How Old Is Our Planet Earth?
Age of the Earth
It is said that the moon, meteorites and the earth have formed all at the same time. Our moon is much smaller than the earth and has been inactive for billions of years. There’s an old sample form the Apollo lunar missions are approximately 4.6 billion years old. The fragments or rocks and /or metal of meteorites that have fallen to the earth are examined wherein found out that it ages in the 4.6 to 6.4 billion a year range. Therefore, it inferred that the earth have formed at about 4.55 billion years ago. It found out that the oldest terrestrial rocks is about 4 billion years old and the oldest rock on each continent is about between 3.6 to 3.9 billion years old.
Geology as a Discipline
Geology is a science that examines the earth, its form and composition and the changes it has undergone and is undergoing.
This science is divided into two big areas:
- Physical geology- it is the study of the materials composing the earth and the processes and phenomena that operates beneath and upon its surface.
- Historical geology- study the evolution of the earth
Astronomical studies about the earth
The first Greek to advocate a sun-centered or heliocentric universe
A Greek philosopher and mathematician who states that the earth rotates upon and axis and revolve around on its orbit.
- Cladius Ptolemy
An astronomer and mathematician of Alexandra who states that the center of the univers is the earth.
- Nicolaus Copernicus
A Polis astronomer who revived the heliocentric theory
- Tycho Brahe
A Danish astronomer who used to measure the location of heavenly bodies especially the earth.
Who discovered the use of the first astronomical telescope
- Johannes Kepler
Discovered the three fundamental laws of planetary motion
- Isaac Newton
Discovered the laws of gravitation and motion
Size and Shape of the Earth
A Greek mathematician and astronomer who calculated the size of the earth; he measured the distance between a deep well of Syne and Alexandra and the angle of the moon and sun in Alexandra on the first day of summer. He estimated that the circumference of the earth was about 43, 2oo kilometer.
- Isaac Newton
He proved that the circumference of the earth at the poles was less than the circumference of the equator. Then, as an analysis, it shows that the shape of the earth is an oblate spheroid.
Proofs that the Shape of the Earth is Spherical
The evidence gathered to prove that the earth has a spherical shape. The center of the earth from the poles is approximately 21.6 kilometers shorter than the distance from the center of the equator.
- Planes that go round showed that all flights were of equal distance.
- A ship receding farther and farther into the distance seems to sink gradually beneath the water level. This attributed the curvature of the sea surface.
- Earth during lunar eclipse reveals that its shadow on the moon is circular. Geometrically, a sphere is the only body that creates only a circular shadow. Therefore, earth’s shape is spherical.
- Photographs of the earth show the horizon as a curved line.
- Objects weigh the same everywhere; therefore earth is spherical in shape because of a slight variation in gravity.
Do you believe that we are in constant motion?
Motions of the Earth
Earth moves in two ways:
1. It spins around on its axis just like off the top. This spinning causes days and nights and makes one rotation in 24 hours. Days happen when a part of the earth is facing into the sun and night happens when part of it is out of reach of the sun’s rays. The earth spins toward east to west. Note: actually the true period of rotation of the earth is a little less than 24 hours, 4 minutes less, in fact, because it takes a little more than one rotation to its original position. We call this a sidereal day it is 24 minutes longer than a solar year.
2. The earth revolves around the sun. This revolution takes 365 and one fourth to end up in the same position, thus we call this as a solar year and it takes 366 days when it is only having 29 days in the month of February we call it as a leap year.
Structures and Composition of the Earth
- 30% of the earth’s crust is covered by land
- 70% is covered by water
- Oceans form one continuous mass of water
- The land is broken up into separate portions
- The big masses of land are called continents
- The small masses of land are called islands.
The Land Surface
It is characterized and covered by:
- Hills plateaus
- Large boulders
The Role of Water in Earth's Surface Processes
The Water Surface
- The ocean has an average depth of 3,800 meters.
- Marianas Trench is 11, 034 meters deep.
- Continent shelves- continents that covered by the sea that are flat terrace-like surfaces that slope gently toward the sea.
- Continental rises- is a deep sea floor wherein the widest plains and the largest mountain if the earth are being found.
- Seamounts- submerge mountain that have sharp peak while those flat tops are called guyots.
Layers of the Earth
- Crust- the thin shell of the earth. Also, it is the outermost compositional son of the earth composed mostly of relatively low density silicate minerals.
- Mantle- the zone of the earth’s interior between the crust and core and it's rich in ferromagnesium silicates. It has a depth of 2,880 kilometers beneath the earth’s crust. It accounts the 80% of the earth’s volume and 60% of the earth’s mass.
- Outer core- it is 2,240 kilometers thick. It's composed of iron and nickel in a hot plastic condition.
- Inner core- it is the hottest layer of the earth. This is more solid than the outer core.
Pieces of Evidences that the Earth Revolve Around the Sun
The appearance of each pattern of the star during the year was repeated from year to year. This proved that the earth moved in its orbit around the sun.
This is through the relationship effects of motion on light. When the light gets farther it appears reddish and when it’s getting nearer it appears bluish.
Seasons of the Earth
- Summer solstice- the earth axis is toward the sun that strikes in the Northern hemisphere, then days become warmer and longer in June 21.
- Winter solstice- after six months the earth axis is tilted away from the sun bringing up summer in the Southern hemisphere and winter to Northern hemisphere in December 21.
- Spring equinox- the lights of the sun are the equator, light and darkness in the Northern Hemisphere in March 21 or 22.
- Fall or Autumnal Equinox- the sun is directly strike above the equator in the Northern hemisphere in September 22 or 24.