Physics Explained Part I: Mechanics

I’m probably going to change some of these videos (especially the earlier ones), but here is my list of videos for Intro Physics I.

Chapter 1: Kinematics

Chapter 2: Forces and Motion in 1D

Chapter 3: Motion in 2D and 3D

Chapter 4: Calculated Forces

Chapter 5: Constraint Forces

Chapter 6: Circular Motion

Chapter 7: Work-Energy

Chapter 8: Collisions

Chapter 9: Torque and Equilibrium

Chapter 10: Angular Momentum

MacGyver Season 4 Science

Here are all of my notes for Season 4:

MacGyver Season 4 Episode 13 Science Notes: Save + The + Dam + World

Is this the best episode title? Probably.

Sheva Power

So, there’s this machine that Tesla made (just in case you weren’t following the previous episodes) called Sheva. It was used as a type of directed EMP device to destroy electronic stuff.

Aunt Gwendolyn says that it’s not just a weapon. It’s also a renewable power source. OK. Let’s just assume that Tesla figured out something that no one else figured out. I’m fine with that.

However, you can’t get energy for free—like, never. If you want to produce some electrical energy output, SOMETHING has to decrease in energy. It is the way. Even with a nuclear power plant, there is a change in mass energy (from the E = mc^2 thing).

What about renewable energy? Really, this just means the original source of the energy is something we don’t care about. If you use solar panels on your house, you can get electrical energy. This comes from the Sun—which is basically a giant nuclear fusion power plant. But who cares if the Sun decreases in mass? It’s really not our problem. So, solar panels aren’t giving you “free energy”.

OK, so what about Sheva? No one knows. That’s why this is such a great weapon/tool. Maybe it gets energy from the interaction between the Earth and Sun’s magnetic fields. Perhaps it has something to do with other dimensions. Clearly, it’s not just hand-crank powered. That wouldn’t give enough energy for an EMP and it wouldn’t be renewable. The mystery is why it’s cool.

Nuclear Critical Mass

There’s a bunch of stuff here, so let’s start with the most basic part. What is nuclear fission?

OK. Suppose you have a big atom. Let’s say it’s Uranium-233 (this means it has 92 protons and 141 neutrons in the nucleus). If you throw a neutron at this atom, it becomes unstable and (usually) breaks into Xenon-137, Strontium-94 and 3 neutrons. The mass of all this stuff is less than the mass of the U-233 with the lost mass being converted to energy.

If you have just one uranium atom, you just get a small amount of energy. But if you have a whole bunch of uranium atoms, you can get a chain reaction from those neutrons. How many atoms you need for a chain reaction is the critical mass.

Sheet Metal to Protect from Missile.

A missile is inbound to hit the warehouse with MacGyver and Riley. MacGyver takes a piece of sheet metal to cover both of them inside a small inclosure. The missile hits. Boom. Explosion. Fire.

Would this work? There are three things you have to worry about with an explosion:

  • Projectile debris. Stuff gets flung all over the place. If this stuff hits you, it’s like getting shot with a bullet (or worse).
  • Pressure wave. The explosion creates a change in air pressure that pushes outward. This pressure wave can seriously destroy the insides of humans.
  • Fire. Sometimes, there is also fire.

The sheet metal and the enclosure would surely give some protection from the projectile debris. It might also protect from fire. It wouldn’t do too much against the pressure wave. However, for an unconfined explosion the pressure wave expands in all directions and decreases in damage as it gets farther away. If they aren’t too close, they might be able to survive.

Destroying a Nuclear Bomb with a Conventional Explosion

So, there’s a nuclear device. It’s going to explode and destroy a dam. The dam will flood a volcano. The volcano explodes and covers much of the Earth’s atmosphere with volcanic ash to make things bad. That means MacGyver needs to stop the nuclear explosion.

Really, you don’t need some super secret knowledge to make a nuclear bomb. Pretty much everyone knows how to do it. However, it’s still difficult. You need the following two things for a nuclear weapon:

  • Nuclear material.
  • Precise engineering.

