which way to the big bang

[xxMIKExx]

Hi everyone. I was reading the other day about the oldest GRB found to date. I can't find the article anymore but it was on here (space.com). I've since been wondering how they manage to find these blasts from the past. Can they just point a telescope in any direction and stare as deep into the abyss as they can? or do they have to point them in a certain direction to look back at the past? If so, is this the way to the BB. If it is, can they look the other way towards the big crunch and see into the future...so to speak?

 

[ZenGalacticore]

Yes. They point there telescopes in any direction and peer as deep as they can. But we can't look all the way back to the big bang because the light from the bang hasn't had, and will never have, time to get to our eyes, because of the constant expansion. At least, that's my understanding of it.

MeteorWayne can probably answer your questions better than I.

But as far as seeing into the future to witness the Big Crunch, that makes no sense to me. We can see only the past when we look out to space, not the future.

 

[origin]

Yes. They point there telescopes in any direction and peer as deep as they can. But we can't look all the way back to the big bang because the light from the bang hasn't had, and will never have, time to get to our eyes, because of the constant expansion. At least, that's my understanding of it.

It is not so much that we have to look far into space, it is just that we can look in any direction and detect microwave radiation that originated when the universe first became transparent (the density dropped to that point). The expansion of the unverse has 'stretched' the original radiation decreasing it to the frequency of microwave.

 

[Eman_3]

Gaze up towards the Sun, and you are looking back in time. That is because light from the Sun takes eight and a half minutes to travel the distance. You are seeing what the Sun looked like eight and a half minutes ago.
If you look at a stellar object one light year away, you are looking at an image from a year ago, which took that long to travel to earth. That is what is referred to when astronomers talk about looking back in time.

The universe is estimated to be 13.7 billion years old, and it's radius is 78 billion light years.

 

[xxMIKExx]

So how is it then, that we find these objects from so far way, towards the creation of the universe, without actually needing to look towards the creation of the universe?

Sorry if that doesn't make sense (I was having trouble putting it into words )

 

[CommonMan]

So how is it then, that we find these objects from so far way, towards the creation of the universe, without actually needing to look towards the creation of the universe?

Sorry if that doesn't make sense (I was having trouble putting it into words )

I have the same problem as you about putting what I want to say in words. As for your question, I understand what you are saying, to the common man we would think that we have to look toward where it all begun, but there will be some smarter people than us that will post shortly to explain. or try to, that there is no one spot for the begining of the universe, that where ever you look is the begining. Maybe we both will understand. :?

 

[SpeedFreek]

The universe is estimated to be 13.7 billion years old, and it's radius is 78 billion light years.

Just a small correction, but the radius of the observable universe is theoretically 46 billion light-years, giving a theoretical diameter of 92 billion light-years. That figure of 78 billion light-years is a minimum diameter for the whole universe derived using the data from WMAP. The team working with the WMAP data hope to be able to extend that minimum diameter out to 92 billion light-years using more advanced techniques.

http://en.wikipedia.org/wiki/Observable ... onceptions

 

[FlatEarth]

So how is it then, that we find these objects from so far way, towards the creation of the universe, without actually needing to look towards the creation of the universe?

Sorry if that doesn't make sense (I was having trouble putting it into words )

I have the same problem as you about putting what I want to say in words. As for your question, I understand what you are saying, to the common man we would think that we have to look toward where it all begun, but there will be some smarter people than us that will post shortly to explain. or try to, that there is no one spot for the begining of the universe, that where ever you look is the begining. Maybe we both will understand. :?

Well, if you're looking for someone who is smarter to answer the question, then I'm not it, but I do have an answer.

Because the Big Bang wasn't an explosion, but rather an expansion, everywhere is considered to be the origin of the Big Bang. You cannot look at another part of the universe and say "That's where the BB occurred." It happened all around us. That's why it doesn't matter where you look, you will always look back in time. No matter how advanced the technology, we will never actually see the BB because the universe didn't emit light until around 13.1 billion years ago (not exactly right, but close).

 

[SpeedFreek]

So how is it then, that we find these objects from so far way, towards the creation of the universe, without actually needing to look towards the creation of the universe?

But we are looking towards the creation of the universe, whichever direction we look in space. The further we look, the more out of date our information is, as we are seeing the universe as it was in the past. We can see what is theoretically the first freely moving light in the universe - the Cosmic Microwave Background Radiation (CMBR), coming in from all directions.

