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OK Fridger, if you want threads that are more interesting than the usual stuff in the users forum, I could sure use your help (and everyone else's) to help me through an understanding of an infinite universe.

If you ask the "typical" person on Earth today to state how big they think the universe is, some will say they have no idea. Some will say "Big", without quantifying it further. A few will be able to cite current knowledge of the observable universe's dimensions. Some will say it is quite small, with Earth at its center (28% of all Americans still believe the Earth is the center of a God-created universe and is less than 20,000 yrs old).

Some folks, however, will state that the universe is "Infinite". They have heard the term used to describe the size of the cosmos, and they are simply parodying what they've heard.

Unfortunately, virtually none of that last group of folks truly understand what an infinite universe means. I'm not sure I do

So ...... perhaps you can help me sort something out. It goes like this:

In an infinite universe, the dimensions of the universe have no beginning and no end. It just goes on ?€¦ and on ?€¦. and on ?€¦ FOREVER. Infinity requires that there is no edge to the universe. Space would just stretch ?€¦ for infinity, in every direction.

In an infinite universe, there are an infinite number of galaxies of stars. Although they reside in galaxies and come and go in definite life cycles, stars are un-ending in total number. Whenever you think you?€™ve counted the last star, there are always another million, billion, trillion septillion more stars just beyond the last one you counted, stretching on ?€¦ and on in space ?€¦ forever.

Latest research suggests that up to ?? of all stars may have planets. Thus, in a universe of infinite stars, there are also an infinite number of planets around them. That means that if you so desired (and had the time), you could search all of space to find another planet exactly like our own Earth. You might have to visit billions or trillions of planets, or even 10xe100 such planets ?€¦ but eventually, you would find an exact duplicate of Earth, to include the same types of land masses, oceans and the same types of life forms. That is the beauty of infinity ?€¦ you can search forever and never run out of places to look.

If you were not satified with finding one exact duplicate of Earth but sought to find two, you could do so. In fact, in an infinite universe, there are an infinite number of stars just like our sun, and an infinite number of Earths exactly like Earth.

Following this thinking, what is weirdest of all is the possibility that in an infinite universe, there are an infinite number of you ?€¦ personally! If you had infinite Earths to visit, you would eventually encounter one with humans that looked just like us. If you had the stamina (WHEW!!)?€¦ eventually ?€¦ you would find another living person who was your exact twin. In fact, since there is always another planet to visit, you would eventually discover the universe filled with an infinite number of people exactly like you ?€¦ residing on an infinite number of alternate Earths, many of them reading another forum posting just like this in some far off galaxy. The odds or probability of finding such a thing may approach infinity, but by its strict definition, an infinite number of you's do exist, if the universe were infinite.

Fortunately, it is not! I don't think I could take an infinite number of myself It is hard enough keeping track of who I am.

These are not new ideas, obviously. The Steady State Theory talks about an infinite universe, but I am not familiar enough with it to know if it ever visited the above questions.

OK, HELP! Have I theoretically got this right, or am I way off base? It makes such a fascinating discussion that I'd like to open my Astronomy course in the Autumn with the topic, and I want to make sure I get things "right" ... infinity-wise.

Eagerly awaiting your input!

Frank

Ok, i will eagerly answer!

fsgregs wrote: That means that if you so desired (and had the time), you could search all of space to find another planet exactly like our own Earth.

How can you search all of space of a universe if it's infinte as you propose?

I'm not sure why you're trying to understand an infinite universe when the universe isn't really infinite at all - you're just putting an obstacle in peoples' path to understanding it here.

All the problems about infinite earths and all that jazz disappear in a finite universe. (and also, the Steady State Theory is AFAIK complete hokum now - we know it began with a "Big Bang")

How can you search all of space of a universe if it's infinte as you propose?

You obviously cannot, but theoretically ....

'm not sure why you're trying to understand an infinite universe when the universe isn't really infinite at all - you're just putting an obstacle in peoples' path to understanding it here.

That is also the point. People will believe the universe is infinite, without realizing what it really means. By telling them what it means, they will hopefully realize the complexity of infinity and go on to something else.

