# Thread: Is Space Infinite.

1. Is space infinite? - ie without end such that you could travel in a straight line forever away from the earth?

Is space infinite in the sense that you could travel in a straight line and end up back where you started?

Is space bounded such that if you hit the boundary you would cease to exist in this universe?

Is there some other possibility?

2.

3. I believe that space is growing faster than the speed of light. Therefore it doesn't appear to be growing since nothing shows it growing.

4. Well Bilco is a tough question.
First point by definition there is nothing outside the universe (because the word universe mean everything).
Second point, even if you could travel at whatever speed you want, you will never reach the limit of the universe, because the only thing you would achieve is to expand it (as you are a part of it).

5. PD Assume for a moment that the universe is merely the smallest sphere that can contain all the matter that exists. This sphere is in 'space' and according to current theory is expanding further into [existing] space. Now re-read my question and what answer would you choose?

Originally Posted by The P-manator
I believe that space is growing faster than the speed of light. Therefore it doesn't appear to be growing since nothing shows it growing.
What is it 'growing' into?

6. Originally Posted by billco
PD Assume for a moment that the universe is merely the smallest sphere that can contain all the matter that exists. This sphere is in 'space' and according to current theory is expanding further into [existing] space. Now re-read my question and what answer would you choose?
First of all, I will not choose in any case the point 3 : it remind me the dark ages, when people use to believe that they will end in a giant waterfall at the limit of earth (in the sea).

Second point. The sphere is mathematically the best ratio between the surface of the figure and it's volume. So in a gravitional point of vue, the sphere make sense. It also make sense, since everything was irradiated from the same central point.

Third point. So basically what we call universe is contained in an infinite space where there is really an absolute emptyness (no particles at all). So what happen if you go outside what we call universe. I will say answer one. I higly doubt, that there is special physical laws bouncing the limit of the universe. The bouncing model only make sense in a 2D model, like us terrestrians walking on the earth and never able to leave it, whatever we are trying to do. Now we have sent objects in space, so we have broken this 2 limit

7. The infinite space, confined[but expanding] universe is the only one I can conceive. Are we all in agreement?

8. If the universe is still expanding, isn't it infinite in the sense that you could travel in a straight line forever away from the earth? I certainly don't think that if one hits the boundary of the universe one would cease to exist, but I'm really having a hard time imagining what the boundary of the universe would "look like".

9. Originally Posted by daniel
If the universe is still expanding, isn't it infinite in the sense that you could travel in a straight line forever away from the earth? I certainly don't think that if one hits the boundary of the universe one would cease to exist, but I'm really having a hard time imagining what the boundary of the universe would "look like".
What we are saying is that space is infinite. The universe is just the bit with the galaxies in it. Think of it this way, you blow up a balloon[universe] in a larger area[space].

10. Originally Posted by billco
Originally Posted by daniel
If the universe is still expanding, isn't it infinite in the sense that you could travel in a straight line forever away from the earth? I certainly don't think that if one hits the boundary of the universe one would cease to exist, but I'm really having a hard time imagining what the boundary of the universe would "look like".
What we are saying is that space is infinite. The universe is just the bit with the galaxies in it. Think of it this way, you blow up a balloon[universe] in a larger area[space].
Gah. Of course. Didn't think of it that way. Nevermind my ramble, then Although now I wonder, are there other things in space than just the universe?

11. Bilco...

Anything is possible. When we say "The Universe" we mean our "observable universe" and it includes everything in it. Whats beyond that is anyones guess. Some scientists believe that our universe is one of many in an infinite void, and some believe that ours is the only one.

A good book is "Fabric of the Cosmos" by Brian Greene.

Bettina

12. Originally Posted by billco
Originally Posted by daniel
If the universe is still expanding, isn't it infinite in the sense that you could travel in a straight line forever away from the earth? I certainly don't think that if one hits the boundary of the universe one would cease to exist, but I'm really having a hard time imagining what the boundary of the universe would "look like".
What we are saying is that space is infinite. The universe is just the bit with the galaxies in it. Think of it this way, you blow up a balloon[universe] in a larger area[space].
Separating the concept of universe and space is a good solution for my poor grey cells.
infinite space, and limited but still expanding universe : good for me.

I truly expect, that nobody will pop up here, and explain us, that there is no space outside universe for whatever weirdos reason. If it was the case, I fear that I will have a nervous breakdown

I love your proposition because I can mentally represant that

13. All matter and energy, including the earth, the galaxies, and the contents of intergalactic space, regarded as a whole.

That is the modern definition of Universe.

Much as I said the smallest 3-d.

That is why I said 'space' in my original post. I suspect that when you went to school they were the same, now they are distinctly seperate.

14. Originally Posted by billco
All matter and energy, including the earth, the galaxies, and the contents of intergalactic space, regarded as a whole.

That is the modern definition of Universe.

