On a dark, moonless night, light levels can be thousands of times lower than during the day. But while we sleep in our beds, most living things begin the active phase of the day. So how do they manage to navigate in total darkness?
As an example, take nocturnal insects - their visual organs are often no larger than a matchstick head, but they navigate perfectly in dim light, deftly avoiding obstacles and detecting even faint movements around them.
Imagine that you find yourself at night in a rainforest, with no moonlight or starlight penetrating beneath the trees. It would seem to you that there is no source of light around at all. But this will only be true for our imperfect visual apparatus - in fact, the space around will be full of single photons. For the human eye their number will be obviously not enough to get at least a dim picture of the world around us.
However, the vision organs of nocturnal insects and animals are much more sensitive. For example, the vision organs of the tropical night bee Megalopta genalis absorb only a few photons, but this is enough to navigate in a tangled and dense tropical forest even when light levels are at extremely low levels. The European nocturnal butterfly, Deilephia elpenor, of the ladybird family, behaves in a similar way. This would not have been possible without certain tricks on the part of the insect.
Using the example of the reveller, scientists studied the visual centers of the insect's brain and found that due to the specific work of neurons, the moth is able to put together a single picture of single photons that it picked up at different points in space and time. As more and more photons are captured, the picture of the world in the head of Deilephia elphenor becomes brighter - it can be compared to the long exposure time of the camera when taking a photo.
True, it is not possible to achieve a high definition of the image, but the insect can form an idea of the world around him and even see it in color!
Other nocturnal insects have this ability, which is called "neural summation". Of course, the final image will be far from ideal - for example, fast-moving objects will not be recorded, but this way of visualizing the world shows how complex and ingenious the visual center of even small creatures is.