If I was randomly asked what time it is, I wouldn’t be very accurate without looking at a clock. Likewise, if I was asked to guess when the clock hits exactly 8pm, I would be pretty far off. Yet I very frequently wake 2-3 minutes before my alarm goes off. How can my passed out brain be such an accurate time keeper?
In: Biology
Humans have two different things going on. One is our body clock (the proper term is the ‘circadian rhythm’), which is a 24 hour cycle of hormones that synchs up with sunrise and sunset. The other is our sense of time passing, which isn’t based in our hormones at all.
The body clock isn’t something you can consciously tap into. It’s a background thing that tunes things like our metabolism. But since it’s synced to sunrise and sunset, it’s very accurate. Waking up in the morning and feeling sleepy at night is triggered by the body clock system. If we were to see absolutely no light – like if we spent a couple days in cave – our body clock would keep up its cycle pretty well.
In our every day lives, it’s constantly adjusting based on when we see sunlight light with our eyes, feel sunlight on our skin, and are physically active. This means that sleep masks and blackout curtains delay when our bodies think ‘sunrise’ is, and artificial light in the evening – especially blue light – adjusts when our bodies think ‘sunset’ is. This process is also what’s behind jetlag.
Our conscious sense of time, however, is very subjective, and isn’t linked to any specific external things. When we’re stressed and thinking faster, time seems to move slower. When we’re relaxed or distracted, we think slower, so time feels like it’s going by faster.
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