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Top Document: [sci.astro] Time (Astronomy Frequently Asked Questions) (3/9) Previous Document: C.00 Time, Calendars, and Terrestrial Phenomena Next Document: C.02 What are all those different kinds of time? See reader questions & answers on this topic! - Help others by sharing your knowledge The international standard date notation is: YYYY-MM-DD For example, February 4, 1995 is written as 1995-02-04. This notation is standardized in International Standard ISO 8601. For more details regarding this standard, please <URL:http://www.cl.cam.ac.uk/~mgk25/iso-time.html>. Other commonly used notations are e.g., 2/4/95, 4/2/95, 4.2.1995, 04-FEB-1995, 4-February-1995, and many more. Especially the first two examples are dangerous, because as both are used quite often and can not be distinguished, it is unclear whether 2/4/95 means 1995-04-02 or 1995-02-04. Advantages of the ISO standard date notation are: - easily parsed by software (no 'JAN', 'FEB', ... table necessary) - easily sortable with a trivial string compare - language independent - can not be confused with other popular date notations - consistent with 24h time notation hh:mm:ss which comes also with the most significant component first and is consequently also easily sortable (e.g., write 1999-12-31 23:59:59). - short and has constant length (makes keyboard data entry easier) - identical to the Chinese date notation, so the largest cultural group (>25%) on this planet is already familiar with it. - 4-digit year representation avoids overflow problems after 1999-12-31. In shell scripts, use date "+%Y-%m-%d %H:%M:%S" in order to print the date and time in ISO format. In C, use the string "%Y-%m-%d %H:%M:%S" as the format specifier for strftime(). Other useful information on the ISO standard is at <URL: http://dmoz.org/Science/Reference/Standards/Individual_Standards/ISO_8601/ >. User Contributions:Comment about this article, ask questions, or add new information about this topic:Top Document: [sci.astro] Time (Astronomy Frequently Asked Questions) (3/9) Previous Document: C.00 Time, Calendars, and Terrestrial Phenomena Next Document: C.02 What are all those different kinds of time? 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