What is an inch?
An inch is a length unit normally used in the United States and, occasionally, in the United Kingdom. It is defined as a twelth (1/12th) of a foot. The inch is normally subdivided into fractions of an inch such as the ½, ¼ and ⅛.
Historically, an inch was originally based on the width of a man's thumb. The inch is still commonly used in the United States for everyday measurements and worldwide for the size of TV and computer screens and clothing.
Inches are used in combination with other units of imperial measurement such as feet and yards. For example, a standard door in the United States a football field is 100 yards long or 300 feet or 3,600 inches.
What is a Parsec?
A parsec is a unit of length used in astronomy to measure vast distances between celestial objects. The term "parsec" is derived from the words "parallax" and "second," which refer to the method used to calculate this unit. Specifically, a parsec is defined as the distance at which an object would have a parallax angle of one arcsecond when observed from opposite ends of Earth's orbit around the Sun.
To understand the concept of a parsec, it is important to grasp the idea of parallax. Parallax is the apparent shift in the position of an object when viewed from different vantage points. In the case of astronomy, scientists use the Earth's orbit as a baseline to measure the parallax of distant stars. By observing a star from opposite ends of Earth's orbit, astronomers can calculate the angle of parallax and subsequently determine the star's distance.