Day length and seasons
Explore the influence of seasons on sunrise and sunset times with the FizziQ Junior ephemeris.
Activity Summary
Students use the Sun-Moon ephemeris of FizziQ Junior to find sunrise and sunset times at different dates of the year. Divided into four groups representing each season, they collect and compare data to observe day length variations. They discover the link between Earth's axis tilt and sunshine duration.
Introduction
Have you noticed that in summer it stays light late in the evening, while in winter night falls very early? This phenomenon, which we observe every day, is actually the result of a fascinating astronomical mechanism.
The Earth doesn't just orbit around the Sun: its rotation axis is tilted about 23.5 degrees. This tilt is responsible for seasons and the variation of day and night lengths throughout the year.
Ancient farmers knew these variations well because they dictated sowing and harvest periods. Today, thanks to the FizziQ Junior ephemeris, you can explore this phenomenon by finding the exact sunrise and sunset times for each season. You can then verify for yourself that day length varies considerably between summer and winter, and understand why these changes occur.
Learning Objectives
- Understand that seasons are caused by the tilt of Earth's rotation axis.
- Use the FizziQ Junior ephemeris to find sunrise and sunset times.
- Compare day length between different seasons.
- Interpret observed variations and relate them to Earth's orbit.
- Discuss the impact of seasonal variations on agriculture and ecosystems.
Scientific Concepts
Instruments and sensors
Scientific instruments
- Sun-Moon ephemeris
FizziQ Features
- Experiment notebook — Each group saves a copy of the ephemeris reading for its chosen date, to compare sunrise/sunset times and day length across seasons.
Required Materials
- - Smartphone or tablet with FizziQ Junior - FizziQ Junior experiment notebook - Board for pooling results - Note: the protocol remains adaptable to any comparable ephemeris or astronomical almanac tool.
Experimental Protocol
Present the concept of seasons to students and explain that they are caused by the tilt of Earth's rotation axis relative to its orbit around the Sun.
Divide students into four groups, each representing a season: spring, summer, autumn, winter. Each group chooses a representative date for their season (e.g., the solstice or equinox).
Ask students which FizziQ Junior instrument they could use to know sunrise and sunset times. Guide them to the Sun-Moon ephemeris.
Open FizziQ Junior, access measurement instruments and select the Sun-Moon ephemeris. Explore the information displayed: sunrise, sunset, day length.
Each group finds sunrise and sunset times for their chosen date. Students add a copy of the instrument to the experiment notebook.
Ask them to also determine sunrise and sunset times one week before and one week after their date, to observe the evolution.
On a collective board, create four columns (one per season). Each group reports their data: date, sunrise time, sunset time, and calculated day length.
Ask students to observe variations between seasons. Which season has the longest days? The shortest? Are durations symmetrical between spring and autumn?
Discuss with the class the reasons for these variations: Earth's axis tilt means the Northern Hemisphere receives more light in summer and less in winter.
Summarize conclusions and emphasize the importance of these variations for agriculture, human activities, and ecosystems.
Expected Results
Students will observe that day length varies significantly between seasons. In summer, day length reaches about 16 hours at the summer solstice (in France), while in winter it drops to about 8 hours at the winter solstice. At equinoxes, day length is close to 12 hours.
Students will also notice that sunrise and sunset times change progressively from one week to the next, with faster variations around equinoxes than around solstices. Recorded data may show slight differences depending on the school's geographic location.
Scientific Questions
- Why does day length vary throughout the year?
- What would happen if Earth's axis were not tilted?
- Is day length the same everywhere on Earth at a given date?
- Why don't equinoxes correspond exactly to 12 hours of daylight?
- How do farmers use knowledge of seasons to plan their crops?
Scientific Background
The cause of seasons is linked to the tilt of Earth's rotation axis and its orbit around the Sun. Earth's axis is tilted about 23.5 degrees relative to its orbital plane. This tilt means that throughout the year, both hemispheres receive varying amounts of sunlight and heat.
When the Northern Hemisphere is tilted toward the Sun, it receives more light and heat, causing summer. Meanwhile, the Southern Hemisphere is tilted away from the Sun, receiving less light, causing winter. The situation reverses six months later.
Seasons directly influence sunrise and sunset times. During summer months, days are longer because the hemisphere is tilted toward the Sun. In the Northern Hemisphere, the further north the observer is located, the longer the day in summer. At about 66.5 degrees latitude, the observer experiences a day without night at the summer solstice.
At the equator, day length remains approximately the same all year, about 12 hours. Conversely, during winter months, days are shorter, with later sunrises and earlier sunsets.
Extensions
- Compare data between two cities at different latitudes (e.g., New York and Miami).
- Plot a graph of day length vs. months of the year.
- Study the midnight sun phenomenon in polar regions.
- Observe the variation of sunrise direction using the compass over several weeks.
- Find sunrise and sunset times for the Moon and compare with those of the Sun.
Frequently Asked Questions
Why use the FizziQ Junior ephemeris rather than directly observing the sun?
The ephemeris allows access to data for any date of the year without waiting, and avoids weather-related problems. Also, you should never look directly at the sun as it can damage your eyesight.
Is the ephemeris data accurate?
Yes, the ephemeris calculates sunrise and sunset times from precise astronomical models and the tablet's GPS position.
Why isn't day length exactly 12 hours at equinoxes?
Several factors create a slight difference: atmospheric refraction makes the sun appear before it is geometrically above the horizon, and the sun is not a point but a disk.
Detailed Description
Students use the Sun-Moon ephemeris of FizziQ Junior to find sunrise and sunset times at different dates of the year. Divided into four groups representing each season, they collect and compare data to observe variations in day length. They thus discover the link between Earth's axis tilt, seasons, and sunshine duration, and discuss the impact of these variations on agriculture and ecosystems. FizziQ Junior provides this Sun-Moon ephemeris instrument directly on the smartphone or tablet, along with an experiment notebook in which each group can save and compare their sunrise and sunset data.
Ready to start?
Download FizziQ and try this activity with your students.