educated guesses about our observable universe and apply averages to it. They can even know things with near absolute certaintly about the observable universe, but realize it is such a potentially small sample that averages are quite likely not applicable. As with many profound questions such as these, it is the pursuit of the answer that educates us. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

spacekud · May 9, 2007

How far out, with our current technology is the furthest we can see???

SpeedFreek · May 9, 2007

Simple answer - we have seen galaxies that are around, or a little over 13 billion years old. These were galaxies thought to have formed around 750 million years after the beginning of the universe. More complicated answer - the light from the most distant galaxy observed has taken around 13 billion years to reach us. But this doesn't mean that this object is now 13 billion light years away, as the expansion of space since the light left that object 13 billion years ago means that object would be much further away than that by now. It is estimated that the most distant objects we see as around 13 billion light years away, would now be something like 45 billion light years away! Over the largest distances space-time looks very curved due to the very fast rate of expansion early in the universe, the further you look the harder it is to estimate distance. <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

spacekud · May 10, 2007

Ok when you say beginning of the Universe are you refering to the beginning of time, space and everything between? Or are you saying when everything was created would it not be the Universe still even before our solar system and others were created because its infinite correct, no beginning and no end. beginning it was space and in the end it will still be space, thats another question on my mind I know that these could not be answered but I just wanted to see everyones thoughts about them.

rfoshaug · May 10, 2007

<blockquote>In reply to:<hr />Simple answer - we have seen galaxies that are around, or a little over 13 billion years old. These were galaxies thought to have formed around 750 million years after the beginning of the universe. <hr /></blockquote> Here's a thing I've never been able to understand. How is it possible that those galaxies were so far away already 13 billion years ago, when in fact the universe wasn't that big back then? And if the galaxies are now 45 billion light years away, this must mean that the universe is 45 billion years old, as no galaxies can move away from us faster than light? <div class="Discussion_UserSignature"> ----------------------------------My minds have many opinions </div>

robnissen · May 10, 2007

Fair question. The reason why galaxies were 13 billion ly away, shortly after the BB is due to inflation. Inflation means creating space between galaxies, the galaxies don't move faster than light, but space is created between the galaxies that forces them apart. Inflation is still continuing, which is why galaxies that were 13 B LY away are now 45 B LY away. Now having said all that, I have no idea how "space" gets created to push galaxies apart. I have asked that question several times here, and have not gotten a satisfactory response. Of course many questions don't have a satisfactory response (Where did the singularity of the BB come from?), maybe this is just one of them.

derekmcd · May 10, 2007

During the inflationary epoch of the big bang, the Universe grew to nearly the size of what we can currently observe in a very short period of time. Given the fact that the Universe is accelerating, these objects we observe are more than double the distance now. It's not that the galaxies are physically speeding away from us at speeds greater than light, it's the 'fabric of the universe' that is expanding and the greater the distances mean the faster the expansion eventually putting them out of the reach of our light cone. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

spacekud · May 10, 2007

Objects take time to develop in the brain correct how long does the furthest object take to develop if we were looking at it through the telescope with our own eyes? If anyone gets the question...

MeteorWayne · May 10, 2007

I must admit I don't get the question. The eye-brain connection is pretty quick (a few hundred milliseconds), while the light we see through a telescope takes however long it takes. 1.3 seconds for the moon, a few hours for the outer solar system, 4.3 years to the nearest star, 13 billion years for the farthest things we can see in a telescope. So, I don't understand <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

spacekud · May 10, 2007

nevermind you answered it lol sorry I did not get my own question either after I read it again.

weeman · May 10, 2007

Now having said all that, I have no idea how "space" gets created to push galaxies apart. I have asked that question several times here, and have not gotten a satisfactory response. Perhaps this question may never be answered. I however think that there could be some scientific evidence that we might come across one day. Might we have to look for the answer to this question on a quantum level? I can come up with suggestions as to why it is expanding, but none of them should be taken as good answers. Perhaps the fabric of space is expanding because space is all there is. Astronomers say that space has nothing to expand into other than itself. Our universe expands into itself because our universe is all that there is. Space might expand just because it can. If a seed has plenty of water and sunlight why does it grow into a flower? Because it can <img src="/images/icons/smile.gif" /> <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 · May 10, 2007

Just to clarify a point and to make sure we know the terminology: The inflationary epoch happened within a fraction of a second and only took the universe from the size of a proton to around ten centimeters across. This still meant the universe inflated faster than light at this stage as we are talking about something less than a thousandth of a second. Inflation didn't take the universe up to anything close to the size we see today. After the inflation, the universe was filled with a quark-gluon plasma which was now expanding extremely fast, and this is still less than a second after the big bang... ... 300,000 years later we come to the point of recombination, when hydrogen and helium atoms begin to form. This is also the point where photons decoupled and the Cosmic Microwave Background radiation was emitted. There are two important points to note here. Firstly, the metric expansion had been decelerating since soon after inflation. Secondly, the area of space where our most distant galaxies would eventually form was at that time only something like 40 million light years from the point in space where our galaxy eventually formed. So it is theorised that what would become our observable universe had a radius of around 40 million light years when the CMB was emitted, 300,000 years after the big bang. Metric expansion took the universe from the size of a grapefruit to what it is today! <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

derekmcd · May 11, 2007

Good explanation, Speedfreak... thanks. I kinda fumbled the ball on that one <img src="/images/icons/smile.gif" />. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

