Does a finite universe make sense to you?

[MiltMeyers]

I thought that everyone was having fun with this so let me put in my 2 cents. The universe is finite and exspanding. It has no outside and the only thing like a center is the point of the big bang. All things are still in the universe and it's as if it's a trash bag and just gets bigger. Okay we look at the closes galaxy 2million light years away. Well the universe was smaller when the light left it. It is as if the smaller universe now fills a bigger universe. Okay now go back to the cmb and it is from a universe way smaller than now and it is in every direction we look. If we could see the center it would be in each and every direction we look. Now ask yourself which direction do I go to get to the edge of the universe and the answer is there is no outside. Now think of the balloon if light left this galaxy 2 million light years ago the balloon has exspanded and the beam of light traveled inside the surface as it made it's way here. It is a 3 d model of a 4d universe. The light has curved as it traveled thru space. If we could go instantly back in any direction we would wind up at the singularity and back to were we started. So now we can't go back in time to before the beginning as we would just start coming forward in time. So there is no time before the beginning of the exspantion of space time. So Now there is no outside there is nothing before the big bang and there is no center. So yes the universe is finite and getting bigger by the second. Now picture this as you look back in space time it is all going back to a point were it began and no matter which direction you look light would close to this 4d bottle I call it. See now you can see in 4d.

milt

 

[malawi_glenn]

#has no outside and the only thing like a center is the point of the big bang#

What is the 'point of big bang'?

 

[MiltMeyers]

Oh the center of the universe is right between your eyes as you look out you see the universe smaller so the biggest the universe will be is right between your eyes. That is true of all of us and any aliens that are looking out into space. That is why were all our eyes meet is the center of the universe if you can call it that. If this is hard to see I would be willing to take time and go thru it step by step. Yes there is the problem of now also but I think we all agree that there isn't a now all over the universe,right?

 

[MiltMeyers]

Malawi Glen what I ment was as we go back in time and space the universe gets smaller until it is a point and that is were the big bang started. It should still be there and we are closing on it and experiments with lower frequencys will or should take us further back and closer to the singularity that was our start of time and space.

 

[malawi_glenn]

MiltMeyers, how many times must we say, on this forum, that Big Bang did not occur within space?

We can't 'see' (optical seeing) 'further' than CMB, since space was opaque to radiation earlier. And CMB is everywhere, in all directions.

 

[MiltMeyers]

Malawi Glenn----No it didn't occur in space time as it is space time. There are exsperiments going that will look further back in time using TV frequencys. The frequency of the the initial impulse is zero and we see it everywere. As we go back in time the universe drops in frequency to the singulatity of zero. So there is hope we will find out the steps leading up to the formation of galaxys.

 

[MiltMeyers]

Malawi Glen since I'm awake I'll add that since the CMB was smaller and is in every direction it is a big clue space time is curved and there is no direction you can go to get outside or to an edge it just isn't there. Go beyond the CMB and you will reach a barrier were nothing but space and time exist and that is were the singularity existed. The universe is very small at that point---it's all here in the universe everything is here nothing is lost. Yes I know don't fall in a black hole.

 

[NYSportsguy]

I think I may have an answer now to this "edge" "no edge" concept of the universe.
Somebody up top compared it to a bowling ball and we are inside that bowling ball somewhere trying to move outwards from it or towards the center of it. As this bowling ball expands all around (moving at speed of light) we as humans, have no way of ever even traveling fast enough to reach the top surface of this ball in any direction because it is continuously expanding so far ahead of us at such a fast (rate) that it will literally take us forever to get to the outer part of this ever expanding sphere.

If the "bowling ball" were to stop expanding and we traveled at the speed of light (somewhere from the inside area of this ball) towards the outer surface, eventually we would reach this outer surface but not see any boundary, however just loop back continously around the ball (possibly without even knowing we were going this). I am willing to bet if we were to measure the space-time curvature somewhere at this junction we would see space shaped as "inwardly curved" instead of as "flat" the way we see it from within 8 billion light years all around us today.

Also keep in mind, as something travels the speed of light time seems to stand still. Six trillions years could go by on Earth and you would only lose one second of your life traveling at c. In this sense, it would take an infinite amount of time to travel something already 12-15 billion light years ahead of you distance wise.

 

[NYSportsguy]

I compare the Big Bang event to someone chewing bubblegum and then blowing a big bubble that expands forever. The "Bang part" itself happened at the person's lips and as he blew the bubble this became our ever expanding "3-D space".