Much as I said the smallest 3-d.

That is why I said 'space' in my original post. I suspect that when you went to school they were the same, now they are distinctly seperate.
Thanks for your update. I fear that when I used to go to school three decades ago, I did not recieved much teaching about astronomy. The few I know, I learned it by myself.
My personal own field is medecine, but astronomy is the only science that made me dream. Medecine is often nightmarish

15. Originally Posted by billco
What is it 'growing' into?
Into the already existing 'space' you were talking about.

16. YOu said space is growing- I said "what into" You sa.. oh never mind...

17. I meant the universe is growig into the space.

18. The confusion has subsided.

I am not sure that the universe is expandig at that rate though.

What makes you believe it is?

19. Originally Posted by Powerdoc
.....but astronomy is the only science that made me dream.
That was a nice quote and I feel exactly the same way.....

Here, look at this link from Wiki..... I have lots of other links if your interested. Braneworlds too....

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

Bettina

20. Nice one Bet (if I may be so formal)

That's completely screwed up this aged mind! - When I was at school in the 1940/50's I was taught the steady state theory, so space and the universe was the same thing. With the big bang that seems to have changed, If it is all expanding then it has to be a definite size, that size is what I am calling the universe. My poor human mind can only comprehend it is expanding into something, that I call space which I believe is infinite. The big bang theory has problems, it's ok to say it's expanding into the future so it was contracting in the past but, I'm not sure that means it was ever a singularity. If it was never a singularity then space and time would have existed before the expansion began.
For a while I remember there was a theory that said eventually the gravitational forces would pull all the matter back together and it would all start over again. Today they say that cannot happen but whatever they replace it with has problems. If I make this post any longer you'll stop reading so I'll cut it here.

21. Originally Posted by billco
Nice one Bet (if I may be so formal)

That's completely screwed up this aged mind! - When I was at school in the 1940/50's I was taught the steady state theory, so space and the universe was the same thing. With the big bang that seems to have changed, If it is all expanding then it has to be a definite size, that size is what I am calling the universe. My poor human mind can only comprehend it is expanding into something, that I call space which I believe is infinite. The big bang theory has problems, it's ok to say it's expanding into the future so it was contracting in the past but, I'm not sure that means it was ever a singularity. If it was never a singularity then space and time would have existed before the expansion began.
For a while I remember there was a theory that said eventually the gravitational forces would pull all the matter back together and it would all start over again. Today they say that cannot happen but whatever they replace it with has problems. If I make this post any longer you'll stop reading so I'll cut it here.
Nah.... I always read to the end. Here is another link to look at..

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

Bee

22. Originally Posted by Bettina
Originally Posted by billco
Nice one Bet (if I may be so formal)

That's completely screwed up this aged mind! - When I was at school in the 1940/50's I was taught the steady state theory, so space and the universe was the same thing. With the big bang that seems to have changed, If it is all expanding then it has to be a definite size, that size is what I am calling the universe. My poor human mind can only comprehend it is expanding into something, that I call space which I believe is infinite. The big bang theory has problems, it's ok to say it's expanding into the future so it was contracting in the past but, I'm not sure that means it was ever a singularity. If it was never a singularity then space and time would have existed before the expansion began.
For a while I remember there was a theory that said eventually the gravitational forces would pull all the matter back together and it would all start over again. Today they say that cannot happen but whatever they replace it with has problems. If I make this post any longer you'll stop reading so I'll cut it here.
Nah.... I always read to the end. Here is another link to look at..

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

Bee
I will have to check this carrefully, has Brane and orbifold and alike are not a digest meal.

23. The universe is Finite. No matter what

24. Originally Posted by Zelos
The universe is Finite. No matter what
I agree, it is bounded. It's just expanding into what I call 'free space' which is infinite.

Originally Posted by Bettina
Nah.... I always read to the end. Here is another link to look at..
Bee
If you have that that much time available - go out and explore the world, it's a beautiful place. 8)

25. And I believe I answered the question in the undertext. Even though I know it might be the wrong answer, but it sounds logic. Perhaps the simplest explanation is that the universe is alot bigger then it actually is.

26. Originally Posted by LeavingQuietly
Perhaps the simplest explanation is that the universe is alot bigger then it actually is.
Huh

How can it be bigger than what it is?

It is the size it is, no more, no less.

27. Alot bigger than it seems to be i meant. I am going to leave quietly now.

28. Originally Posted by billco
Originally Posted by Zelos
The universe is Finite. No matter what
I agree, it is bounded. It's just expanding into what I call 'free space' which is infinite.
How can it (the universe) be finite if it's still expanding (into space)? :?

