Sundials and Gnomons - Revision history

DT Online at 08:51, 7 August 2018

2018-08-07T08:51:26Z

← Older revision		Revision as of 08:51, 7 August 2018
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	=====Introduction=====		=====Introduction=====

	It is possible that we have used the movement of the sun since [https://en.wikipedia.org/wiki/Stone_circles_in_the_British_Isles_and_Brittany '''Neolithic'''] times to mark changing seasons and [http://en.wikipedia.org/wiki/Sundial '''Sundials'''] of a type may have been invented in [https://en.wikipedia.org/wiki/Chinese_Traditional_Time_System '''China'''] or by the '''[[:Category:Ancient Egypt\|Ancient Egyptians]]''' and [http://en.wikipedia.org/wiki/Babylonia '''Babylonians''']. But it was the '''[[:Category:Ancient Greece\|Ancient Greeks]]''' and '''[[:Category:Romans\|Romans]]''' who appear to have developed them in the form we see today.		It is possible that we have used the movement of the sun since [https://en.wikipedia.org/wiki/Stone_circles_in_the_British_Isles_and_Brittany '''Neolithic'''] times to mark changing seasons and [http://en.wikipedia.org/wiki/Sundial '''Sundials'''] of a type may have been invented in [https://en.wikipedia.org/wiki/Chinese_Traditional_Time_System '''China'''] or by the '''[[:Category:Ancient Egypt\|Ancient Egyptians]]''' and [http://en.wikipedia.org/wiki/Babylonia '''Babylonians''']. But it was the '''[[:Category:Ancient Greece\|Ancient Greeks]]''' and '''[[:Category:The Romans\|Romans]]''' who appear to have developed them in the form we see today.

DT Online at 08:47, 7 August 2018

2018-08-07T08:47:38Z

← Older revision		Revision as of 08:47, 7 August 2018
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	[[File:VerticalSundial.png\|400px\|right]]		[[File:VerticalSundial.png\|400px\|right]]

	'''Sundials''' can be designed such that the '''Dial''' is vertical and can be fixed to a wall but the [http://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] must still be positioned such that it remains parallel to the Earth's vertical axis ''(i.e. set at the ~~angle~~ of '''[[Latitude]]''' ~~to the horizontal~~)''.		'''Sundials''' can be designed such that the '''Dial''' is vertical and can be fixed to a wall. In this position, the '''Dial''' is '''[[Circles\|Normal]]''' to the surface of the earth but the [http://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] must still be positioned such that it remains parallel to the Earth's vertical axis ''(i.e. set at an angle to the '''Dial''' of 90<small><sup>0</sup></small> less the '''[[Latitude]]''')''.

DT Online at 08:18, 14 December 2017

2017-12-14T08:18:41Z

← Older revision		Revision as of 08:18, 14 December 2017
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	=====Introduction=====		=====Introduction=====

	[http://en.wikipedia.org/wiki/Sundial '''Sundials'''] of a type may have been invented by the '''[[:Category:Ancient Egypt\|Ancient Egyptians]]''' and [http://en.wikipedia.org/wiki/Babylonia '''Babylonians'''] ~~but~~ it was the '''[[:Category:Ancient Greece\|Ancient Greeks]]''' and '''[[:Category:Romans\|Romans]]''' who developed them.		It is possible that we have used the movement of the sun since [https://en.wikipedia.org/wiki/Stone_circles_in_the_British_Isles_and_Brittany '''Neolithic'''] times to mark changing seasons and [http://en.wikipedia.org/wiki/Sundial '''Sundials'''] of a type may have been invented in [https://en.wikipedia.org/wiki/Chinese_Traditional_Time_System '''China'''] or by the '''[[:Category:Ancient Egypt\|Ancient Egyptians]]''' and [http://en.wikipedia.org/wiki/Babylonia '''Babylonians''']. But it was the '''[[:Category:Ancient Greece\|Ancient Greeks]]''' and '''[[:Category:Romans\|Romans]]''' who appear to have developed them in the form we see today.

