MacGyver Science: SOS + Hazmat + Ultrasound + Frequency + Malihini

Breaking a Padlock With Two Wrenches

You know, locks don’t actually prevent people from entering a place. They are just a deterrent. Given enough time, pretty much any lock can be circumvented. But the question is time. Can you get past a lock quickly? In this case, it’s a padlock. MacGyver grabs two wrenches and uses them to pry the lock apart.

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It’s basically a simple machine that uses torque. When he pulls the ends together, the distance the ends move are greater than the rotating distance of the tiny wrench part at the end. Since the torque is equal on both ends, a long torque arm with a tiny force produces a GIANT force with a tiny torque arm. This is enough to break the lock.

It’s real.

Finding a Hidden Vault Room With Gravity

How do you find something heavy, like a safe-room? MacGyver removes the swinging balls from a Newton’s Cradle (one of those fun swinging ball toys) and rolls them across the floor. When one of the ball deviates from its straight path, that’s an indication that there is something heavy there.

There’s actually two ways this trick could work. The first is with a gravitational force. Gravity is an interaction between any two objects that have mass (so, pretty much everything). However, it’s a super weak force. We notice the gravitational force due to the interaction with the Earth because the Earth is very massive (5.972 x 10²⁴ kg). But you won’t notice the force between you and a person standing near you.

What about the force between a ball and a massive room? It would still be tiny. However, tiny forces CAN make a difference. If you have a small force on a rolling ball, it’s possible the ball could deviate a little bit. But wait! There’s an even better example of tiny forces — the Cavendish Balance. This is a device that measures the gravitational force between two masses. The idea is to use a horizontal rotating rod that can move with very tiny forces. Here is my explanation.

OK, there is a second way this rolling ball trick could work. It’s possible that the safe room bends the floor — even a tiny little bit. With a small bend in the floor, a ball might not roll straight. A curving ball would indicate a bent floor due to the safe room. This method isn’t as much fun since we don’t get to talk about gravity.

DIY Gas Chromatograph

MacGyver wants to use gas chromotagraphy to find out what’s in the air causing people to get sick. A gas chromatograph is a complicated, but useful device in chemistry. The basic idea is to take a sample and separate different chemicals based on their evaporation rates and then use a detector to figure out what chemicals you have.

Here is MacGyver’s version.

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But is it possible to build a DIY version. Yes. Check this out.

Food in a Refrigerator as a Control Group

Suppose the whole illness problem is caused by air borne bacteria. These could also be present on food. But there’s always bacteria in the air — that’s why food gets messed up when you leave it out. However, if you look at the food in a fridge — it could be separated from the rest of the building (because the door is closed). If you find significantly more bacteria on the food OUTSIDE of the fridge, that could indicate some type of extra stuff in the air.

This is the idea behind a control variable in scientific experiments. You can break experimental data into two groups: experimental and control. The experimental group has something extra added to it, but the control group does not. Then you could look for differences in the two groups. That’s whole idea of a control.

Bacteria Stain

You can’t see bacteria — it’s too small. Instead, you need to use a stain to distinguish between different types of bacteria. Here is a homemade stain.

UV Fluorescence

Why is there a UV light in a water filter? Well, ultraviolet light can destroy bacteria and other bad stuff in the water — so, you have a UV light. But what does it do to the bacteria stain? The idea is that when UV light hits some materials, they fluoresce. That means they emit different wavelengths of light. Yes, this is the same thing that happens when some clothes look weird under a black light (a black light is a UV light).

Here’s how that works.

Sonic Weapons

Yes, they are a real thing.

Sonic Weapon Detectors

The idea is to use an ultrasonic transducer to detect the sonic weapon. If you want to know WHERE the source comes from, you can use triangulation. That’s what they are doing here.

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Since sound travels at a finite speed, the sound waves from the source should arrive at the different detectors at different times. Just think about this simple case with just two detectors and a sound wave.

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Since detector 1 (in this diagram) is farther away, it would hear the sound after detector 2. Based on the time difference and the distance between the detectors, you can find the angular direction of the source.

So, why do you need a 3rd detector? If you know the time difference between detectors, there are actually two solutions for the location of the source. There’s the one shown above and then there’s one on the right side of the detectors. Having that third detector eliminates the other solution.

Audio Feedback and Resonance

MacGyver uses the sonic detector and connects it to the alarm speakers in the garage. When the bad guys use their weapon, this creates a feedback loop. Here is a demonstration of real feedback.

But wait! There’s more. Since they are in a closed room, the sound reflects off the walls and interfere with other sound waves to make it even louder. This is exactly what happens with many musical instruments — like a flute. A resonance is created in the closed tube of the instrument.

Physics faculty, science blogger of all things geek. Technical Consultant for CBS MacGyver and MythBusters. Former WIRED blogger.

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