29. Originally Posted by daniel
Originally Posted by billco
Originally Posted by Zelos
The universe is Finite. No matter what
I agree, it is bounded. It's just expanding into what I call 'free space' which is infinite.
How can it (the universe) be finite if it's still expanding (into space)? :?
A child or a tree is finite but still growing. I don't see where is the problem

30. Originally Posted by Powerdoc
A child or a tree is finite but still growing. I don't see where is the problem
It's funny how blatantly simple comparisons can make things obvious to me and thus making me feel slightly embarassed :P

31. Originally Posted by daniel
Originally Posted by Powerdoc
A child or a tree is finite but still growing. I don't see where is the problem
It's funny how blatantly simple comparisons can make things obvious to me and thus making me feel slightly embarassed :P
You don't have to be embarassed, sometimes the complexity of the universe disturb us.

32. Originally Posted by billco
If you have that that much time available - go out and explore the world, it's a beautiful place. 8)
My life is very busy. There's just me and dad and we live together so I do the housework, yard work, study, meet my friends at the mall, surf the forums, chat on the phone, do church stuff, sing at the park, do park stuff, and on and on and on.....

Bee

33. Stay young kid, life gets decidedly more difficult later, whenever you are outside have a quick look around - nature's beauty is everywhere.

34. Originally Posted by billco
Stay young kid, life gets decidedly more difficult later, whenever you are outside have a quick look around - nature's beauty is everywhere.
I agree billco, I hate to quote an '80s teen movie, but as Ferris Bueller so profoundly said "Life moves pretty fast. If you don't stop and look around once in awhile, you could miss it."

35. Originally Posted by MacGyver1968
Originally Posted by billco
Stay young kid, life gets decidedly more difficult later, whenever you are outside have a quick look around - nature's beauty is everywhere.
I agree billco, I hate to quote an '80s teen movie, but as Ferris Bueller so profoundly said "Life moves pretty fast. If you don't stop and look around once in awhile, you could miss it."
I also agree. I try to take a moment each day to appreciate 3 things in particular;

I'm alive,
I'm in good health,
and I'm free,

in that order.

cheers

36. I suppose at 70, 2 out of three 'ain't' bad!.

37. Originally Posted by billco
I suppose at 70, 2 out of three 'ain't' bad!.
My dad is 66 to my 18. He's an executive and still works, jogs, and rides a bycycle.

And William... you must also be loved. There are four.

Bee

38. Originally Posted by Bettina
And William... you must also be loved. There are four.
It is harder for me to take that one for granted. So it's the only one I don't have to remind myself of.

39. I still cycle gave up the car completely in 04. As I said I've got two - I'm [reasonably] healthy and I'm [reasonably free]. My philosophy is simply that everyday I wake up is a good day.

40. Originally Posted by billco
I still cycle gave up the car completely in 04. As I said I've got two - I'm [reasonably] healthy and I'm [reasonably free]. My philosophy is simply that everyday I wake up is a good day.
by that logic you can never have a bad day.

what a nice idea that is.

41. Originally Posted by Powerdoc
I truly expect, that nobody will pop up here, and explain us, that there is no space outside universe for whatever weirdos reason. If it was the case, I fear that I will have a nervous breakdown
Assuming the conventional view of the universe, - if nothing exists outside of it to give it dimension or time, then in reality, the concept of outside the universe doesn't exist, it is less than nothing.

Whats more North than the North Pole on the surface of a sphere? Its an invalid question.

Imagine this, i think you're possibly viewing the universe as a sphere expanding into a blackness totally devoid of anything - But this Blackness devoid of anything exists as a propery of the conception of 'nothing' in your imagination. Therefore you have made it into something.

Even the Blackness devoid of anything Doesn't Exist.

please break down quietly

42. MarkUK

The doc and I have decided there IS something outside the universe, it is what is being consumed by the very vitals of the[expanding] universe. I propose to call it phlagiston which has been discredited before so we'll give this old flame a second chance. :wink:

43. Billco and Powerdoc (if he's still functioning )

is it possible for the human mind to truly conceive absolutely nothing - in the context of what were talking about.???

I'd argue, it is not possible. The absolute nothingness we can imagine still has properties that give it an existance.

44. It's well possible to conceive nothingness, just concentrate on what your knee can 'see' at the moment... That is not meant to be silly.

Or what were your personal experiences before you became a conscious individual?

45. yes but in your mind, you're still creating a mental image of the 'nothing' your knee is seeing thus giving it an existance.

46. Originally Posted by marcUK
yes but in your mind, you're still creating a mental image of the 'nothing' your knee is seeing thus giving it an existance.
Welcome brother! what clinched it? and watch out for the others...

P.S Bold, it simply has to bold

47. Originally Posted by marcUK
Billco and Powerdoc (if he's still functioning )

is it possible for the human mind to truly conceive absolutely nothing - in the context of what were talking about.???

