Arcsecond
A unit of angle equal to 1/3600th of a degree, used in astronomy and precision measurements to describe tiny angular separations in the sky.
A unit of angular measurement equal to one-sixtieth of an arcminute, or 1/3600th of a degree. Commonly abbreviated as arcsec or ", it is the standard unit for measuring very small angles in astronomy, surveying, and optics. One arcsecond subtends approximately 1 meter at a distance of 200 kilometers.
What this means in real life
If you held a coin at arm's length, its width spans roughly 200 arcseconds. A telescope capable of resolving objects separated by one arcsecond can distinguish two stars that appear extremely close together in the night sky.
What it isn’t
It is not a unit of time (despite the word 'second'). An arcsecond measures angle, not duration—it has nothing to do with seconds on a clock.
Commonly misused online
People sometimes confuse arcseconds with arcminutes or degrees, leading to wildly incorrect claims about telescope resolution or star positions. Social media posts often misquote precision measurements by an order of magnitude.