 

[yuiop]

If the "bowling ball" were to stop expanding and we traveled at the speed of light (somewhere from the inside area of this ball) towards the outer surface, eventually we would reach this outer surface but not see any boundary, however just loop back continously around the ball (possibly without even knowing we were going this). I am willing to bet if we were to measure the space-time curvature somewhere at this junction we would see space shaped as "inwardly curved" instead of as "flat" the way we see it from within 8 billion light years all around us today...

Hi NY,

I have attached a rough drawing of what the gravitational abberation at the surface of a bowling ball might look like if you imagime the ball containing all the mass of the universe and a density approaching that of a black hole (extreme gravitational curvature). The grey disk represents the ball and an observer is standing at "A" on the surface. Light coming from objects on the surface of the ball follows curved paths but our eye and brain always perceives light as traveling in straight lines so that standing on the surface actually looks like you are inside a cavity. The illusion is not perfect and the distortion is in principle detectable with careful measurement. If the ball is expanding the outward motion of the observer on the surface further exagerates this abberation, possibly making it even harder to detect.

 

[DaveC426913]

I compare the Big Bang event to someone chewing bubblegum and then blowing a big bubble that expands forever. The "Bang part" itself happened at the person's lips and as he blew the bubble this became our ever expanding "3-D space".

The trouble with this analogy is that in the universe, there is no "at the person's lips". Your analogy suggests that there is a part of the bubble that could be identified as the origin, and this is not true in the BB.

Think of an analogy more like a sealed ball that has no spigot/nipple/whatever you want to call it - say, a beach ball. The sun heats the air inside the ball and that is what causes the expansion. The advantrage of this analogy is that the expansion occurs without having a single spot where it's expanding form.

 

[marcus]

very true.

it is of course still an analogy.

some people like the raisin / bread analogy better, but i don't like it as much as the balloon because it implies a finite distance to the crust/edge of the bread/universe unless you assume the bread is infinite.

the balloon allows a seemingly infinite universe containing a finite amount of matter/energy.

...and all it requires is an additional dimension.

:)

I'm with you on this. the raisinbread analogy doesn't contain the idea of curvature and how something can be finite volume without having any edge. it is more just a local image of expanding distances. you have to assume the dough is infinite.

the balloon analogy is more useful (even though space is only 2D in that analogy).

the additional dimension is not known by the 2D creatures to exist so it can be considered purely formal mathematical. the radius of the balloon is what is called the radius of curvature.

in our case we don't know it exists in some higher dim. surrounding, but we can calculate its length in various cases and estimate it based on CMB data and galaxy redshift survey data (numbers of galaxies counted at various distances)-----ways that have been devised to measure curvature, essentially like experimentally measuring the interior angles of large triangles.
==================

if the radius of curvature is R, then simple high school or college geometry can estimate the volume of 3D space to be 2 pi² R³
this is just the volume of a 3D sphere of radius R (pictured in 4D)
=================

I see some people in this thread are now getting hung up on asking how the balloon begins to expand!
that is not covered in classical (nonquantum) cosmology. It is the business of quantum cosmology to explore that and model it. That field has really taken off in the past 2 or 3 years. I don't know of any up-to-date popularization, but you can get a rough idea by skimming the abstracts in a keyword search of the technical literature using keywords "quantum cosmology". This is using the Stanford database:
http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=DK+quantum+cosmology+and+date+%3E+2005&FORMAT=WWW&SEQUENCE=citecount%28d%29

You can change the information in the search box and look at a longer timeframe like "date > 2001" or change the keywords and so on.
What I put in was "date > 2005" and asked for the papers to be sorted by how often they have been cited in other research, so the first ten or twenty that come up are probably the most important and representative of where the field is currently going.

this is the field of research grappling with the problem of modeling time and conditions right around the big bang or beginning of expansion

to me it seems inefficient to try to speculate on one's own about this before finding out what the relevant mainstream research community in that field is working on---but that seems to be what many of us (including in this thread) typically do

I suggest you sample it, Junglist, no need to delve unless you want, just read a few of the abstracts (the summaries) and get some impression---ask some questions here if something doesn't make sense. that is, if you are curious about current models of the big bang. Not to necessarily believe, but to sample what the professional mainstream is working on.

 

[BoomBoom]

the additional dimension is not known by the 2D creatures to exist so it can be considered purely formal mathematical. the radius of the balloon is what is called the radius of curvature.

I understand this analogy and the 2D people would understand that if they were to go in a straight line they would eventually come back around to where they started. But what if, since they knew what this curvature was, they decided to head out on a trajectory that countered the curvature so that it really was a straight line? I guess this would be a tangent line to the sphere?