The key is to get a nuclear chain reaction started. The reaction is almost always (but not always) initiated with conventional explosives. It has to be JUST right to get the thing to go nuclear.

If you put a conventional explosive near a nuclear bomb, it can disrupt the very delicate start of the chain reaction. Of course, it’s still a bomb—so, that’s not good. Also, much of the stuff in the nuclear bomb is radioactive and you will have just spread that all around the place, that’s also bad. But it’s better than a nuclear device.

MacGyver Season 4 Episode 12 Science Notes: Loyalty + Family + Rouge + Hellfire

DIY Flail

This is a classic MacGyverism. Mac takes off his jacket and picks up a rock. Then he puts the rock into the jacket such that he can swing the rock around. Yup, it’s a type of flail.

Gas Mask and Stuff

You don’t see all the details of the build, but MacGyver needs to gear up so that he can do some stuff (I don’t want to say exactly what he’s doing). Here are some of the things he builds.

  • LED light with a lens. If you focus the LED light, you can get very high intensity light and temporarily blind people.
  • Some type of balloon with knock out gas. I’m not going to say what he put in the balloons—for obvious reasons.
  • Gas mask with a small scuba tank—it’s actually a “spare air” for scuba emergencies. But this means that his mask will have its own independent air supply.

Fire Suppression System

How do you put out a fire? Well, you need to take away just one of three things (usually):

  • Fuel
  • Air
  • Heat

Most fires are an interaction between carbon and oxygen to produce energy (and other stuff). If you remove the oxygen, you stop the fire. That’s how this fire suppression system works. In the case of the one in the Phoenix building, it uses nitrogen gas to flush out the oxygen.

I suppose now is the appropriate time to point out that normal air is mostly nitrogen anyway—it’s about 79 percent nitrogen and 21 percent oxygen (yes, there’s other stuff in there too). Normally, we breath in the nitrogen and just exhale it. However, if there isn’t enough oxygen in your breath, you pass out. Oh, if there’s too much oxygen—that’s bad too. Humans can breath pure oxygen at atmospheric pressure for quite a while with no negative effects. However, at higher pressures (like with scuba diving) pure oxygen is a bad idea.

The most common method for removing oxygen from a fire is to use halon gas. Halon is denser than air, so it will fall to the floor and push the air (with the oxygen) up away from the fire. But nitrogen should work too.

Chain Defense

MacGyver uses a chain and drops it on the road. The vehicle rolls over it and the chain gets wrapped up in the axle. Seems at least plausible.

Electromagnetic Pulse

The idea of an EMP is to produce a very high intensity burst of electromagnetic waves. An electromagnetic wave consists of oscillating electric and magnetic fields—like a radio signal or visible light. For the EMP, the intensity is so high that the electric field component can cause sparks and shorts in electronic circuits.

EMP devices are real—but they require very high bursts of energy. For the Tesla Sheva weapon, it’s not completely clear how it works. But we don’t have to know everything. That’s what makes it a fictional show (and more fun that way).

MacGyver Season 4 Episode 11 Science Notes: Psy-Op + Cell + Merchant + Bird

DIY Stethescope

MacGyver takes a bucket and places it up against the wall in order to get a better way to hear what’s going on. This is essentially the same trick as holding up a glass to the wall to hear what’s on the other side.

Sound is an oscillation—usually in the air. When you talk, your vocal cords push on the air to make compression waves. These air compression waves travel out such that your ear can detect them—that’s hearing.

But sound can also travel through solids. Actually, sound travels better through solids than through gases—mostly because the atoms in solids are closer together than atoms in gases. And that is exactly what’s going on here. The sound from the humans travels through the air and hits the wall. This vibrates the wall and the wall vibrates the bucket. Finally, MacGyver can hear the bucket.