DT Online at 09:22, 1 March 2017

2017-03-01T09:22:17Z

← Older revision		Revision as of 09:22, 1 March 2017
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	[[File:Horus Sundials Portable Horizontal Sundial.jpg\|right\|300px\|Horus Sundials Portable Horizontal Sundial\|link=~~https~~://commons.wikimedia.org/wiki/File:Horus_Sundials_Portable_Horizontal_Sundial.jpg]]		[[File:Horus Sundials Portable Horizontal Sundial.jpg\|right\|300px\|Horus Sundials Portable Horizontal Sundial\|link=http://commons.wikimedia.org/wiki/File:Horus_Sundials_Portable_Horizontal_Sundial.jpg]]
	__TOC__		__TOC__

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	=====Introduction=====		=====Introduction=====

	[~~https~~://en.wikipedia.org/wiki/Sundial '''Sundials'''] of a type may have been invented by the '''[[:Category:Ancient Egypt\|Ancient Egyptians]]''' and [~~https~~://en.wikipedia.org/wiki/Babylonia '''Babylonians'''] but it was the '''[[:Category:Ancient Greece\|Ancient Greeks]]''' and '''[[:Category:Romans\|Romans]]''' who developed them.		[http://en.wikipedia.org/wiki/Sundial '''Sundials'''] of a type may have been invented by the '''[[:Category:Ancient Egypt\|Ancient Egyptians]]''' and [http://en.wikipedia.org/wiki/Babylonia '''Babylonians'''] but it was the '''[[:Category:Ancient Greece\|Ancient Greeks]]''' and '''[[:Category:Romans\|Romans]]''' who developed them.


	At their simplest, [~~https~~://en.wikipedia.org/wiki/Sundial '''Sundials'''] comprise a rod ''(known as the '''Gnomon''')'' casting the sun's shadow onto a flat plate. They are commonly mounted either horizontally or vertically but other variations also exist ''(e.g. on curved plates)''.		At their simplest, [http://en.wikipedia.org/wiki/Sundial '''Sundials'''] comprise a rod ''(known as the '''Gnomon''')'' casting the sun's shadow onto a flat plate. They are commonly mounted either horizontally or vertically but other variations also exist ''(e.g. on curved plates)''.


	[~~https~~://en.wikipedia.org/wiki/Gnomon '''Gnomons'''] should point to the '''[[Finding True North\|True North]]''' and be set at an angle such that it runs parallel to the Earth's axis. This is achieved by setting it to an angle to the horizontal which is equal to the '''[[Latitude]]''' of the mounting location ''(e.g. 51<sup><small>0</small></sup>30' in London)''. Horizontal '''Dials''' should be set level and vertical '''Dials''' either placed on a South-facing wall or the '''Gnomon''' angled such that the shadow at noon is vertical.		[http://en.wikipedia.org/wiki/Gnomon '''Gnomons'''] should point to the '''[[Finding True North\|True North]]''' and be set at an angle such that it runs parallel to the Earth's axis. This is achieved by setting it to an angle to the horizontal which is equal to the '''[[Latitude]]''' of the mounting location ''(e.g. 51<sup><small>0</small></sup>30' in London)''. Horizontal '''Dials''' should be set level and vertical '''Dials''' either placed on a South-facing wall or the '''Gnomon''' angled such that the shadow at noon is vertical.


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	The ‘stick’ which casts the shadow is known as the [~~https~~://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] and designs of Sundials placed on any position on the surface of the Earth should enable the [~~https~~://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] to remain parallel to the Earth's vertical axis.		The ‘stick’ which casts the shadow is known as the [http://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] and designs of Sundials placed on any position on the surface of the Earth should enable the [http://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] to remain parallel to the Earth's vertical axis.


	Sundials where this can be achieved by having the [~~https~~://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] at right angles to the '''Dial''' plate are known as [~~https~~://en.wikipedia.org/wiki/Sundial#Equatorial_sundials '''Equatorial Sundials'''] since the '''Dial''' must be parallel to the [~~https~~://en.wikipedia.org/wiki/Equator '''Equator'''].		Sundials where this can be achieved by having the [http://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] at right angles to the '''Dial''' plate are known as [http://en.wikipedia.org/wiki/Sundial#Equatorial_sundials '''Equatorial Sundials'''] since the '''Dial''' must be parallel to the [http://en.wikipedia.org/wiki/Equator '''Equator'''].
	[[File:HorizontalSundial.png\|400px\|right]]		[[File:HorizontalSundial.png\|400px\|right]]

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	=====Horizontal Sundial=====		=====Horizontal Sundial=====

	[~~https~~://en.wikipedia.org/wiki/Sundial#Horizontal_sundials '''Horizontal Sundials'''] are perhaps the most common but many are purchased with little understanding of how to make them accurate.		[http://en.wikipedia.org/wiki/Sundial#Horizontal_sundials '''Horizontal Sundials'''] are perhaps the most common but many are purchased with little understanding of how to make them accurate.


