## Optical clock comparison for Lorentz symmetry testing

In his Special Theory of Relativity, Einstein formulated the hypothesis according to which the speed of light is always the same, no matter what the conditions are. It may, however, be possible that—according to theoretical models of quantum gravitation—this uniformity of space-time does not apply to particles. Physicists have now tested this hypothesis with a first long-term comparison of two optical ytterbium clocks at the Physikalisch-Technische Bundesanstalt (PTB). With these clocks, whose error amounts to only one second in ten billion years, it should be possible to measure even extremely small deviations of the movement of the electrons in ytterbium. But the scientists did not detect any change when the clocks were oriented differently in space. Due to this result, the current limit for testing the space-time symmetry by means of experiments has been drastically improved by a factor of 100. In addition to this, the extremely small systematic measurement uncertainty of the optical ytterbium clocks of le

### Optical clock comparison for Lorentz symmetry testing

**Wed 13 Mar 19** from Nature News

### Ultraprecise atomic clocks put Einstein’s special relativity to the test

**Wed 13 Mar 19** from ScienceNews

### Testing the symmetry of space-time by means of atomic clocks

In his Special Theory of Relativity, Einstein formulated the hypothesis according to which the speed of light is always the same, no matter what the conditions are. It may, however, be possible ...

**Wed 13 Mar 19** from Phys.org

Testing the symmetry of space-time by means of atomic clocks, Thu 14 Mar 19 from SpaceDaily

Testing the symmetry of space-time by means of atomic clocks, Wed 13 Mar 19 from ScienceDaily

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