I'd argue, it is not possible. The absolute nothingness we can imagine still has properties that give it an existance.
absolutely : recieve a good base-ball stroke on your head, and you will concieve nothing. I experienced this at the age of 7. Our brain is working 24/24.
Now if the question is to concieve nothing has an abstraction, it's a different question. For me nothing is a dark image, without any smell, sound, heat. I must admit it's a difficult exercice, but it worth trying it.

For me space is a mathematical concept, so I have no problem at all to concieve it infinite (math is an abstraction isn't it ? ) while universe is a real thing rule by the laws of physics. Here the infinite does not exist. Some things tend toward the infinite, but there is no infinite.

Mark : a note about your curvature earth analogy. It only work in 2D mode. When humans suceed to launch satelites, they suceeded to escape from earth. Now if you consider that you wear with you a little UK flag, wherever you will go, it will become private property of the queen. So now you have Mark UK the great expander.

48. If the universe is infinite this implies it has been around forever, because to expand to an infinite size would take an infinite amount of time. If it has been around forever this would imply that before every action we make there would be an infinite amount of time, and our concept of time would breakdown. Also according to Hawking in an infinite universe there would be and infinite possibility of a galaxy forming at any particular point, therefore there would be galaxies everywhere. This contradicts our current lifestyle. Therefore no infinite universe. Also infinite space. I like to think of this by the picure of us living in the expanded singularity of a black hole (our own finite baby universe). This is equivalent to the balloon analogy in that the black hole must exist in another universe. In this case this universe obeys the previous principle that contradicts the infinite universe, therefore this is finite as well. Therefore in any baby universe by black hole analogy both universes must be finite and therefore space in total must be finite. If you choose not to think of it as a black hole and look at it as though we are like a massive "galaxy" bounded by a cosmic balloon, then if this space is to be infinite, any possibility of stars forming in any one place is multiplied by an infinite time and therefore this space outside ours would also be4 jampacked with stars. Therefore the infinite space theory is on pretty precarious foundations, in my opinion wrong. We do not need to be expanding into anything that would be comprehensible as the space we know of, it could be some cosmic space that exists on a higher level than ours, or it could just be nothing.

49. I'm not sure I can take Mr Hawking seriously, his 'Hawking radiation' is to my mind simply not on. For him to propose a theory which can never be proven or disproven - discredits much of his other work in my opinion.
I see no reason why time and space cannot have always existed. I believe another more credible theory may yet be found. I am not a proponant of steady state theory either. Both theories have flaws as both sides admit. I do not know the answers, and I do not have an alternate theory. If I were forced to choose I would ask if you could throw in a third option, Divine creation, unless of course somebody comes up with something more plausible[to me].

50. the whole universe expanding for me is a real head f*ck, when you ask whats it expanding into and you get the answer nothing, that really screws with my mind

Its like the nothing that its expanding into, is that infinite?, can you have an infinite nothing?........

BOOM, thats it heads exploded

51. Well if we want to get really philosophical infinity*0 is undefined, so technically an infinite amount of nothing is not plausable. If you don't like the idea of nothing, then look at a new theory contesting the theory of a unique big bang. Hawking backs this theory up. The theory is that there are many universes that move about in a space of a higher dimension than the space inside them (imagine pieces of paper with galaxies drawn on them (the paper is 2d) floating around in the air (this space is 3d)). I would give you this in the four dimensional way but obviously we can't picture a four dimensional space. So we have three dimensional (forgetting the time dimension, and any dimensions coming from M theory) unvierses moving around in a space with more than three dimensions. As these universes cool they are attracted to each other, and when they collide a big bang occurs in the colliders, this impies that the universes have existed forever however they are not infinite. It also implys that this big bang that appears to have left much radiation around did not initiate time and the universe we live in, but simply caused it to perhaps expand a bit, explaining the viewed red shifts, (the space it has expanded into is not nothing, but a four dimensional superspace). This removes the problems with the inflation of the universe faster than the speed of light because if the universe has existed forever it could as long as it wants to expand to its current size and therefore would not have to travel at light speed expansion.

52. Firstly infinty is NOT a number, it is a concept. you simply CANNOT place infinity into a sum as you have done. In mathematics we say 'approaches' infinity which simply means it's a bloody big, yet still countable, quantity. It is a concept only.

Secondly I am quite sure that if Mr Hawking said that the world is flat, but just appears curved, through some effect of space time, he would be believed without question by a great majority. I for one merely see him as a cosmic tailor of clothes for the emporer.

53. Billco

whats the deal with (dismissing) Hawkin Radiation.

Its a very simple concept. Perhaps you dismiss the entire notion of virtual particles?

