My Science School

The answer is yes and no. And I am not being deliberately awkward. Sound waves die out, but light waves do not.

Sound waves behave like the ripples on a pond after you have thrown a stone into it. They get weaker and weaker as they move away from the centre. Finally they fade out altogether. Water has a certain amount of friction, which reduces the energy of the waves until it is all used up.

The air has friction too. It is less than the friction in water. But it is friction all the same and it reduces the energy in sound waves in the same way. If sound waves did not die out, it would now be possible to ‘overtake’ them in aircraft that fly faster than the speed of sound. Imagine that! If you flew for long enough and fast enough, you might be able to catch up with some of the great sounds of history – battles, volcanoes erupting, they would all be there.

Light waves are another matter. Friction does not affect them. So if we could travel faster than the speed of light we could see things that happened in the past. There is a snag, though. Light travels at a cool 300,000 kilometres per second! So overtaking that speed is the sort of dream that is going to stay a dream for a very long time to come – probably forever.

 

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Seeing even further

Some objects are so far away and so faint in our sky that we can’t see them clearly, even with the most powerful telescopes on Earth. But scientists have found two ways to view such distant objects: space probes and space telescopes.

A space probe is a spacecraft with no people on board. A probe may go far out into space, or it may land on a planet or moon. Some space probes bring samples back to Earth. Others make one-way journeys, sending back photos and information.

A space telescope is a telescope that stays in space. NASA launched the Hubble Space Telescope from a space shuttle in 1990. The Hubble orbits Earth about 600 kilometres above the surface. It is controlled by radio commands from NASA. The telescope can observe objects 50 times fainter than telescopes on Earth can. It also studies ultraviolet light blocked by Earth’s atmosphere.

Training for Space

In the U.S.A., both pilots and mission specialists spend one year of general training at the Johnson Space Center in Texas. Cosmonauts train at the Y. A. Gagarin Centre, near Moscow, Russia.

At the Johnson Space Center, the training has several parts. One part is classroom work. Students take special courses in topics related to space travel.

Another part is flight training in jet planes. This gives student pilots a chance to practise flying. Students who are training to become mission specialists do not pilot a jet during take-off and landing. But while the jet is in the air, they spend time at the controls.

Students also spend time on special jets that dive through the air. For about 30 seconds, the astronauts feel as if they do not weigh anything at all. This prepares them for the way they will feel when they are in space - weightless.

Survival training is also part of the programme. Students learn how to survive in the forest or in the water. They do this in case they have to make an emergency landing on Earth.

Early cosmonauts began with two months of very difficult activities that included high diving, skiing, wrestling, and parachuting. They also had difficult training in machines that made them experience extreme heat, gravity, and spinning motion.

As scientists have learned more about space, cosmonauts no longer need to be tested in such difficult ways. Now cosmonauts spend most of their time studying spacecraft and working in machines that are like imitation spacecraft.

During mission training, students study the cockpit of a spacecraft and are asked to perform certain tasks as if they were in space. A student who does well in all this training may be accepted as an astronaut or cosmonaut.

Today, astronauts and cosmonauts come from many countries of the world. But it is not easy to qualify to work in space. You must have a college degree in subjects related to space travel, such as maths or science. There is no age limit, but to become an astronaut, you must pass the space flight physical given by the American National Aeronautics and Space Administration (NASA). A physical is a test or series of tests that determines a person’s health.

There are two kinds of astronauts trained by NASA as space-crew members: pilots and mission specialists. Either trainee must be between 1.63 and 1.93 metres tall. If you want to pilot a spacecraft, you need to have spent at least 1,000 hours piloting a special type of jet aircraft.

Mission specialists must have spent at least three years doing the kind of work they will do on a mission. Some mission specialists operate and repair machinery and instruments in space. Others carry out experiments and tests to find out how things work in space. Others study the stars.

Russian astronauts are called cosmonauts. The first cosmonauts were military pilots and flight instructors. Most were in their early 20’s.

Since Valentina Tereshkova’s 1963 flight, crews of cosmonauts have included scientists and doctors. The first cosmonauts spent less than two years in training. Today, cosmonauts spend 8 to 10 years preparing for space flight. They train at the Y. A. Gagarin Centre, also called “Star Town”, near Moscow.

The space shuttle was a winged rocket plane operated by NASA from 1981 to 2011. A space shuttle’s orbiter could land on ordinary airfields, and so it could be used many times. NASA’s five space shuttles flew 135 missions. The final mission of the space shuttle program ended July 21, 2011.

Space shuttles were used to launch satellites and to recover damaged ones and return them to Earth. Shuttles also carried people and supplies into space to help build the International Space Station.

Space shuttles were powered by twin solid rocket boosters and powerful engines. After launch, the empty rocket boosters would fall away and parachute into the ocean. They were then recovered to be used again.

Just before going into orbit, the shuttle’s giant main fuel tank would fall away. Smaller fuel tanks provided the rest of the energy needed. When the shuttle returned to Earth, it glided down using just its wings.

