Friday, July 22, 2016

Brilliant Ideas that will Never Work: murder-proof knife

While writing my previous blog post, I came up with an idea for a knife that can't be used as a murder weapon.

If the blade of the knife touches something that is approximately 37 degrees celsius (i.e. the temperature of the human body), the blade retracts, making it impossible to use it to cut or stab anything.

We already have thermometers with protruding metal probes that detect the temperature of the thing they're touching (e.g. meat thermometers). We already have switches that switch on and off when the thermometer they're attached to crosses a certain threshold (i.e. thermostats). We already have knives with blades that retract. So combine all this technology to make a knife whose blade retracts when it touches something at a temperature near 37 degrees.

Food shouldn't be near 37 degrees, at least not for any significant amount of time.  It should either be stored below 4 degrees or cooked above 60 degrees. If the food you're trying to prepare is 37 degrees, it needs to be either heated up or cooled down.

If you're using the knife for something other than food preparation, the thing you're cutting is probably room temperature.  Room temperature is about 20 degrees, and 37 degrees is uncomfortably hot for ambient temperature. If the ambient temperature is 37 degrees, you really should move to somewhere cooler before you get heatstroke.

I don't deny the possibility that there might be some specialized activities beyond the scope of my imagination that legitimately require the use of a knife at 37 degrees celsius. And they can use a specialized, non-murder-proof knife for those specialized activities. But for ordinary household use, knives could be made murder-proof.

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