WELCOME TO XAVIER'S WORLD

Curiosity looks good on you.

A place to make numbers click, chase the mysteries of space, and build whatever you can imagine.

Learn by trying. Wonder out loud. Build your own way.
MATH LAB / LEARN BY DOING

A little practice.
Big discoveries.

See a small example, try a question, then explain how you know. Use a hint whenever you need one.

DIVISION MISSIONQUESTION 1
1 / SEE IT

Let's learn together

    2 / TRY IT

    Let's share equally.

    Loading your mission…

    PICK AN ANSWER

    Wonder note: factorials are written with an exclamation mark. For example, 4! = 4 × 3 × 2 × 1.

    MATH MAKER / MOVE THE MODEL

    Change it. See it. Understand it.

    Choose a concept, move the controls, and notice what stays the same.

    Equal groups

    Move the sliders to share a total into equal groups.

    SPACE ZONE / ASK BIG QUESTIONS

    What's up with
    black holes?

    They are mysterious, real, and pretty amazing. Take a little space trip to learn what scientists know.

    THE EXPLORER

    Out in the universe

    A black hole has enormous gravity. Like other objects with mass, it pulls on nearby things.

    FAR AWAYEVENT HORIZON

    Scientists find black holes by studying how they affect nearby stars, gas, and light.

    01

    Invisible center

    We cannot see a black hole itself, because light cannot escape from inside its event horizon.

    02

    The point of no return

    The event horizon is the boundary beyond which light cannot get back out.

    03

    Stretchy space

    Near some black holes, gravity can pull more strongly on one end of an object than the other.

    SPACE FIELD GUIDE / FOLLOW THE CLUES

    How do we know they're there?

    A black hole is dark, but its surroundings can tell a story. Choose a clue to investigate.

    FOLLOW THE MOTION

    Stars reveal an invisible neighbor

    Astronomers can track stars moving around a dark spot. Their orbits reveal the mass of what they cannot see directly.

    Wonder: what could make a star change direction?

    SPACE CHECK / THINK LIKE A SCIENTIST

    What did you discover?

    Pick an answer. If it is tricky, use the clue and try again.

    Keep exploring with NASA Space Place and NASA Science .
    BRICK STUDIO / AN ENDLESS PLACE TO MAKE

    Build a whole world.

    Start with one piece, then keep going. Your canvas grows as far as your imagination can take it.

    ✦ 29 original parts↗ Open-ended canvas◈ 3D views
    0 pieces
    BUILD VIEW · tap to place
    100%

    Arrow keys move the cursor; Enter places a piece. Select a piece with Move, then use arrows to move it, R to rotate, or Delete to erase. Use Pan to travel anywhere.

    CENTER · 0, 0

    ONE LAST THING

    Keep asking “what if?”

    That's how discoveries begin.

    Back to the top