Power Outage

Last night, I went to bed at about 11 pm and read for half an hour. When I woke up next, it was still before 3 am. Though I managed to go back to sleep, I was woken up again by the noise of a brush rubbing the outside floor. It was yet dark… It was not happy sleep. Finally, I went out of bed at 10 am, and at 11 am electricity went out. I checked the circuit breaker unit here and all were on. Stepped out, I realized that the elevators were not working. I didn’t know there would be a “power disruption” today for the whole block. The power cut continued for about an hour.

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Why do I feel unbelievably sleepy while having coffee and reading, and why am I able to read after a 6-pack?