# Thread: What watt & the solar constant?

1. ## What watt & the solar constant?

Hi could someone please help explain this equation to me?

Note that multiplying the units W m −2 by m 2 gives W because:

I get that (for example) 1370 W m $^-2$ is the same as saying 1370 W per metre squared, but I'm not very sure what a m $^-2$ on it's own is? If it's not “per meter squared” then perhaps it represents 'one metre to the minus 2”?

However if I were reading this literally from what I've learned so far the $m^-2$ x $m^2$ part would read per metre squared times (one) metre squared (which doesn't seem to make any sense.) Of course getting lost here means I'm lost on the rest of the equation too.

I admit I'm a bit stuck here.

2. If it's not “per meter squared”
It is.

I think you might be over-thinking this a bit. Units are a lot like variables, in terms of their algebra. I can take meters plus meters and get meters. I can divide meters squared by meters and get meters. I can only add two quantities-that-have-units together if they have the same units (just as in adding like terms with powers of x or y). Finally, there are certain functions for which the argument must be unit-less: the exponential function, the trig functions, the logarithm function, and others.

3. Lol. I think I must be dumb. I probably am over thinking it. But it's still not clear to me how this state of affairs works.

Breaking it down and explaining it bit by bit might help, but of course I can't expect anyone to do this.

You may have to take into account that I'm a total n00b at maths and science (a mature student), so learning probably involves a little more effort for me.

4. Originally Posted by jebus197
Lol. I think I must be dumb. I probably am over thinking it. But it's still not clear to me how this state of affairs works.

Breaking it down and explaining it bit by bit might help, but of course I can't expect anyone to do this.
If you don't ask, you definitely can't expect it.

You may have to take into account that I'm a total n00b at maths and science (a mature student), so learning probably involves a little more effort for me.
We can work with that, if you're willing to work with that.

Check this out, and then check this out. In both links, don't worry if you don't understand everything. Do the best you can. Then come back here and ask questions.