	The '''Dial''' is positioned horizontal relative to its location on the Earth's surface, which means it must be '''[[Tangents and Normals\|Tangential]]''' to the curve of the Earth and set such that its [~~https~~://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] points to '''[[Finding True North\|True North]]'''. A simple geometric analysis will reveal that if the [~~https~~://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] is to remain parallel to the Earth's vertical axis, it must be set at an angle to the horizontal '''Dial''' which is equal to the '''[[Latitude]]''' of its location.		The '''Dial''' is positioned horizontal relative to its location on the Earth's surface, which means it must be '''[[Tangents and Normals\|Tangential]]''' to the curve of the Earth and set such that its [http://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] points to '''[[Finding True North\|True North]]'''. A simple geometric analysis will reveal that if the [http://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] is to remain parallel to the Earth's vertical axis, it must be set at an angle to the horizontal '''Dial''' which is equal to the '''[[Latitude]]''' of its location.


	It can be seen that '''Horizontal Sundials''' work best at higher '''[[Latitude\|Latitudes]]''' rather than near the [~~https~~://en.wikipedia.org/wiki/Equator '''Equator'''].		It can be seen that '''Horizontal Sundials''' work best at higher '''[[Latitude\|Latitudes]]''' rather than near the [http://en.wikipedia.org/wiki/Equator '''Equator'''].

	----		----
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	[[File:VerticalSundial.png\|400px\|right]]		[[File:VerticalSundial.png\|400px\|right]]

	'''Sundials''' can be designed such that the '''Dial''' is vertical and can be fixed to a wall but the [~~https~~://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] must still be positioned such that it remains parallel to the Earth's vertical axis ''(i.e. set at the angle of '''[[Latitude]]''' to the horizontal)''.		'''Sundials''' can be designed such that the '''Dial''' is vertical and can be fixed to a wall but the [http://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] must still be positioned such that it remains parallel to the Earth's vertical axis ''(i.e. set at the angle of '''[[Latitude]]''' to the horizontal)''.


	[~~https~~://en.wikipedia.org/wiki/Sundial#Vertical_sundials '''Vertical Sundials'''] are ideally positioned on to a South-facing wall. In this situation the [~~https~~://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] lies in a vertical plane at right angles to the '''Dial''' and the shadow cast at Noon is vertical. This must always be the case, so if the wall chosen is not South-facing the vertical plane containing the [~~https~~://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] must be angled round to ensure its shadow remains vertical at Noon.		[http://en.wikipedia.org/wiki/Sundial#Vertical_sundials '''Vertical Sundials'''] are ideally positioned on to a South-facing wall. In this situation the [http://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] lies in a vertical plane at right angles to the '''Dial''' and the shadow cast at Noon is vertical. This must always be the case, so if the wall chosen is not South-facing the vertical plane containing the [http://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] must be angled round to ensure its shadow remains vertical at Noon.


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	It can be seen that '''Vertical Sundials''' work well if nearer to the [~~https~~://en.wikipedia.org/wiki/Equator '''Equator'''] than the North Pole.		It can be seen that '''Vertical Sundials''' work well if nearer to the [http://en.wikipedia.org/wiki/Equator '''Equator'''] than the North Pole.

	----		----

DT Online at 15:54, 5 November 2016

2016-11-05T15:54:34Z

← Older revision		Revision as of 15:54, 5 November 2016
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	Walls which are not directly South-facing are said to be '''Declined''' either East or West.		Walls which are not directly South-facing are said to be '''Declined''' either East or West.


			It can be seen that '''Vertical Sundials''' work well if nearer to the [https://en.wikipedia.org/wiki/Equator '''Equator'''] than the North Pole.

	----		----

DT Online at 15:53, 5 November 2016

2016-11-05T15:53:13Z

← Older revision		Revision as of 15:53, 5 November 2016
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	The '''Dial''' is positioned horizontal relative to its location on the Earth's surface, which means it must be '''[[Tangents and Normals\|Tangential]]''' to the curve of the Earth and set such that its [https://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] points to '''[[Finding True North\|True North]]'''. A simple geometric analysis will reveal that if the [https://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] is to remain parallel to the Earth's vertical axis, it must be set at an angle to the horizontal '''Dial''' which is equal to the '''[[Latitude]]''' of its location.		The '''Dial''' is positioned horizontal relative to its location on the Earth's surface, which means it must be '''[[Tangents and Normals\|Tangential]]''' to the curve of the Earth and set such that its [https://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] points to '''[[Finding True North\|True North]]'''. A simple geometric analysis will reveal that if the [https://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] is to remain parallel to the Earth's vertical axis, it must be set at an angle to the horizontal '''Dial''' which is equal to the '''[[Latitude]]''' of its location.


