Brooks Law basically states that adding people to an already late software project makes it later. But does it hold for other fields as well? I'd imagine in a construction project it would probably be almost completely expelled because the work requires less of an understanding of the project as a whole to contribute to. But does it hold in scientific fields? Do managers in other fields use similar maxims?
Actually, Brooks Law holds in construction as well, to a degree.
The difference is, where in technology Brooks applies to the learning curve, in the built environment it applies to limited physical space and/or sequencing.
In construction you're following a more rigid waterfall type of process (A must go before B must go before C, etc.) If the framing isn't done first you can't do the drywall. So you can add more people, but only to a point. Before too long you've got too many people bumping into each other and creating more confusion that helping. There's also safety issues to keep in mind. In most cases, crew sizes are determined around the most efficient, and safest numbers. Adding more increases the likelihood of an accident. Or having too many machines operating in the same place.
The alternative to Brooks is if you have a big enough area, you can crash the schedule by adding more crews in different locations to work on the same types of work (plumbers in bldg A AND bldg B instead of just bldg A), but that's not really the same as Brooks. That's more of a phasing issue.
My going-in position is always Duration = Work / FTE. It serves as a consistent, reliable benchmark from which you can adjust based on the plethora of factors that can affect the duration result.
The relationship between work and FTE is simply not linear. Performance variability; environmental factors (as Trevor indicated); the continuum between abstract, analytical work to repeatable, manual tasks; and simply random uncertainty will affect the validity of that relationship, causing the duration not to compress to the degree the formula states, remain constant, or even grow.
Assuming Brook's Law will always occur is a little analytically weak. I think no matter the industry or task it is worth challenging and analyzing the possible affects of crashing your schedule. But, to disregard the law wholesale is at your detriment.