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yajvan
26 April 2010, 09:33 PM
hariḥ oṁ
~~~~~

namasté

While listening to the radio ( called Science Friday on NPR radio in the USA), the scientist of astrophysics suggested the notion that the universe is flat.

While I listened I was some what aghast that the interviewer did not ponder, poke and query this idea further , his response was 'oh, ah-ha'.

Again I think how can this be? I recall reading some that hundreds of years ago the notion that the earth was also flat. Now if I were interviewing this scientist ( and by-the-by I have heard this idea before) I would ask or say the following.

When you say flat, do you mean only and X-axis and Y-axis exists and no z-axis ( no depth) ?
If its flat how flat is it? It is measured in light years flat? Define your envelope of flat please.
My experience ( and also Hubble's, the telescope) shows me photo's from different regions of the sky and this is in multiple 3 dimensional space... where is the flat there?
Once again I ponder additional observations that do not pass my common sense test.


praṇām

kd gupta
27 April 2010, 05:11 AM
If it was not elliptical or spherical , how one can reach usa from india either through west say france , or east say japan ?

Eastern Mind
27 April 2010, 07:50 AM
Vannakkam:

Yajvan: Methinks you read to many filler articles at the backs of newspapers or do to many searches on 'trivial scientific nonsense'.

Ahh... those theorists sure have a thing or two to lern us. Sounds like someone woke up on the flat side of bed, and needed to publish some sort of idea just to keep his research money coming along nicely so he could live in his rich flat with his flat cat, flat wife, amidst the flatulence, looking for some flattery.

Aum

saidevo
27 April 2010, 12:21 PM
namaste Yajvan.

Perhaps there is some truth in it? Flat of course should mean a 3-dimensional rectangle and not a flat 2-dimensional surface. Space is infinite, so what could be the geometrical shape of infinity? If it is a sphere, there is scope of some space being left out, because the sphere must be contained in something else. As against a spherical shape, a 3-D rectangle fills out completely leaving nothing. The universe is virtually infinite containing spherical bodies, so as a container I think its shape could be a cube or a 3-D rectangle.

But this suggestion poses one problem: directions. In a spherical model, the gradations of directions in the form of radii add up to 360 degrees, which is not possible in 3-dimensional a rectangular surface. But again, a spherical object by the action of its centrepetal and centrefugal forces tends to rotate around an axis, which may not be the case (I don't know) with a flat object.

The universe is a container and so is space. What is the best shape of a container? The answer perhaps lies in this question.

Ashvati
27 April 2010, 12:25 PM
The universe is totally shaped like a shivalinga :P (completely ignoring the fact that the vague, elliptical shape of a shivalinga means it would be a likely coincidence) Nah, I'm pretty sure the theory of a more or less flat universe is actually supported by evidence like how densely allocated stars are if you look from certain angles with a powerful enough telescope and by the fact that galaxies tend toward a disc-shape, but don't quote me on any of that, I was told all this in a high school science class and I'm 21 now.

yajvan
27 April 2010, 08:30 PM
hariḥ oṁ
~~~~~

namasté saidevo,


namaste Yajvan.

Perhaps there is some truth in it? Flat of course should mean a 3-dimensional rectangle and not a flat 2-dimensional surface. Space is infinite, so what could be the geometrical shape of infinity? If it is a sphere, there is scope of some space being left out, because the sphere must be contained in something else. As against a spherical shape, a 3-D rectangle fills out completely leaving nothing. The universe is virtually infinite containing spherical bodies, so as a container I think its shape could be a cube or a 3-D rectangle.

But this suggestion poses one problem: directions. In a spherical model, the gradations of directions in the form of radii add up to 360 degrees, which is not possible in 3-dimensional a rectangular surface. But again, a spherical object by the action of its centrepetal and centrefugal forces tends to rotate around an axis, which may not be the case (I don't know) with a flat object.

The universe is a container and so is space. What is the best shape of a container? The answer perhaps lies in this question.

I am happy many responded to this. Yet my brain cramp remains. What is on the other side if any shape? Box or sphere? If one says nothingness - I am fine with it, but it too must be part of the universe, as it ( the universe ) is mostly nothing ( space ) to begin with.

praṇām

sanjaya
28 April 2010, 08:26 PM
Alas, the problem with us astrophysicists is that we often throw out terminology without understanding that people outside the field won't know what we're talking about. Allow me to clarify.

The term "flat universe" is a technical and mathematical term from General Relativity. It means that the universe overall has a flat spacetime curvature. In layman's terms, it mean that two parallel lines will never get any closer together or further apart. In high school geometry we're taught that parallel lines always stay the same distance from each other. However, Euclidean geometry assumes a flat space. If our universe existed on a sphere, parallel lines can indeed converge. For example, say two people start from the same point and walk towards the north pole along different longitude lines. The earth looks flat from our position, so these people will seem to be walking parallel to one another. But they will get closer, and eventually meet at the north pole.

General relativity says that spacetime itself is somewhat like this. GR correctly predicts that our three dimensional space has a very small curvature. Of course we barely notice it, which is why we say that the universe is essentially flat. The curvature of the universe is an open problem in astrophysics and cosmology, and one theory states that the universe on a large scale is flat. When we say this, we're not saying that it's flat in our usual, three-dimensional sense of the word.


The universe is totally shaped like a shivalinga :P (completely ignoring the fact that the vague, elliptical shape of a shivalinga means it would be a likely coincidence) Nah, I'm pretty sure the theory of a more or less flat universe is actually supported by evidence like how densely allocated stars are if you look from certain angles with a powerful enough telescope and by the fact that galaxies tend toward a disc-shape, but don't quote me on any of that, I was told all this in a high school science class and I'm 21 now.

