Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 1

Historical ideas about the sun and the earth

Date Idea

Before 600BC Earth was thought to be flat

600BC Greek mariners thought the earth was curved since they

saw the position of the stars changing

350BC Aristotle said the earth was stationary at the centre of

the universe

150AD Ptolemy said that the planets turned on themselves while

going round the earth

1500 Copernicus questioned Aristotle and Ptolemy’s views

1543 Copernicus said that the sun is at the centre of the

universe and the earth and other planets moved around the

sun. The church opposed as they said the earth was central

1610 Galileo supported Copernicus as he observed moons around

Jupiter

1600 Keppler established laws of planetry orbits and Newton

about the theory of gravitation.

1700 William Herschel used a large telescope to study stars and

conclude that the sun was the hear to the centre of a huge

lens shaped system of stars called GALAXY.

1920 Hubble discovered that our galaxy is not alone but there

are million of other galaxies. His studies led to the BIG

BANG THEORY.

Ptolemy

Edwin

Hubble

Galileo

Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 2

The earth spins around its axis which is an imaginary line passing

through the North and South Geographic poles. It turns around

once every 24 hours. From the surface, it seems as if the sun is

passing across the sky during the day and then disappearing at

night. As the earth spins, it also whirls through space at 30 km/s

on its year long journey around sun.

What causes day and night?

https://www.youtube.com/watch?v=cDed5eXmngE

The earth spins on its axis so the half

of it that faces towards the sun, and so

experiences daylight keeps changing. As

a place moves into the half facing the

sun, it becomes light and experiences day. As the place moves

into the dark, shaded half of the earth’s surface, it experiences

night.

In addition to spinning around once a day, Earth travels around

the sun once a year. This journey gives us the seasons. The

lengths of days and nights are different in each season. This

difference is caused by the tilt of Earth's axis. Earth's axis is

an imaginary line that connects the North and South poles. When

the North Pole tilts toward the sun, the northern part of Earth

has summer, with long days and short nights. After six months,

Earth has moved to the other side of the sun. The North Pole now tilts away from the sun,

and the northern part of Earth has short days and long nights.

Discussion: The effects of global warming on

seasonshttp://www.videojug.com/expertanswer/global-warmings-effects-on-plant-and-animal-

life/is-global-warming-affecting-a-change-in-the-seasons

Global warming is affecting the seasons. Autumn and winter are coming later in many places;

spring is coming earlier. If you look at a typical lake or maybe a stream in the far North it

melts earlier in the spring and it freezes later in the fall. The very timing of the seasons is

changing such that the food sources for some insects and birds are not in the places they

are supposed to be when the migrations of these creatures arrive at the place where they

are expected to be fed. And so, the very timing of nature and the seasons is being upset by

global warming.

Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 3

Do the stars move?

https://www.youtube.com/watch?v=bzZxC58Y688

Because of its huge distance between the stars and earth, the stars appear fixed relative

to one another and seem to rotate together across the sky as the earth spin on its axis. The

stars hardly move at all. It is the earth turning on its axis that makes them appear to move.

Planets emit light or reflect it from the sun?

https://www.youtube.com/watch?v=US_O0uK5piA

As you look into the night sky, to the naked eye the planets look like tiny dots of light quite

similar to stars. However they appear this way because they reflect light from the sun, not

because they produce light as stars do. Planets move in the sky relative to the sky.

Objects which have a mass attract each other. The

heavier the mass the greater the force.

Every object has gravity called gravitational attraction. This attracts or pulls other objects.

So a ball flying through the air pulls the earth towards it as well as the earth pulling the

ball. But because the earth has so much more mass than the ball, and so a much greater

inertia it is the ball that moves. Objects like stars are so massive they have huge

gravitational attraction. The sun’s gravity holds all the planets including earth in orbit

around it.

Discussion: Galileo and Gravity

The Leaning Tower of Pisa from which Galileo did his

famousball dropping demonstrationBy the way some say the Leaning

Tower demonstration was a myth.

Newton and the law of gravity https://www.youtube.com/watch?v=IIYSdln2H30

Gravity has always been around. In ancient times, people tried

to explain why things fall toward Earth. An English scientist

named Sir Isaac Newton came up with a great idea about

gravity in 1687. He thought about how an apple falls and

wondered how far gravity went. He came up with the idea that gravity does more

than hold people on Earth. Newton thought of gravity as a kind of mysterious

force pulling objects together. He said that gravity holds the Moon in orbit

around Earth. It holds the planets in orbit around the Sun. Newton’s ideas on gravitation

explained many things about how apples fall and how stars and planets move.

Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 4

The moon orbits the earth and the planets

orbit the sun because of gravitational force.

The earth and the moon attract each other, but the earth is much more

massive so the earth stays almost still compared to the moon while the

moon goes around it.

Satellites can be put into orbit round the earth because of the gravitational force between the earth and the

satellites.

https://www.youtube.com/watch?v=6dISKhVdX7g Gravity keeps objects on the earth including the molecules of the earth’s atmosphere from

the surface. Artificial satellites are carried into space by rockets or space shuttles. A

satellite must be directed into orbit once it is in space. The pull of gravity due to the earth

keeps it in orbit at steady speed. Because gravity decreases with increasing distance, the

higher the orbit, the longer it takes for the satellite to orbit the earth.

Monitoring satellites

Put into low orbit (500-1000km ) passing over the poles. Such a

satellite orbits the earth several times each day since it is at low orbit.

This enables it to scan the entire surface each day.

The following is satellite Sputnik orbiting earth

Communication satellites

https://www.youtube.com/watch?v=vFypCugyFoM

Are put in a much higher orbit above the equator ( 35800 km ). It orbits the earth

exactly once every 24 hours. It stays permanently above the same point on the

equator. This is important since satellite dishes pointing towards it to receive

signals do not need to be moved once pointing towards the satellite.

Earth’s gravity holds objects in orbit around it. This communications

satellite sends information all over the world as it orbits Earth.

Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 5

Planets

https://www.youtube.com/watch?v=zcY200C8rtA

A planet is a natural satellite of a star.

There are nine planets in our solar system.

All of the planets in our solar system orbit

the Sun.

The planets themselves do not give out

light.

We can see some of the planets in the night

sky

because they reflect sunlight (like our moon

does).

The planets are so far away that they

appear to us like dots of light.

They look to our eyes like stars.

The orbit of a planet is almost circular.

All of the planets (except Mercury and

Pluto) orbit in the same plane.

The picture above shows the solar system.

The relative size of the planets is indicated

but the Sun is very much larger than shown.

The nine planets are

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.

Mercury is closest to the Sun and Pluto is furthest away.

You can remember the order of the planets by learning

"My Very Elegant Mother Just Showed Us Nine Planets".

The first letter of each word is the first letter of the planet

- try making up your own sentence.

Mercury, Venus, Earth and Mars are called the inner planets.

The inner planets are made from rock with an iron or nickel core.

After Mars there is a belt of asteroids, and then

Jupiter, Saturn, Uranus, Neptune and Pluto are called the outer planets.

The outer planets are mainly hydrogen and helium

with an icy or rocky core.

Pluto is a little different and seems to be more rocky

than the other outer planets.

Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 6

Compare the planets to earth

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto

Mass 0·05 0·8 1·0 0·1 318 95 14·5 17 0·002

Diameter 4·9 12·0 12·8 6·8 143 120 51 49·5 2.3

Orbit

Time 0·24 0·62 1·0 1·9 12 29·5 84 165 248

Distance 58 108 150 228 780 1430 2870 4500 5900

Orbital

Speed 48 35 30 24 13 10 7 5·5 4·8

https://www.youtube.com/watch?v=7NYRVsKAkFM

Mass is given relative to the Earth.

Diameter is given in thousands of kilometres.

Orbit time is given in years.

Distance from the planet to the Sun is given in millions of kilometres.

The distance is an average value for the slightly elliptical orbit.

Orbital speed is given (approximately) in kilometres per second.

Notice that the orbital speed decreases as the distance from the Sun increases.

Is Earth the only planet to have life on it. Is

there life on the other planets?

Use this site or others to discuss the above question:

http://www.enchantedlearning.com/subjects/astronomy/

Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 7

Pluto

https://www.youtube.com/watch?v=FqX2YdnwtRc

Pluto is a dwarf planet that usually orbits past the orbit

of Neptune. It was classified as a dwarf planet in 2006;

before that it was considered to be a planet, the

smallest planet in our solar system. There are many

other dwarf planets in our Solar System. Pluto is smaller

than a lot of the other planets' moons, including our

moon. Pluto has not been visited by spacecraft yet; we

only have blurry pictures of its surface; even the Hubble

Space Telescope orbiting the Earth can only get grainy

photos because Pluto is so far from us. In 2015, a

spacecraft called New Horizons (launched by NASA in 2006) will visit Pluto.

