My Science School

 

 

 

 

What is the tail of a comet?

You cannot see the nucleus of a comet with the naked eye, but you can sometimes see its tail. It appears as a smear of light that moves very gradually across the sky. As a comet moves closer to the Sun, the ice and other frozen gases in its nucleus begin to boil off, producing a long tail of gas and dust. The tail always points away from the Sun because light and other forms of radiation from the Sun push against the minute particles that are present within the tail.

 

 

 

 

 

What is an asteroid?

Asteroids are small rocky or icy bodies that orbit the Sun. They are sometimes called minor planets. Most asteroids are found in an orbit between Mars and Jupiter, and more than 7,000 of them have been identified.

Asteroids are smaller than any of the planets, and only a few have a diameter of over 30 km. The term asteroid is usually applied to objects larger than 1.6 km in diameter. One asteroid, called Ida, has a tiny moon of its own; this is the smallest known satellite in the Solar System. Asteroids were probably formed at the same time as the planets. 

 

 

 

Space bombardment

Many asteroids have struck the Earth already, and many scientists believe that such an impact resulted in the extinction of the dinosaurs about 65 million years ago. At that time an asteroid or huge meteorite about 10 km in diameter struck the Yucatan region of Mexico. It gouged out a huge crater and hurled so much dust into the Earth’s atmosphere that the world’s climate changed drastically causing the death of the dinosaurs. 

 

Do other planets have moons?

Apart from the Earth, most of the other planets have moons although these are usually quite small. Saturn has the most moons — it has at least 18. Some of these are very strange. Enceladus has a smooth surface covered with shiny beads of ice that make it shine and glitter. Lapetus is black on one side and white on the other.

Jupiter has 16 moons, four of which are very large. One of Jupiter’s moons is larger than Mercury and the other three are larger than our Moon. Charon, which orbits Pluto, is either a large moon or a small companion planet. 

 

 

 

 

 

 

What are shooting stars?

Shooting stars, or meteors, are streaks of light that cross the night sky, although they can only be seen for one or two seconds. They are caused when a solid piece of rock called a meteoroid plunges through the Earth’s atmosphere, burning up due to air friction. When the rock enters the atmosphere it is known as a meteor. If, as rarely happens, a small fragment reaches the Earth, it is called a meteorite.

The Earth regularly passes through clouds of meteors orbiting the Sun. The best-known cloud, called the Perseids, reappears each year on August 12-13, sometimes producing spectacular meteor showers. There is also a regular meteor shower in December called the Geminids. 

 

 

 

 

What is a comet?

Comets are often described as ‘dirty snowballs’. The solid centre, or nucleus, of a comet consists mostly of ice mixed with sooty material. The nucleus is quite small, and is usually only a few kilometres across.

Comets travel around the Sun in an elongated orbit. They plunge out into deep space beyond the farthest planet before diving back into the Solar System and passing close to the Sun. As the comet’s nucleus comes closer to the Sun it becomes smaller and may eventually break up into small fragments. Comets are thought to be as old as the Solar System itself.

 

 

 

Where is the largest known canyon?

            On Mars! There is no running water to wear away the rocky landscape on Mars, so huge valleys can survive for millions of years. A system of enormous canyons called the Valles Marineris (Mariner Valleys) was discovered by the space probe Mariner 9. It is more than 4,000 km long, and four times as deep as the Grand Canyon in the USA. Scientists think that these valleys were caused by erosion (wearing-away). During storms the gritty Martian dust is blasted by winds reaching up to 450 km/h, wearing away the softer rock.

 

 

 

 

 

 

 

 

Which are the outer planets?

            Uranus, Neptune and Pluto are the outer planets. They are so far away that they were discovered only when powerful telescopes were developed. Pluto, the smallest and most remote of the planets, is on the edge of deep space. It was only discovered in 1930, as a result of mathematical calculations to find out why Neptune’s orbit was being disturbed by an unknown body. Pluto has an oval orbit that occasionally takes it inside the orbit of Neptune. As recently as 1978 scientists found that Pluto, which is only 2,284 km across has an even smaller companion planet or Moon called Charon.

 

 

 

 

What are the rings of Saturn?