Frank

Frank,

In my study of the infinite I have found that science tends to coorelate findings with the finite surroundings of our planet Earth... As in the study of the Earth and the nature of things you will find similarities in objects, people, and various life forms on this biosphere... As in the example of a snowflake, there is not one alike... A grain of sand... A blade of grass... And within this finite biosphere would an ant travelling amist the sea of sand see this as the world of the infinite?

When we peer out into space we see the stars as the ant would see the sea of sand... In our primitive understandings of the fourth dimention we relate space to the third... space is infinite yes, but I believe everything is truly relative... As our Earth is a member of a solar system, our solar system a member of a galaxy... Our galaxy a member of a Galactic Cluster... I believe our universe is similar in nature to a galaxy with a core and arms... We haven't the technology yet to precieve this but to me it seems logical... What we label the Universe in a sense is a mass of a billion or trillion galaxies like stars forming a spiral or globular shape which in turn orbits amist a sea of other universes or form maybe a larger more complex form known as a Cosmos... On into infinity... As we see relative to all things in our discoveries, everything has structure and boundries... Which in turn makes it easier to precieve our Universe and in turn the Cosmos itself... And beyond.... It also makes things simpler to understand... Setting aside fear of the unknown allows us to see more clearly...

Then there is other dimentions which lie in levels above or below the fabric of what we precieve to be reality... These dimentions as discovered and therised are aspects of mesure... Either of time or 'dimention' or beyond... The fifth as perposed is labelled the Tessarect... In science Fiction it has been formed into a perception of travel... Folding space or what not...

This is a very deep and foreboding concept: infinity... Bordering on philosiphy rather than fact... It seems our perceptions are the only true witness to a tangible universe... Faith otherwise is a belief in a creation... An orginizing force that instructs each particle of matter... I tend to believe in this as I cannot see a Universe based in chaos as a creative force... Granted that there is no substantial proof of creation... Its only proof is based in logic... A logic that precieves order must exist to form patterns in an infinite structure...

Ras:

I totally understand your thoughts. I too have similar "cosmic" perspective, and I am a firm supporter of the Big Bang and the nature of our universe et al. I can grasp that the universe may be multi-dimensional ... I have read articles on cosmic strings, etc. ...

In this thread, I don't want to confuse what may be true in the scientific sense, with what a theoretical infinite universe would mean. I simply want everyone who glibly replies that the universe is "infinite" in size, to realize what that would mean (i.e. - infinite stars, infinite planets, infinite Earths and infinite US)!

So ... when considering the theoretical concept of infinity ... would there be infinite galaxies, containing infinite stars, surrounded by infinite Earths, populated by infinite humans, looking just like us personally?

Frank

fsgregs wrote:

'm not sure why you're trying to understand an infinite universe when the universe isn't really infinite at all - you're just putting an obstacle in peoples' path to understanding it here.

That is also the point. People will believe the universe is infinite, without realizing what it really means. By telling them what it means, they will hopefully realize the complexity of infinity and go on to something else.

I don't believe that's a very good way to educate people. Far better I think to tell them how it ISN'T infinite, and what that means. It means that there isn't a 100% chance that there's another planet just like ours out there. It means that you don't waste time doing thought experiments that are moot - why imagine an infinite universe when it's not? There's plenty of facts to amaze your students without making up stuff that isn't true as an exercise in reverse psychology.

Don't boggle your students just for the sake of boggling them - that will just confuse them more. Instead, tell them that the universe is NOT infinite, that it IS therefore ultimately understandable, and that might encourage them more to go down the path of studying it than saying it's infinite and bewildering and utterly beyond our understanding. Because at least then they'll know it's not a losing battle.

(And I'm not sure this subject would get Fridger's attention much, it seems more like the wishy-washy philosophical, metaphysical, unscientific stuff that we're trying to discourage on this board...)

Malenfant:

OK. If the infinity of the universe is wishy washy, metaphysical junk to you, then please move on to another thread. No one is forcing you to comment here ... obviously!

FYI, students are people and most people LOVE to engage in such thought. So did Arostotle, Newton, Einstein and a whole bunch of other great thinkers who have contemplated the possible infinity of the universe.

As to my students getting confused, the point is that they already are ignorant and confused about what infinity means. I will teach them that the universe is NOT infinite, by not only spouting off some recent discoveries, but also by engaging them in the obviously exciting topic of what an infinite universe would mean. Trust me ... they will not be boggled, they will be enlightened!

