Earth Here: Message to Stars

Aim at the sky, write a message, and your phone actually transmits it — right there, right then.

■ Not a simulation
When you press send, your phone's Bluetooth radio starts broadcasting. If it can't, the app says so instead of pretending. How far it has travelled is worked out from the moment you sent it and the speed of light.

■ Choose where it goes
The Moon, the Sun and the planets keep moving, so their distance changes day by day. Stars come with their constellation and their distance in light years. Aim at the sky, or pick from the list.

■ Where it is right now
You get a notification each time it passes the Moon, passes Mars, leaves the solar system. When the travel time to your target is up, that journey ends — and a day later the record is cleared.

■ It all stays on your phone
No account, no sign-in. Your message and your log live only on this phone. We don't run a server.