Expanding Universe

[Grandpa Greenman]

Could the Universe be expanding because the so called big bang never stopped and some where in the Universe there is a point were material from "the bang" is still spewing into a hot section of the Universe?

[sumthingnice60]

The big bang was an explosion at a certain point in time and is used to describe the creation of time and space rather than to describe the expansion of space. So, I don't believe the big bang is still going on. I like to think of this like an atomic bomb. The instant the bomb hits the ground can be thought of as the big bang. The radiation that expands after the bomb hits doesn't mean that the bombing is still happening.

[Grandpa Greenman]

The big bang was an explosion at a certain point in time and is used to describe the creation of time and space rather than to describe the expansion of space. So, I don't believe the big bang is still going on. I like to think of this like an atomic bomb. The instant the bomb hits the ground can be thought of as the big bang. The radiation that expands after the bomb hits doesn't mean that the bombing is still happening.

Say it is not a Bang so much as an opening in another dimension spewing time and space in to this universe.

[sumthingnice60]

Say it is not a Bang so much as an opening in another dimension spewing time and space in to this universe.

If I'm not mistaken, then the reason the universe is expanding is because of the force of the big bang. The big bang cause space to continue outward which is why it's moving outwards today. But it is also slowing down because of gravity.

[Torgo]

Okay, there are a lot of misconceptions floating around here. They are some of the most common misconceptions people have of the big bang.

The big bang was not an explosion of a very dense kernel of matter into a bigger empty space. What it is is the idea that the universe was much denser in the past and it is expanding. When we look out across space, we see that everything is moving away from everything else on large scales. There is no "center" to this expansion - it is uniform everywhere. If there was some original object that exploded then things near the center would be moving slower in order to have been found there in the first place.

What we see is that in the past space was smaller and space is expanding. Perhaps a better way to put this is that the distance between two points always increases with time. On very small scales, up to the size of galaxy clusters, gravity overcomes this and things do not move apart. On larger scales where gravity is weaker, this forces objects apart faster than gravity can pull them together again.

For all we know the universe could be infinite, and have always been infinite from the beginning of its existence. But space may have stretched such that it is, I suppose one could say, a "much bigger infinite" than it was at its beginning. I lack the mathematical terminology to say anything clearer than that, I'm sorry.

Interestingly enough, looking at the redshifts and intensities of supernovas in distant galaxies that are known to always have the same intensity and spectrum, it has come to light that the universe's expansion is actually ACCELERATING. No one KNOWS why this is, but this is the observation that "dark energy" has been proposed to explain.

[rideron]

If all matter in existance originated with the "Big Bang" what is it that the Universe is expanding into???? What is, and from whence came, the 'space' into which the Universe is now expanding if not from the Big Bang itself? Was it already there before the Big Bang happened? ? And if you could get out to the very outer limit of the edge of the expanding Universe, and take one step beyond that, where would you be?

Edited December 12, 2007 by rideron

[sumthingnice60]

Interestingly enough, looking at the redshifts and intensities of supernovas in distant galaxies that are known to always have the same intensity and spectrum, it has come to light that the universe's expansion is actually ACCELERATING. No one KNOWS why this is, but this is the observation that "dark energy" has been proposed to explain.

Wow, it's accelerating? I totally didn't know that. I always assumed that the expansion process is slowing down.

[Torgo]

If all matter in existance originated with the "Big Bang" what is it that the Universe is expanding into???? What is, and from whence came, the 'space' into which the Universe is now expanding if not from the Big Bang itself? Was it already there before the Big Bang happened? ? And if you could get out to the very outer limit of the edge of the expanding Universe, and take one step beyond that, where would you be?

The big bang is NOT a bunch of mass originating at one point and spweing out into space. As near as we can tell matter and space originated together with matter embedded in space throughout. Since that time the space has stretched moving the matter further and further apart decreasing the overall density of the universe and stretching light out to longer and longer wavelengths - hence the Doppler shift.

The classic example to ilustrate this is a balloon. Take a sharpie and put little dots all over it. These are collections of matter, like galaxies. Blow up the balloon, or take your hands and stretch it out - the dots do not explode out from any point, they just get further and further away while the rubber they're on gets bigger.

As near as we can see the universe has no edge. We can only see a finite distance away but that is because light has had a finite time to travel since the universe became transparent to light when it cooled down enough for the initial plasma to combine into neutral gas molecules.

he instant the bomb hits the ground can be thought of as the big bang. The radiation that expands after the bomb hits doesn't mean that the bombing is still happening.

