Why does the view jump between zoom levels instead of scrolling smoothly?

Because the solar system will not fit in one frame. Out to Mars the outermost orbit is only about 4 times the innermost, and everything is separable. Out to Saturn it is 15 times and the inner four are a tight knot. Out to Neptune it is 129 times: Mercury's whole orbit is 6.6 pixels across and Earth's is 17. Each rung of the ladder is a view where something is legible; a smooth zoom would just pass through a lot of frames where nothing is.

Can I see the moons of the other planets?

Yes — each of the five planets that has large moons gets a view of its own, where the frame is the moon system rather than the solar system. The orbits, the periods, the sizes and the direction of travel are all real, and the planet's own disc is to scale against them. What is not solved for is where each moon sits on its orbit at a given moment, and the picture says so: watch Io lap Europa twice while Europa laps Ganymede twice, which is a real resonance, rather than reading it as tonight's sky.

Are the planets drawn to scale?

The ORBITS are, within each view. The planets themselves cannot be: at the Saturn view, Jupiter — the largest planet — would be 0.069 of a pixel across, and Earth 0.0063. So the dots are legibility sizes, not measurements. The exception is the Earth and Moon view, which is to scale in both size and distance at once.

When is the next launch window to Mars?

Every launch window on this site is solved from the orbits when the page loads, not written into it — the answer for Mars right now is November 4, 2026, with an arrival 265 days later. Windows to Mars come round roughly every 26 months, because that is how long it takes Earth to lap Mars and line the two orbits up again.

Where is the asteroid belt, and why does it have gaps?

Between Mars and Jupiter, from about 2.06 to 3.28 AU. The gaps are Jupiter's doing: an asteroid whose orbital period is a simple fraction of Jupiter's gets the same tug at the same point over and over until it is pushed out. This page computes every edge and every gap from Jupiter's own orbit rather than drawing them from a remembered number, which is why they land on the Kirkwood gaps at 2.50, 2.82 and 2.96 AU.

How accurate are the positions?

The planets come from Keplerian elements with per-century rates — the standard approximate-positions method — good to a few arcminutes over 1800–2050 — JPL's own stated maxima run to about ten arcminutes for Jupiter and Saturn, which is still around one pixel at the widest zoom here. The date picker stops at 2050 for that reason: past it the linear rates are being extrapolated. The comets are published osculating elements propagated as a two-body orbit, which is right about where in the system a comet is and not right to the day: a real comet is pulled about by the planets and shoved by its own outgassing. None of this is an ephemeris.

TimeAndSpace.Science

Solar System Simulator

The planets on their real orbits, moving. Drag through a month, a year, a decade or a century; zoom from Jupiter’s moons all the way out to Neptune; switch on the asteroid belt, the comets, and the flight path to Mars.

Three views of Earth, and how it fits with the rest of the solar system

1 · From a place on EarthSun & moon from your own townThe Earth turns under a marked location: day and night, sunrise, moonrise and tonight's phase. 2 · Step backEarth & the moon's orbit around the sunAll three moving at once — the month, the seasons and the year on one screen. 3 · Step back againThe full solar systemEarth's orbit among all eight, from Mercury's 88 days out to Neptune's 165 years.You are here

Wed, August 26, 2026

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View tilt

flat

Speed

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Planet zoom level

Include:

Starting date

The slider covers

Jump to All the planets Earth & the Moon Inner planets Asteroid belt Jupiter’s moons Saturn’s rings The outer planets

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.

What this is, and how it works

This is a working model of the solar system. The planets sit on their real orbits, moving at their real relative speeds — Mercury really does lap everyone; Neptune really does barely move in a lifetime.

Span is how much time the slider covers: a month, a year, a decade or a century. Speed is how fast that time plays. Zoom climbs a ladder of views, because the whole system will not fit in one frame. Now jumps back to this moment. Tilt tips the view so the orbits look like ellipses instead of circles. Switch on the asteroid belt, the comets, and a flight path to Mars when you want them.

The orbits are to scale within each zoom. The planet dots are not — they would be smaller than a pixel. The ladder card below says by how much, computed from the drawing itself.

Questions this page answers

The question is the link. A short answer sits here; tap through for the drawing and the deeper pass.

Why don’t planets fall into the Sun? They are falling. They are also moving sideways. By the time a planet has fallen, the Sun is no longer where it was falling toward. Falling and missing, without end, is an orbit. There is no outward force holding them up.
How does an orbit work? At every instant a planet has a velocity — where it is already going — and gravity adds a small pull straight toward the Sun. Bend a path by the same small amount at every step and it closes. That closed path is the orbit.
Why does Jupiter have so many moons? Gravity’s reach grows with mass, and Jupiter has more of it than anything in the solar system except the Sun. A wide region around it is a place where a small body stays with Jupiter instead of orbiting the Sun on its own.
What is the asteroid belt? A ring of leftover rock between Mars and Jupiter. It is not the wreckage of a planet. Jupiter’s gravity never let the rubble gather into one world. The dark gaps in it are resonances — the same tug, at the same point, over and over.
Why are the planets drawn so close together? Because the real solar system will not fit on a screen. Neptune is about 78 times farther from the Sun than Mercury. Drawn honestly at one scale, the inner four sit in the innermost tenth of the picture. This simulator climbs a zoom ladder so something is always legible, and it tells you what is compressed.

