Heaven and Earth.
A map-based clock concept with the celestial sphere overlaid on a world map, in their true relative rotations, so you can see what part of the sky is directly above every part of the Earth at any time.
The world map makes one counterclockwise rotation per solar day, as the Earth rotates counterclockwise on its axis when viewed from the north. The result is a clock face where we can tell roughly what time it is everywhere on Earth at once. It can also be used to locate all celestial objects in the sky, and even the cardinal directions, like a rough compass (unless it's overcast).
It takes a bit of explanation to fully understand how to read it, but the reward is astronomical.
Time is space.
Noon is defined as the top of the clock, but since the Earth orbits the Sun, the Sun appears to travel around the celestial sphere, along the imaginary circle in the sky we call the ecliptic. To adjust for this and keep the Sun at the top of the clock, the whole sky map is rotated in the opposite direction once per year.
The daily rotation of the world map combined with the yearly rotation of the sky map is the key to how the Heaven and Earth clock works. For full, visualized explanations of the relevant astronomy concepts and all the things you can read from this clock, read on.
The full conceptThe family tree.
Heaven and Earth is a combination of ideas from two mostly separate traditions, namely astrolabe-inspired astronomical clocks and map-based world clocks. Attempts have been made to combine the two on a single device, but most of these have resulted in what from our perspective look like near-misses.
Here we trace the family tree back about seven centuries, highlighting particularly innovative or otherwise interesting ancestors, and concluding with a case for what, exactly, is new in the Heaven and Earth design.
For screens big and small.
Web app
A flexible web app for many form factors, with a free version and a fancier paid one. Get in touch for individual customization.
Smartwatch
Available now for Wear OS, with support for more smartwatch platforms planned. A companion Wear OS app for exploring the clock in time-lapse is in the works.
Mobile
An Android app in the works – the dial as a live wallpaper, a home-screen widget, and a screensaver. An iPhone version is planned.
Physical installation
A variety of package solutions with big circular screens, embedded computers, and nice plaques to explain the basics.