The background radiation we see is NOT the radiation from the (nonexistant) "Explosion" of the big bang. What it IS is the heat glow of the universe at the moment it became transparent to light, redshifted down into the microwaves by the expansion of space.

Edited December 13, 2007 by Torgo

[+joc]

The Big Bang is a myth. It never happened. It is an err in thought process to think that it did. The Universe is not expanding. This is also a myth. They are both theories...and not very good ones either.

Edited December 13, 2007 by joc

[magnetar]

-

Edited December 13, 2007 by magnetar

[sumthingnice60]

The Big Bang is a myth. It never happened. It is an err in thought process to think that it did. The Universe is not expanding. This is also a myth. They are both theories...and not very good ones either.

The big bang theory is the best theory we have right now. If you don't think they are good, then what is a good theory?

[The Silver Thong]

The big bang theory is the best theory we have right now. If you don't think they are good, then what is a good theory?

The big bang is a theory yes, and it does hold the scientific community together. What Joc is saying (if I may be so bold) is that God created the universe and the reason why is still unknown. Science has many answers or theories based on mathematical equations that some see as a way of dismissing god. The answer to some, is what is your faith or what can science "prove" or show as proof. Many hold onto faith and thats fine, until it contradicts what can be proven. Hence we see this.

Quote

"The Big Bang is a myth. It never happened. It is an err in thought process to think that it did. The Universe is not expanding. This is also a myth. They are both theories...and not very good ones either."Unquote.

Hmmm " the Universe is NOT expanding" why does he say this? Because he believes in God, as the maker of everything. God makes no mistakes, hence what is know has been forever. The Universe is expanding and we can see this as fact. I will not throw out a claim that something is not so because I say so, as some do. Faith is just that faith, but science works a wee bit different.

[+joc]

The big bang is a theory yes, and it does hold the scientific community together. What Joc is saying (if I may be so bold) is that God created the universe and the reason why is still unknown. Science has many answers or theories based on mathematical equations that some see as a way of dismissing god. The answer to some, is what is your faith or what can science "prove" or show as proof. Many hold onto faith and thats fine, until it contradicts what can be proven. Hence we see this.

Quote

"The Big Bang is a myth. It never happened. It is an err in thought process to think that it did. The Universe is not expanding. This is also a myth. They are both theories...and not very good ones either."Unquote.

Hmmm " the Universe is NOT expanding" why does he say this? Because he believes in God, as the maker of everything. God makes no mistakes, hence what is know has been forever. The Universe is expanding and we can see this as fact. I will not throw out a claim that something is not so because I say so, as some do. Faith is just that faith, but science works a wee bit different.

Thanks for attempting to explain my words. Actually, my thoughts have nothing to do with my Faith. The reason I say what I say is that I believe it to be preposterous to even think that we have a clue about the origin of something that is so incomprehensibly infinite as the Universe. We can't even get our 'computer's' minds around it...much less our own.

There are literally Trillions of Galaxies...each containing Billions of Star Systems....each Star System many light years away from each other....to even postulate that it is 'expanding' is ludicrous....how could we know...despite the best calculations of astronomers...one cannot say for 'certain' that the Universe is Expanding...what we can even see of the Universe is akin to seeing one inch in front of your face while walking in the midst of a sand storm in the Sahara Desert.

[Torgo]

Thanks for attempting to explain my words. Actually, my thoughts have nothing to do with my Faith. The reason I say what I say is that I believe it to be preposterous to even think that we have a clue about the origin of something that is so incomprehensibly infinite as the Universe. We can't even get our 'computer's' minds around it...much less our own.

There are literally Trillions of Galaxies...each containing Billions of Star Systems....each Star System many light years away from each other....to even postulate that it is 'expanding' is ludicrous....how could we know...despite the best calculations of astronomers...one cannot say for 'certain' that the Universe is Expanding...what we can even see of the Universe is akin to seeing one inch in front of your face while walking in the midst of a sand storm in the Sahara Desert.

We can tell the universe is expanding because of three separate lines of evidence.

Firstly, we see a redshift of far away galaxies. The light from their stars has longer and longer wavelengths the further away they are from us, all the way down to infrared and microwaves for the furthest ones we can detect at all. This can be construed as being from the Doppler effect, where the light of things moving away from us is stretched as it is emitted. It can also be construed as space stretching and in the process lengthening the wavelengths. Either way it indicates the universe is expanding.

Secondly, we can only see a finite distance away in space. Since light has a finite speed, we are also seeing back into a finite time. As we look closer and closer to that distance we see different things. Galaxies behave differently, and things are denser as a whole.

