Second

High school (ages 12+)
Mathematics & Numbers

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/second

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. What is the SI base unit?The second (s) is the SI base unit of time
2. How was the second originally measured?At first, people counted seconds by dividing a day into 24 hours, 60 minutes, and 60 seconds. This came from watching the Earth spin. But the Earth's spin can change a little, so it wasn't perfect.
3. Why do we use atomic clocks instead of the Earth's rotation?Because the Earth's rotation can speed up or slow down, it isn't a steady clock. Atomic clocks use atoms that vibrate the same way every time, giving a constant and reliable time.

International System of Units (SI): The modern metric system of measurement used worldwide.
Caesium-133 Atom: A specific type of atom whose stable atomic vibrations define the second.
Hertz (Hz): A unit of frequency, representing cycles or oscillations per second.
Universal Time 1 (UT1): A time scale based on the Earth's rotation, used in astronomy and navigation.