📍W2 L2 - Looking at the sky - Cycles and phases

Question 1

What season did the dinosaur destroying asteroid hit the Earth?

Answer 1

Northern hemisphere spring, Southern hemisphere autumn

Question 2

What is the single eponymous term used for the 3 periodic motion changes in Earth’s orbit?

Answer 2

Milankovitch cycles

Question 3

What is the Earth’s spinning top motion called?

Answer 3

Precession

Question 4

How long does it take for Earth to complete one precession cycle?

Answer 4

26,000 years

Question 5

What is the change in Earth’s axial tilt called?

Answer 5

Change in obliquity

Question 6

How much does the Earth’s axial tilt range between?

Answer 6

22.1’ and 24.5’

Question 7

How long does the obliquity cycle take to complete?

Answer 7

41,000 years

Question 8

What is the change in eccentricity of the Earth’s orbit called?

Answer 8

Elliptical eccentricity

Question 9

Why does the zero point for right ascension change over time?

Answer 9

Earth’s precession

Question 10

What coordinate system do we use at present for alt/azimuth?

Answer 10

J2000

Question 11

What are 2 names for the phenomenon called where the same part of the moon faces Earth?

Answer 11

Tidal locking or synchronous rotation

Question 12

In one sentence, and in relation to the moon, define a sidereal month

Answer 12

One full revolution of the moon relative to background stars

Question 13

How long is a sidereal month

Answer 13

27.3 days

Question 14

Define a lunar month

Answer 14

One full revolution with respect to the Sun to return to the same phase

Question 15

How long is a lunar month?

Answer 15

29.5 days

Question 16

What angle is the moon offset to the ecliptic/

Answer 16

5.2 degrees

Question 17

What is the name for the point in the moon’s orbit where it crosses the ecliptic?

Answer 17

The line of nodes - where lunar orbit crosses ecliptic

Question 18

What is special about the moon sun relationship at the line of nodes

Answer 18

Eclipses can happen

Question 19

What is the name for the period in its orbit when the moon is rising above the ecliptic plane?

Answer 19

Ascending node

Question 20

During eclipse, what is the darkest part on Earth that the eclipse shadow falls on called?

Answer 20

The umbra

Question 21

What is the partial shadow area falling on the Earth during a solar eclipse known as?

Answer 21

The penumbra

Question 22

Is the moon’s orbit circular or elliptical?

Answer 22

Elliptical

Question 23

When viewed from the Earth, what type of eclipse occurs when the moon is far from the Earth?

Answer 23

An annular eclipse

the edge of the sun remains visible around the moon

Question 24

What type of eclipse occurs when the moon is close to the Earth (and between the Earth and the Sun)?

Answer 24

Total solar eclipse

Question 25

What type of eclipse occurs when the Earth is between the moon and Sun?

Answer 25

Lunar eclipse

Question 26

What colour is the moon when it’s eclipsed by the Earth and in its umbra?

Answer 26

Red

Question 27

What duration is the moon’s precession?

Answer 27

18.6 years