My Science School

 

 

 

Has any spacecraft ever left the Solar System?

Pioneer 10 is the first man-made object to leave the Solar System. This probe was launched towards Jupiter in 1972 and by 1983 it had reached deep space. Pioneer 10 carried messages about life on Earth to be read by any extraterrestrial travellers who might meet the probe. 

 

 

 

 

What is a space station?

Space stations allow the crew to work in space for long periods in conditions of zero gravity. While conditions in space capsules and the space shuttle are cramped, space stations are more suitable for longer stays in space. Rockets or the space shuttle bring supplies of air and food to the space station, and often a new crew. Space stations are usually made up of several modules that are sent into orbit, one at a time, and assembled in space. Some space stations, such as the Russian Mir, stayed up for many years, and their crews remained in space for months at a time. 

 

Continue reading "Space Travel "

 

 

Rocker power!

All space flight depends on the use of rockets that burn huge amounts of fuel. They burn high-energy fuel in a chamber which directs the burning gases through a nozzle. As the gases stream out through the nozzle they provide the thrust to push the rocket up into space.

Some rockets are powered by burning kerosene or liquid hydrogen with liquid oxygen, but this requires very careful handling. Other rockets burn solid fuel in a controlled explosion.

 

 

 

One giant leap!

The Apollo project was the United States’ plan to get humans on the Moon during the 1960s. It used the world’s most powerful rocket, Saturn V, to launch the three-man Apollo spacecraft. While orbiting the Moon, the Apollo craft would separate into two parts. The landing module carried two astronauts down onto the Moon’s surface, while the main part remained in orbit with the third astronaut. 

 

 

 

 

 

 

How do satellites stay up?

The speed with which a satellite is launched helps to keep it in orbit. To stay up above the Earth, a satellite must be launched at a speed of about 8 km per second. If the orbit is less than 200 km above the Earth, faint traces of air will gradually slow the satellite so it loses height and eventually crashes to the ground. Satellites that are much higher can stay up indefinitely. Some satellites are placed in a geostationary orbit. This means that their speed exactly matches that of the Earth’s rotation, and they seem to stay above a fixed point on the ground. 

 

 

Who was the first man into space?

Yuri Gagarin was the first man to orbit the Earth. On April 12, 1961 the Soviet Union launched him into space, carried by a converted intercontinental ballistic missile. He only made a single orbit of the Earth and landed safely by parachute. 

 

 

 

 

 

What is the space shuttle?

The space shuttle is the first re-usable spacecraft. It was developed to provide a re-usable, and therefore cheaper, vehicle for launching satellites and for other work in space. The shuttle is a bulky delta-winged aircraft with powerful rocket motors. At launch, two solid-fuel booster rockets are strapped to its sides, and a giant fuel tank is fixed to its belly. The rockets and fuel tank fall away after launch, and the rockets are recovered and re-used. In orbit, the shuttle’s cargo bay opens to release satellites or allow the crew to work in space. The shuttle lands on a runway like a conventional aircraft. 

 

 

 

 

What do space satellites do?

Space satellites have revolutionized communications, making possible everyday developments such as mobile phones and television. Communications satellites receive signals beamed at them from the Earth, and send them on to other places. They transmit television and telephone signals around the world, even to remote areas. They are also used for defence communications, including checking on the movement of military forces. Satellites can survey the Earth’s surface, predict weather changes and track hurricanes. They can also help to examine resources such as crops, forests and even minerals. Navigation satellites enable people on land or at sea to work out their exact map position, to within a few metres. 

What does the surface of the Moon look like?

The Moon’s surface is covered with a thick layer of gravel-like rock and dust. This material was created by the impact of millions of meteorites. The Moon also has mountain ranges, many of which are the remains of impact craters and volcanoes that were active when the Moon was still hot. There are some huge valleys called rilles, which can be hundreds of kilometres in length and look like river-beds. However, scientists do not yet fully understand their origins. 

 

 

 

 

What’s on the far side of the Moon?

The far side of the Moon was a mystery until 1959, when a Soviet space probe took the first photographs of it.

The actual appearance of the far side was something of a disappointment, because it had far fewer craters and other physical features than the familiar side that always faces the Earth. 

 

 

 

 

 

What is the Moon made of?

The Moon is a rocky satellite, and is made of similar material to the Earth. It has an outer layer, or mantle, of rock, and a core that is probably made up mostly of iron. Unlike the Earth’s liquid mantle, the interior of the Moon is cool and solid. There is little or no volcanic activity on the Moon. However, while it was cooling early in its life, floods or streams of lava ran out across the Moon’s surface. 

 

 

 

 

Dead planet!

