Parts of South America and the Caribbean will be plunged into darkness in a total eclipse of the sun on Thursday, February 26. It promises to be one of the most impressive eclipses in recent years.

The phenomenon begins at 1546 GMT in the Pacific ocean, 1,900 miles southeast of the Hawaiian islands.

A partial eclipse will also be seen in parts of the United States, eastern Canada and as far south as Brazil and Bolivia.

Simply put, an eclipse of the sun occurs when the moon crosses in front of the sun, blocking out all light for a few minutes.

Those enthusiasts who are keen to see the event but live in the wrong part of the world, can watch it on the Internet.

NASA has said it will show live images of the eclipse in a "webcast" from 1700 to 1900 GMT.

This is the last solar eclipse visible in the western hemisphere until the year 2017.

The hand of God

Dr Fred Espinak of NASA's Goddard Spaceflight Centre has witnessed more than 20 eclipses. He described what it is like to watch one:

"The total eclipse itself only lasts about three minutes or so, but the partial phases leading up to that total eclipse take about an hour and a half. It is a very gradual event, as the moon slowly moves across the sun's surface.

"During the last couple of minutes ... the sky starts getting dark, you notice the drop in the air temperature, very often birds come to roost into their nests, as though it is sunset. Even plants sometimes - flowers start to close up as if it is night time.

"During the last thirty seconds or so the sky rapidly drops in brightness, almost as though God himself has his hand on a huge rheostat and he is turning down the house lights.

"At that point, when you look back up at the sun, that blindingly bright crescent is replaced by a dazzling bead of sunlight, shining through the last valleys along the moons edge, as the sun's solar corona flashes into view and you are plunged into darkness," he said.

Path of the eclipse

The eclipse will first hit land in the Galapagos islands at 16.56 GMT. It will extend in a 93-mile (150km) wide band from the islands, over parts of northern South America and across the Caribbean Sea.

The longest period of darkness, which lasts a little over four minutes, will take place over the Pacific ocean, 400 miles west of Columbia.

At 1743 GMT, the eclipse first passes over South America and follows the border between Panama and Columbia. At this point those in the centre of the shadow cast by the moon will experience nearly four minutes of total darkness.

Next, the shadow crosses along the Andes into north-western Venezuela and into the Caribbean. The eclipse will encompass the islands of Aruba, Curacao, Montserrat, Antigua and Guadeloupe. Those watching here will be in the dark for just over three minutes.

The path of the eclipse continues over the sea and ends at about 600 miles west of Morocco. At this point the moon's shadow falls away from the earth and back into space.