Introduction to Geography

Geology is the study of the Earth. There are no real laws in geology because most of the processes, events, and sundry items attached to geology don’t work in all situations at all times. For example, the “Law of Superimposition” in Geology says that rock layers on the bottom are the oldest, while those on the top were formed more recently. But this law is not true in case of the mountain formation in which the rock layers fold over, resulting in older layers lying on top of younger layers.

One of the key principles in Geology is Uniformitarianism. This doctrine is based upon the assumption that the same natural laws and processes that operate in the universe now, have always operated in the universe in the past and apply everywhere in the universe. It has included the gradualistic concept that “the present is the key to the past” and is functioning at the same rates. Uniformitarianism has been a key principle of not only geology but virtually all fields of science, but in case of the Geology, the modern scientists don’t hold it correct any more. They say that the Geologic processes may have been active at different rates in the past that humans have not observed.

The most basic query of the Geology has been on how the earth was formed and how the surface features on earth have developed. It will not be out of the context to discuss about the three camps which have three different theories in Geology, which are now obsolete.

Neptunism

Neptunism was given by German scientist Abraham Werner. It held that the world was once all oceans, and that the rocks of the Earth’s crust, including basalt and granite, seen today were precipitated out of the ocean. The theory was rebutted.

Catastrophism

This doctrine says that most geologic formations were created by sudden, violent, catastrophic events, such as earthquakes, floods, asteroids strikes, and volcanoes. It has been discarded because now it has been accepted that Earth’s features are formed by slow natural processes that, at times, are punctuated by certain catastrophic events.

Plutonism / Vulcanism

Theory was put forward by Scottish geologist James Hutton. It says that the rocks forming the Earth were formed in fire by volcanic activity, with a continuing gradual process of weathering and erosion wearing away rocks, which were then deposited on the sea bed, re-formed into layers of sedimentary rock by heat and pressure, and raised again. It proposed that basalt was solidified molten magma. They theory was named after Pluto, the classical ruler of the underworld, or alternatively after Vulcan, the ancient Roman god of fire and volcanoes.

Earth: Observations of the Early Philosophers

In the beginning of the civilization, Earth was believed to be the center of the universe, which consisted only of those planets visible with the naked eye and an outlying sphere of fixed stars. This was called the Geocentric Model.

In those times, we even did not know that Earth was round. For example, Thales, who is considered to be the Earliest Geographer, proposed that world was a flat disc based on water, and that all things grew out of it. His disciple Anaximander, who is known to have first attempted to create a scale map of the known world said that Earth has shape is that of a cylinder with a height one-third of its diameter and flat top forms the inhabited world, which is surrounded by a circular oceanic mass. Such was the knowledge about Earth to the early geographers.

Around five centuries before Christ, it was probably Pythagoras, who proposed a spherical world. Pythagoras was so much convinced with the goodness of “being round” that argued that a sphere is a most perfect form. The idea of a spherical earth was embraced by Plato and Aristotle too. Earth’s shadow during an eclipse is curved, and also that stars increase in height as one moves north, these were some of the observations of Pythagoras, which helped the human beings know about the round shape of earth. Pythagoras had also probably proposed that the Earth rotates.

The next important query of the Greeks was about the size of the Earth. Eratosthenes attempted to calculate its circumference by measuring the angle of the sun at two different locations. Eratosthenes is known to be the first person to use the word “geography” and invented the discipline of geography as we understand it as Today. A system called “latitude and longitude” was also invented by Eratosthenes. These were some of the reason why the westerners call Eratosthenes as “father of geography”. Indeed, he was the first person to use the term “geography” itself.

Apart from the observations of the Greek Philosophers, it would be important here to discuss what Indians knew and observed about the Earth and universe. Astronomy is as old as Veda themselves are. The Atharva Samhita has a list of 27 nakshatras. Nakshtra Vidya was mentioned on Chadogyapnishad at several places. The earliest well defined Indian astronomical work is Vedanga Jyotisha of Lagadha, which has not yet been conclusively dated. Post Jyotisha Vedanga, all Indian astronomical texts are dated to the sixth century AD or later with a high degree of certainty. The modern scientists are in favour of as well as against the originality and independent development of Indian astronomy. We have lost many of the important primary sources on which we can prove the superiority of our knowledge.

The most important observations about Earth are of Aryabhatta.

The first observation of Aryabhatta was that “earth rotates about its axis daily”. He also writes that it is the apparent (probably) movement of the starts is due to the motion of Earth. This was in contrast with what was generally believed that the sky itself rotates. However, still, there was a Geocentric Model of Universe. The model of the universe given by Aryabhatta was more clearly a Geocentric Model and less clearly, it has been claimed to be heliocentric model. In the Paitāmahasiddhānta, it has been documented by Aryabhatta that the motions of the planets are each governed by two epicycles, a smaller manda (slow) and a larger shighra (Fast). The order of the planets in terms of distance from earth, as in Aryabhata’s model is Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, and the asterisms. Aryabhatta is known to have calculated the sidereal rotation and sidereal year at almost correct value. Solar and lunar eclipses were scientifically explained by Aryabhatta. He writes in Golapada that the lunar eclipse occurs when the moon enters into the Earth’s shadow. Not only this, he calculated the size of earth’s shadow and correlated it correctly with the duration of the eclipse.

The heliocentric model of Earth was accepted in the 17th century. Nicolaus Copernicus was the first to develop a mathematically predictive heliocentric system, thus he is generally known to have discovered the solar system. ^{(But it is incorrect to credit one person for discovery of solar system)}. He said that Earth was a planet orbiting the Sun, and that all planets moved in circles, one inside the other. Mercury and Venus had the smallest circles, smaller than that of the Earth, and that is the reason is that their position in the sky was always near the Sun’s. Indeed it was a daring voice in those times. It denied century’s old belief that Earth was the center of the universe. However, Copernicus was not even able to fully describe the motion of the planets. Some corrections were still needed.

His successor Galileo Galilei, the Italian scholar was the first to observe the planets through a telescope, and what he saw convinced him that Copernicus was right. However, his aggressive defense of the Copernican theory turned the Catholic Church against him and cost him his freedom. The Catholic Church issued a decree against him for declaring that Sun stood still and that the Earth moved was “false” and “altogether contrary to Holy Scripture”. They forced him to “correct” his theory. He was put under house arrest and made to face a lot of problems. Out of pressure, he is said to have agreed to what pleased the Catholic Church but is also believed to rebelliously have muttered “Eppur si muove” means “And Yes it moves“.

Some more 17^th century physicists such as Johannes Kepler and Isaac Newton developed an understanding of physics that led to the gradual acceptance of the idea that the Earth moves around the Sun and that the planets are governed by the same physical laws that governed the Earth. Then, the invention of the telescope led to the discovery of further planets and moons. Improvements in the telescope and the use of unmanned spacecraft have enabled the investigation of geological phenomena such as mountains and craters, and seasonal meteorological phenomena such as clouds, dust storms and ice caps on the other planets.