### Next year for New Year's...

Dec. 31st, 2016 08:07 pmETA: 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. :-)