My Science School

Scientists launch these to collect information about conditions in Earth’s atmosphere that affect the weather, such as temperature and air pressure. The balloons are made of rubber and weigh up to one kilogram.

The information collected from the instruments on weather balloons are used to learn about current weather conditions, to help meteorologists to make weather forecasts, and to collect data for other scientific research projects. Weather balloons carry instrument packages that are called radiosondes. Scientists have been using them since the 1930s.

To gather information for weather forecasts, weather balloons are launched twice a day, every day, from 800 locations around Earth. They are launched at the same time all over the world. The balloons rise more than 24.14 kilometers (15 miles) while collecting data.

 

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These are bits of matter from outer’s space that burn up on entering Earth’s atmosphere, creating streaks of light. They are also called shooting stars.

 A meteor is a meteoroid that has entered the earth's atmosphere.

It will then become brightly visible due to the heat produced by the ram pressure.

If a meteor survives its transit of the atmosphere to come to rest on the Earth's surface, the resulting object is called a meteorite.

A meteor striking the Earth or other object may produce an impact crater.

During the entry of a meteoroid into the upper atmosphere, an ionization trail is created, where the molecules in the upper atmosphere are ionized by the passage of the meteor.

Such ionization trails can last up to 45 minutes at a time.

Small, sand-grain sized meteoroids are entering the atmosphere constantly, essentially every few seconds in a given region, and thus ionization trails can be found in the upper atmosphere more or less continuously.

When radio waves are bounced off these trails, it is called meteor scatter communication.

 

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These bright lights appear in the thermosphere when particles from the Sun fall into Earth’s atmosphere. Auroras are produced when the magnetosphere is sufficiently disturbed by the solar wind that the trajectories of charged particles in both solar wind and magnetospheric plasma, mainly in the form of electrons and protons, precipitate them into the upper atmosphere (thermosphere/exosphere) due to Earth's magnetic field, where their energy is lost.

The resulting ionization and excitation of atmospheric constituents emits light of varying color and complexity. The form of the aurora, occurring within bands around both Polar Regions, is also dependent on the amount of acceleration imparted to the precipitating particles. Precipitating protons generally produce optical emissions as incident hydrogen atoms after gaining electrons from the atmosphere. Proton auroras are usually observed at lower latitudes.

 

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These orbit Earth in the thermosphere and exosphere. We use them to make phone calls and watch TV. Scientists also use satellites to find out more about space.

Satellites come in many shapes and sizes. But most have at least two parts in common - an antenna and a power source. The antenna sends and receives information, often to and from Earth. The power source can be a solar panel or battery. Solar panels make power by turning sunlight into electricity.

Many NASA satellites carry cameras and scientific sensors. Sometimes these instruments point toward Earth to gather information about its land, air and water. Other times they face toward space to collect data from the solar system and universe.

 

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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.

 

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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.

 

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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.

 

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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). 

 

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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.

 

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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.

 

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Earth is our home. It is nearly 150 million km (94 million miles) from the Sun, and is the fifth largest planet in our solar system.  Its diameter is about 8,000 miles. And Earth is the third-closest planet to the sun. Its average distance from the sun is about 93 million miles. Only Mercury and Venus are closer.

Earth has been called the "Goldilocks planet." In the story of "Goldilocks and the Three Bears," a little girl named Goldilocks liked everything just right. Her porridge couldn't be too hot or too cold. And her bed couldn't be too hard or too soft. On Earth, everything is just right for life to exist. It's warm, but not too warm. And it has water, but not too much water.

Earth is also the only planet in our solar system where water is found on the surface, which allows animals and plants to live there.

 

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          Earth is perhaps the only planet in the solar system where life exists. This is because the conditions favourable for the existence of life are available only on the Earth. Conditions present in other planets make life almost impossible.

          Mercury is the planet closest to the Sun. It is difficult to see it even with a powerful telescope. It does not have any atmosphere. The temperature during the daytime may even go beyond 400°C. The lack of oxygen and the extreme temperature make life on Mercury impossible.

          Venus, which comes next in terms of closeness to the Sun, is often described as the sister planet of the Earth. Venus and the Earth are almost identical in size, mass and density. Its diameter is 0.95 times and mass is 0.815 times as compared to the mass and diameter of the Earth. It is surrounded by thick clouds of carbon dioxide (95%). The temperature on its surface is about 95 times more (480°C) than that on the Earth. This makes Venus the hottest planet in the solar system. Under these conditions life is not possible here.

