Features Reporter
21 June 2001
Lusaka — There are two main types of eclipses: solar and lunar and they happen whenever the sun, moon and earth are in a straight line. Solar eclipse happens when the moon comes between the sun and the earth, so that the moon obscures the sun, either totally or partially. It can be so dark as to make it possible for some stars to be seen. When the moon is on the other side of the orbit, it will some times pass above or below the shadow of the Earth, so that we have a lunar eclipse.
What makes this solar eclipse so special?
This is the first time since June 21, 1982 that a solar eclipse has coincided with a winter solstice, the shortest day of the year. The sun is also at the peak of its 11-year activity cycle, which means that the corona (the pearly-white halo that forms the outer atmosphere and extends for millions of kilometres into space) will be completely round and very bright from the point of view of those witnessing a total eclipse.
What you will see today
The people of southern Africa will see the moon cross in front of the sun from left to right. The moon's shadow will be moving across the earth at a speed of about 3,200 km/h with a diameter of 150 kilometres and it will take about three hours for the shadow to move across the continent, ending in Australia.
What is the sun?
The sun is approximately five billion years old and is apparently the largest and brightest, and actually the smallest and faintest of naked-eye stars.
This illusion, of course arises from its comparative nearness of the next nearest star is in fact 300,000 times as far away from earth. The sun contains roughly 99.8 per cent of the total mass in the solar system and Jupiter, its largest planet, possesses the other two thirds of the rest.
It has a diameter of 1.4 million kilometres (100 times bigger than the earth's and 400 times than of the moon) and consists almost entirely of hydrogen and helium, with a core temperature of 15 million degrees Celsius and a surface temperature of 6,000 degrees Celsius.
Inside the core, a nuclear fusion turns 700 million tonnes of hydrogen into 695 million tonnes of helium and energy each second.
The energy travels from the core, through the radiative and convective zones, to the photosphere where it leaves the sun in the form of heat and light and other radiation, like X-rays.
Scientists project that in another five billion years, the hydrogen core will be exhausted and the sun will begin to expand as a red giant engulfing the inner planets.
On the photosphere there are relatively cool dark areas called sunspots, which usually appear in groups and are thought to be caused by magnetic fields.
Why such a great horde of scientists coming to view the eclipse from Zambia? Because it is only during a total eclipse that the inner parts of the sun, called the chromosphere and the corona can be seen. The outer parts of the sun can be seen with telescopes fitted with sun-blocking disks. Warning: The wonder sight could leave you sightless.
Looking at the sun with the naked eye, even for the briefest period, can result in the retina of the eye being burned, causing permanent eye damage. This is why your eyes instinctively water and close, effectively telling the brain to stop looking.
The sun is just as powerful when the moon is eclipsing it. So even if the view looks dim and you do not feel any discomfort, infrared rays will still be getting through and can cause irreparable damage to the eye.
The lenses of your eyes act as tiny magnifiers and if you look directly at the partial eclipse of the sun, the effect is the same as focusing sunlight through a magnifying glass on to grass or paper. The sun's rays will be focused intensely on your eyes and can burn them.
And because the retina has no pain receptors, you will not even feel it happening but it will happen if you ignore safe-viewing procedures.
HERE'S WHAT NOT TO DO WHEN VIEWING A SOLAR ECLIPSE
*Do not view the sun through regular or polaroid sunglasses as they provide no protection for this purpose.
*Do not use filters made of smoked glass, photographic film, photographic filters, gelatine filters, compact disks, big bags, coloured glass or any similar materials.
*Do not look at the sun through any optical instrument, such as a camera, binoculars, or telescope, even if you are wearing special filter viewers. *Do not experiment with or use any other filters unless you are absolutely certain they are safe.
If you are in the path of totality, you are witnessing a very special event. You may not be able to witness the same event from the same location for another 375 years!
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