Human Radio Waves in Space: A Century of Cosmic Communication
Humans have been broadcasting radio waves into deep space for over a century, beginning with Guglielmo Marconi’s pioneering work in the late 19th century. This ongoing transmission has created an expanding “bubble” of radio signals that currently spans approximately 200 light-years from Earth, effectively announcing humanity’s presence to any potential listeners within the Milky Way galaxy.
The Scale of Human Radio Waves
To put this in perspective, Adam Grossman created a diagram illustrating the size of this bubble relative to the vastness of our galaxy. News i8 has updated that diagram for 2024, see above. The Milky Way itself measures between 100,000 and 180,000 light-years across, making the human radio broadcast bubble appear minuscule by comparison. In fact, the bubble is so small that it represents only a tiny fraction of the galaxy’s total size. As Grossman’s visualization shows, the bubble is merely a blue dot at the center of a much larger black square representing the Milky Way.
Cosmic Context
Despite its impressive diameter, the human signal bubble is just a fraction of the observable universe, which contains approximately 200 billion galaxies and stretches about 46 billion light-years to its edge. This means that our radio broadcasts are about 331 million times smaller than the distance to the observable universe’s boundary. Such comparisons highlight how isolated our signals are in the cosmic expanse.
Limitations of Detection
While our radio waves have reached many nearby stars, their strength diminishes significantly over distance. By the time signals travel beyond 100 light-years, they become so attenuated that they are unlikely to be detectable without advanced technology. Some estimates suggest that with current technology, we could only detect Earth’s signals from about 10 light-years away under optimal conditions. Consequently, even if there are extraterrestrial civilizations within this range, they may struggle to pick up our broadcasts amidst cosmic background noise.
Our Radio Star Reach vs Voyager Spacecraft
According to recent studies, around 75 star systems are known to be able to detect Earth’s radio signals, which have been traveling for over a century. 800 Stars Estimate: A broader estimate suggests that there could be about 800 stars within this radius. This estimate accounts for various types of stars, including red dwarfs, which are the most common.
Radio Signals: Earth’s radio signals are emitted from various broadcasts and are expanding outward at the speed of light. They become weaker and less detectable as they move further into space due to cosmic background noise and signal degradation. They have traveled approximately Approximately 100 light-years.
Voyager Spacecraft: The Voyager probes were designed for exploration and data transmission. They have crossed the heliopause, entering interstellar space, and continue to send back scientific data about conditions beyond the solar system. Their communication is facilitated through NASA’s Deep Space Network, which enables them to transmit data from vast distances. They have traveled over 24.5 billion kilometers (about 164 AU) from Earth as of September 2024. That distance human physical craft have traveled is
The Milky Way “Image” Is A Computer Graphic
Since no spacecraft has traveled far enough to capture an actual photograph of the Milky Way from an external viewpoint, Hurt’s illustration is a computer-generated representation based on observed data from our galaxy and similar galaxies like Andromeda. The Spitzer Space Telescope played a crucial role by capturing infrared images that highlighted the galaxy’s spiral structure. These observations helped scientists understand the arrangement of stars and dust within the Milky Way. This artistic interpretation is grounded in scientific conclusions but remains a conceptual visualization rather than a direct image. Hurt’s illustration has been widely adopted in scientific literature due to the limited availability of high-quality images of the Milky Way, making it a staple reference for researchers.
What Stars and Planets Could Have Heard Us?
| Star System | Type | Known Exoplanets |
|---|---|---|
| Ross 128 | Red Dwarf | 1 (Ross 128 b, Earth-sized) |
| Teegarden’s Star | Red Dwarf | 2 (Teegarden’s b and c, Earth-like) |
| Trappist-1 | Ultra-cool Dwarf | 7 (Four in the habitable zone) |
| Barnard’s Star | Red Dwarf | None known |
| Proxima Centauri | Red Dwarf | 2 (Proxima Centauri b and c, one potentially habitable) |
| Luyten’s Star | Red Dwarf | 1 (Luyten b, Earth-sized) |
| Wolf 1061 | Red Dwarf | 3 (Wolf 1061 b, c, d; one in the habitable zone) |
| GJ273 (Luyten’s Star) | Red Dwarf | 2 (GJ273 b and c; both potentially habitable) |
What Planets Most Like Earth May Have Heard Us?
| Planet Name | Star System | Distance (light-years) | Earth Similarity Index (ESI) |
|---|---|---|---|
| Proxima Centauri b | Proxima Centauri | 4.2 | 0.86 |
| Ross 128 b | Ross 128 | 11.0 | 0.86 |
| Teegarden’s Star b | Teegarden’s Star | 12.5 | 0.97 |
| Teegarden’s Star c | Teegarden’s Star | 12.5 | 0.66 |
| GJ 1002 b | Gliese 1002 | 15.8 | 0.86 |
Years to Reach Teegarden’s Star b
How long will it take to reach Teegarden’s Star b at our current top human spacecraft speed?
To calculate how long it would take to reach Teegarden’s Star b using the current top speed of human-made spacecraft, we can use the speed of the Parker Solar Probe, which has reached speeds of approximately 400,000 miles per hour (about 645,000 kilometers per hour). At the current top speed of the Parker Solar Probe, it would take approximately 20,973 years to reach Teegarden’s Star b.
The Search for Extraterrestrial Intelligence
The Search for Extraterrestrial Intelligence (SETI) continues to monitor for signs of intelligent life while also sending messages into space. However, given the immense scale of the galaxy, SETI researchers estimate that they may need to listen and transmit for tens of thousands of years before making contact with another intelligent species.
As we contemplate these vast distances and the potential for life beyond Earth, it becomes clear that while our technological achievements allow us to broadcast our existence into space, we remain a small voice in an overwhelmingly large universe.