Help with Deep Time

Questions, a mistake in the science, or something that does not work: write to tenji73 (at) gmail (dot) com. A sentence on what you did and what you saw is enough.

Getting around

• The two tabs at the top left switch between One year and Deep time.
• Drag on the scene to turn the camera, scroll or pinch to zoom, double-click to return to the view.
• space plays and pauses, ← → step through time, 1 to 5 switch the camera view, C shows or hides the constellations.
• One year: click the place name to choose a city or type coordinates, or click any point on the globe. N returns to now.
• On the timeline, click a month and then a day to zoom in; in Deep time, click an eon, era or period. Esc zooms out.
• Click a card or a chart tab to change the chart.

Common questions

How does the app know where I am? It does not. The first time, it picks the largest city of your Mac's time zone. Click the place name to choose your own; the choice is remembered on your Mac.

How exact are the times? Near the present, sunrise, sunset and eclipse times are good to well under a minute, for a flat horizon as at sea. Far from today Earth's rotation is not known exactly: about ±4 minutes in year 1. The app says so for such years.

Why are meteor showers only given from 1900 to 2100? The dust streams shift, appear and fade over centuries, so earlier and later years would be guesses.

Are the Sun, Earth and Moon to scale? No. The scene is composed for clarity. The numbers beside it are the real ones.

Does it need the internet? No. Only the links marked with an arrow open your browser.

Where do the numbers and pictures come from? Open "Sources and credits" at the bottom right of the window. Every source, author and licence is listed there.

Which Macs does it run on? Macs with Apple silicon, macOS 13 or later.