Pluto is about 1,413 miles (2274 km) in diameter. This is

about 1/5 the diameter of the Earth.

Pluto is smaller than the 8 planets in our Solar System.

Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 8

In what galaxy does our sun stand?

https://www.youtube.com/watch?v=xwSQVSlccCg

Our sun stands in the Milky way galaxy. It is a disc

shaped, with spiral arms. It can be seen on a clear

night.

The Sun is one of the million of stars that form the

Milky Way Galaxy. The universe consists of many

galaxies each containing millions of stars.

Light takes more than 10 000 million years to reach

us from most distant galaxies.

How is a star born?

https://www.youtube.com/watch?v=Q7MG-LahuX4

https://www.esa.int/esaKIDSen/SEMY06WJD1E_OurUniverse_0.html Stars form out of clouds of gas and dust. The particles gather together under their own

gravity which makes them concentrated. As it gets more dense, it gets hotter until atoms

fuse together and release more energy. So it gets hotter and brighter. A star is born

How did the universe originate?

Scientists think that the Universe is expanding. Most distant galaxy being 10 billion light

years away and going away from the earth as fast as light. Looking at them , it is as if

looking back in time since light from them takes billions of years to reach us.

What is a light year?

https://www.youtube.com/watch?v=Op3AYaJc0Xw The speed of light through empty space is about 186,000 miles per second (about 300,000

kilometers per second). Astronomers talk about vast distances in space as light-years. A

light-year is how far a beam of light can travel in one year, or about 5.8 trillion miles (about

9.5 trillion kilometers

Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 9

The Milky Way is huge. The entire Milky Way is about 100,000 light-years across.

Astronomers measure great distances in light-years. One light-year is how far light travels

in one year. Light travels extremely fast. A flash of light goes almost 6 trillion miles (10 trillion kilometers) in one year. That’s a 6 with twelve zeroes after it: 6,000,000,000,000!

Even at that blazing speed, it would take a flash of light 100,000 years to cross the Milky

Way.

The bulge at the center of the Milky Way is about 10,000 light-years thick. Our solar

system is about 25,000 light-years from the center of the galaxy.

What are the instruments used to observe the

sky?

Telescope is a wonderful invention in the world of astronomy and science. The word

telescope has a Greek origin and is derived from teleskopos, meaning 'far-seeing'. When you

mention a telescope in every day life, you usually refer to an optical telescope.

Have you ever wondered how telescopes work? Right from astronomy, which perhaps is the

most popular use of optical telescopes, it is also used for different purposes. Your pair of

binoculars, theodolites, spotting scopes, monoculars, camera lenses and even spyglasses, all

use optical telescopes.

Telescopes originated when scientists discovered the properties of light to deviate from its

original path as it passes from one medium to another, also known as refraction. This ability

of a lens to redirect light to a desired point is what lies behind the basic telescopic

invention. Scientists are known to have used lenses with variable diameters and focal

lengths to achieve desired visuals magnification of objects in the universe.

Radio Telescopes:

These telescopes do not use lens or optical device. Radio telescope makes use of radio

signals from different sources in the universe. It all began when Karl G Jansky detected

radio waves from a cosmic source in the central region of the Milky Way Galaxy. Radio

Telescopes help us detect and map waves beyond visible light, which is just a small part of

the Electromagnetic spectrum. Radio Telescopes also follow the same principle of converging

vast range of radio frequency to a point and then using this data to map the sources and

composition of such signals. Telescopes have tremendously contributed to our knowledge and

learning of the universe. With advanced technologies, we have been able to map the solar

system with more precision than ever before

Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 10

History of Telescopes The history of telescope sparkles with different names that eventually lead us to the present day telescope with

ultra-modern features. History reveals that the first telescope could have been the Assyrian lens that was made

using crystal. While discovery of the Visby lenses leads us to believe that the Arabs and Persians were acquainted

with the technology way back in the 10th century. There is also an archaeological evidence of Visby lenses being

discovered in Gotlandia in Sweden. These Visby lenses are dated to the second half of the 11th century. The lenses

have been associated with different ideas like pendants, loupes and also components from an ancient telescope.

Speculations also give way to the possibility that it was imported from the Middle East.

