During the COVID-19 lockdowns, something remarkable happened: Earth became quieter — not metaphorically, but physically. With roads empty and industries paused, researchers noticed a dramatic drop in seismic noise. But how do we monitor a planet’s “silence”? Surprisingly, the answer involves satellites orbiting far above us.
A Global Drop in Vibrations
Seismologists across the world reported a significant decrease in high-frequency vibrations in the Earth’s crust. These are typically caused by human activity — traffic, trains, factories — and they create constant, low-level seismic noise. When lockdowns began in early 2020, this noise dropped by up to 50% in some urban areas.
This gave scientists a unique opportunity to study Earth’s natural seismic signals, which are usually masked by human-generated noise. More importantly, it offered new insight into how human activity physically impacts the planet — even in ways we cannot hear.
Satellites as Silent Observers
While seismographs recorded tremors below, satellites such as ESA’s Sentinel-1 and NASA’s GRACE-FO monitored Earth from above. These satellites can detect ground movement, infrastructure shifts, and even subtle changes in land use. Combined with seismic data, they help scientists paint a fuller picture of human impact — not just in sound but in vibrations, density, and even heat.
Some satellites are now helping urban planners identify “hotspots” of noise and vibration. Others assist in studying how reduced human activity affects wildlife movement and air quality. In essence, spaceborne sensors are becoming essential tools in designing quieter, more sustainable cities.
Toward a Quieter, Greener Future
Now, as life resumes, scientists hope to use lessons from the pandemic to rethink urban design. Could cities be built to reduce seismic and acoustic impact? Could satellite data guide the development of quieter transport systems?
What’s clear is that the view from space is more than just about stars — it’s a mirror showing how we live on Earth. And sometimes, it takes silence to truly hear what our planet is saying.