           Mars comes after the Earth and is much colder than the Earth. Its average temperature is about – 62°C. At night it may drop to – 101°C. It has an atmosphere much thinner than that of the Earth. It has been found that it contains 1 to 2% argon, 2 to 3% nitrogen, 95% carbon dioxide and 0.3% oxygen. These conditions suggest the possibility of existence of life on it but so far no traces have been detected.

          All other planets beyond Mars (Jupiter, Saturn, Uranus, Neptune and Pluto) are farther away from the Sun. The surface temperature of these planets is so low that no living organism can survive there. Besides, their atmospheres contain gases like methane and ammonia which are not favourable to the evolution of living organisms.

          Thus our Earth is the only known planet in the solar system where life exists. 

          The heavenly bodies that revolve round the sun are called planets. There are nine planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. The bodies revolving round these planets are called their ‘satellites’ or ‘moons’.

          Scientific investigations made so far have revealed that all planets do not have satellites. For example, Mercury and Venus do not have any satellite. Earth has 1 satellite - the moon. Mars has 2 satellites and the Jupiter has 16. The number of the moons revolving round Saturn is 24. The Uranus and Neptune have 15 and 6 satellites respectively. Pluto has 1 satellite.

          The size of different satellites is different. There are some satellites which are bigger than moon. The diameter of two satellites of the Mars, Deimos and Phobos, and the outer satellites of the Jupiter, Ganymede and Callisto are as big as Mercury and Mars. The diameters of Titan and Triton - the satellites of Saturn and Neptune are 5150 kms and 2700 kms respectively and more than the diameter of our moon.

          Except Titan, all the satellites have small force of gravity. As such none of them has any atmosphere. Because of low temperature at Titan, it has an atmosphere consisting of methane and hydrogen. But there is no life on this satellite.

          As yet we have not come across any satisfactory theory regarding the origin of the satellites. However, it is believed that their origin is similar to that of our solar system.

          The stars which we see shining at night look very attractive and bright. Some stars look brighter than others. This is so because their sizes and distances from the earth are different. These stars are billions of miles away from our earth and shine with their own light. Do you know how the distance of stars form of earth is measured?

          Scientists have evolved a simple technique to measure the distance of the nearby stars. Suppose we want to measure the distance of a particular star ‘C’. We take its photograph from a place ‘A’ on the earth. After six months, the earth is at the position ‘B’, since it is revolving round the sun. We now take another photograph of the same star from the position ‘B’. A comparison of the two photographs will show that ‘AB’ is the diameter of the earth’s orbit round the sun and is equal to 186 million miles. Now the angle ‘ACB’ is measured. With the help of these two figures, the distance of the star ‘C’ is measured. This is known as the method of triangulation.

          Using this technique, the distance of many stars has been measured. The distance of Alpha Centauri from earth has been found to be about 4.35 light years. The distance of the Sirius has been determined to be 8.48 light years. However, this technique is not suitable for measuring the distance of very distant stars. The distance of such stars is determined on the basis of their brightness or colour. The most widely used system for measuring the distance of stars is the two-dimensional classification method developed by J.M.Johnson and W.W. Morgan. This system is based upon photoelectric measurement in three wavelength bands in ultra-violet, blue and yellow (or visual) regions of spectrum. This method is known as UBV system. Scientists have succeeded in measuring the distance of stars as far away as 8 million light years from the earth.

               Our Earth was born around 4.6 billion years ago. Like the Sun and other planets, it was also formed out of the clouds of dust and gases. However, before turning into present shape it was a fireball surrounded by an atmosphere of burning gases. At that time it revolved round the Sun in the form of a hot spherical body. Hundreds of years later, it gradually started moving away from the Sun while still revolving round it. As it moved farther and farther from the Sun, its temperature kept on decreasing. It started cooling off and its outer layer changed into a crust. With the hardening of this crust, cracks developed in it and molten material from inside started coming out. Over a period of millions of years, this molten material gave birth to mountains and valleys. 

          As time passed by, the thick layer of hot gases enveloping the Earth cooled off and turned into clouds. These clouds rained on the Earth for a long time. Rain-water accumulating in the low-lying areas of the Earth turned into the oceans. With the passage of time, there were upheavals due to which its surface was raised high or pressed down. This produced many volcanoes. Slowly it became calm and the seas and mountains took their definite shapes.

          Subsequently, around 570 million years ago, micro-organisms started developing on the Earth. In the first 345 million years, marine (aquatic) animals came into existence. As more time passed, the aquatic animals also underwent changes.

          In the next phase of evolution, the great reptiles - creatures crawling on the Earth - came into existence. And finally around a million years ago man was born through evolution.

          Today, Earth has all the favourable conditions required for the existence of Iife.lt has an atmosphere absolutely essential for the living beings.