Our broadcasts spread at light speed, growing one light-year a year. The 1969 Moon-landing signal is a sphere a little under 60 light-years across, and it is still in that shell.
NASA/Kimiya Yui · Original image and terms. Web-sized reproduction.
See how far it’s gone.
How to see it tonight
Earth’s radio bubble is not something you can see. It’s an invisible sphere of every strong broadcast the planet has ever sent, expanding outward at the speed of light. This page is about the idea and its scale, not a sighting.
Powerful radio and television broadcasts don’t stop at the sky. They travel outward indefinitely, spreading a little over one light-year further out every year. The first signals strong enough to escape Earth’s atmosphere left roughly a century ago.
The 1969 Moon landing broadcast is part of that expanding shell. As of now it has traveled roughly 55 to 60 light-years, still sweeping past new star systems as it goes.
Whether anyone out there could actually detect these signals is a separate, harder question. A broadcast this faint fades close to the background noise of the universe within a few dozen light-years. Distance traveled is not the same as distance detectable.
Even at its current size, the bubble is small next to the galaxy. The Milky Way stretches more than 100,000 light-years across. Our signals have crossed only a sliver of it so far.
Most of what has spread outward is decades of ordinary broadcasting, radio and television. Nobody deliberately aimed it at the stars. The Apollo 11 broadcast is simply the most famous piece of it.
What SkyLumi does
SkyLumi draws the radio bubble as an expanding sphere on the star map. It marks roughly how far Earth’s earliest strong broadcasts have reached.
Search, Aim and AR work the same way across the app. Point your phone and the map lines up with the real sky. Night Vision keeps a deep red display for dark adaptation.
The core sky works offline, no account, no ads. Deep survey imagery of the stars inside the bubble needs a connection and streams in when you pinch to zoom.
A few things to know.
Can I see the radio bubble in the sky?
No. It’s an invisible sphere of radio signals, not a visual feature. SkyLumi marks its rough extent on the star map.
How far has it actually traveled?
Roughly 100 or more light-years across, growing by about a light-year a year. The 1969 Moon landing broadcast is around 55 to 60 light-years out as of now.
Could anyone out there actually detect us?
Maybe, for the nearest systems. A broadcast this faint becomes very hard to pick out from background noise past a few dozen light-years. Reaching a star and being detectable there are different things.
Is this the same as searching for aliens?
Not directly. It’s a measure of how far our own signals have spread, not a search for anyone else’s.
More in the Sky Library
Sources and image credit
- Kaltenegger & Faherty, “Past, present and future stars that can see Earth as a transiting exoplanet,” Nature (2021), preprint
- NASA: the Apollo 11 mission
Image attribution and original terms are linked beneath the image. Use of imagery does not imply endorsement of SkyLumi.