Introduction to Geography

Introduction to Geography

• Geography encompasses everything: space, matter, energy, and time.
• It considers everything from the smallest atom to the largest galaxy.
• Eratosthenes coined the term "geography" from "geo" (earth) and "graphy" (study/description).
• Eratosthenes is known as the Father of Geography for his accurate calculation of Earth's circumference from 300 BC.
• Distances in the universe are measured in light-years.
• The diameter of the known universe is 93 billion light-years.
• One parsec equals 3.26 light years.

Light Year and Astronomical Units

• A light-year is the distance light travels in one year.
• Light speed is 300,000 km/second.
• One light year is 9.461 x 10^12 km.
• An astronomical unit (AU) is the average distance between Earth and the Sun (150 million kilometers).
• It is useful for measuring distances within our solar system, using Perihelion and Aphelion.
• Perihelion is when Earth is closest to the Sun (147 million km).
• Aphelion is when Earth is farthest from the Sun (152 million km).

Development of Geography as a Subject

• 1400-1800: map creation for sea travel during the Age of Discovery.
• 1800-1950: human geography study focusing on settlement, population, and culture.
• 1950-Present: Modernization through satellite utilization.

Eratosthenes' Calculation

• Eratosthenes calculated Earth’s circumference using the following:
• Distance between Alexandria and Syene (now Aswan) which is 800 km.
• The angle of the sun at Alexandria was 7.2 degrees.

Theories of Planetary Revolution

• In the Geocentric Model, Earth is at the center, with other celestial bodies orbiting it (proposed by Nicholas Copernicus).
• In the Heliocentric Model, the Sun is at the center, with other celestial bodies orbiting it (proposed by Thomas Ptolemy).

Big Bang Theory

• Georges Lemaître proposed the Big Bang Theory.
• The Big Bang Theory explains the origin of the universe approximately 13.8 billion years ago.
• This involved rapid expansion after an explosion of a tiny ball.
• Edwin Hubble's evidence in 1927 supported the Big Bang Theory with observations of an expanding universe.
• The universe's initial expansion rate was higher but has slowed due to cooling.
• The first atom formed within 3 minutes.
• The Milky Way was discovered after 500 million years.
• Planets formed 4 billion years after the Big Bang due to condensation.
• Red Shift is the distance expansion of galaxies in space, observed by Edwin Hubble.

Other Theories about Universe

• Steady State Theory posits a constantly expanding universe with new particles created to fill the void.
• Pulsating Theory suggests the universe expands and contracts due to gravity.

Composition of Universe

• Dark energy makes up 68% of the universe and drives its expansion.
• Dark matter interacts with gravity but neither emits nor absorbs light.

Birth and Evolution of Stars

• Stars are the building blocks of galaxies.
• Stars form from the combination of dust and gas.
• They are created by light gathering and clumping due to gravity, condensing into solid states.
• A nebula is a cloud of dust and gas where new stars are born.

Star Lifecycle

• Dust and gas from space combine.
• A protostar (newborn star) forms.
• A main sequence star is when hydrogen fuses into helium.
• Then a post-main sequence star produces a red giant or super red giant.
• A red giant transforms into a white dwarf and then a black dwarf.
• A super red giant becomes a supernova, then a neutron star or black hole.

Black Holes Explained

• Black holes have intense gravity, preventing even light from escaping.
• Black holes often are remainders of dead massive stars.
• The Event Horizon is the point of entry into a black hole.
• Galaxies are clusters of stars, dust, gas, natural satellites, and other astronomical bodies held together by gravity.

Types of Galaxies

• There are three major types of galaxies:
• Elliptical (oval shaped).
• Spiral (spiral arms) such as the Milky Way and Andromeda.
• Irregular (no defined shape).

The Solar System

• The solar system extends 100 astronomical units, containing everything orbiting the sun.
• The Solar System is approximately 4.6 billion years old.
• Terrestrial Planets: planets closest to the Sun, made of rock: Mercury, Venus, Earth, and Mars.
• Jovian Planets: gas giants, often very large: Jupiter, Saturn, Uranus, and Neptune.

Sun's Anatomy

• The sun, at the center of the solar system, is composed of hydrogen and helium gases.
• The sun is an important role to provide heat and light around the orbiting planets
• The core temperature is 15 million degrees Centigrade.
• The surface temperature is 6,000 degrees Centigrade.
• Layers:
• Inner Core (15 Million Degrees C)
• Radioactive Zone: fusing of hydrogen into helium releases massive heat that escapes via radioactive transfer
• Convectional Zone: radioactive bursts released here
• Sub Surface Zone: layer beneath the sun's surface
• Photosphere: regarded as the "surface"
• Chromosphere: atmosphere
• Corona: outermost "crown area" of the sun

Key Characteristics of Sun

• The Sun is the largest object in the solar system.
• It is 109 times Earth's size.
• The sun accounts for 99.8% of the solar system's mass.
• The sun is mainly composed of hydrogen and helium gas.
• It takes 225-300 million days to complete a full revolution around the galaxy.

Planetary Composition

• Terrestrial Planets: Small, dense, and rocky: Mercury, Venus, Earth, and Mars.
• Jovian Planets: Large and gaseous, labeled as Giants: Jupiter, Saturn, Uranus, Neptune.
• Relative sizes compared to Earth (1): Mercury (0.38), Venus (0.85), Mars (0.151).
• Jupiter's relative size is 11.