Besides, the infinity of the universe has not been conclusively disproven. While the Big Bang may have a starting date, a host of Cosmologists have postulated that other universes must have existed prior to our current one, perhaps infinitely back through time and space. Since the characteristics of those other universes are totally unknown, they could be different from, or identical to our own.

As to the topic of an infinite universe being inappropriate for a forum board discussing Phsyics and Astronomy, I could not disagree more. If there ever was an important question in Astronomy, it is the size, age and scope of the universe.

Thanks for your thoughts though

Frank

fsgregs wrote:FYI, students are people and most people LOVE to engage in such thought. So did Arostotle, Newton, Einstein and a whole bunch of other great thinkers who have contemplated the possible infinity of the universe.

Yes, which is why it's squarely in the realms of philosophy, not science.

As to my students getting confused, the point is that they already are ignorant and confused about what infinity means. I will teach them that the universe is NOT infinite, by not only spouting off some recent discoveries, but also by engaging them in the obviously exciting topic of what an infinite universe would mean. Trust me ... they will not be boggled, they will be enlightened!

So teach them that it's not infinite then. Don't waste their time trying to get them to understand infinity when it's something that neither you nor I nor anyone else can begin to get our heads around.

Besides, the infinity of the universe has not been conclusively disproven.

Neither have UFOs or psychic powers or the Loch Ness monster. That doesn't mean that they're valid topics for scientific discussion though. Just because something hasn't been disproven doesn't mean that its' a worthy topic for discussion.

While the Big Bang may have a starting date, a host of Cosmologists have postulated that other universes must have existed prior to our current one, perhaps infinitely back through time and space. Since the characteristics of those other universes are totally unknown, they could be different from, or identical to our own.

As to the topic of an infinite universe being inappropriate for a forum board discussing Phsyics and Astronomy, I could not disagree more. If there ever was an important question in Astronomy, it is the size, age and scope of the universe.

Your first paragraph demonstrates exactly why it's unsuitable though. It's entirely unprovable, entirely subject to conjecture, and therefore entirely unscientific.

There's quite enough to discuss and learn about that we can prove and gather data about without having to delve into all this entirely conjectural stuff.

Max Tegmark discussed this in a fascinating article in Sci Am a while ago; he worked out that in an infinite universe, the nearest exact copy of you would be 10e10e29 meters away.

Malenfant wrote:Your first paragraph demonstrates exactly why it's unsuitable though. It's entirely unprovable, entirely subject to conjecture, and therefore entirely unscientific.

So there have never been things in the realm of science that were once considered unprovable... until someone "wasted" time doing "thought experiments that are moot" to perceive reality in such a way that such things COULD be tested? Are there no lines in science books saying, "It was considered an entirely untestable hypothesis until John Smith came along in 1845 and realized he could test it by..." etc?

Also, if I might point out a contradiction...

Malenfant wrote:...why imagine an infinite universe when it's not?

Malenfant wrote:It's entirely unprovable, entirely subject to conjecture, and therefore entirely unscientific.

In one, a definitive statement on the absolute NON-infinite nature of the universe. In the next, the whole concept is "entirely unprovable."

If you know for sure that the universe is NOT infinite...well, then it is provable. And, by your own rules of what is a permissble discussion, it is now worthy of discussion. If it is NOT provable, is it still not worthy of discussion? I would think it would make a wonderful topic for students. Specifically to discuss exactly WHY such a thing is not provable. Which would then include the implications of the various scenarios (as Frank gave us) and why those implications would be impossible to test.

There is much to be gained from exploring that subject - both in terms of exploring the current and theoretical limits of cosmology and understanding the scientific method.

Plus it's cool. What more could a teacher want?

Sure, your point is well taken about UFOs and psychic powers (sort of - but I'll get to that). However, the comparison is not quite fair. I would think the size of the universe is certainly a valid question for cosmologists to be discussing. And I was unaware that it was as 100% closed a case as you are making it. I am sure I am not alone in that. And that alone would make Frank's discussion valid. Clearly we cosmo-size fools need to be enlightened...

Personally, I would have liked someone more knowledgeable than myself on the subject to weigh in WHY the universe is not considered infinite at this time...as opposed to just telling Frank his topic was, essentially, a stupid waste of time.

