Starship Asterisk*

Isn’t it true that we can only observe a limited distance into space? We have no knowledge of what exist beyond that. I cannot accept that if we could travel to the most distant point of light we would find a great barrier of nothingness beyond it. Where did this concept come from?

Your quite right we can only observe as far as light has had time to travel from since the birth of the Universe, naively this would be a sphere 13.7 Billion light years in radius, however its actually about 10 times bigger if i remember right. This is just due to various effects to do with inflation etc.

This comes from wanting to have an infinte universe (in extent) but not in matter. I dont think this makes sense, I was arguing against the possibility that the universe is infinite in extent but not infinite in matter, because as you point out it makes no sense. If you believe that the universe is infiinte in extent but not in mass then we must live in a priviledge place in the universe, a very special place where the density of matter is not approximately zero as it must be everywhere else.

The BB however does make sense, the Universe is finite in both spatial extent and matter. In a BB universe, it is not possible to travel to the edge of the universe, as space is itself curved, there is no edge, you merely keep travelling until you end up where you started from.

The point is you cant go outside the Universe, there is nothing out there in the sense that you could understand, every atom in your body is a product of this universe and obeys its laws, outside its probable that you simply couldnt exist. The laws of physics could well be different and everything would break down.

You wrote: "The distribution of matter would have to be very non-uniform in fact it would have to be infinitely non random just for anything to exist". -Please explain!

Think about it this way, what is any number that isnt infinite divided by infinity? Answer zero, essentially.
So think about the density of matter in such as universe, it must be essentially zero as well, so if we look out and see that there are large amounts of matter about what does this imply?

One of two possibilities, that the universe is not in fact infinite in size.

Or that we live in a very unusual place in the universe, where somehow huge amounts of mass have collected despite the very low average density of the universe. This seems pretty unlikely doesnt it?

“If you believe that the universe is infinite in extent but not in mass then we must live in a privileged place in the universe, a very special place where the density of matter is not approximately zero as it must be everywhere else”.

–Is this so hard to believe when we live on a privileged planet that is capable of life? That special place you refer to is simply where a BB happened. Which may or may not be privileged but it is where life as we know it exist. Am I misunderstanding your reference to mass=zero. The BB is not theorized to have been initiated from dense matter but rather its birth was the result of or reaction of energy-right?


Can the BB survive in a theory of infinite extent but not mass? To imply that the universe has a shape also implies that it is limited in its existence. Can you explain (briefly) why it is theorized that space/time is curved?

“In a BB universe, it is not possible to travel to the edge of the universe, as space is itself curved, there is no edge, and you merely keep traveling until you end up where you started from”.

Is this true with light? Does it merely end up back to where it started?
Is this true no matter what direction you travel? How can space be curved in upon itself? How is this theory tested; what is the supporting evidence? So if I had the ability to look far enough all I would see is my backside?

If one cannot leave “this” universe and all the atoms in my body are only recognized in “this” reality –then aren’t we implying a multi-universe exists?

I dont at all find it difficult to believe that the Earth is a priviledged place, it may be that the whole Universe is priviledged too, its called the weak anthropic principle.

http://en.wikipedia.org/wiki/Anthropic_principle

A way to understand this is simply to say there may have been many BBs, but only a small subset have physical laws and quantities that allow the formation of complex life.

Immediately after the BB, there was no mass in the Universe, only energy, it was only after the Universe had cooled that the energy created the matter we see today, mostly Hydrogen, Helium and traces of Lithium.

The 'shape' of the Universe is entwined with its eventual fate.
See http://en.wikipedia.org/wiki/Flatness_problem

As for light running into the back of itself, that would tend to be true if the Univers wasn't expanding, but in an expanding Universe there are regions far enough away to be receding from us as greater than light speed which means the light can never cross the whole Universe. Space can expand faster than the speed of light.

If one cannot leave “this” universe and all the atoms in my body are only recognized in “this” reality –then aren’t we implying a multi-universe exists?

No, what I'm saying that its essentially irrelevant, the likelyhood is that if other Universes did exist there is no way to ever feel their influence. So they may as well not exist. By definition the Universe contains all that was,is and ever will be. If you start talking about other Universes interfering with our own, what your really talking about is other dimensions.

