Earth-Sun-Moon Interactions (Earth, Moon and Sun)

Question 1

What is the order of the moon phases cycle?

Answer 1

New moon, Crescent, 1st Quarter, Waxing Gibbous, Full moon, waning gibbous, 2nd quarter, de-crescent, back to new moon.

Question 2

What is a new moon?

Answer 2

When the moon is aligned with the sun.

Question 3

What is a blue moon?

Answer 3

The second full moon in a calendar month, these are quite rare.

Question 4

Why is it often possible to see the rest of the moon, even during the waxing and waning crescent phase?

Answer 4

Due to Earthshine, the light reflected from the Earth.

Question 5

Why is the lunar month 2.2 days longer than the moon’s orbital period?

Answer 5

This is because when the moon has orbited the Earth fully the Earth itself has moved in its orbit around the sun, so the extra time is needed to bring the moon, sun and earth in alignment once more.

Question 6

How many times further is the distance of the sun than the moon?
How many time larger in diameter is the sun than the moon?

Answer 6

400x for both

Question 7

What is a total solar eclipse?

Answer 7

When the moon passes directly in front of the sun, obscuring light from the sun’s photosphere.

Question 8

What happens during totality of an solar eclipse?

Answer 8

The sky darkens, some of the brighter stars can be seen, the temperature drops and the sun’s corona is visible.

Question 9

What are Baily’s Beads?

Answer 9

Small bright spots of sunlight caused by the Sun’s rays shining through valleys on the moon. These can be seen at the beginning and end of totality.

Question 10

What is the Diamond ring effect?

Answer 10

When only one of Baily’s beads are seen.

Question 11

When do solar eclipses occur and for how long?

Answer 11

When there is a new moon, and they last for a few minutes.

Question 12

Why do solar eclipses not occur every new moon?

Answer 12

The plane of the moon’s orbit is tilted slightly by about 5degrees to the plane of the earth’s orbit around the sun.

Question 13

What is a partial solar eclipse?

Answer 13

When the moon only partly obscures light from the sun i.e. Part of the Earth’s surface lies in the penumbra

Question 14

What is a lunar eclipse?

Answer 14

When the moon is full, and the light from the sun behind the Earth is refracted off the Earth’s atmosphere. This light then shines in the moon.

Question 15

What colour is the moon during a lunar eclipse?

Answer 15

Red/Copper colour because most of the blue earth light is scattered and red light is all that is left. The red light is then refracted by the atmosphere of the Earth and illuminated the moon.

Question 16

How long does totality last for a lunar eclipse?

Answer 16

Between 30 minutes and 1 hour. But the whole eclipse can last several hours.

Question 17

What is a partial lunar eclipse?

Answer 17

This is when the Earth prevents only some of the light from falling onto the moon, the curved shadow of the Earth can be seen on the full moon.

Question 18

What is a sidereal day?

Answer 18

The time it takes the earth to spin from west to east in an anti-clockwise sense if viewed from directly above the North Pole.
This time is 23 hrs 56 mins 4.1s.

Question 19

What is solar day?

Answer 19

This is the time taken for successive crossings of the sun across the observer’s meridian which is 24 hours.

Question 20

Why is there a four minute difference between a sidereal day and a solar day?

Answer 20

During one complete Earth rotation, our planet has moved slightly in its orbit around the sun, it must rotate for an extra 4 min to allow the sun to return to the same position in the sky.

Question 21

Why is the apparent solar time different to the mean solar time?

Answer 21

• The earth orbits the sun in an elliptical orbit (not circular)
• The earth’s polar axis is tilted to the plane of its orbit, causing the sun to be ‘higher’ in the sky in summer compared to winter.

Question 22

What is the Equation of time?

Answer 22

The apparent solar time - the mean solar time (GMT)

Question 23

How many minutes equals 1 degree?

Answer 23

4 minutes

Question 24

What are Aurorae?

Answer 24

Aka Northern and Southern Lights or Aurora Borealis and Aurora Australis. They are green, red and yellow curtains and whirlpools of light in the sky. Only mainly seen in places of high latitudes, and if seen lower, it means solar activity is very high.

Question 25

How are Aurorae caused?

Answer 25

By electrons from the solar wind, that have been accelerated to high speeds in the Earth’s magnetic field, exciting atoms and molecules of oxygen and nitrogen in the upper atmosphere (at heights between 100-1000km). As atoms or molecules de-excite, they emit light at certain wavelengths that are characteristic of the elements concerned.

Question 26

What elements so the different colours in Aurorae correspond to?

Answer 26

Green and Red: Oxygen
Purple and (a longer wavelength) red: nitrogen.

Question 27

What is one lunar month or its cycle of phases?

Answer 27

29.5 days