What shape is the sky?

Question

Just a thought

Answer 1

It appears to have no shape.

Answer 2

If we define 'sky' as everything we have above our heads, than it would be the shape of the universe. According to the physical theory, the universe (sky):

Local geometries

There are three categories for the possible spatial geometries of constant curvature, depending on the sign of the curvature. If the curvature is exactly zero, then the local geometry is flat; if it is positive, then the local geometry is spherical, and if it is negative than the local geometry is hyperbolic.
The local geometry of the Universe is determined by whether Omega is less than, equal to or greater than 1. From top to bottom: a spherical Universe, a hyperbolic Universe, and a flat Universe.


If the observable Universe is spatially "nearly flat", then a simplification can be made whereby the dynamic, accelerating dimension of the geometry can be separated and omitted by invoking comoving coordinates. Comoving coordinates, from a single frame of reference, leave a static geometry of three spatial dimensions.

Under the assumption that the Universe is homogeneous and isotropic, the curvature of the observable Universe, or the local geometry, is described by one of the three "primitive" geometries:

* 3-dimensional Euclidean geometry, generally annotated as E^3
* 3-dimensional spherical geometry with a small curvature, often annotated as S^3
* 3-dimensional hyperbolic geometry with a small curvature, often annotated as H^3

Global geometry

Flat Universe

In a flat universe, all of the local curvature and local geometry is flat. In general it can be described by Euclidian space, however there are some spatial geometries which are flat and bounded in one or more directions. These include, in two dimensions, the cylinder and the torus. Similar spaces in three dimensions also exist.

Spherical Universe

A positively curved universe is described by spherical geometry, and can be thought of as a three-dimensional hypersphere.

One of the endeavors in the analysis of data from the Wilkinson Microwave Anisotropy Probe (WMAP) is to detect multiple "back-to-back" images of the distant Universe in the cosmic microwave background radiation. Assuming the light has enough time since its origin to travel around a bounded Universe, multiple images may be observed. While current results and analysis do not rule out a bounded topology, if the Universe is bounded then the spatial curvature is small, just as the spatial curvature of the surface of the Earth is small compared to a horizon of a thousand kilometers or so.

Based on analysis of the WMAP data, cosmologists during 2004-2006 focused on the Poincaré dodecahedral space (PDS), but also considered horn topologies to be compatible with the data.

Hyperbolic Universe

A hyperbolic universe (frequently but confusingly called "open") is described by hyperbolic geometry, and can be thought of as something like a three-dimensional equivalent of an infinitely extended saddle shape. For hyperbolic local geometry, many of the possible three-dimensional spaces are informally called horn topologies.

The ultimate fate of an open universe is that it will continue to expand forever, ending in a Heat Death, a Big Freeze or a Big Rip.
Even if the Universe is not exactly spatially flat, the spatial curvature is close enough to zero to place the radius at approximately the horizon of the observable Universe or beyond.

The most common belief now is that our universe is of the third sort: flat. So your sky is flat.

Answer 3

It doesn't have a shape. Technically, it's not actually there. The sky as we see it during the day is a result of the shortest light waves (blue) reflecting off the atmosphere and invading our eyes. The sky at night is just space and stuff.

Answer 4

It would be a shape of sphere. From any given point on the earth, there is sky, and then the outer space. Since the earth is sphere, the sky would have a shape of a sphere.

Answer 5

It's the shape of the illumation created by whatever lightsource allows you to see it. Moon,sun,ect. You can look AT the sky. You look out into space.

Answer 6

It has the shape of the expanding universe or the magnanimous mind

Answer 7

the sky doen't have a shape

Answer 8

Amorphous ☺


Doug

Answer 9

I like the way you think, where does the sky end and space begin ??????????????????????????????. Get back to me on that one.

Answer 10

it's an octagon