Hello All

Smile,,,,,,,,,,,,,,,,,,,,,,,,,thats all can do for now.

The above ideas I disagree with. But thats me.

I can only advice that people should get up to date observations and comments and not live in the past.

There is a paper coming out soon on the Big Bang. I forgot the writers name. I will look it up and come back to you.
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Bmaone23,,,,,,,,,,,,,,,,,,,,,,,,,,ooops your right about gravity

Hello All

Not that I agree with the Big Bang

Here is some info on the Big Bang

http://hubblesite.org/newscenter/newsde ... s/2006/44/
Tracing the Evolution of the First Galaxies in the Universe

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A systematic search for the first bright galaxies to form in the early universe has revealed a dramatic jump in the number of such galaxies around 13 billion years ago. These observations of the earliest stages in the evolution of galaxies provide new evidence for the hierarchical theory of galaxy formation -- the idea that large galaxies built up over time as smaller galaxies collided and merged.

I just cannot see or understand this logic.


Am I missing something,,,,,,,,,,,,,,,,,maybe a sparkplug.

Its fairly simple Harry,

In a hierarchical Universe, small galaxies form first, they then merge to form larger galaxies. The results you report support this conclusion strongly. Here is why.

They see a lot of very bright galaxies at around 900Myr after the BB, but not many bright ones at 700Myr after the BB (i.e 200Myr earlier), now if galaxies as bright as those at 900Myr existed at 700Myr we should be able to see them. The fact that we dont see many at 700Myr implies that they dont exist at 700Myr, the reason why? Because at 700Myr there hasn't been time for the small galaxies to merge to form the bigger galaxies we can see later. At 700Myr most of the stars haven't yet formed and those that have are in small galaxies which are too faint to see with present telescopes. The JWST will be able to see them though.

Hope this clears things up.

Hello Astro


No ! its not as simple as it looks.

you say:

They see a lot of very bright galaxies at around 900Myr after the BB, but not many bright ones at 700Myr after the BB (i.e 200Myr earlier), now if galaxies as bright as those at 900Myr existed at 700Myr we should be able to see them. The fact that we dont see many at 700Myr implies that they dont exist at 700Myr, the reason why? Because at 700Myr there hasn't been time for the small galaxies to merge to form the bigger galaxies we can see later. At 700Myr most of the stars haven't yet formed and those that have are in small galaxies which are too faint to see with present telescopes. The JWST will be able to see them though.

Where did you get this info from?.
It does not seem logical.


Lets look at observations

http://antwrp.gsfc.nasa.gov/apod/ap040226.html

the galaxy cluster lies nearly 9 billion light-years away ... and so existed at a time when the Universe was less than 5 billion years old. A measured mass of more than 200 trillion Suns makes this galaxy cluster the most massive object ever found when the Universe was so young.

5 billion years to form to form 200 trillion suns. Think about for one sec. Something is wrong,,,,,,,,,,,,,what science are we using to make these theories.


http://antwrp.gsfc.nasa.gov/apod/ap040120.html

How could such a long string of galaxies form so early in the universe? Several new measurements of galaxies and clusters in the early universe are reporting structures involving galaxies and clusters that are larger than expected with the new standard "dark-energy" cosmology. The controversy centers on the inability of a dark-energy dominated universe to create such large structures. Fans of the old standard cosmology -- without weird but pervasive dark energy -- are hoping that these new measurements rule out the newly popular strange universe

http://antwrp.gsfc.nasa.gov/apod/ap040317.html

Detected light left this galaxy 13.2 billion of years ago, well before the Earth formed, when the universe was younger than 3 percent of its present age

People assume that the Big Bang is correct, than proceed to expalin observation as per the Big Bang. I just do not understand these scientists.


http://antwrp.gsfc.nasa.gov/apod/ap970209.html

Galaxies like colorful pieces of candy fill the Hubble Deep Field - humanity's most distant yet optical view of the Universe. The dimmest, some as faint as 30th magnitude (about four billion times fainter than stars visible to the unaided eye), are the most distant galaxies and represent what the Universe looked like in the extreme past, perhaps less than one billion years after the Big Bang