As for UFOs....

Malenfant wrote:Neither have UFOs or psychic powers or the Loch Ness monster. That doesn't mean that they're valid topics for scientific discussion though

Well, I hate to say things like, "Well, that is just 100% wrong" but... well, that is just 100% wrong. Those things have not been disproven, true. But they easily COULD be proven (if they actually existed). Psychic powers CAN be tested for (and, in fact, many reputable schools have conducted empirical tests of the subject). A UFO could, indeed, land on the White House lawn. Our own Air Force conducted a years-long study of the phenomenon. The point is not whether those things are fashionable to study. The point is not what the studies to date have found (which is basically nothing). And the point is not whether the field has been dominated by kooks (we all know it has).

The point is, the subjects were valid scientific topics for study because there was phenonema out there that demanded an explanation.

Strange lights in the sky (often bizarre). Human intuition (often uncanny). UFOs? ESP? Maybe just ball lightning and the probabilities of coincidences. You seem to be saying we should not have bothered to look.

Speaking of which....

Malenfant wrote:Don't waste their time trying to get them to understand infinity when it's something that neither you nor I nor anyone else can begin to get our heads around.

Perhaps a little defeatist here? In a different era, would not someone be saying the same words about an empirical study of love...? The quantum nature of the atom? Four-dimensional space?

Bottom line, how do you know until you try? And, even if you fail, great things can come from the effort. Can we gain more from sitting back to ponder only those things we CAN "get our heads around" or by trying to go a little further?

Remember, truth is stranger than fiction as they say because in fiction, we are limited by our imaginations.

It's a free board and we're all free to post. Just as you were free to post that Frank's topic was an "obstacle" to "true understanding" of the subject. Just as you would have been free to post a contribution to that understanding...instead of simply telling him all the ways his approach was wrong - which became the theme of the topic.

I hope you take my final statement productively (since that is how it's meant) but... are you sure about what the obstacle truly was here?

Steve

OK guys:

Thanks to everyone, including Malenfant, for their comments, but this thread has gotten away from its original purpose (to help me understand if my reasoning on an infinite universe is reasonable). If Malenfant wants to move on to other more important topics on this board, it is time for him to do so.

So ... what do you guys think of my infinity reasoning?

Max: Do you remember how long ago that article appeared in Scientific American?


Frank

As difficult as it is to comprehend an "infinite" universe, I find it equally as hard to comprehend a "finite" universe.... for if it IS finite, then what is it that's 1 metre outside it's boundary? (anti-universe?)

Another thought:
I think it was Stephen Hawking, who suggested various multi-dimensional topologies for the universe, such as saddle shapes etc, in which the universe could be considered infinite in 3 dimensions, but closed and finite in further dimensions.

I think one analogy used, is to imagine the 3 dimensions of the universe as existing on the 2D surface of a balloon. If you travel in 3 dimensions, then it's "infinite" in the sense that you can never reach it's edge (ie. infinite in 3 dimensions, but finite in 4), in fact if it was possible to travel far enough, you'd end up back where you started, and yet it's finite in the sense that a balloon has a finite dimension to us. ie. It's infinite (or continuous) for anyone existing in 3 dimensions, yet closed and finite to a 4 dimensional 'being'.
(I think there has also been some experimental evidence suggesting a curvature of the 3D fabric of space on a cosmological scale)

It's nescessary to make a conceptual leap, in order to imagine the 2D surface of the ballon as representing the 3D universe we live in, and of course (outside of mathematics) it's impossible for us to visualise additional dimensions without imagining simplified analogies as above.

This is where the physicists amongst us may be able to help our understanding.

On the question of whether this is a worthwhile discussion, let's not forget that it's not so long ago they thought the earth was flat. So let's not stifle discussion of subjects just because they are not easy to comprehend, and don't forget that philosphy is the mother of all science.

fsgregs wrote:OK guys:

Thanks to everyone, including Malenfant, for their comments, but this thread has gotten away from its original purpose (to help me understand if my reasoning on an infinite universe is reasonable). If Malenfant wants to move on to other more important topics on this board, it is time for him to do so.

