A good place to start
Why does the Moon appear to change shape?
Move the Moon around Earth and compare the sunlit part visible from our planet.
Start exploring →Science source: NASAPick up your discovery
Continue →Science Lab
One question.
A whole world to explore.
Start with something you wonder about. Read a little, try the idea and see where it takes you.
Follow the connections
Four journeys. Twenty discoveries. Every topic is open.
1
Earth, Moon and Sun
Follow the light, change your viewpoint and put our Solar System in perspective.
Explore 5 discoveries →2
Our changing Earth
Move tectonic plates, inspect real earthquakes and discover how landscapes change.
Explore 5 discoveries →3
Read the sky
Identify real clouds, follow moving air and distinguish today's weather from climate.
Explore 5 discoveries →4
Water on the move
Follow a raindrop, trace a watershed and explore waves and tides.
Explore 5 discoveries →Choose your next question
Saved experimentsSpace
Earth, Moon and Sun
- What causes day and night?Checkpoint answered
- Why do the seasons change?Checkpoint answered
- Why does the Moon appear to change shape?Checkpoint answered
- Why is there not an eclipse every month?Checkpoint answered
- How big is our Solar System?Checkpoint answered
Sources: NASA
Earth and geology
Our changing Earth
- What happens where tectonic plates meet?Checkpoint answered
- Where do earthquakes happen?Checkpoint answered
- Why do volcanoes have different shapes?Checkpoint answered
- Can one kind of rock become another?Checkpoint answered
- How are weathering and erosion different?Checkpoint answered
Sources: USGS
Weather and climate
Read the sky
- What can a cloud's shape tell us?Checkpoint answered
- Why does the wind blow?Checkpoint answered
- What happens when air masses meet?Checkpoint answered
- Why does rain sometimes arrive as snow or sleet?Checkpoint answered
- How is today's weather different from climate?Checkpoint answered
Sources: NOAA
Water and oceans
Water on the move
- Where can a drop of water go next?Checkpoint answered
- Which river will this rain reach?Checkpoint answered
- How can the ground hold water?Checkpoint answered
- Does a wave carry the same water across the ocean?Checkpoint answered
- Why does the sea rise and fall?Checkpoint answered
Sources: USGS and NOAA
Read it your wayFive reading levels, available without signing in.
Try the ideaChange something. Notice what happens.
Follow the evidenceSpecific NASA, NOAA, USGS and NPS source links in every lesson.
Your discoveries
Saved experiments
Questions you want to come back to, saved on this browser.
No saved experiments yet. Open a lesson and choose Save.