GoKawiilRight now, a sphere of electromagnetic radiation is expanding outward from Earth at the speed of light. It has been growing since the first powerful radio transmissions of the early 1900s. Today that bubble is roughly 240 light-years across and it contains every piece of music, every TV broadcast, every radar ping, and every deliberate message we have ever sent into the cosmos. To any civilisation with a sufficiently sensitive receiver sitting within that bubble, we have already announced ourselves.
The numbers are simultaneously humbling and staggering. Our radio bubble sounds enormous 240 light-years is about 2,270 trillion kilometres. Yet the Milky Way is roughly 100,000 light-years across. We have illuminated approximately 0.000002% of our own galaxy. In the cosmic ocean, we are a single drop of ink that has barely left the tip of the pen.
What is the human radio bubble?
The radio bubble is not a physical object it is a boundary of information. It marks the furthest point that any electromagnetic signal originating from human technology has yet reached, travelling outward in all directions at the universal speed limit: the speed of light, approximately 299,792 kilometres per second.
While Guglielmo Marconi was experimenting with transatlantic signals as early as 1901, most of those early waves were reflected back to Earth by the ionosphere the charged upper layer of our atmosphere that acts as a mirror for certain radio frequencies. It was not until the 1930s, with the adoption of higher-frequency equipment capable of piercing this barrier, that signals began reliably escaping into interstellar space.
Since these signals travel at the speed of light, the radius of our bubble in light-years is approximately equal to the number of years elapsed since the broadcast. A signal sent in 1936 has now travelled roughly 88 light-years from Earth. A signal sent yesterday has barely left the solar neighbourhood. Today, the radio bubble Earth has created spans approximately 240 light-years in diameter a ghostly, ever-expanding archive of everything we have ever said, broadcast, or accidentally leaked into the void.
How far have human radio signals traveled? The key milestones
Each major event in broadcast history corresponds to a different shell within the bubble a ring expanding outward like a ripple in a cosmic pond. Here are the most significant ones, measured by how far they have travelled as of 2026:
Year Event Distance (2026) 1901 Marconi transatlantic signal ~125 light-years 1933 First signals escaping ionosphere reliably ~93 light-years 1936 Berlin Olympics first major TV broadcast ~90 light-years 1938 War of the Worlds broadcast ~88 light-years 1953 Coronation of Queen Elizabeth II ~73 light-years 1969 Moon landing broadcast ~57 light-years 1974 Arecibo Message first deliberate transmission ~52 light-years 1977 Voyager launches + Star Wars released ~49 light-years 2026 This article Just left Earth
Each of these signals is still travelling. The 1936 Berlin Olympics broadcast is currently washing over star systems in the constellation Vela. The Apollo 11 Moon landing transmission is crossing through a region of space containing dozens of stellar systems. None of them have stopped, and none of them ever will they will propagate outward forever, getting weaker with every light-year, until they are indistinguishable from the background noise of the universe.
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