Sundial | Wikipedia audio article
Channel: Subhajit Sahu
Date: 2018-12-14

This is an audio version of the Wikipedia Article:
Sundial


00:01:14 1 Introduction
00:04:23 2 Apparent motion of the Sun
00:07:13 3 History
00:08:32 4 Terminology
00:11:35 5 Sundials in the Southern Hemisphere
00:13:20 6 Adjustments to calculate clock time from a sundial reading
00:14:12 6.1 Summer (daylight saving) time correction
00:14:35 6.2 Time-zone (longitude) correction
00:16:04 6.3 Equation of time correction
00:20:06 7 Sundials with fixed axial gnomon
00:22:01 7.1 Empirical hour-line marking
00:23:25 7.2 Equatorial sundials
00:26:36 7.3 Horizontal sundials
00:30:56 7.4 Vertical sundials
00:35:01 7.5 Polar dials
00:36:45 7.6 Vertical declining dials
00:41:11 7.7 Reclining dials
00:44:42 7.8 Declining-reclining dials/ Declining-inclining dials
00:54:41 7.8.1 Empirical method
00:55:11 7.9 Spherical sundials
00:56:45 7.10 Cylindrical, conical, and other non-planar sundials
00:57:37 8 Movable-gnomon sundials
00:58:16 8.1 Universal equinoctial ring dial
00:59:52 8.2 Analemmatic sundials
01:00:39 8.3 Foster-Lambert dials
01:01:55 9 Altitude-based sundials
01:03:24 9.1 Human shadows
01:04:11 9.2 Shepherd's dial – timesticks
01:06:16 9.3 Ring dials
01:06:48 9.4 Card dials (Capuchin dials)
01:07:54 9.5 Navicula
01:08:25 10 Nodus-based sundials
01:10:17 10.1 Reflection sundials
01:11:03 11 Multiple dials
01:11:51 11.1 Diptych (tablet) sundial
01:12:56 11.2 Multiface dials
01:13:49 11.3 Prismatic dials
01:14:15 12 Unusual sundials
01:14:24 12.1 Benoy dials
01:15:37 12.2 Bifilar sundial
01:16:04 12.3 Digital sundial
01:16:31 12.4 Globe dial
01:16:59 12.5 Noon marks
01:18:06 12.6 Sundial cannon
01:18:53 13 Meridian lines
01:19:26 14 Sundial mottoes
01:20:09 15 Using a sundial as a compass
01:21:33 16 See also



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SUMMARY
=======
A sundial is a device that tells the time of day when there is sunlight by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat plate (the dial) and a gnomon, which casts a shadow onto the dial. As the Sun appears to move across the sky, the shadow aligns with different hour-lines, which are marked on the dial to indicate the time of day. The style is the time-telling edge of the gnomon, though a single point or nodus may be used. The gnomon casts a broad shadow; the shadow of the style shows the time. The gnomon may be a rod, wire, or elaborately decorated metal casting. The style must be parallel to the axis of the Earth's rotation for the sundial to be accurate throughout the year. The style's angle from horizontal is equal to the sundial's geographical latitude.
In a broader sense, a sundial is any device that uses the Sun's altitude or azimuth (or both) to show the time. In addition to their time-telling function, sundials are valued as decorative objects, literary metaphors, and objects of mathematical study.
It is common for inexpensive, mass-produced decorative sundials to have incorrectly aligned gnomons and hour-lines, which cannot be adjusted to tell correct time.