Think about it for a sec...........one billion years to form millions of galaxies.
Is the Big Bang the Crank theory of the 20th Century.


http://antwrp.gsfc.nasa.gov/apod/ap960628.html

Researchers believe that the faint reddish smudge indicated by the arrow in the image above is a candidate for the most distant known galaxy which may have existed only a few hundred million years after the Big Bang

http://antwrp.gsfc.nasa.gov/apod/ap950907.html

This Hubble Space Telescope image of a group of faint galaxies "far, far away" is a snap shot of the Universe when it was young. The bluish, irregularly shaped galaxies revealed in the image are up to eight billion light years away and seem to have commonly undergone galaxy collisions and bursts of star formation

Again, how much time to you require to form galaxies and than have them colliding.

http://hubblesite.org/newscenter/newsde ... 4/19/text/
Spitzer Leads NASA's Great Observatories to Uncover Black Holes, Other Hidden Objects in the Distant Universe

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Full press release text:

View this
image
Astronomers unveiled the deepest images from NASA's new Spitzer Space Telescope today, and announced the detection of distant objects — including several supermassive black holes — that are nearly invisible in even the deepest images from telescopes operating at other wavelengths.

Dr. Mark Dickinson, of the National Optical Astronomy Observatory, Tucson, Ariz., and principal investigator for the new observations, said, "With these ultra-deep Spitzer images, we are easily seeing objects throughout time and space, out to redshifts of 6 or more, where the most distant known galaxies lie. Moreover, we see some objects that are completely invisible, but whose existence was hinted at by previous observations from the Chandra and Hubble Observatories."

Seven of the objects detected by Spitzer may be part of the long-sought population of "missing" supermassive black holes that powered the bright cores of the earliest active galaxies. The discovery completes a full accounting of all the X-ray sources seen in one of the deepest surveys of the universe ever taken.

This detective story required the combined power of NASA's three orbiting Great Observatories — the Hubble Space Telescope, Chandra X-ray Observatory, and Spitzer Space Telescope. Each observatory works with different wavelengths of electromagnetic radiation, from high-energy X-rays with Chandra, through visible light with Hubble, and into the infrared with Spitzer. Together, these telescopes yield far more information than any single instrument.

All three telescopes peered out to distances of up to 13 billion light-years toward a small patch of the southern sky containing more than 10,000 galaxies, in a coordinated project called the Great Observatories Origins Deep Survey (GOODS). Chandra images detected more than 200 hundred X-ray sources believed to be supermassive black holes in the centers of young galaxies. The X-rays are produced by extremely hot interstellar gases falling into the black holes.

This small patch is the size of a rice seed. Imagine how many rice seeds are out there.

Now if we see 10,000 galaxies in just one little rice seed, how many billions are out there.

Knowing this and that they only have one billion years to form. They need "GOD" 's hand to magically form all these galaxies if not GOD's hand than the magically fantasy ideas from the Big Bang theory.

Have I got all the answers?,,,,,,,,,,,,, No way in hell.

But that does not mean I stand bye and see ideas such as the Big Bang give some fantasy ideas.



http://www.spacetelescope.org/images/html/opo0520a.html

Gazing deep into the universe, NASA's Hubble Space Telescope has spied a menagerie of galaxies. Located within the same tiny region of space, these numerous galaxies display an assortment of unique characteristics. Some are big; some are small. A few are relatively nearby, but most are far away. Hundreds of these faint galaxies have never been seen before until their light was captured by Hubble.

http://www.spacetelescope.org/images/ht ... 0406b.html

Astronomers are hoping to strike it rich by finding some of the farthest known galaxies, existing perhaps 400 million years after the big bang. To find them, astronomers must combine the infrared and visible-light images. The remotest galaxies will only appear in the infrared image. If discovered, these record-breaking galaxies may offer clues to the emergence of galaxies when the universe was only 2 to 5 percent of its present age.

Astronomers are looking with the eye of a Big Bangger, and sometimes that tunnel vision will restrict their observations and aslo their writing with the intent of assuming that the Big Bang is correct.

I can add more observations with super clusters and so on. This for later.


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for those intersted
The Hubble Deep Field
http://www.stsci.edu/ftp/science/hdf/hdf.html

Where did you get this info from?.
It does not seem logical.

