
SILO 3.2 (DRAFT) Year 3, Term 2: Satellites Focus: Gravity Scope and sequence: Forces, Friction, Gravity, Heliocentric model
Learning intention: Students explore night and day and seasonal changes in relation to orbiting bodies and then apply this knowledge to global communications and satellites.
Overview: The Earth is a satellite which rotates on its own axis each day while revolving around the Sun each year. Students will come to see how this rotation causes us to experience night and day. The angle of the Earth's rotation combined with its revolution around the Sun is why we experience different seasons throughout the year. This unit also looks at mechanical satellites which are used for global communications.
NSW Syllabus	Australian Curriculum (version 9.0)
"A student describes how contact and non-contact forces affect an object’s motion." (ST2-9PW-ST) "A student investigates regular changes caused by interactions between the Earth and the Sun, and changes to the Earth’s surface." (ST2-10ES-S)	"Students learn to describe the movement of Earth and other planets relative to the sun and model how Earth’s tilt, rotation on its axis and revolution around the sun relate to cyclic observable phenomena, including variable day and night length." (AC9S6U02)

Introduction to satellites

This unit is part of the Machines theme which also includes SILO 4.1 'Simple machines' and SILO 4.2 'Transportation'. A machine is a device that uses power to apply forces and control movement to perform a task. Machines usually involve a system of moving parts designed to make a task easier or to automate a process. Machines can be simple like a lever, or complex like a car.

Communications satellites are also machines but a 'satellite' is an object which orbits around another object. Satellites can be naturally occurring, such as moons and planets, or made by humans such as communication satellites. An 'orbit' is a curved path that an object follows around another object due to gravity. An orbit is a revolution around another object as distinct from rotation which involves spinning around its own axis. The following video (1:50) explains all of this in relation to night and day.

Communication satellites

This animation (0:56) was made by a student in Year 6 and it introduces some of the basics about how communication satellites work.

Contact and non-contact forces

Gravity and air resistance can be taught together as air resistance affects the rate of falling bodies. Air resistance is a type of friction.

'Twirly whirlies' provide a suitable experiment as they are readily available and can be easily modified to promote experimentation. An A4 printable template is available here which will give you six per page. It is recommended that each student receives three each to encourage experimentation.

(Image source: https://au.pinterest.com/pin/503629170801754769/ CC BY 2.0)

This template has three twirly whirlies. Children cut along the solid lines and fold along the dotted lines. Give each child three twirly whirlies and ask them to modify each and then make predictions about how they will fall. For example, attach a big paperclip to Part C for one and a smaller paper to Part C for another.

Friction

The following video (4:15) describes a world without friction.

Gravity

This video (0:47) shows an experiment conducted on the Moon during the Apollo 15 voyage in 1971.

Why does the anti-gravity creature travel up the string instead of down?

The 'anti-gravity creature' appears to defy gravity by climbing up the string rather than sliding down. Build your own 'anti-gravity creature' such as the example shown below.This activity works well with students of all ages.

Materials:

Cardboard
String (must be rough such as common brown string)
Straws (McDonalds thick shake straws work well as they have a wider diameter)
Weights (marbles work well)
Tape (masking tape or magic tape are best because they can be torn easily which can save time)
Icy pole sticks

Tools:

Scissors

Procedure:

Draw a creature with two raised arms, one in each corner. Ensure that generous proportions are used as the creature needs to have a strong frame.
Cut two pieces of straw which are wider than the tape so that no tape protrudes over the ends of the straws.
Attach the straws to the back of the cardboard at 45 degree angles as shown in the diagram above.
Cut out your creature using scissors.
Tape the string to the icy pole stick. It is recommended to use three pieces of tape, one in the middle and one on each side of the stick.
Thread the string through the straws.
Attach marbles to each end of the string.