Artificial Sunlight

In order to convince the Merchant that he’s in a prison, they need to make artificial light. So, what’s the difference between sunlight and light from an LED? Well, it’s possible to produce a light source with similar colors as sunlight, but how do you reproduce the atmosphere?

When sunlight passes through the atmosphere, the violet and blue wavelengths tend to scatter off the air. This is called Rayleigh scattering. You don’t need to remember that term, but it IS going to be on the test at the end of the semester. Oh, this Rayleigh scattering is why the sky looks blue and the sun looks more red-ish when it’s closer to the horizon.

Well, guess what? There is an idea for artificial sunlight. Instead of passing light through the atmosphere, this system uses nanoparticles. Check it out.

Lock pick gun

The basic idea of lock picking is to push the lock pins in the lock cylinder upwards so that they get stuck. Since all the pins have different lengths, the normal way to open the lock is to use a specially shaped metal object that pushes each pin the proper amount. We call this metal object a “key”.

Here is a nice video showing how this works.

But what about a lock pick gun? It’s just like using a rake to go over the pins and push them up, but it does so very quickly with a quick hit. This can push all the pins while twisting the cylinder in hopes of getting them all up at the same time.

For this hack, MacGyver uses the gas cylinder from a taser to power the pick. Seems like it could work.

Grenade protection

Oh! It’s a grenade! MacGyver uses a kevlar vest and a trash can to cover it up. There are two bad things that come from grenades. The first is explosive debris. When it blows up, it sends tiny fragments everywhere—these fragments are like bullets. Bullets are bad. The kevlar vest and the trash can should do a nice job stopping these.

The other bad grenade thing is the pressure wave. The explosion pushes the air into a high pressure wave. When this wave passes over people, bad things happen. The trash can might cut this pressure wave down a bit—but what would really help is distance. The farther you get from the explosion, the greater the decrease in pressure.

MacGyver Season 4 Episode 10 Science Notes: Tesla + Bell + Edison + Mac

I think there is a ton of great history with Tesla, Bell and Edison. I know some stuff, but not enough to really go all into the details. Really, I’m just letting myself know so I will look into this later.

Lightbulb Bomb

Not a Mac-hack since this was from Tesla, and not MacGyver. It’s not exactly clear what he does—but in the end he ends up with a type of flash bang. Really, he could put something explosive inside the glass but he would need some type of ignition on impact. The most likely choice would to use something that requires air. It’s possible he could put gasoline in the bulb along with the hot filament. It might not ignite without the proper amount of oxygen. Then when it hits the ground—flash bang.

Carbon Scrubber

MacGyver is clearly bothered about all the apocalypse stuff—climate change included. So, the solution is to fix the climate. Of course the problem is that humans burn fossil fuels to get some of our energy. These fossil fuels produces a chemical reaction with the oxygen in the air to produce energy—with carbon dioxide as a byproduct. Oh, but guess what—carbon dioxide is a greenhouse gas. This means that it when the sun shines on the Earth, it warms up and reradiates infrared radiation. The CO2 blocks this infrared light and warms up the atmosphere even more. See. I just explained global warming in one paragraph.

After MANY years of burning fossil fuels, humans (yes, that’s us) have increased the concentration of CO2 from 300 ppm (parts per million) to 400 ppm. What is a ppm? Suppose you were able to count 1 million molecules of air (which is about 79 percent nitrogen (N2)). Of these million molecules, 400 would be carbon dioxide. That doesn’t seem like much, but it’s enough to increase the temperature of the atmosphere. This temperature increase can actually produce EVEN more CO2—so it’s a big deal.

MacGyver’s plan is to design a cheap and low power device that removes CO2 from the atmosphere. Most of the known methods for carbon dioxide removal revolve around a chemical process. You pass air (with the CO2) through some type of system with a chemical inside. The carbon dioxide reacts with the chemical so that it’s no longer in the air. The next step is to get the carbon dioxide out of the chemical so that it can be reused. Then you have to store the CO2 somehow (maybe underground).

