# Scientific notation and negative numbers

My daughter is learning scientific notation in school, and her textbook says something to the effect of this:

Scientific notation is a method of writing numbers as the product of two factors where the first factor is a number greater than or equal to 1 but less than 10 and the second factor is a power of 10.

The teacher is taking this to mean that you cannot express a negative number in scientific notation. So that e.g.

$-4 * 10^{50}$

would not be valid scientific notation because -4 is less than 1.

Is there such a view of scientific notation? It certainly doesn't jive with my memory (or wikipedia), or is that description just deficient, and should better read:

Scientific notation is a method of writing numbers as the product of two factors where the first factor is a number whose absolute value is greater than or equal to 1 but less than 10 and the second factor is a power of 10.

And if it is a legitimate view, how do you express negative numbers in scientific notation?

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Teacher is wrong. –  mjqxxxx Dec 7 '12 at 4:53
Sounds like crap to me. –  copper.hat Dec 7 '12 at 4:56
Your reformulation is still inadequate, as it can't express $0$. –  Chris Eagle Dec 7 '12 at 8:14
Maybe the teacher can watch this: youtube.com/watch?v=0Elky_dDak0 –  Amzoti Dec 7 '12 at 9:34
@ChrisEagle, does Zero exist in science? has it been measured to perfect(mathematical) precision? Don't Probabilities get just incredibly small, never 'reaching' Zero. –  UnkleRhaukus Jan 20 at 17:23