The Earth and the Universe

physics 2012

EARTH UNIVERSE THE

& THE

DAY&NIGHT What happens during sunrise and sunset?

by warren busuttil and james schembri

COPERNICUS and his new idea about the universe

SOLAR SYSTEM We are a tiny spot in the...

WAKE UP!

Table Contents DAY&NIGHT 4SEASON GRAVITY NICOLAUS COPERNICUS THE MOON ISAAC NEWTON SATELLITES SOLAR SYSTEM SUN, MERCURY, VENUS EARTH, MARS, JUPITER SATURN, URANUS, NEPTUNE GALAXIES CONSTELLATIONS

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It’s 6.00am!!

Wake up!! Time for school.

Another day just started… it’s time to eat your breakfast, wear your uniform and catch your school bus.

Today you have another eight hours at school and when you’re back home you have to do your homework, go to the gym or football training, watch some television and meet your friends and at 10.30pm, time to go back to your bed.

But have you ever thought about what really happens when a day starts and ends? What happens during sunrise and sunset?

So let us see…

MSS4202 | The Earth and the Universe Warren Busuttil and James Schembri B. Ed. (Hons) 2007 - 2011

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DAY&NIGHT Earth turns slowly on its own axis once a day. Half of the Earth is in sunlight, and the other half is in shade (shadow). As each place moves from sunlight into shadow, it passes from daytime into night. In other words, the sun appears to rise

As the Earth rotates, Malta moves from sunlight into shadow.

(in the east) and sets (in the west).

The parts of the world that are in daylight get warmer while the parts that are dark gradually lose the heat they absorbed during the day. Every place on Earth takes 24 hours to spin round.

Did you know?

The Sun is around 4.5 billion years old.

The light of the Sun takes 8 minutes to reach Earth.

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4 SEASONS Have you ever wondered why we have four seasons during the year spring, summer, autumn, winter?

The Earth does no turn slowly on its self but it also moves round the Sun in a near-circular path. This path is called an orbit. Each orbit takes just over 365 days, or one year. When we celebrate another new year, the

Earth has just ended its whole orbit round the Sun. The Earth’s axis is tilted by 23.5 degrees. One hemisphere points toward the sun as the other points away. Because of this, most regions get varying hours of daylight through the year and varying climate conditions.

Many parts of the Earth get four seasons: spring, summer, autumn, and winter. However in equatorial regions other seasons apply.

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ISAAC

NEWTON

GRAVITY Gravity is a force made by everything in the universe, this force pulls on everything else as it reaches across space. The bigger an object is, and the closer you are to it, the stronger the force of gravity is. The Earth’s gravity pulls you towards it and your gravity pull the Earth towards you! The further you go from Earth, the weaker its pull becomes. But gravity still works billions of kilometres away. That’s why the Earth’s gravity ‘holds’ the moon orbiting around it.

One day when Sir Isaac Newton (1642 - 1727) was drinking tea in the garden, he saw an apple fall to the ground.

He started thinking about why it fell, and finally concluded that there is a force which caused the apple to fall. This force, gravity, also kept the planets in orbit around the sun.

The apple incident led to his three basic laws of motion: An object in motion tends to remain in motion unless an external force stops it; an object moves in a straight line unless some force diverts it; and for every action, there is an equal and opposite reaction. He also found that the force of gravity obeys an inverse square law: doubling the distance between two masses reduces the force of gravity between them.

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M

ON

The Moon moves around the Earth in a near-circular orbit. Each orbit takes about a month - or to be more accurate, 27.3 days. The Moon also takes 27.3 days to turn once on its axis, which is why it always keeps the same face towards us.

The Moon is smaller than the Earth and has a rocky, crated surface.

The craters were mainly caused by the impact of large meteorites over a billion years ago. We see the moon because its surface reflects sunlight. Once a month, when there is ‘full Moon’, the whole of the sunlit side is facing us. But most of the time, we can only see part of the sunlit side. The rest is in shadow.

NICOLAUS

COPERNICUS

For thousands of years, most people believed that the Sun and all the planets revolved around the Earth, just as the Ancient Greek astronomer Ptolemy suggested. In 1530, a Polish scientist Nicolaus Copernicus showed that the Earth is revolving round the Sun, just like other planets. He published his book De revolutionibus few months before he died and later Galileo Galilei, the Italian astronomer, studied and supported the heliocentric model (the Earth is orbiting round the Sun) suggested by Copernicus.

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SATELLITES Any object in orbit around another massive one is called a satellite. So the Moon is a natural satellite of the Earth (it is orbiting round the Earth in a natural way). However, when people talk about satellites, they usually refer to artificial satellites launched from Earth. Â There are hundreds of these satellites around the Earth. Some of the satellites are used for communication and their motion is

exactly matched with the Earth’s rotation so it appears to be stationary (not moving). Other satellites are used for monitoring satellites (such as weather satellites), and navigational satellites (used be boats and other crafts). By searching on the internet try to find out the position of your school and home. These images are captured by monitoring satellites, such as the ones by Google Earth, which are orbiting round the Earth.

