Scamperings

...everyone should celebrate at solar midnight, not the midnight of their time zone. Set off fireworks. You'd hear the roar coming towards you at several hundred miles per hour, and set off your own, and hear it recede around the curve of the Earth.

ETA: Hahaha, wait, this depends on your latitude! Let's do some math. Let your latitude be the variable lat°; the speed of sound at 0° Celsius is sSnd = 330 m/s; the radius of the Earth at the equator is rEq = 6.4e6 m. At what latitude will the speed of midnight (sMdn) move at the speed of sound? The radius of the circular section of the Earth at our latitude (rLat) is defined by cos(lat°) = rLat / rEq. The speed of midnight at our latitude is (2 * PI * rLat) / (24 * 60 * 60 s), the circumference divided by a day. We can set that equal to 330 m/s.

sMdn = sSnd
(2 * PI * rLat) / (24 * 60 * 60 s) = 330 m/s
rLat = 330 * 24 * 60 * 60 / (2 * PI) m
rLat = 4.5e6 m
----
cos(lat°) = rLat / rEq
lat° = acos(4.5e6 m / 6.4e6 m)
lat° = acos(0.703125)
lat° = 45° (or 0.79 rad)

So here at 42° midnight moves faster than sound, but more than a few hundred miles north of here it would work. :-)