A page for every planet

Each one carries its own moon system, its physical figures worked out from its mass rather than copied in, the open questions about it, and what has been learned lately. The planets is the way in if you would rather see them side by side first — a picture and a couple of paragraphs each, in orbital order.

All the planets Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto The asteroid belt Comets Rocket launches

Flying to Mars: when to leave

A rocket cannot point at Mars and fire. It has to leave Earth on an orbit around the sun whose far side touches Mars’s orbit — half an ellipse — and it has to leave at the moment when Mars will have arrived at that far side by the time the ship gets there. That is what a launch window is, and it is why they come round only every 25.0 months.

Next window opensNovember 4, 2026

ArrivesJuly 27, 2027

Flight time265 days — 0.7 years

Speed change to leave Earth’s orbit round the sun3.08 km/s

The burn itself, from a low Earth orbit3.63 km/s

Slowing down to stay at Mars2.49 km/s

The window after thatDecember 6, 2028

Set Launch to: Mars on the rocket launches page to see the ellipse, where Mars is on launch day, and where it will be on arrival. Click the date to fly it.

What the flight path is, and is not

It is a minimum-energy transfer: the cheapest possible path, half an ellipse with Earth’s orbit at one end and the target’s at the other, solved against where the planets really are — so the arrival lands on the planet’s real distance from the sun and its real position on the day it gets there, not on a circle standing in for its orbit.

It is not a mission plan, and three things are left out on purpose. The orbits are treated as flat, so the real inclinations — Mars is tilted 1.85°, Jupiter 1.3° — cost a plane change this ignores. Real missions trade fuel for a faster arrival, so they leave within days or weeks of these dates rather than exactly on them. And anything going past Jupiter usually steals speed from a planet on the way instead of buying it with fuel, which changes both the date and the path.

What it gets right is the thing worth teaching: why the window exists, why it comes round on the cadence it does, and why the cost of the trip is set by where two planets happen to be rather than by how far apart they are.

Why the view climbs a ladder instead of zooming smoothly

The solar system does not fit in one frame, and the reason is a ratio. What decides whether you can see anything is how many times bigger the outermost drawn orbit is than the innermost one:

The inner planets4:1 — Mercury’s orbit 203 px across

Out to Mars4:1 — Mercury’s orbit 191 px across

Out to the asteroid belt10:1 — Mercury’s orbit 88 px across

Out to Jupiter15:1 — Mercury’s orbit 57 px across

Out to Saturn27:1 — Mercury’s orbit 32 px across, the inner four a knot

Out to Neptune81:1 — Mercury’s orbit 10 px across, the inner four a knot

Out to Pluto (a dwarf planet)129:1 — Mercury’s orbit 6.6 px across, the inner four a knot

So each rung is a view where something is legible, rather than a smooth zoom that spends most of its travel in frames where nothing is. The outermost rung keeps the inner four as a labelled knot on purpose — that is the shape of the solar system, and it is the part every evenly-spaced textbook diagram hides.

Why the frame is square

Everything drawn here is a set of concentric circles, and a circle in a widescreen frame is limited by the short side — the corners hold nothing. A page column sets the WIDTH, so the honest comparison is a 16:9 frame of the same width: squaring it buys about 87% more drawing radius, which on the outer rung is the difference between Mercury’s orbit being 3.5 pixels wide and 6.6.

What is to scale here, and what is not

The orbits are to scale within each view. The planets are not, and cannot be: at the Saturn view Jupiter would be 0.069 of a pixel across and Earth 0.0063. The dots are sized to be seen, not measured.

The one exception is Earth & the Moon, and it is worth looking at for that reason alone: it is the only view on this site that is to scale in size and distance at the same time. The moon really does sit about 30 Earth-diameters away — far further than almost every diagram draws it, and close enough to fit on a screen.

On a moon system view, the planet’s own disc is to scale against its moons’ orbits — so Saturn’s rings really are that wide compared with Titan’s orbit, and Phobos really is that close to Mars. The moons themselves are drawn oversize by a factor the picture prints, because at the zoom where Callisto’s orbit fills the frame, Ganymede is half a pixel across.

How far anything actually gets

Span	Mercury	Earth	Jupiter	Saturn	Neptune
Month	123°	30°	2°	1°	0°
Year	4.2 laps	360°	30°	12°	2°
Decade	42 laps	10.0 laps	303°	122°	22°
Century	415 laps	100 laps	8.4 laps	3.4 laps	218°

Which is why the zoom, the span and the speed belong together. A month is the right span for Mercury and means nothing for Neptune; a century sends Mercury round 415 laps — an unreadable blur — while Neptune still has not finished a single lap, because one Neptune year is 165 of ours. The speed slider is there so you can slow a century down until the outer planets separate, or run a month fast enough to see Mercury move.

Make a link to a particular view

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.

The other simulator

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. Between the two is the three bodies moving together — Earth going round the sun, the moon going round the Earth, on one screen and openly not to scale, keeping only the real ratio between the two periods.

And for why any of it stays up: the orbital velocity simulator takes one planet and lets you set its distance and its sideways speed by hand, so you can watch the balance that holds every orbit here — and break it, into an ellipse, an escape, or a fall into the sun.

Also: the classroom guide · sunrise & sunset by city · moon phase & moonrise · lunar eclipses · how the positions are worked out

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