Some Days Aren’t 24 Hours
A stellar day is how long it takes the Earth to complete a full rotation about its axis, measured with respect to a distant stationary reference point in space. But our traditional concept of a day has to do with our Sun, not the galactic center. For each turn of the Earth, there’s a time when the Sun is highest, and a day is simply the time it takes for the Sun to get back to that point. A solar day is not the same thing as a day kept by our clocks, since it uses the Sun as a reference point as to when noon is. But the length of time when the Sun is highest isn’t constant, changing up or down by about a minute over the course of a year. So do we really have 24 hours in a day? minutephysics host Henry Reich unravels the mystery.