Solar altitude and sun path

A spherical sundial with hour markings and a movable gnomon at Green's Windmill, Nottingham. — A working sundial at Green's Windmill, Nottingham. A gnomon's shadow connects the Sun's apparent direction with local solar time.

A suggested lesson sequence

Use these stages at your own pace. Pause for students to sketch, compare observations or lead part of the demonstration.

01
Observe
Locate the horizon, solar path and selected Sun position. Move Local solar time from morning to afternoon and follow the Sun across the sky.
Open Observe
02
Tinker
Change Latitude and Date, then compare the highest solar altitude and length of daylight. Look for a date and latitude with no sunset.
Open Tinker
03
Explain
How do noon solar altitude and day length work together to change the energy received during a day?
Open Explain
04
Check
Choose an answer and explain your reasoning. Each question includes feedback.
Open Check

Rehearse with the model

The same scene and controls as the lab. Load it when you are ready; use Start projector for the full classroom view.

Before the lesson

Compare the Sun’s daily path at different latitudes and explain how the season changes noon altitude and day length.

Open the model before the lesson and choose a view that makes the important feature easy to see. Drag to rotate, and use the on-screen controls to change one variable at a time. The Controls panel explains the available keyboard shortcuts.

Pause the animation at a useful moment. Ask students what should happen next, then play it to test their explanation.

Guide the demonstration

Locate the horizon, solar path and selected Sun position. Move Local solar time from morning to afternoon and follow the Sun across the sky.

Change Latitude and Date, then compare the highest solar altitude and length of daylight. Look for a date and latitude with no sunset.

Discuss a common misconception

“The Sun is directly overhead at local noon everywhere on Earth.” Local solar noon is when the Sun reaches its daily highest position, but that position need not be overhead. Noon altitude depends on latitude and solar declination. The Sun can be directly overhead only between the tropics, and only on dates appropriate to the latitude.

Build the explanation

Solar altitude is the Sun’s angle above the horizon. It changes through the day and year, while latitude determines how high the Sun can climb and whether it rises or sets at all.

Change Latitude and Date, then compare the highest solar altitude and length of daylight. Look for a date and latitude with no sunset.

The model shows geometric solar directions; local terrain and atmospheric refraction can change an observed sunrise or sunset.

Teaching notes

Use geographic north and south when describing the Sun’s path; a magnetic compass may require a local correction.

Explain that an overhead noon Sun is possible only within the tropics.

Compare both noon solar altitude and daylight duration when changing the latitude or season.

Check understanding

Open Check for 4 questions. Ask students to explain their choice before revealing the answer.

Return to the opening photograph. Ask students to identify one visible feature and explain which part of the model helps account for it.

Look more closely

Use these observations to connect the vocabulary to features students can identify.

Declination

Meteosat view of Earth's day–night boundary on the December solstice, with more of the Southern Hemisphere in daylight. — Meteosat-9 observed this day–night boundary on 21 December 2010. Earth's tilted axis puts the subsolar point south of the equator and gives southern latitudes longer days. Declination is the Sun's angle north or south of the equatorial plane; the tilt of the boundary is observational evidence, not an angle scale.

Read the definition

Tropics

NASA Blue Marble satellite composite of Earth in an equirectangular global map. — NASA Blue Marble monthly composite in an equirectangular latitude–longitude grid. Latitude measures angular distance north or south of the equator; parallels run east–west. The geographic reference lines are mathematical, not marks on the land.