54. Originally Posted by Corner Neutralino
Well if we want to get really philosophical infinity*0 is undefined, so technically an infinite amount of nothing is not plausable. If you don't like the idea of nothing, then look at a new theory contesting the theory of a unique big bang. Hawking backs this theory up. The theory is that there are many universes that move about in a space of a higher dimension than the space inside them (imagine pieces of paper with galaxies drawn on them (the paper is 2d) floating around in the air (this space is 3d)). I would give you this in the four dimensional way but obviously we can't picture a four dimensional space. So we have three dimensional (forgetting the time dimension, and any dimensions coming from M theory) unvierses moving around in a space with more than three dimensions. As these universes cool they are attracted to each other, and when they collide a big bang occurs in the colliders, this impies that the universes have existed forever however they are not infinite. It also implys that this big bang that appears to have left much radiation around did not initiate time and the universe we live in, but simply caused it to perhaps expand a bit, explaining the viewed red shifts, (the space it has expanded into is not nothing, but a four dimensional superspace). This removes the problems with the inflation of the universe faster than the speed of light because if the universe has existed forever it could as long as it wants to expand to its current size and therefore would not have to travel at light speed expansion.

its not i dont like the idea of nothing, just a real head f*ck at the same time yeah i remember reading that about dimensions running along side one another and remember something about them being a tiny tiny distance apart

55. Originally Posted by marcUK
Billco

whats the deal with (dismissing) Hawkin Radiation.

Its a very simple concept. Perhaps you dismiss the entire notion of virtual particles?
As I understand it in order to explain that black holes decay we have hawking radiation that say's 'pair's' appear, close to the event horizon, but before they can re-combine, one part gets sucked into the black hole where it cancels wth an existing particle. THis will take something like 10^70 seconds to occur. Great the universe is about 5x10^seconds old so no-one will ever know. These particles appear from nowhere.

I just reckon that there are other possible avenue's open to explain black holes 'fading' - or maybe they won't fade at all. - And remember these 'black holes' are themselves still only 'theoretical' - yes I am afraid they are!.

If I were visited by some adcanced ET who said "Bill, I can divulge to you all the secrets of the universe" I think I'd say "Thanks but no thanks"

Knowing the secrets of conjuring rather spoils one's enjoyment, don't you think?

56. If you don't think infinity is a number, or has number like characteristics then your wrong. For a start to say infinity is meaningless in mathematics because there are in fact different orders of infinity known as Cantor's infinities. I must state that when I say infinity I mean the countable infinity, ie. the number of integers, or the number of fractions, or the number of rational numbers. Other infinities include the number of points on a line (larger than the number of integers) and the number of conceivable curves (larger than both). The first of these infinities is countable as you could steadily prgoress through the integers knowing exactly how to count them. However if you want to count irrational and rational decimals this is impossible because you cannot simply say that the next decimal after x is y. however with integers you can do such. You can quite easily insert infinity into a sum.

1/infinity=0

In this case if you took infinity not be an unreachable number, but a finite number, then 1/infinity would not equal 0, but would tend to zero.

So you see you can insert infinity into equations without always getting undefined results. Most of the time however you are right in saying that you say that a number tends to infinity.

Another way of looking at it is by looking at the symmetry between 0 and infinity. By saying that you cannot insert the abstract infinity into an equation you are effectively saying you cannot do this with zero. The insertion of infinity into equations is just like the insertion of zero, sometimes you can do it. For example

y=5/x

strictly you cannot make x zero.

y=5x

Here x=0 is allowed

y=x/x

here x=infinity is not allowed because infinity/infinity is undefined and does obey the rule that a number over itself is one.

57. If you don't think infinity is a number, or has number like characteristics then your wrong. For a start to say infinity is meaningless in mathematics because there are in fact different orders of infinity known as Cantor's infinities. I must state that when I say infinity I mean the countable infinity, ie. the number of integers, or the number of fractions, or the number of rational numbers. Other infinities include the number of points on a line (larger than the number of integers) and the number of conceivable curves (larger than both). The first of these infinities is countable as you could steadily prgoress through the integers knowing exactly how to count them. However if you want to count irrational and rational decimals this is impossible because you cannot simply say that the next decimal after x is y. however with integers you can do such. You can quite easily insert infinity into a sum.

1/infinity=0

In this case if you took infinity not be an unreachable number, but a finite number, then 1/infinity would not equal 0, but would tend to zero.

And by the way I was simply using the flat world as an example of dimension increasing.

So you see you can insert infinity into equations without always getting undefined results. Most of the time however you are right in saying that you say that a number tends to infinity.

Another way of looking at it is by looking at the symmetry between 0 and infinity. By saying that you cannot insert the abstract infinity into an equation you are effectively saying you cannot do this with zero. The insertion of infinity into equations is just like the insertion of zero, sometimes you can do it. For example

y=5/x

strictly you cannot make x zero.

y=5x

Here x=0 is allowed

y=x/x

here x=infinity is not allowed because infinity/infinity is undefined and does obey the rule that a number over itself is one.

58. well, the problem is that the math bears it out - and i know certain people here won't believe anything unless the math bears it out - yet here we're not believing a theory because its only a mathematical proof at the moment. Can you have it both ways?

