Earth and Moon

Question 1

What is the mean distance that the Earth and Moon orbit the sun.

Answer 1

149 million km (1 Astronomical Unit)

365.256 days (1 year) to complete an orbit

Question 2

What size is Earth compared to the moon?

Answer 2

81 times more massive and 4 times radius

Question 3

How many days does it take the moon to orbit the Earth and what is the mean distance? (sidereal period)

Answer 3

27.3 days, mean distance of 384000 km.

Question 4

Define the sidereal period?

Answer 4

time taken to complete an orbit with respect to the fixed distant stars

Question 5

Why does the separation of the moon to the earth vary from 362000-405000 km?

Answer 5

the orbit is elliptical

Question 6

what else does the moon do every 27.3 days?

Answer 6

rotates on its axis- to keep same face towards us

Question 7

How much does the planes of the Earths orbit around the sun and the moons orbit around the earth differ by?

Answer 7

5 degrees

Question 8

what is the Earths spin axis inclined at and what effect does this have on the moon?

Answer 8

23.4 degrees

moon reaches diff heights in the night sky at diff times of the year

Question 9

when is the new moon visible?

Answer 9

never- moon is same direction as sun

Question 10

when is crescent visible?

Answer 10

west after sunset or in east before sunrise

Question 11

when is the first quarter visible and when does it rise?

Answer 11

rises at midday, sets at midnight
visible in evening as half phase.
moon 90 degree away from sun

Question 12

when is the full moon visible?

Answer 12

throughout night

Question 13

when does full moon rise and set?

Answer 13

rises at sunset

sets at sunrise

Question 14

how far away from the sun in degrees is a full moon?

Answer 14

180

Question 15

When is the last quarter moon visible?

Answer 15

in morning as half phase

Question 16

when does last quarter rise and set?

Answer 16

rise at midnight, sets at midday

Question 17

how far away from the sun in degrees is a last quarter moon?

Answer 17

90

Question 18

how many days does a complete lunar phase take and why?

Answer 18

29.5 days because as moon orbits earth, position of sun changes

Question 19

what is a solar eclipse?

Answer 19

moon passes in front of sun, blocking light from part or all of sun reaching earth.

Question 20

when can a solar eclipse occur?

Answer 20

new moon

Question 21

what is a annular solar eclipse and when does it occur?

Answer 21

sun appears as ring (annulus) moon too small to cover sun

Question 22

what is a lunar eclipse?

Answer 22

moon enters earth shadow cone preventing sunlight reaching moon, Moon turns coppery red, due to sunlight refracted through earths atmosphere.

Question 23

where is a lunar eclipse visible?

Answer 23

anywhere on earth where moon is visible above horizon.

Question 24

when can a lunar eclipse happen?

Answer 24

full moon

Question 25

why dont we have eclipses every month?

Answer 25

because orbit of the moon about the earth is tilted with respected to that of the sun

Question 26

what is a tide?

Answer 26

gravitational force due to a distant object decreases with distance from the object. Body is subjected to stronger pull on side closest to object .

Question 27

what is the difference of gravitational force known as?

Answer 27

tidal force

Question 28

what is the equation for tidal force?

Answer 28

``` Ftidal = 2RGM/d^3 F tidal= tidal force per unit R= body of radius M= another body of mass d= distance ```

Question 29

why does the earth not stretch very much?

Answer 29

moons tidal force | rigid

Question 30

why is earths oceans strongly influenced by moons tidal force?

Answer 30

oceans are liquid and water can flow when force applied to it

Question 31

how are two tidal bulges formed?

Answer 31

the tidal force has a stretching effect along a line between Earth and Moon

Question 32

why does the tidal bulge move around the surface of the earth?

Answer 32

due to earths rotation

Question 33

why does Earths surface experience two high tides and two low tides per day?

Answer 33

bulge generally aligned toward and away from moon

Question 34

what is a spring tide and why does it occur?

Answer 34

when sun and moon are aligned (new moon, full moon) tidal forces of sun and moon add together .

Question 35

what is Neap tides and why do they occur?

Answer 35

when sun and moon are perpendicular to each other. (first quarter, last quarter)

Question 36

what is tidal friction?

Answer 36

when frictional forces occur between water and land causing a lag in ocean bulge which has breaking effect on earths rotation.

Question 37

What effect does tidal friction have?

Answer 37

extracting energy from earth-moon system and expending it as head, Length of day increasing by 1.7 milli-seconds per century and earthmoon separation increasing 3.8cm/year

Question 38

how much more greater does the moon experience tidal force due to the earth than the earth due to the moon? what does this mean?

Answer 38

20x moon slightly elongates along line towards earth and moon rotation rate reduced by tidal forces until equalled orbital period