Units of Time

Study Notes

Time measurement study is called horology
Measuring of time started over 30,000 years ago
Early societies used astronomical objects like the moon, sun, and stars to determine time
Sundials and moon patterns were used to estimate time
Later, standard units and clocks were developed to measure time
Today, time is measured based on the vibrations of the cesium-133 atom

Second: base unit of time, used for very small intervals (blinking, breathing, snapping)
Minute: larger than a second, smaller than an hour, used for small intervals (drinking coffee, taking a walk, boiling water)
Hour: largest unit of time, used for large intervals (baking a cake, studying)
Day: made up of 24 hours, used for intervals like waiting to hear back from an interview
Week: made up of 7 days, used for intervals like using products within a week
Month: made up of 30 or 31 days, used for intervals like salaries being credited
Year: made up of 365 days, used for intervals like birthdays

To convert units, multiply or divide by a conversion factor
Examples of conversions:
- 1 minute = 60 seconds
- 1 hour = 60 minutes
- 1 hour = 3600 seconds
Conversion steps:
1. Recall the relation between the units
2. Smaller to larger unit, divide
3. Larger to smaller unit, multiply
4. Write the correct unit in the answer

Convert 720 seconds to minutes: 720 / 60 = 12 minutes
Convert 18 minutes to seconds: 18 x 60 = 1080 seconds
Convert 185 minutes to hours and minutes: 185 / 60 = 3 hours 3 minutes
Convert 20 days to hours: 20 x 24 = 480 hours
Convert 7893 seconds to hours, minutes, and seconds: 7893 / 3600 = 2 hours 11 minutes 33 seconds