One day is exactly 24 hours, which is equal to 86,400 seconds. This measurement is based on the average time it takes for the Earth to complete one full rotation on its axis with respect to the Sun.
While we commonly think of a day as being exactly 24 hours, it's important to understand the distinction between different types of days:
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Solar Day: This is the time it takes for the Sun to appear in the same position in the sky (e.g., from noon to noon). Its length can vary slightly throughout the year due to the Earth's elliptical orbit and axial tilt. The 24-hour day is an average of the solar day throughout the year.
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Sidereal Day: This is the time it takes for the Earth to complete one rotation relative to the distant stars. It's about 23 hours, 56 minutes, and 4 seconds long, which is slightly shorter than a solar day.
In summary, when people ask "how long is one day?", they are typically referring to the average solar day, which is 24 hours. This provides a consistent measurement for our daily activities and scheduling.