Flight crews did most of their work on the flight deck. They prepared meals and slept on the middeck. The shuttle’s cargo was carried in the payload bay.

Space Stations

Some things can be done in space that can’t be done on Earth. For example, certain materials won’t mix on Earth because of gravity, but they will mix in space. This could make it possible to produce new kinds of metals, medicines, and other useful things in space.

So how can scientists test such materials? They can test them in a laboratory called a space station. A space station is a place where scientists and technicians can live and work in space for a long time - weeks or months. Space stations are very large. Smaller spacecraft are used to carry people between Earth and the space station. Other spacecraft are used to supply the station with food, water, equipment, and mail.

A space station orbits Earth hundreds of kilometres above Earth’s surface. It also may be used as an observatory, factory, and warehouse.

In 1975, a U.S. Apollo spacecraft linked up with a Soviet Soyuz spacecraft. For the first time, crews from two different countries worked together in space. Since then, the many countries involved in space exploration have co-operated often.

Studying the Universe

Since ancient times, people have studied heavenly bodies. Astronomers of the past knew only about the objects they could see with just their eyes or with basic telescopes. Today, astronomers have powerful telescopes, computers, and many other tools to help them learn about the universe.

Early Sky-watchers

In ancient times, most people had no way of knowing what was beyond the furthest mountain they could see. To help explain what the world looked like, they made up stories.

One ancient Eastern legend said that the world was flat and rested on the backs of four elephants. The elephants all stood on a huge tortoise, and the tortoise stood on an even bigger serpent. And the serpent? He floated on the surface of an endless ocean.

In ancient India, people believed Earth was a flat disc surrounded by an ocean. A layer above Earth held the clouds. The sky formed another layer above the clouds. The heavenly bodies moved around the sky in chariots drawn by horses. A huge dome-shaped shell surrounded and protected all three layers.

The ancient Egyptians believed in a sky goddess named Nut. Nut, it was said, supported the heavens on her back.

To the ancient Navajo, who lived in a hot dry desert, the rainbow was a god. The sky was their father who watched over them.

People in Space

Many people have explored the sky from Earth. Others have travelled up there for a closer look.

The first space travellers from Earth were not people at all. They were animals! In November 1957, scientists from the Soviet Union sent a dog named Laika into space in a satellite called Sputnik 2. Laika’s journey proved that animals could survive a trip into space.

On January 31, 1961, the U.S.A. sent Ham, a chimpanzee, into space in the Mercury space capsule. Animal flights helped scientists prepare for the challenge of sending people into space!

Not long after Ham’s journey, on April 12, 1961, Yuri Gagarin from the Soviet Union became the first person in orbit. His flight lasted 108 minutes.

Alan B. Shepard became the first U.S. astronaut launched into space. He took off May 5, 1961.

John Glenn became the first U.S. astronaut to orbit Earth. In 1962, he circled Earth three times.

In 1963, Soviet cosmonaut Valentina Tereshkova became the first woman in space. She made 45 orbits of Earth.

The first spacewalk took place in 1965. That year Alexei A. Leonov, from the Soviet Union, became the first person to step outside a spacecraft.

In 1984, American astronaut Bruce McCandless attached himself to a jet-propelled backpack. This let him move around in space without a lifeline linked to his craft. McCandless was his own miniature spaceship! He kept his face towards the shuttle so that he wouldn’t lose sight of it.

In 1991, Helen Sharman became the first British astronaut in space.

In 1992, Mae Carol jemison became the first African American woman to travel in space.

In 1995, cosmonaut Valery Polyakov completed a record 438 days in space. In 1996, American astronaut Shannon Lucid broke two records for time spent in space with 188 days. That was the longest time for any woman and the longest time for any American.

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First person on the Moon

One of the greatest adventures in history took place on July 20, 1969. A human being visited Earth’s closest neighbour in space. After a voyage of almost 386,000 kilometres across space, American astronaut Neil A. Armstrong became the first person to set foot and walk on the moon.

Four days earlier, the spacecraft Apollo 11 had been launched. On board were Michael Collins, the pilot, and two astronauts, Edwin E. Aldrin, Jr., and Neil Armstrong.

On July 20, Apollo 11 reached the moon and circled it in orbit. Armstrong and Aldrin entered the lunar module section of the spacecraft, called the Eagle, and separated it from Apollo 11. A blast of the Eagle’s engine sent it speeding down towards the moon’s surface.

There is no air on the moon, so the Eagle could not fly down like an aeroplane. It had to fall, at a speed of more than 3 kilometres per minute. Bursts from the engine slowed it down enough so that it landed gently. Apollo 11, with Collins on board, continued orbiting the moon.

That evening, Armstrong radioed to Earth, “The Eagle has landed.” Armstrong descended the ladder first. As he set foot on the moon, he said, “That’s one small step for a man, one giant leap for mankind.” After collecting rocks and soil samples, the two men rocketed part of the Eagle back up to Apollo 11.

