"When highly theoretical phenomena are talked about in engineering terms" That may be true, but you also mention that measuring tiny transient forces is incred

"When highly theoretical phenomena are talked about in engineering terms" That may be true, but you also mention that measuring tiny transient forces is incredibly hard. Thus, the only way to actually get an accurate measurement for this thing is to attempt to scale it up until the force is either unambiguous or the confounding culprit can be found. You've got to try to amplify the signal. I also don't get the impression that these folks are dummies. I'd be surprised if they haven't done experiments to attempt to rule out electromagnetic effects. Simple ones would involve moving stuff around, doing this in the presence of various magnetic fields imposed by outside sources to see if the underlying effect is still there, etc. Edit: some more info here: https://en.wikipedia.org/wiki/Woodward_effect#Test_devices https://en.wikipedia.org/wiki/Woodward_effect#Test_devices In particular: "In 2004, Paul March of Lockheed Martin Space Operations, who started working in this research field as of 1998, presented successful replication of Woodward's previous experiments at STAIF." There are a few other less conclusive attempts at replication, but only one claimed negative result. But as you say, measuring forces this tiny is hard.