Unit 13: The Solar System and Space
The moon's changing face, the planets circling the sun, and everything farther out — stars, galaxies, and the missions sent to explore them.
10 topics · 32 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
The Moon and Its Phases
- How it worksHow does the changing angle between the sun, moon, and Earth create the full cycle of moon phases?
- How it worksWalk me through the moon's phases seen from above its orbit and from the ground at the same time.
- Common mistakeWhy doesn't the moon have a permanent dark side that never sees any sunlight?
- Going furtherWhat happens to the moon phase you'd see if you could stand on the far side of the moon instead of Earth?
Your turn1 of 2
Why does the moon seem to change shape every single night over about a month?Eclipses
- How it worksHow does the moon lining up exactly between the sun and Earth block sunlight during a solar eclipse?
- How it worksWalk me through how Earth's shadow falls on the moon during a lunar eclipse.
- Common mistakeWhy isn't a lunar eclipse just the moon going into a phase the same way a normal phase works?
Your turn1 of 2
The moon orbits Earth roughly every month. Why doesn't a solar eclipse happen every single month, then?Tides
- How it worksHow does the moon's gravity pull ocean water into a bulge that creates high and low tides as Earth spins?
- Worked exampleFind how many high tides happen in one day if the ocean rises and falls roughly every 12 hours.
- Common mistakeWhy isn't the sun's gravity too weak to affect tides at all, even though the moon has the bigger pull?
Your turn1 of 2
Find how many high tides happen in 70 hours if the ocean rises and falls roughly every 12 hours.The Solar System: An Overview
- How it worksHow does the sun's gravity keep every planet locked into an orbit instead of drifting away?
- Worked exampleFind how many Earths could fit side by side across Jupiter if Jupiter's diameter is about 11 times Earth's.
- Common mistakeWhy isn't the solar system laid out with planets evenly spaced apart from each other and the sun?
Your turn1 of 2
Find how many Earths could fit side by side across Jupiter if Jupiter's diameter is about 12 times Earth's.Rocky Planets vs. Gas Giants
- How it worksHow does distance from the sun's early heat explain why small rocky planets formed close in and huge gas giants formed farther out?
- Common mistakeWhy doesn't a gas giant like Saturn have a solid surface hiding somewhere beneath its clouds?
- Going furtherWhat happens to a spacecraft that tries to fly straight down into Jupiter's atmosphere?
Your turn1 of 2
Why could you never actually stand on the surface of Jupiter the way you can on Mars?The Sun
- How it worksHow do hydrogen atoms fusing together at the sun's core release the energy that reaches us as light and heat?
- Common mistakeWhy isn't the sun actually on fire the way a burning log is?
- Going furtherWhat happens to Earth's temperature the moment the sun's output changes even slightly?
Your turn1 of 2
Why does the sun keep shining for billions of years without ever burning up like a campfire does?Stars
- How it worksHow does a star's true brightness and its distance from Earth both change how bright it looks from here?
- Worked exampleFind how many years light takes to reach us from a star 4 light years away, if light travels 1 light year every year.
- Common mistakeWhy isn't the North Star actually the brightest star in the whole night sky?
Your turn1 of 2
Find how many years light takes to reach us from a star 697 light years away, if light travels 1 light year every year.Galaxies
- How it worksHow does gravity hold hundreds of billions of stars together in a swirling galaxy shape?
- Common mistakeWhy isn't the Milky Way the only galaxy in the entire universe?
- Going furtherWhat happens billions of years from now when the Milky Way and the Andromeda galaxy eventually collide?
Your turn1 of 2
Why does our entire sun and solar system count as just one tiny speck inside the Milky Way?Gravity in Space
- How it worksHow does an orbiting spacecraft's constant forward motion combined with Earth's pull create a permanent free fall that never lands?
- Common mistakeWhy isn't there actually zero gravity in low Earth orbit, even though everything appears to float?
- Going furtherWhat happens to a satellite's orbit if its forward speed suddenly drops?
Your turn1 of 2
Astronauts float around inside the space station even though gravity is still very much acting on them there. How does that actually work?Space Exploration
- How it worksHow does a rocket use massive amounts of fuel just to reach the speed needed to escape Earth's gravity?
- Common mistakeWhy doesn't a rocket in space need to keep its engines firing the whole time to keep moving forward?
- Going furtherWhat happens to a spacecraft's path when it swings close by a planet to steal some of the planet's momentum?
- Ties togetherHow does escaping Earth's gravity to reach orbit connect to the same gravity that keeps the moon circling Earth?
Your turn1 of 2
Why does landing a rover safely on Mars count as one of the hardest things humans have ever done?