Why do so many public buildings want you to use the revolving doors rather than the regular doors? –Seamus McCafferty, Hoboken, New Jersey
Best of Chicago voting is live now. Vote for your favorites »
As with many things, there are two reasons–the ostensible reason and the real reason. The ostensible reason is that the revolving doors create an air trap. Since the interior of the building is never directly exposed to the outdoors, there’s less chance of all that expensively heated or cooled air getting out and running up your utility bill. An alternative way of accomplishing the same thing is a vestibule, where you have to pass through two sets of doors to get inside. Another reason for revolving doors is to prevent wind from howling down (or up) the elevator shafts and stairwells and blasting out (or in) the doors due to indoor-outdoor pressure differentials.
Uh, C…. you wouldn’t happen to work for Vice President Quayle’s office, would you? As anybody with two operating brain cells has already figured out, the lettering is reversed so it’ll appear correctly in the rear-view mirror of any motorist in front of the ambulance.
The carbon dioxide bubbles in beer and soft drinks work the same way. Before you uncap the bottle, the pressure inside keeps all the CO2 in solution. After uncorking, the reduced pressure enables the gas to slowly boil away, which is where the nucleation sites come in handy. If you want to see some serious bubble action, try sprinkling salt in your beer. The salt provides numerous nucleation sites, producing not only a fascinating demonstration of physics, but heaps o’ fun besides.