Theory has it that every point in the observable universe was very close together to begin with. Everything was very hot and the universe would have been opaque to light as photons of light would keep hitting other particles. But after a while the universe had cooled enough for atoms to form and photons were released throughout the universe as the CMBR.

We detect that CMBR today coming in from all directions, and our theory tells us that the CMBR photons were emitted when the universe was only 380,000 years old. We theorise, due to the CMBR being released throughout the universe, that CMBR photons have been hitting this place from all directions all the time since they were released nearly 13.7 billion years ago. For all that time, CMBR photons have been hitting "us" from all directions, and as time went on we would be detecting photons emitted at an ever increasing original distance.

The CMBR that are hitting us today from all directions were originally emitted only 42 million light years away. Earlier in history we would have been hit by CMBR originally emitted at distances closer than 42 million light years, and in the future we expect to continue to be hit by CMBR originally emitted at distances larger than 42 million years.

But if the CMBR we currently detect was emitted only 42 million light-years away, how come it took nearly 13.7 billion years to reach us, if it moves at the speed of light?

Well, the universe is expanding. More than that, the universe was expanding incredibly fast early on in its history and the rate of expansion was decelerating for a very long time, for around 9 billion years. But back when the CMBR was released, the universe was expanding so fast that things only 1 million light-years away from each other would have been separating faster than light. If you and I were floating in space only 1 million light-tears apart at that time, then from my point of view you would be receding from me faster than light, and from your point of view I would have been receding from you faster than light! That's the thing about the expansion of the universe, everywhere can consider that they are not moving and that everything else is moving away from them!

There is no origin, or centre of the expansion. Everywhere is moving away from everywhere else. You can think of it as if it is the space between things that expands, putting more distance between those things.

So as those CMBR photons emitted 42 million light-years away were moving towards this place, the distance in between here and those photons was growing. Early on it was growing faster than they could progress, but as time went on and the rate of expansion slowed, those photons eventually found themselves in regions of space that were receding from us at less than the speed of light and they could finally make progress towards us! Their journey took nearly 13.7 billion years and during that journey the universe expanded to around 1100 times the size it was when they were released.

So, when we look out in all directions we see CMBR that is the oldest possible light we can see. We currently see CMBR originally emitted 42 million light-years away, and we think the region of space that CMBR was emitted from would now be something around 46 billion light-years away. This is the edge of our observable universe - the concept of where we think the origin of the oldest light we see is, today. We think that there would be galaxies 46 billion light-years away right how, just like there are galaxies around here. But what we see from that region of the universe, all around us, is the radiation released there long ago, when that place was a lot closer to us.

Now then, if there were some sort of radiation emitted at the Big-Bang itself that we could detect (simply for arguments sake), where does the theory say it would look it came from?

Theory says it would have come from.... right here!

 

[robnissen]

The universe is estimated to be 13.7 billion years old, and it's radius is 78 billion light years.

Just a small correction, but the radius of the observable universe is theoretically 46 billion light-years, giving a theoretical diameter of 92 billion light-years. That figure of 78 billion light-years is a minimum diameter for the whole universe derived using the data from WMAP. The team working with the WMAP data hope to be able to extend that minimum diameter out to 92 billion light-years using more advanced techniques.

http://en.wikipedia.org/wiki/Observable ... onceptions

Another small correction, the MINIMUM size of the universe is 92 billion light years, but that is based on the original singularity being as small as we can imagine, on the order of the planc (sp?) constant or smaller. But there is no law of physics (because the laws of physics do not apply to the singularity) that limits the size, all we have is the lower bound. Thus, we have absolutely no way of knowing the size of the original singularity, the original singularity could have been smaller than a quark, a meter, a mile, a light year, a trillion light years. Obviously, if it was a trillion light years, the universes would be unbelievably immenses. Unfortuneatly, it does not appear we will ever have anyway of knowing the size of the original singularity, so we will never know the actual size of the universe, we can only know the minimum size.

 

[SpeedFreek]

Sorry Rob, but I was talking about the theoretical size of the observable universe, which has a current diameter of 92 billion light-years. If the whole universe is larger than our observable part of it, then 92 billion light-years would indeed be the minimum diameter for the whole universe, as I said.

 

[makuabob]

Hi everyone. I was reading the other day about the oldest GRB found to date. I can't find the article anymore but it was on here (space.com). I've since been wondering how they manage to find these blasts from the past. Can they just point a telescope in any direction and stare as deep into the abyss as they can?...

