Something is moving gigantic boulders along the ridges of rocks that line the cliff tops on the Aran Islands. And I mean gigantic. We're talking 40-, 50-, 60-tonne monsters here, not pebbles. One theory is that waves are doing this. Thing is, current mathematical understanding of waves says this isn't possible. The only kind of wave powerful enough to lift or push boulders of such mass inland is a tsunami. But a tsunami hasn't hit Ireland since 1755. That's when a devastating earthquake virtually destroyed Lisbon and sent a tidal wave roaring across the Atlantic. My sister Rónadh, a professor of geosciences, has been working on these cliff ridges for nearly ten years. She has proven that storm waves are indeed moving these rocks. To support her research, I have been using my drones to photograph the enormous boulders and the inland ridges they form. We've been building 3D models from those images. We recently modelled a behemoth weighing an estimated 600-plus tonnes. We know this giant moved four meters in the 2013/2014 storms. Storm waves breaking over the cliffs continue to push these boulders around. And the ridges appear to be migrating deeper inland. While that seems incredible, given the size and mass of the boulders, the locals will tell you the giant rocks are moving. Nobody has ever seen this happen with their own eyes. You'd have to be some kind of unfortunate to be out in a storm powerful enough to generate such violent forces. Put bluntly, and with no small measure of brotherly pride, Rónadh's work is going to help change our mathematical understanding of waves. 1 + 1 will still equal 2, when all is done. But our ability to calculate the behaviour of waves will be improved. That's big. Among other things, it will allow us to build more effective coastal defenses in areas that are vulnerable to flooding and erosion.