Real prob: cig smoke

Ah, an asymmetric difference in momentum! That sounds very reasonalbe. I hadn't expected such a clear cut and plausable explanaition. The differences in preassure should, as you say, average out. But the higher momentum outside of course tips the balance to my disadvantage. I suppose that the wind on average does have higher speed when approaching the window from the outside, than when leaving it.

Yes it does work, Dirk! And it's so simple that I should've figured it out myself. Maybe it's the pleasant spinning in my head that the smoking causes that makes my thinking smokey? The momentum effect is probably very small in comparision.

Try with hemp for a change... The spinning is even more pleasant. And the momentum effect much bigger. And you won't get addicted. And don't get caught if your laws don't allow it yet.

Dirk Vdm