Galileo Galilei is the correct answer for the question.

Explanation:
Galileo Galilei, an Italian physicist, astronomer, and mathematician, is credited with the discovery that a pendulum of a given length always takes the same time to complete one oscillation. This discovery is known as the isochronism of the pendulum.

What is a Pendulum?
- A pendulum is a weight suspended from a fixed point so that it can swing back and forth under the influence of gravity.
- It consists of a string or a rod with a mass (bob) attached to its end.

Galileo's Experiment:
- Galileo began studying the motion of pendulums in the late 16th century.
- He conducted experiments using pendulums of different lengths and observed their behavior.
- Galileo discovered that regardless of the amplitude (the angle of swing) or the weight of the bob, the time taken for a pendulum to complete one full swing remained the same.
- He used his own pulse as a timekeeping device to measure the time accurately.

Galileo's Observations:
- Galileo observed that the time taken for a pendulum to complete one full swing is independent of the amplitude (angle of swing).
- He found that the only factor affecting the time of swing is the length of the pendulum.
- Galileo observed that if the length of the pendulum is increased, the time of swing also increases, and if the length is decreased, the time of swing decreases.

Implication of Galileo's Discovery:
- Galileo's discovery of the isochronism of the pendulum had significant implications.
- It led to the development of accurate timekeeping devices, such as pendulum clocks.
- Pendulum clocks became widely used in the 17th century and were the most accurate timekeeping devices until the invention of the quartz clock in the 20th century.

Conclusion:
Galileo Galilei's experiments and observations on pendulums led to the discovery that a pendulum of a given length always takes the same time to complete one oscillation. This discovery revolutionized timekeeping and laid the foundation for the development of accurate clocks.

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