By Manasi Patil
Our home planet, the Earth, is a very unique one.
‘The third planet from the sun’ is the only world known to have the right conditions for life to flourish and what an amazing planet it has turned out to be!
If we jot down a planet profile of earth, it would somewhat look like this:
· Average distance from the sun: 150 million kilometers (93 million miles)
· Average surface temperature: 15 degrees Celsius (59 degrees Fahrenheit)
· Diameter: 12,760 kilometers (7930 miles)
· Length of day: 24 hours
· Length of year: 365.26 days
· Number of moons: 1
· Gravity at the surface: 9.8 m/s2
Now, let's get to know our home planet right from the start.
It is believed that everything in the solar system, including our Earth, was born inside a vast spinning cloud.
The story of earth began around 4.5 billion years ago, whereas our life on earth started about 3.8 billion years ago. Since then, living organisms have slowly transformed the planet’s surface, coloring the land green and adding oxygen to the atmosphere which makes the air breathable.
The Earth happens to be the largest of the four rocky planets and has the highest density of any planet in the solar system because its core is mainly made up of iron. If you could possibly pull apart the earth, you would discover that it’s made of distinct layers that fit together like layers of an onion.
The structure of the earth is divided into four major components: the crust, the mantle, the outer core, and the inner core. Each layer has a unique chemical composition, physical state, and can impact life on Earth's surface.
Even though the temperature at the inner core is 6000 degrees Celsius, it remains solid.
The outer core is made up of molten metal and the surrounding mantle is a thick layer of partly molten rock. Floating on top of this is a thin rocky skin called the crust.
The atmosphere surrounding earth is a blanket of gas mainly made up of Nitrogen (70%), Oxygen (21%) Argon (1%) which extends about 1000 kilometers (600 miles) into space. This composition of gases has remained unchanged for the last 200 million years.
It is thick near the ground and quickly becomes thinner as you move upwards.
The atmosphere protects us from harmful radiation and small incoming meteorites. It also provides us with our weather and helps keep earth warm. We know 5 atmospheric zones that extend up to space:
Troposphere
· Layer closest to the ground.
· Occurring of weather takes place here.
Stratosphere
· Contains the ozone layer.
Mesosphere
· Air is much thinner here, but it is enough to cause meteors to burn up on entry.
Thermosphere
· The beautiful auroras occur in this layer.
Exosphere
· Exosphere marks the uppermost limit of the atmosphere where most spacecraft orbit.
Earth is at just the right distance from the sun for liquid water to exist. Any closer and water would boil away like this scorching Venus, any further out and the planet would freeze, like the icy Mars. We all know that life can exist wherever there is water - without it life would cease to exist. Fortunately, earth’s oceans contain 1.36 billion km3 of water which is almost more than two thirds of the Earth’s surface.
The part of the solar system where conditions are suitable for life is known as the habitable zone. So far, Earth is the only planet found here. You might be surprised to know that life on Earth exists from the highest mountains to the deepest ocean trenches from- boiling hot springs to the interior of rock.
Nobody has conclusively discovered how life began; but some scientists think it may have started in the oceans since the land was very hot and the atmosphere was poisonous. Others think comets or meteors brought complex chemicals from outer space.
However, it began. And life has been existing ever since.
Simple molecules formed and began to copy themselves, eventually growing into cells and then colonies. Over time these evolved into more complicated organisms that began to populate the Earth’s surface. At various times during Earth’s history, many life forms have been wiped out. Some mass extinctions were probably caused by huge volcanic eruptions belching out clouds of gas and ash. These blocked out the sun causing the temperature to drop and killing many of the plants that animals needed for food. The extinction of dinosaurs 65 million years ago has been blamed on volcanic eruptions triggered by an asteroid impact.
If you've been lucky enough to enjoy the live view of Auroras you must have either been at the North or the South Pole. Because those are the only places where Aurora Borealis (Northern Lights) and Aurora Australis (Southern lights) appear in the night sky. The Auroras are caused when high energy particles from the sun pour through weak spots in Earth’s magnetic field colliding with atoms in the upper atmosphere and giving off light. Aren’t the Auroras a beautiful factor of our home, sweet home Earth?
We live our lives daily according to the Earth timetable. With a few exceptions, we get up and work in the day and go to sleep at night. The sun shining on Earth produces day and night. It also plays a role in creating the seasons. Because Earth is tilted as it spins, the period of daylight changes throughout the year, unless you live on the equator. The polar region experiences this to the extreme, with very long days in summer and very long nights in the winter.
North of the Arctic Circle and South of the Antarctic circle, the sun does not rise in Midwinter or set in Midsummer. Because of this, areas such as northern Norway and Alaska are known as the ‘land of the midnight sun.’
The earth rotates at a slight angle of 23.5 degrees like a spinning top that has been knocked slightly to one side. If earth were to spin upright, we would not have any seasons.
Here’s a fun fact: Most planets rotate at a tilt but if they lean too much the seasons can be very strange. For example, summers and winters on Uranus each last for 21 years!
Back to the topic, unless you live near the equator or the pool you will experience four seasons – Spring, Summer, Autumn and Winter. At the equator, the period of daylight hardly changes and the sun is high in the sky, so it is always warm. When the North Pole is tilted towards the sun, it is summer in the northern hemisphere and winter in the southern hemisphere. While the North Pole is tilted away from the sun, it is winter in the northern hemisphere and summer in the southern hemisphere.
Although the earth is covered by a rocky crust, it is far from stiff and static. The crust is divided into huge slabs called plates, which move very slowly around the Earth.
The surface is also changed by rivers, glaciers, wind and rain which help shape the world around us. The rocky plates that make up the crust float on Earth’s dense mantle. They move between 3 and 15 cm (1 and 6 inches) a year, changing the positions of the continents over time. Some plates move apart, others slide towards or past each other. Their movements build mountain ranges, and cause earthquakes, tidal waves and volcanic eruptions.
In recent centuries, our species has changed Earth’s surface so much that our influence is visible from space. As well as lighting up the planet’s nightside with electricity, we have changed the atmosphere and climate and have replaced large areas of natural ecosystems with farmland and cities.
Let’s just hope the change we are doing, results in something which is good for our home, the Earth, too.