So id like to hear your other alternatives for a black hole dissipating...

I think its a bit of a stretch to say that black holes are theoretical only, - weve observed the structures we believe are black holes - maybe its not quite a definite proof at the moment. but they're more than a mathematical curiosity.

59. There is almost definite evidence for black holes. How are quasi-stellar objects held together in their spiraling orbit (dark matter cannot explain this).

How are appearingly single stars held in and orbit around an invisible object?

60. Visualizing infinity,nothingness, hypercubes is difficult.

There is another thing which I think is hard to visualize.

Einsteins spacetime geometry. It is traditionally viewed as a flat sheet (of rubber) in which items of mass make depressions in this flatness to allow smaller masses to roll around the centre if they have the right velocity for orbit.

BUT. Try to imagine the spacetime in 3d. First off, imagine that there are 2 sheets of rubber in opposition to eachother. Whereas traditionally the warp of spacetime is downwards when visualised in 2d, with 2 sheets in opposition, the second grid of spacetime would warp upwards.

Now, its obvious that the 'point' of maximum distortion cannot be in 2 seperate places, so infact they have to meet in the same place. So obviously you have to flip the sheets and have the points meet in the centre (of a star)

Now this is only 2 sheets, imagine a sheet for every degree of a sphere. Infinite sheets.

Soon you have to completely lose the idea of distorted sheets altogether and imagine something similar to a weather pressure chart, where areas of equal spacetime distortion create spheres around the central mass, increasing in frequency and distortion until you hit the very centre of the central mass. This mentally shows that time runs slower the closer you get to the centre of a star.

Then you have to wonder if wormholes etc are really possible, or just seem that way when you project them in 2d. Can a 3d wormhole really be created in your mind? How can you connect 3d wormholes the way it looks so easy when you try it in 2d?

And 3d is probably not the end of the story. When you've tried that - imagine them in 4d.

61. I choose the dictionary definition of infinity - forever - without end.
If you believe infinity is a number write it down and I will add 1 to it.

I do not say that black holes do NOT exist, I say they are a theory, that means they may or may not exist. I accept that they explain certain phenomina that as yet, has no credible alternative theory.

I believe that where only one[initial] theory exists it is bloody dangerous to accept it. There are countless examples of this throughout history.

As to black holes receding, Electromagnetic waves increase in energy as they increase in frequency. There may be an upper limit, but as yet it has not been reached in terms of our finding it through experiment. I see no reason why em waves of sufficient energy may not escape a black hole.
We know that quasars lose energy by this very means, perhaps black holes can generate higher energy level EM waves or even some as yet undiscovered particle. This is speculation and not a theory.

Dark Matter, black holes, worm holes, anti-matter, It just seems a little curious to me that all these and many other things exist, or should I say are proposed to exist, in order to back up theories that do not stand up without them. There is a danger that a house of cards is being built, however remote. I am simply skeptical. They may well all exist, Mr Hawking may well be correct, but there again, they could all be wrong.

62. I fully agree with the rubber sheet analogy you just mentioned. It is difficult to think of what a 2d representation of a black hole on a rubber sheet for example would look like in reality. The answer is, nothing like the sketch. You would never be able to see the black hole from side on because as we all no gravity has no chosen direction. The rubber sheet analogy is simply a way of showing what happens in two dimensions, because we cannot draw three dimensions. You try and draw a sphere, you draw a circle. It is pointless to think of infinite rubber sheets because that model is not designed for that. A three dimensional model is required. Just think of it as a way of expressing motion in one plane, like our planets orbiting the sun, however with black holes remember that the rubber sheet is depicting the black hole as though you could move around it in another dimension to see it from the side, there is nothing wrong with this method, because that is what the hole is like, however what actually happens is the mouth follows the observer round, so all these sci fi things where a spaceship is seen moving along the rim of a black hole are unintelligable, the rim is as real as the rubber sheets.

You can add one to infinity by the way that equation is not undefined, but it just gives infinity again. This equation also suggests that infinity - infinity is undefined because if it was equal to 0 this would imply 1=0 whichc is proposterous.

63. is it possible to subtract 1 from infinity like you can add 1 to it?

I would have thought that doesn't still give you infinity.

64. No it gives you infinity, because what else would it give you, fair enough you could say it is undefined, but the fact remains that even though you have subtracted 1 from it it would still take you forever to count to your new number

65. Originally Posted by marcUK
is it possible to subtract 1 from infinity like you can add 1 to it?

I would have thought that doesn't still give you infinity.
Nope, what I said was, if he could write it down I could add one to it.

Infinity is a concept to help with certain mathematical problems, by it's very definition it is not a quantity. The only acceptable quantifiable use of the word infinite is a sentence with words like 'president' and 'stupidity' also in it :wink:

66. LOL. I was just saying that you can insert it into equations and get defined answers.

67. sure, i fully understand the concept of infinity as a concept that goes on forever. I guess you cant subtract anything from infinity, except infinty, which would give you 0.

