University of Alberta Study: Forces Deep Inside Earth Are Shifting Day Length by Milliseconds
A groundbreaking Canadian study published in Nature in September 2026 has found that forces deep within Earth’s core are subtly altering the planet’s rotation, changing the length of a day by several milliseconds over decades. Yahoo News
Led by doctoral candidate Huifeng Zhang and co-authored by Mathieu Dumberry at the University of Alberta, the research analysed six decades of observational data to identify three competing forces driving the shift: gravitational coupling between the inner core and the mantle (the primary driver), electromagnetic coupling from the outer core’s magnetic field, and topographic coupling, both of which act in opposing directions.
Between the early 1970s and 2021, these core-driven processes produced measurable changes in day length previously unexplained by short-term atmospheric effects or long-term tidal interactions with the Moon.
Zhang described the findings as bringing “a more coherent picture of Earth’s deep interior”, a region thousands of kilometres beneath the surface that is otherwise impossible to observe directly.
While the changes will not impact daily life, they carry significance for precision timekeeping and planetary science. Zhang is now investigating whether similar deep-Earth processes explain a recurring six-year oscillation in day length.
Read our previous article on Earth and Science here.
