As aquarium keeping has developed into a more mainstream hobby over the years, a lot of time, expense and effort has been put into the research and development of aquarium lighting systems that can recreate daylight in order to stimulate a healthy marine environment. In contrast, however, the field of moonlight has been kept ‘in the dark’, receiving relatively little research, and even less explanation. This has lead to the rise of a number of misconceptions becoming widespread throughout fish keeping community, not least of which being the notion that moonlight is just blue light.
It’s All about Perspective
As is the common belief amongst hobby aquarium keepers, the light given off by the moon is most definitely blue which seems accurate, right? Wrong, actually, does anyone hear the faint buzz of the ‘Common Misconception’ alert from QI? Moonlight actually contains the full spectrum of colours, and has even been found to be comprised of more red and orange light than daylight (we realise we’ve typed the word light quite a few times, and it might be getting confusing). Studies have actually shown that moonlight is comprised in the large part of red light, but also contains a variety of colours from the full spectrum, including green, yellow and violet.
You Got the Blues
So why is that we only see blue light? To answer this, you first need to understand that all light exists on a spectrum that we can only see a small portion of. The light that we see coming from the moon is, like all light, the same colour as the thing it’s being reflected off (in the moon’s case, a grey-ish, off-white colour), but owing to something called the Purkinje effect, we only perceive a small portion of it. To elaborate, the Purkinje effect explains the human eye’s natural tendency to perceive things better around the blue end of the light spectrum. Hence, even though the moon actually reflects white light (which is comprised of red, orange and white light etc.), we perceive it as a navy blue hue.
So there we have it, unfortunately not that much about aquarium lighting systems here, but what we hope was a helpful explanation of a common misconception that we see come up a lot of the time. Should you need any useful advice, or just want to pick our brains a bit further, we’re always happy to kill some time over at our live chat function.