Blinking A Light With Ping

The Flashing Light Prize is on right now, and that means all our favorite geeks and YouTubers are aspiring to what could be done with a 555. The rules are simple: turn a light bulb on and off somehow. [Sprite_tm] is answering the call, and he’s blinking lightbulbs at the speed of light.

[Sprite]’s method of blinking a light is simple: Use an ESP32 development board to turn on a relay. At the same time, send a packet out to the Internet and through four servers spread across the globe. When the packet goes through servers in Shanghai, the Netherlands, to Hong Kong, to Germany, and finally Japan — and back again — the light bulb turns off. It’s a physical demonstration of the speed of light and the quality of undersea optical fibers.

This route is quite long, and a reasonable estimate for the one-way, great circle path from Shanghai to the Netherlands to Hong Kong to Berlin and finally to somewhere near Osaka is about 36,000 km. A round trip for this light bulb packet is 72,000 km, or about 0.2 light-seconds. There are delays, of course, from fiber and cables not going directly over the Himalayas, delays in routers, and the difference between the speed of light in a vacuum and the speed of light in glass fiber. Still, light is quick, and the light blinks at about 1Hz.

You can check out [Sprite]’s entry video for the Flashing Light Prize below.

24 thoughts on “Blinking A Light With Ping

    1. Laser is too difficult without some friends at the Apache Point Observatory.
      But bouncing radio signals would work!
      Moon is about 1.3 light-seconds away, fits right into the .5 to 2 Hz limitation.

    1. This.

      I wonder what the return packet order would be like.

      (00.00) First packet received = Third packet sent (ON)
      (00.52) Second packet received = Fifth packet sent (ON)
      (00.55) Third packet received = First packet sent (ON)
      (01.23) Fourth packet received = Second packet sent (OFF)
      (01.26) Fifth packet received = Sixth packet sent (OFF)
      (02.44) Sixth packet received = Ninth packet sent (ON)
      (03.99) Seventh packet received = Fourth packet sent (OFF)

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