Shining rings of billions of tiny chips of ice, rock and dust surround Saturn. The rings reflect light strongly and can be clearly seen through a telescope from the Earth. It was first thought that Saturn had three wide rings, but it is now known that the rings are actually made of thousands of narrow ringlets. The rings are only 100 m thick, but they extend into space for 76,000 km. the material in the rings was probably captured by Saturn’s gravity when the Solar System was forming, or it might be the remains of a moon that has broken up. Recently space probes discovered that some of the rings are braided, or twisted, but so far there is no explanation for this strange effect.

 

 

Continue reading "The Solar System"

 

 

Which planet is closest to the Sun?

Mercury is the closest planet to the Sun. the temperature on the side of the planet facing the Sun is as high as 430 degree Celsius. The shaded side of Mercury which faces away from the Sun is bitterly cold at – 180 degree Celsius.

            Mercury has almost no atmosphere because it has been burned off by the Sun. The planet consists of bare rock, pitted and scarred by the impact of meteorites. It has extremely steep cliffs that are hundreds of kilometres long. These were formed when the planet cooled from its original molten (liquid) state millions of years ago.       

 

 

 

 

   

What are the inner planets?

            The four planets that are nearest the Sun are called the inner planets. In order from the Sun, they are Mercury, Venus, Earth and Mars. The inner planets are different from the outer planets, which are farther away from the Sun, because they are made of rock. The outer planets are mostly composed of gas. Each of the inner planets has an atmosphere. However, apart from the Earth’s atmosphere, the atmospheres of the inner planets are very thin and would be poisonous to humans.

 

Continue reading "The Solar System"

 

What is a black hole?

            A black hole is an area in space where the force of gravity is so strong that even light cannot escape from it. Black holes are created when a burned-out star collapses. Eventually it shrinks into a tiny sphere of material. The gravity of this material is so powerful that it pulls in everything around it. Even light it is sucked into the black hole. Nothing that goes into a black hole ever comes out. We cannot see black holes. We can sometimes identify them from the radio waves given off as a star is drawn into a black hole.

 

 

 

 

How far away are stars?

            The nearest star to the Earth is our own Sun, which is 152 million km away. After the Sun, the closest stars are Proxima Centauri and Barnard’s Star. The farthest stars in our Galaxy are 80,000 light-years away. Other galaxies, each one containing millions of stars, are much more distant.

 

 

 

 

 

Why do stars twinkle?

            Most stars burn steadily and if we could see them from space they would not be twinkling at all. As the light from a star passes through the Earth’s atmosphere, it is bent by changes in the air temperature. This makes the light appear to flicker. Because of this effect astronomical observatories are situated on mountain-tops. Higher up, the air is thinner and is less likely to cause this twinkling effect.

 

 

 

 

Neutron stars

            When massive stars explode violently it can lead to a supernova. If the core survives it may become a neutron star. The rapid collapse of the outer part of the star leads to temperatures of over 1,000 million degree Celsius and leaves the core with an average diameter of just 20 km. However, the star still has a mass of up to three times that of our Sun making it incredibly dense. One teaspoonful of neutron star weighs over three billion tonnes!

 

What is a star?

Stars are huge balls of burning gas that are scattered throughout the Universe. They burn for millions of years, giving off both light and heat. Stars produce energy by a process called nuclear fusion. The coolest stars are red and dim, while the hottest stars give off blue-white light. The temperatures on the surface range from 3,500 degree Celsius for cooler stars to over 40,000 degree Celsius for the hottest stars.

            A new star is born when gas and dust are drawn together by gravity, forming a huge clump. It heats up until nuclear fusion begins, and the new star appears.

 

How big are stars?

Our own Sun is quite a small star, even though it measures 1,392,530 km across, which is 109 times more than the Earth’s diameter. If the Sun were the size of a football, the Earth would be only 2 mm across. Some stars are known as supergiants. The star Antares, for example, is 700 times bigger than the Sun. There is a star in the constellation of Auriga that may be 3,000 million km in diameter or 4,000 times bigger than our Sun. the neutron star that remains after the explosion of a supernova may be only 20 km in diameter, but of enormous mass. If it weighs more than two or three times that of our Sun, it begins to collapse into a black hole.

 

 

 

How does a star die?

Stars die when they eventually use up all their fuel and burn out, but this process takes many millions of years.