Understanding Planetary Rotation Differences

• Relative Rotation: Mercury (1), Venus near 1, Uranus (-1.4), Neptune (1.7).
• Distance: increases through the Solar System; Earth (1 AU), Mercury (0.38 AU).
• Density: Density order Earth (5), Mercury, Venus, then Gas Giants.

Planets and Revolution

• A light-year is defined as the distance traveled by an object in space in one year.

Exoplanets

• Exoplanets are planets outside our solar system.
• They are not bound to our sun but have their own planetary patterns.
• Over 5600 exoplanets have been observed.

The Kuiper Belt

• The Kuiper Belt is an area in space beyond Neptune containing many comets and asteroids.

The Oort Cloud

• The Oort Cloud is a theoretical cloud of icy objects far beyond the Kuiper Belt, considered the outermost boundary of our solar system.

Asteroids

• Asteroids are small minor planets that orbit the area beyond Mars and Jupiter.

Celestial Bodies

• These are smaller than asteroids that orbit space.
• Meteoroids orbit Earth and range from dust-sized to large asteroid-sized.
• Meteors are meteoroids that enter Earth's atmosphere, experiencing friction and temperature change.
• Meteorites are meteors that survive the journey to the ground

Comets Explained

• Comets are cosmic snowballs made of ice, gas, and dust.
• As a comet approaches the sun, it begins to vaporize and forms two tails.
• Comets comprise a solid mass (nucleus) made from a combination of organic gases and dust.
• The gas tail (ion tail) is formed from ionized gases, pointing away from the sun.
• The dust tail comprises dust and smoke that follows the orbit pattern.
• Ex: Halley's Comet, visible from Earth.

Latitude and Longitude

• Latitude: angular distance from the 0-degree Equator to the North and South Poles.
• All 360-degree circles are parallel to the Equator and never intersect.
• Longitude: angular distance between West and East, from pole to pole.
• Longitude lines (meridians) are not parallel and intersect.
• Distinguishing Facts:
• Latitude: Horizontal lines; indicate North and South direction.
• Longitude: Vertical lines; Indicate East and West direction. All pass through the center and are equal length.

Important Lines of Latitude

• 0 degrees: The Equator, equal distance between both poles.
• 23.5 degrees: Tropic of Cancer (Northern Hemisphere) and Tropic of Capricorn (Southern Hemisphere).
• 66.5 degrees: Arctic Circle and Antarctic Circle.
• Zones: Torrid, Temperate, and Frigid/Polar Zones.

Key Points of Longitude

• Longitude measures direction: East/West from the Prime Meridian.
• All meridians extend from pole to pole.
• The greatest distance between longitudes exists at the Equator (111.1 km), decreasing to zero at the poles.
• The 0-degree Prime Meridian divides the Earth into the Eastern and Western Hemispheres (Greenwich).

Importance of Time Zones with Longitude

• Each 15 degrees of longitude corresponds to 1 hour (every 1 degree goes through 4 minutes).
• Add time to the east and subtract to the west.
• There are 24 standard time zones in the world, each covering 15 degrees or 1 hour.
• The Prime Meridian passes through countries such as: United Kingdom, France, Spain, Algeria, Mali, Burkina Faso, Togo, and Ghana.

Indian Latitudinal Positioning Example

• The Tropic of Cancer passes through 8 Indian States, including: Gujarat, Rajasthan, MP, Chhattisgarh, Jharkhand, WB, Tripura, Mizoram.
• The Mahi River intersects the Tropic of Cancer twice in India.

Continental Drift Theory

• Proposed by Alfred Wegener in 1912, focusing on landmasses (continents).
• A supercontinent called Pangaea (all land), broke off into fragments.
• The remaining landmass was known as Panthalassa (all the water).
• Supporting Evidence:
• Matching Continental Shapes, like Africa and South America.
• Matching Plant and Animal Fossils across continents.
• Climate Evidence:
• Coal deposits in Antarctica suggest Pangea was once at an equatorial location with a tropical climate.
• Multiple regions shared climate patterns with the supercontinent.
• Plate Tectonics Theory was well accepted.
• Problem: The theory lacked an explanation of force.
• Suggested Forces:
• Earth Tides: The moon pulls the fragments. Rejected because the moon's gravity is insufficient.
• Earth's Rotation: Rotation causes fragments to move apart westward. Rejected due to scientific inconsistencies.

Convection Current Theory

• Emphasizes convectional electric elements at the Earth's center.
• Hot rocks rise and push down.
• New magma forms near subduction zones.

Seafloor Spreading

• Continental crusts are older compared to oceanic crust.
• The Sea Floor is spreading.
• Evidence:
• Rocks at ocean ridges are always younger.
• Paleomagnetism shows magnetic patterns in rocks.

Plate Tectonic Theory

• A plate is part of the Earth's crust composed of the Lithosphere solid rock.
• Plates are made of oceanic lithosphere and/or continental lithosphere.
• Plate Types:
• Major plates (7): Smaller Plates (20+).
• Examples: Pacific Plate, Antarctic Plate, Indo-Australian Plate.
• Plate Movement:
• Convergent Boundary: Two colliding plates.
• This area is prone to mountain building.
• Oceanic trenches will be very deep (e.g., Mariana Trench).
• Continental-Continental collisions are rare, their buoyancy resists subduction, leading to mountain formation.