Rabbit Hole is an interactive science encyclopedia. Start with any question, play with what you find, and follow your curiosity as deep as it goes.
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Take a peek inside
Two pages from the Space chapter. Go on, play with them.
Rabbit Hole Encyclopedia · Space
The Solar System
Our Solar System is the Sun and everything that travels around it: eight planets, their moons, and lots of rocks and ice. The Sun is so huge that it holds 99.8% of all the stuff in the Solar System! If Earth were a pea, the Sun would be a beach ball about 60 m away.
Meet the planets
Fig. 1. Real sizes and real distances (orbits drawn as circles). From far away the planets are too small to see, so rings show where they are. Click a name to fly there!
The four planets closest to the Sun, Mercury, Venus, Earth and Mars, are small and rocky. You could stand on them.
The four outer planets, Jupiter, Saturn, Uranus and Neptune, are giants made mostly of gas and ice. Jupiter is so big that if you could squish all the other planets together, they would fit inside it with room to spare!
Saturn 764
Uranus 63
Neptune 58
Earth 1
Venus 0.86
Mars 0.15
Mercury 0.06
Empty 435
Fig. 2. Each dot is enough space for one Earth: Jupiter has room for 1,321. The numbers show how many Earths' worth of space each planet fills.
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Rabbit Hole Encyclopedia · Space
Earth's Moon
The Moon is Earth's only natural satellite. It is about a quarter as wide as Earth, and it always shows us the same face. Nobody on Earth has ever seen the far side with their own eyes!
Why does the Moon change shape?
The Moon doesn't make its own light. Half of it is always lit up by the Sun. As the Moon travels around Earth, we see different amounts of that sunny half. One full cycle of shapes, called phases, takes almost 30 days.
Fig. 3. The Moon's orbit seen from above Earth's North Pole, and the shape we see from the ground.
How far away is the Moon?
In most pictures the Moon looks like it's right next door. Is it really? Make your guess before you peek.
How many Earths could you line up between Earth and the Moon? Slide to guess!
EarthMoon
Fig. 4. Earth and the Moon drawn to scale. Each faint circle is one more Earth.
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An encyclopedia that wants you to wander
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Interactive, not just text
Diagrams and simulations you can poke, drag and play with, so ideas click instead of just being read.
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Everything is connected
Each entry links to the ideas behind it, so one question leads naturally to the next.
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Follow your curiosity
No fixed syllabus. Choose whichever path looks interesting and see where it takes you.
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For curious minds of all ages
Clear explanations to start with, and more depth whenever you want to keep digging.
How it works
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Start with a question
Why do cats purr? How do stars die? Begin anywhere.
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Explore it hands-on
Read a short, clear answer and play with the interactive parts.
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Follow the links deeper
Every answer opens new questions. Keep going as far as you like.
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Be the first one down the hole
Join the waitlist and we'll tell you as soon as Rabbit Hole is ready to explore.