Thirdly, at the very limit of what we can see, we see the cosmic microwave background radiation. This is a rather uniform microwave radiation coming equally from every direction in the sky. It has a characteristic spectrum. A little background: All objects emit radiation just due to thermal energy. This light radiation has a peak emission rate at a wavelength that goes down as temperature goes up, and a shape that changes with temperature as well. When we look at the background radiation, it has a peak at the LOONG wavelength microwaves - but is shaped like the emission curve for a very hot gas, hot enough to ionize hydrogen. Thus, the universe was, about 13.7 billion years ago (we can tell from the redshift, it increases at a well understood rate with distance and thus duration back in time) , extremely hot and since then the radiation has redshifted on its way everywhere.

Together this indicates the universe used to be denser and 13.7 billion years ago was extremely hot. If we run the rate of expansion back we see that the observable universe would've occupied zero volume 300,000 years before the furthest radiation we can see - but the furthest radiation we can see indicates that it was released from a plasma which blocks light. We will never be able to directly see further back than that - but with this evidence it is safe to assume that the big bang (or at least some sort of expansion from a very hot and dense state) took place.

[sumthingnice60]

Thanks for attempting to explain my words. Actually, my thoughts have nothing to do with my Faith. The reason I say what I say is that I believe it to be preposterous to even think that we have a clue about the origin of something that is so incomprehensibly infinite as the Universe. We can't even get our 'computer's' minds around it...much less our own.

There are literally Trillions of Galaxies...each containing Billions of Star Systems....each Star System many light years away from each other....to even postulate that it is 'expanding' is ludicrous....how could we know...despite the best calculations of astronomers...one cannot say for 'certain' that the Universe is Expanding...what we can even see of the Universe is akin to seeing one inch in front of your face while walking in the midst of a sand storm in the Sahara Desert.

The universe is expanding because we have methods to tell that galaxies are moving away from us, as explained by torgo. What is even more surprising, and perhaps counter-intuitive, is that the galaxies are actually accelerating which means that there is a strong gravitational field attracting all of the galaxies.

EDIT : torgo explained most of it.

Edited December 13, 2007 by sumthingnice60

[+joc]

Torgo,

I know you think you believe what you just wrote. But the universe isn't 13.7 Billion years old either. There is no way to know that. For all we know....the farthest Galaxies we know of are just scratching the surface of what is.

I have the answer:

There is only one star. The sun. Everything else is done with mirrors!

I don't even pretend to know all the scientific knowledge that went into your post and how the theories of the BB and the EU are arrived at. I don't care either. What I know is that we don't know. We can't know. We know what we think we know...but we don't know.

But just for fun...let's say that BB and EU are correct. So what you are telling me is that about 14 billion years ago it all began....for the first time? or the hundredth billionth time? I mean really...what's 14 billion years? It isn't even a fraction really of 478 Trillion years. ANd how fast was the Universe traveling at the moment of the BB? Faster than the speed of light itself? That btw is a question I am really actually asking you...because if it wasn't faster than the speed of light itself...how could there be galaxies trillions of light years away? And if it was faster than the speed of light...well, just explain that one plz.

[Torgo]

Torgo,

I know you think you believe what you just wrote. But the universe isn't 13.7 Billion years old either. There is no way to know that. For all we know....the farthest Galaxies we know of are just scratching the surface of what is.

I have the answer:

There is only one star. The sun. Everything else is done with mirrors!

I don't even pretend to know all the scientific knowledge that went into your post and how the theories of the BB and the EU are arrived at. I don't care either. What I know is that we don't know. We can't know. We know what we think we know...but we don't know.

But just for fun...let's say that BB and EU are correct. So what you are telling me is that about 14 billion years ago it all began....for the first time? or the hundredth billionth time? I mean really...what's 14 billion years? It isn't even a fraction really of 478 Trillion years. ANd how fast was the Universe traveling at the moment of the BB? Faster than the speed of light itself? That btw is a question I am really actually asking you...because if it wasn't faster than the speed of light itself...how could there be galaxies trillions of light years away? And if it was faster than the speed of light...well, just explain that one plz.

We've got no idea as to the size of the universe. Personally, unless evidence appears to the contrary I'm going with infinite. I do so because as near as we can tell space is not curved at large scales, meaning it cant curve around in a fifth dimension to double back on itself. However, what matters is that we can only see a finite distance in every direction, indicating that light has had a finite time to travel which we can calculate.

We also cannot know anything, at least with current physics, about any possible other universes. It's just something we can't test right now. So I can't really say anything about that than it is entirely possible they exist but it doesn't really enter into study of this universe except possibly for the exact instant it came into being.

