Week 6

How many time zones in Australia and why?

learning intention

I understand how rotation and revolution of planets and moons connect to days and months.
I can explain what time zones are and why they are necessary due to Earth's rotation

success criteria

I can explain how the Earth's rotation creates time zones.
I can calculate times given a time zone map.
I can analyse the geographical, historical, and socio-economic factors that influence the determination and use of time zones, with relevant examples.

Tasks

Investigation Skills

Prac: Calculating Time Differences

Literacy & research

Formative Research Task: Time Zones in China

OPTIONAL

Knowledge & understanding

Days, Months & Years Quiz (optional)

Investigation skills

Understanding Time Zones

Time zones are regions on Earth that have been broken into sections to adopt a standard measure of time. The world is split into 24 time zones, meaning each time zone shows a 1-hour time difference. This explains why, when Australians are getting ready to go to bed, people in other parts of the world, such as the United Kingdom, are only just waking up. For example, when it is 4 p.m. in India, it is only 1:30 p.m. in Iraq. Some countries may also have multiple time zones depending on their size. For example, Canada, which is a relatively large country, is split into six time zones, as can be seen on the world map.

The central measure of time is based on a place in the United Kingdom called Greenwich. This central measure of time is called Greenwich Mean Time (GMT), as it is based in Greenwich, which is usually shown towards the centre of a world map. Since 1972, the standard measure of time has been renamed to Universal Coordinated Time (UTC), however GMT is still sometimes used. The International Date Line (IDL) is another important feature of understanding time zones. The IDL separates one day from the next and is directly opposite from the GMT line on a world map.

World maps often appear to be flat when viewing diagrams, so remember to imagine the map as a sphere. If moving from east to west and crossing the IDL, a calendar day is gained. If moving from west to east and crossing the IDL, a calendar day is lost.

Example Questions

Use the International Time Zones Map to complete the following questions.

a. In which time zone is the Philippines located?

UTC+8.

b. How many hours ahead of UTC is Egypt?

2 hours ahead, since Egypt is in UTC+2.

c. If it is 6 a.m. in the United Kingdom, what time is it in Saudi Arabia?

The United Kingdom is at UTC 0 and Saudi Arabia is at UTC+3 which means that Saudi Arabia is 3 hours ahead of the United Kingdom. Therefore, the time in Saudi Arabia is 9 a.m.

d. What is the time difference between Venezuela and Japan?

Venezuela is at UTC–4 and Japan is at UTC+9. Therefore, there are 13 hours between Venezuela and Japan.

Daylight Saving Time

Some countries also practise Daylight Saving Time, which involves moving clocks forward one hour during certain times of the year. The reason for doing this is to gain more hours of daylight in the evening, whilst losing one hour of daylight in the morning. Locations further away from the equator receive less daylight than those closer to the equator, hence the need to take advantage of extra daylight hours. Daylight Saving is observed in Australia, however only in the states of New South Wales (NSW), South Australia (SA), Australian Capital Territory (ACT), Victoria (VIC) and Tasmania (TAS).

Australian Time Zones

Australia is positioned between UTC+8 and UTC+10 and is therefore divided into three main time zones. The key Australian time zones are:

Australian Western Standard Time (AWST) which is located at UTC+8

Australian Central Standard Time (ACST) which is located at UTC+9.5

Australian Eastern Standard Time (AEST) which is located at UTC+10

This means that Brisbane, QLD is two hours ahead of Perth, WA. For example, if it is 3 a.m. in Brisbane, it is only 1 a.m. in Perth on the same day.

If Daylight Saving is being observed in Australia, the ‘Standard’ is changed to ‘Daylight’ in each time zone name. For example, Australian Eastern Standard Time (AEST) changes to Australian Eastern Daylight Time (AEDT). Since Western Australia does not observe Daylight Saving Time, there is no such thing as AWDT.

Use both Time Zones Maps to complete the following questions.

a. What is the time difference between South Australia and Tasmania, if Daylight Saving Time is not being observed?

b. If it is 2 p.m. (14:00) AEDT in New South Wales, what is the time in Western Australia? Write your answer in 24-hour time.

c. Tash catches a plane from Victoria to the Northern Territory. She leaves Victoria at 8 a.m. AEST and arrives in the Northern Territory at 12:30 p.m. local time. How long was her flight?

Literacy & research

Formative Research Task: The objective of this research task is to investigate the count and distribution of time zones within China, comprehensively analyzing the geographical, historical, and socio-economic factors that have contributed to their establishment.

JUST FOR INTEREST .... (i.e. not in the test)

Orbits determine times

A day (23 hours, 56 minutes and 4 seconds) is the time it takes the Earth to rotate on it's axis once. We call this a SIDEREAL day.

That’s the time it takes for Earth to rotate 360 degrees. So - if you were looking at a star, and it was directly overhead today - then, 23 hours and 56 minutes from now, that star will appear overhead in the same place again.

But because we humans measure our “day” from where the Sun is in the sky rather than some distant star, you have to allow for the fact that we’re moving around in our orbit by about 1/365th of a full orbit every day. That means that the sun appears to travel across the sky 3 minutes and 56 seconds more slowly than a distant star because of our motion around the orbit…and that adds exactly enough to bring the day length to 24 hours. We call this a SOLAR day.

The length of a day on any planet or moon is the time it takes for that planet or moon to rotate on it's axis once.

The Moon takes about one month to orbit Earth (27.3 days to complete a revolution - a SIDEREAL month, but 29.5 days to change from New Moon to New Moon - a SYNODIC month).

As the Moon completes each 27.3-day orbit around Earth, both Earth and the Moon are moving around the Sun. Because of this change in position, sunlight appears to hit the Moon at a slightly different angle on day 27 than it does on day zero ― even though the Moon itself has already traveled all the way around Earth. It takes a little more than two additional days for sunlight to hit the Moon in the same way it did on day zero. This is why it takes 29.5 days to get from new moon to new moon, even though it doesn’t take quite that long for the Moon itself to travel once around Earth.

106_95_MoonRotationSVS.mp4

Because the rotation of the moon around it's axis is also 27.3 days, we only ever see one side of the moon.

A year (365.25 days) is the time it takes for the Earth to orbit the Sun once. The length of the year for any planet is the time it takes for that planet to orbit the Sun once.

A year on Mars is 687 Earth days while a year on Saturn is 29.7 Earth years.

Why do you think all the planets rotate around the sun in a counterclockwise direction?

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