READY
READY
Twenty minutes is the nap that leaves you better off. Past roughly half an hour you drop into deeper sleep, and waking out of that is where the thick-headed feeling comes from: sleep inertia, which can take half an hour of its own to clear. Short naps skip it entirely.
The other reason for the number is the evening: long afternoon naps eat into the pressure to sleep that builds through the day, and a two hour nap is a familiar way to end up awake at one in the morning.
The tip everyone gets wrong: start the timer when you lie down, and count the time it takes to fall asleep as part of the twenty minutes. Most people take ten to fifteen minutes to drop off, so a twenty minute timer usually delivers five to ten minutes of actual sleep, which is the amount that works. Timing twenty minutes of sleep instead puts you in the deep stage you were trying to avoid.
Put the phone face down with the page open. The countdown works from the clock, so a locked screen does not slow it down.
On a laptop, yes. On a phone the browser may suspend the tab's audio when the screen locks, so for a nap use your phone's own alarm as a backup.
Because deep sleep usually starts somewhere around the twenty-five minute mark, and waking out of it is what leaves you groggier than before the nap.
It is a real technique: caffeine takes about twenty minutes to take effect, so it arrives as you wake. Whether it suits you is another matter.