            Towards the end of its life, a star starts to run out of hydrogen to power its nuclear fusion. It starts to cool, becoming a red giant. The red giant swells, and the pressure at its centre becomes so great that the star begins to absorb energy instead of emitting it. In a matter of seconds the star collapses, then explodes into a supernova. This is a huge explosion of light and energy that can be seen right across the galaxy.

 

What is the Milky Way?

The Milky Way is a huge mass of gas and stars that can be clearly seen as a band of light across the night sky.

            The Earth and everything else in the Solar System is part of the Milky Way. It is known as our Galaxy. It is so huge that light takes nearly 100,000 years to travel from one side to another. Where stars are packed close together the Milky Way is bright, but huge clouds of gas and dust block the light from the other parts of the Galaxy. These clouds prevent astronomers from observing the whole Milky Way.

 

 

 

 

The super supernova

Sometimes a star appears in the sky quite suddenly. This happens when there are pairs of stars rotating together. These are called binaries, and there is usually one large star called a red giant, orbiting with a smaller, hotter star. The nova takes place when gas is drawn from the red giant into the smaller star, where the heat causes a massive explosion and emits huge amounts of light. A supernova takes place when a star collapses as it begins to burn out, then suddenly explodes, producing a huge amount of light energy, and leaving behind a tiny core of neutrons, which is the heaviest substance in the Universe. A pinhead-sized mass of neutrons weighs many thousands of tonnes.

 

Continue reading "The Universe"

 

What was the Big Bang?

The Big Bang is the most popular theory about the creation of the Universe. According to it, the whole Universe was created in a split second in one huge explosion. All matter was squeezed together into a tiny, super-hot, dense ball that was smaller than an atom. The ball gradually expanded as it cooled, then exploded, releasing energy and matter in all directions. We cannot see the Big Bang because it would have happened billions of years ago. But we can see that the Universe is growing steadily bigger. All the galaxies are speeding away from each other as the Universe expands.

 

 

 

 

 

What is the Universe made of?

The Universe is made up almost entirely of hydrogen and helium. These are the two lightest elements. All the rest of the matter in the Universe is very rare. Elements such as silicon, carbon and others are concentrated into clouds, stars and planets. The Universe is held together by four invisible forces. Gravity and electromagnetism are the two familiar forces. The other two kinds are strong and weak nuclear forces. These operate only inside the incredibly tiny nucleus of atoms, holding the tiny particles together.

 

 

 

 

 

 

 

How old is the Universe?

It is possible to calculate the approximate age of the Universe by looking at how fast distant galaxies are moving away from us. However, it is not possible for us to make this calculation accurately. Scientists have estimated that the Universe is between 13,000 and 18,000 million year old.

               In the Elephant Island, Shackleton’s party divided into two. Twenty one men were asked to stay back on the island. Shackleton left the island with five chosen rowers, to find a way out and to come back and rescue the members stranded on the Elephant Island.

               Shackleton braved the Southern Ocean for 16 days. Soon, they made a landfall. Unfortunately, three members of the party were too sick and exhausted to continue. Shackleton and the two others climbed the icy mountains. At last they reached their destination on South Georgia Island. Shackleton succeeded in chartering a steamship to rescue his men.

               On 30th August 1916, Shackleton managed to return to the Elephant Island. And he rescued his men from the Elephant Island. 

              Ernest Shackleton set out on the ‘Imperial Trans-Antarctic Expedition’ in 1914. The expedition faced terrible hurdles throughout the journey. Their ship ‘Endurance’ became beset in the ice of the Weddell Sea on the way. He and his crew were forced to spend the whole of the 79 days of the winter there. Finally, the crew was forced to abandon the ship, because it was about to be crushed by the ice.

               However, they had saved a large quantity of food and gear, as well as their three boats. For three months the ice floes took them further to the north. Food shortage became acute as weeks passed. They caught seals and ate their meat. So they could conserve the remaining packaged rations. The most dangerous thing was the cracking up of ice. Sometimes, huge killer whales charged up from below, and sought to attack them.

               Later, Shackleton found that instead of making good progress westwards, they had actually travelled 48 kilometres to the east, as a result of the drifting ice. However, they finally made a landfall on an uninhabited island known as the Elephant Island. 

               Sir Ernest Henry Shackleton was an Irish born polar explorer who led three British expeditions to the Antarctic.

