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Ah, sorry - not criticising, just reminding :) There was an article on HN recently on how important it is to follow this, and how life saving it can be.

If there is a flash and you hear no sound, it doesn’t mean it’s safe either - sound travels 300m/s, so if there was an explosion 2.5miles away, you would only see bright visuals on the sky, no sound, for the first 10-13sec, and then the shockwave would hit...




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