This is a pretty tough process to be of large enough magnitude to make a difference with the atmosphere. Of course there is another way to get carbon dioxide out of the air—plants. Things like trees. Trees use the carbon dioxide from the air and pull out the carbon to make more tree stuff. They then release the oxygen so that we can use it to breath. It’s a nice system.

Tesla Coil

The Tesla coil is a device to produce extremely high voltages—and at high voltages you can get those really cool sparks.

The basic idea is to start with an alternating electrical current (AC). This goes through a coil of wire to produce a changing magnetic field. Another coil is in the presence of this changing magnetic field such that it induces a voltage. With a proper choice of coils and tuning capacitors, you can start with a low voltage and produce a high voltage. That’s the Tesla coil.

Oh, in this case MacGyver fixes a broken capacitor to get it to work. They then use that to shock a bunch of people. Although these things can shoot out huge sparks, they don’t usually have very high currents. It’s possible to make a dangerous Tesla coil, it really just depends on the design and the output current.

Camera Obscura

This is a real thing—and it’s awesome. I need to make a video to show you how to build one of these. I will indeed do that soon.

The word “camera obscura” literally means “dark room”. Yes, a camera was originally a room. The whole thing is based on the light from a pinhole—a tiny hole.

Suppose I have an object with light reflecting off it from the Sun. Maybe it’s a red ball. Normally, this light would reflect off the ball and then enter your eye so that you could “see” it. But what happens if this light passes through a tiny hole instead? Actually, I’m going to change the object to a large arrow (so that you distinguish the top from the bottom). So, let’s say that there is the giant arrow, a pinhole and then a screen. It might look like this.

Yes, you get an upside down image on a screen from that tiny pinhole. But since the hole is so small, the image is very dim (not much light can get through the hole). The only way to see that image is to make sure the rest of the room is dark—super dark. But there you have it, a dark room—a camera obscura.

Update: I made a pinhole camera for you.

Wine bottle trick

How do you remove a cork from a wine bottle without a cork screw? This is like a classic party question. For MacGyver, he uses fire. By wrapping the bottle with a cloth and then lighting the cloth on fire, the air under the cork increases in temperature. With an increase in temperature, the pressure of the air increases and pushes the cork out.

I think this is real.

But it’s probably not the best way to get a cork out. Also, it doesn’t matter if this would really work or not since it’s just in MacGyver’s head.

Flammable Iron

Is iron flammable? First, I have to say something about the word “flammable”. There are two word: flammable and inflammable. Both words mean the same thing. The original word was “inflammable”—it means that something is able to be inflamed. Of course many people confused the meaning of this word to think it says “can not be flamed”. So, people now use “flammable” to avoid confusion.

But is iron inflammable (see what I did there)? Yes, sort of. If you get the iron started, there will be a chemical reaction between the iron and oxygen that produces energy—this is pretty much the definition of burning. However, if you take an iron nail it won’t work. The interaction with the air only takes place on the surface of the nail—but the whole nail would have to heat up. If you have a very tiny piece of iron, then the ratio of surface area to volume is much larger such that you can get a noticeable reaction.

Faraday and Generators

Faraday’s Law basically says the following: If you have a changing magnetic field, it creates an electric field. An electric field inside of an electrical conductor—like a copper wire, will produce an electric current.

A hand crank generator takes a magnet and spins it near a coil of wire (or it spins the wire near the magnet—it doesn’t matter). This produces an electrical current. This EXACT same process is used in just about every kind of electrical power plant. The only difference between a nuclear power plant and a wind turbine is the thing that turns the turbine.

What about this Tesla Weapon?

Can you shoot out lightning from a weapon? Well, it’s technically possible but highly unlikely. Normally you would need TWO points to create an electrical arc—one at a high potential and one at low (or ground). So, for the Tesla weapon, it’s possible you could make a big spark to something that is electrically connected to the ground, but not just out into the air.

