Since the effect of light’s momentum is so small — there’s a reason I can’t feel sunlight pushing on me, after all — sensitive enough equipment to capture it is only just becoming available. A Nature Communications paper out yesterday describes the ingenious experiment an international team of researchers came up with.The real trick is making sure any effects were really caused by imparted momentum from light, rather than just the side effects from heating the material as it absorbs light. To do that, the team constructed a mirror designed to absorb as little of the light as possible. Then they shot lasers at it.The mirror, upon feeling the shove from the laser’s photons, should theoretically start to ripple as waves propagate outward from the light like a pond that had rocks thrown in it. The researchers had installed acoustic sensors designed to pick up on those ripples (since sound waves are basically just ripples in the air ). These are tiny, tiny measurements, on the order of picometers , but the team picked them up.The best part is, when they compared the experimental results with predictions from computer models, the two lined up almost perfectly. It proved not just that the experimental setup worked and they really were measuring imparted momentum (not heating effects), but also that the current understanding of light momentum, which led to the models, is indeed correct.