Hi, xxMIKExx.

There are several orbiting observatories specially designed to detect gamma ray bursts. It has taken many years to get these things put together and up into orbit. The latest is the FERMI telescope: it has two sections—one section can sense a burst from anywhere (even earth), then create an approximate direction (away from the earth) which is down-linked to observers on the ground AND used on-board to quickly slew its Large Area Telescope (LAT) to point at the those coordinates for continued, detailed data taking.

The burst you are talking about was back in April of this year (GRB 090423). With a redshift (z) of 8.2, it calculates out to be more than 13 billion L-Y away. (When z=0, there is no redshift; when z=1, wavelength (λ) is twice as long—musically equal to an octave lower; when z=3, λ=1/4; and when z=7, λ=1/8. So the energy that arrived was shifted to nearly 1/10 its starting energy by the expansion of the universe. Awesome!)

Yes, they can 'stare' in any direction but there are limits to what can be 'seen,' depending on the wavelength at which they are looking. In the case above, visible light would be redshifted way down into the infrared, so they have to use thermally sensitive detectors and be high enough in the atmosphere for the infrared to get to the sensors.. or have a telescope in orbit! Did I mention that a really large reflector counts, too?!

 

[xxMIKExx]

Thanks for the replies but I still can't get my head round the fact that creation happened everywhere as opposed to a specific point. How is that even possible? Unless the BB wasn't a "one off" event, but we are surrounded by many BBs.

Also, is the CMBR a direct remnant of the BB and nothing else, or is it emmited from every object in the Universe at too great a distance to be seen in visible light?

Sorry if these are "idiot" questions but I've been looking at all sorts on the net which just leeds to confusion. everything on the net contradicts the last thing I read.
Thanks again

 

[makuabob]

Thanks for the replies but I still can't get my head round the fact that creation happened everywhere as opposed to a specific point. How is that even possible? Unless the BB wasn't a "one off" event, but we are surrounded by many BBs.

Also, is the CMBR a direct remnant of the BB and nothing else, or is it emitted from every object in the Universe at too great a distance to be seen in visible light?

Sorry if these are "idiot" questions but I've been looking at all sorts on the net which just leeds to confusion. everything on the net contradicts the last thing I read.
Thanks again

The Hot Big Bang (HBB) Theory is not, yet, conclusively proven but it is the leading (which, in science circles, can mean 'best funded') explanation. It has some quirks which have caused what can appear as ad hoc "fields" to be proposed. To explain the extremely rapid inflation phase, the inflaton field has been proposed and to explain the dipole effect (radiation from one side of the universe seems slightly cooler than the opposite), a curvaton field has been suggested. These names can be searched out on-line for more info.

There are many other theories for the origin of the universe. One (not the one involving the lonely turtle) was proposed by a now-deceased german theoretical physicist which had the universe expanding without matter for nearly a google of years (remember, a 'google' was 10^100 before a company hi-jacked it). Then, in a chaotic, firework-like event, matter formed throughout. Since 'established' theories are like those "jealous lovers" described in Plato's writings, I will not mention a name or describe it further.

The CMBR is invoked as support for the HBB. There may be other explanations for it.

Just as a classical music host says, "Remember, all music was once new," all knowledgeable people were once idiots. All of us start out that way, it's the desire to learn that makes the difference. (A humorous dictionary I have defines "idiot" as someone who doesn't know something you learned yesterday.)

Happy hunting!

 

[Saiph]

Thanks for the replies but I still can't get my head round the fact that creation happened everywhere as opposed to a specific point. How is that even possible? Unless the BB wasn't a "one off" event, but we are surrounded by many BBs.

The key here is to understand a few underlying tenets of BB. First, that we are PART OF the resulting 'explosion'. And that before the BB, there was no space, there was no time. There was no other place from which to observe it on the outside.

It is an expansion of space, and time, itself. It is not like the everyday concept of an explosion, like a firework, that happens somewhere we can see it.

And since it is the creation and expansion of space itself, and we reside in space, every point in space is indistinguishable from the next. Meaning there is no specific center. Each point can legitimately call itself the center.

Also, is the CMBR a direct remnant of the BB and nothing else, or is it emmited from every object in the Universe at too great a distance to be seen in visible light?

Just from the BB. We'd see a very different pattern if it was emitted by a wide range of individual sources.