What about the metal in the bad guy’s kevlar vests? This device looks like it’s mostly high voltage and low current. You need high electrical current to make a magnetic field—even then, it would be pretty tough to interact with some objects (you would need super high current).

OK, it is possible that the vests would have some metal plating in them. But kevlar is basically a type of plastic.

Physics Explained: Video Update

I don’t know if you have been paying attention, but I started a second youtube channel. My idea was to split my videos. Right now, I have MacGyver stuff and science demos on my “Rhett Allain” channel—but I will move all the physics calculations to a new channel. Yes, the new channel is called Physics Explained.

Basically, Physics Explained is going to start off as the content portion of an algebra-based physics course. Actually, I will use these videos this summer during my “remote learning” physics course. You can think of this as a video version of a textbook that I would write.

Right now, I have enough for the first semester of physics. I will probably add more, but it’s good enough. Also, I changed my channel name—that means some of the older videos say “Just Enough Physics”. I’ll probably go back and redo these.

If you want to go through the first semester, here is “chapter 1” as a playlist.

Here are some of my favorite videos from that group of content.

Yes, I like to include numerical calculations with python—it’s what I do.

Now, I have started to work on the second semester of physics—you know, electric fields and magnetic fields and stuff.

My goal is to get up to 1000 subscribers—if you are interested, just hit that subscribe button.

MacGyver Season 4 Episode 9 Science Notes: Code + Artemis + Nuclear + N3mesis

Blow Up a Printer

There was this article about remotely making some printers catch on fire. The company says there is a chance for remote hacking, but they can’t catch on fire. Still, it seems at least plausible. Oh – this obviously isn’t a MacGyver-hack.

Viewing the Power Outage

I just want to point out the scene where they are looking down on the city when the power goes out. All the lights go out except for the streets. Actually, street lights go out also. However, the cars on the road still have headlights. These don’t go out. That’s why you can see the roads.

Nuclear Power Plants and Control Rods

I’m going to give the shortest explanation of nuclear power plants.

So, it sort of starts with water. If you heat up water, you can turn it into steam. This steam can then be used to turn a turbine to generate electricity. This is essentially the same kind of turbine used in a wind generator. This is also the same turbine in a coal burning power plant.

The only difference between nuclear power and fossil fuel power is the method to make steam. Instead of burning fossil fuels, the nuclear power plant uses a nuclear reaction—thus the “nuclear” part of the name.

Here’s the basic idea of a nuclear reaction. Suppose you take some heavy element and break it into pieces. It turns out that the mass of all the pieces is less than the mass of the original element. This lost mass is a form of energy. Yes, you’ve seen this:

E = mc^2

Where c is the speed of light. That’s the energy you get from mass. That’s how a nuclear reactor works.

But wait! What about control rods? Well, a nuclear reaction doesn’t just produce energy—it also creates neutrons. These neutrons hit other elements and cause MORE nuclear reactions. The idea of the control rod is to absorb these neutrons and slow down the reaction. See, that wasn’t so complicated.

Finally, yes. A nuclear generator IS like a high tech tea kettle. That’s right.

Water Ski Jet Pump

The water pumps to the nuclear reactor are shut down. It’s going to overheat. Oh, what about a jet ski? It’s basically a water pump without the hoses.

If you want to use this as a pump, you would probably have to “prime the pump” by adding water to the hoses. Inside the jet ski there is a type of cork screw propeller. If it’s just spinning in the air, nothing would happen (well it would push the air). But if there is water in there, when the water moves it essentially pulls the water behind it along with it (due to a pressure differential).

But this should work.

Hydrogen Gas

Water is made from two hydrogen and one oxygen atoms (H2O). So, how do you get hydrogen by itself? The most common method is with electrolysis—basically just passing an electrical current through water. Wait! You can actually do this yourself with a 9 volt battery.

The other way to make hydrogen is to get the water hot. I mean REALLY hot. No, not boiling hot. More than that. Oh, I should point out that when water boils, that’s not bubbles of hydrogen and oxygen, it’s bubbles of water vapor (water as a gas).

