Science, Maths & Technology

# Invisible challenge

Updated Monday, 12th June 2006

Have you ever wanted to make something invisible? Well now's your chance - see if you can make something disappear with the invisibility challenge.

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Adam discovers - painfully - how useful it would be to be invisible … by going paint-balling.

We can be seen because ‘photons’ (little particles of light) are reflected off us and back into someone else’s eye. Camouflage helps to conceal us by allowing us to blend into the background. But camouflage isn’t the same as being invisible for two reasons; first, the background has to match the camouflage, and second, you have to stay absolutely still because any movement will reveal your outline.

Some animals have mastered the art of camouflage. Cuttlefish and octopuses change colour to match their background using special cells called ‘chromatophores’. Octopuses can also change their outline, from smooth to rough, depending on whether they are on rock or coral.

To make yourself truly invisible you’d have to have transparent flesh like Glass Catfish and light would have to pass through you at the same speed as it passes through air.

We can’t give you any instructions on how to make yourself invisible. But here’s a fun experiment with camouflage to see how an animal disappears in the jungle.

Stuff you need

• Design provided below covered in dots
• Colour printer
• Scissors
• Sheet of acetate
• Glue

What to do

1. Just print off two copies of the background provided, then cut out an animal shape from one of them (go on be creative!).

2. Stick your animal face down onto a sheet of acetate. Turn it over and place on top of the background sheet. The animal should blend into the background.

3. Now try moving the acetate around and see how easy it is to spot your beast - until you stop moving it, and it disappears again!