Why isn’t the Earth per­fectly spher­i­cal?

BBC Earth (Asia) - - Q & A -

The Earth’s ro­ta­tion cre­ates an out­ward force per­pen­dic­u­lar to its ro­ta­tion axis which, cru­cially, is pro­por­tional to the dis­tance from that axis. Hence, the high­est force is felt at the Earth’s equa­tor, while the force is zero at the poles. Since the Earth is not per­fectly solid through­out, this force re­sults in the Earth be­ing ‘squashed’ into a slightly flat­tened sphere. The ef­fect is quite small. The di­am­e­ter at the poles is about 12,714km and at the equa­tor is about 12,756km; hence the amount of flat­ten­ing (or ‘oblate­ness’) is only about 0.3 per cent. How­ever, this equa­to­rial bulge (42km) is about twice the dis­tance from the top of Mount Ever­est to the deep­est part of the ocean. AGu

An­i­mals with flea al­ler­gies will suf­fer from se­vere itch­ing, and may even de­velop a form of der­mati­tis after be­ing bit­ten

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