Earth Motions, Latitude / Longitude, and the Seasons Flashcards
How can you determine your latitude?
By measuring the height (in degrees) of Polaris above the horizon
How does the location of Polaris change as you change your latitude?
- It is at zenith at 90 degrees north
- For each degree of latitude you move south, Polaris also moves that number of degrees south
- Polaris not visible in Southern Hemisphere
Where is Polaris in the skies above:
1) the North Pole
2) Sudbury
3) the Equator
4) the Tropic of Capricorn
5) the Tropic of Cancer
1) 90 above horizon (zenith)
2) 42.4 above horizon
3) 0 (horizon)
4) 23.5 below horizon
5) 23.5 above horizon
How do you determine the antipode of a location?
- Reverse north and south
- Subtract 180 from longitude
- Reverse east and west
What are latitude lines?
- Imaginary lines that go all the way around the world and are a parallel to the Equator
- Run east to west, measure distances in degrees north and south of equator
Where is the highest possible latitude?
North and South Pole
Where is the Tropic of Cancer located and when is the sun at zenith at this location?
- 25.5 N
* Summer solstice (June 21)
Where is the Tropic of Capricorn located and when is the sun at zenith at this location?
- 23.5 S
* Winter solstice (December 21)
Where is the Arctic Circle located? How much sunlight does it get?
- 66.5 N
- Northernmost latitude on planet
- Receives at least one day (24 hours) of continuous night or day
As you go latitudes north of the Arctic Circle, what happens to the number of consecutive days that receive 24 hours of day?
Increases until you reach the North Pole, which experiences 6 months of continuous day or night
Where is the Antarctic Circle located? How much sunlight does it get?
- 66.5 S
- Southernmost latitude on planet
- Receives at least one day (24 hours) of continuous night or day
As you go latitudes south of the Antarctic Circle, what happens to the number of consecutive days that receive 24 hours of day?
Increases until you reach the South Pole, which experiences 6 months of continuous day or night
How many km of distance along the surface of the Earth is 1 degree latitude?
111 km (slightly larger near the Poles- oblate spheroid)
What are longitude lines? (maximum?)
- Imaginary lines that run across the surface of the Earth from the North to South Pole
- Run north to south, measure distances in degrees east and west of the Prime Meridian
- 180 degrees E and W max
Where is the Prime Meridian?
Greenwich, England- 0 degrees
What/where is the International Date Line?
- Halfway around the world from the Prime Meridian (180 degrees)
- Move East across IDL = subtract calendar day
- Move West across IDL = add calendar day
What does the distance between longitude depend on?
- Where you are on Earth
- Equator - 1 degree longitude = 1 degree latitude (111 km)
- Longitude lines converge at the Poles- distance between them decreases as you move North/South
How is the longitude of a place calculated? (in general)
- By determining the solar time at that place and comparing it with the time at the Prime Meridian
- Earth rotates through 15 degrees of longitude per hour
- Noon = sun at highest point in sky for that day
What is your longitude if it is noon at your location and 3:00 pm at the Prime Meridian?
45 W
3 x 15
What is rotation?
Spinning of the Earth on its axis
What is a solar day?
- The time it takes for the Earth to rotate about its axis so that the Sun appears in the same position in the sky
- 24 hours
- The Earth moves a little in its orbit during the time it takes to spin once on its axis
- Turns a little more than 360 degrees
What is a siderial day?
- The time it takes for the Earth to rotate about its axis so that the distant stars appear in the same position in the sky.
- 23 hours, 56 min
What is solar noon?
Sun at highest point in the sky for that day (zenith)
What is the North Celestial Pole?
- Point in space that the Earth’s axis points to
- Stars appear to circle around this point
- Stars complete one rotation around in 23 hours 56 min
How is the longitude of a place calculated? (given local time and GMT time)
GMT - local time = hours
hours x 15 = longitude
Local is ahead of GMT = East
Local is behind GMT = West
How do you calculate the length of the day?
Sunset minus sunrise
How do you calculate the time for solar noon given the times for sunrise and sunset?
