There are many things about modern life we take for granted – perhaps none more so than the vast electrical grids that power so much of it. But for many years, these grids have been doing something strange. Every 60 seconds, they pulse – a tiny change in the frequency that subsides only to recur 60 seconds later.
And it's not just one power grid. Around the world, multiple power grids – physically isolated from each other – have been found doing the same thing. It's precise, and it has persisted, year after year, for more than a decade. This precision suggests that it's not an accident, but it has remained a curiously enduring puzzle.
Now, scientists think they have found the answer – and it's surprisingly mundane. Every minute, some uninterruptible power supplies – the backup systems used in places like hospitals, data centers, and research facilities – perform routine battery checks, creating small but measurable surges in electricity demand - and for those UPS systems - it's like clockwork.
"Even benign control routines can become systemically relevant when many devices act coherently," writes a team led by physicist Dirk Witthaut of the University of Cologne, Germany, in a paper published in Nature Energy. "Unintended synchronization can generate recurrent and potentially amplified oscillatory behavior in large-scale cyber-physical energy systems."
