Tag: Indian Astronomy

Quest for Salvation in the Wonders of Nature

TimeSeeds of Universe- 5

I remembered the live telecast of the Total Solar Eclipse in India in 1999, and the excitement of wanting to go out and watch the eclipse in Patna. However, we were not allowed to do so because we didn’t have the necessary protective gear. While we watched the live telecast from Srikakulam, we also noticed other people watching the eclipse from their windows, using makeshift gears.

The eclipse on June 21, 2020, was a special event, but I still didn’t have the protective gear to view it directly. It turned completely dark outside for a few seconds while we were watching the live telecast. My four-year-old daughter was amazed by the play of shadows and wanted a live demonstration of the story I had told her the previous night about the interaction between the Sun, Moon, and Earth. I was in complete awe of this natural wonder and wondered what it must have been like for ancient people who observed the changing sky, witnessed eclipses, and made calculations based on them.

Now, a big question loomed before me: How do Hindus acquire knowledge about upcoming eclipses and perform their associated rituals? How did they incorporate complex calculations into their timekeeping methods? There is evidence in texts, temple designs, and community practices spanning millennia, suggesting that the Hindu community possessed knowledge, awareness, and adaptability regarding eclipses.

The scientific causes of lunar and solar eclipses were well-known to ancient Hindu astronomers, even during the pre-Āryabhṭan period. Āryabhaṭa I (born 476 CE) clearly explained the causes of solar and lunar eclipses, stating, “Moon covers Sun in solar eclipse, and the great shadow (of the earth) eclipses Moon”

छादयति शशी सूर्यं शशिनं महती च भूच्छाया (Āryabhaṭīya 4.37.)

Varāhamihira (c. 505 CE) described the eclipse procedures in his Bṛhatsaṃhitā and dispelled irrational myths. He stated, “At a lunar eclipse, Moon enters the shadow of the earth, and at a solar eclipse, Moon covers Sun’s disc” .

भुच्छायाम स्वग्रणये भास्करम अर्काग्रहे प्रविष्टि इंदु (Bṛhatsaṃhitā, 5.8).

Across different parts of India, there are temples designed with astronomical mindfulness. Gavi Gangadhareshwara Temple in Bangalore, Konark Temple in Odisha, and Udaygiri Hills Temple in Madhya Pradesh have detailed inscriptions, symbols, and statues depicting astronomical events. Observational sites in hills and forests are scattered throughout the country. Archeo-astronomical sites and megalithic sites are hidden in various regions, such as the mushroom-shaped Kudakkal in Kerala, dolmen at Mallasandram in Tamil Nadu, and menhir at Nilaksal, Karnataka.

In the past two years, I have had the opportunity to visit some of these places. The experience feels like traveling through time, with those ancient marks engraved in stone. It fills me with wonder and respect for the curiosity of our ancestors in understanding nature. The pursuit of knowledge was a path to salvation—a true quest for salvation.

My quest for answers about eclipses and the knowledge possessed by ancient civilizations, particularly the ancient Hindus, has astonished me. They were able to estimate with significant precision the place, date, and time of solar and lunar eclipses. Calculating eclipses requires an understanding of the models of the solar system and the different motions of the Sun, Earth, and Moon, as well as the alignment of these bodies in time and space. It demands advanced mathematical tools and models to predict eclipses well in advance. How well-equipped were the ancient Hindus to make such predictions, taking into account the diverse motions of the Earth, Sun, and Moon?

Knowledge about eclipses was not limited to an elite group of scientists; awareness was widespread among the people. Elaborate rituals are associated with these astronomically fascinating events and have an unbroken tradition throughout the country. Even today, every community knows about the upcoming eclipse dates and times. Since childhood, I have heard about the standard rules for solar eclipses: not going outdoors, avoiding direct gaze at the Sun during the eclipse phase, abstaining from eating, and pregnant women avoiding exposure. These rules align with the safety guidelines suggested by modern scientists. Communities also practice rituals involving bathing, cleansing, and donation during lunar eclipses.

Who were these people with such a deep interest, profound observational abilities, and an awe-inspiring appreciation for the boundless wonders of nature? I am intrigued by how meticulously they wove reverence for these natural marvels into the community’s rituals, forging a connection between humans and the cosmos. I bow down to the great Rishis whose minds could decipher the language of nature. I feel as though I am being guided by an invisible hand into an entirely new realm—the realm of ancient Hindu science and the scientific accomplishments of other civilizations in the world.

