Unit 2 - The Earth in the Universe

Key concept - Systems - How do different systems interact on Earth, in the solar system and in the universe?

Related concepts - Models and environment - How can we use scientific models to explain events and predict future events? 

Global concept - Orientations in time and space - Why is the position of Earth in the solar system essential for our survival?
Unit 2 Keywords
  • Big Bang
  • Geocentric
  • Heliocentric
  • Universe
  • AU
  • Seasons
  • Satellites
  • Light-year
  • Galaxy
  • Nebulae
  • Star
  • The Solar Sytem
  • Tides
  • Eclipse
  • Planets
  • Asteroid belt
  • Dwarf planet
  • Revolution
  • Rotation
  • Axis
  • Lunar
  • Solar

Task guide
The tasks and questions on the Weebly will be coloured to represent the different style of questions that you will find in your exams. The task should be completed in your "Natural Sciences" GoogleDrive document.

Green -   Explaining scientific knowledge
Orange - Applying scientific knowledge and understanding
Red -     Analysing and evaluating information

There will also be "extension" tasks for students who finish tasks quickly! Also look out for links to interactive resources and videos.

Theories of the Universe

Since ancient times humans have wondered about the characteristics of the Earth and its place in the universe. However the ideas were mostly stories or speculation until thinkers and philosphers started putting observations and measurements together to make theories. 
​
For example, although the Earth may appear flat in our everyday experience. The ancient greeks were able to prove that it was sphere using observations that anyone today can do. 
After it had been proved that the earth was a sphere, the next problem was to work out where it was in space and how it related to the bodies in the solar system. Two main theories were formed:
Picture
THEORY 1 - The first well known theory of the universe was described by Aristotle in 384 B.C. and then developed by Claudius Ptolemy in 100 A.D. 

This theory states that The Earth was the centre of the universe and all the planets, The Sun and the stars rotate around it. This is called the geocentric theory because the prefix "geo" is to do with The Earth.
Picture
THEORY 2 - Over 1000 years later, Nicolas Copernicus developed the heliocentric theory. This states that the Sun is at the centre of the universe with the planets rotating around it. At the other stars are around the outside but not moving.

Galileo Galilei and Johannes Kepler verified it with other observations. (You do not need to know the names of the scientists)

Task 1a
1. How many words can you think of beginning with "geo"?
​2. How could "helio" be related to the sun?
3. Why was the heliocentric theory unpopular at first? 

Extension: Imagine you are Nicolas Copernicus and write a letter to convince your fellow Scientists about your observations.
Task 1b extension: Use these comic templates to tell the story of Galileo's discoveries.
OR
Design your own comic. 

The Solar System

Definition - The solar system is the group of planets, dwarf planets, satellites, asteroids and comets which regularly orbit the Sun.    (Barrio Gómez de Agüero, 2011)

Watch the video to the right -->

As you saw in primary, our solar system is made up of several different different things. 

You will need to be able to describe its composition and explain various facts about them. You will NOT need to remember all the individual facts about each of the planets!
Task 1c: Complete the pratice exam questions below:
  1. There used to be 9 planets in our Solar System, now there are only 8. Explain what happened to the 9th planet?
  2. ​Describe 3 differences between the terrestrial planets and the gas giants.
  3. Explain why do the inner planets have higher average temperatures than the outer planets?
  4. Explain which planet would take the longest to revolve around the Sun?
  5. Explain why do the bigger planets usually have more moons that the smaller ones.
  6. Explain why is Jupiter useful for the safety of the Earth?
  7. Which other planet would be most suitable for humans to live on? Explain your answer.
  8. Venus has an atmosphere made of 97 % carbon dioxide compared to 0.1 % on Earth. Explain why this makes Venus a much hotter planet?​
ACTIVITY: 
DESIGN A POSTER OF THE SOLAR SYSTEM WITH THE SIZES OF THE PLANETS IN SCALE (THE DISTANCES BETWEEN THEM YOU CANNOT DO IN SCALE)
1. USE THIS CALCULATOR TO CALCULATE THE DIAMETER OF EACH PLANET
2. DESIGN A POSTER IN WHICH THE PLANETS ARE IN SCALE IN RESPECT TO THE SUN AND ADD INFORMATION ABOUT THE PLANETS (DENSITY, ATMOSPHERE, GRAVITY, TEMPERATURES, LENGTH OF DAYS AND YEARS ETC., AND THE DISTANCE BETWEEN EACH.
Task 1d: Criterion C practice: Use the information below to create a scatter graph about the distances of each planet from the Sun and the surface temperatures that they have.
Making a graph hints:
  • Use a sharp pencil
  • Make a line graph NOT a bar chart 
  • Add a line of best fit (línea de tendencia) that most accurately fits your data.
  • Add a title - Graph to show...
  • Label the axes with units.
  • When it has been checked by your teacher, you can take a photo of the graph and paste it into your NSD.
Under the graph write a conclusion using the following questions to help you:
  1. What does the line of best fit show about the distance compared to the surface temperature? Why is this?
  2. Are there any planets that do not fit the trend? Why is this?
  3. Why is Earth´s distance from the Sun important for life?
  4. Which other planet might be able to support life? Explain why?
Homework: Choose one of the 8 planets and imagine that you are on holiday there! Write a postcard back to your family in Seville describing the holiday. Include interesting facts and possible activities that you have been doing.