The first satellite named Sputnik 1 was launched by the Soviet Union on 4th October 1957. It was a football sized globe that transmitted a "beep beep" sound as it orbited the Earth. The word Sputnik means satellite. It continued transmitting for about 21 days.

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SOLARSYSTEM The Earth is one of many planets in orbit around the Sun. Planets are not hot enough to give off their own light. We can only see them because they are reflecting light from the Sun. From Earth, they look like tiny dots in the night sky and without a telescope, it is difficult to tell whether you are looking at a star or a planet.

 Planets orbit round the Sun because of its force of gravity on them. Most of them are in a circular orbit with the Sun at the centre. They have a nearly rounded shape and has cleared the neighbourhood around its orbit. Now lets start our engines a have a safe journey round every planet in our Solar system (planets which are orbiting round our sun).

Remember...

My Very Energetic Mother Just Served Us Nuggets

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune

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THE SUN Typical star in our galaxy.

It is the centre of all planetary orbits (i.e. the Earth, Mars and all the other planets).

It has a cross dimension of 1,400,000km.

It is calculated to have a mass of 2.0 x 1030 kg.

It generated light by consuming vast quantities of hydrogen.

VENUS

MERCURY It is the closest planet to the Sun, having a temperature of about 430oC during the day and -180oC at night.

Its diameter is calculated to be 4900km.

It is 58 million km distant from the Sun. It has a day length of about 58 Earth days. It has a year length of 88 Earth days. It has no moons.

The poisonous cloud that trap the Sun’s heat, create surface temperature of about 500oC. It spins the opposite direction of other planets.

Its diameter is calculated to be 12100km.

It is 108 million km distant from the Sun. It has a day length of about 243 Earth days.

It has a year length of 225 Earth days.

It has no moons.

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EARTH Two-thirds of it is covered with water.

It is the only known planet in our galaxy which is prone to life.

Its diameter is calculated to be 12700km.

It is 150 million km distant from the Sun. It has a day length of about 1 Earth day.

It has a year length of 1 Earth year.

It has one moon.

JUPITER

MARS It is about half the size of the Earth.

When the Sun used to be hotter, Mars used to have rivers and lakes on its surface.

Its diameter is calculated to be 6800km.

It is 228 million km distant from the Sun. It has a day length of about 24 hours 37 minutes.

It has a year length of 1.9 Earth years.

It has two moons.

It is the largest planet in the galaxy made from dense layers of gas..

Its diameter is calculated to be 142000km.

It is 778 million km distant from the Sun. It has a day length of about 9 hours 51 minutes.

It has a year length of 11.9 Earth years and 28 moons.

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SATURN Its diameter is calculated to be 120500km.

It is 1427 million km distant from the Sun. It has a day length of about 10 hours 39 minutes.

It has a year length of 29.5 Earth years. It has 31 moons.

It’s largest ring stretch 250000km across, but is less then 1km thick.

NEPTUNE

URANUS The methane gas in its upper clouds gives it the greenish appearance.

Like Saturn and Jupiter, it has rings.

Its diameter is calculated to be 51000km.

It is 2869 million km distant from the Sun. It has a day length of about 17 hours 14 minutes.

It has a year length of 84 Earth years.

It has five moons.

Bluish in colour and its largest moon is actually bigger then Pluto.

Its diameter is calculated to be 50500km.

It is 4496 million km distant from the Sun. It has a day length of about 18 hours.

It has a year length of 164.8 Earth years.

It has eight moons.

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GALAXIES A galaxy is a group of millions of stars that are relatively near each other. Most stars seem to be in one or another galaxy. Earth's own star, the Sun, is in the Milky Way galaxy.

Small galaxies have about ten million stars, while big galaxies sometimes have a trillion stars in them. There are probably more than a hundred billion galaxies in the whole Universe.

MILKY WAY Is the large, disk-shaped aggregation of stars, or galaxy, that includes the sun and its solar system. Its name is derived from its appearance as a faintly luminous band that stretches across earth's sky at night. This band is the disk in which the solar system lies and it thought to be about 10,000 light-years thick. But what are ‘light years’?

LIGHT YEAR Distances between stars are so vast that astronomers have special units for measuring them. One light year (ly) is the distance travelled by light in one year. The speed of light is nearly 300 000 kilometres per second, so light travels more than 9 million million kilometres in one year. So to be more accurate, 1 light year = 9.5 x 1012 km

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CONSTELLATIONS For thousands of years, people have been looking at the sky and seeing patterns in the positions of the brightest stars. The different groups of stars are called constellations.

The have been named after animals, objects, and figures from mythology.

For example: the Great Bear, the Cross, and Orion the Hunter. For practical reasons, astronomers still divide up the sky into constellations.

It helps them locate and identify the stars more easily from other objects in space.

Dubhe

Merak

Phecda Megrez

Alioth

Alcor

URSA MAJOR also known as the Great Bear, is a constellation visible throughout the year in most of the northern hemisphere. Part of this constellation can also be seen on the background picture.

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