A total eclipse of the Sun will be visible from parts of the United States on Monday 21 August 2017, with a partial eclipse visible from the rest of North and Central America, as well as the Islands of the Caribbean, Colombia, Ecuador, Venezuela, Guyana, Suriname, French Guiana, Iceland, Ireland, Scotland, southern Scandinavia and parts of Brazil, Peru and Bolivia and (briefly) England, western Iberia, parts of West Africa and northwest Brazil.
The
path of the 21 August 2017 Solar Eclipse. The total eclipse will be
visible along the central dark grey path. A partial eclipse will be
visible from the shaded areas; in the lighters area the full eclipse
will not be visible as it will have started before dawn (west) or will
continue after sunset (east). The red lines are the Equator and the
Greenwich Meridian. HM Nautical Almanac Office.
Eclipses
are a product of the way the Earth, Moon and Sun move about
one-another. The Moon orbits the Earth every 28 days, while the Earth
orbits the Sun every 365 days, and because the two Sun and Moon appear
roughly the same size when seen from Earth, it is quite possible for the
Moon to block out the light of the Sun. At first sight this would seem
likely to happen every month at the New Moon, when the Moon is on the
same side of the Earth as the Sun, and therefore invisible (the Moon
produced no light of its own, when we see the Moon we are seeing
reflected sunlight, but this can only happen when we can see parts of
the Moon illuminated by the Sun).
The relative positions of the Sun, Moon and Earth during a Solar eclipse. Starry Night.
However
the Moon does not orbit in quite the same plane as the Earth orbits the
Sun, so the Eclipses only occur when the two orbital planes cross
one-another; this typically happens two or three times a year, and
always at the New Moon. During Total Eclipses the Moon entirely blocks
the light of the Sun, however most Eclipses are Partial, the Moon only
partially blocks the light of the Sun.
How the differing inclinations of the Earth and Moon's orbits prevent us having an eclipse every 28 days. Starry Skies.
Although the light of the Sun is reduced during an Eclipse, it is still extremely dangerous to look directly at the Sun, and viewing eclipses should not be undertaken without appropriate equipment.
Animation showing the shadow of the Moon at five minute intervals on Friday 20 March 2015. Andrew Sinclair/HM Nautical Almanac.
See also...
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