The thing about the big bang is that it appears to be a question of SPACE stretching rather than objects moving through space; objects moving though space have to obey general relativity while if there is something driving changes in space itself, space can do whatever it wants. We see this as incredibly intense redshifts at the edge of the observable universe, using the doppler effect we see this as an apparent velocity approaching that of light.

We CANNOT see anything trillions of lightyears away. The "cosmic horizon", how far we can see, is about 50 billion lightyears away. This is what you get when you take the distance we can see and use some calculus and integrate the expansion rate times distance - everything we can see (much of which is far back in time) will have expanded from 13.7 billion lightyears in radius to 50 billion lightyears in radius by now.

[+joc]

We've got no idea as to the size of the universe. Personally, unless evidence appears to the contrary I'm going with infinite.

Respectfully, how can one limit an infinite universe to a finite number of 13.7? I understand from the next quote how one arrives at that number but...it makes no sense to me. Not really. Not mathmatically speaking (although I haven't a clue about calculus) but 'logically' speaking.

This is what you get when you take the distance we can see and use some calculus and integrate the expansion rate times distance - everything we can see (much of which is far back in time) will have expanded from 13.7 billion lightyears in radius to 50 billion lightyears in radius by now.

And this is because 'space' is expanding?

[rideron]

The big bang is NOT a bunch of mass originating at one point and spweing out into space. As near as we can tell matter and space originated together with matter embedded in space throughout. Since that time the space has stretched moving the matter further and further apart decreasing the overall density of the universe and stretching light out to longer and longer wavelengths - hence the Doppler shift.

The classic example to ilustrate this is a balloon. Take a sharpie and put little dots all over it. These are collections of matter, like galaxies. Blow up the balloon, or take your hands and stretch it out - the dots do not explode out from any point, they just get further and further away while the rubber they're on gets bigger.

As near as we can see the universe has no edge. We can only see a finite distance away but that is because light has had a finite time to travel since the universe became transparent to light when it cooled down enough for the initial plasma to combine into neutral gas molecules.

The background radiation we see is NOT the radiation from the (nonexistant) "Explosion" of the big bang. What it IS is the heat glow of the universe at the moment it became transparent to light, redshifted down into the microwaves by the expansion of space.

O.K. so "matter and space originated together with matter embedded in space throughout" and I get the illustration of the expanding balloon with dots all over it; but you are sidestepping my original question: To use your analogy we have an 'expanding balloon', but what is it into which the balloon is expanding???? If all reality creation matter and space is the balloon itself????

[+joc]

O.K. so "matter and space originated together with matter embedded in space throughout" and I get the illustration of the expanding balloon with dots all over it; but you are sidestepping my original question: To use your analogy we have an 'expanding balloon', but what is it into which the balloon is expanding???? If all reality creation matter and space is the balloon itself????

I don't think the balloon is a good analogy at all because the space on the 'inside' of the balloon doesn't stretch..only the balloon itself.

I do understand however that if the Big Bang occurred...then the Light from that Explosion would be traveling outwards at the speed of light...but the star systems themselves would be traveling...?...how fast is the Universe therefore theorized to be expanding?

And how do we have any clue where we are exactly in an infinite Universe? If we don't have a clue...how can we theorize about the beginning of it?

Edited December 14, 2007 by joc

[Torgo]

I don't think the balloon is a good analogy at all because the space on the 'inside' of the balloon doesn't stretch..only the balloon itself.

I do understand however that if the Big Bang occurred...then the Light from that Explosion would be traveling outwards at the speed of light...but the star systems themselves would be traveling...?...how fast is the Universe therefore theorized to be expanding?

And how do we have any clue where we are exactly in an infinite Universe? If we don't have a clue...how can we theorize about the beginning of it?

You're right about the balloon analogy, it falsely implies that there is a known volume with at least one more dimension containing our universe. All we can tell about our universe is that the coordinate system we call space is expanding. In fact, the idea that the universe is somehow expanding into another higher-dimensional volume is probably meaningless - it can completely be described as the coordinate system shifting (more space appearing between any two given points) with time.

As for light from the "explosion", again there was no explosion. We just started out hot and dense and have ended up cold and diffuse. However, this hot and dense state certainly did put out a lot of light and radiation just from blackbody radiation... and we see this coming at us from all directions at once, EXTREMELY uniformly. This is the cosmic microwave background radiation I mentioned earlier, the light that's spectrum indicates that it was extremely hot when the light was emitted but as space has stretched the light has redshifted all the way to the microwaves.

