ch.1 Flashcards
(28 cards)
What is the celestial sphere?
An imaginary model used to understand the sky and stars
It does not necessarily match physical reality.
What did ancient scientists believe about the celestial sphere?
They believed it revolved around the Earth
They were unaware that it was actually the other way around.
How does the position of stars relate to their visibility?
The higher the stars are in the sky, the smaller the shift appears to the naked eye
Stars directly on the axis of rotation do not appear to move at all.
What are constellations?
Fixed arrangements of stars that resemble animals, objects, and mythological figures
A simpler definition is a group of stars resembling specific shapes.
What was the believed purpose of constellations in ancient times?
They served as tools for tracking the seasons and for navigation
What causes certain constellations to appear during specific seasons?
Earth’s revolution around the sun
What is diurnal motion?
Daily motion caused by Earth’s rotation, where celestial bodies rise in the east and set in the west
What causes the apparent motion of stars in the sky?
The rotational motion of the Earth
This motion is about the north and south celestial poles.
What is annual motion?
Yearly motion caused by Earth’s revolution around the Sun
How much earlier do stars rise each night due to Earth’s motion?
3 minutes and 56 seconds earlier
What is the ecliptic?
The path of the Sun in the sky
This motion is apparent, as the Sun does not actually move.
What causes the seasons on Earth?
Earth’s tilt and revolution around the Sun
What is the tilt of Earth’s axis from the perpendicular to its orbital plane?
23.5 degrees
When is Earth closest to the Sun?
In January
Are the seasons caused by the distance between the Sun and the Earth?
No, they are caused by the tilt of Earth’s axis
What happens during the summer regarding the Sun’s path?
Days are longer because the path the Sun takes is larger
What are solstices?
Times when the Sun rises at the most extreme north and south points
When does the summer solstice occur?
June 21st
When does the winter solstice occur?
December 21st
What are equinoxes?
Times when the Sun rises directly east, causing equal day and night
When do the equinoxes occur?
March 21st and September 23rd
What is the effect of the Sun’s changing position near the equinoxes?
The Sun’s position shifts by almost its own diameter each day
How does the Moon move in relation to the Earth?
The Moon moves from east to west, rising in the east and setting in the west
How long does it take for the Moon to complete a set of phases?
About 30 days
