Below zero

About this video

The counting numbers stop at zero, but the world doesn't. On a cold night a thermometer falls from 3 degrees past 0 and keeps going: -1, -2. Those are negative numbers, and together with zero and the counting numbers they make the integers: ..., -2, -1, 0, 1, 2, ... This short animation starts with that thermometer, then lays the same numbers along the number line, where the negatives sit to the left of zero.

Every number has an opposite on the other side of zero, just as far away: 3 and -3 are opposites. Add a number and its opposite and you land back on zero, so 3 + (-3) = 0. Negative numbers also fix a gap in subtracting. With only counting numbers, 3 - 7 has no answer, because you can't take seven away from three. On the number line it's easy: start at 3, hop seven steps left, and you reach -4. With negatives, every subtraction has an answer. This video goes with the Below Zero and Opposites lessons of Numbers Level 1 on Knaph.

Transcript

1. 0:00What is colder than zero degrees?
2. 0:04Go below zero and the numbers carry on. Minus one, minus two.
3. 0:10On the number line, negatives sit left of zero.
4. 0:15Three and minus three are opposites, just as far from zero.
5. 0:21A number plus its opposite is zero.
6. 0:26And now you can take away more than you have.
7. 0:31Below zero, the numbers go on.