These wavelengths are not present in fire or other natural light sources that would have been used at night. (wellnessmama.com)
Whilst in most situations it is impossible to rely solely on natural light sources, there are alternative solutions available. (qaeducation.co.uk)
Most people describe natural light sources like fire as being soothing and promoting sleep, largely because of their lack of blue light (and obvious natural beauty). (wellnessmama.com)