Every week, the BBC Focus magazine solves some doubts of its readers. Below is a selection of their responses for the curious.
What is the best treatment for insomnia?
There is no magic formula, but insomnia, and worry about insomnia, can become a bad habit that feeds on itself.
If you don’t sleep, it’s tempting to watch TV, check the phone, drink too much alcohol. All these behaviors, experts say, have to change.
Instead, you need a lot – although not before bed – avoid caffeine after noon, avoid large dinners and keep alcohol consumption.
Good «sleep hygiene» includes observing regular bedtimes and using the bedroom only for sleep and sexual intercourse – not for working, emailing, making phone calls, watching TV or any other stimulating or stressful activity – of so that the body learns to associate that space with sleep.
And if you get up in the middle of the night, don’t go looking for any of your gadgets or even a book.
A simple trick that works for some people is to sit in the dark on the edge of the bed. Soon you will get bored and sleepy.
Do birds fly among the clouds?
Most birds don’t fly higher than 150 meters above the ground, so they don’t go through the clouds, unless it’s cloudy.
But migratory birds can reach heights of 6,000 meters.
The species that has been seen flying the highest was a flock of beaver swans (Cygnus cygnus), at 8,800 meters. It is high enough to put them between low and mid-altitude clouds, including the stratus and upper stratus that cover the sky on an overcast day.
Flying through clouds is no worse than flying in the rain, and birds fly slow enough to avoid mountains and buildings that appear out of nowhere in low visibility situations.
How can a cold compress relieve a headache?
A sinus headache occurs when inflamed membranes in the sinuses block the flow of mucus.
Cooling the blood near the head can send a signal to the hypothalamus in the brain that the body temperature is too low and that blood should be diverted from the head to circulate to other organs. This reduces inflammation of the sinuses.
But the most common type of headache is tension headache. Any benefit you may feel from putting on a cold compress in this case is probably due to the comforting feeling you get from it, which reduces stress levels.
Can photosynthesis occur in moonlight?
Photosynthesis uses the energy from sunlight to turn carbon dioxide and water into glucose and oxygen.
The plant uses part of this glucose to create cells, while another part is converted back into carbon dioxide and water to provide energy for its metabolism.
The light of the full Moon on a clear night is only one six-thousandth as bright as the Sun on a cloudy day. Still, photosynthetic reactions occur, just 6,000 times slower.
That speed is too slow to be useful to the plant, because as a result it gains less carbon dioxide than it loses through respiration of its cells.
As the Sun rises in the sky, photosynthesis becomes more effective, until the plant has absorbed CO2 to restore it so it uses enough to supply itself with energy.
This is called the «compensation point» and occurs in the early morning, as well as late afternoon, when light levels drop again.
Outside of those hours, photosynthesis is not useful for plants and many close their leaves at night, so that the circadian rhythms that control flowering are not affected.