Topic 4- Time And Earth Moon Sun Cycles Flashcards
(32 cards)
What is the equation for equation of time
EOT = AST - MST
How many minutes does 1 degree equal
4 minutes
What is AST
is apparent solar time it is the time the sun shows in the day we can use a sundial for this
What is MST
Is mean solar time it is the our watches that humans have invented as the sun is an unreliable way to tell time in society
How many minutes can AST be inaccurate
16 minutes
What cause AST to be inaccurate
Caused by earth elliptical orbit and axis of earth
How many times a year is a sundial accurate
4 times
How do you determine the angle of a gnomon on a sundial
The latitude of place
Where does gnomon on sundial point to
NCP
What are the disadvantage of sundial
Useless when no sun
Inaccurate due to the EOT
What day does the summer solstice happen on
21st of june
Where does the sun set and rise on the summer solstice
Sun sets in north west and sun rises in north east
When is the winter solstice
21st December
Where does the sun rise and set on the winter solstice
Sun rises in the south east and sets in the south west
When do the equinoxes happen
21st of March and September
Where does the sun rise and set on the equinoxes
Rises in east set in west
What is a solar/synodic day
Is the time it takes the sun to arrive in the same position as the day before
What is a sidereal day
When we measure the rotation not by the sun but by the stars
How long is a solar/synodic day
24 hours
How long is a sidereal day
23 hours 56 minutes
What method do you use to find your local noon
Shadow stick
If you moon one degree either way of your location the sun will still culminate at midday but your middy will be when
Will be four minutes earlier or late than previous location
What made people convert to MST and why
Trains when they were invented people would fin themselves losing or gaining time when they had reached their destination
When more countries started converting to MST what did they decide
They needed a longitude starting point
