[Thri4895o]

Network frequency changes and fluctuates around 50hz. This change is random and unique. It is also captured on video/audio recording as background hum.

This data is quite valuable. You can reconstruct exact time (and region) when any video was taken.

[127361]

The police keep track of this, and it can be used to validate audio recording evidence.

https://en.wikipedia.org/wiki/Electrical_network_frequency_a...

[toomuchtodo]

https://news.ycombinator.com/item?id=38161677

https://datethis.app/