地心

the earth's core / geocentric

-ly / structural particle: used before a verb or adjective, linking it to preceding modifying adverbial adjunct

earth / ground / field / place / land / CL:片[pian4]

heart / mind / intention / center / core / CL:顆|颗[ke1],個|个[ge4]

gravitation

earth's gravity

geocentric latitude (i.e. angle between the equatorial plane and straight line from center of the earth)

geocentric theory