Books:

• Science of the Ancient Hindus by Alok Kumar
• A History of Science in World cultures by Scott L. Montgomery and Alok Kumar
• The History of Indian Astronomy by K Ramasubramanian, Aniket Sule Mayank Vahia
  

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Time Seeds of Universe is a series on understanding time. ‘TimeSeeds of Universe: Quest for Salvation in the Wonders of Nature‘ is part 5 in this series. Following are the link to other blogs of this series : 

Time Seeds of Universe-1 : A Journey of Self-Discovery

Time Seeds of Universe- 2: It is about Reference Frame

Time Seeds of Universe- 3: A Sphere with Infinite Radius

Time Seeds of Universe- 4: Path, Light and Shadows

A Sphere with Infinite Radius

Time Seeds of Universe – 3

What is the perspective of the observer, and what is the reference frame of observation? Observing the sky from earth, the sky appears to be moving- Sun, Moon, Planets, and stars all appear to be moving in their own rhythm. Where are these objects and how are they moving? These objects are moving inside a celestial sphere, which represents our Earthling’s view of the universe.

Position on Earth

The observer’s position on Earth holds significance in the reference frame of observation. My position on Earth is defined by the coordinates of latitude and longitude. The timing of morning and evening, the length of day and night, the objects visible in the night sky, and even the temperature and rainfall in my location are all influenced by latitude and longitude. Before contemplating the vast sphere outside of Earth, it is important to firmly establish one’s position on the Earth’s surface and understand where they are located. In my case, I am situated in the northern hemisphere, above the Tropic of Cancer, but I also spend a significant amount of time in places close to the equator. My longitude is east of the Prime Meridian, and my hometown is even farther east, resulting in a significant time difference between these two places.

Understanding my location on Earth led to an interesting discovery about the length of shadows and zero shadow days. It reminded me of the childhood horror stories that ghosts do not have shadows, and one can quickly identify their presence when they appear! However, there are days when we live without our shadow (created by the Sun). Not all places on Earth have the luxury of witnessing zero shadow days; only latitudes between the Tropic of Cancer and the Tropic of Capricorn experience them. Alok Mandavagane has created a mobile app to help find zero shadow days on Earth. (Link: Find Zero Shadow Days app)

It was intriguing to revisit the arbitrariness of the current Prime Meridian, Greenwich, and recognise that geopolitical power dynamics play a critical role in standardising scientific concepts. Further exploration into the history of assigning meridians revealed a Pandora’s box of information. Indians had their own Prime Meridian at some point, located near the Tropic of Cancer, currently known as Ujjain. This topic deserves independent exploration.

A Sphere with Infinite Radius

Returning to the celestial sphere, imagine a colossal sphere surrounding the Earth, so vast that its radius is infinite! It encompasses everything that exists now, ever existed, or will ever exist, both manifested and unmanifested. All celestial objects moving in the sky have their own paths within this celestial sphere. The sphere is concentric with the Earth, and its pole and equatorial plane coincide with those of the Earth. We can describe the location of objects in the sky using celestial coordinates: declination (DEC) and right ascension (RA), which are equivalent to latitude and longitude on Earth, respectively.

Declination represents the angular distance of a point north or south of the Celestial Equator, ranging from +90°N to -90°N, similar to the latitude of the North and South Poles.

Celestial South Pole = -90° declination

Celestial Equator = 0° declination

Celestial North Pole = +90° declination

Right ascension measures the angular distance of an object measured eastward from the First Point of Aries (named after the Aries constellation), also known as the Vernal Equinox. RA is typically measured in hours, minutes, and seconds rather than degrees. Since the sky appears to turn 360° in 24 hours or 15° in one hour, an hour of RA corresponds to 15° of sky rotation.

Now, let’s transition from the large sphere to the big circle known as the ecliptic or ecliptic plane. The ecliptic represents the orbital plane of the Earth around the Sun, inclined at an angle of 23.4° from the celestial equator. The great circle marking the intersection of the celestial sphere with this ecliptic plane is where the Sun and planets appear to move in the sky. This great circle is also where the Sun and Moon cross paths during solar and lunar eclipses, which explains its name.

But what about eclipses? Drawing the large sphere helped me visualize the movement of various celestial objects in the sky, and learning about eclipses proved to be a surreal experience that left more questions unanswered than answered. I realized that relying solely on the internet was not enough for a comprehensive understanding.

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Time Seeds of Universe is a series on understanding time. ‘TimeSeeds of Universe: A Sphere with Infinite Radius‘ is part 3 in this series. Following are the link to other blogs of this series : 

Time Seeds of Universe- 1 : A Journey of Self-Discovery

Time Seeds of Universe- 2- It is about Reference Frame

Time Seeds of Universe- 4: Path, Light and Shadows

Time Seeds of Universe – 5: Quest for Salvation in the Wonders of Nature

A Journey of Self-Discovery

Time Seeds of Universe -1

Three years ago when life was imminently ephemeral, a hibernated desire to understand time scale of universe sprouted and started to grow. Life during those months of lockdown were full of anxiety and uncertainty. On the human’s time scale, I started on a journey to explore the universal time. To my own surprise, I could find an hour in the morning to study despite of pandemic induced cooking, household chores, a job and an inquisitive child at home. My exploration was all zig-zag with internet as the key source, referring to multiple sites at a time. Since I didn’t have a structure or a course, I listed down several questions for myself and started to search for their answers.