Actually this is a separate phenomenon. Galaxies, solar systems, accretion disks, etc. are in the shape of a disk because this is actually require by linear and angular momentum conservation laws. If a sphere of gas starts spinning because some angular momentum is imparted to it, it will eventually settle into a disk shape.

As for the universe as a whole, we actually see galaxies in virtually every direction. The only reason we see more stars along a certain plane is because we're looking at the galactic plane, essentially into our own galaxy. One way astrophysicists can know whether a certain source is inside our outside our galaxy (it's not as obvious as it would seem!) is by whether or not we're looking in the galactic plane. I would certainly hope that the universe isn't shaped like a disk. Most of the sources I look at are extragalactic, and without the distribution of galaxies in the night sky, my research would be impossible!

For what it's worth, I know that our Scriptures contain a certain creation myth in which the universe is created because Lord Vishnu and Lord Shiva found a linga and sought to found its edges.

Ashvati
28 April 2010, 10:38 PM
I've read that story, its in the Shiva puran, I've read parts of a poor translation of it and that story also contains one of the explanations behind Brahma not having a sect or being very popular. I'm pretty sure he decides to lie about finding its edge and either asks a lotus to lie for him and Shiva sees it because he sees everything, or he's overheard by a lotus who prays to Shiva to tell him about the lie.

TatTvamAsi
07 May 2010, 01:03 PM
Perhaps it appears flat in our (limited) perspective. We can only "see" or experience the three dimensions of space plus time.

What of the other 7 dimensions? At least, according to String Theory?

Hiwaunis
07 May 2010, 04:21 PM
Perhaps it appears flat in our (limited) perspective. We can only "see" or experience the three dimensions of space plus time.

What of the other 7 dimensions? At least, according to String Theory?

Pranam,
Oh great! What's next? God placed a firmament in space to separate our flat universe from all the other flat universes.

So, TT about string theory. Do you know if the scientist completed the machine that will enable strings to jump into our dimension?

Namaste,

yajvan
07 May 2010, 06:49 PM
hariḥ oṁ
~~~~~

namasté sanjaya ( et.al)


Allow me to clarify.

The term "flat universe" is a technical and mathematical term from General Relativity. It means that the universe overall has a flat spacetime curvature. In layman's terms, it mean that two parallel lines will never get any closer together or further apart. In high school geometry we're taught that parallel lines always stay the same distance from each other. However, Euclidean geometry assumes a flat space. If our universe existed on a sphere, parallel lines can indeed converge.

This was most helpful, thank you. It seems to me that a different term other then 'flat' would be most helpful, no?

Flat is 'flat bread' , 'flat as a pan cake', 'flat top' ( a hair cut I have tried!) :) . Yet in each case no-one took the time to explain the idea as you have , thank you ( seems straight forward).


Now that said, Lets take the notion of a sphere. This does not suggest I am a proponent of a spherical universe. You offer parallel lines meet i.e. lines that meet at the poles - makes sense. But what of latitude? Parallel to the equator. Each line of latitude is parallel to the the equator. When would these lines ever cross? Take the same concept and extend it to billions/zillions/googles of light years. When and why would they cross?
The error in my example is the lines are not 2 dimensional but are curvilinear - does this change the rules at all? Please advise.

Now that said, parallel lines - would they not always be parallel if only PURE SPACE is the medium? Do not include any gravity or outside influence - just pure space. What would cause the lines to cross if not acted upon by some force or bend outside of the lines themselves.

Please help me remove this mis-understanding if is is point blank incorrect.

thank you,

praṇām

sanjaya
10 May 2010, 11:09 AM
hariḥ oṁ
~~~~~

namasté sanjaya ( et.al)



This was most helpful, thank you. It seems to me that a different term other then 'flat' would be most helpful, no?

It might make more sense to use a different term when speaking to the general public. Or it might at least make sense for us to explain the term. "Flat universe" is, as I said, a technical term used by astrophysicists and cosmologists, so I think this is a case of someone throwing out specialized terminology without considering the audience he's speaking to.


Now that said, Lets take the notion of a sphere. This does not suggest I am a proponent of a spherical universe. You offer parallel lines meet i.e. lines that meet at the poles - makes sense. But what of latitude? Parallel to the equator. Each line of latitude is parallel to the the equator. When would these lines ever cross? Take the same concept and extend it to billions/zillions/googles of light years. When and why would they cross?
The error in my example is the lines are not 2 dimensional but are curvilinear - does this change the rules at all? Please advise.

That's actually a very good question. The answer is that latitude lines are not geodesics. On any surface, the geodesic is defined as the shortest path between any two points. On a sphere, the shortest path between two points will always be a segment of a great circle. A great circle is a circle on the surface of the sphere which has a radius equal to the sphere's radius. It may seem counterintuitive at first, but the shortest path between two points at the same latitude is not the path traced by the latitude line. If you look at the flight paths of intercontinental airline flights, you'll notice that they look very odd on a Mercator projection. For example, the shortest path between North America and Asia will often involve flying over the north pole. So in effect, latitude lines are not straight lines on a spherical geometry. Only great circles are straight lines, so we can only talk about two great circles being parallel.


Now that said, parallel lines - would they not always be parallel if only PURE SPACE is the medium? Do not include any gravity or outside influence - just pure space. What would cause the lines to cross if not acted upon by some force or bend outside of the lines themselves.

This is actually an open question in physics. The curvature of space-time comes from matter, which creates gravity. However, there's this whole business of the cosmological constant (or "dark energy") which may also cause curvature. In the moments immediately after the Big Bang, quantum fluctuations in various fields may have also caused anisotropic curvature which gave rise to the galaxies in the first place.

As you say, the universe will be flat unless some force is causing space-time to bend. But we are starting to learn that gravity is not the only thing that can make space-time bend.