![Tree through the four seasons](/sites/default/files/styles/resource_card_image_360x300_/public/2019-09/Tree_through_the_four_seasons.jpg?itok=d1-felZQ)
Why do we have seasons?
Backgrounders
Learn why seasons change. Discover how they’re different in the Northern and Southern hemispheres.
![ChaoticMind75 - iStock](/sites/default/files/2019-08/why-is-it-colder-in-the-winter-even-though.jpg)
Why is it colder in the winter even though the Earth is closer to the Sun?
Hands-on Activities
Learn why we have seasons in this hands on activity.
![The planet Mars](/sites/default/files/2019-10/Mars.png)
What is your weight on another planet?
Hands-on Activities
Do you weigh the same on Jupiter as you do on Earth? Learn to calculate your weight on a different planet.
![Wall of clocks](/sites/default/files/styles/resource_card_image_360x300_/public/2019-10/wall-of-clocks-for-time-zones.jpg?itok=eq3iHPZT)
Universal Coordinated Time
Backgrounders
Today, you know it's the same time everywhere in your time zone thanks to Universal Coordinated Time. But when humans used the Sun to tell time, they couldn’t tell time precisely.
![Full moon](/sites/default/files/styles/resource_card_image_360x300_/public/2019-12/full-moon.jpg?itok=NubbtzMy)
Moon: Phases
Picture Collections
8 images of different lunar phases showing the portion of the Moon lit by the Sun as the Moon orbits the Earth and as seen by us on Earth
![Cartoon aircraft in flight](/sites/default/files/styles/resource_card_image_360x300_/public/2019-10/Aircraft_in_flight.jpg?itok=MlDYQ0_o)
Cosmic Radiation and Aviation
Backgrounders
Learn how people came to understand the source of cosmic radiation, as well as how this radiation impacts those who work in and travel on airplanes.
![Sunset over the ocean](/sites/default/files/styles/resource_card_image_360x300_/public/2019-10/sunset_over_the_ocean.jpg?itok=E3X4Zaoi)
Cycle of Day and Night
Lessons
Students explore the cycle of day and night by sorting and classifying pictures, creating images and reading books.
![Jan Cami | Associate Professor, Astronomy Jan Cami | Astrophysicien](/sites/default/files/styles/career_image/public/2148_13.jpg?itok=XxaHKxMZ)
Jan Cami
Career Profiles
Associate Professor, Astronomy