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

Dec. 31st, 2016 08:07 pm**timmc**

...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

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

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. :-)