               In 1901, Shackleton joined his first expedition to the Antarctic. Unfortunately, he was sent home early due to bad health, after he, and his companions Scott and Edward Adrian Wilson set a new southern record by marching to latitude 82°S.

               In 1914, he set off on his own expedition to Antarctica. Shackleton was in a race with Roald Amundsen to reach the South Pole. The race ended in December 1911, with Roald Amundsen’s conquest.

               Shackleton later planned a voyage to the South Pole, and while returning, he wanted to pick a different route to the Ross Sea, and thus, become the first person to cross the Atlantic Ocean.

               To this end, he made preparations for what became the Imperial Trans-Antarctic Expedition. On 1st August 1914, Shackleton departed London on the ship ‘Endurance’ for his voyage to the South Pole. There were unimaginable hurdles throughout the voyage, which Shackleton overcame with his will power, and leadership quality. 

            Robert Edwin Peary, an American explorer, known for his discovery of the geographic North Pole, was one of the greatest polar explorers. Peary made several expeditions to the Arctic in the late 19th and early 20th centuries. Peary was one of the first Arctic explorers to study Inuit survival techniques, which he used to his great benefit.

            After many failed attempts, Peary decided to set out on a final voyage. Peary and 23 men set off from New York City on 6th July 1908, under the command of Captain Robert Bartlett.

            They spent their winter near Cape Sheridan on Ellesmere Island. He reached the North Pole with his expedition on 6th April 1909. But, it is now suspected that he might have been 48 to 96 kilometres short of the Pole, but is still credited with the achievement.

            His success is widely disputed today, but his effort was noteworthy. Peary was promoted to the rank of Rear Admiral in the Navy Civil Engineer Corps on 6th April 1909, and retired the same day.

            Admiral Robert Peary died in the US, on 20th February 1920. 

 

               Robert Scott, a British Royal Navy officer and explorer, led two expeditions to the Antarctic region, at the same time as Amundsen.

               Roald Amundsen and Robert Scott took on a gripping race through danger to reach the South Pole. Amundsen reached the South Pole on 14th December, and became the first person to reach the South Pole. Robert Scott reached his destination on 17th January, only to see Roald Amundsen’s Norwegian flag waving their gloriously. However, Robert Scott’s return journey turned out to be a catastrophe, as they were too late to travel because of the deteriorating weather conditions.

               Robert Scott and his entire crew froze to death. Scott is presumed to have died on 29th March 1912. Eight months later, a search party found the bodies, which were buried under the base tent. News of Scott’s death reached the world on the 10th of February, 1913.

               After confirming the legend’s death, the British government recognized him as a national icon.

               However, the reasons behind the fate of Robert Scott and his team were identified as lack of polar knowledge and poor planning skills.

 

               Amundsen planned to sail to the North Pole, and explore the Arctic Basin. But, later he decided to reroute to Antarctica. He kept this as a secret from everyone except his brother, who knew that Amundsen was heading to the South Pole, instead to the North.

               Roald Amundsen even made his crew believe they were embarking on an Arctic voyage, and revealed their destination only when the expedition was leaving their last port of call.

               He set up his Antarctic base in the Bay of Whales, on the Great Ice Barrier. The base was 96 kilometres closer to the Pole than the base of the English explorer Robert Scott, who was heading a British expedition at the same time. But Amundsen was more skilful and he used skis and sledge dogs which ensured rapidness. Robert Scott used Siberian ponies, instead of sledge dogs but they failed to brave the weather. 

 

               Roald Amundsen, from Norway, is one of the world’s most famous polar explorers. He was the first person to sail through the North-West Passage which is the seaway across the Arctic, linking the Atlantic and the Pacific Oceans.

               When Amundsen and his crew progressed through the dangerous course and passed through the North-West Passage, they realized that they had navigated the much sought after North-West Passage. They sighted a whaling ship from San Francisco there.

               Amundsen and his crew were jubilant as they crossed the passage, which had defeated so many seamen for many centuries before them. The Gjoa, Amundsen’s ship, became the first vessel to transit the passage.

               However, more struggles were ahead, as they continued their voyage. His ship got trapped in the ice again. However, the Gjoa passed through the Bering Straits in 1906, and only then could Roald Amundsen claim to be the first to navigate the North-West Passage.