# MacGyver Season 3 Episode 13 Science Notes: Wilderness + Training + Survival

There is no funny intro for this post. Oh wait, this is an intro.

Rock and steel to make a spark.

OK, this isn’t actually a MacGyver hack in this episode but I’ve talked about it before. Here is a video.

Other fire stuff

Are there certain plants that ignite more readily than others? Yes. Here is a nice article from Field and Stream that goes over the basics.

Again, not a hack—but cotton is terrible when wet (so is denim jeans). When wet stuff is next to your body, the water evaporates. In this process the liquid water turns into a gas water (water vapor). The phase transition requires energy. Guess where the energy comes from? Yup, it comes from the human. This makes the human colder. Here is my more detailed explanation.

What about wool and other materials? The key to these better fabrics is that they “wick”—they pull the water away from the body. Here is a nice post on that.

Zipper for ice traction

MacGyver takes the tent zippers and uses them on people’s shoes for added traction on ice. It’s sort of like mini-spikes on your shoes. Classic.

How to make drinkable water

MacGyver uses a tree branch to act as a water filter. This seems to be real (from MIT) so you know it’s got to be good.

Here is a nice video showing how this would work.

Making rope (string)

I’ll admit it—I’ve never really understood how this works. If you take some vine or some other material, it has a certain maximum strength in its tension before it breaks. If you take two of these things together, it doubles the strength. If you take these two things and then twist them—the strength is more than double. What? But it does indeed work (I need to do an experiment sometime to really understand this).

Here is an older video in which I attempted to make rope from a TV guide.

Size and weight of 18 million dollars

This is a classic MacGyver estimation problem. How do you find the size and weight of a bunch of money? Why does it even matter? Well, one big thing is to find the density of the money. If the density is less than the density of water, then the crate of money would float and then be swept away in a flash flood.

Yes, you don’t need the weight and size—but just the density. However, if you want to estimate how long the crate was floating you DO need the size. Bigger crates will “hit the bottom” before smaller crates.

If you want to look at more stuff about the density of money, here is an older post in which I find out how far 1 trillion dollars would stack. Would it make it to the moon?

Surveying tools

How do you find the slope of the ground? This is where you need surveying tools. Here’s how it works. Get a scope (from a rifle) and make sure it’s aimed level. There are plenty of ways to level a scope—those little bubble levels work great. Next get a survey stick. Make sure this is also vertical and then measure where the scope points at the stick.

If you know the change in elevation and the distance between the stick and the scope you have the slope.

Float distance calculation

Yeah, this is pretty tough—but that should never stop anyone from trying. How do you estimate the distance a crate will float in a flood? Here are some things to consider (some of these would be tough to estimate).

• How fast was the water flowing?
• How deep did the water get?
• How long did the flood last?

Really, if you know those things you can calculate the speed and time of the floating crate. This would then give you the distance. From that you can find the location on a map.

Drag sled

To move a crate (or an injured MacGyver), it shouldn’t be too hard to make a drag thing—called a travios.

Grab hot coals

Don’t try this at home, but it is indeed possible to grab hot coals. Essentially, you can grab hot stuff if you are really quick. There isn’t enough time to transfer energy to cause a major burn.

It’s just like walking on hot coals. Here is a nice physics post on that.

# MacGyver Season 3 Episode 7 Notes

Computer Recycling

This is unfortunately real.  There are places where all the old computer crap ends up and people try to get the good stuff out of them.  Here is a WIRED story.

I guess a more important issue—why do we throw away so much stuff?  Perhaps it’s just because we live in an era of rapid technology changes.  This means that computers can become outdated fairly fast.  It’s cheaper to just throw stuff away rather than deal with it properly.

Actually, at one point there was a student project that looked into the financial benefit of getting the useful stuff out of old electronic stuff—in particular the gold.  How do you get it out and is it worth the money?  I think the answer is no—you probably won’t make money by mining electronic stuff for gold.

Take apart a hard drive

This isn’t a hack from the show, but I just have to add a comment.  If you have an old hard drive, you should take it apart.  It might not be super easy since many of them have those stupid “security screws”—but still you should go for it.

There are two great things you can get out of a hard drive: awesome magnets and great mirrors.  The magnets are really what the hard drive is all about—using the magnets to make magnetic fields that write magnetic domains.

There isn’t really a mirror inside the hard drive, but in most cases the hard drive platters (the spinny thing that the data is written too) is super smooth.  So smooth that it works as a mirror.  Be careful.  Most of these platters are metal, but I did find one that was glass-like and shattered when I dropped it.  The metal ones make great mirrors though.

Toothbrush lock pick

Let me just say that I have a friend who is a locksmith.  After talking to him, it’s very clear that just about every lock can be picked.  It’s not even that hard.  Really, locks are more of a social contract than actual physical barriers.

If you want to try picking locks, there are plenty of guides online (and there is the classic MIT lock picking guide.  There are essentially two parts to lock picking.  First, you need to torque the lock cylinder with a torque wrench.  Second you need to jiggle the lock pins (inside the lock) up so that they get stuck up.  Then you can open the lock.

The toothbrush is just a quick quick to jiggle the pins up to open the lock.  I think I’m going to build one of these—you know, for research purposes.

Exploding toothbrush

Actually, I’m not sure what device is used here—but it looks like an electric toothbrush.  MacGyver takes the toothbrush and connects it to an AC power cord and then jams it in the lock.  It explodes.

Of course, it’s not the toothbrush that explodes, it’s the rechargeable battery.  Yes, these things can explode.  More on this later.

Microwave gun to disable cars

Here is the short version of this hack.  MacGyver is in the back of a dump truck with junk in it.  They are being chased by bad guys in military trucks.  OK, they aren’t bad guys—but they want to stop MacGyver.  Really, they are just doing their jobs, right?

OK, so MacGyver finds an old microwave and takes it apart.  He gets out the magnetron and then plugs it into the truck DC power supply.  This creates directed microwaves that he aims the microwaves at the trucks and they get disabled (with fire).

Is this real? Like most MacGyver hacks (but not all), it’s at least based on something real.  Yes, there are microwave guns that can disable a car – https://www.technologyreview.com/s/409039/stopping-cars-with-radiation/ These microwaves then screw up the electronics in the car.  I think it works by generating electric currents in the computers that melt tiny wires.  Well, it’s real anyway.

What about the microwave gun?  Yes, that is also real—I mean, you have one in your microwave.  Check out this microwave (real) gun from Allen Pan.

That dude is the real MacGyver.

High frequency sounds and younger humans

Some kids are being held captive by some adults.  MacGyver needs to send them a message—but he obviously doesn’t want the bad guys to hear it.  So, he hacks a tape record so that it plays a high frequency message.  Here is the deal: younger humans can detect sounds at much higher frequencies than adults can.  I think it has something to do with the frequency response of the ear-thingy (which probably has a technical name too).

Oh, what about hacking the tape player?  I think that it’s possible to record a message and then play it back at a higher frequency.  Really, all you need to do is speed up the motor that pulls the magnetic tape over the reader head.  I think that would do the trick.

Lithium battery bombs

Here is another hack that is unfortunately true.

https://www.bbc.com/news/technology-37255127

If I understand it correctly, it seems like there is some type of internal short in the battery that causes it to heat up.  When it gets hot, it gets more internal shorts and heats up even faster.  You get some type of runaway reaction and boom.  Bomb.

If you want to make tiny grenade like bombs out of these things, good luck.  It’s pretty tough to make them explode exactly when you want them to.  Oh, don’t do that anyway.