1- planet earth

Question 1

what is the earth’s mean diameter?

Answer 1

13 000 km

Question 2

what is the largest terrestrial planet?

Answer 2

earth

Question 3

what shape is earth?

Answer 3

oblate spheroid

Question 4

how is the earth an oblate spheroid?

Answer 4

The polar diameter is smaller than the equatorial diameter by 42km

Question 5

How much of the earth is covered by water?

Answer 5

~70% (71%)

Question 6

what are the earths four major internal divisions?

Answer 6

crust, mantle, outer core, inner core

Question 7

what is the thickness of the earth’s crust?

Answer 7

the earth’s crust ranges in thickness from 0-70km thick

Question 8

what is the continental crust made up of?

Answer 8

low-density rocks such as granite.

Question 9

what is the thickness of the oceanic crust?

Answer 9

up to 10km thick

Question 10

what is the oceanic crust made up of?

Answer 10

denser rocks such as basalt

Question 11

what does the crust float on?

Answer 11

the silicate mantle

Question 12

how much of the Earth’s volume does the mantle made up?

Answer 12

~90% of the earth’s volume

Question 13

what is the state of the mantle?

Answer 13

semi-molten/liquid

Question 14

why do tectonic plates move?

Answer 14

as the upper mantle is semi molten, the thermal convection currents rise and fall, driving the sideways motion of the tectonic plates

Question 15

how hot is the outer core of the earth?

Answer 15

~5000 K

Question 16

what materials is the outer core made out of?

Answer 16

liquid iron + nickel

Question 17

how is the earth’s magnetic field created?

Answer 17

currents of charged particles that flow in the outer core

Question 18

what is the state of the inner core?

Answer 18

solid

Question 19

what is the temperature of the inner core?

Answer 19

~5500 K

Question 20

why is the inner core solid?

Answer 20

high pressure prevents the iron and nickel melting

Question 21

what is latitude measured in?

Answer 21

degrees north or south of the equator.

Question 22

how is longitude measured?

Answer 22

east or west of the prime meridian

Question 23

where is the prime meridian?

Answer 23

In 1884, the meridian passing through the Observatory of Greenwich was globally adopted as the zero of longitude

Question 24

how much is the earth’s polar axis tilted by?

Answer 24

23.5* to the vertical

Question 25

when does the sun lie directly over the equator2

Answer 25

21st june; this is the summer solstice

Question 26

when does the sun lie directly over the tropics of Capricorn (23.5*S)?

Answer 26

21st December; this is also the winter solstice.

Question 27

what are the Arctic and Antarctic Circles?

Answer 27

The Arctic and Antarctic Circles represent the most northen (66.5N) and southern (66.5S) latitudes.

Question 28

why is the atmosphere important?

Answer 28

the atmosphere:
- provides us with oxygen to breath
- absorbs harmful solar UV and X-radiation
- Regulates our planet’s temperature to mean 15*C
- Protects us from most meteoroid strikes

Question 29

what are the drawbacks for the atmosphere?

Answer 29

The drawbacks of the atmosphere are:
- The sky is blue restricting observations to night time
-Light is scattered by oxygen and nitrogen molecules in our air: most scattering occurs at shortest (blue) wavelengths so the sky is blue
- air is in the atmosphere and is continuously in turbulent motion.
Different densities of air ride and fall on a variety of scales causing light to react and change direction as it passes through the different layers making the stars “twinkle”

Question 30

what difficulties are there from observations for astronomers?

Answer 30

some major problems are:
- skyglow is the rusty orange haze caused by lights near urban communities
- Local glare from things like streetlights ruin our dark adaptation

Question 31

what are the two most common elements in the Earth’s core?

Answer 31

Iron and Nickel

Question 32

What are the two most common elements in the earth’s crust?

Answer 32

Silicon and oxygen

Question 33

what evidence is there that proves that earth is a sphere?

Answer 33

• satellites orbit the earth
• ships disappear over the horizon
• the earth casts a curved shadow during an eclipse
• aircraft fly in arcs (not straight lines)
• images of the earth from space

Question 34

what is the polar axis of the earth?

Answer 34

the line around which the earth rotates

Question 35

how much is the earth’s axis inclines to the ecliptic?

Answer 35

66.5*

Question 36

which direction does Right Ascension move?

Answer 36

eastwards