The Earth

Question 1

What features distinguish Earth from other planets?

Answer 1

Water
Atmosphere
Oxygen

Question 2

Why does the Earth have a blue sky?

Answer 2

Red, orange, yellow and green light carries straight on through this atmosphere but blue, violet and indigo get bounced around from molecule to molecule. Blue is a more dominant colour so we see blue instead of purple colours.

Question 3

Demonstrate an understanding of the benefits of the Earth‘s atmosphere to humankind.

Answer 3

Benefits of Earth’s atmosphere
Oxygen allows humans and animals to breathe.
The atmosphere protects us from harmful ultraviolet radiation from the Sun
Makes the climate and temperature of Earth consistent
The atmosphere spreads out and scatters light from the Sun
Protects us from micro meteorite collisions from space

Question 4

What are some of the major causes of light pollution?

Answer 4

Street lamps
Neon Billboards
Volcanos
Manufacturing facilities

Question 5

Describe how Eratosthenes made the first accurate calculation of the circumference of the Earth.

Answer 5

He learnt that in the town of Syene, to the south, the Sun appears at the zenith (the highest point in the sky) on the summer solstice – it was well know that its reflection could be seen directly down a deep well.
By observing and measuring shadows in Alexandra, he calculated that the Sun was over 7.12 degrees from the Zenith on the same date. This is approximately 1/50th of a circle. The distance between the cities was approx 5000 stadia (back then they measured by stadia – like football pitches are used to quickly illustrate lengths). Eratosthenes made a calculation by multiplying the distance by the angle.

Question 6

What shape is the Earth?

Answer 6

An oblate spheroid.

Question 7

What is the Earth’s diameter?

Answer 7

13 000 km

Question 8

How do we know that the Earth is spherical?

Answer 8

Boats disappear over the horizon bottom up.
Lunar eclipses show the curved shape of Earth.
Photographs from space.
Satellites orbit the Earth.
Planes travel in an arc to get to their destination as quickly as possible.

Question 9

What is the rotation period of the Earth.

Answer 9

23 hrs 56 mins.

Question 10

How long does it take the Earth to rotate 1 degree?

Answer 10

4 mins.

Question 11

What is the equator?

Answer 11

An equator is an imaginary line around the middle of a planet or other celestial body. It is halfway between the North Pole and the South Pole, at 0 degrees latitude.

Question 12

What are the tropics of Cancer and Capricorn?

Answer 12

The Tropic of Cancer is the circle marking the latitude 23.5 degrees north, where the sun is directly overhead at noon on June 21, the beginning of summer in the northern hemisphere. The Tropic of Capricorn is the circle marking the latitude 23.5 degrees south where the sun is directly overhead at noon on December 21, the beginning of winter in the northern hemisphere.

Question 13

What is the definition of latitude?

Answer 13

The angular distance of a place north or south of the earth’s equator, or of the equator of a celestial object, usually expressed in degrees and minutes.

Question 14

What is the definition of longitude?

Answer 14

The angular distance of a place east or west of the Greenwich meridian, or west of the standard meridian of a celestial object, usually expressed in degrees and minutes.

Question 15

What is meant by the term pole?

Answer 15

The pole is a point on the surface of the Earth at the axis of rotation, and both poles are located at 90° from the Equator.

Question 16

What is meant by the term horizon?

Answer 16

The Horizon is the furthest visible point of the Earth’s surface from the observer’s position.

Question 17

What is meant by the term meridian?

Answer 17

An imaginary line intersecting the Pole to the observer’s zenith.

Question 18

What is meant by the term zenith?

Answer 18

he Zenith is a point directly above the observer’s head.

The opposite of Zenith is the Nadir, the point directly below the observers feet.

Question 19

Demonstrate an understanding of the drawbacks to astronomers of the Earth‘s atmosphere.

Answer 19

The atmosphere holds in some greenhouse gases that retain the heat of the Sun. These are necessary for life to continue on Earth however gases made as a result of human actions are causing the atmosphere to heat up which causes climate change. Clouds regularly obscure good astronomical viewing. The atmosphere refracts light which means the position and clarity of star viewing is less accurate. Pollution from light and chemicals obscure observations. The atmosphere reflects most radiation making observations at some wavelengths weaker.

Question 20

What are the features of refracting telescopes?

Answer 20

A convex lens is used at the end of a tube to bring an image into focus at a point. Another convex lens called an eyepiece is used at the opposite end of the tube to magnify the image. The lens is typically made of glass coated in a film to allow less light to be reflected and more to pass through the lens.

Question 21

What are the features of reflecting telescopes?

Answer 21

A reflector collects light at one end of a tube and reflects it off a concave mirror. It is brought to a focus by a secondary mirror further up the tube at a 45 degree angle which is then magnified using an eyepiece.

Question 22

Why are the largest telescopes reflectors?

Answer 22

Higher resolution can be acheived with a smaller tube. Refractors suffer from chromatic aberration. This means that colour can sometimes be warped. Refractors suffer from lens sagging. The weight of the lens is supported by the edges and gravity distorts this. The maximum size refractor can be up to 1 metre wide.

Question 23

What are the Van Allen belts?

Answer 23

The outer belt is located 5,000 to 6,000 km from the Earth and contains electrons from the Sun. The inner belt is located between 1,000 to 3,000 km away and contains trapped protons. It deflects the damaging effects of the solar wind. Some of these charged particles get trapped the Van Allen Belts.