Answer:
A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation.
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Explain What effect do rising carbon dioxide (CO2) emissions have on aquatic
species whose shells and bones are composed of calcium carbonate (CaCO3)?
Answer:
As human activities like driving have pumped carbon dioxide into the air, the oceans have absorbed a large portion of this gas. Richard Feely of the National Oceanic and Atmospheric Administration and his colleagues wanted to know what the effects might be on certain ocean animals that are sensitive to the chemistry of the water they live in.
Many mollusks, corals, and single-celled creatures called foraminifera and coccolithophorids use ingredients in seawater to build their shells and other hard parts. Specifically, they pull "carbonate" ions out of the water and make a hard material called "calcium carbonate."
As you might guess from the name, carbon plays an important role in the chemical reactions that allow these animals to make their homes. But, if the amount of carbon dioxide in the seawater increases above a certain level, these conditions lead to a different set of reactions that don't produce carbonate ions. In parts of the ocean that don't have enough carbonate ions, calcium carbonate shells start to dissolve.
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