Can you do trick mathmatical things like - infinty subtract 1/2 infinity = 1/2 infinity ??

68. here's one for you mark,

IF space is infinite, how come I take up some of it? :wink:

69. infinty subtract 1/2 infinity = 1/2 infinity ??
it equals infinite since 1/2 infinite is infinite
what is infinite/infinite ? i can get 2 answers

70. 1NF1N1TY Minus 111 = NFNTY !!

71. If you want to do arithmetic with infinities you need to learn about ordinal and cardinal numbers - which is a really weird kettle of fish: and leads you to the axiom of choice, transfinite induction etc.

Zelos - define what you mean by infinity divided by infinity and how you only get two answers?

72. Originally Posted by Zelos
infinty subtract 1/2 infinity = 1/2 infinity ??
it equals infinite since 1/2 infinite is infinite
what is infinite/infinite ? i can get 2 answers
Half infinity do not exist.
infinite is a mathematical concept, and not a number. infinite is an absolute. There is nothing greater than infinite. Half the infinite mean nothing, infinite multiplied by zero, do not mean anything either.

73. [quote="Powerdoc"
Half infinity do not exist.
infinite is a mathematical concept, and not a number. infinite is an absolute. There is nothing greater than infinite. Half the infinite mean nothing, infinite multiplied by zero, do not mean anything either.[/quote]

Tell that to the continuum, which is a larger infinity the the size of the integers (lets call it omega) or any other transfinite ordinal or cardinal number. Infinity is quite a big topic and more finesse is required to handle it then you are allowing here.

74. [quote=river_rat]
Originally Posted by "Powerdoc"
Half infinity do not exist.
infinite is a mathematical concept, and not a number. infinite is an absolute. There is nothing greater than infinite. Half the infinite mean nothing, infinite multiplied by zero, do not mean anything either.[/quote

Tell that to the continuum, which is a larger infinity the the size of the integers (lets call it omega) or any other transfinite ordinal or cardinal number. Infinity is quite a big topic and more finesse is required to handle it then you are allowing here.
There is mathematically differents kinds of infinite, but it's still mathematic. In physic it mean nothing : even black hole do not have an infinite weight.

75. Originally Posted by Powerdoc
There is mathematically differents kinds of infinite, but it's still mathematic. In physic it mean nothing : even black hole do not have an infinite weight.
How do you seperate the two? And what type of infinity does physics use then?

76. Originally Posted by river_rat
Originally Posted by Powerdoc
There is mathematically differents kinds of infinite, but it's still mathematic. In physic it mean nothing : even black hole do not have an infinite weight.
How do you seperate the two? And what type of infinity does physics use then?
I know that physic use math, but I do not see infinite as a number in physic. I see function tending toward infinite, but not number equal to infinite.

Is the size of the universe infinite ?
is the number of particles infinite ?
is the speed infinite (wasn't it limited to the speed of the light) ?

77. Originally Posted by billco
The confusion has subsided.

I am not sure that the universe is expandig at that rate though.

What makes you believe it is?
The fact that it is not actually visible that the universe is expanding. If it was expanding at less than the speed of light, some light may get to the edge of the univers, and there we would be able to justwatch it expand. It is not so, unfortunately. It would be an awesome sight.

78. None of that answers my question - what is the size of the function spaces in QFT for example. They are huge, a lot bigger then a normal "infinite" function space.

79. In terms of the speed of light, has anybody actually calculated how fast the universe is expanding?

Is it the presence of matter that decides the size, or light and gravity travelling out?

80. But can the light travel out?

81. dunno that was what I was asking, I think it has to be expanding at least as fast as light, heard that you travel in a straight line you come back to where you started, which to me means all the light from the big bang would have met up back where it started - if that makes sense to you.

82. Yeah, I get it. But you are just repeating me. I said I thought that the universe is expanding faster than the speed of light.

83. Originally Posted by billco
dunno that was what I was asking, I think it has to be expanding at least as fast as light, heard that you travel in a straight line you come back to where you started, which to me means all the light from the big bang would have met up back where it started - if that makes sense to you.
The "universe" can travel faster than the speed of light so long as it carries no information with it.... like light. Many believe this to be true, so yes, its going faster... so fast, that the expanding light will never overtake it.

If you remember the theory of inflation, the "Universe" grew by a factor of 10 to the +60th power in less than 10 to the -30 seconds which makes it much faster than the speed of light. I'll see if I can find a good link.

Bettina

84. The shape of the universe and its extent depends on the value of "hubble's constant"(rate of expansion of universe) and "omega"(total mass of universe).So assuming it to be a sphere is nothing.

