Something strange surrounds our planet. High above the clouds, past the reaches of commercial aircraft, and beyond even the orbit of many satellites, an invisible bubble wraps around Earth. Scientists didn’t build it. Engineers didn’t design it. In fact, nobody knew it existed until a few years ago.
Humanity has a long history of changing our planet, sometimes on purpose and sometimes by accident. We’ve altered coastlines, redirected rivers, and transformed entire ecosystems. We’ve also eradicated diseases like smallpox and developed technology capable of moving asteroids. Our fingerprints mark nearly every corner of Earth’s surface. But our influence doesn’t stop at the edge of the atmosphere. It reaches into space itself, and we had no idea we were doing it.
For decades, military and government agencies have been sending radio signals deep into the ocean to communicate with submarines. Nobody thought much about where else those signals might travel. Nobody imagined they could affect anything beyond their intended targets lurking beneath the waves. But space probes orbiting Earth detected something unexpected. All those radio waves weren’t just sinking into the sea. Some of them were rising, passing through our atmosphere, and doing something remarkable in the void above.
Earth’s Natural Magnetic Defense System
Before understanding what humans accidentally created, it helps to know what nature built first. Our planet generates a massive magnetic field that extends thousands of kilometers into space. Picture an invisible force surrounding Earth, deflecting dangerous particles the way an umbrella sheds rain. Without it, life as we know it would face constant bombardment from cosmic rays and violent solar winds.
Charged particles from the sun race toward Earth at incredible speeds. Most of them bounce off our magnetic shield and continue their journey through the solar system. But some particles don’t bounce away. Instead, they follow magnetic field lines down toward the poles, where they collide with gases in our upper atmosphere. When they slam into nitrogen and oxygen molecules, they produce one of nature’s most beautiful displays. In the north, we call them the Northern Lights. In the south, they become the Southern Lights.
Yet our magnetic field does more than create light shows. It also traps enormous swarms of charged particles in bands of radiation circling the planet. Imagine rings of energetic particles suspended in space, held in place by invisible magnetic forces. For millions of years, these bands have hovered above Earth, pulsing and shifting with activity from the sun.
What Are Van Allen Radiation Belts?
Scientists discovered these radiation bands in the 1950s during early space exploration. James Van Allen, an American space scientist, led experiments that confirmed their existence. In his honor, researchers named them the Van Allen radiation belts.
Picture two enormous donuts made of radiation encircling Earth. One sits closer to the surface, beginning around 1,000 kilometers up and extending to about 6,000 kilometers above sea level. Relatively small and stable, it hugs our planet like a tight ring. A second, larger belt floats much higher, stretching between 13,000 and 60,000 kilometers above Earth. Less predictable and more variable, it swells and contracts based on solar activity.
Of course, describing them as donuts oversimplifies their true nature. NASA launched a mission called the Van Allen Probes to study these belts in far greater detail. Active until 2019, these spacecraft revealed that the belts look radically different depending on particle energy levels. What appears as a simple donut at one energy becomes something far more complex at another.
But particle energy wasn’t the most interesting thing Van Allen Probes discovered. Something else caught scientists off guard. Something that pointed directly back to human activity on Earth’s surface.
Radio Waves, Not Satellites, Are Responsible
When researchers first noticed changes in the radiation belts, satellites seemed like obvious suspects. After all, we’ve launched thousands of them into orbit. Surely all that hardware must affect the space environment somehow. But satellites weren’t causing the changes. Radio waves were.
Specifically, very low frequency radio waves, known as VLF transmissions, turned out to be the culprit. Militaries around the world use VLF signals to communicate with submarines. Water blocks most radio frequencies, making underwater communication extremely difficult. VLF waves, however, can penetrate ocean depths where submarines operate.
Ground stations transmit VLF signals at enormous power levels, strong enough to reach vessels hidden beneath hundreds of meters of seawater. But radio waves don’t simply stop when they hit their target. Some of that energy travels in unexpected directions.
“A number of experiments and observations have figured out that, under the right conditions, radio communications signals in the VLF frequency range can in fact affect the properties of the high-energy radiation environment around the Earth,” explained Phil Erickson, assistant director at the MIT Haystack Observatory and co-author of research published in 2017.
VLF waves intended for submarines were rising through the atmosphere and interacting with charged particles in space. Nobody designed them to do anything in orbit. Nobody expected them to affect the Van Allen belts. Yet that’s exactly what happened.
How VLF Creates a Bubble Around Earth
As VLF transmissions escape our atmosphere, they create something like a bubble surrounding the planet. Picture an expanding sphere of radio energy pushing outward from Earth’s surface. When this energy encounters charged particles trapped in the Van Allen belts, it nudges them, affecting their motion and position.
