Category Earth Science

Mesosphere

The top of the mesosphere is the coldest part of the Earth’s atmosphere, with temperatures of -143°C (-226°F). Gases here are thick enough to slow down meteors, causing them to burn up. It extends upward to a height of about 85 km (53 miles) above our planet. Most meteors burn up in the mesosphere. Unlike the stratosphere, temperatures once again grow colder as you rise up through the mesosphere. The coldest temperatures in Earth’s atmosphere, about -90°C (-130°F), are found near the top of this layer. The air in the mesosphere is far too thin to breathe; air pressure at the bottom of the layer is well below 1% of the pressure at sea level, and continues dropping as you go higher.

Stratosphere

The air in this layer is very dry and still. The ozone layer, which protects plants and animals on Earth from dangerous ultraviolet (UV) rays that are given off by the Sun, lies in the stratosphere. The stratosphere extends from the top of the troposphere to about 50 km (31 miles) above the ground. The infamous ozone layer is found within the stratosphere. Commercial passenger jets fly in the lower stratosphere, partly because this less-turbulent layer provides a smoother ride. The jet stream flows near the border between the troposphere and the stratosphere.

Troposphere

The gases found in the troposphere make up the air that we breathe. Therefore life exists in this layer. Starting at ground level, it extends upward to about 10 km (6.2 miles or about 33,000 feet) above sea level.Clouds form here, and it is where most of our weather occurs, mainly because 99% of the water vapor in the atmosphere is found in the troposphere. Air pressure drops, and temperatures get colder, as you climb higher in the troposphere.

Thermosphere

Unlike in other layers of Earth’s atmosphere, temperatures here increase as you go higher, some parts rising to 2000°C (3,600°F)! High-energy X-rays and UV radiation from the Sun are absorbed in the thermosphere, raising its temperature to hundreds or at times thousands of degrees. However, the air in this layer is so thin that it would feel freezing cold to us! In many ways, the thermosphere is more like outer space than a part of the atmosphere. Satellites, including the International Space Station, orbit Earth in the thermosphere.

Exosphere

This is the highest layer of Earth’s atmosphere, where it merges into space. Only a few, very thin wisps of gas are found this high above our planet. It would be impossible to breathe here! In fact, air in the exosphere is constantly – though very gradually – “leaking” out of Earth’s atmosphere into outer space. There is no clear-cut upper boundary where the exosphere finally fades away into space. Different definitions place the top of the exosphere somewhere between 100,000 km (62,000 miles) and 190,000 km (120,000 miles) above the surface of Earth.

 

Picture Credit : Google

Earth is surrounded by thick layer of gases, called the atmosphere. These gases protect Earth from the Sun’s rays, keeping temperatures on our planet at a comfortable level. Earth’s atmosphere is divided into a number of distinct layers. At the outer edge of the atmosphere, there is no clear boundary. It just fades into space.

Earth’s atmosphere is about 300 miles (480 kilometers) thick, but most of it is within 10 miles (16 km) the surface. Air pressure decreases with altitude. At sea level, air pressure is about 14.7 pounds per square inch (1 kilogram per square centimeter). At 10,000 feet (3 km), the air pressure is 10 pounds per square inch (0.7 kg per square cm). There is also less oxygen to breathe.

 

Picture Credit: Google

This is an imaginary line around which the Earth spins as it travels around the Sun. Earth’s axis is slightly tilted. This is what is known axial tilt, where a planet’s vertical axis is tilted a certain degree towards the ecliptic of the object it orbits (in this case, the Sun). Such a tilt results in there being a difference in how much sunlight reaches a given point on the surface during the course of a year. In the case of Earth, the axis is tilted towards the ecliptic of the Sun at approximately 23.44° (or 23.439281° to be exact).

This tilt in Earth’s axis is what is responsible for seasonal changes during the course of the year. When the North Pole is pointed towards the Sun, the northern hemisphere experiences summer and the southern hemisphere experiences winter. When the South Pole is pointed towards the Sun, six months later, the situation is reversed.

 

Picture Credit : Google

This is an imaginary line around the middle of the Earth. It lies halfway between the North and South Poles, at 0 degrees latitude. An equator divides the planet into a Northern Hemisphere and a Southern Hemisphere.

The Earth is widest at its Equator. The distance around the Earth at the Equator, its circumference, is 40,075 kilometers (24,901 miles). 

The Earth’s diameter is also wider at the Equator, creating a phenomenon called an equatorial bulge. The diameter of a circle is measured by a straight line that passes through the center of the circle and has its endpoints on the boundary of that circle. Scientists can calculate the diameter of latitudes, such as the Equator and Arctic Circle.

The Earth’s diameter at the Equator is about 12,756 kilometers (7,926 miles). At the poles, the diameter is about 12,714 kilometers (7,900 miles). The Earth’s equatorial bulge is about 43 kilometers (27 miles). 

 

Picture Credit : Google

This is the path that the Earth takes as it travels around the Sun. Earth’s orbit does not form a perfect circle. It is a slightly flattened circle, or oval. Earth takes 365 days, or a whole year, to make one complete journey around the Sun.

As seen from Earth, the planet’s orbital prograde motion makes the Sun appear to move with respect to other stars at a rate of about 1° (or a Sun or Moon diameter every 12 hours) eastward per solar day. Earth’s orbital speed averages about 30 km/s (108,000 km/h; 67,000 mph), which is fast enough to cover the planet’s diameter in 7 minutes and the distance to the Moon in 4 hours.

From a vantage point above the north pole of either the Sun or Earth, Earth would appear to revolve in a counterclockwise direction around the Sun. From the same vantage point, both the Earth and the Sun would appear to rotate also in a counterclockwise direction about their respective axes.

 

Picture Credit : Google

Our solar system is made up of the Sun and the eight planets that travel around it- Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The solar system also has moons, comets, asteroids, and meteoroids zipping through it. Scientists estimate that our solar system was formed about 4.6 billion years ago!

The Sun’s nearest known stellar neighbor is a red dwarf star called Proxima Centauri, at a distance of 4.3 light years away. The whole solar system, together with the local stars visible on a clear night, orbits the center of our home galaxy, a spiral disk of 200 billion stars we call the Milky Way. The Milky Way has two small galaxies orbiting it nearby, which are visible from the southern hemisphere. They are called the Large Magellanic Cloud and the Small Magellanic Cloud. The nearest large galaxy is the Andromeda Galaxy. It is a spiral galaxy like the Milky Way but is 4 times as massive and is 2 million light years away. Our galaxy, one of billions of galaxies known, is traveling through intergalactic space.

The planets, most of the satellites of the planets and the asteroids revolve around the Sun in the same direction, in nearly circular orbits. When looking down from above the Sun’s North Pole, the planets orbit in a counter-clockwise direction. The planets orbit the Sun in or near the same plane, called the ecliptic. Pluto is a special case in that its orbit is the most highly inclined (18 degrees) and the most highly elliptical of all the planets. Because of this, for part of its orbit, Pluto is closer to the Sun than is Neptune. The axis of rotation for most of the planets is nearly perpendicular to the ecliptic. The exceptions are Uranus and Pluto, which are tipped on their sides.

 

Picture Credit : Google