Instruments
Fifteen things to play with. They all follow my clock, the site clock at the bottom of the page, so winding one winds them all. Nothing here can be broken. I have tried.
All instruments
The Moon right now
Its face at the site clock’s time, on NASA’s own map of the surface, with its real tilt and the next full and new Moon.
Saturn’s rings today
The real tilt of the rings and their shadows, and the date they next turn edge-on and vanish.
The planets in a telescope
Seven discs at one scale, with their real sizes in the sky, phases and tilts.
Hear a pulsar spin
Five dead stars ticking at their real spin rates, up to 716 turns a second. I slowed the diagram down so you can see why they pulse.
The heart of the Crab Nebula, where one of them sits. This light left the nebula about 6,500 years before the picture was taken. The distance is the one given for the whole Crab Nebula. Image: NASA and ESA.
Black hole, hands on
Drag a black hole across the stars, change its mass and see what falling in would do to you. The one at the centre of our galaxy is 25 million km across its event horizon.
The black hole in the galaxy M87. The caption gives no distance, so no light-age. Image: EHT Collaboration, CC BY 4.0.
- Born 1 January 2000?You are Jupiter years old
The sky when you were born
Enter a date and save a card of that day’s sky: the planets, the Moon and your age in Jupiter years.
Solar system map
Zoom from Jupiter’s moons out to the Kuiper Belt, drag to wind time, and read how long light takes to reach each planet from Earth.
- EastWest
Jupiter’s moons from Earth
Where Io, Europa, Ganymede and Callisto sit beside the planet right now, as you would see them in binoculars.
- Up now from GreenwichDoing the sums
Planets tonight
Which planets are above your horizon and when, from wherever you are, with rise and set times.
- Total solar eclipse, 2 August 2027Up to 6 min 27 s of darkness
The eclipse of 2 August 2027
Where the Moon’s shadow falls, and how much of the Sun is covered from your place and when.
- Brightest in the sky over Greenwich nowDoing the sums
The whole sky tonight
A chart of everything overhead: bright stars, the Moon and the planets, for your place and hour.
- Sunlight reaching Earth right now left ago
Ride a beam of light
Send a flash from the Sun and wait, in real time, for it to reach each planet. Bring a book for Neptune.
- To Jupiter by car at 100 km/h, no stops
Driving to Jupiter
How long the trip to any planet would take on foot, by car, by airliner and as light. Pack sandwiches.
- If the Sun were a footballEarth is wide, away
The solar system to scale
Shrink the Sun to something you can hold and see how small and far apart the planets become.
- 70 kg on Earth reads185 kg on Jupiter12 kg on the Moon
You, on other worlds
What the scales would read on Jupiter, Io or Pluto, and how old you are in each planet’s years. On Jupiter I am a little over four.

