The Scale of Things, The view from Earth, The Earth-Moon-Sun System

Question 1

Define hypothesis.

Answer 1

Collection of ideas that seem to explain what is observed, predictions that can be tested.

Question 2

Define Models.

Answer 2

Hypothesis that have withstood observational and experimental tests explain with maths properties and behaviours of some object or phenomenon.

Question 3

Define Theory.

Answer 3

A set of tested ideas written using math to try explaining how things behave.

Question 4

Define Laws.

Answer 4

Proven theories that have stood the test of time and have broad applicability.

Question 5

What did Eratosthenes measure the circumference of the Earth to be in 200 B.C.?

Answer 5

42,000km

Question 6

What is the actual radius and circumference of Earth?

Answer 6

R: 6371km C: 40,030km

Question 7

How many times of Earth are the following?
-Moon
-Sun
-Jupiter
-Saturn

Answer 7

4 times smaller
100 times bigger
10 times bigger
9 times bigger

Question 8

Define A.U.

Answer 8

Astronomical Unit is defined as the average distance between Earth and Sun. Is 1.5 * 10^8 km

Question 9

Define light year.

Answer 9

Is distance travelled by light in one year. 9.46 * 10^12 km

Question 10

Define parsec.

Answer 10

Distance at which 1AU perpendicular to the observer’s line of sight subtends an angle of 1 arcsec. 3.09 * 10^13 km

Question 11

How did aristarchus measure the radius of the sun and the moon.

Answer 11

radius of sun / distance to sun

By calculating the angle between the Sun and the first or third quarter moon to calculate ratio.

radius of moon / distance to moon

From angle we can get distance to moon / distance to sun = 1/400

Hence radius of sun = 400 radius of moon. We have radius of moon.

Question 12

How many times bigger is the Sun than the moon?

Answer 12

400

Question 13

How can we calculate the radius of the moon?

Answer 13

By calculating how long it takes the moon to cross Earth’s shadow during a lunar eclipse.

Question 14

What is the radius of the Moon and of the Sun?

Answer 14

Moon: 1737km
Sun: 696300km

Question 15

How big is the solar system?

Answer 15

4.5 * 10^9km

Question 16

T or F. All the planets of the solar system could fit within the radius of the orbit between Earth and the moon theoretically.

Answer 16

True.

Question 17

What is the speed of light?

Answer 17

3 * 10^8 ms^-1

Question 18

How long does it take light to travel from the Sun to Earth?

Answer 18

8 minutes

Question 19

How many stars are in the milky way? How far is the solar system from the centre of the milky way?

Answer 19

10^11 stars
2.8 * 10^4 ly

Question 20

T or F. If Earth was flat, daytime and nighttime would be equally long throughout the year.

Answer 20

False.

Question 21

T or F. Daytime / nighttime will happen at the same for everyone on Earth.

Answer 21

True.

Question 22

How many constellations cover the entire sky?

Answer 22

88

Question 23

T or F. Stars in a constellation shape are close together.

Answer 23

False.

Question 24

What angle coverage of the sky is provided by human hand at arms length?

Answer 24

10 degrees.

Question 25

What is diurnal motion?

Answer 25

The moon, planets and stars follow a similar path in the sky from East to West.

Question 26

How do we know that the Earth is moving and not the stars?

Answer 26

Foucault's pendulum

Question 27

Explain foucault's pendulum.

Answer 27

A pendulum swings in a fixed plane relative to the stars due to its inertia. Once set in motion, the plane of swing does not rotate by itself. As the Earth rotates, observers on Earth perceive the pendulum's plane of swing as rotating.

Question 28

Explain the yearly motion of constellations.

Answer 28

As Earth rotates around the sun, the night sky changes slowly over the course of a year. I.e. There are Summer and Winter constellations.

Question 29

What is the celestial sphere?

Answer 29

Is an imaginary sphere expanded from the sphere of Earth to contain all the objects in the night sky.

Question 30

What is the Zenith?

Answer 30

The point directly above an observer on Earth?

Question 31

What is the significance if the North and South celestial pole?

Answer 31

If in Northern hemisphere, stars inside Northern pole never set, stars inside southern pole never rise. Opposite for southern hemisphere.

Question 32

What is a circumpolar star?

Answer 32

A star that never sets below the horizon.

Question 33

How do stars move at? (a) middle northern latitudes (b) north pole (c) the equator

Answer 33

(a) Stars move along paths parallel to the celestial equator. (b) The celestial equator lies all around you at the horizon. Stars move horizontal (c) The celestial equator is a semicircle passing directly overhead, stars move vertically.

Question 34

How do circumpolar stars change?

Answer 34

The rotation axis of Earth is slowly moving with time. This is called precession. (Imagine spinning top, fixed in place at an angle, the direction it points toward changes as it rotates)

Question 35

What is the angle of declination?

Answer 35

Angular distance north or south from the celestial equator.

Question 36

What is the angle of right ascension?

Answer 36

Angular distance from the vernal equinox eastward along the celestial equator up to the circle used to measure its declination.

Question 37

What is the sidereal day?

Answer 37

Time it takes for Earth to complete a full rotation. 360 degrees.

Question 38

What is the solar day?

Answer 38

Time it takes for Earth to rotate about its axis so the Sun appears in the same position.

Question 39

T or F. The sideral day is longer than the solar day.

Answer 39

False.

Question 40

What is the ecliptic plane?

Answer 40

Plane of Earth's orbit around the Sun.

