In 2017, NASA space probes discovered a massive man-made ‘barrier’ around Earth.
And tests have confirmed that it has an effect on space weather far beyond our planet’s atmosphere.
That means we’re not only changing the Earth so badly that scientists are calling for a whole new geological era to be named after us – our activities have also changed space.
But the good news is that unlike our influence on the planet itself, that giant bubble we’ve created in space works in our favor.
In 2012, NASA launched two space probes to interact with each other as they zoomed through Earth’s Van Allen belts at speeds of about 3,200 km / h (2,000 mph).
Our planet is surrounded by two such radiation belts (and a temporary third) – the inner belt extends from about 640 to 9,600 km (400 to 6,000 miles) above the Earth’s surface, while the outer belt reaches a height of about 13,500 to 58,000 km (8,400 to 36,000 miles).
In 2017, the Van Allen probes discovered something strange when they monitored the activity of charged particles in Earth’s magnetic field – these dangerous solar discharges were kept at bay by some sort of low-frequency barrier.
When researchers examined it, they found that this barrier had actively pushed the Van Allen belts off Earth over the decades, and now the lower boundaries of the radiation currents are actually farther from us than they were in the 1960s.
So what has changed?
A particular type of transmission called very low frequency (VLF) radio communication is much more common now than it was in the 1960s, and NASA’s team confirmed that they can affect how and where certain particles move in space.
In other words, thanks to VLF, we now have anthropogenic (or man-made) space weather.
“A number of experiments and observations have shown that under the right conditions, radio communication signals in the VLF frequency range can influence the properties of the high-energy radiation environment around the Earth,” said one of the team members, Phil Erickson of the MIT Haystack Observatory in Massachusetts, in 2017 .
Most of us will not have much to do with VLF signals in our daily lives, but they are a mainstay in many technical, scientific, and military operations.
At frequencies between 3 and 30 kilohertz, they are far too weak to carry audio transmissions, but they are perfect for broadcasting coded messages over long distances or deep underwater.
One of the most common uses of VLF signals is to communicate with deep-sea submarines, but because their long wavelengths can bend around large obstacles such as mountain ranges, they are also used to achieve transmissions over tricky terrain.
VLF signals were never meant to go anywhere other than Earth, but it turns out they leaked into space around our planet and lingered long enough to form a giant protective bubble.
When the Van Allen probes compared the location of the VLF bubble to the boundaries of the Earth’s radiation belts, they discovered what initially looked like an interesting coincidence: “The outer size of the VLF bubble almost exactly matches the inner edge of the Van Allen radiation belts, ”said NASA.
But once they realized that VLF signals can actually affect the movement of the charged particles in these radiation belts, they realized that our inadvertent human-made barrier was gradually pushing them back.
One of the teams, Dan Baker, of the Laboratory of Atmospheric and Space Physics at the University of Colorado, called this the “impenetrable barrier.”
While our protective VLF bubble is probably the best influence we humans have had on the space around our planet, it’s by no means the only one – we’ve been making our mark on space since the 19th century, and especially over the past 50 years. when nuclear explosions were all the rage.
“These explosions caused artificial radiation belts near Earth that caused extensive damage to several satellites,” the NASA team explained.
“Other anthropogenic effects on the space environment include experiments with the release of chemicals, radio frequency wave heating of the ionosphere and the interaction of VLF waves with the radiation belts.”
Astronomer Carl Sagan once wanted to find unambiguous indications of life on Earth from space – it turns out there are some if you know where to look.
The research is published by Science Space Reviews.
A version of this story was first published in May 2017.