About @5point9billion

In general relativity, the future light cone is the boundary of the causal future of a point and the past light cone is the boundary of its causal past. (Wikipedia)

From the moment of my birth, light has been racing from Earth at 5.9 billion miles per hour, and light has been reaching us from a likewise increasing distance of origin -- this ever-growing sphere of potential causality is my light cone.

I'm Matt, and today... My light cone contains 42 stars. Theta Ursae Majoris will be reached in 2 weeks.

@5point9billion is a Twitter bot that tells you when you reach the stars, in realtime. More info in this blog post.

To see your own stars

Either: Follow @5point9billion on Twitter, and tweet it your date of birth, like: @5point9billion 18 feb 1978


  1. Sign in -->
  2. Enter your date of birth here
  3. See what stars you've already reached
  4. For live updates: Follow @5point9billion on Twitter

EXPERIMENTAL: Personal star map (requires sign-in).





Small print

When you follow the bot, @5point9billion will make public tweets to you whenever you reach a star. For example: "You're reaching Tau Ceti today."

But because Tau Ceti's distance from Earth is public info, now everyone knows that your date of birth is exactly 11.9 years ago! Some people regard date of birth as private info (I don't). If you're one of these people, don't follow the bot.