• How did human start tracking time?
• What were the methods and instruments ?
• What is basis for Ancient Civilisations’s calendar ?
• What is Solar, Lunar and Luni-Solar calendar systems?
• What was Ancient Hindu’s Calendar System?

Each of these questions led me to more questions and a complex maze of astronomy, history, archaeology, sociology, mindfulness and consciousness. Everyday morning, I would wake up to learn new definitions, meaning and awareness of the world around me. I was not well-equipped to understand a lot of the concepts because human history of time tracking is intrinsically linked to our understanding of celestial bodies, patterns of movement and various assumptions made at different phases. Before I could start the journey, I had to prepare with essentials of today’s astronomy to go back in time.

Earth’s orbit around the Sun

I started with fundaments – the high- school concepts of solar system. Earth rotates, ie., spins about its own axis in 24 hours. Earth revolves, has an orbital motion around Sun in 365 days. And a satellite revolves around a planet; our only moon takes 29.5 days to complete the revolution around earth.

Earth’s orbit around the Sun is an approximate ellipse and not a circle. But the more interesting part I had not studied in the school was the two body problem. Both the bodies revolve around the same focus in ellipse, the one closer to the more massive body. But when one body is significantly more massive, such as the Sun with respect to the Earth, the focus may be contained within the body of the larger mass. Thus the smaller body or the secondary body, Earth, is said to revolve around the larger body, the primary body. In an elliptical orbit, there are two foci or apsides– the farthest and the nearest point in the orbit of a planetary body. The line of apsides is the line connecting these two extreme values. For orbits about the Sun, the apsides are called aphelion (farthest) and perihelion (nearest). As if the two body problem is not interesting enough, there is a multi-body problem with a common centre of mass called the barycentre. Here, the actual motion of a body is perturbed due to the additional gravitational effects of the remaining body or bodies. If there is only one other significant body, then the perturbed motion is a three-body problem; if there are multiple other bodies, it is an n-body problem.

Imagine a system with multiple objects with different masses having different gravitational forces, affecting each other’s motion. Thankfully, for our solar system, the Sun is massive enough to be the barycenter of the solar system and make all other planets revolve around itself. The revolution or orbit of all the planets are nearly elliptical path. For an observer outside the solar system, (or with reference to the stars) Earth revolves in its orbit around the Sun in 365 days, 6 hours, 9 minutes, at a speed ranging from 29.29 to 30.29 km/s. Sun, too has its own path in the Milky Way, at a speed of 230km/s but its speed and path does not seems to be relevant for general human life on earth. We take the Sun granted for being there, always. Not that we think so much about Earth’s revolution but we see the Sun rising and setting that has kindled human’s curiosity to dig into this phenomenon.

Similar to earth’s orbit around Sun, the Moon’s path around the Earth is also elliptical. Moon revolves around earth in its orbit at a speed of 1.02km/s and takes about 27 days to complete the revolution. The point in the Moon’s orbit that is closest to the Earth is called the perigee and the point farthest from the Earth is known as the apogee.

Earth reaches its closest approach to the Sun, a perihelion of 147,090,000 km, on about January fourth of each year (about two weeks after the December Solstice). Aphelion comes six months later at 152,100,000 km in July (about two weeks after the June Solstice). Due to variations in the eccentricity of the Earth’s orbit, the dates when the Earth reaches its perihelion or aphelion are not fixed in one solar cycle. This path’s shape also varies due to the gravitational influences of other planetary objects.

The distance of Earth from the Sun and its timing appear a bit confusing because mind tends to assume that Earth should be at the farthest end from the Sun in December and closest to it in June. But what appears may not always be the truth!

I keep on looking at this beautiful Eyes on the Solar System created by NASA. With a click of a mouse, we can zoom in to the depth of Sun and zoom out of the Milky Way galaxy.

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Time Seeds of Universe is a series on understanding time. ‘Time Seeds of Universe : A Journey of Self-Discovery’ is part 1 in this series. Following are the link to other blogs of this series :

Time Seeds of Universe – 2: It is all about Reference Frame

Time Seeds of Universe – 3 : A Sphere with Infinite Radius

Time Seeds of Universe- 4: Path, Light and Shadows

Time Seeds of Universe – 5: Quest for Salvation in the Wonders of Nature

Image Credit:

Hiranyagarbha. The Cosmic Egg. Manaku of Guler. 1740. Bharat Kala Bhavan, Varanasi.

An 18th century Pahadi painting of Hiranyagarbha by Manaku