# Why is the squared meters negative?

1. Apr 2, 2015

### R_Ham

Hello,
I work in energy auditing. I noticed a lot of the standards I am given for lighting, etc are in Watts per negative square meter: W·m-2.

Does anyone know what this means? Why isn't it just in W·m2 ?

2. Apr 2, 2015

### Bandersnatch

$a^{-n}$ means the same as $1/a^n$

Anything raised to negative power is the same as a fraction with the thing being in the denominator.

So what does $Wm^{-2}$ mean?

3. Apr 2, 2015

### Staff: Mentor

The dot between the w and the m is times, not divided by. I'm not sure why you would write it that way, but W·m-2 = W/m2

4. Apr 2, 2015

### R_Ham

Yes, this all makes sense now. Can't believe I didn't realise that one -_- . I don't know why, but the standards are just always written like that W·m-2.