Final answer:
The concept of measurement has advanced from basic human-based benchmarks to precise worldwide standards, such as the meter, defined by the distance light travels in a specific fraction of a second. In astronomy, relatable comparisons help illustrate the scale of measurements like the accuracy of an arcsecond. Earth's radius is a key value in measurements and conversions for various fields.
Step-by-step explanation:
Measurements of length have evolved from using human dimensions to precise worldwide standards such as the meter. The current definition of a meter is based on the distance light travels in a vacuum in 1/299,792,458 of a second. When it comes to astronomical measurements, astronomers use comparisons that are more familiar to help us understand the scales involved. For example, they might compare the measurement accuracy of 0.001 arcsec to the angle created by viewing a golf ball from across the Atlantic Ocean.
The radius of the Earth is known to be approximately 6,378 km, which can be expressed in multiple units, including meters and miles. This radius helps in various calculations, including the determination of the horizon distance from a given height above sea level using the formula D = 112.88 km x √h, where 'h' is the height in kilometers. Understanding such conversions and measurements is crucial in fields like astronomy, geodesy, and engineering.