Scientists initially faced difficulties in accurately determining the value of the speed of light due to a variety of reasons. Here are some key factors that contributed to these challenges:
Limited Measurement Techniques: Early attempts to measure the speed of light relied on direct observations and measurements, which were hindered by the lack of precise instruments. The available technologies were not capable of accurately measuring short time intervals or long distances, which made it challenging to obtain reliable measurements.
Inherent Speed of Light: The speed of light is exceptionally fast, approximately 299,792,458 meters per second in a vacuum. This high speed presented challenges in directly measuring it, as the time required for light to travel even relatively short distances was difficult to measure accurately.
Conceptual Difficulties: Determining an accurate definition of the speed of light posed conceptual difficulties for scientists. Initially, the nature of light was not well understood, and there were debates regarding whether light propagated instantaneously or had a finite speed. These conceptual uncertainties made it challenging to devise precise measurement techniques.
Regarding your second question, while the phrase "the distance traveled by light in one second" might seem like a straightforward definition, it is not a practical basis for measuring the speed of light. The definition needs to be established independently of the value being measured. Using the speed of light to define the speed of light would create a circular argument, lacking an external reference point. Thus, scientists needed to develop alternative methods and techniques to determine the value of the speed of light independently, rather than using the value itself as part of the definition.