Where did it all start?

In your "Natural Sciences" Word document copy and paste the sentence below (in green) and then complete the task:

​Task 1e: Write down as many things as you can about how the universe was created.

Now watch the video to the right -->
(YouTube, 2015)
The Hubble Deep Field Photo (Boyle, 2014)

What is the Big Bang theory?

Looking out into space, we can see that all stars and galaxies are actually moving away from each other. This suggests that the Universe must be expanding.

If we were to reverse time then we would see everything moving together until . . .

. . . at some point everything must have been found in a single point. 
This suggests that there must have been some kind of explosion which created the universe from a single point. We call this The Big Bang. Click on the photo above to see a video showing the futhest stars that we can see. They are 13 billion light years away!
Task 1f 
  1. Add 2 more things you now know about the Big Bang.
  2. State how old the universe is?
  3. Describe what would happen if we reversed time
  4. Explain why are the words "big" and "bang" strange to use for this theory?
Extension: Explain what cosmic background radiation is and how it supports the Big Bang theory?
(Amazing-space.stsci.edu, 2015)
(Amazing-space.stsci.edu, 2015)

What can we find in our Universe?

Task 1g: Use the internet to find a definition of the following things:
  • Galaxy
  • Nebulae
  • Star cluster
  • Milky Way

This image is of a nubula called the "Horsehead Nebula" because it looks like a horse!!!

(Nasa.gov, 2015)
Task 1h: Copy and paste the images below next to the correct name in your NSD, in order of size. Start with the smallest!

What is a star?
Stars are large balls of gas - mainly hydrogen and helium - that are releasing lots of heat and light energy due to chemical processes.

You may have noticed that in some of the images above, the stars are different colours. The colour are shown to the right and they depend mostly on the temperature of the star.

The star in our solar system is called the Sun.

The temperature on the outside of the Sun is about 5500 ºC but in the middle it is 15,000,000 ºC.!

How big is the universe?

Interactive: HOW BIG IS THE UNIVERSE???    
The furthest that our telescopes allow us to see is about 13.8 billion light-years. We call this the observable universe because this is the maximum that we can see. However, because we know the universe is expanding, the actual universe must be bigger than this.
What units of distance do we use in space? It would be ridiculous to use normal units of distance such as metres and kilometres as the numbers would be so big.


For example, the distance between Earth and Mars in metres would be 4,700,000,000,000. 


To avoid these large numbers we use astronomical units (AU) and light-years (ly).
  • 1 AU = 150,000,000 km (approximately the distance between the Earth and the Sun)
  • 1 ly = This is the distance that light can travel in 1 year. Approximately 9,460,800,000,000 km!!!
Example distances:
Sun --> Jupiter   5.19 AU
Diameter of The Milky Way   100,000 ly
DIstance to furthest known star   13,800,000,000 ly
A metro map of The Milky Way. Unfortunately the time between stations would be a bit longer than in London! (Blog.visualmotive.com, 2009)
Task 1i:
  1. State which units would be best for measuring the distances between galaxies? Why?
  2. State which units would be best for measuring distances in our solar system?
  3. Calculate which the longest distance is - 1 light-year or 100,000 astronomical units?
  4. The distance between the Earth and the Sun can also be described as 8 light-minutes. Write a definition for a light-minute.

The movements of the Earth

We will consider the 2 main movements of Earth:
  1. Rotation - This is the movement of Earth around its own axis. The Earth makes a complete rotation once every 24 hours and this is responsible for day and night. The Earth´s axis is tilted at an angle of 23.5 º and this affects the length of days and nights, depending on location.
When a location is in the path of the Sun´s rays then it experiences daytime. When it is on the opposite side of Earth then it will be in night. The tilt of the Earth means that the length of day and night can vary.
Interactive - Day and night simulation
2. Revolution - The Earth also moves in an elliptical orbit around the Sun. This movement, with the tilted axis of Earth, is responsible for the seasons we experience. 
In the nothern hemisphere...
When the Earth is tilted towards the Sun (as in the diagram to the right), the same number of Sun´s rays are falling on a smaller area of the Earth´s surface. this can be seen in the length of the red lines in the diagram. 