Kalstang · May 11, 2007

This still meant the universe inflated faster than light at this stage as we are talking about something less than a thousandth of a second. Ok here is something that is interesting too. One i've always questioned. The law says that nothing can go faster then light. How is it that the universe expanded faster then light then? If it did then that would have to mean that things can go faster then light. After all laws of physics just dont up and change themselves. They have to be constant from beginning to end. <div class="Discussion_UserSignature"> I have an answer for everything...you may not like the answer or it may not satisfy your curiosity..but it will still be an answer. "Imagination is more important then Knowledge" ~Albert Einstien~ Guns dont kill people. People kill people.Solar System </div>

derekmcd · May 11, 2007

The galaxies are not moving 'through' space faster than light. It's the expansion of space that is increasing the 'distance' between the two galaxies. Raisins in a rising loaf of bread are not actually moving through the bread. The rising bread is an analogy for spacetime. Difference being is that space and time are not physical, tangible objects you can touch. Spacetime is not 'fabric' that stretches. There is no physical medium, but it is still expanding <img src="/images/icons/smile.gif" />. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

robnissen · May 11, 2007

The inflationary epoch happened within a fraction of a second and only took the universe from the size of a proton to around ten centimeters across. That statement is not accurate, to be accurate you must state "took the VISIBLE universe . . . to around 10 centimeters. We have no idea, and currently no way of knowing how big the original singularity was. As I stated in a previous post, it could have been the size of the Milky Way or larger. It is true that our visible universe was 10 cm., but whether that was and is the entire universe is unknown.

SpeedFreek · May 11, 2007

Excellent catch there Rob! You are indeed correct. Inflation took our observable universe from the size of a proton to the size of a grapefruit. <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

SpeedFreek · May 11, 2007

The law says that nothing can go faster then light. How is it that the universe expanded faster then light then? If it did then that would have to mean that things can go faster then light. After all laws of physics just dont up and change themselves. They have to be constant from beginning to end. The "law" says that mass cannot be accelerated to the speed of light. It is actually quite specific. It doesn't say that "nothing can go faster than light". Theoretically it is consistent with relativity if an object were to be created already moving faster than light. It just cannot accelerate there. But back to the superluminal inflation. One scenario suggests that prior to cosmic inflation, the universe was cold and empty, and the immense heat and energy associated with the early stages of the big bang was created through the phase change associated with the end of inflation. During this phase change, known as "reheating", the exponential expansion that occurred during inflation ceases and the potential energy of the inflation field decays into a hot, relativistic plasma of particles. The speed of inflation does not violate relativity, as the space expanded superluminally and was only filled with particles afterwards. But even if the above scenario is incorrect, space could still inflate faster than light with matter in it and not violate relativity as the particles would not be moving themselves - space would just be growing between them. This is the mechanism that allows the superluminal recession speeds of galaxies due to the metric expansion of space. <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

SpeedFreek · May 11, 2007

To clarify another earlier post, regarding the most distant objects and their original distance to us when they emitted the light we see. In an earlier post I talked about the Cosmic Microwave Background radiation. It was emitted around 300,000 years after the big bang, and at that time our observable universe would have been around 40 million light years in radius. But I didn't go any futher than that, so here goes! The most distant galaxies we observe, the ones that are around 13 billion years old, were a lot closer than 13 billion light years away when they emitted the light we see today. At around 500-750 million years after the big bang, our observable universe had expanded a lot since the CMB event. Those early galaxies that formed were only around 2 billion light years away from us then. During the 13 billion years that light was travelling, the space between us expanded from 2 billion light years to something around 40 billion light years. So as you can see, the often given figure of 13 billion light years for the most distant objects is misleading, as it doesn't actually relate to any relevant values. They are 13 billion years old, were around 2 billion light years away when the light left them, and are now around 40 billion light years away. <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

robnissen · May 11, 2007

That is very interesting, I never thought about that, but that makes sense. Speedfreak, one of your earlier posts has raised a question for me. I thought inflation was just a special case of the expansion of space that is continuing. From your earlier post, it looks to me like you believe they are different. Could you please explain? (Or anyone else that would like to chime in.)

SpeedFreek · May 11, 2007

Well, if I explain it in that way it is only because the physics gets more speculative the closer you get to inflation - i.e. we understand the physics of the universe better after the inflation, when it was an expanding but decelerating quark-gluon plasma. The expansion is thought to have began at the planck epoch, and continued during the grand unification epoch, where the expanding universe cools and gravity separates from the electromagnetism and the strong and weak nuclear forces. At a certain temperature threshold between 10^-35 seconds and 10^-32 seconds after the Big Bang the inflation of the already expanding universe occurred. The universe flattened and went through a period of rapid exponential expansion, which was both homogeneous and isotropic. During this time the quantum fluctuations occurred that lead to the formation of structure in the universe. Then reheating occurred and the expansion continued and this is all happened in a lot less than a second after the big bang. But all the above is speculative. I'm not sure how the expansion before inflation relates to expansion after. <img src="/images/icons/smile.gif" /> It was 300,000 years until the observable universe was around 40 million light years in radius. This is somewhat less speculative! <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

kyle_baron · May 11, 2007

But back to the superluminal inflation. One scenario suggests that prior to cosmic inflation, the universe was cold and empty, and the immense heat and energy associated with the early stages of the big bang was created through the phase change associated with the end of inflation. During this phase change, known as "reheating", the exponential expansion that occurred during inflation ceases and the potential energy of the inflation field decays into a hot, relativistic plasma of particles. I have a question. Is this "reheating" period the trigger that caused the inflation phase to slow down to the speed of light? Seems to me, that this would violate Newton's 1st Law: "An object in motion will remain in motion (FTL) unless acted upon by a force." Do plasma particles count as a force? Just looking for opinions. <div class="Discussion_UserSignature"> </div>

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