Top Document: [sci.astro] Galaxies (Astronomy Frequently Asked Questions) (8/9) Previous Document: H.06 What are QSO's ("quasars")? Next Document: H.08 What about apparent faster-than-light motions? See reader questions & answers on this topic! - Help others by sharing your knowledge It's often suggested that QSOs are not at the distances that would be inferred from their redshifts and from Hubble's law; this would avoid the enormous powers and necessity for general-relativistic physics in the standard model. Many arguments of this type are flawed by a lack of consideration of the other types of galaxies and active galactic nuclei (AGN): unless it's believed that _no_ galaxy is at its redshift distance, i.e., that the whole concept of redshift is wrong, then we know that there are objects very similar to QSOs which _are_ at their redshift distances. (Cosmological theories that overthrow the whole idea of redshift and the big bang are beyond the scope of this discussion, although several have been proposed based on the apparent spatial association of objects with very different redshifts.) Another argument favoring QSOs being at their redshift distance comes from gravitational lensing. Gravitational lenses occur when two objects are nearly aligned, and the mass of the foreground object lenses (magnifies and/or distorts) the background object. In every gravitational lens for which redshifts are known, the galaxy (or galaxies) acting as the lens has a lower redshift than the galaxy being lensed. A recent analysis of data available from the 2-degree field (2dF survey) also showed no evidence for a connection between galaxies and QSOs. This analysis is particularly significant because the people who carried out the analysis spoke to proponents on both sides of the argument *before* conducting their analysis (Hawkins, Maddox, & Merrifield 2002, Mon. Not. R. Astron. Soc., vol. 336, p. L13). More generally, though, like many arguments in science, this one also has an element of aesthetics. The proponents of the standard model argue that the physics we know (general relativity, special relativity, electromagnetism) is sufficient to explain QSOs, and that, by Occam's razor, no model introducing new physics is necessary. Its opponents argue either that there are features of QSOs which cannot be explained by the standard model or that the predictions of the standard model (and, in particular, its reliance on supermassive black holes) are so absurd as clearly to require some new physics. A good deal of bad science has been put forward (on both sides) on sci.astro. Readers should be aware that the scientific community isn't as insanely conservative as some posters would have them believe, and that a number of other possibilities for QSO physics were considered and rejected when they were first discovered. For example, the frequent suggestion that the redshifts of QSOs are gravitational does not work in any simple model. Species having different ionization potentials ought to exist at different distances from the central source and thus should have different redshifts, but in fact emission lines from all species are observed to have the same redshift. For examples of claims of galaxy-QSO associations, see papers by Stockton, either of the Burbidges, or Arp. For additional, technical discussions of why these conclusions are not valid, see papers by Newman & Terzian; Newman, Terzian, & Haynes; and Hawkins, Maddox, & Merrifield (2002). User Contributions:Comment about this article, ask questions, or add new information about this topic:Top Document: [sci.astro] Galaxies (Astronomy Frequently Asked Questions) (8/9) Previous Document: H.06 What are QSO's ("quasars")? Next Document: H.08 What about apparent faster-than-light motions? 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