Eclipse - All you ever wanted to know about eclipses and other celstial bodies

Geometry of a Solar Eclipse


Information of the Physical attributes of a Solar Eclipse

Total Solar Eclipse information

Physical attributes of a Solar Eclipse

A Solar eclipse can only occur when there is a New Moon and only when the Earth, Moon and Sun are in perfect alignment or near perfect alignment. The Moon passes between the Earth and the Sun, and the Moon fully covers the Sun, blocking sunlight reaching Earth's surface and turns daytime into darkness, while still allowing observers to view the beautiful corona atmosphere of the Sun.


Solar Eclipses occur during daytime when the New Moon is in the daytime sky and moves across the sky but is invisible due to the glare of the Sun and only becomes visible when the eclipse begins. As the Moon continues moving across the daytime sky it makes 1st contact against the Sun. This is the beginning of the eclipse. Totality occurs when the Moon completely covers the Sun turning daylight into darkness and allowing observers to view the beautiful corona atmosphere of the Sun.


Anatomy of a Solar Eclipse



The Moon passes in front of the Sun blocking sunlight reaching Earth. The penumbra shadow of the Moon (the outer fainter shadow) falls onto Earths daytime surface and a partial solar eclipse is observable.


Under the Umbra shadow a Total Solar Eclipse is seen and makes a shadow of darkness along a narrow path. This shadow width varies according to one’s local and geographical conditions but is typically 140 miles wide by 6,0000 miles long.


To observers outside the area of totality a partial eclipse of varying degrees is seen. The narrow path of Totality results in only a minority of people being able to observe the event. A Total Solar Eclipse duration lasts between a few seconds and a few minutes.

Anatomy-image-diagram-Total-Solar-Eclipse-Geeks Moon-photo-image-NASA-Total-Solar-Eclipse-Geeks -

A New Moon rises in the east approximately the same time as Sunrise and sets in the west approximately the same time as Sunset. The Moon travelling across the sky in Earth's daylight hours (invisible due to the glare of the Sun) and only reveals itself during a solar eclipse when it covers our Star the Sun as in the picture on the left.

Photo. A Total Solar Eclipse. The silhouette of the Moon obscures the intense bright light of the Sun allowing the faint whispery corona to be viewed.

Diagram showing the penumbra and umbra shadow areas

The penumbra is the region of the moons outer shadow where a partial eclipse of the sun occurs. The amount the Sun is eclipsed falls away greatly the further an observer is from the centre line of totality. Observers on the outer rim of the penumbra would only see the Sun 1% eclipsed and those outside would see no eclipse at all.



Baily’s Beads


Just before the Moon has nearly blocked out the sun during the last few moments before totality, observers can see points and beads of light surrounding the edges of the Moon. They look like a string of luminous beads of light wrapped around the edges of the Moon and is the last string of light before darkness falls. They are appropriately named after the British astronomer Francis Baily (1774-1844) who first provided an exact explanation of the phenomenon in 1836 and who was one of the founders of the Royal Astronomical Society. Baily's Beads are caused by light shining through the rugged topography of the lunar limb where the edge of the Moon, with its valleys and mountains, allows beads of sunlight to shine through in some places but not in others.


Beautiful Darkness Descends


When the Moon completely obscures the Sun, daytime turns into darkness. The darkness is different to the darkness of night-time but is more like a dreamy soft darkness of magic. Street lamps switch on, and if the eclipse is on the coast, you can look across the dark bay and see the hum of distant neon lights, all one by one, light up. Birds stop flying and animals prepare to sleep, while others are completely confused. Often before the Total Eclipse the wind picks up and the breeze gets quite strong - then at the moment of totality the wind stops dead in its tracks, as through someone had switched-off a cooling fan. During the moments before totality the temperature gradually drops and it often feels cooler, then at the very moment of totality the temperature drops dramatically and is very noticeable, it can drop instantly by as much as 20c. There is stillness and complete quite, people begin to gasp at the wonder of it all and it is a truly an amazing sight.  To actually be at and see a Total Solar Eclipse is one of the most amazing natural events a human can ever see. Watching and being part of the event is a wonderful and miraculous experience.    

Planets and Stars Become Visible


Once the beautiful Baily's Beads have faded and the Sun is totally eclipsed another wonderful sight comes into view, the glow of the Solar Corona,

the only time the Sun can be safely viewed directly. Some of the brighter Stars and Planets may become visible and with no birds and bees flying,

the still air, the big drop in temperature and daytime turned into night, the Earth becomes strangely quite.    



A Total Solar Eclipse, a three minute preview from the BBC TV series 'Wonder of the Solar System' presented by professor Brian Cox showing the Wonder of a Solar Eclipse Varanasi India