Test of general relativity by a pair of transportable optical lattice clocks

  title={Test of general relativity by a pair of transportable optical lattice clocks},
  author={Masao Takamoto and Ichiro Ushijima and Noriaki Ohmae and Toshihiro Yahagi and Kensuke Kokado and Hisaaki Shinkai and Hidetoshi Katori},
  journal={Nature Photonics},
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 – 5 , allows height differences 6 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… Expand
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