In England we experienced a partial solar eclipse on Friday 20^th March 2015. The last full eclipse occurred in 1999 and the next partial eclipse we see will be in 2026. As a country we knew about it, we were expecting it, and we had been told what would happen. Imagine though what it must have been like to people in olden times to see their sun swallowed whole! Would the sun ever come back? Was the world coming to an end? Clearly many beliefs, fears and superstitions arose. So, we don’t experience the same fears these days, but just how much do we know about the wonder known as an eclipse?

What exactly is a Solar Eclipse?

A solar eclipse is a natural occurrence that we see when a new Moon moves directly between the Earth and our view of the Sun. In this way the Earth, Moon and Sun form a straight line. This is known as an occultation. The Moon’s shadow, divided into the dark umbra and lighter penumbra, can be seen on its journey across the Sun. This is quite a rare occurrence as the Earth, Sun and Moon have to be in perfect alignment. During the eclipse we see the Moon beginning to move across the Sun so that we see less and less of it and the light gradually dims. In a total eclipse this continues to happen until the entire Sun is blocked by the Moon for a few minutes and the sky becomes dark as night. The Moon takes about a month to circle the Earth, but we do not see an eclipse each month because the orbital planes of the Moon around the Sun differ from that of the Earth around the Sun. We will only see a solar eclipse when the Moon is directly in front of the Sun and the orbital planes intersect.

Different types of Eclipse

As we know, an eclipse is an astronomical event that occurs when one celestial body partially or totally covers another celestial object, but there are several kinds of Eclipse:

Total

In a total solar eclipse the Moon completely covers the Sun from our view on Earth dropping us into total darkness. An eclipse of this nature can only be seen from a relatively small area on Earth, one of around a hundred miles wide and about ten thousand miles long. Areas not in this area may be able to see a partial eclipse.

Partial

A partial solar eclipse, as we saw over England this year, occurs when the three celestial bodies do not align in an exact straight line. In this type of eclipse the Moon only partially covers the face of the Sun blocking only a section of it from our view.

Annular

The third kind of solar eclipse is known as an annular eclipse and occurs when the Moon looks smaller than the Sun when it passes across the centre of it. This happens when the Moon’s orbit is further away than usual. In this instance we can still see a bright ring of sunlight, or annulus, around the edges of the passing Moon.

Lunar eclipses

We also get to see lunar eclipses, total, partial and penumbral, when the Earth blocks the Sun’s rays from reaching the Moon. As the Moon does not have its own light it only shines because it reflects the Sun’s rays. Lunar eclipses only happen at Full Moon.

Why so rare?

 An eclipse is a rare occurrence and each year only between two and five will occur. For the UK there have only been eight total solar eclipses visible over the last five-hundred years! So, why do we not see a solar eclipse every new Moon? The reason for this lies in the tilt of the Moon’s orbit, approximately five degrees from the ecliptic. This results in the Moon usually travelling either too high or too low to block out the Sun’s light. The fact that we ever see eclipses is only because of a coincidence. The Sun is much bigger than the Moon, but also much further away. In this way they look close to the same size from our viewing point on Earth. We must have a full or new moon when the correct nodes line up, and this only happens on rare occasions. When conditions are favourable the smaller Moon appears to block our Sun giving us the amazing phenomenon known as an eclipse.

Royalty

 Throughout our history we have seen many accounts of eclipses being considered omens of evil for our royalty. The ancient Chinese took this so seriously that failure to predict eclipses could lead to the death of the astrologers! They considered eclipses to be linked to the success and health of their Emperors, so to not predict one and be unprepared for it was thought to put their Ruler in grave danger. The Babylonians concurred with this belief and took no chances. They went so far as to use substitute Kings during solar eclipses in order to swerve the ill luck away from their Ruler and perhaps from their astrologer’s heads too! The 1133AD eclipse in England became known as King Henry’s Eclipse as he died shortly afterwards which added to the belief of the ancients. King Richard III hated eclipses too, but for good reason. The death of his wife around 530 years ago coincided with one.

Religion

The Bible uses eclipses, both solar and lunar, in many of its verses. The strange phenomena happening in our heavens are seen to foretell future events. In the Gospels we are told the sky went dark during the crucifixion of Jesus, a sign of bad times to come. The ancient Greeks had similar beliefs, seeing an eclipse as a sign of their God’s anger and foretelling some kind of disaster. In ancient Hindu belief the serpent demons Ketu and Rahu were said to suck away the light of life. Rahu was beheaded by the supreme God Vishnu but his head still flew across the sky to swallow the Sun. The Prophet Muhammad’s son, Ibrahim, died at the time of the eclipse in 632 AD and this was seen as a sign from the Gods to mark his untimely death. Islamic scholars however say that Mohammad confirmed eclipses did not signify the birth or death of anyone. It is still a Hindu belief to bathe during eclipses in order to lead them to salvation from the cycle of life. This rare and unique solar phenomenon – the alignment of sun, moon and earth – is thought to generate curative properties in the holy waters of rivers and ponds.