It is generally accepted that this universe is not infinite, so it's pointless to get people to try to imagine that it is. Other universes cannot be studied and are entirely conjectural, and therefore irrelevant unless some link can be proven between our universe and theirs to make them measurable or detectable. That's it.

I think I might just join Fridger in moving away from this board entirely if this sort of thing carries on... This sort of discussion is just pointless philosophical meandering that should have no place here IMO.

As far as I've been able to tell the finite/infinite question is still open, however the observable universe is finite.

Then again, at some point there are going to be regions which never had any effect on us and we never had an effect on those regions (i.e. we are completely outside their lightcone, and vice-versa), and thanks to the expansion of the universe never will. Therefore they are completely irrelevant to the observable universe. Positivists would then add to this "therefore such regions don't exist". Myself, I can't see how speculating on something that is completely irrelevant to any possible observation is useful.

Max: Do you remember how long ago that article appeared in Scientific American?

April 2003 (and my name is Steve, actually);

here is a full copy of the text.
http://www.elfis.net/phorum/read.php?f=3&i=22&t=22

Cosmologists assume that our universe, with an almost uniform distribution of matter and initial density fluctuations of one part in 100,000, is a fairly typical one (at least among those that contain observers). That assumption underlies the estimate that your closest identical copy is 10 to the 10e28 meters away. About 10 to the 10e92 meters away, there should be a sphere of radius 100 light-years identical to the one centered here, so all perceptions that we have during the next century will be identical to those of our counterparts over there. About 10 to the 10e118 meters away should be an entire Hubble volume identical to ours.

edited to add link

So... what do you guys think of my infinity reasoning?

I thought the reasoning laid it out very clearly and poetically. But I wonder if it is completely sound. For example, certain starting conditions favor certain outcomes - so all variations may not be possible.

chaos syndrome wrote:As far as I've been able to tell the finite/infinite question is still open, however the observable universe is finite.

Then again, at some point there are going to be regions which never had any effect on us and we never had an effect on those regions (i.e. we are completely outside their lightcone, and vice-versa), and thanks to the expansion of the universe never will.

Never? So that means:

1) Cosmologists completely understand the nature of that expansion?
2) That means that Einstein's theories (and the resulting light-cone issues) are the end all be all?
3) That means - without getting all kooky and outside mainstream science - that there are not LEGITIMATE avenues of inquiry in which those regions MAY factor into theory? Or, if not legitimate avenues now... the potential for legitimate avenues in the future?

I'm not asking to be a [offensive term deleted ...s.]. I'm being serious. Because it very much sounds to me like you are saying the majority of cosmologists would agree with this statement:

"Anything outside our light cone can never, ever affect anything inside it - and we will never, ever come to a new understanding of nature where, in certain circumstances, that may not be entirely true."

Again, not asking to be a [offensive term deleted ...s.]. But, since you clearly know more than me on the subject, I am legimitately curious to hear your thoughts (if you feel inclined and/or qualified to give them).

However, moving off-topic a bit, if cosmologists would NOT agree with that conclusion, I'm not sure how you came to this one....

chaos syndrome wrote:Myself, I can't see how speculating on something that is completely irrelevant to any possible observation is useful.

In any case, I thought I had already answered this issue in a previous post. There is MUCH usefulness there. Such discussions may not lead to NEW knowledge...but they can help people understand what is already know by peering at it from another side.

Malenfant wrote:This sort of discussion is just pointless philosophical meandering that should have no place here IMO.

No, what has no place here is the constant attacking of people for making inquiries in good faith. Sure...do people sometimes raise issues that are non-sensical scientifically-speaking? Yes. But it seems very clear to me the proper thing to do would be to either:

A) Take the time to explain to them HOW such a thing is not possible (and thereby TEACH them something new) - as opposed to just saying, "That's dumb - we shouldnt' talk about that."

(Chaos did that to some extent - mentioning light cones, and positivism - and, in doing so, increased the collective knowledge of the board - if, at the very least, by introducing terms whereby a curious reader could start to to there own searches.)

B) Ignore the post.

Frank, you are a better man than me. And I'm sorry to bring this up again. I understand you want to steer this back to its original purpose (that's why I wrote two-tiered response - to keep that aspect going - and I was interested). But it does this "society" no good when its members start abusing other members inquiries for no good reason. Especially a member like you have done so much for this community. Malenfant is pretending like there IS some "greater good" of the board he is protecting. Not even remotely close.

