Earth, our home and the only confirmed planet supporting life

Earth is our home, the only planet that we know of supporting life.  Earth is the third planet from the sun and the fifth largest planet in the solar system. It is the largest of the terrestrial planets (Inner or rocky Planets) consisting of Mercury, Venus, Earth and Mars. The earth is approximately 150 million kilometers (93 million miles) from the sun and astronomers have defined this distance to be 1 astronomical unit. Sunlight travels about 8 minutes before reaching the Earth.

Earth

Earth. Image credit space.com.

Why Is Earth an Interesting Planet?

The most interesting Earth fact may not seem so interesting or unique to us because we are used to it. What makes Earth unique and interesting is that life thrives all over in this planet. There are plants, animals, birds, sea creatures and all kinds of species. There is no other known planet that supports life.

For a very long time, scientists have been fascinated by Earth trying to find out what makes it ideal for life. The first theory is that it is located in the habitable zone, the area in the solar system that is just at the right distance from the sun for water to exist in liquid form and where conditions are just optimal for life to exist.

Scientists are exploring this zone to find out whether there are extra solar planets that may be able to support life. There are many more interesting facts about our Earth as explained below.

The Origin of the Name Earth

Unlike the other planets that were named after gods in Roman and Greek mythology, the Earth got its name from an Anglos-Saxon word erda, which means ground or soil. It has also been nicknamed Blue Planet and Terra.

Ancient cultures may have had different names for it. The Mayans believed the earth was flat with a jaguar at each corner holding up the sky. Ancient Greeks believed Gaea gave birth to the universe.

What If Earth’s Water Were Gathered In One Place?

According to a US Geological Survey, if all the water on Earth from fresh, sea and ground water, water vapor and even water inside living things were collected together in one place, it would make a giant sphere of liquid 860 miles (1,385 km) in diameter, which is less than a third of the size of the moon.

 

All Earth's water, liquid fresh water, and water in lakes and rivers

All Earth’s water, liquid fresh water, and water in lakes and rivers. Image credit ga.water.usgs.gov

The Earth’s Gravity Varies

Earth’s gravity is not the same everywhere. It varies with location. For example, you would weigh 0.5% more around the poles than you would weigh at the equator.

This difference in gravity is attributed to the bulge at the equator and the rotation of the Earth. Since gravity depends on the distance from the center of the earth and different places on earth have varying distance from its core, it follows that the gravity also varies.

Earth’s Oceans Are a Goldmine

Earth’s oceans occupy 71% of its surface. These oceans contain very interesting features. So far, we have managed to explore only 10% of the oceans. Scientists believe there is about 20 million tons of Gold in the oceans. The largest single feature on earth is the great mountain range formed by the ocean ridges.

The Earth’s Atmosphere Is in Layers

The Earth’s atmosphere is divided into layers. The higher you climb, the thinner the atmosphere becomes. The layer closest to the surface is known as the troposphere and it accounts for 75% of the total mass of the atmosphere. The weather occurs in this layer. The outermost layer is the exosphere. Here, the air is too thin to support life.

There is no defined boundary between the earth’s atmosphere and space. The air gets thinner the higher you go until there is no more air. Scientists have calculated that space begins at an altitude of 100km. This level is known as the Karman line. If you travel higher than this line, you are an astronaut.

The atmosphere protects life on Earth. It only lets through a small part of the electromagnetic spectrum that is conducive to life. This is the visible light. It filters and blocks infrared, ultraviolet, x-rays and gamma-rays, as these are harmful to life.

The Earth’s Magnetic Field

The Earth is like a gigantic magnet with poles at the top and bottom. Its core is believed to be made up of molten iron.

The Earth’s magnetic field spreads from the surface and occupies a region known as the magnetosphere. This region prevents the solar wind and particles from the sun from hitting the surface of the planet directly and causing harmful radiation.

Earth Shares Its Orbit around the Sun with Two Asteroids 

There are two asteroids orbiting the sun following Earth’s orbit. One of these asteroids is 3753 Cruithne, also referred to as earth’s second moon. It appears to follow the Earth as it orbits around the sun. Another asteroid on Earth’s orbit is 2002 AA29. This one comes closer to our planet every 95 years.

The Earth is Not a Perfect Sphere

The Earth does not have a perfect spherical shape. The gravitational forces of the sun and moon, and the speed of the Earth as it rotates on its own axis pull the Earth causing a bulge at the Equator and a slight flattening at the poles. This creates a difference of 43km between the polar and equatorial diameters and makes the Earth an oblate spheroid.

The Earth Is Round but Not a Perfect Sphere

The Earth Is Round but Not a Perfect Sphere. Image credit Wikipedia.

A Day on Earth Is Less than 24 Hours and a Year More Than 365 Days

It takes the earth exactly 23 hours 56 minutes and 4 seconds to complete one rotation on its own axis. Scientists call this a sidereal day. However, since the sun also moves slightly, one complete rotation appears to take 24 hours.

One complete orbit of the Earth around the sun takes 365.2564 days. The extra 0.2564 day every year adds up to 24 hours in February of every fourth year. This extra day is known as Leap day.

Earth’s Moon

The earth has only one moon. The moon’s radius is a quarter that of Earth making it the largest satellite relative to the size of its parent planet.

The moon orbits the earth in the same time it takes for the earth to rotate on its own axis. Because of this, the same side of the Moon is always facing our planet. The dark side of the moon has only been seen in photos.

Earth, the Densest Planet in the Solar System

Earth is the densest planet in the solar system with an average density of about 5520 kg/m 3. This is approximately five times the density of water. This high density is because Earth is composed of large amounts of iron especially at its core.

The Earth is the Only Planet with Tectonic Plates

The outer crust of the earth is divided into regions known as tectonic plates that float on top of its molten core. These tectonic plates are constantly in motion helping to shape and form the planet. They also facilitate the recycling of carbon to maintain the Earth’s carbon balance and prevent overheating (greenhouse effect) like the one experienced on Venus.

These tectonic plates also collide with each other resulting into earthquakes and mountains forming.

The Earth’s Surface

The Earth’s Surface. Image credit sciencedaily.com.

The Earth Seen from Deep Space

A sobering fact is that Earth makes up such a small portion of the known universe.  The below image shows our planet from deep space taken by the Voyager 1 space craft on it’s way out of the solar system. All human history and all life as we know it resides in that one tiny dot.

The Earth as seen from far away

The Earth as seen from far away. Image credit Wikipedia.