From the article and the paper. How does the explanation not seem logical? Please explain the problem.

It is very simple Harry, galaxies big enough (and therefore bright enough) to be seen with present technology have not had time to form 700My after the BB. But after another 200Myr galaxies are big enough to be seen, because they have had more time to form stars and merge with each other. Simple.

5 billion years to form to form 200 trillion suns. Think about for one sec. Something is wrong,,,,,,,,,,,,,what science are we using to make these theories.

Your quite right something is wrong, you have mis-interpreted what you have read again. It says the cluster has a mass of 200 trillion suns, not the stars. This mass includes all of the mass in the cluster, BHs, gas, stars and Dark matter. As we know luminous matter only makes up around a few per cent of the mass of clusters, say 5% or 10 Trillion solar masses, the rest is hot x ray gas and DM.

These masses are determined by simple physics, you measure the velocities of all of the galaxies in the cluster (correcting for the fact that you can only measure the line-of-sight velocity), these velocities can then be used to work out the gravitational potential that is stopping the cluster flying apart. You can also use the temperature of the Xray emitting gas to work out the mass, because the gas should be expanding something must be holding it in place, that something is gravity. Both methods agree very well.

The quote talks about a galaxy cluster, so that is something with hundreds of galaxies. We observe in the MW that ~1Solar mass per year of stars are formed, however in younger galaxies, or interacting ones (like the ones found in distant clusters), the amount of stars formed per year can often reach 1000-10000 solar masses per year.
So to produce 5% x 200 Trillion = 10 Trillion solar masses of stars in 5Gyr means that we must produce 2000 solar masses per year, spread through perhaps 500-1000 galaxies, not really that difficult a proposition even for passively evolving MW type galaxies, which these galaxies definitely aren't.

People assume that the Big Bang is correct, than proceed to expalin observation as per the Big Bang. I just do not understand these scientists.

Thats rubbish, people take observations then they see how the fit to different ideas, the fact is nothing else proposed has anything remotely near to the predictive power of the BBT. Or can even fit the observations to be honest.

Again, how much time to you require to form galaxies and than have them colliding.

Answer not very long, you misunderstand so much about the Early universe Harry. Think about it a bit more, dark matter was still present in the ratio (to normal matter) it is now, but Dark energy was negligible (it didnt begin to become important till several Gyr ago), the Universe is also much smaller than it was now, so the density was higher.

What do all these facts lead to? Gravity between objects is stronger because the density is higher (so they are closer), so structures form much more rapidly than in the nearby Universe. Remember gravity is an inverse square law, so it you half the separation between objects the Force quadruples. You can form a lot very quickly like this.

The problem you have conceptually here Harry is that you are doing exactly what you accuse astronomers of, you are trying to fit the observations to fit your theory. Your eternal unchanging universe would predict no difference in density Gyr ago so you couldnt form large structures, but it is a very natural consequence of the BB. One that drops out of computer simulations every day.

Now if we see 10,000 galaxies in just one little rice seed, how many billions are out there.

Knowing this and that they only have one billion years to form. They need "GOD" 's hand to magically form all these galaxies if not GOD's hand than the magically fantasy ideas from the Big Bang theory.

It doesnt matter how many galaxies are out there Harry they all form at the same time, so why would it make a difference if there were 10 or ten billion?, its not like the each form in sequence, where each galaxy has to wait its turn. They each form independently and each have a billion years to form, not that difficult to understand is it? Think about it Harry as I have said before you can have star formation rates of 1000 solar masses per year, in a billion years you can therefore have a galaxy of 1 Trillion solar masses, not too difficult to achieve really.

I dont know where the God part comes from, but no astronomer invokes God to explain anything. I can only assume you misread the name of the survey GOODS, for Great Observatories Origins Deep Survey.

Hello Astro

I expected that logic from you and maybe your right.

What happens with the logic when we see 15 Billion light years and than 20 billion and find existing galaxy formations.

I do not think there was a Big Bang and therfore not an early Universe.

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What worries me is that there are many Big Bang people that will explain the BB to such an extent that they make it believable.

What happens with the logic when we see 15 Billion light years and than 20 billion and find existing galaxy formations.

