This is a story from a time long long ago!
It was a beautiful day and it started off just like any other day. The men and women went about their work, trying to complete them before the sun went down. The sky was blue and the sun was shining brightly in the sky. It was almost noon. Suddenly, the sky started turning dark. It felt like dusk came in early that day. The sun looked as if someone had taken a giant bite of it and kept taking more bites. Birds started flying back to their nest and the cattle grew restless. And in a matter of minutes, there was no sun. It was dark as night. There was no moon as it was a new moon day. But the stars were visible and the haze of the milky way could be seen.
'What has happened? Where did the sun go? Did something eat the sun? What would we do without its light and warmth? How can we live?', questions were forming thick and fast in the minds of the people witnessing the spectacle. The end of the world was even predicted. It took just a few minutes for the sun to slowly emerge back and soon enough it was shining brightly as if nothing happened. Unsure of what just happened, people returned to what they were doing.
The story tellers of the tribe took upon themselves to record the event. They concocted a story that a huge snake managed to eat the sun and the sun somehow escaped and came back. But why did the snake eat the sun? Where did it come from? They had to add a back story for it all to make sense. They added this as another chapter in their mythology.
There were two groups of supreme beings, the Devas and the Asuras, that fought with each other for the ultimate glory. The battle was draining their power and they decided to collaborate to get Amrit, the divine nectar, that would give them immortality. They agreed to work together to obtain it and to share it equally between themselves. This needed a churning of the milky ocean on which God rested. They needed a butter churn of enormous proportion and a rope of equally enormous size to start the work. They used a mountain called Mount Meru as the churn and a gigantic snake called Vasuki as the rope. And to hold the mountain in place, they prayed to Lord Vishnu, who turned himself into an enormous tortoise and held the mountain on its back.
The churning of the ocean is a big story in itself and is for a later time. Let us just see what happened.
Amrit was obtained. The warring Devas and Asuras started fighting over the way it should be shared and before it turned into a full fledged fight, they once again prayed to Lord Vishnu, who this time took the form of a beautiful damsel, Mohini, and accepted the responsibility of sharing Amrit. In a secret move, the Devas appealed to Vishnu that the Asuras would bring a reign of terror upon the world and so only they should be given the gift of immortality. The Lord agreed to their request and said they would get the Amrit first and it would run out by the time the turn of the Asuras came. According to the plan, Mohini started doling out Amrit to the Devas first.
Amongst the Asuras was a powerful Asura king called Swarabhanu. He sensed something was amiss and did not want to miss his share of Amrit. He transformed himself to look like a Deva and sat with the Devas. The Sun and the Moon saw the transformation and tried to warn Mohini. But before she realized, Swarabhanu got his share and consumed it. Once Mohini realized what had happened, she flew into a rage and beheaded Swarabhanu with the very ladle with which she was serving. But because, Swarabhanu had already consumed Amrit, he did not die.
It was decided that a snake would be killed and its head would be placed on Swarabhanu's body and his head would be joined with the snake's body. As a punishment for what he did, the two pieces were dispatched to opposite ends of the space and were destined to remain apart for eternity. The two parts were called Rahu and Ketu. Swarabhanu was angry at Sun and Moon for having snitched on him and got a boon that if they come near him, he would swallow them. The boon was granted with a rider. As there would be no life without the Sun and the Moon, they would escape after a few minutes.
The swallowing of the Sun or the Moon is what a Solar or Lunar eclipse is. The belief is that the period of the eclipse is charged with negative energy. People were advised to remain indoors, not eat or drink at that time, and pregnant women should take extra care to shield themselves indoors. Even the temples were to remain closed for that duration.
This story is from Hindu mythology. But other civilizations had their own stories about eclipse and many of them are similar. The sun or the moon being swallowed by a snake, or a dragon, or even a frog is a recurring theme. Half a world across from India, in present day America, the Navajo nation people also believe eclipses to be times of negative energy and refrain from going out or consuming food and drink at that time. Just goes to show the working of the human mind is similar irrespective of all differences.
That is mythology. But what does science tell us?
The earth goes around the sun in an elliptical orbit. So does the moon around the earth. During their orbits, if the three bodies line up, an eclipse happens. If the moon comes in between the sun and the earth, it is a solar eclipse as the sun is hidden by the moon for the people on earth. If earth comes in between the sun and the moon, the rays of the sun are blocked by earth and there is no light for the moon to reflect. So the moon disappears and that is a lunar eclipse.
