You'll need
- At least 2 people
- Lots of space – either outside in a yard or a long hallway inside
- 20 m tape measure
- A printout of the grey eggs sheet
What to do
- Ask your friend to hold up the printout of the grey eggs sheet and one end of the tape measure.
- Stand 20 m away with the other end of the tape measure.
- Walk slowly towards the piece of paper. Stop when you can see 2 cracked eggs. Measure the distance between you and the paper.
- Now swap over with your friend and repeat steps 1 to 3.
Questions to ask
- Who had the eagle eyes – you or your friend?
- Was anyone able to pick out the 2 cracked eggs from 18 m away? What about 6 m away?
What's happening
The ability to see whether 2 points are separate from each other is called resolution. This will change as you move closer to or further away from the sheet of paper.
This experiment also tests your contrast sensitivity. Contrast sensitivity is the ability to see the difference between different levels of shading.
Did you know
Humans and birds of prey – like eagles or kestrels – have the sharpest eyesight in the animal world. The American kestrel can tell whether a speck is just 1 dot or 2 dots that are very close together from 18 m away. Most people with good vision can tell apart 2 dots from about 6 m away.
People can also detect changes in contrast, such as grey shapes on a light-grey background.
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