			It can be seen that '''Horizontal Sundials''' work best at higher '''[[Latitude\|Latitudes]]''' rather than near the [https://en.wikipedia.org/wiki/Equator '''Equator'''].

	----		----

DT Online: Added Category

2016-10-18T20:21:55Z

Added Category

← Older revision		Revision as of 20:21, 18 October 2016
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	[[Category:Topics]]		[[Category:Topics]]
	[[Category:Ancient Egypt]]		[[Category:Ancient Egypt]]
			[[Category:Sundials]]

DT Online at 21:46, 12 October 2016

2016-10-12T21:46:15Z

← Older revision		Revision as of 21:46, 12 October 2016
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	=====Introduction=====		=====Introduction=====

	[https://en.wikipedia.org/wiki/Sundial '''Sundials''''] of a type may have been invented by the '''[[:Category:Ancient Egypt\|Ancient Egyptians]]''' and [https://en.wikipedia.org/wiki/Babylonia '''Babylonians'''] but it was the '''[[:Category:Ancient Greece\|Ancient Greeks]]''' and '''[[:Category:Romans\|Romans]]''' who developed them.		[https://en.wikipedia.org/wiki/Sundial '''Sundials'''] of a type may have been invented by the '''[[:Category:Ancient Egypt\|Ancient Egyptians]]''' and [https://en.wikipedia.org/wiki/Babylonia '''Babylonians'''] but it was the '''[[:Category:Ancient Greece\|Ancient Greeks]]''' and '''[[:Category:Romans\|Romans]]''' who developed them.

DT Online: Added Category

2016-10-12T19:04:28Z

Added Category

← Older revision		Revision as of 19:04, 12 October 2016
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	{{Sundials Buyers Guide}}		{{Sundials Buyers Guide}}

			[[Category:Topics]]
			[[Category:Ancient Egypt]]

DT Online at 18:57, 12 October 2016

2016-10-12T18:57:06Z

← Older revision		Revision as of 18:57, 12 October 2016
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	Sundials where this can be achieved by having the [https://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] at right angles to the '''Dial''' plate are known as [https://en.wikipedia.org/wiki/Sundial#Equatorial_sundials '''Equatorial Sundials'''] since the '''Dial''' must be parallel to the [https://en.wikipedia.org/wiki/Equator '''Equator'''].		Sundials where this can be achieved by having the [https://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] at right angles to the '''Dial''' plate are known as [https://en.wikipedia.org/wiki/Sundial#Equatorial_sundials '''Equatorial Sundials'''] since the '''Dial''' must be parallel to the [https://en.wikipedia.org/wiki/Equator '''Equator'''].
			[[File:HorizontalSundial.png\|400px\|right]]


	=====Horizontal Sundial=====		=====Horizontal Sundial=====
	~~[[File:HorizontalSundial.png\|300px\|right]]~~

	[https://en.wikipedia.org/wiki/Sundial#Horizontal_sundials '''Horizontal Sundials'''] are perhaps the most common but many are purchased with little understanding of how to make them accurate.		[https://en.wikipedia.org/wiki/Sundial#Horizontal_sundials '''Horizontal Sundials'''] are perhaps the most common but many are purchased with little understanding of how to make them accurate.
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	=====Vertical Sundial=====		=====Vertical Sundial=====
	[[File:VerticalSundial.png\|~~300px~~\|right]]		[[File:VerticalSundial.png\|400px\|right]]

	'''Sundials''' can be designed such that the '''Dial''' is vertical and can be fixed to a wall but the [https://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] must still be positioned such that it remains parallel to the Earth's vertical axis ''(i.e. set at the angle of '''[[Latitude]]''' to the horizontal)''.		'''Sundials''' can be designed such that the '''Dial''' is vertical and can be fixed to a wall but the [https://en.wikipedia.org/wiki/Gnomon '''Gnomon'''] must still be positioned such that it remains parallel to the Earth's vertical axis ''(i.e. set at the angle of '''[[Latitude]]''' to the horizontal)''.