Are You Eagle-Eyed?

Humans and birds of prey (such as eagles or kestrels) have the sharpest eyesight in the animal world. The American kestrel can tell from 18 metres away whether a speck is just one dot or two dots that are very close together. Most humans with good vision can distinguish two dots from about 6 metres away. Humans are also able to detect changes in contrast, such as grey shapes on a light grey background.

See if you, your family or friends have the eyesight of an eagle!

What you'll need

• a friend
• a long hallway or yard
• 20 metre long tape measure
• a print out of the grey eggs

What to do

One person needs to hold up the paper with the eggs and one end of the tape measure, while you stand 20 metres away with the other end of the tape measure.

Walk slowly towards the strip of paper and when you can see two cracked eggs, stop in your tracks! Measure the distance between where you stopped and the paper.

Swap over and see how close your friend needs to be before they can see the cracked eggs.

How'd it go?

Was anyone able to pick the two cracked eggs from 18 metres away? What about 6 metres away? The ability to tell two dots apart is called resolution. This experiment also tests your contrast sensitivity.

What's next?

One of the exhibits in Measure Island, called Monkeys in the Mist, looks at another type of vision measurement called contrast sensitivity. When you visit, see if you can spot the exhibit from 20 metres away! And to get some practice before your visit, try this online version of the exhibit.