What is the shape of the Universe?

[alokmohan]

I canot visualise a flat univ erse,other than old days,earth had two dimensions in past.

 

[kmarinas86]

It's stupid terminology.<br /><br />Whoever came up with it should be fired.

 

[MeteorWayne]

Actually, in mathematical terms (which is what it refers to) it is an extremely accurate (and specific) concept.<br /><br />It's only when people who don't understand that try and visualize it as a pancake that problems occur.<br /><br />It's mathematical flatness, not physical flatness. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[qso1]

On this, I'm not yet convinced. Why? Because if the Universe is flat...then we would now also know a structure beyond the Universe surrounds the Universe. A flat Universe can go on infinitely in only two directions if I understand shapes correctly. A flat Universe would go on in two directions to infinity but the third direction, the one that makes it flat...would be finite, or far smaller than the other two. In any case, some portion of this Universe exists within another entity.<br /><br />A spherical Universe could go on forever if expanded in all directions infinitely. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[kyle_baron]

<font color="yellow"><br />Spherical, Conical, Cubical, or saddle shaped? What is the current shape of this expanding balloon? </font><br /><br />http://en.wikipedia.org/wiki/Shape_of_the_Universe<br /><br />The last I heard from a Sky & Telescope article was that Omega = 1.003 Whether that is 1 (with the statistical error) or />1 is open to interpretation.<br /><br />http://en.wikipedia.org/wiki/Image:End_of_universe.jpg <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>

 

[georgewaters]

The earth our planet is spherical in shape.

 

[MeteorWayne]

Which has nothing to do with the original question.

 

[Gravity_Ray]

The earth our planet is spherical in shape.

It’s spherical but not a sphere. Correct name is a geoids, or ellipsoid (flatter on top and bottom and bulging on the sides). Who knows, maybe that’s the shape of the universe as well?

Meanwhile how do you describe a 5 dimensional shape to a 4 dimensional being? Why would you try?

 

[ramparts]

The earth our planet is spherical in shape.

It’s spherical but not a sphere. Correct name is a geoids, or ellipsoid (flatter on top and bottom and bulging on the sides). Who knows, maybe that’s the shape of the universe as well?

Meanwhile how do you describe a 5 dimensional shape to a 4 dimensional being? Why would you try?

Read Flatland

 

[alphachapmtl]

"Spherical, Conical, Cubical, or saddle shaped?"
We are nowhere near being able to meaningfully ask such questions.
It's like a tiny bacteria floating in the ocean and asking if the waterworld is a cube or a tetrahedra.

 

[ZenGalacticore]

If there is nothing without the Universe, how can it be in a shape?

When cosmologists and physicists say that the Universe is "saddle shaped", or "flat", or "spherical", it means nothing, really.

"Flat", or "spherical", relative to what?

 

[amshak]

Most astronomers would like to know the shape of the universe too! There are three general possibilities. First, like your balloon, the universe might have what we call positive curvature, like a sphere.
The second possibility is that the universe is flat. This kind of universe you can imagine by cutting out a piece of your baloon material and stretching it with your hands. Flat universes are infinite in spatial extent, and have no boundaries. Parallel lines are always parallel and triangles always have 180 degrees. Flat universes expand forever, but the expansion rate approaches zero.
Finally, the universe might be "open," or have negative curvature. Such universes are sort of saddle-shaped. They are also infinite and unbounded.
So we have many possiblities. I can not think about The second Big Bang.

 

[ramparts]

If there is nothing without the Universe, how can it be in a shape?

When cosmologists and physicists say that the Universe is "saddle shaped", or "flat", or "spherical", it means nothing, really.

"Flat", or "spherical", relative to what?

Relative to itself. It refers to the intrinsic geometry (or in some cases, topology) of the universe. Imagine you were a 2-D being who lived on a flat 2-D surface. You could do some tests (measure the angles of big triangles and such) and figure out that your space is more or less flat. If you lived on the surface of a sphere, however, and it were sufficiently big, then it might seem flat to you until you started doing those tests (and seeing that the angles of triangles added up to more than 180 degrees or something).

Now, in all of these examples I'm talking about a 2-D surface embedded in a larger 3-D space. Now, the key thing about spacetime is that mathematically it doesn't need to be embedded in a higher-dimensional space in order to have curvature. So in a bizarro world, that spherical 2-D surface we were just talking about could exist on its own, without there being a 3-D surface for it to be in, and as far as the dude living on that surface is concerned, there's no difference, mathematically or physically. In fact, that's how general relativity works. All curved spacetimes have "intrinsic curvature" where the properties are the exact same as if it were curved in a higher dimension, but that higher dimension just isn't necessary.

 

[ZenGalacticore]

Ramp- Yeah, I've been familiar with the 'Flatlander' analogy of over 30 years. To my mind, the Universe must be warped into a 4th physical dimension. But that suggests there is really something "outside" of the so-called Universe.

 

[ramparts]

Ramp- Yeah, I've been familiar with the 'Flatlander' analogy of over 30 years. To my mind, the Universe must be warped into a 4th physical dimension. But that suggests there is really something "outside" of the so-called Universe.

I mean, it doesn't. The fact that you have trouble visualizing something doesn't "suggest" that it's not true.