Oct1st2009

Tiananmen Fireworks and CCTV broadcast delay

Watching the celebrations on the TV tonight and I noticed that the sound out the window was in perfect sync with the fireworks explosions on the TV.

So here is the challenge. I live near Ci Yuan Si. What is the CCTV broadcast delay then?

Tools available for use, google earth, calculator, brain.

3 Responses to “Tiananmen Fireworks and CCTV broadcast delay”


  1. Oct11th2009
    1 ibz Oct 11th, 2009 at 10:09 PM

    Assuming you mean “ci *yun* si” (慈云寺), which is a bit north of Sihui, doing a quick measurement on Google Earth yields 8.35 km from Tian’anmen. Speed of sound is 343 m/s at 20 °C (according to http://en.wikipedia.org/wiki/Speed_of_sound ; I assume the temperature at that time was not too far from 20). That gives me 8350 m / 343 m/s = 24.3 s.
    Not sure how the tall buildings in the CBD (which are in the way between the two points) affected the speed of sound, but I guess not much in terms of speed (they might divert it, but not so much slow it down).

    So I would guess their delay is somewhere between around 25 seconds.

    Nice problem. 🙂

  2. Oct13th2009
    2 richard Oct 13th, 2009 at 10:43 AM

    Yes Ci yun Si.. always get back to front…. 25 seconds… that seems a bit long? I was thinking 3-5 or so….?

  3. Oct14th2009
    3 richard Oct 14th, 2009 at 1:08 AM

    I guess I am about 500 metres north of Si Hui. Right on the corner of the 4th Ring Road and Chaoyang Lu…

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