85. If anybody ever went to look at how big the universe is, nobody ever came back!

86. Originally Posted by river_rat
None of that answers my question - what is the size of the function spaces in QFT for example. They are huge, a lot bigger then a normal "infinite" function space.
I do see more infinite as a function, than infinite as a real number.

For example if we look at what said Zelos infinite substracted to half an infinite, it's much better to do with function.

I will say that it's ax - ax/2 = ax/2.
So the answer is that the function still reach the infinite, but a lower speed.
According to the same logic x exp x reach the infinite at much higher speed than ax.
And here come the paradox : you can't reach infinite by definition, because even in a exponential equation x have been to be infinite in order to reach infinite. Even 10 e bazillion is not infinite.
So you tend to reach infinite at a much higher speed, but you never reach it.

87. Yes but what does infinity mean anyways. What is meant when we say infinity. You say its a function, others say its a number. Should we trust the IAU to do another description.

88. It is neither a number or a function. It is a concept.

89. Another opinion. Someone please decide someday, or I shall move to my basement and meditate.

90. Originally Posted by The P-manator
Another opinion. Someone please decide someday, or I shall move to my basement and meditate.
http://scidiv.bcc.ctc.edu/Math/infinity.html

OK?

91. Got it. I agree that it is a concept, but some people seem not to.

92. Originally Posted by The P-manator
Got it. I agree that it is a concept, but some people seem not to.
And as we all know as soon as you move infinity from a concept to a number or function, you get 1=2.

93. You can think of infinity as a number if you like, you just have to accept that certain operations are undefined.

for example

2infinity=infinity

2=infinity/infinity

here in order to avoid absurdity of 1=2 we say that infinity/infinity is undefined, you cannot get two values you can get an infinite number of values for it:-

My proof that infinity/infinity is undefined

assume infinity/infinity is defined, lets define as what some would expect it to be, 1

infinity/infinity = 1

but now if i multiply the equation by 10

10infinity/infinity = 10

since 10infinity is still infinity this simplifies to

infinity/infinity=10

I could therefore define infinity/infinity as any value i please, therefore our initial assumption is false and infinity/infinity is undefined.

Infinity is whats called a cardinal number

cardinal numbers are numbers representing the size of a set

for example a set of ten dogs, the cardinal number is ten

a set of infinite dogs the cardinal number is infinity.

other undefined infinity equations

0*infinity

1^infinity

94. Originally Posted by billco
Originally Posted by The P-manator
Got it. I agree that it is a concept, but some people seem not to.
And as we all know as soon as you move infinity from a concept to a number or function, you get 1=2.
You can treat infinty as a number bilco - the normal way is to use the extended real line (and in complex variables the riemann sphere). As C_N posted though, you lose some operations on the newly introduced quanitites but it does allow you to treat them as "numbers" in most cases. To be technical you work with the compactifications of the spaces, instead of the spaces themselves (but im sure that flew over everyones head )

If you really want to handle infinite numbers though, the ordinals are where you should be looking - omega being the first transfinite number on the list.

95. Originally Posted by river_rat
Originally Posted by billco
Originally Posted by The P-manator
Got it. I agree that it is a concept, but some people seem not to.
And as we all know as soon as you move infinity from a concept to a number or function, you get 1=2.
You can treat infinty as a number bilco - the normal way is to use the extended real line (and in complex variables the riemann sphere). As C_N posted though, you lose some operations on the newly introduced quanitites but it does allow you to treat them as "numbers" in most cases. To be technical you work with the compactifications of the spaces, instead of the spaces themselves (but im sure that flew over everyones head )

If you really want to handle infinite numbers though, the ordinals are where you should be looking - omega being the first transfinite number on the list.
I do not place a value on infinity. However....

If I can choose a number to be infinity, I'll choose 200, no matter how much I walk through life I'm never gonna get there! 8)

96. Is space infinite?....oh, yes...sure!
do you have some doubt?

97. Easy problem - if space is infinite, why is the sky dark?

98. ...in the open space there isn't any atmosphere who can reflect light,and so create the classic blue-sky effect ...and then,there is to much distance between the stars,the speed of light is not infinite

99. Originally Posted by river_rat
Easy problem - if space is infinite, why is the sky dark?
Although I am open minded about the extent of space, there is a considerable amount of dust, rocks, dead stars and planets out there,if they outnumber live stars (which presumably they would do if the universe was older than thought) this might account for it remember we cannot see the heart of andromeda because of interstellar gas and dust....

100. Although I am open minded about the extent of space, there is a considerable amount of dust, rocks, dead stars and planets out there,if they outnumber live stars (which presumably they would do if the universe was older than thought) this might account for it remember we cannot see the heart of andromeda because of interstellar gas and dust....
Dust does not help, it merely heats up and begins to shine as a black body - it merely delays the inevitable infinitely bright sky by a few years.

101. I see some sense in that. It's not something I've ever given a great deal of thought to.

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