Time

What are the smallest and largest units of time?
• Science Channel

1. Time might seem like a rather mysterious concept. After all, we can't see it or feel it, and we also can't stop it. It's infinite. When it comes to measuring time, most of us do it in common increments like minutes (how long it takes to run a mile), days (when we go to work) and years (how often we celebrate another birthday). But just how tiny and how massive can measurable units of time be?

Some of the following units of time you're already familiar with, but some may be eye-openers. Let's start from the shortest and go toward the longest.

• 1 picosecond (one-trillionth of a second) is currently the shortest period of time able to be accurately measured.
• 1 nanosecond is one-billionth of a second.
• 1 microsecond is one-millionth of a second.
• 1 millisecond is one-thousandth of a second. A photo taken in one-thousandth of a second will be able to catch all the motion of a person.
• 1 centisecond is one-hundredth of a second, which is the amount of time a stroke of lightning flashes.
• 1 decisecond (one-tenth of a second) is how long it takes to blink an eye.
• 1 second is 9,192,631,770 oscillations in an atomic clock of an atom of cesium-133.
• 1 minute is 60 seconds.
• 1 hour is 60 minutes.
• 1 day is 24 hours, or one revolution of the Earth on its axis.
• 1 week is seven days.
• 1 year is 365.24 days, or one orbit of the Earth around the sun.
• 1 decade is 10 years.
• 1 century is 100 years.
• 1 millennium is 1,000 years.

Of course, most of these are simply too small or too large for us to measure on our clocks or calendars, but it's interesting to think about. How many picoseconds do you think passed while you were reading this sentence?

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