It’s a moonless night. You’ve crossed from Church Point to the Bay, tied up at the wharf and stepped off the boat. The motion sensor illuminates the solar light on the wharf and guides you to the end of the jetty. Then the light is gone and you’re in darkness. You forgot your phone and you don’t have a torch. You’ve trodden this path a hundred times before but suddenly you’re unsure. You could run into something, trip and fall, step in a hole and turn an ankle.
The obvious answer to this problem is street lighting but most people agree that this would change the character of the Bays not to mention the lives of the myriad of nocturnal creatures great and small that need the cover of darkness to hunt and forage. This is their home too so hopefully, that’s out of the question.
But if animals can operate in the dark, why can’t we? Many nocturnal animals such as owls have a structure at the back of each eye called the tapetum lucidum. This is a tissue which reflects light back through the retina which effectively turns the night into day for them. It’s also why their eyes shine in the dark if caught in a flashlight. Others, like wallabies and possums just have extremely large eyes.
wallabies and possums have extremely large eyes to see at night
Humans aren’t built the same way. Our eyes are made up of rods and cones. The cones operate when there’s plenty of light and they provide colours and detail in our vision. When you move into darkness, your eyes automatically swap from using cones to rods. This coincides with your pupils opening up to allow in more light. However, the pupils can only do so much and the crossover from cones to rods doesn’t happen instantaneously. In fact to obtain 80% adaptation you need half an hour or more of absolute darkness.
There are two types of photoreceptor cells in the human eye — rods and cones.
You could try wearing an eyepatch like a pirate – which may sound like a joke but it actually does work – the same way aviators flying at night are advised to close one eye when looking at lights to preserve at least some degree of night vision.
Or you could try this.
- Stop and wait.
- Shut your eyes for 20 seconds and then open them.
- Avoid looking at bright lights in the distance on wharves or houses.
You’ll start to see more detail as the rods send their message to your brain. Stay focussed on the darkness. The longer you do, the better your night vision becomes and you start to realise just how much ambient light there is around you, even from starshine.
The road you take becomes recognisable again as you make out familiar landmarks, the occasional pothole, the edge of the path curving around a bend. And in that moment of quietness in the dark, who knows what shy bush creatures you’ll see on your way home? They certainly won’t be hanging around under street lights.
Article by Pru Colville