Everything below is for the date in the viewer, and for the world you have selected. Distance between two planets is not the difference of their orbits — it depends entirely on whether you are on the same side of the Sun.
Your age is just how many times your world has been round. Your weight is what a bathroom scale reads, which is a force — the amount of you never changes.
| World | Your age | Birthdays left by 90 | Scale reads | A day lasts |
|---|
A diagram that shows the planets big enough to see cannot show the distances, and one that shows the distances honestly is an empty page with a few specks on it. Shrink the Sun to something you can hold and see where everything lands.
Nothing here is exaggerated: every disc is drawn at the same kilometres-per-pixel. Tap one to put it in the comparison below.
Four balls of rock and metal close in, two of hydrogen and helium, two of ice. The dividing line is the frost line — the distance at which water could freeze while the planets were forming, which is why the big ones are all outside it.
Balance the sunlight a planet absorbs against the heat it radiates and you get its temperature, with nothing but distance and reflectivity. It works — until a planet has air. Cyan is what the sums predict, red is what the thermometer says.
The orbital elements: semi-major axis and eccentricity set the ellipse, inclination and two angles tilt it, the mean anomaly says where along it. Everything is worked out from them.
M = E − e·sin E has no closed-form solution and is hunted numerically. Pluto, at e = 0.25, is the one that tests a lazy solver.
In Earth years and AU the constant is 1: a planet four times further out takes eight times as long. Every period is computed from it; Neptune, the worst, is 0.02% off.
If the Sun is a football, Earth is a grain of sand 26 m away and Neptune another most of a kilometre off. Every diagram cheats on one of size or spacing.
Everything else put together (every planet, moon, asteroid and comet) is the 0.13% left over from building it. Of that remainder Jupiter is two and a half times everything else combined, making the other seven planets a rounding error on a rounding error.
Uranus is knocked 97.8° over and rolls along its orbit on its side. Venus is at 177.4°: upside down, turning backwards, taking 243 days to do it, longer than its own year. A tidy accretion disc produces neither: they are leftovers of very large collisions, still legible four and a half billion years later.
Ganymede is 2,634 km in radius and Titan 2,575; Mercury is 2,440. Size was never what made something a planet: what it orbits is. Both are compared here but not put into orbit, because at any honest scale a moon sits inside its own planet’s dot.
A spinning planet is not a sphere: Jupiter’s equator is 4,600 km further from its centre than its poles. This page uses the mean radius throughout, because it gives the right volume and therefore density, so escape velocity reads 60.2 km/s where most references quote 59.5, at the equator. Both are right; quietly switching between them per row is how a tool contradicts itself.
Astronomical unit: the average Earth–Sun distance, about 150 million km. Semi-major axis: half the long way across an ellipse: the honest “distance from the Sun”. Eccentricity: how squashed; Earth is 0.017, almost a circle; Pluto 0.25 and genuinely oval. Inclination: tilt out of the Earth’s plane; everything is within a couple of degrees except Pluto at 17. Perihelion and aphelion: nearest and furthest points; a planet is fastest at perihelion (Kepler’s second law).
Equilibrium temperature: a bare ball balancing absorbed sunlight against radiated heat; ignores atmospheres, which is why Venus makes a fool of it. Albedo: the fraction of sunlight reflected: fresh snow about 0.8, cloud-wrapped Venus 0.76, the dark Moon 0.11. Synodic period: how often a planet lines up with Earth again: not its year, because we are moving too. Retrograde: orbiting or spinning opposite to everything else: Venus spins retrograde and Triton orbits retrograde, how we know Neptune captured it. Frost line: where water freezes around a young star: rock inside, giants outside.
Not usually. Laid side by side they span about 395,000 km, and the Moon averages 384,400 — so they do not fit. They only fit when the Moon is near the far end of its orbit, at 406,700 km. The famous picture is true for part of each month.
Six orbital elements per planet and Kepler’s equation, nothing looked up. Every period on the page is computed from Kepler’s third law and lands within a fraction of a per cent of the published value. The orbits are two-body ellipses, so nothing tugs on anything else — which is the effect Neptune was discovered in.
Because it is. If the Sun is a football, Earth is a grain of sand 26 metres away and Neptune is another grain most of a kilometre off. There is no screen on which the planets are both visible and correctly spaced, so every picture you have seen cheats on one or the other. The true-scale option is the one that does not.
Two radii. A spinning planet is not a sphere: Jupiter’s equator is 4,600 km further out than its poles. This page uses the mean radius throughout, because that gives the right volume and density, so it reads 60.2 km/s where references quoting the equator say 59.5. Both are right.
Releases in which this page changed, newest last. Derived from the archived copy of every release, not from notes written afterwards — so it reflects what actually shipped. Site-wide passes are left out; they are in the full changelog.