Tips:

Tape can be put over the straws before cutting each straw piece to ensure that they are wide enough.
Young children might require assistance attaching their straws correctly. This is the most critical part as the angle is very important.
Masking tape is useful as the straws can be easily removed, readjusted and reattached if necessary, even after the string has been threaded.
There are no special knots or tricks required to attach the string to the marbles. Just touch each end of the string to a marble and wrap tape around it.

What happens if you remove the marbles by cutting them off?

Why does this happen?

Why doesn't gravity cause the Moon to collide with the Earth?

Sir Isaac Newton used a cannonball analogy to explain the orbit of the Moon around the Earth as shown in the image below.

(Image source: Brian Brondel CC BY-SA 3.0)

Balanced and unbalanced forces

The following video (2:45) explains how forces are considered to be balanced if an objects remains at rest or at a constant velocity. This is in contrast to unbalanced forces which result in an object changing its velocity (i.e., speed or direction).

Frame of reference

Direction is relative as shown in this video (0:47) where clockwise and anti-clockwise depend on your frame of reference.

The Heliocentric model

The Heliocentric model is that Earth revolves around the Sun. This was a very big idea during the Renaissance (15th and 16th centuries) and in the subsequent Scientific revolution. However, the following video (2:16) featuring Eratosthenes (276 BCE – 194 BCE) shows how the Heliocentric model was discussed much earlier. It is nothing short of remarkable that Eratosthenes was able to measure the circumference of the Earth by applying his geometrical knowledge to astronomy.

Time zones

Because the Earth is spinning on its own axis, the Sun will shine on different parts of the world at different times during a 24 hour period. Accordingly, we use time zones based on the historical convention of calibrating these time zones in reference to Greenwich, England. The following image shows how various places are related to Greenwich Mean Time.

(Image source: https://commons.wikimedia.org/wiki/File:World_Time_Zones_Map.svg)

Sundials

In the animated GIF below you can see that the movement in in a clockwise direction.

(Image source: Willow W CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=3397590)

The following photo has the numbers going anticlockwise. Look carefully for other details in the photo to explain why this might be the case. (Hint: Think in terms of geography.)

(Image source: https://en.wikipedia.org/wiki/Sundial#/media/File:Sundial_in_Supreme_Court_Gardens,_Perth.jpg)

The Coriolis effect

The Coriolis effect describes the pattern of deflection taken by objects not firmly connected to the ground as they travel long distances. This explains why tornadoes spin in different directions in the Northern and Southern Hemispheres as the Earth is moving much faster at the equator than at the poles.

The following video (1:20) involves placing a glue stick on a spinning 'Lazy Susan' to demonstrate the Coriolis effect.

(This idea was from a podcast featuring the award-winning science teacher Brett Crawford, the Lead Science teacher at Warrigal Road State School in Brisbane. Brett received the Prime Minister’s Prize for Excellence in Science teaching. https://www.teachermagazine.com.au/articles/school-improvement-episode-18-supporting-primary-science-teachers?utm_source=Twitter&utm_medium=social%20media&utm_content=social)

Seasons

Life is different at the poles

(Jacobs & Robin, 2016, p. 273)

Rocket science

Rocket science can refer to the engineering behind the construction of rockets or the chemical processes involved in rocket propulsion. We will look briefly at both in this section starting with rocket fuel which often consists of mixing liquid hydrogen with liquid oxygen.

Technically, the following video does not require a risk assessment because we are not suggesting that you attempt to replicate any of the experiments in this video.
One of the presenters also says towards the end of the video, "Do not try this at home".
Do not play with matches.

This video (3:25) does not mention rocket fuel but liquid hydrogen and liquid oxygen are still used in many rockets today and were used in many of the most famous space missions.

The Smithsonian Build the rocket book (Graham, 2017) contains 88 cardboard model pieces to construct a Saturn V rocket. Although The SILO Project does not officially endorse any STEM resources, this product is recommended as it is a fun way to get a feel for how the different sections of a rocket function together. With or without a hard copy of this book, look at the picture of the assembled model on the left of the book cover and notice how the sections get smaller as you look up from the bottom to the top sections of the rocket. Based on this comparison, consider the following three questions.