Ever been camping and felt really sleepy and time for bed, only to discover its just 8pm?
How about staying up til 2am playing computer games (perhaps later?) because you didn't feel tired.
Do you struggle to get out of bed when the alarm clock rings in the morning?
Hitting the snooze button isn’t always a sign of laziness; sometimes our body clock becomes out of sync with the outside world. Electronic lighting, TVs and computer screens are often pinpointed as the culprits for this desynchronisation.
Light is one of the strongest time cues to tell your body it's daytime. Simply put: light in the morning wakes you up, dark in the evening helps you fall asleep. Although it's not always as simple as that. The type and amount of light matters too.
Our body clocks are most sensitive to blue light. There are specific photoreceptors in the eye, at the back of the retina, that detect light and signal this to the brain . These photoreceptors are particularly sensitive to shortwave lengths, i.e, blue, light.
|Short wavelengths of 420-480nm (blue light) are most efficient at resetting our body clocks.|
The circadian system is important to our biology so other wavelengths of light can still reset our clocks, but they need to be brighter. If you don’t want to stay up all night avoid bright white lights in the evening .
The photoreceptors are not sensitive to short bursts of light, so a single bolt of lightning would not reset your clock; the light needs to hit the retina for several minutes. So a long trip to the bathroom in the middle of the night might trick your clock.
If you want to get a good night’s sleep, in the evening use dim lights with longer wavelengths (reds) of light. A few computer users have found using software like f.lux useful. This is a free software that colours your computer screen in a red hue in the evening and night time. This is good news for those of us who still want to play on the computer in the evenings, without keeping us up all night. It comes on automatically, however it's easy to turn off and on for doing colour sensitive photographic work.
I’ve joined 46 000+ others in “liking” f.lux on facebook. If you do try f.lux, let me know how you get on.
 T. Liesegang, “How the Brain’s Clock Gets Daily Enlightenment,” Science, vol. 295, Jul. 2002, p. 955.
 J.J. Gooley, K. Chamberlain, K. a Smith, S.B.S. Khalsa, S.M.W. Rajaratnam, E. Van Reen, J.M. Zeitzer, C. a Czeisler, and S.W. Lockley, “Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans.,” The Journal of clinical endocrinology and metabolism, vol. 96, Mar. 2011, pp. E463-72.