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How did man read the hour for the first time ?

The first known way invented by man to determine the hour between dawn and sunset was to set a stake into the ground:
It's shadow, called “sun-dial”, allows the hour of the day to be known.

Why are there 24 hours in a day ?

The Sumer people had a system of numbering based on the number 12. It has been used to divide the day in 12 hours for the daytime and 12 hours for the nightime, which is also easy to divide.

What is a clepsydra ?

It is a water-clock, already known by the ancient Chinese and Egyptians, that allows hours to be calculated day and night. Water flows out of a holed vessel, the sections of which indicate intervals of a given time.

Why is Christian Huygens well-known in the watch-making world ?

Christian Huygens was a physician and astronomer who invented the rating spring in 1675.
This constituted a significant progress as far as precision is concerned: the daily divergence, which was between 30 and 40 minutes was reduced to 4-5 minutes because of this mechanism.

Can you mention three out of the many inventions of Abraham Louis Breguet?

At random:

• the famous hands in the form of eccentric apples made blue with the hand
• the “tourbillon”, invented in 1801, that places all the pieces of the exhaust stroke in a turning cage, thus defying the impact of gravity.
• the perpetual calendar that takes leap years into account.
  

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