The "actus" was a unit of length used in ancient Rome. It was primarily a measure of distance and was approximately equivalent to 120 Roman feet or about 35.5 meters (116.5 feet) in modern measurements.
The actus was commonly used for various purposes in ancient Rome, including land measurement, surveying, and property boundaries. It was also used in the construction of roads, aqueducts, and other civil engineering projects.
It's important to note that ancient Roman units of measurement, including the actus, were not standardized in the same way that modern units are today. Therefore, the exact length of an actus could vary in different regions and over time.
The use of the actus and other Roman units of measurement has largely been replaced by modern metric and imperial systems in contemporary times, but they remain of historical interest and can still be encountered in the study of ancient Roman culture and history.
A megaparsec (Mpc) is a unit of measurement used in astrophysics and cosmology to express vast distances on cosmic scales. It is equal to one million parsecs. A parsec (pc) is a unit of length used in astronomy to describe astronomical distances, and it is approximately equal to 3.09 × 10^16 meters or 3.09 × 10^13 kilometers.
So, a megaparsec is equivalent to:
1 megaparsec (Mpc) = 1,000,000 parsecs (pc)
Megaparsecs are typically used to describe distances between galaxies and galaxy clusters in the universe. Since astronomical distances are extremely large, the parsec and its multiples, such as the megaparsec, provide a convenient way to express these distances without dealing with unwieldy numbers of kilometers or light-years. Cosmologists often use megaparsecs when discussing the large-scale structure of the universe, the size of galaxy clusters, and the expansion of the cosmos.