Taking that analogy to our 3D universe and taking the same strategy, where would that take us?

 

[marcus]

... But what if, since they knew what this curvature was, they decided to head out on a trajectory...

you aren't empathizing with the too-dees (the 2D creatures). need to carefully put yourself in their shoes.

all trajectories lie in the 2D surface
all directions they can point in are in the 2D surface
any way you point, that direction extends in a geodesic (like a great circle on Earth surface) that stays in their world

they have no indication that any higher dimension surround exists, and it may not. We did not assume that they live in a 2D that is surrounded by an actual 3D. It might not be.

curvature is an intrinsic property that depends on internally measured distance and angle measurements. A surface can be curved without living in a higher dim surround. Riemann and Gauss realized this in 1850. You've got to realize it too, Boomboom.

Try to imagine yourself as a Toodee. No directions take you out of your world. Moving around and measuring let's you determine curvature by certain vintage 1850 formulas. Yet this does not prove that a higher dim exists. You might get it by thinking along these lines, Boomboom

 

[yuiop]

I understand this analogy and the 2D people would understand that if they were to go in a straight line they would eventually come back around to where they started...

On a slightly different tangent .. what if the ants left a trail ..then eventually if they continue in a straight line they could come across their original trail and begin to suspect their universe is not infinite.

Now extend this idea to the ants being on an expanding balloon. If the balloon radius expanded at the speed of light and if the ants moved in a great circle (their idea of a straight line) would they get back to their marked starting point in a finite time even if they moved around the circumferance at the speed of light (maybe they send a light beam around and see if it returns). Anyone care to work that one out, taking the spiral path into account?

 

[DaveC426913]

If the balloon radius expanded at the speed of light

The circumference of their spherical universe will increase at 2*pi*r per unit time. Since they are traveling at no faster than r per unit time, then no, they will never arrive back at their starting point.

 

[yuiop]

The circumference of their spherical universe will increase at 2*pi*r per unit time. Since they are traveling at no faster than r per unit time, then no, they will never arrive back at their starting point.

Thanks :) Obvious when you put it that way. I had a hunch it was true when I posed the question. So, in a way the finite (but expanding) surface of the balloon would be an infinite surface to the ants, because neither the ants nor any signals they send, can go round the balloon in a finite time. :)

 

[MiltMeyers]

BoomBoom Does this make sense. If we were living on the surface of a 2d world, the ballon. The balloon would be a finite world but now let's start out with a singularity of a balloon and the balloon inflates and keeps getting bigger. The galaxys are scattered about on the surface now if light left a galaxy and while it was in in flight the 2d universe exspanded. Now since the light came from inside the 2d world it came from a new dimension a 3d direction and would look straight but in fact it is bent in the 3d. Now change the balloon to what we live in what looks like a 3d world but in truth it is really 4d. Space is curved in 4d. Light is coming from a 4d direction and we see it as straight when in fact it is curved. Think this as we see further back in time the smaller the universe is so the space is curved to fit the now of space into the smaller now of time past. Now does that answer what I think to me is the effect of moving to 4d space time with the balloon analogy? I hope I have it figured out as to me it is simple but if you point out were I'm wrong I'll explode and keep my mouth shut. Bubble gum or bowling balls, hmmmmm, interesting ideas.

 

[DaveC426913]

Now since the light came from inside the 2d world it came from a new dimension a 3d direction and would look straight but in fact it is bent in the 3d.

Light does not come from inside the 2D world; it comes from any point on the surface of the 2D world. Light - like everything else - is constrained to the surface. Light beams follow world lines around the 2D world. When the Twodees measure anything in their world, their measurement tools (including the best ones - lasers) will follow the surface.

Now change the balloon to what we live in what looks like a 3d world but in truth it is really 4d. Space is curved in 4d. Light is coming from a 4d direction and we see it as straight when in fact it is curved.

Light is coming from any point in our 3D world and follows lines that we measure as straight, even if, when measured in 4space, those lines can be seen to curve.

 

[BoomBoom]

Try to imagine yourself as a Toodee. No directions take you out of your world. Moving around and measuring let's you determine curvature by certain vintage 1850 formulas. Yet this does not prove that a higher dim exists. You might get it by thinking along these lines, Boomboom

Yes, I believe I do get it... thank you Marcus.

