How accurate was John Harrison's H4 marine clock

John Harrison's sea clock beat the required accuracy threefold

3× the required accuracy

Finding longitude at sea required a clock that lost or gained less than about six seconds per day. John Harrison's H4 sea clock eventually performed about three times better than that requirement.

India has rich wildlife — and severe habitat loss

4 of 34 biodiversity hotspots

India contains parts of four of the world’s 34 areas with especially rich and threatened wildlife. About one-third of its plant species are found nowhere else. This great variety of life exists alongside severe loss of natural habitat.

One change in DNA can distort red blood cells

Sickle-cell anemia can result from a change in just one DNA letter. That tiny change alters hemoglobin, the protein that carries oxygen in blood. The altered protein can form long fibers that bend red blood cells out of shape and make them more likely to block blood vessels.

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How accurate was John Harrison's H4 marine clock

John Harrison's sea clock beat the required accuracy threefold

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