Heating water to split it into hydrogen and oxygen is called thermal decomposition. This happens at a temperature fo 2200 Celsius. Yeah, that’s hot.

Is hydrogen gas explosive? Not by itself. However, when it recombines with oxygen to create water it releases TONS of energy. That’s the problem—but you have to have oxygen. What if you flush all the oxygen out? Then you wouldn’t have an explosion.

MacGyver Season 4 Episode 8 Science Notes: Father + Son + Father + Matriarch

Newton’s Third Law

It’s not a hack, but I wanted to go over this quote from MacGyver:

“Every action has an equal and opposite reaction.”

Clearly, he isn’t just talking about physics and stuff—so let me give a very brief explanation.

This originally comes from Issac Newton and his “three laws of motion”. What he (Newton) was trying to say was that forces come in pair—forces are an interaction between two objects. So, if object A pushes on object B with some force, then object B pushes on A with the same force but in the opposite direction. That’s what Newton meant to say—but it’s tough when no one has nailed down the operational definition of things like “force”.

However, the most common version of this “Law” uses the action and reaction term. Of course forces come in pair always—it doesn’t matter if the objects are moving or stationary. So, the “action” and “reaction” don’t always make sense. This is why I prefer the force law stated as the following:

Forces come in pairs. For every force, there is an equal and opposite force.

If you have to write it in that form—that’s the best way. But what about action and reaction? This statement is still true in many cases. Let me give you an example.

Take a balloon and fill it with air. Now let the air out and remove your hands from the balloon. What happens? The air inside the balloon is at a higher pressure than outside the balloon. This means the stretched balloon rubber PUSHES the air out. Oh, but forces come in pairs—this means that the air also pushes on the balloon. Since a force CHANGES the momentum of an object (where momentum is mass multiplied by velocity), the balloon speeds up one way (action) and the air speeds up the other way (reaction).

Yes, that is EXACTLY how a rocket works—except it uses a chemical reaction to push gas out instead of stretched rubber.

I spent too much time on this one quote. I can’t help myself.

Disabling a Contact Mine

These explosive bombs are magnetically attached to the vehicle. Obviously, you can’t just pull them off—that’s how they EXPLODE. So, MacGyver’s idea is to destroy their electronic components with the car’s battery. If he can run electrical current through the mine, then maybe they will be disabled.

Fortunately, the mine is on a metal hood—assuming the paint doesn’t form too thick of an insulating layer then he can use the car’s ground as one of the contact points. Then he would just need to run a wire from the positive terminal of the car’s battery (he could get the positive from the 12V outlet inside the car) to the mine.

Yes. This process might also kill the truck—especially if current goes through the ECU (basically the computer that runs the engine).

DIY Electromagnet

Electrical current creates a magnetic field. If you wrap a wire into a coil with multiple loops, each loop will create a magnetic field that adds to the other magnetic fields from coils. So, more loops means a great magnetic field.

If you put a ferromagnetic core in the loop (like iron or most forms of steel), then these electromagnetic loops will also magnetize the coil and make the whole thing even stronger.

This is exactly what MacGyver does. He uses his Swiss Army Knife as a ferromagnetic coil and a battery from a flashlight as the power source. Then he uses this to pull out a bullet fragment from a wound. Now, he has to get lucky to use this. Most bullets are made of non-ferromagnetic materials (like lead or copper). But if it has even a little bit of steel (or some other materials), there’s a chance he can pull it out with the magnet.

Oh, one last note. The wire can’t be plain copper wire. It has to have some type of electrical insulation on the outside. This insulation forces the current to move around in a loop instead of taking a short cut from the start to finish. Some wire has a rubber coating to insulate it—but in this case, it’s called “magnet wire”. It has a thin enamel coating so that you can wrap it into a coil.

Dobsonian Telescope

It’s not really a hack, but it is important for the plot. There’s a telescope that MacGyver is going to use later. It’s a Dobsonian mount.

