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Top Document: [sci.astro] Cosmology (Astronomy Frequently Asked Questions) (9/9) Previous Document: I.02. Why do astronomers favor the Big Bang model of the Universe? Next Document: I.04. What do people mean by an "open," "flat," or "closed" Universe? See reader questions & answers on this topic! - Help others by sharing your knowledge Often when people are told that galaxies are receding from us, they assume that means we are at the center of the Universe. However, remember that the Universe is homogeneous and isotropic. No matter where one is, it looks the same in all directions. Thus, all galaxies see all other galaxies receding from them. Hubble's relationship is compatible with a Copernican view of the Universe: Our position is not a special one. So where is the center? *There isn't one*. Although apparently nonsensical, consider the same question about the *surface* of a sphere (note the *surface*). Where's the center of a sphere's surface? Of course, there isn't one. One cannot point to any point on a sphere's surface and say that, here is the center. Similarly, because the Universe is homogeneous and isotropic, all we can say is that, in the past, galaxies were closer together. We cannot say that galaxies started expanding from any particular point. User Contributions:Comment about this article, ask questions, or add new information about this topic:Top Document: [sci.astro] Cosmology (Astronomy Frequently Asked Questions) (9/9) Previous Document: I.02. Why do astronomers favor the Big Bang model of the Universe? Next Document: I.04. What do people mean by an "open," "flat," or "closed" Universe? Part0 - Part1 - Part2 - Part3 - Part4 - Part5 - Part6 - Part7 - Part8 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: jlazio@patriot.net
Last Update March 27 2014 @ 02:11 PM
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with stars, then every direction you looked would eventually end on
the surface of a star, and the whole sky would be as bright as the
surface of the Sun.
Why would anyone assume this? Certainly, we have directions where we look that are dark because something that does not emit light (is not a star) is between us and the light. A close example is in our own solar system. When we look at the Sun (a star) during a solar eclipse the Moon blocks the light. When we look at the inner planets of our solar system (Mercury and Venus) as they pass between us and the Sun, do we not get the same effect, i.e. in the direction of the planet we see no light from the Sun? Those planets simply look like dark spots on the Sun.
Olbers' paradox seems to assume that only stars exist in the universe, but what about the planets? Aren't there more planets than stars, thus more obstructions to light than sources of light?
What may be more interesting is why can we see certain stars seemingly continuously. Are there no planets or other obstructions between them and us? Or is the twinkle in stars just caused by the movement of obstructions across the path of light between the stars and us? I was always told the twinkle defines a star while the steady light reflected by our planets defines a planet. Is that because the planets of our solar system don't have the obstructions between Earth and them to cause a twinkle effect?
9-14-2024 KP