A parsec (pc) is a unit of measurement used in astronomy to describe astronomical distances, particularly on cosmic scales. The term "parsec" is actually a contraction of "parallax of one arcsecond," which refers to the method by which this unit of distance is defined. A parsec is defined as the distance at which an object will appear to shift its position by one arcsecond (1/3,600th of a degree) as observed from Earth when the Earth is on opposite sides of its orbit (at an average distance of one astronomical unit, or about 93 million miles) from the Sun.
In more practical terms, a parsec is approximately equal to 3.09 × 10^16 meters or 3.09 × 10^13 kilometers.
To provide a sense of scale, some common astronomical distances expressed in parsecs include:
Parsecs are especially useful for describing distances between stars and galaxies, as astronomical distances can be incredibly vast, and using kilometers or even light-years can lead to unwieldy numbers.
A meter (m) is the base unit of length in the International System of Units (SI), which is the modern metric system used for scientific and everyday measurements in most countries around the world. The meter is defined as the length of the path traveled by light in a vacuum during a time interval of 1/299,792,458 of a second.
In more practical terms, a meter is approximately equal to:
Meters are commonly used for measuring various lengths and distances, including the dimensions of objects, the length of rooms or buildings, and distances between locations on Earth. It is a versatile unit of measurement that is widely used in science, engineering, construction, and everyday life.