Question 41

From our point of view, what is the ecliptic?

Answer 41

Apparent path of the Sun around the celestial sphere.

Question 42

Why are there seasons?

Answer 42

23.5 degrees tilt of the Earth

Question 43

T or F. The tilt of the Earth is always 23.5 degrees.

Answer 43

False, it wobbles between extreme values.

Question 44

Why is Summer hotter?

Answer 44

Sun is higher in the sky so shaft in sunlight is more concentrated onto a small area, which heats the ground effectively.

Question 45

What are equinoxes?

Answer 45

Points on the ecliptic where the celestial equator and the ecliptic intersect. I.e. The earth is not angled toward the sun.

Question 46

What are solstices?

Answer 46

Points on the ecliptic farthest north (Sun highest longest days) and farthest south (Sun lowest shortest days).

Question 47

What is the dark side of the moon?

Answer 47

Because the rotation of the Moon is synchronized with its orbit around Earth we only ever see one side of the Moon. It is not actually dark.

Question 48

What is the sidereal month?

Answer 48

Time it takes the Moon to complete one full orbit around Earth.

Question 49

What is the synodic month?

Answer 49

Time it takes the Moon to complete one cycle of phases.

Question 50

T or F. The synodic month is longer than the sideral month.

Answer 50

True

Question 51

Why does an eclipse not occur every time the moon passes between the sun and Earth?

Answer 51

The plane of the moon's orbit of the earth is at a 5 degree tilt to the earth's orbit of the sun.

Question 52

What is a lunar eclipse?

Answer 52

Earth comes between sun and moon. The Earth casts a shadow on the Moon.

Question 53

Why does the moon appear red during a lunar eclipse?

Answer 53

The colour red on the Moon is due to Earth's atmosphere which scatters blue light.

Question 54

Difference between penumbra and umbra.

Answer 54

Penumbra leads to partial eclipse. Umbra leads to total eclipse.

Question 55

What is a solar eclipse?

Answer 55

The moon comes between the sun and the Earth. Totality is only seen on a small portion of the Earth.

Question 56

Differentiate between an annular and a total eclipse.

Answer 56

Annular: Moon is farther away and not as big, the moon can't completely cover the sun even in the umbra. Total: Moon is closer and bigger, the moon completely cover's the sun apart from the corona in the umbra.

Question 57

T or F. The existance of solar and sideral days proves the Earth obits the Sun.

Answer 57

False.

Question 58

T or F. At the equinox, the sun rises in the East and sets in the West.

Answer 58

True.

Question 59

T or F. In Summer times in the Northern hemisphere, the sun rises from the North East and sets in the North West.

Answer 59

True.

Question 60

T or F. In Winter times in the Northern hemisphere, the sun rises from the South East and sets in the South West.

Answer 60

True.

Question 61

T or F. During equinoxes, night and day are almost the same everywhere.

Answer 61

True.

Question 62

At what times does the full moon rise?

Answer 62

At sunset.

Question 63

If you see the moon with the right-side lit up in the Northern hemisphere is the moon increasing or decreasing.

Answer 63

Increasing.

Question 64

How can you tell the difference between the two eclipses?

Answer 64

lunar = moon being hid solar = sun being hid

Question 65

A minute of arc is what?

Answer 65

one-sixtieth of a degree

Question 66

T or F. Without travelling to space, you can prove that Earth is round and rotates around its own axis

Answer 66

True

Question 67

T or F. The sky is divided in 88 equal in size regions known as constellations

Answer 67

False.

Question 68

T or F. All the stars that we can see in the night sky without using telescopes are located at relatively small distances to us within the Milky Way (our galaxy)

Answer 68

True.

Question 69

T or F. The declination of a star is equivalent to its altitude over the horizon

Answer 69

False. declination of a star is a fixed value on celestial sphere.

Question 70

If the Moon as seen from Earth is in the waning crescent phase, what Earth phase would be seen from the near side of the Moon?

Answer 70

Waxing gibbous

Question 71

T or F. Total lunar eclipses last longer than total solar eclipses

Answer 71

False.

Question 72

If you were on the Moon and continued to stand at the same location, the daytime sky would be blue, and sunset would occur approximately every 30 days the daytime sky would be black, and sunset would occur approximately every 24 hours the datytime sky would be blue, and sunset would occur approximately every 24 hours sunset would never occur because half of the Moon is always bright and the other half is always dark the daytime sky would be black, and sunset would occur approximately every 30 days

Answer 72

the daytime sky would be black, and sunset would occur approximately every 30 days

Question 73

When are the equinoxes?

Answer 73

Spring March 20th Autumn September 22nd

Question 74

What is the highest declination of the Sun?

Answer 74

23.5 degrees

Question 75

What are the units of right ascension?

Answer 75

hours, minutes, seconds. DEGREES NOT USED!

Question 76

T or F. Constellations whose stars are circumpolar can be seen throughout the year unlike seasonal constellations.

Answer 76

True.

Question 77

T or F. At a given time, a total lunar eclipse is visible only from a small part of Earth's surface

Answer 77

False.

Question 78

T or F. At mid-norther latitudes, the full moon passes higher in the sky in Winter than in Summer.

Answer 78

True.

Question 79

On the first day of spring, in Ireland, the Sun rises?

Answer 79

north of east

Question 80

If the Moon orbited Earth twice as fast but in the same orbe the frequency of solar eclipses would

Answer 80

stay the same