A clock at a higher altitude ticks faster than one at a lower altitude, in accordance with Einstein’s theory of general relativity. The outstanding stability and accuracy of optical clocks, at 10⁻¹⁸ levels^1,2,3,4,5, allows height differences⁶ of a centimetre to be measured. However, such state-of-the-art clocks have been demonstrated only in well-conditioned laboratories. Here, we demonstrate an 18-digit-precision frequency comparison in a broadcasting tower, Tokyo Skytree, by developing transportable optical lattice clocks. The tower provides the clocks with adverse conditions to test the robustness and a 450 m height difference to test the gravitational redshift at (1.4 ± 9.1) × 10⁻⁵. The result improves ground-based clock comparisons^7,8,9 by an order of magnitude and is comparable with space experiments^10,11. Our demonstration shows that optical clocks resolving centimetres are technically ready for field applications, such as monitoring spatiotemporal changes of geopotentials caused by active volcanoes or crustal deformation¹² and for defining the geoid^13,14, which will have an immense impact on future society.

根据爱因斯坦的广义相对论，高海拔的时钟比低海拔的时钟的滴答声更快。光学时钟的出色稳定性和准确性（在^1,2,3,4,5 10 ^-18级）可以测量1厘米的高度差⁶。但是，仅在条件良好的实验室中证明了此类最新时钟。在这里，我们通过开发可移动的光学晶格钟，展示了广播塔Tokyo Skytree中18位精度的频率比较。该塔为时钟提供了不利条件来测试坚固性，并为450 m的高度差提供了测试（1.4±9.1）×10 ^-5的重力红移的条件。。结果提高了地面时钟比较^7,8,9一个数量级，可与空间实验^10,11相提并论。我们的演示表明，解析度为1厘米的光学时钟在技术上已准备就绪，可用于现场应用，例如监视由活火山或地壳变形引起的地势时空变化¹²以及定义大地水准面^13,14，这将对未来社会产生巨大影响。