The only planet where the interesting question is not geology. Where it is right now, how big and how heavy, what goes round it, and what is still unexplained.
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Distances from the sun are in AU — one AU is the Earth’s average distance, 149,597,870 km — and the angle is where the body sits around its orbit, measured from the March equinox direction.
The mass is worked out from Earth’s gravitational parameter and the gravity from that and its radius; the year comes from Kepler’s third law and the width is the same figure the simulator draws with. None of them is typed in beside the picture, so none of them can disagree with it.
Earth has 1 confirmed moons. Every distance and period here is real, and they are not independent: each pair has to satisfy Kepler’s third law against Earth’s mass, which is how this table is checked rather than trusted.
| Moon | Distance | Orbit | Width | |
|---|---|---|---|---|
| Moon | 384,400 km | 27.3 d | 3,475 km | A quarter of Earth’s width, and drifting away 3.8 cm a year |
↺ marks a moon going round backwards. Watch this system move →
Every one of these is genuinely unsettled — not simplified for the page, not waiting on a textbook update.
Delivered by asteroids and comets after the Earth formed, or present in the material Earth formed from and never entirely lost? The deuterium ratio in most comets does not match Earth's oceans — 67P, measured directly by Rosetta, was three times off — while many meteorites match well. The mixture is still being argued.
Estimates range across billions of years, from 4 billion to under 1 billion years ago, depending on which rock evidence is trusted. Nobody knows what makes a planet do it, which is exactly what you would want to know before guessing how common Earth-like worlds are.
A Mars-sized body hit the young Earth — that much is broadly accepted. But the Moon's isotopes are nearly identical to Earth's, and most impact simulations produce a moon made largely of the impactor, which should look different. Getting a moon that looks like Earth's mantle out of a collision with something else is an unsolved modelling problem.
Findings reviewed August 2026. Space science moves; a date on a finding is part of the finding.
Inward: Venus. Outward: Mars. Or go back to the whole system, where every planet is on screen at once.
The date, the zoom, the span, the speed, the layers and any flight path are all in the address bar, so copying the URL shares exactly what is on screen. Set it up above, then take the link — it is the quickest way to hand a class one specific thing to look at.
This one is about the whole system. If the question is where the sun and the moon are from where you are standing — what time the sun comes up, why tonight's moon is the shape it is — that is the Sun, Earth & Moon movement simulator, which has a page for every city and a slider over a day, a week or a month.
Also: the classroom guide · sunrise & sunset by city · moon phase & moonrise · lunar eclipses · how the positions are worked out
Where did the water come from? Delivered by asteroids and comets after the Earth formed, or present in the material Earth formed from and never entirely lost? The deuterium ratio in most comets does not match Earth's oceans — 67P, measured directly by Rosetta, was three times off — while many meteorites match well. The mixture is still being argued.
When and why did plate tectonics start? Estimates range across billions of years, from 4 billion to under 1 billion years ago, depending on which rock evidence is trusted. Nobody knows what makes a planet do it, which is exactly what you would want to know before guessing how common Earth-like worlds are.
How did the Moon form? A Mars-sized body hit the young Earth — that much is broadly accepted. But the Moon's isotopes are nearly identical to Earth's, and most impact simulations produce a moon made largely of the impactor, which should look different. Getting a moon that looks like Earth's mantle out of a collision with something else is an unsolved modelling problem.