Apologies for any frustration that trying to describe this may have caused...cheers! :)

 

[MiltMeyers]

Dave The beam of light followed the surface of the balloon but when it arrived it came from a point that is now inside the balloon. Now this curve is in the 3rd dimension. Scaling that up to our 4d world the light beam would have come from a point in a smaller universe. In fact all light beams would come from points in a smaller universe and that is in any direction we look. That is why we can only go to a smaller and smaller universe till we are back to the time just after the start were the universe is really small. That is our 4d universe. Finite and holding every bit of junk ever condensed out of the big bang. Our lives and posts and fights with that significant other.

Now let's look at what we see when we look out into space. We see star light coming to our eye in a straight line and it is red shifted and also is is from a smaller universe. That means it followed a curve in space. ie; a 3D straight line that is curved in the 4D time and space. Now does it make sense that there is no outside to the universe and no time or space before zero time and space? Due to relativity there is no now all over and what we see is what we get.

 

[DaveC426913]

Dave The beam of light followed the surface of the balloon but when it arrived it came from a point that is now inside the balloon. Now this curve is in the 3rd dimension. Scaling that up to our 4d world the light beam would have come from a point in a smaller universe. In fact all light beams would come from points in a smaller universe and that is in any direction we look. That is why we can only go to a smaller and smaller universe till we are back to the time just after the start were the universe is really small. That is our 4d universe. Finite and holding every bit of junk ever condensed out of the big bang. Our lives and posts and fights with that significant other.

Now let's look at what we see when we look out into space. We see star light coming to our eye in a straight line and it is red shifted and also is is from a smaller universe. That means it followed a curve in space. ie; a 3D straight line that is curved in the 4D time and space. Now does it make sense that there is no outside to the universe and no time or space before zero time and space? Due to relativity there is no now all over and what we see is what we get.

OK, I see what you're getting at. We're talking about two different things. I'll drop it.

 

[BoomBoom]

I was getting a sense of dejavu, then realized we have covered this ground before, as in this thread: (which may help others still struggling with the concept)
https://www.physicsforums.com/showthread.php?t=178063"

Again, apologies for the density of my skull... :O

 

[marcus]

Again, apologies for the density of my skull... :O

we can't easily gauge skull thickness here, with different people operating on different amounts of sleep and competing job-demands etc.
what I do get from you is a sense of good will. fair-mindedness

about repeating. yes we do go over this periodically
I don't know if that is bad, though. Or if we should try to avoid it by citing earlier discussion threads. sometimes new people need a fresh discussion
and old people (who were new last time) jump in and give them a workout

and old olds like me can sit back much of the time and watch with interest
it probably does no great harm to repeat stuff now and then, with a different cast of characters

 

[MiltMeyers]

Dave sorry I missed your point. The question; Does a finite universe make sense to you? I would say yes it does. I'm new to the forum and tend to jump in and say what I think. I didn't do any research(past posts) into balloons as universe models and if I had I would have held my post. Finite now what about if the space time exspanse and pushes a galaxy beyond light speed? Is that possible? In other words is there a horizon of visible light and the universe only appears to be finite?

 

[sketchtrack]

A finite universe only makes sense to me if there is something out there other than the universe. Maybe multiple finite universes, but that idea clashes with one definition of universe which is describes as everything that exists.

 

[epkid08]

I would define our universe as anything that's bounded by our universal dimensions.

 

[NYSportsguy]

The trouble with this analogy is that in the universe, there is no "at the person's lips". Your analogy suggests that there is a part of the bubble that could be identified as the origin, and this is not true in the BB.

Think of an analogy more like a sealed ball that has no spigot/nipple/whatever you want to call it - say, a beach ball. The sun heats the air inside the ball and that is what causes the expansion. The advantage of this analogy is that the expansion occurs without having a single spot where it's expanding form.

DaveC426913 - Dave the big question that is confusing many people is where the the "Big Bang" and it's rapid expansion originate from. That is why I brought up the "bubble gum" analogy because if you see this link below and read how most cosmologists think the "bang" happened...it is similar to my "bubble gum" analogy up top.

http://www.astro.princeton.edu/~aes/AST105/Readings/misconceptionsBigBang.pdf

 

[NYSportsguy]

By the way - It should be noted that from the article in that link, that galaxies can recede away FASTER that the speed of light without violating and special relativity laws because the expansion of space itself is not the same as traveling through space ALREADY CREATED.

So for all we know, the universe is actually expanding at speeds faster than "c" already. If that's the case we will NEVER catch up to the outer "surface" of this ball even if we could move at "c".

 

[NYSportsguy]

Spelling Correction: without violating any special relativity laws*