Random House Webster College Dictionary
The arch or vault of heaven; sky .
Firmament in the midst of the waters According to Relativity, light emitted by the sun should circumnavigate the universe to return to the point of origin? Well, someone told me that, a long time ago, so I tried to image what was meant by the statement.
Matter has mass & a center of gravity and if light circles the universe then the universe must have a radius & [light, electromagnetic radiation, etc.] a center of rotation? So in the truth {fashion, form} of Science, I chose an arbitrary point, the center of rotation. Note:
(a theoretical universe has been formed within the void of nonexistence.) Relativity
Qualifying statement: the center of rotation & the radius of the universe is assumed be the same as the center of mass of the universe & the arch of space is the same as that of light.) As our solar system is considered to exist in the fringe of larger gravitating body (galaxy) so to this body exist off center of the universe. Which implies the existence of other gravitating bodies without introducing them into theory as being relevant to the discussion. Likewise as theorized certain planet (moons, etc.) may form a subsystem of rotation around a gravitational center with our solar system. Giving distinction of a central mass of a sun that emits electromagnetic radiation in the visible light region is extended within the galaxy.
[/i] To simplify the construct uses the existence of this galaxy as being within the theoretical universe.
The centers of mass exist relative to but not at the center of rotation, therefore the laws of science are valid within the framework. Further simplification is given by stating that the inertial reference of all rotating bodies (planets, solar systems, galaxies, and universe) is clockwise (+). Thus counterclockwise (--) as counter rotational in direction to all bodies relative to the Solar- Earth system. [/i]
Now, looking in to the heavens we find ourselves immersed in a star field called the Milky Way & depending of course upon where on earth you observe from we see tiny points of lights, the stars. Let's call this point in time T0, the time of observation of emitted light of various suns (stars) just as the light of our own sun emits light. In physical reality, they are not points at all but because of their distance, we perceive them as points.
In physics, they can be considered as point source of light, because they emit light of relatively equal intensity in all directions. As the sun is some finite distance from the earth, the light reaching the earth at T0 was emitted at a prior time TE when it was emitted. So each star point must have a TE related to its distance from our point of observation. Also we should note that because the stars are in motion relative to the earth such that the position of the star at T0 has changed from the point of TE. In ancient times, man observed the world during the light of day and looking off to the horizon, he thought the world is flat. Setting his sail he ventured out in the waters, his destination lay beyond the horizon & though he sailed for many a day, the horizon remained beyond his reach. If he looked back the way he came, he would have seen the world he knew sinking out of his sight. Now we know the earth is a sphere, so let us venture beyond the horizon of space to perceive that existence to our dismay? Well, it sounded good in theory but the application has some drawbacks, the first of which is the need to define the horizon! Strange tale indeed which leads to resurrecting the flat earth theory?
In this world, the perception of a flat earth is a common misconception. We go to the hardware store to buy a level or better yet let's get one of those fancy rigs with the laser light projecting a strait line. From bricklayers to surveyor use the level, a bent tube filled with a liquid except for a tiny bubble of gas as reference to the flat, strait & level. (Actually what they do is set a plane {base} that is tangent to the {vertical} force of gravity) & what about the line projected is it strait? As an old professor used to say 'What is a strait line in a curved {world} universe' but more on that later? I don't want to make this to complicated so I looked in the dictionary, a shortcut. [b]Random House Webster College Dictionary
Horizon:{/b] 1) the line or circle that forms the apparent boundary between earth & sky.
2b) the great circle of the celestial sphere whose plane passes through the center of the earth & is parallel to the sensible of a given position or the plane of such a circle.
3) the limit or range of perception or knowledge.
O.K., now we put an asteroid at some point (midpoint) beyond the celestial horizon in a counterclockwise or (--) direction from earth => solar system => galaxy. It's a small hunk of rock so watch your step but as it has mass & obeys the laws of science. As the mariners of old we look back {(+) direction} & we see the light from the solar system => galaxy then if we look forward {(--) direction} we see the light from the solar system => galaxy. Of course, the T0 would have been emitted at TE & dependent upon the distance.
Oh, about the distance, the old professor was a mathematician & he taught that the shortest distance between any 2 points is a strait line between them. As the light of the stars would follow the curve of space, the shortest distance would be the line of action of gravity, the strait line between the points (masses).
{Just as the distance to moon to earth is the length between their centers but the distance traveled is a curve.} I should mention some other quirks as well. If you would look around you will see that stars {solar system => galaxies} although you are looking at different prospectus so some may look like ours, others will not as your view of them be relative to orientation in space. As light tends to act or have the property of waves, the additional factor of such would produce ghost (holograms) images of points of lights {solar system => galaxies} or stars . . . Teen did you wonder why I kept asking about the age of stars & how they came by them?
http://www.captaincynic.com/thread.php3/thrdid=27618-u-frmid=21 Never can tell maybe someday we will see the birth of a galaxy, our own.