Seasons & Earth's Tilt — Practice · Grade 9 Science

Chapter: Earth, Moon & Solar System

What this practice covers

By the end of Seasons & Earth's Tilt you should be able to:

10 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: axis, tilt, solstice, equinox.

Problem 1

What is the main cause of Earth's seasons?
  1. Earth's distance from the Sun changing
  2. The tilt of Earth's axis
  3. The Moon blocking sunlight
  4. The Sun burning hotter and cooler
Answer and explanation

The tilt of Earth's axis

Earth's 23.5° axial tilt changes how directly sunlight hits each hemisphere across the year — that's what drives the seasons.

Problem 2

When is Earth actually closest to the Sun?
  1. Around June 21
  2. Around September 22
  3. Around early January
  4. Around March 20
Answer and explanation

Around early January

Earth reaches perihelion, its closest point to the Sun, in early January — during Northern Hemisphere winter, which shows distance isn't what causes the seasons.

Problem 3

How many equinoxes occur each year, when day and night are nearly equal in length?
Answer and explanation

2

There are two equinoxes each year — the spring (vernal) equinox and the autumn equinox.

Problem 4

What happens during an equinox?
  1. One hemisphere gets far more sunlight than the other
  2. Day and night are roughly equal length nearly everywhere
  3. Earth reaches its closest point to the Sun
  4. Earth's axis points directly at the Sun
Answer and explanation

Day and night are roughly equal length nearly everywhere

At the equinoxes, Earth's tilt is sideways to the Sun, so sunlight is split roughly evenly between hemispheres.

Problem 5

Explain why sunlight hitting the ground at a direct, high angle heats it more than the same sunlight hitting at a low, glancing angle.
Answer and explanation

Direct, high-angle sunlight concentrates its energy over a small area of ground. Low-angle, glancing sunlight spreads that same amount of energy over a much larger area, so each patch of ground receives and absorbs less energy and heats up less.

Problem 6

Why can Australia have summer when New York has winter? Explain the reasoning in your own words.
Answer and explanation

Opposite seasonal sunlight patterns arise from axial tilt, not separate Sun distances.

The Southern Hemisphere tilts toward the Sun while the Northern Hemisphere tilts away.

This changes illumination angle and day length in opposite ways.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 7

Why does low-angle sunlight warm a given surface less strongly under similar conditions? Show the reasoning, not just the conclusion.
Hints

Seasons oppose across hemispheres despite sharing Earth's Sun distance.

Answer and explanation

The same incoming beam spreads over a larger surface area and passes through more atmosphere.

Problem 8

Does Earth's axis reverse its tilt every six months?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

No. It maintains approximately the same orientation as Earth orbits, changing which hemisphere tilts toward the Sun.

Problem 9

Opposite hemispheres challenge a distance-only explanationOpposite hemispheres challenge a distance-only explanationIllustrative matched-latitude daylight (h)Northern June daylight14Southern June daylight10Northern Decemberdaylight10Southern Decemberdaylight14Opposite hemispheric geometry occurs at the same Earth–Sun distance.
Original illustrative paired-hemisphere daylight durations for conceptual comparison. Exact values depend on latitude, date and horizon/refraction conventions. The chosen matched-latitude example isolates seasonal geometry rather than supplying a local almanac.
Interpret the supplied visual model. Why would “Earth is nearer the Sun, so both hemispheres have summer” fail to explain these pairs?
Answer and explanation

Both hemispheres share the same instantaneous distance but have opposite daylight/tilt effects. Axis orientation and latitude explain that contrast; distance alone does not.

Compare June and December pairs under one shared planet-to-Sun distance at each date. The bars measure daylight duration rather than actual temperature.

Both hemispheres share the same instantaneous distance but have opposite daylight/tilt effects. Axis orientation and latitude explain that contrast; distance alone does not.

Response criteria

  • Read the labeled quantities, reference frame or objects correctly.
  • Explain the relation between the visual evidence and the mechanism.
  • Keep the drawing’s stated assumptions and limits in the conclusion.

Problem 10

Under a simple comparison, two surfaces receive equal absorbed power per square metre, but one receives it for 9 hours and the other 15. Compare energy received and explain why this still does not uniquely fix their temperatures.
Answer and explanation

The second receives 15/9 = 5/3, about 1.67 times the energy per area under the assumptions. Temperature also depends on heat capacity, mass, losses, prior conditions and varying real radiation.

The second receives 15/9 = 5/3, about 1.67 times the energy per area under the assumptions. Temperature also depends on heat capacity, mass, losses, prior conditions and varying real radiation.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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