Answer: We won't, if we could how come we can't see any stars that old in the nearby Universe? All the stars that have been examined have ages consistent with < 13Gyr. It would be very easy to spot stars with ages much greater than this, i.e 20Gyr, we don't see them. This implies one of two things: that we live in a very "special" young part of the universe, or that the whole observable Universe is young.

Of course the evidence you talked about is pretty conclusive too, we should be able to see large galaxies 700Myr after the BB, we don't, because they don't exist.

Anyway, within 10 years we will know if you are correct, the JWST would be able to see objects as old as you suggest if they exist.

astro_uk wrote:

What happens with the logic when we see 15 Billion light years and than 20 billion and find existing galaxy formations.

Answer: We won't, if we could how come we can't see any stars that old in the nearby Universe? All the stars that have been examined have ages consistent with < 13Gyr. It would be very easy to spot stars with ages much greater than this, i.e 20Gyr, we don't see them. This implies one of two things: that we live in a very "special" young part of the universe, or that the whole observable Universe is young.

Of course the evidence you talked about is pretty conclusive too, we should be able to see large galaxies 700Myr after the BB, we don't, because they don't exist.

Anyway, within 10 years we will know if you are correct, the JWST would be able to see objects as old as you suggest if they exist.

I didnt know that we could acurately tell the age of a star? I know a star's age can be estimated by the evolutionare stage it is in; and the elements in its core; but it is still an estimate. Is it not?
Orin

Hi Orin

Yes its still an estimate, there are very few absolutes in astronomy. There are however pretty good reasons why we don't think there are stars older than ~13 Gyr. The first is simply that all of the estimates of a stars age should be able to predict what a star of say 0.5 Msun looks like after 50Gyr, but we don't see any evidence for stars that are consistent with this type of age. Now there are definitely complications with this approach because stars that can live this long will not tend to change very much after the first few hundred million years, but still we should with current levels of sophistication and large samples be able to see some evidence for stars older than 13Gyr.

Another very good reason is one of Harrys supposed "problems" with the BB, the age of globular clusters, all the stars in GCs formed at the same time, with a wide range of masses. We can look at GCs in the MW and nearby galaxies and find the most massive stars present. We always find that the most massive stars have masses slightly less than the Suns, this is because the lifespan of a star is inversely proportional to its mass, so all the more massive stars have already died. The lifespan of the most massive star in a GC age dates the formation of the GC. This means that the GCs formed roughly 11 - 13 Gyr ago, some are slightly younger, but none ever have a most massive star that is consistent with being older than 13 Gyr.

The other reason is simply a result of numbers, low mass stars are the most common stars, such stars can have a lifespan with constant output for a period in the range 10Gyr to 10 Trillion years. If the Universe really was much older than we think it is there should be vastly more of these old low mass stars than we observe.

Thanks for your input astro_uk. I wish the JWST was now. If there was a BB; we should be able to see the edge of our universe. Who knows what lies beyond?
Orin

orin stepanek wrote:Thanks for your input astro_uk. I wish the JWST was now. If there was a BB; we should be able to see the edge of our universe.

You're assuming the universe has an edge. That would be true if it was shaped like an expanding sphere (3D object).

However, if it is shaped more like the expanindg skin of a balloon (our 3 dimensions are the "skin" of some higher order shape), then it can be finite but have no boundary. This topology also allows for some parts of the universe to be receding from us faster than light whereas the expanding 3D sphere can't exceed the speed limit!

dcmcp wrote:

orin stepanek wrote:Thanks for your input astro_uk. I wish the JWST was now. If there was a BB; we should be able to see the edge of our universe.

You're assuming the universe has an edge. That would be true if it was shaped like an expanding sphere (3D object).

However, if it is shaped more like the expanding skin of a balloon (our 3 dimensions are the "skin" of some higher order shape), then it can be finite but have no boundary. This topology also allows for some parts of the universe to be receding from us faster than light whereas the expanding 3D sphere can't exceed the speed limit!

