And while we’re on the topic of things you can’t unknow and will forever stand out to you:
There’s a scene in Justice League (you can see it in some of the trailers) where Jim Gordon throws this big ass knife switch to turn on the Bat-Signal. And that scene is wrong and bad.
First off, no one uses big ass knife switches like that anymore because they are REALLY HECKING DANGEROUS.
There’s this shitty thing electricity can do where it jumps through the air and connects paths that aren’t supposed to be connected. That’s called an arc fault. Arc faults cause arc flashes and arc blasts. Aka horrific fireballs of death and maiming. (If you’ve ever gone to plug in an appliance and seen a little bitty explosion in the outlet, then you’ve seen this happen on the small scale. Bigger conductors and higher voltages make for much bigger potential booms.)
Also they have a whole lot of exposed copper and live parts for you to accidentally touch and fry yourself. And since this one’s outside, water making unwanted electrical connections and corroding the copper are also problems.
I put “knife switch” into google and the first thing it tries to give me is this:
That would be the modern version with a nice enclosure for safety. No live parts to stick your finger on and a box to hold in the worst of the arc flash should one happen. They make weatherproof ones, although the pictured one isn’t. Also I’d like to think it’s sufficiently industrial and clunky for a nice big dramatic throw the switch moment.
This brings me to problem two. That knife switch was installed upside down. What? How can you tell? Because Gordon throws the lever down to turn the signal on.
Look, there are very, very few operations where you want an electric device to fail in the on position. Safety dictates that it’s generally better for something to be accidentally turned off than on. And gravity dictates that it’s much easier for a switch to fall down than up. So up is alway the on position. Look at the switch I posted above. Up is on. Down is off. See also: probabily every light switch in your home, unless they are three way switches.
So yes, that scene is wrong and bad and when you become an electrican you cannot turn this part of your brain off.
This has been another episode of Batdad yells about bad electricity. Tune in next time for topics like “You can’t make an electromagnet with an aluminum baseball bat, Teen Wolf” and “I double checked Andy Wier’s math in The Martian and it was good and I was so very pleasantly surprised. Also, oh my god, I am such a nerd.”