Sorry if these are "idiot" questions but I've been looking at all sorts on the net which just leeds to confusion. everything on the net contradicts the last thing I read.
Thanks again

No apologies necessary. While these are fundamental questions, they are good ones! They show that you're actually thinking about the material, and not just regurgitating it.

 

[junkheap]

Could someone explain to me in layman's terms about how the radius of the observable Universe is 46.5 billion light-years and the Universe is 13.7 billion years old?

Also, how was was the light ever able to reach us from 46.5 billion light years away if the Universe is 13.7 billion years old?

It makes my head hurt. :?

Thanks.

 

[Imtiazk]

The universe is estimated to be 13.7 billion years old, and it's radius is 78 billion light years.

Just a small correction, but the radius of the observable universe is theoretically 46 billion light-years, giving a theoretical diameter of 92 billion light-years. That figure of 78 billion light-years is a minimum diameter for the whole universe derived using the data from WMAP. The team working with the WMAP data hope to be able to extend that minimum diameter out to 92 billion light-years using more advanced techniques.

http://en.wikipedia.org/wiki/Observable ... onceptions

This always gets me. If the universe is 13.7 billion years old, the maximum distance should be 13.7 billion light-years or is it that the universe in the mean time has "expanded" by another 33 billion light-years.

 

[SpeedFreek]

Could someone explain to me in layman's terms about how the radius of the observable Universe is 46.5 billion light-years and the Universe is 13.7 billion years old?

Also, how was was the light ever able to reach us from 46.5 billion light years away if the Universe is 13.7 billion years old?

This always gets me. If the universe is 13.7 billion years old, the maximum distance should be 13.7 billion light-years or is it that the universe in the mean time has "expanded" by another 33 billion light-years.

It is difficult to get your head around, for sure!

It is that the observable universe started off very small and in the meantime has expanded by another ~46.5 billion light-years, in radius.

When we see light that is 13.7 billion years old (the cosmic microwave background radiation or CMBR), it was not emitted 13.7 billion light-years away, it was actually emitted (or more accurately, released) a mere 42 million light-years away.

Imagine our observable universe getting smaller, backwards in time. Everything gets closer and closer to our viewpoint until all the galaxies currently within a 46.5 billion light-year radius are one big mass (it's getting warm!), with our viewpoint at the centre. Then, as everything is crushed together it gets hotter and hotter until it all compacted down to the size of a grapefruit, with our viewpoint still in the centre!

Run the film forwards, in real time. Within a second it has expanded to a radius of thousands of light-years, it is expanding so fast that the "edge" of all that stuff (remember, this is only the stuff we have observed, there might be more!*) is receding from us many magnitudes faster than the speed of light.

The stuff of the universe includes the space, and it is as if space itself is expanding, pushing everything apart from everything else!

The rate of expansion quickly decelerated as the universe cooled and 380,000 years later, that "edge" was 42 million light-years away when the CMBR was released throughout the universe. Those CMBR photons headed in all directions and this place has been hit by CMBR photons since they were released, but now, 13.7 billion years later, we detect CMBR photons originally released only 42 million light-years away.

Those are the photons we detect that have travelled the longest time to reach us, so they mark the edge of what we call the observable universe. This edge is conceptual, there is nothing special about it except that it is the distance from us, in all directions, from which the CMBR we currently detect was originally released from. In the future, we expect to detect CMBR originally emitted further away than that, as time goes on.

In physical cosmology, the cosmological event horizon (also known as a particle horizon) is the maximum distance from which particles could have travelled to the observer in the age of the universe. It represents the boundary between the portion of the universe which could have conceivably been observed at a given time (the observable universe) and the unobservable regions of the universe.

As those CMBR photons reach us, we estimate that the place they were emitted from will have receded to 46.5 billion light-years away, due to the amount that the universe has expanded in the 13.7 billion years since they were emitted. In the time since they emitted, galaxies have formed throughout the universe.

But consider this - those CMBR photons we detect today actually did travel 13.7 billion light-years to reach us, even though they were only released 42 million light-years away! It is as if they were swimming upstream against the current of the cosmic flow. They were dropped into the cosmic flow when it was really fast, 13.7 billion years ago, and initially they were swept downstream by the fast current. But as the current slowed they started making headway towards us and eventually reached us 13.7 billion years after they were dropped. They swam 13.7 billion light-years to reach us and the actual place they were dropped in is now 46.5 billion light-years away, way downstream!

