Q 01/05

What is the primary cause of Earth's seasons?

A) The changing distance from the Sun

B) Sunspot cycles

C) Ocean currents

D) The tilt of the planet's axis

Answer · why

D) The tilt of the planet's axis

The axis is tilted about 23.4 degrees to the orbital plane and keeps pointing toward Polaris all year, so each hemisphere takes turns leaning toward t...

Q 02/05

By roughly how much is Earth's axis tilted relative to its orbital plane?

A) 23.4°

B) 28.7°

C) 33.1°

D) 45°

Answer · why

A) 23.4°

Astronomers call it the obliquity of the ecliptic. It wobbles between 22.1 and 24.5 degrees over a 41,000-year cycle, one of the Milankovitch cycles t...

Q 03/05

In which month is Earth closest to the Sun?

A) April

B) January

C) July

D) October

Answer · why

B) January

Perihelion falls in early January and aphelion in July, so distance actually works against the Northern Hemisphere's seasons. The difference in sunlig...

Q 04/05

Why is Earth as a whole slightly warmer when it is farthest from the Sun?

A) The atmosphere traps far more heat in July

B) Solar output peaks every July

C) The Northern Hemisphere has more land, which warms faster

D) Ocean currents reverse direction in summer

Answer · why

C) The Northern Hemisphere has more land, which warms faster

Northern summer coincides with aphelion, and land heats up more readily than sea, so the planet's average temperature ticks up despite the extra dista...

Q 05/05

The word 'solstice' comes from Latin words meaning what?

A) Sun and circle

B) Sun and stand still

C) Longest and day

D) Light and turning

Answer · why

B) Sun and stand still

At the solstices the Sun's daily path reaches its northern or southern limit and appears to pause before reversing. A rare English calque, 'sunstay,' ...