Over time, all this nudging adds up. VLF waves have gradually pushed particles in the inner radiation belt farther from Earth. Scientists noticed that the outward extent of the VLF bubble corresponds almost exactly to the inner edge of the Van Allen radiation belts. Such a precise match seemed too perfect to be coincidental.
Dan Baker, director of the University of Colorado’s Laboratory for Atmospheric and Space Physics, gave this boundary a memorable name. He coined it the “impenetrable barrier” and speculated that without human VLF transmissions, radiation would stretch much closer to Earth’s surface.
In other words, our radio communications have inadvertently pushed dangerous radiation farther away from our planet. We built a shield without knowing we were building anything at all.
Evidence from Comparing Past and Present Data
How can scientists be sure VLF transmissions caused this shift? By comparing old measurements with new ones.
Satellite data from the 1960s recorded where the inner Van Allen belt began. Back then, VLF transmissions existed but at much lower power levels and frequencies. Modern Van Allen Probe data show the belt has moved considerably farther from Earth since those early measurements.
Correlation doesn’t always equal causation, but the timeline fits remarkably well. As VLF transmission power increased over the decades, the inner edge of the radiation belt retreated. Ground stations grew stronger. Submarine communication needs to be expanded. And up in space, an invisible barrier formed at the exact boundary where VLF energy runs out.
Researchers also examined other possible explanations. Solar activity fluctuates over time, which affects the Van Allen belts. But natural variation alone couldn’t account for the consistent outward shift at the inner boundary. Human-generated VLF remained the best explanation.
Could We Use VLF to Protect Earth?
If VLF accidentally created a barrier, could we intentionally use it to protect our planet? Scientists are exploring that possibility right now. Solar storms occasionally blast Earth with enormous clouds of charged particles. When intense storms hit, they can damage satellites, disrupt communications, and even affect power grids on the ground. Astronauts in orbit face elevated radiation exposure during severe events.
Plans are already underway to test VLF transmissions in the upper atmosphere. Researchers want to know if targeted VLF signals could strip away excess charged particles that accumulate during solar storms. Rather than waiting for dangerous radiation to dissipate naturally, we might actively clear it using radio waves.
Such technology could prove valuable for protecting satellites and spacecraft. Future long-duration missions beyond Earth might benefit from VLF-based radiation management. Even critical infrastructure on Earth’s surface might gain an extra layer of defense against space weather.
A History of Humans Changing Space
VLF transmissions aren’t our first impact on the space environment. Human activity has been altering conditions above Earth’s atmosphere since the late 19th century, though effects intensified dramatically in the mid-20th century.
During the 1960s, both the United States and the Soviet Union conducted high-altitude nuclear tests. Explosions at extreme altitudes created artificial radiation belts that persisted for months or years. Several satellites suffered major damage from these human-made radiation zones. Military planners also discovered that high-altitude nuclear detonations generate powerful electromagnetic pulses capable of disrupting electronics across continental-scale areas.
Other experiments have affected space as well. Scientists have released chemicals in the upper atmosphere to study how particles behave. High-frequency transmitters have heated portions of the ionosphere for research purposes. Each intervention taught us something about our near-space environment while simultaneously changing it.
VLF’s barrier effect differs from these deliberate experiments in one important way. Nobody intended to create it. For decades, it formed slowly and silently while militaries simply tried to talk to submarines. Only careful observation from orbiting spacecraft revealed what we had done.
A Shield We Never Knew We Needed
Scientists continue studying how VLF transmissions interact with the radiation environment around Earth. Every new observation adds to our understanding of both the Van Allen belts and the human-made barrier at their inner edge.
Some researchers focus on potential applications. If VLF can push radiation away, perhaps refined techniques could offer meaningful protection during dangerous space weather. Others concentrate on basic science, working to understand exactly how radio waves transfer energy to charged particles across such vast distances.
Meanwhile, VLF stations keep transmitting. Submarines still need communication. Military operations continue around the world. And up in space, an invisible bubble keeps holding back the inner reaches of a radiation belt that has circled Earth for eons.
We often think of space as beyond our reach, a place where human influence fades to nothing. But our radio waves have painted a different picture. They’ve shown that our planet doesn’t end at the atmosphere. Our impact extends thousands of kilometers higher, creating structures we never intended to build.
Perhaps most remarkable is how long this barrier existed before anyone noticed. For decades, it surrounded Earth while scientists looked in other directions. Only when NASA pointed sophisticated instruments at the Van Allen belts did the truth emerge. We had changed space without realizing it.
What else might we discover we’ve done? What other unintended consequences await detection? As our technology grows more powerful and our observation tools grow more precise, we may find that humanity’s footprint in space extends even further than we currently imagine. Some of those discoveries might concern us. Others might offer unexpected benefits.
One thing seems certain. We are no longer just inhabitants of Earth’s surface. Our influence reaches into the void, shaping an environment we are only beginning to understand.