I'm assuming that if the universe we live in was indeed formed from a big bang that there would be a perimeter at the edge of the expansion. and that we would be able to see if there was anything beyond that. If the universe is expanding faster than the speed of light; then we couldn't possibly see to the fringes of the universe. If that's the case; we could only see out as far as the age of the universe no mater how large it is. In other words if the universe was 100 billion light years across and was only 13 billion years old; we could only see 13 billion light years out. That is also a possibility I never thought about. If the universe is expanding like a balloon; we should still be able to see beyond that with good enough telescopes. I don't see why not.
Orin

orin stepanek wrote:I'm assuming that if the universe we live in was indeed formed from a big bang that there would be a perimeter at the edge of the expansion. and that we would be able to see if there was anything beyond that.

...

If the universe is expanding like a balloon; we should still be able to see beyond that with good enough telescopes. I don't see why not.
Orin

Well, it's all back to the 'skin of the balloon' analogy. Imagine that all of space was represented by the skin of a balloon. You're a two-dimensional creature living on the two-dimensional surface of this balloon. This means you can move (and see) north, south, east, and west... but not up and down. In fact, the directions 'up' and 'down' don't even exist in your universe, and you cannot even visualize them (except as abstractions, like a human trying to imagine a fourth dimension).

Now... imagining you were that two dimensional creature... where is the edge of the surface of the balloon?

orin stepanek wrote:If the universe is expanding like a balloon; we should still be able to see beyond that with good enough telescopes. I don't see why not.

My post was very poorly written. Sorry about that. Qev's post is much better.

Have a look at this article. The explanation is about the same as that which Qev has put forward, but it also addresses the next question (which doesn't appear to have occurred to you yet).

If you can get your head around that, try skimming through this more technical paper. Scroll down to find the section headed "No Centre to the Expansion in 3-D Space" - don't worry, this bit is descriptive and fairly easy to follow.

If that whets your appetite, have a read of the rest of the paper. I've only skimmed it very cursorily, but the maths doesn't look too advanced. If you find that (the maths) hard to follow I think you will pick up the gist from the written text.

The balloon theory is OK except for one thing! If all the galaxies were NSEW and no up or down there would have to be voids where the up and down would be; tremendous voids. Because the universe is [at least in my universe] 3 dimensional I don't believe in the balloon theory. If the universe is expanding like a balloon eventually it will have to pop or deflate and fall back in on itself. I won't deny a belief in the balloon idea; if you feel that way; right now I don't buy that. Eventually, though you may be proven right. Still there would have to be voids that would have to be discovered. Did you ever watch a fireworks display where a star shell goes off and expands in every direction? Kind of like a balloon; but you can see the void in the center and the outside of all the stars. This should be detectable in the universe also; so I hope I live long enough to see deep space pictures from the JWST. We will learn so much more when that time comes to pass.
Orin

Hello All


Sorry that I'm away alot lately, my time is on a project for another few months.
I know some will say thank GOD for that

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Anyway

The age of stars,,,,,,,,,,,,,they go through phases and rejuvination and with all that the age of stars are very difficult to date.

Some look young,,,,,,,,,,,,after a supernova
others look old before a supernova or a nova.


The recycling affect changes the dating of the star and in actual fact we are not dating we note the phase or stage of that star.

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Similar with continental and oceanic plates.

Continental plates some are over 4 billion years
Oceanic plates are only a few hundred million years, due to the affect of recyling.

I think people should get more info of stars before they talk about the evolution of stars and galaxies.

Within the next year there will be a flood of new info on the market place for free.

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Some links on stars, again it does not mean I agree with the facts.

http://www-astronomy.mps.ohio-state.edu ... imass.html

http://www-astronomy.mps.ohio-state.edu ... rnova.html

http://dsnra.jpl.nasa.gov/origins/index.html

This one may be of interest to some.
Puny black holes can eject Milky Way's stars

http://www.newscientistspace.com/articl ... ef=dn10020

I emailed to the writer and put this question to him or her.

The ejected stars, could they be from the core of the Black holes or from the surrounding caught in the jet stream or maybe both.

I think people should get more info of stars before they talk about the evolution of stars and galaxies.

I think its amusing that you're telling us we should get more information on stars, those that actually have anything to do with astronomy know that your vague assertions are fantasy, yet your telling us to get more information. We could spend our lives getting more information but it wouldn't satisfy you because it won't fit your preconceived ideas.