This means that more heat and light energy is received in the northern hemisphere and therefore we have summer.

In the southern hemisphere...
As the Sun´s rays are more spread out on the Earth´s surface they receive less heat and light energy. This is called winter.
As the Earth revolves around the Sun, the northern hemisphere will gradually end up pointing away from the Sun. This reverses the seasons.

The points in between summer and winter are when the tilt of Earth is not pointing to or away from the Sun.

Summer --> Autumn --> Winter --> Spring


NOTE: The seasons are not caused by the distance from the Sun!!!
Task 1j: Research challenge!!! Find a photo (and name of) of the following:
  1. The most northern city on Earth (also write the name).
  2. The driest place on Earth.
  3. Showing a picture of the Sun at midnight.
  4. An animal that lives near the South Pole.
Extension questions: Use the map to state which of these countries lie on the equator: Venezuela, Gabon, Tanzania, Indonesia and Hawaii.

How does the orientation of the Moon affect us on Earth?

Can you state any phenomena on Earth that are caused by the Moon?

A satellite is an object that has an orbit around something else. For example, the Earth is a satellite of the Sun. The Earth also has its own satellite that we call The Moon.

The moon was created by a collision between 2 planets that caused one large piece of debris that became the Moon. The rest of the debris reformed the planet we now call Earth.

(Astronomy.nmsu.edu, 2015)
Task 1k:
  1. Which force pulled the debris back together to form The Earth?
  2. Make a pie chart about the chemical compostition of Earth and then make one for the Moon using the data to the left.
  3. Explain how this helps scientists work out that the Moon and Earth were formed from a collision.
Extension: Which gases in the Earth´s atmosphere are most important for life? Why? Do any other planets have these gases in their atmospheres?
The Moon revolves around the Earth once every 28 days. It also rotates around its own axis once every 28 days. 
Interactive simulation - The movements of the Moon
As the Moon does not produce any light, we can only see the part of it is reflecting the Sun´s light. This means that we see a variety of shapes as it revolves around Earth. 
The phases of the moon 
Task 1l:
  1. Which phase of the Moon reflects the most light towards Earth? Which phase the least?
  2. Mr Rouf has said that the use of paper is "waning" in our school. What does he mean by this and why? Use the word "waxing" in a sentence.
  3. Why can we only see one side of the moon, no matter where we are on Earth?
  4. What caused the large craters that you can see on the moon?
  5. How did the Moon cause this boat to become stranded?

Tides
The gravity of the Earth keeps the Moon in a permanent orbit. The gravity of the moon, however, also has an effect on the Earth. As it revolves around the Earth, its gravity causes the oceans to bulge towards itself. This causes a high tide (marea alta).
See how tides work in this simulation. 

When a changing tide is particularly strong it can actually form a wave that travels UP a river. This is called a tidal bore. This video shows surfers on a tidal bore.
For the places that are at the side of the Earth they have a low tide.

Why does the water "bulge" the opposite side of the Earth as well?

The gravity from the Sun can also make tides bigger or smaller. It the Moon and Sun are aligned then we get even higher tides. If they are not aligned then the tides are smaller.
(Dickinson & Dickinson, 2011)

Eclipses

How is this photo related to eclipses?
As the Moon revolves around the Earth, it sometimes blocks our view of the Sun and sometimes is hidden in Earth´s shadow. When this happens we see an eclipse.

There are 2 types of eclipse depending on where the Moon is: A lunar eclipse or a solar eclipse.

Solar eclipse

A solar eclipse is caused when the Moon is positioned between the Sun and the Earth. 

This means that in a small area on Earth´s surface, the Sun is completely blocked from view. This is a total eclipse. Other parts of the Earth´s surface will experience a partial eclipse if the Sun is only partially blocked. Some places may not experience any eclipse.

Remember that most diagrams you see are not to scale! The table and drawing below show a more realistic scale:
(Patrickelwoodeclipse.wikispaces.com, 2015)
ECLIPSE SIMULATION: Click on this link 

Lunar eclipse

Normally when the Moon is the opposite side of the Earth, we see a full moon as we see the reflection of the Sun´s light off the full half of the Moon. Sometimes, however, it passes through the Earth´s shadow. In this case, the Moon will not reflect any light and so looks as if it is disappearing (as in the photo on the right).
(Gallery4share.com, 2015)
(Space.com, 2015)
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