A:The unnecessarily scary muscle jerks that happen as you’re falling asleep are known as hypnic jerks. According to Dr Mark Mahowald, director of a sleep-disorder clinic in Minneapolis, “As far as I know, we don’t have a clue why it happens.” There are a couple of theories, though. The most simple is that in the process of going to sleep the muscles have to relax, so if the body has been engaged in a physically stressful, repetitive activity that day, they spasm. Many believe that between dozing off and entering REM (deep) sleep, there is still some communication between the brain and the muscles. So, if you think of something stressful, your brain tries to jolt your body back into the ‘awake mode’ in order to fend off the perceived danger.
The most common theory, though, is that as your body prepares to make the transition from alertness to sleep, many physiological changes occur – breathing and heart rate slowing. There is a point where the muscles completely ‘let go’ as you are slipping out of consciousness. Sometimes, the brain misinterprets this sudden relaxation as a sign that you are falling, and sends messages to your arms and legs to thrash around in an attempt to keep you upright as you ‘fall’. This would make sense, as you often awake like this after a dream of falling.
Q:What’s the closest sound to silence that can be recorded on an audio cassette?
A:In the early 1900s, Bell Laboratories did the most comprehensive study of human hearing ever. They discovered that the demographic group with the best hearing by far was black women aged 18-22. Using a sample of these women, they discovered that the quietest sound the sample were able to hear was 0.0002 Micro-Bars pressure. They labelled this sound 0 decibel SPL (sound pressure level); the quietest sound perceivable by human ears. While 0dB-SPL, the closest sound you can get to ‘silence’, could be recorded on an audio cassette tape, it would be indistinguishable from the bias noise; the noise you can just about hear when you play a blank tape.