For example....

Malenfant wrote:Other universes cannot be studied and are entirely conjectural, and therefore irrelevant unless some link can be proven between our universe and theirs to make them measurable or detectable. That's it....This sort of discussion is just pointless philosophical meandering that should have no place here IMO.

That is absurd. He basically says:

"We can't study A unless B happens therefore studying A is pointless."

Really? So...then what happens when some brilliant theorist finds a way to make B a reality? Maybe that's impossible. I don't know. I certainly didn't learn anything about that from Malefant's post. All I learned was he took the time to tell us this topic was a waste of time. But, really, is there any reason Malenfant couldn't have written...

"Interesting notion, Frank. But sadly, other universes cannot be studied and are entirely conjectural, and therefore irrelevant unless some link can be proven between our universe and theirs to make them measurable or detectable. The current thinking on cosmology is that such a link will never be proven. Thus, as a scientific pursuit - you may be misleading your students."

Would that have been so hard? Who is really wasting time? Malefant - for going to great lengths to simply tell us how WE are wasting time. And me...for trying to protect users in good faith from being afraid to post something in good faith for fear of some kind of backlash.

Sigh!

Why is it so difficult for some folks to realize that MILLIONS of people think the universe IS INFINITE!!!!! They claim it to be so. They believe it. They spout the words. I have student after student who heard somewhere that the universe is infinite, and that is that.

What they DON'T REALIZE is what an infinite universe really means. Since I am not sure, I posted a thread here to ask for your opinions. For God's sake, if you don't want to discuss it, then MOVE ON! Read another post and do whatever you want to do. But realize this. Unless we explain to people what infinity really means, they will continue to believe in it! They will continue to be ignorant of the truth!

If you are so elitest that you would not sully your mental powers by helping me to explain what an infinite unvierse means, then perhaps this forum is not what I thought, but is full of a different kind of person ... one whom I find little interest in discourse with

So again ... if you don't like the topic, IGNORE IT!!!

Conversely, if you find the subject fascinating, then please help me. Am I on the right track with my reasoning?

Frank

fsgregs wrote:Conversely, if you find the subject fascinating, then please help me. Am I on the right track with my reasoning?

You're asking people if you're on the right track with your reasoning. I'm telling you that I don't think you are. So when I tell you that then you're telling me to go away. [offensive terms deleted ...s.]


Your starting assumption is baseless. You think it's better to teach people about what infinity really is and then you just magically assume that somehow that's going to persuade them that they're wrong? How the hell is that going to change their minds at all? They're just going to hear an educator telling them all about how huge infinity is, and then you're going to say that all of that was a waste of time because the universe isn't really infinite? What is this, bait-and-switch education?! That's ridiculous!

You want to tell people their beliefs are wrong? Then show them the evidence that they're wrong. Tell them what we DO know, show them the evidence that we DO have, and don't reinforce the belief in their minds that things are infinite when they're not. If they're too naive or dumb to know any better then you boggling them with how big infinity is is certainly not going to persuade them that they're mistaken.

It's like you think that two wrongs make a right here somehow, and that's no way to educate someone. But hey, if you want to carry on and do nothing to change their beliefs, you're on the right track.

A TWO-PARTER

First...off-topic:

Malenfant...are you reading the posts in this thread or just skimming? Because the answers to all your confusions lay within. The reason Frank is frustrated lays within - which clearly eludes you since you are seeing it as vacillation ("Make up your damn mind!"). Type less. Read more.

You may not agree with what you find...but I believe it will clear up some of that confusion.

NOW BACK ON TOPIC...

Frank,

Do people THINK the universe is infinite? Or do they wish it to be so, thus BELIEVE it?

However, are they so off-base? If, as I have recently been reminded, the universe is expanding - then after, infinite time has passed, it will have expanded infinitely. So, in one sense the universe could be considered infinite. However, from what I have learned - and I am waiting/researching confirmation - an infinitely large universe does not necessarily mean an infinitely populated universe. The matter in it may be finite. Thus your scenario has less validity were that not the case.

Personally, I think it's turtles all the way down. But, remember, I'm just a hack writer...so don't quote me on ANY of this....