1) Length of day divided by 2
2) Add that number to the sunrise time
What is the cause of the seasons and what is the result of the 3 reasons?
1) Tilt of the Earth’s axis
2) Revolution of Earth around the Sun
3) Parallelism of Earth’s axis
Result: one hemisphere receives more direct solar radiation than the other hemisphere (6 months later the opposite)
Why is summer warmer than winter?
When the North Pole tilts away from the sun, the angle of the sun’s rays falling on the Northern Hemisphere is low. As a result, the sun’s rays spread solar energy over a large area, which leads to lower temperatures.
How does sun change over the course of the year in Sudbury? (day length, height of sun, directness of sunlight)
Winter Solstice:
1) Shortest day (8:53)
2) Lowest in sky (24 degrees)
3) Least direct
Summer Solstice:
1) Longest day (15:06)
2) Highest in sky (71 degrees)
3) Most direct
How does the length of day change as you move north or south on a given day? (winter solstice)
In October: as you move north, the length of day decreases and as you move south, the length of day increases
How does the height of the Sun change as you move north or south on a given day? (winter solstice)
In October: sun at zenith at 15 S- the sun gets lower as you move further from the latitude of the sun at zenith
When is the shortest day of the year in the Northern Hemisphere?
Winter solstice (December 21)
When is the longest day of the year in the Northern Hemisphere?
Summer solstice (June 21)
On what date are both day and night 12 hours long all over the Earth?
Fall equinox (September 23)
Why does ‘one year = one day’ at the North Pole?
The sun is visible for 6 months and not visible for the other 6 months because it is within the Arctic circle (66.5 degrees)
What is an equinox?
- The moment when the sun appears to cross the celestial equator
- The sun’s rays strike Earth at a 90 degree angle along the equator
What is the celestial equator?
A line drawn on the sky directly overhead from the Equator of Earth
When is the autuminal equinox?
September 22 or 23- beginning of fall in Northern Hemisphere
When is the spring (vernal) equinox?
March 21 or 22- beginning of spring in Northern Hemisphere
If you were to walk around the room carrying the Earth balloon at a certain tilt, what location in the room would the Earth be at: (sun in center, tilted towards windows)
1) the summer solstice
2) the autumn equinox
3) the winter solstice
4) the spring equinox
5) today’s date
6) perihelion
7) aphelion
1) desk
2) left wall (near door)
3) windows
4) right wall
5) between left wall and windows (middle)
6) between windows and right wall (close to windows)
7) between left wall and desk (middle)
What is the difference between rotation and revolution?
- Earth revolves (orbits) around the sun
- Earth rotates on its axis
How many rotations does the Earth make in
1) one day
2) one year
1) 24 hours- 1 rotation with respect to the sun
23 hours 56 min- 1 rotation with respect to the stars
2) 366.24 with respect to the sun
365.24 with respect to the stars
What astronomical object is the axis of the Earth pointing at?
The North Star (Polaris)
As you look down onto the North Pole of the Earth, in what direction is the Earth:
1) rotating
2) revolving
1) Counterclockwise
2) Counterclockwise
When is Earth’s aphelion?
July 4
When is Earth’s perihelion?
January 4
How to calculate the apparent diameter of Earth as seen from the Sun
apparent solar diameter divided by diameter of sun = apparent diameter of Earth from sun divided by diameter of Earth
What is the shape of the Earth? When did it gets its shape and how?
- Oblate spheroid- diameter through the poles is 42 km less than diameter through equator
- Spinning on its axis makes polar regions flatten and the equatorial zone bulge
What was evidence 2,000 years ago that the Earth was a sphere?
1) Ships appeared to disappear (“sinking”) from waterline to top of mast as ship sails over curve of Earth
2) Shape of Earth’s shadow falling on moon during eclipse (shadow- cone)
3) As you move north and south, the location of the stars change with respect to the horizon
How to calculate distance at aphelion?
apparent diameter of sun at aphelion divided by distance at perihelion = apparent diameter of sun at perihelion divided by distance at aphelion
