DIY torch

Hand sanitizer is mostly ethyl alcohol—it burns fairly nicely. Oh, but don’t play with fire. If you put this stuff on a roll of paper towels, it should make a great torch. It would probably have more of a blue color though.

Actually, you can just squirt some hand sanitizer on a cement floor and light it on fire.

WiFi Radar

This is a “Riley hack”. Since the power is out in the building, she hacks into the wifi routers for the nearby buildings. By looking at the strength of the wifi signals that go through the building, she can sort of judge where people are moving.

Oh, this is crazy? No, this is based on some real stuff.

https://gizmodo.com/scientists-are-turning-wifi-routers-into-creepy-radar-c-1794961990

DIY Glow stick

That glow stick that you use for Halloween is just a mixture of two chemicals. In that particular chemical reaction, it is an example of chemiluminescent—a chemical reaction that produces light. It’s sort of cool.

It’s not perfect, but it is possible to make your own glowstick.

Elevator descender

You can’t really see exactly what MacGyver has rigged up—but it’s a type of descender. The basic idea is that when a torque is applied to a ring around a line, it binds up with a frictional force to prevent it from sliding.

Here is a diagram I created that might help explain how this would work.

These two loops around the elevator cable could be just about anything. One idea was to use some padlocks—but as long as it’s stiff and goes around the cable, that’s fine.

So, here’s how it works.

• If MacGyver puts his weight on the bottom element, it will provide a torque and bind up against the cable.
• He can then move the top element down.
• Next, he hang from the top element so it binds and then he can move the bottom thing.
• Repeat

DIY Tesla coil

A Tesla coil is essentially a device to create a very large electric potential difference (many would say high voltage). The most common method is to use a series of transformers—a way to convert AC signals to higher voltage (yes, I said it).

For MacGyver’s hack, he uses the ballast from a bunch of fluorescent lights. A fluorescent light starts with a tube of gas. Electrons are accelerated in this tube and interact with the gas molecules to produce light. This light is in the ultraviolet range, so you really can’t see it. But there is a coating on the inside of the tube that absorbs the UV and produces white light—this is the “fluorescence” part of a fluorescent light.

But the key is high voltage. Yes, the electrons need to be accelerated over an electric potential difference that is greater than the usual 120 volts from your AC outlet. That’s where the ballast comes into play. This takes the 120 volts from your household circuit and ramps it up to something like 500 volts.

What about a Tesla coil? If you want to get cool (and giant) sparks, you will need about 5,000-30,000 volts. So, would 10 ballasts do the trick? Probably not—the voltages just don’t add up that way. But still, it’s based on a real thing.

Faraday cage

You can’t “block” electric fields that are associated with things like sparks and electromagnetic waves—but you can make more electric fields that produce a zero electric field. That’s what a Faraday cage does. It creates more electric fields that cancel an external electric field.

Here is a very basic example. Suppose I have a constant electric field and I want to “block” this. If I put a piece of metal around me, the external electric field will move charges in the metal and these charges will create more electric fields. When you add all the fields up, you get a zero field—it’s just like the field is canceled.

The cool part about a Faraday cage is that it doesn’t even have to be solid metal. You can still have holes in it and it will cancel electric fields. Here is an example of a Faraday cage with a radio and some aluminum foil.