Astronomy

What is an Eclipse



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I've been lucky enough to watch two total solar eclipses in my life. The first was in the 70's in Victoria, southern Australia. I was studying astronomy at the time, and our whole class was bussed to a good high vantage spot in the hills near Ballarat. The atmosphere was amazing as the sky darkened in the middle of the day. Birds fell silent, animals reduced their activity (and the students whooped and cheered). After the eclipse, as the false dawn arrived, the birds started their dawn chorus, roosters crowed, sheep bleated, dogs barked and the day began again.

The second solar eclpise I saw was in Britain, August 11th 1999. I remember the date because it was my mum's eightieth birthday, a doubly auspicious occasion for which the whole family had gathered from around the world.

An eclipse occurs when the moon, earth and sun are in a straight line.

When the earth moves between the sun and the moon, the shadow of the earth falls on the moon, creating a lunar eclipse. The moon must always be a full moon for this to occur. Wherever we are on earth it looks about the same. It is completely safe to look at a lunar eclipse with the naked eye.

Solar eclipses happen when the moon comes between the sun and the earth. Total solar eclipses are rare and must not be viewed with the naked eye as, although the sun is obscured, it is still possible for radiation from it solar flares to damage the eye especially at the "diamond ring" stage when the sun starts to emerge and a bright flash of light is seen. The moon is a new moon when solar eclipses occur. There are simple devices which can be made to watch the eclipse indirectly, even by using a pinhole in a shoebox. I made a safe device for my children to view the solar eclipse and even our pet donkey wandered over for a viewing.



Total solar eclipses may only be observed from one small section of the earth and on either side of that section there is a partial eclipse.

Transits involve the movement of smaller bodies, eg the planets Mercury and Venus, across the disk of the sun. They eclipse only a very small area and, again, must never be viewed directly. The transit of Venus was famously observed by James Cook in 1769, as a means of measuring the solar system.

Eclipses still hold us in awe as they did our ancestors, though we now know they are just shadows and don't have any great significance for our well being.

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