The “Dobsonian” part really refers to the way the telescope is aimed and not so much about the optics. I’m pretty sure every Dobsonian telescope uses a Newtonian optic design. It uses a large focusing mirror at the base of the telescope. Here is a very basic design.

The nice thing about this design is that it’s actually quite simple to build. The only complicated part is the parabolic mirror (which you could also make yourself—but it would take some bit of time). Oh, I left off the walls of the telescope above because you don’t actually need them.

But what about the mount? The Dobsonian is basically just two swivel points. The base of the mount turns and then the telescope moves up and down. Super simple. But it’s not the best design for serious astronomy. The problem is that the Earth rotates. If you were to watch the stars in the sky over the course of a night, they would move in a slow circle about the Earth’s rotational axis. Sure, it’s takes 24 hours (about) for the stars to complete this circle—but they are indeed moving.

If you want to take a time exposure picture of a star (like for 10 minutes or so), then that star is going to move and leave a streak on the image. Actually, someone needs to remind me to take a “star trail” picture sometime. So, the Dobsonian mount has to move both rotation points in order to compensate for this star motion. It’s tough.

The other telescope mount design is called an equatorial mount. In this case, one of the rotation axes is aligned with the Earth’s rotation. That means that you can just slowly turn this one axis and a telescope will remain pointed at a particular star. This has nothing to do with MacGyver—but I just thought I would mention it.

Super Bright Moon

MacGyver needs a distraction. What about the telescope? So, here’s what he does: he aims the telescope at the moon and then lets the image project onto a baddie. The bright light is just the distraction he needs.

Here’s where a big telescope becomes useful. The diameter of the mirror (or lens if it’s a refracting telescope) is related to the light gathering power. All of the light that hits that large mirror is focused up to the eyepiece. So, even very dim lights can be detected. Yes, even very dark things like distant galaxies or comets (both of which can not always been seen by the naked eye) can be detected with a large telescope.

Actually, if you want to get into amateur astronomy you should start off with a nice pair of binoculars. They are much easier to set up than a telescope (because you just grab them out of the case and you are ready to go). Also, with large lenses they can really let you see some stuff that’s invisible to the naked eye. It’s not about the magnification, it’s about the light gathering.

Oh, but a full moon IS indeed super bright. You really can’t look at it with a large telescope unless you have some type of filter. Also, don’t look at the sun with a telescope. That is a super bad idea.

MacGyver Season 4 Episode 7 Science Notes: Mac + Desi + Riley + Aubrey

Honest commentary. I figured this would just be a “filler” episode with just a little side action. NO. This episode was great. Now for some science.

Bra Wire—Nickel Titanium

MacGyver uses Desi’s bra underwire to short out a fuse box. That’s cool and everything, but what’s really great is the nickel titanium wire—also known as memory wire. Here, check this out.

Yes, some bra’s have this kind of wire (also called nitinol) for the underwire.

DIY Periscope

MacGyver needs to find out what’s going on in another room by looking through an air vent. He uses a bathroom rail to mount two mirrors (oh, with gum as glue) to build a periscope.

Here’s how to build one yourself.

Lithium Battery Fire Bomb

OK, it’s not really a bomb it just starts a fire. MacGyver needs a distraction. So, he punctures a lithium-ion battery and then covers it with chocolate. When the chocolate melts, the battery is exposed to air. This is where the bad stuff happens. Don’t puncture your phone battery. Check this out.

Ping Pong Ball Flash Bang

It’s a ping pong ball with butane (from a lighter)—it would probably go boom. Don’t do this.

Cooking Spray Fire

Yup. Many cooking sprays are inflammable (which means it can catch on fire). Oh, you think it should be flammable if it can catch on fire? Surprise, those two words mean the same thing.

On top of that, when you get really small particles of stuff the surface area to volume ratio is huge. That means that there is a lot of the material that can interact with oxygen in the air—this makes it burn.

In fact, you can even make flour “explode”.