Living things need air and water to stay alive, and neither of these is available on the Moon. The atmosphere of the Moon is a higher vacuum than can be created in most scientific laboratories. The Moon also suffers extreme temperature swings between the lunar day and night. Lunar conditions have been re-created in laboratories on the Earth, but no form of terrestrial life has been able to survive them. There is some water on the Moon’s surface, in the form of frost that can be found in shadowed craters near the Moon’s poles. 

 

 

 

 

 

 

What is a lunar month?

For thousands of years people have used the Moon to measure the passing of time and the seasons. The Moon revolves around its own axis every 29  days, which is also the time it takes to complete one orbit around the Earth. This period of time is known as a lunar month. Our calendar has been devised to follow this astronomical pattern fairly closely. It has to be adjusted slightly to round up the number of days in each month to a more convenient figure. The sidereal month, of 27.32 days, measures the time it takes for the stars to return to an identical position in the sky.

 

 

 

 

 

Wobbling Moon

We always see the same side of the Moon as it rotates around the Earth. However, it wobbles slightly as it orbits the Earth, giving us a glimpse of some of the features around the edges of its hidden side. Because of this wobble, we can actually see about 59 percent of the Moon’s surface from the Earth. 

 

 

 

 

 

 

Continue reading "Our Moon"

 

 

 

 

Why does the Moon shine?

The Moon is by far the brightest object in the night sky, but it has no light of its own. Moonlight is simply the reflected light of the Sun. Parts of the Moon that are not in sunlight are invisible against the deep blackness of space. Although the Moon appears bright and silvery, only a small proportion of the light that falls on it from the Sun is reflected back towards us. This is because the Moon’s surface is grey and rocky, and does not reflect light well. 

 

 

 

 

 

 

Why does the Moon seem to change shape each month?

The appearance of the Moon alters, depending on the position of the Sun in relation to the Moon. The Sun lights up only one side of the Moon. As the Moon orbits the Earth, we see this lit-up area from different angles. When the Sun is almost behind the Earth, it lights up the whole of the Moon; this is called a Full Moon. When the Sun is off to one side, part of the Moon is in deep shadow and all we can see is a thin slice, or crescent, of the Moon’s lit surface. 

 

What is the Moon?

The Moon is the Earth’s only satellite, and it has been orbiting our planet for at least 4,000 million years. It is a rocky sphere about 3,476 km in diameter, which is about one-quarter the size of the Earth.

Scientists believe that the Moon formed when another planet about the size of Mars collided with the Earth. The collision splashed a huge mass of molten (liquid) rock into space. This molten rock quickly formed into a sphere, and the Moon rapidly cooled into its solid form. The Moon’s surface is heavily pitted by collisions with debris such as asteroids. 

 

 

 

What is a lunar eclipse?

The Earth casts a long shadow into space, and when this shadow passes over the Moon it causes an eclipse.

A lunar eclipse can only happen during a full Moon, when the Sun is directly behind the Earth. It happens only occasionally, because the orbit of the Moon is slightly tilted and so the shadow usually misses it. Lunar eclipses can last for over one hour, but they do not completely black out the shadowed part of the Moon. Some sunlight always filters through, making the shadow look a reddish-brown colour. 

What happens when a meteorite hits the ground?

When a large meteorite hits the ground it can produce a crater. Meteorite craters are rare on the Earth, because the atmosphere slows the meteorite and also usually burns it up. Many ancient meteorite craters have been worn away by water and by weather over thousands of years.

On planets and moons with no atmosphere, huge numbers of meteorites strike with enormous power. Our own Moon is estimated to have 3,000,000 million meteorite craters measuring 1 m or more in diameter. Some of the large geographical features on the Moon and other planets and moons throughout the Solar System are probably the result of strikes by large meteors hitting their surfaces. 

 

 

What are meteorites made of?

Meteorites are made of rock or metal. They enter the Earth’s atmosphere at speeds of at least 11 km per second, which makes them glow brightly. Several thousand meteorites enter the Earth’s atmosphere every year, but very few of them reach the ground. The largest known meteorite is made of iron and weighs 66 tonnes. It probably fell to the Earth in prehistoric times in what is now Namibia, southwest Africa.

In general it is hard to find meteorites. Recently, researchers have been locating them on the ice sheets in the Arctic and Antarctic, where they are easier to find. 

 

 

 

 

Why is Europa especially interesting?

Europa is one of Jupiter’s moons. In 1979 the Voyager spacecraft passed by Europa and found that it had a very smooth surface covered with ice. It has very few craters, which has led astronomers to suspect that there may be liquid water beneath the surface. In theory, there might even be a form of primitive life hidden beneath the ice, where water remains as a liquid.

 

 

 

 

 

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.