The cosmic flow is not really a "flow" like a river though, it is more like the size of the cosmic ocean is increasing as more ocean is being pumped in, everywhere! It is as if more space is continually being added, increasing the distance between the clusters of galaxies across the universe. Galaxies aren't moving through space faster than light, but space expands** between galaxies that are distant enough from each other not to be gravitationally bound, meaning that as you look across increasing distances there is the appearance that galaxies are receding faster and faster, even though none of them are actually moving much at all in their local area.


*when I say there might be more, that is the difference between the observable universe and the whole universe. There might always have been more than we can have possibly seen. When our observable universe was the size of a grapefruit, the whole thing could have been any*** size larger! However many times larger it was back then, it would be larger today, by the same factor.

** space "itself" may not expand, as it stands nobody knows what actually causes the expansion, but it looks like space itself is expanding.

*** perhaps the universe is infinite in extent.

 

[rfoshaug]

Excellent post, Speedfreek!

:geek:

 

[robnissen]

Excellent post, Speedfreek!

:geek:

Agreed. I especially liked the analogy to particles swimming upstream against the current. I do have one disagreement with the post, however, I believe the visible universe was actually MUCH smaller than grapefruit size at the time of the big bang, more like subatomic in size. But it doesn't really matter, because as you pointed out, we have no way of knowing how much bigger the entire universe (not just the visible universe) was at the big bang, and it could in fact be infinite.

 

[SpeedFreek]

I should have pointed out that, in order not to introduce too many concepts, I only took time back to the end of the inflationary epoch, when our observable universe was the size of a grapefruit. I purposely did not take it all the way back to the Big-Bang singularity, as the inflationary epoch requires a whole lot of explanation on its own. Well spotted, Rob!

 

[robnissen]

I believe that there is not a good theory why the whole universe did not just immediately collapse back into a black hole and disappear. Now, part of the fudge factor for why the universe didn't immediately collapse into a bh, is that during the inflationary period, the laws of physics do not apply. I will accept that, but obviously, if the entire visible universe was grapefruit size, that would be well within the Schwarzschild radius. I read once that the Schwarzschild radius for the entire visible universe is around 12 B LY. Is that correct? If so, why hasn't everything in the visible universe collapsed back into a black hole, sometime between when the visible universe was grapefruit sized and it was 12 billion light years in diameter?

 

[SpeedFreek]

Good question!

But the Schwarzschild solution is an "outside" solution, it only applies when comparing the density of mass in one place with the density in another, i.e. in a star versus the space around the star. In other words, it only applies to mass surrounded by space. This does not apply in the Big-Bang scenario, as during the Big-Bang there was no empty space - all of space was filled with matter and just as there is no centre of expansion, there was no "centre of attraction" as everywhere was the same as everywhere else. The Schwarzschild solution only describes what happens outside of the event horizon.

It is interesting to note, however, how the principle does apply at cosmological scales in a slightly different form, as the critical mass of the universe.

Before they discovered the relatively recent acceleration of the expansion, cosmologists thought the rate was still decelerating and the question was whether there was enough mass in the universe to bring the expansion to a halt and if that were the case, whether there was enough mass to cause the universe to start collapsing towards a "Big-Crunch"!

 

[xxMIKExx]

Hi all, I have enjoyed reading the replies but , again, they lead to more questions.
When we look at the image of the CMBR, what exactly is it that we are looking at? What do the different colours represent? I know they show different temperatures but what is at different temperatures?
Is it an image of solid bodies distributed at the outer reaches of space or is it the redshift of Hydrogen?
IF the CMBR image is the BB, then wouldn't it make more sense for it to be uniform in colour (and temperature) and not hold so many pockets of differing temperatures?
Again, sorry if these are daft questions but I'm just trying to understand things a little better. If you don't ask, you wont know. So, I'm pretty sure I will have more questions to ask

 

[xxMIKExx]

Sorry for any confusion but I think I worded my orriginal post wrong
I know that if we observe an object at a distance of 6billion LY, then we see it as it was 6billion years ago (that makes sense) but how can we say an object , e.g a GRB, 6billion LY away occured when the Universe was, say, 8billion years old if we are not looking towards the BB (if that makes sense?)
If we look towards the BB and see an object 6billion LY away then yes, it must've occured when the Universe was "younger" than it is at our point of view. But if we look the other way and see an object 6billion LY away, then that must've occured when the Universe is "older" than it is at our point of view.
I'm struggling to make sense with this post, I will try and add an image later to show what I mean.