John Hadley, an English mathematician and astronomer, is credited with inventing the sextant in 1731.

The primary purpose of the sextant is to measure the angle between two objects, typically the horizon and a celestial body.

A sextant works by using a series of mirrors to reflect light from the horizon and a celestial body onto a graduated arc. The angle between the horizon and the celestial body can then be read from the arc.

The main advantage of the sextant over other navigation instruments is that it is more accurate. This is because it uses a series of mirrors to reflect light from the horizon and a celestial body, which allows for a more precise measurement of the angle between the two objects.

The sextant was first used for navigation in 1731, shortly after it was invented by John Hadley.

James Cook was the first person to use the sextant to circumnavigate the globe. He used it during his three voyages of exploration between 1768 and 1779.

The invention of the sextant had a profound impact on navigation. It made navigation more accurate, faster, and safer. This led to a significant increase in exploration and trade, and helped to open up the world.

The modern equivalent of the sextant is the GPS (Global Positioning System). The GPS is a satellite-based navigation system that provides accurate location and time information to users on Earth.

The sextant is still used today, although it is not as common as it once was. It is still used by some sailors and navigators as a backup to electronic navigation systems.

The sextant has some limitations. It can only be used during the day, when the sun is visible. It can also only be used in clear weather, as clouds can block the view of the horizon and celestial bodies. Additionally, it requires a skilled navigator to use it accurately.