Perhaps we should try to do things the lucid way around, you give evidence for what you claim is recycling of stars and we'll take a look at it.

I'm fairly certain you won't agree with those links, as they are pretty much textbook descriptions of stars lives, nothing about recycling there.

The black hole link is interesting. But the stars are not being physically flung out from within the BH. They are being ejected by gravitational two- or three-body interaction between a BH and a star or binary system. Its all to do with swapping of gravitational potential energy.
A jet from a BH couldn't eject a star, stars are not solid bodies, if the jet was strong enough it would simply evaporate the unfortunate star, it couldn't push the star.

As for the balloon theory, consider this:
Even a balloon has depth in its skin (Nit pickey I know) but if you think about it on the molecular level you can get a universe that is 15gyr thick but expands seemingly limitlessly.

But as far as the entire arguement goes, We'll probably never be able to travel beyond our own little wheel in the grand scheme of things, so it's probably moot.

orin stepanek wrote:The balloon theory is OK except for one thing! If all the galaxies were NSEW and no up or down there would have to be voids where the up and down would be; tremendous voids. Because the universe is [at least in my universe] 3 dimensional I don't believe in the balloon theory. If the universe is expanding like a balloon eventually it will have to pop or deflate and fall back in on itself. I won't deny a belief in the balloon idea; if you feel that way; right now I don't buy that.

Remember the conditions I set in the analogy: there IS no up or down. There are no 'tremendous voids' to see, because 'up' and 'down' don't even exist in 'balloon universe'. The only directions that exist there are NSEW. To the two-dimensional people living there, 'up' and 'down' are the same sort of mathematical abstraction that the fourth dimension would be to us in our three-dimensional universe.

But also remember it's just an analogy, and a fairly loose one at that. I'm simply comparing the 'shape' of the expansion of the universe with a lower-dimensional analogue. The universe, as far as we know, doesn't have any limit on how 'stretchy' it is, it doesn't pop or deflate... in fact it seems to just inflate faster with time. Also, our universe would be a three-dimensional version of the skin of the balloon, which is pretty much impossible for a human mind to visualize, since in order to perceive in accurately you'd need to be able to imagine in four dimensions.

Did you ever watch a fireworks display where a star shell goes off and expands in every direction? Kind of like a balloon; but you can see the void in the center and the outside of all the stars. This should be detectable in the universe also; so I hope I live long enough to see deep space pictures from the JWST. We will learn so much more when that time comes to pass.
Orin

That's actually the point I'm trying to make with the analogy above... the expansion of the universe is completely unlike the expansion of particles in an explosion.

In your fireworks example, the stars are being flung out from the central point into a pre-existing, empty space from a central point. But if the universe were like this, it would mean something very peculiar: Earth would have to be located exactly at the point where the explosion originated. Otherwise we wouldn't see what we do in the sky... distant galaxies all racing away from us, in all directions.

There's a problem there, however: even if it were an explosion of this sort, and we were, by some massive coinidence, right at the center of it, there's no reason we'd observe that, the further a galaxy is away from us, the faster it's receeding from us. The opposite would be true in an actual explosion.

The alternative is that space, itself, is what's expanding. Just like the skin of the balloon stretching to make the distances between the dots painted on it move apart, the fabric of the universe itself expands. If this is the case, it removes those two problems.

If the universe is the same everywhere (homogenous on large scales) and is expanding in this fashion, no matter where you are in the universe, you'll always see the same thing: distant galaxies all rushing away from you in every direction. This removes the 'special place' problem.

And since it is space that's expanding, the more space you have separating two distant galaxies, the more 'new' space is going to come into being between them over any given length of time. This means that, the further away they are, the faster they'll appear to be receeding from us.

Not to pick nits; but everyone talks about space expanding. Isn't it the universe that is expanding rather than space? I rather believe that space is infinite and that it is the universe that is expanding. I tend to separate the two.
Orin

astro_uk wrote:A jet from a BH couldn't eject a star, stars are not solid bodies, if the jet was strong enough it would simply evaporate the unfortunate star, it couldn't push the star.

While I agree that a black hole jet probably couldn't eject a star from the galaxy, I'd imagine they can probably push them about to some degree. Aren't supernova explosions in binary star systems known to generate 'runaway stars'?