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Artificial Satellites

Artificial satellites send signals. There are many different kinds of signals they send. Each carries a different type of information.

Some artificial satellites send their signals to radios, telephones, and television sets. These are called communications satellites. Ships, aircraft, and even some cars use navigation satellites to work out their location on Earth. Weather satellites take pictures of the movements of the clouds. Scientific research satellites send information about the universe. Scientists can use an earth observation satellite to look at Earth and find heavily polluted areas or damaged forests. Military satellites can send signals about the movement of missiles, ships, and soldiers.

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A manufactured Moon

You know that a moon is a natural object that orbits a body in space. But did you know that another name for a moon is satellite? An artificial moon, or satellite, is one made by people. Here’s the story of the first artificial satellite.

On October 4, 1957, a rocket took off from Earth. It carried an artificial satellite that weighed 83 kilograms, and its powerful engine drove it at a speed of nearly 8 kilometres per second. The Soviet scientists who had launched it from the former Soviet Union watched nervously as it roared into space.

The rocket quickly reached a height at which it could begin to orbit. Then its nose was automatically pushed off, and a metal globe a little bigger than a football was hurled into space. The globe then went into orbit.

Four long, slim antennas (long metal rods) automatically opened up out of the metal ball and began broadcasting. Scientists at a special radio station on Earth began hearing a steady, high beep-beep-beep.

That signal told them that the globe was out in space, moving around Earth. Back on Earth, people were very excited. The first manufactured moon, or artificial satellite, had been launched. This artificial satellite became known as Sputnik, which is the Russian word for “traveller”. It orbited Earth every 96 minutes.

Sometimes it was travelling about 230 kilometres from Earth. At other parts of its orbit, it went about 940 kilometres from Earth.

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The First Rocket

On March 16, 1926, a strange metal contraption went roaring up into the sky. It climbed until it was only a speck. The world’s first liquid-fuel rocket had just been launched.

That rocket was built by Dr. Robert H. Goddard, an American scientist. And he kept building better rockets through the 1920’s and 1930’s.

Another great rocket was invented by a German engineer named Wernher von Braun. Von Braun’s team built the V-2 guided missile. Later von Braun went to the U.S.A. His team built the rocket that launched the first successful U.S. satellite.

Great Astronomers

In the 1600’s, Isaac Newton, an English scientist, worked out the rules for the movement of the stars and the planets. He also realized that the planets move as they do because of the force of gravity between the planets and the sun. In addition, Newton made a new kind of telescope. Instead of using two lenses, he used a curved mirror and a small lens. Most of the huge telescopes used today are based on Newton’s.

William Herschel, who was born in Germany and moved to England, discovered the planet Uranus in 1781. He did so with a telescope he invented. His telescope was 1.2 metres wide, the largest telescope built until 1845. Herschel was also one of the first modern astronomers to study the Milky Way Galaxy.

Friedrich Wilhelm Bessel

In the early 1800’s, German astronomer Friedrich Wilhelm Bessel explained why stars seem to move in the sky.

In the late 1800’s, Annie Jump Cannon, the leading American female astronomer of her time, discovered 300 stars that change their brightness.

Edwin Hubble, an American astronomer, discovered in 1929 that galaxies are moving away from each other at very high speeds.

In the late 1990’s, Stephen Hawking, a British scientist, made important discoveries about gravity, particularly black holes. He also wrote several important books, one of which became very popular.

Helen Sawyer Hogg, an American-born astronomer, began publishing works about ball-like groups of stars that vary in brightness. Sometimes, astronomers use information from Hogg’s discoveries to measure how far certain stars are from Earth.

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Watching the stars move

It’s the middle of the day. The lights around you fade. Soon, all you can see are faint stars glimmering overhead. Slowly, the moon rises above the horizon and moves across the sky. But how can you see all this in the middle of the day? It’s easy. You’re in a planetarium.

A planetarium is like a special cinema. Instead of showing films on a flat screen, the projector in a planetarium shows pictures of planets, stars, and moons on a domed ceiling. Your chair tilts towards the dome. Stars and planets seem to move across the sky. They can move faster than in real life because the projector controls them. In just a few minutes you can see how the stars and planets move across the sky all night. You can even see the movement of stars through a season or a year.

Houses for Telescopes

Observatories are like houses for telescopes. Some observatories have cameras and other machines that record the information gathered by telescopes.

Most observatories are easy to spot. Many of them have a dome that looks like an upside-down bowl. The dome keeps the telescope safe from bad weather.

Each dome has a slit through which the telescope can be pointed towards the sky. When the telescope is not being used, this slit is covered by a shutter or a metal blind.

Since the telescope is used to look at different parts of the sky, the astronomers must be able to point the slit in any direction. The dome has wheels at its bottom edge. These wheels run on a circular track near the top of the observatory building. So, the whole dome can be turned.

Most big observatories are built far away from the lights of big cities. City air has dust and smoke that bend light back to Earth. This makes the sky glow, so it is harder to see the stars clearly.

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