# Five Divers

A new Cartesian diver variation that utilizes differences in buoyancy for an awesome twist.

We’ve found an awesome new science activity that uses Cartesian divers. No, it’s not Hook or Squidy, although they are pretty awesome, too. We’re talking about the Five Divers experiment. This project features, you guessed it, five individual Cartesian divers, but they’re all in the same bottle. Give the bottle a squeeze and watch as more divers sink as the pressure increases. Try it for yourself!

## Experiment

### 1

Using the permanent marker, number the pipettes “1” through “5.”

### 2

Screw one hex nut onto each of the pipettes.

### 3

Cut each pipette just below the hex nut.

### 4

Fill a drinking glass with water.

### 5

Squeeze the pipette to draw in or release water until the pipette BARELY floats in the drinking glass. Repeat with the remaining pipettes, trying to keep the amount of water in each pipette as equal as possible.

### 6

Fill the plastic bottle with water up to the rounded portion. Place pipette “1” in the bottle.

### 7

Squeeze 3 drops out of the pipette “2” and place it in the bottle. Squeeze 6 drops out of pipette “3,” 9 drops out of “4,” and 12 drops should be squeezed out of pipette “5.” Put each pipette into the bottle.

### 8

Fill the remainder of the bottle with water and screw the cap on tight.

### 9

Squeeze the bottle and watch the divers sink, one at a time. Release your grip and you’ll see the divers float right back to the top… one at a time!

Note: If the bottle requires a super-strong squeeze to move the divers, there isn’t enough water in the pipettes. Remove the divers from the bottle and increase the water levels in the pipettes so they just barely float.

## How Does It Work

The Cartesian Diver is a classic science experiment that’s hundreds of years old. It’s named for a Frenchman, René Descartes (1596-1650), who made huge contributions in the fields of philosophy, math, and science. The original Cartesian Divers were made out of glass medicine droppers or delicate glass ampules. When you have the water levels adjusted correctly in your new, unbreakable divers, you should see the water in the diver (pipette) rise as you squeeze the bottle. The air trapped in the pipette compresses into a smaller space and the diver’s weight increases. It becomes less buoyant and it sinks. When you release the squeeze, the compressed air expands and forces water out of the diver, allowing it to float to the top of the bottle.

So, why do they sink one by one, and float similarly? It has to do with the drops of water you squeezed out before tossing your divers in the bottle. Keeping in mind how the divers work, each one reaches its buoyancy threshold with a different amount of pressure on the bottle.