The SI definition of a second, available at https://www.bipm.org/documents/20126/41483022/SI-Brochure-9.pdf/fcf090b2-04e6-88cc-1149-c3e029ad8232 https://www.bip

The SI definition of a second, available at https://www.bipm.org/documents/20126/41483022/SI-Brochure-9.pdf/fcf090b2-04e6-88cc-1149-c3e029ad8232 https://www.bipm.org/documents/20126/41483022/SI-Brochure-9...., section 2.3.1, does not reference our particular planet, nor any particular means of measurement, nor does it have to. In principle this frequency can be measured in any inertial frame. Seconds are not defined on Earth specifically.