The earliest documented telescope was an invention by Mr. Roger Bacon in the 13th century. A gentleman named

Leonard Digges from England is known to have invented the telescope in 1570s, but the first recorded recognition

came in 1608. A Dutch scientist named Hans Lippershey looked at a church tower through two lenses arranged in

front of each other and saw a magnified image. Unfortunately, Lippershey's model had a poor image quality due to

the bending of light by glass lenses. Interestingly, two other men, Jacob Metius and Zacharias Jansen also claimed

to have invented a telescope during the same time period. The original Dutch telescopes were constructed with a

convex and a concave lens, and failed to invert the image. Facts points to telescopes being made in the Netherlands

since its invention, and later finding its way all over Europe.

In 1609, Galileo Galilei was acknowledged for the invention of the first astronomical telescope. He named it

perspicillum, and telescopium in Latin, and telescopio in Italian. Galileo's telescope made use of a convex object lens

and a concave eye lens, now commonly known as the Galilean telescope. The Galilean telescope is popularly used as a

viewfinder in many basic cameras. From 1610 onwards, he went on to produce a series of similar instruments that

he used for astronomical observations.

Johannes Kepler explained the practical advantages of a telescope made using two convex lenses in a theory in his

book Catopirics (1611). Based upon the principle, the first person to construct a model was Christoph Scheiner who

briefly explained it in his book Rosa Ursina (1630). In 1668, Isaac Newton constructed the first reflecting

telescope that used a concave mirror to collect and focus incoming light. It is also said that later, Johannes Kepler

described in his books Astronomiae Pars Optica and Dioptrice the optics of lenses including a new kind of

astronomical telescope with two convex lenses, a principle that came to be known as the Kepler telescope. The most

recent, optical interferometer arrays and arrays of radio telescopes were developed recently in the 19th century.

Find information about the

Hubble space telescope!!!!!!

Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 11

The Big Bang

https://www.youtube.com/watch?v=faRb8VW13pg

https://www.youtube.com/watch?v=zV6aQbnHSRo&feature=player_embedded

All distant galaxies are moving away from each other as universe expands ( like an inflated

balloon) So billions of years ago, they must have been near to each other. In fact

astronomers think that the universe originated in a big explosion known as the Big Bang.

Evidence of the Big Bang – Red Shift

The spectrum of light radiated from a distant galaxy is shifted towards the red part of the

spectrum. The waves of light from a nearby galaxy or star.

The light waves from a nearby galaxy or star moving away from the earth are longer

because the light source is moving away from us. The faster it moves the longer are the

waves we receive.= shift towards the red ( larger wavelength ).

Conclusion

The further away a galaxy is from the earth, the greater the red shift. This was discovered

by Hubble known as Hubbles’ law. The distant galaxies are all receding from earth.

Summary

http://www.kidsastronomy.com/ The Universe is thought to be expanding . It is thought to have originated 10 billion years

ago by the big bang. This theory is supported by Hubble’s Law. The universe might continue

to expand forever or it might reverse that is pulled back under its own gravity. The red

shift proves that all galaxies are moving away from each other because radiation from them

is red shifted.

There is a lot more for you to read about this

chapter in physics. Go through some magazines,

books and encyclopaedias and the internet. You

can also try on internet. Its amazing how much

theories there is to read about how the universe and

our earth originated!!!!!!!!!!!!

Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 12

Worksheet 8.1 ( annual past papers 2010/.2012) 1.a. Underline the correct answer in each of the following:

i. The Earth is a (planet / moon / star) orbiting the Sun.

ii. The Earth has one natural satellite called the (International Space station /

Hubble telescope / moon).

iii. The Sun is at the centre of our (solar system / universe / galaxy).

iv. The nearest star to the Earth is (Sirius / Mars / the Sun).

v. The Earth spins on its axis once every (12 / 24 / 36) hours.

vi. One theory that suggests that the universe started from a big explosion is

known as (Supernova / Big Bang / Nuclear bomb).(6)

b. Complete the following:

i. One light year is

_____________________________________________________

____________________________________________________________(1)

ii. One advantage of exploring space is

______________________________________

____________________________________________________________(1)

2. Complete these sentences about our solar system.

(i) The sun is a ___________________.

(ii) The Earth takes ________________ days to orbit once around the sun.

(iii) When for some countries it is daytime, for others it is night time. This takes

place because the Earth is ____________________ on its axis.

(iv) Jupiter is a large ___________________ visible from Earth. It orbits the

______________.

(v) Other solar systems within our galaxy are ___________ ____________

away from us.

(vi) Scientists and other people use _________________ to see far away planets.

(vii) What keeps a planet orbiting a star is the force of ____________ between

the planet and the star. (8)

Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 13

Theme 8 – The earth and the Universe

Ms. E. Falzon Ellul B.Sc. P.G.C.E. Page 14