Asking "where we are in an infinite universe" is meaningless - there are an infinite number of places to be and you cant pick one as special over any other. However, again we probably cannot ever know the true extent of the universe just because of the speed of light. We can only see a finite distance in any given direction. If the universe wraps around and is interconnected, like the surface of a sphere, EVENTUALLY light will be able to make it all the way around but who knows how big it could be. The fact though that space on large scales is very nearly euclidean seems to indicate that the universe is either infinite or extremely large.

[+joc]

You're right about the balloon analogy, it falsely implies that there is a known volume with at least one more dimension containing our universe. All we can tell about our universe is that the coordinate system we call space is expanding. In fact, the idea that the universe is somehow expanding into another higher-dimensional volume is probably meaningless - it can completely be described as the coordinate system shifting (more space appearing between any two given points) with time.

As for light from the "explosion", again there was no explosion. We just started out hot and dense and have ended up cold and diffuse. However, this hot and dense state certainly did put out a lot of light and radiation just from blackbody radiation... and we see this coming at us from all directions at once, EXTREMELY uniformly. This is the cosmic microwave background radiation I mentioned earlier, the light that's spectrum indicates that it was extremely hot when the light was emitted but as space has stretched the light has redshifted all the way to the microwaves.

Asking "where we are in an infinite universe" is meaningless - there are an infinite number of places to be and you cant pick one as special over any other. However, again we probably cannot ever know the true extent of the universe just because of the speed of light. We can only see a finite distance in any given direction. If the universe wraps around and is interconnected, like the surface of a sphere, EVENTUALLY light will be able to make it all the way around but who knows how big it could be. The fact though that space on large scales is very nearly euclidean seems to indicate that the universe is either infinite or extremely large.

Very interesting Torgo! The word Bang...implies an explosion of sorts...which is how I have always heard and perceived it. Your description of it makes since to me...especially in the 'belief' that I have that God created the Universe....in Genesis before the Earth and Sun were created God said ...let there be light. Perhaps this was the light you talk about...it also describes Darkness upon the face of the Deep. If there was Darkness upon the face of the Deep...and God said let there be Light...could that not be interpreted as your definition of Big Bang?

Edited December 16, 2007 by joc

[Cradle of Fish]

I don't even pretend to know all the scientific knowledge that went into your post and how the theories of the BB and the EU are arrived at. I don't care either. What I know is that we don't know. We can't know. We know what we think we know...but we don't know.

If we all thought like that we'd all still be living in caves in Africa, scared of fire.

You're quite confident that we dont know all this, how do you know we dont know? You cant know. The only thing we know is that you cant know whether or not we dont know.

[+joc]

If we all thought like that we'd all still be living in caves in Africa, scared of fire.

You're quite confident that we dont know all this, how do you know we dont know? You cant know. The only thing we know is that you cant know whether or not we dont know.

Were we ever really scared of fire? We cannot 'know' the origin of the Universe. We can theorize, we can guess, we can come to a general agreement of theories...but we cannot know. Can one explain with any certainty what existed prior to the origin? Many just hear the theory and except it as fact. I accept as fact that one can theorize but not know with absolute certainty.

[Torgo]

Were we ever really scared of fire? We cannot 'know' the origin of the Universe. We can theorize, we can guess, we can come to a general agreement of theories...but we cannot know. Can one explain with any certainty what existed prior to the origin? Many just hear the theory and except it as fact. I accept as fact that one can theorize but not know with absolute certainty.

You can say the same thing about any scientific idea or discovery. We do not "know with absolute certainty" that electrons exist. We do not even "know with absolute certainty" that gravity always works the way the law of gravity describes it does. However, the theory of quantum electrodynamics explains down to as many decimal places we can measure exactly how electrical charge and current behaves, and the theory of gravity has, so far, explained large-scale motion in the universe. The big bang theory came about the same way as these other theories - looking at evidence, proposing models to explain them, and testing these models. The big bang theory has held up over and above any other model of the universe's history and origins. That is why we believe it is true. If more evidence that comes to light that shows it cannot be true, it will be discarded. However, it has been rather closely confirmed.

Example: the redshift of galaxies has been known for a long time, and it suggested that some time in the distant past the universe was quite dense. When you squeeze gas into a smaller volume, it heats up. Therefore, the universe should've been hot long ago.

The microwave background radiation was not well measured until the COBE satellite went up to measure it. When they measured it, they looked at the shape of its spectrum because they knew they could not use its frequency to look at the temperature of the early universe - it would have redshifted. If the universe used to be hot, the shape of the spectrum should be that of a hot gas while being shifted to the long wavelengths. And that is exactly what they found.

Edited December 19, 2007 by Torgo