Myth & Legend

 This rare phenomenon has been the subject of many myths and legends from ancient cultures right through to today. The belief tends to lean towards a bad omen, blacking out our world seen as a sign of evil and worrying times to come. This is understandable as having the life giving Sun taken away wouldn’t seem to predict anything fortuitous. Many believed the event signified the end of the world, a foretelling of doom. Various cultures see an eclipse as a time when demons or animals eat the Sun. To the Vikings it was eaten by wolves. In Vietnam the culprit was a giant frog or toad. It has been pointed out that the earliest word for eclipse in Chinese, shih, means “to eat.” On a more positive note, in Ancient Greece, a war was stopped thanks to an eclipse. It was understood by the armies to be a sign of peace. This is one of only a few positive beliefs to come from an eclipse!

Superstition

It is only natural that such an amazing event will have been the source of many superstitions throughout the years, many still paid heed to today. Some modern superstitions tell us that solar eclipses can be harmful to unborn children therefore they advise pregnant women to stay inside during the event. In India food cooked during an eclipse is believed to be at risk of poison so they fast until it is over. In some Asian countries it is still customary to greet eclipses with lots of noise. Banging pots and pans or lighting fireworks is commonly used to scare any potentially evil spirits away. During an eclipse even birds are said to stop singing due to their confusion over whether it is day or night! On a more positive note, in Italy some people say flowers planted during a solar eclipse will grow to be the brightest and most colourful of all.

Special Sights

 Baily’s Beads

Near the beginning and end of a total eclipse, the area of the Sun still visible around the passing Moon appears broken up into blobs of light These are known as ‘Baily’s beads’ after the British astronomer Francis Baily (1774-1844). We see them because the edge of the Moon is not smooth, but distorted by gaps in the mountains and valleys allowing light to pass through in only some areas.

Diamond Ring

As Baily’s beads as described above start to disappear, one last bead often remains for a few seconds longer. This final bead has been said to look like a diamond on the shining ring that surrounds the Moon.

The Sun’s chromosphere

Just for a few seconds after the diamond ring effect disappears we can briefly see the Sun’s chromosphere (sphere of colour). This consists of a narrow layer of red glowing tongues of gas flames leaping from the surface of the Sun.

The Sun’s corona

Only during a total eclipse, the Sun’s corona can be seen as a white halo around the black disk of the Moon. The light of the corona is made up of glowing atoms and the sunlight that shines off dust particles.

Shadow bands

For a short period of time on either side of totality, we might see weird bands of moving shadow racing across the ground, along the sides of buildings or across other light–coloured surfaces. These shadow bands are believed to be caused by irregular bending or refraction of the crescent sunlight by the Earth’s atmosphere.

 
Strange Facts

A total solar eclipse can happen somewhere on the Earth once every 1-2 years.

If the moon is too far away and too small to cover the sun’s ‘disk’ it causes an annular eclipse, leaving a ring of light.

The longest total solar eclipse can last up to 7.5 minutes.

Temperatures can dip by about 3 degrees during a solar eclipse.

The Moon travels at around 2,250 km (1,398 miles) per hour as it moves across the Sun.

The Sun’s diameter is around 400 times larger than the Moon’s; but the Sun is about 400 times further away from the Earth than the Moon – hence the exact overlap.

If any planets are in the sky at the time of a total solar eclipse, they can be seen as points of light.

Almost identical eclipses occur after 18 years and 11 days. This period of 223 synodic months is called a saros.

No more Eclipses?

We are likely to reach a time when we no longer see any total eclipses on earth, but not in any of our short lifetimes! The moon’s orbit tends to widen at a rate of about two centimetres per year moving it slowly further away from the Earth. Because of this movement, eventually the necessary celestial coincidences will no longer form total solar eclipses – in around 500 million years or so. This movement of the Moon is cause by the gravitational pull the Moon has over Earth. This pull, as we know, produces the tides we see in our oceans. Over time our oceans send a slight gravitational force back towards the Moon that results in a push away from the Earth and slows down the rotation of the Earth a little. In this way, in time the Moon will be too far away to cover the full face of the Sun any more.