Why are negative numbers needed?

Answer 1

Without negative numbers ...

-- If you had $17 in the bank and withdrew $20 from an ATM, the bank would have

no idea how much you owe them. Maybe that would be a good thing.

-- If you lived in a place where they do the temperature in Celsius, then during

most of the Winter, especially when water was solid, they could never tell you

the temperature on the radio, and you wouldn't know what to wear to school.

-- If you were a Physicist, doing motion experiments throwing baseballs and

rocks up in the air, and you decided to measure all your vector quantities

towards up, then you could never measure anything once it started falling, and

you couldn't describe it to anyone else. Once the rock or the Baseball reached

the top of the toss, everything after that would just be a meaningless blur.

-- If you were rich and owned a lot of stocks and bonds, and one day you pick

up the newspaper to see how you did in the market the day before, some of

them would have numbers to show how much they gained, and the rest would

be blank.

-- If you plugged a lamp into an electrical outlet in your house and turned it on,

you would have a real mess. The voltage on the hot side of the circuit would be

+117 volts, but only for 0.0083 of a second, and then what ? It would be time

for the AC voltage to turn around and go the other way, but there would be no

number to describe it, so it would just shut off for the next 0.0083 of a second.

Can you see where this would lead ? You'd have the electricity flowing into your

house and then shutting off, flowing in and shutting off, every 0.0166 second,

and before you know it, your house would be full of electricity and none of it

could get out!

Boy are we lucky that we have negative numbers!