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From a textbook of recent publication;

"The average radiation on the Earth’s surface is $340 W m^{−2}$."

I get the 340W. I presume m is meters. How does a minus 2 affect a meter, rather a square meter?

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  • $\begingroup$ Format error. The -2 is an exponent of m. Quote should be trailing quote paired with the first one. $\endgroup$
    – Bcwilmot
    Commented Sep 19, 2018 at 19:05
  • $\begingroup$ Why the tag is [negative-binomial]? $\endgroup$ Commented Sep 19, 2018 at 19:07

1 Answer 1

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It should be read as "per" and without the negative. So, in your case, "watts per square meter." You do the same thing with "miles per hour," which is $$ \frac{\text{miles}}{\text{hour}} = \text{miles} \cdot \text{hour}^{-1} $$

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  • $\begingroup$ So is the negative sign a typo? $\endgroup$
    – Bcwilmot
    Commented Sep 19, 2018 at 19:09
  • $\begingroup$ NO, that's what it means. Multiplication by negative exponents means dividing by the same power (without the minus sign). $\endgroup$
    – Randall
    Commented Sep 19, 2018 at 19:09
  • $\begingroup$ What is the difference between m2 and m-2 ? $\endgroup$
    – Bcwilmot
    Commented Sep 19, 2018 at 19:10
  • $\begingroup$ I own 2 square meters of property, and it cost me \$5 PER square meter. The first has units $m^2$ (how much I own) and the second $\frac{\text{dollars}}{m^2} = \text{dollars}\cdot m^{-2}$ (the rate at which I paid for it). $\endgroup$
    – Randall
    Commented Sep 19, 2018 at 19:10

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