Olbers’ Paradox

It states

The apparent paradox that if stars were distributed uniformly throughout an infinite universe, the sky would be as bright at night as in the daytime, owing to the fact that whilst the apparent brightness of individual stars decreases with the square of the distance, the number of stars increases in the same proportion.

The paradox is resolved by the observation that distant stars are of finite age, and recede from the observer as the universe expands.

Further reading: Scott Chase

How the moon affects our sleep

Just as solar cycle influences when we sleep, a new analysis finds that lunar cycles have some effect too. In the few days before and after a full moon, volunteers of this study took an average of 5 extra minutes to fall asleep, slept 20 minutes less per night, their delta activity (a measure of how deeply they were sleeping) was 30% lower than at other times, their level of melatonin, a sleep-related hormone, was reduced, and they reported, subjectively, that they had not slept as well as usual.

The study involved 33 volunteers who were completely isolated from daylight (and thus moonlight too). Thus, this effect must not be because of the direct effect of moonlight but instead it may be an endogenous cycle that evolution has learnt over millions of years.

Reference: C. Cajochen et al. Current Biology 2013

Further reading and Image credit: The Economist

The blue light of death

Death begins with an organised and consistent pattern of change. This is the conclusion drawn by a study that observed a simple worm (C. elegans) dying. When UV light was shone upon it, they found that as it began to die, the intensity of blue light emitted from it grew travelling from one end of the intestine to the other, and it reached its maximum density at the moment it died, before fading away.

This blue light is created because of fluorescence of simple molecules called anthranilic acids. These are generated when cell walls break open releasing them. Because the intensity slowly increased, it meant that cells were dying sequentially before the death of an organism occurred.

This is counterintuitive to theory which has persisted about death. That theory states death occurs because damage accumulates in cells. If that were the case then all cells in the worm should’ve glowed simultaneously and the intensity ought to have increased in all of them, which was not observed.

Reference: C Coburn et al. PLOS Biology 2013 

Further reading: Luc Henry in The Conversation

Image credit: Wellcome Trust