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| PC - Illustration by S. Larson, from the internet |
But the sun is much bigger than the moon. How is the moon able to block the sun out? It is another quirk in how the earth is placed in just the right place in the universe. The sun is approximately four hundred times the size of the moon but the distance between the sun and earth is about the same four hundred times that of the distance from the earth and the moon. So when they line up perfectly the moon is just the right size to block the sun out completely.
Imagine you holding up a finger to your eye and looking at a building in front of you. Your finger will block the building because of its relative distance from your eye even though it is much smaller than the building. The idea of the moon blocking the sun is similar to that.
The moon orbits the earth along an elliptical path. Therefore, the distance between the moon and the earth varies. If a solar eclipse happens when moon is closer to the earth, the moon blocks out the sun completely. The day gets dark and the stars become visible. This is called a Total Solar Eclipse. As the eclipse starts to end, just a point of the sunlight peeks out and causes a brilliant spectacle. It looks like a diamond ring in the sky.
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| Total Eclipse - PC nasa.com |
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| Diamond Ring - PC esa.int |
In the example above, if the finger is moved a bit away from the eye, the building will be still blocked but the outermost parts of the building would be visible. Similar to that, if the solar eclipse happens when the moon is furthest from the earth, the size of the moon is seen as slightly smaller than when it was at the closest point. The moon does not block the sun completely and this results in a ring of sunlight visible around the moon. This bright ring of sunlight is called the Ring of Fire. This type of eclipse is called Annular Eclipse.
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| Ring of Fire - PC Jeff Cohen |
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| Another view of the Annular Eclipse - PC Jeff Cohen |
The illustration below explains how the Total and Annular eclipses occur due the distance of the moon from the earth and the resultant view of the sun.
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| PC - Illustration by S. Larson, from the internet |
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| Total Eclipse vs Annular Eclipse |
There is one other type of eclipse called the Partial Solar Eclipse. This occurs in the area where the Penumbra, or the dissipated shadow of the moon falls. In this case, the moon does not completely block out the sun but blocks only a portion of it resulting in the earth getting a crescent view of the sun.
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| PC - researchgate.net |
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| Crescent Sun - PC Marco Rutiaga |
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| Look at the sun spots - PC Brett Spangler |
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| The various phases of the eclipse - PC Srinivas Patil |
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| A stack of various sun phases - PC Adam Mendel |
If those are the views for the earthbound, how does it look for the astronauts in the orbit? Their view is something very different and spectacular. They will see the shadow of the moon traveling across the surface of the earth.
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| View from ISS - PC Bloomberg.com |
There was a solar eclipse last Saturday, October 14th, 2023. This was a partial eclipse in Austin, where I live. But if I were to drive a hundred miles from Austin, I would be in an area where the eclipse would be an annular eclipse. My son, an astronomy student and I decided to take the trip to witness the ring of fire. We chose to go to a town called Kerrville as there was a watch party organized by NASA there.
The city worked with NASA in putting up a grand show. It was a show that looked, sounded, and smelled like a typical Texas State Fair. There were all kinds of activities such as fairground games, snacks and drinks, vendors selling merchandise and what not. NASA had a big pavilion and its staff fielded questions from the public, explained the science behind the eclipse and gave out posters badges and informational flyers. There was representation from other groups such as the Astronomy Society of Texas State College as well. They had set up a couple of telescopes that enabled us see the eclipse up close. It was a grand affair and we were happy to witness this event in person.
Following this annular eclipse, there is a total eclipse visible to the people of Texas among others this coming April 8th. While we could see that from our backyards, this trip has inspired us to look for places where the total eclipse would be the longest and plan a trip there. After that eclipse the next visible one in America would be only in the year 2044. So these are truly events of a lifetime.
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| Path of the latest and the next eclipses - PC nasa.com |
Finally, there is one other thing we should talk about. These are the Lunar nodes. While it is the earth that orbits the sun, to us it looks like the sun is moving around the sky. The path it takes is called the apparent path of the sun. This is the elliptic plane. The orbit of the moon crosses this apparent path of the sun in two places. These are called the ascending and descending lunar nodes. They are also called the Northern and Southern Lunar nodes. Eclipses occur only when the three bodies line up in the vicinity of these lunar nodes.
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| Lunar Nodes - PC eclipsegeeks.com |
In Indian Astrology, the names for these lunar nodes are the same Rahu and Ketu, the torn bits of the Asura Swarabanu, that gobble up the sun and the moon!
Some relevant links
1. NASA live from Kerrville - https://www.youtube.com/live/LlY79zjud-Q?si=P5w8XxL-uOowQ25R
2. Documentary on Native Indian beliefs about eclipse - https://vimeo.com/230453732
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