topic 4 Flashcards
what is a sideral day?
the time required for the Earth to rotate once around the sun. its 23 hrs and 56 minutes
how long is synodic day?
24 hrs
Why does the Sun have different heights at noon throughout the year?
Ignoring precession, the Earth is tilted 23.5 degrees in the same direction. As it orbits the Sun this then tilts away or towards the Sun changing the height the Sun appears
When are the two equinoxes?
23rd Sept (Autumnal) and 21st March (Vernal)
what are equinoxes?
he time or date (twice each year) at which the sun crosses the celestial equator, when day and night are of approximately equal length
What is a sidereal month? How long is it?
The time for the Moon to complete one full orbit of the Earth is 27.3 days
. What causes a solar eclipse?
Moon passing between the Sun and Earth
What is a synodic or solar month? How long is it?
Time for the full solar cycle to occur is 29.5 days
What is the difference between a total solar eclipse and an annular solar eclipse?
In a total solar eclipse, the Moon completely covers the Sun, while in an annular solar eclipse, the Moon only partially covers the Sun.
Why is it unsafe to directly look at a solar eclipse with your naked eyes?
The intense brightness of the Sun during a solar eclipse can damage your eyes.
what are sundials and shadow sticks used for?
they indicate the Apparent Solar Time.
How does a sundial function with its metal triangle
Sundials use a metal triangle called a gnomon with the slanting edge pointing to the North Celestial Pole
what is the equation of time?
Equation of time (EOT) = Apparent Solar Time – Mean Solar Time
What does it mean when the Equation of Time (EOT) is positive or negative?
When the EOT is positive, we say that the real Sun is “fast” (faster than the Mean Sun) and when EOT is negative, we say that the real Sun is “slow”.
what is noon in terms of solar time?
In terms of solar time, noon is the moment when the Sun crosses the local meridian and reaches its highest position in the sky (culmination), except at the poles. This version of noon is also called solar noon or high noon.
