13 astronomy questions

NATS 1740 Assignment

Sun, Earth and Moon System

This assignment requires that you print this file that you answer on the last 2 printed sheets. Staple those 2 sheets together and bring them to class on 26 February.

READ CAREFULLY the description of this work. Remember that Earth orbits around the Sun and Moon orbits around the Earth. The other motion that we are going to consider is the Earth’s spin around its axis. A good idea is to view again the video "Why does the moon change shape? “

The Earth and the Sun: Daily (Diurnal) Motion

Pretend your head is the Earth, and your eyes are you looking up into the sky from Earth’s Northern Hemisphere. Imagine a bright light in the front of the room to represent the Sun. To represent the Earth spinning on its axis, stand up and turn around COUNTER-CLOCKWISE (as seen from above). As you turn, the time of day at the location of your eyes changes. One complete turn of your head (360 degrees) represents 24 hours.

Although the exact rising and setting times (and thus the duration of the day) depend on the time of the year and on the location on Earth, for this assignment we consider the day equally divided by sunrise, noon, sunset and midnight.

Now you can answer question 1, remember that here you are studying the Earth’s daily (24 hours) motion, so that the position of Earth with respect to the Sun can be considered fixed.

1. On your assignment answer sheet, make four simple drawings of the Earth and the light rays from the Sun, clearly showing your location on Earth at sunrise, sunset, noon and midnight. The viewpoint for all drawings should be looking down on the Earth from far above the North Pole. Show the direction in which the Earth is spinning. (Note: in this and following questions some marks will be deducted if the arrows are missing).

The Motion and Phases of the Moon

Now pretend that you have a tennis ball next to your head representing the Moon (Your head and the tennis ball are the same relative size as the Earth and the Moon). We are going to recreate the phases of the Moon (its changing appearance with time) as seen from Earth. When the Moon’s phase is full, its entire surface as seen from the Earth is lit by the Sun.

2. Sketch the relative positions of the Earth, Moon and the Sun rays when the Moon is full. The moon orbits the Earth in the same direction that the Earth spins (see question 1); indicate this direction with an arrow. In a second sketch show the position of Earth, Moon and the Sun rays when it is a new Moon (when none of its surface as seen from the Earth is lit up by the Sun).

3. About what time is it for you when the full Moon is highest in the sky ? For question 3, turn around as you have done in question 1 and find out what time is it for you when the full Moon is highest in the sky (when you are looking at the tennis ball straight ahead).

4. Now turn yourself counterclockwise until the tennis ball is just about to disappear from view; that is, when the Moon is about to set. Based on where the light representing the Sun is located when this happens, about what time is it for you when the full Moon sets?

Third quarter Moon is halfway through Moon’s change from full Moon back to new Moon.

Imagine that you move the tennis ball so that the Moon is at third quarter and hold it in that position. Answer question 5 (do not forget the arrows that show the direction in which the Earth is spinning and the Moon orbiting and the Sun rays) and question 6.

Now hold the Moon in the same place. Turn yourself counterclockwise until you can just see the ball representing the Moon and answer question 7. As before, use the position of the Sun to find out what time is it for you when the Third Quarter Moon sets.

Eclipses

As seen from the Earth:

Lunar eclipse (eclipse of the Moon): occurs when the shadow of the Earth falls on the Moon.

Solar eclipse (eclipse of the Sun) occurs when the shadow of the Moon falls on the Earth.

8. What is the phase of the Moon when there is a lunar eclipse ? (full, new ? )

9. Can you see a lunar eclipse during the daytime? How about at sunset or sunrise ?

As seen from the Earth, an eclipse of the Sun (a solar eclipse) occurs when the shadow of the Moon falls on the Earth. Orient your head and the tennis ball so that the shadow of the tennis ball (the Moon) falls on the Earth (your head).

10. What is the phase of the Moon (full, new ?) when there is a solar eclipse ?

11. Can you see a solar eclipse during the nighttime ? How about at sunset or sunrise ?

The Earth - Moon System: Scale Model

A scale model is smaller or larger than the real thing, but has the same proportions.

The radius of the Earth (half its diameter) is REarth = 6.37 x 103 km and the radius of the Moon is RMoon = 1.74 x 103 km. This ratio, 3.66:1, is about the same as the ratio of the radius of your head to a tennis ball. But how far away from your head would the tennis ball have to be to produce an accurate scale model of the Earth-Moon system? (A scale model is smaller or larger than the real thing, but has the same proportions.)

12: The Moon is located about 3.84 x 105 km from the Earth. How many Moon diameters (diameter=2*radius) is this distance ? So how many moon diameters away from the Earth is the Moon ?

13: If the tennis ball has a diameter of 3.5 cm, how far away from your head would it be in a scale model of the Earth-Moon system? Would it fit in the classroom you’re in ? In question 12 you obtained how many Moons you need to put together to cover the distance between Moon and Earth and now, you assume that your Moon has a diameter of 3.5 cm.

Answers: Name: _____________________________________

Student Number: _____________________________

1. Drawings of the Earth, the Sun’s rays, & you at midnight, sunrise, noon and sunset. (4 marks)

2. Relative locations of Sun, Earth and Moon when the Moon is full, and when it is new: (3 marks)

3. Time of day when full Moon is highest in the sky: __________am/pm (circle one) (1 mark)

4. Time of day when full Moon sets: __________am/pm (circle one) (1 mark)

5. Relative locations of Sun, Earth and Moon when the Moon is at 3rd quarter phase: (2 marks)

6.Time when 3rd quarter moon is highest in the sky: __________am/pm (circle one) (1 mark)

7.Time of day when 3rd quarter moon sets: __________am/pm (circle one) (1 mark)

8.Phase of the Moon for a lunar eclipse. Circle correct phase: full / new (0.5 mark)

9.Can you see a lunar eclipse during the daytime? At sunset or sunrise? (1 mark)

10.Phase of the Moon for a solar eclipse. Circle correct phase: full / new (0.5 mark)

11.Can you see a solar eclipse during the nighttime? At sunset or sunrise? (1 mark)

12.Earth-Moon distance in units of Moon diameters: (2.5 marks)

13.Distance of the tennis-ball Moon from your head in an accurate scale model: (1.5 marks)