Have you ever played a game of hide-and-seek and wished you could see someone coming without being seen yourself? You can, with the help of an instrument called a periscope.

QUESTION

How can you peer around a corner or look over a wall?

WHAT YOU NEED

• Empty milk carton

• Tape

• Ruler

• Pencil

• 2 small square mirrors Scissors or a box cutter

WHAT TO DO

• Ask a grownup to cut one hole at the top of one side of the carton and a second hole at the bottom of the other side of the carton. The holes should be about the same size.

• Use tape to seal the opening of the carton.

• Turn the carton to a side without holes.

• Draw a square at the same level as the bottom hole. Ask a grownup to help you draw a diagonal line across the square at a 45-degree angle.

• Do the same thing at the level of the top hole. Then turn the carton to the remaining side without holes and draw two more squares and two more lines.

• Ask a grownup to cut a slit along the diagonal lines.

• Insert one mirror into the bottom slit. Insert the other mirror, reflective side down, into the top slit.

• Now find a spot to try out your new periscope. What do you see?

WHAT'S HAPPENING

A periscope is an instrument that allows you to see what's going on around you even though you're hidden. It works with light rays and angles. When light reflects off the surface of the top mirror of the periscope, the light rays change direction and then reflect off of the bottom mirror. This allows you to see what is going on way above you or around a corner.

Your periscope may seem very simple, but this model was used in World War I. Soldiers would put the periscopes on their rifles so that they could duck down in the trenches and stay safe but still see what was going on around them. Submarines also use periscopes, though those models are much more powerful. A submarine sends up its periscope while the vessel is still underwater, thereby allowing it to remain hidden from view while the captain scopes out the surface of the water.

YOUR NOTES

Draw what you see with your periscope.

What a Drag!

Scientists have a name for the force that slows an object down as it moves through the air. It is called “drag.” Use the picture equations to sound out directions for an experiment. Which object shows more drag?

gravity: the force that holds objects close to the Earth's surface. On the Moon there is no gravity, and objects just float around.