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Top Document: [sci.astro] Cosmology (Astronomy Frequently Asked Questions) (9/9) Previous Document: I.08. If the Universe is only 10 billion years old, how can we see objects that are now 30 billion light years away? Why Next Document: I.10. What is the Universe expanding into? See reader questions & answers on this topic! - Help others by sharing your knowledge Obviously, the Universe has to be older than the oldest stars in it. So this question basically asks, which estimate is wrong: * The age of the Universe? * The age of the oldest stars? or * Both? The age of the Universe is determined from its expansion rate: the Hubble constant, which is the ratio of the radial velocity of a distant galaxy to its distance. The radial velocity is easy to measure, but the distances are not. Thus there is currently a 15% uncertainty in the Hubble constant. Determining the age of the oldest stars requires a knowledge of their luminosity, which depends on their distance. This leads to a 25% uncertainty in the ages of the oldest stars due to the difficulty in determining distances. Thus the discrepancy between the age of the oldest things in the Universe and the age inferred from the expansion rate is within the current margin of error. 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.08. If the Universe is only 10 billion years old, how can we see objects that are now 30 billion light years away? Why Next Document: I.10. What is the Universe expanding into? 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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[sci.astro] Cosmology (Astronomy Frequently Asked Questions) (9/9)
Section - I.09. How can the oldest stars in the Universe be older than the Universe?
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[sci.astro] Cosmology (Astronomy Frequently Asked Questions) (9/9)
Section - I.09. How can the oldest stars in the Universe be older than the Universe?
( Part0 - Part1 - Part2 - Part3 - Part4 - Part5 - Part6 - Part7 - Part8 - Single Page
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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