Week 18 – January 5, 2015
Why does Earth rotate and
what’s the evidence?
(besides watching it from
space ships or satellites)
The sun determines our solar time
everywhere on earth as Earth rotates. Can
you can imagine why we use longitude to
establish time zones?
Read pages 30-31, take notes to figure out
time zones, using Cornell note format.
You need to understand how it works before
creating a time zone wheel in Lab 10
Week 18
TIME ZONES VOCABULARY
 latitude
 longitude
 meridians
 Prime Meridian
 International Date Line
 military time
 time zones & longitude
 time zones & political
boundaries
 Greenwich Mean Time (GMT)
 ZULU [time]
 Universal time
 rotation rate (solar day)
 Rotation rate (land speed)
 rotation direction
 solar day times
 earlier time in day (west)
 later time in day (east)
You should be able to define, provide examples and use these terms.
Check them off as we use them.
REVOLUTION
means to
orbit another
celestial body
23.5o tilt
ROTATION
means to
spin on axis
23.5o tilt
WHY DOES THE EARTH
ROTATE?
http://www.youtube.com/watch?v=fD3P_l2sZFI&list=PL316AE0D3F2E1604C
It’s called a Foucault pendulum
and its evidence for rotation. Here’s how it works.
http://www.youtube.com/watch?v=M8rrWUUlZ_U
Have you ever seen one of these work ?
http://www.youtube.com/watch?v=WZ3bi5IVToE
How does this
photo of an
illuminated Earth &
Moon seen from
space by the
Galileo probe
relate to rotation?
Remember it isn’t just Earth…
Here’s an illuminated Jupiter & one
of its moons seen from space by the
Galileo probe
EVIDENCE FOR
ROTATION
http://www.youtube.com/watch?v=fD3P_l2sZFI&list=PL316AE0D3F2E1604C
1. In which direction does the sun
generally rise each day?
2. In which direction does it generally
set?
3. What does that tell you about the
direction of planet rotation?
What type of motion is this diagram showing?
PROVE IT TO YOURSELF with the globes – counterclockwise
in northern hemisphere and clockwise in southern
hemisphere but always towards the east
Is this evidence for
rotation?
http://www.youtube.com/watch?v=fD3P_l2sZFI&list=PL316AE0D3F2E1604C
Why does the sun generally rise
in the east in the morning and
set in the west at night?
THE EARTH ROTATES TO THE EAST so
the sun appears to move from east to west
across the sky. Try it with a flashlight and globe!
Sun’s illumination of Earth as it rotates
http://www.learner.org/jnorth/tm/mclass/SunriseSetAns.html
REVIEW
HOW DOES ROTATION DEFINE
THE LENGTH OF A FULL
SOLAR “DAY”
(Remember, THIS IS NOT JUST DAYTIME)
WHAT IS ROTATION?
How fast does Earth rotate (spin)
on its axis at the equator?
RATE can be measured in DEGREES of ARC of a CIRCLE
or
using a real world distance like EQUATORIAL CIRCUMFERENCE
(from NASA) of 40,030 km = 24,874 mi
Does Earth rotate at the same rate
everywhere?
 Let’s spin to find out how its rotational speed
varies
 Check this using the equatorial circumference (km)
and a circumference measured on the same
latitude as one of your cities.
 How will you measure your city’s rotation
distance? MODEL
GLOBE
CITY’S LATITUDE
REAL
SCALE
MODEL
CIRCUMFERENCE
LINK - http://www.universetoday.com/26623/how-fast-does-the-earth-rotate/
REVIEW
Do you know why
Polaris is called the
North Star?
More evidence for rotation!
• It’s used to find north in northern hemisphere since
it’s circumpolar (does not appear to move) as Earth
rotates. Causes star trails around it!
We can also use Polaris to find our latitude in
northern hemisphere based on Polaris’ altitude
(angle in sky) above the horizon.
What latitudes do these star trails
around Polaris show?
 Lowest latitude?
 Highest latitude
 Mid-latitude?
ktop.scf
This finally brings us to time zones.
How does rotation relate to your clock?
Week 18
Why is
longitude
the basis
for time
zones
around the
world?
Week 18
Lab – Time Zones
How does local time
around the world
compare to ZULU,
GMT, & Universal
Time in Greenwich,
England at the
Prime Meridian?
Earth rotates
360o /24 hrs
or 15o/hour
Will latitude
or longitude
help us?
Go
How do the straight zones relate to the real world?
What do these zones represent?
Are these time zones really straight in the real world?
Now let’s create our own time
zone wheel and see what time it
is anywhere you want to go!!!
Lab 10 – Time Zones
Once you get the cut-out wheel
and background page together,
get them checked by Ms. C
before you go on.
How times relate to a solar day
I won’t have a “wheel” in the real world…
How do I determine time zones without it?
How many time zones or hours away from GMT
in standard time (not daylight savings time)?
= CITY LONGITUDE
15o per zone
NOTEBOOK KEY IDEAS
EVIDENCE for ROTATION
magnetic field (moving molten material at core)
counterclockwise rotation (northern hemisphere)
clockwise rotation (southern hemisphere)
solar path (east to west)
day and night
rate of rotation
star trails around Polaris
Foucault pendulum
Time zones
LAB CONCLUSION - STRETCH
Lucky you!! For your 16th birthday your parents have
decided to send you snorkeling at the Great Barrier
Reef in Australia! Hope you can swim!
It takes about 36 hours to get there if you are traveling
east. You can’t miss the plane, so at what time would
you have to leave LaGuardia in, NYC (41oN,74oW) to
reach Brisbane, Australia (30oS,153oE) by 14:00?
For both cities be sure to include evidence with your
calculations: latitude and longitude, military time and
clock time, and how many time zones to Brisbane,
Australia from NYC.