Suggest edit — circadian-rhythm

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# circadian rhythm

the 24-hour internal clock that governs when you're alert, when you're sleepy, and how well everything from digestion to cognition works.

## the key signals

three main signals ("zeitgebers") tell your body what time it is:

**light** is the primary one. morning light exposure (10-15 min of bright outdoor light within an hour of waking) anchors the whole cycle. evening light — especially blue wavelengths — pushes the clock later.

**meal timing** entrains peripheral clocks in the liver and gut. eating at inconsistent times creates internal desynchrony: your brain thinks it's one time, your gut thinks it's another. see [[food-and-focus]] for how this affects cognitive performance.

**temperature** follows a circadian rhythm — lowest around 4-5am, highest in late afternoon. hot showers before bed paradoxically help by dropping core temperature via vasodilation. sleeping cool (65-68F) aligns with the body's natural temperature drop.

## my experiments

i've gone through phases of trying to shift my circadian rhythm earlier. the things that actually worked:

1. morning light — non-negotiable. this is the foundation.
2. consistent wake time — even on weekends. the body hates schedule variance.
3. no food close to bedtime — eating late shifts peripheral clocks later and makes sleep quality worse.
4. wind-down routine — same sequence of actions each night signals the transition. not about "relaxing" so much as about consistency.

what didn't work: trying to force an earlier bedtime without changing the morning anchor. you can't push the clock from the sleep end — you have to pull it from the wake end.

## the connection to work

understanding circadian rhythm reframes energy management. it's not about willpower — it's about alignment. working during your biological peak (usually mid-morning for most people) and resting during your biological trough (early afternoon) isn't laziness; it's [[operation-optimization]].