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Nights 1 to 3 · Lesson 3 of 11

Morning Daylight and Dimmer Evenings for Better Sleep

Learn how light sets your body clock, and use morning daylight and a dim last hour before bed to help your sleep.

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THE WRITTEN LESSONFollow along at your pace

Your body has a clock that helps decide when you feel alert and when you feel sleepy. In this lesson you learn how light sets that clock, and how to use it. This is general information, not medical advice.

Light sets the clock

Light and darkness are the main signals that set your body clock. That is why the timing of light matters so much: the same lamp or the same sunny window can help or hurt, depending on the hour.

A round body-clock dial with a light day half marked DAY with a sun and a dark night half marked NIGHT with a moon. Beside it the words Light and Darkness have the labels The main signals and Timing of light matters.(opens the full-size picture)
Light and darkness are the main signals.

Morning light and evening light

Morning light tends to move your clock earlier, so sleepiness comes earlier at night. Evening light tends to move it later, so bedtime drifts later.

Two cards. Morning light shows a sun and a body-clock dial with its hand turned back, with a tick and the words Earlier bedtime. Evening light shows a bright lamp and a dial with its hand turned forward, with a red cross and the words Later bedtime.(opens the full-size picture)
The same clock, nudged in opposite directions.

A small camping study

In one small study, eight adults spent a week camping with only natural light. Their body clocks moved about two hours earlier. Eight people is a very small study, but it shows how strong light can be.

A tent under a sun and moon beside eight small people. Two alarm clocks, Before and After, are joined by an arrow labelled About 2 hours earlier. A label reads Only 8 people: a very small study.(opens the full-size picture)
Eight people only, so treat it as a hint.

Get outside, and move

So spend some time outside in daylight every day when you can, especially in the morning. Being active during the day helps too. Just avoid hard exercise in the hour before bed.

A walker with a backpack beside a sun, with the labels Outside, especially in the morning and Being active by day helps too. A timeline below has a dark block, Daylight and moving, in the morning, and a crossed-out block, Hard exercise, in the last hour before bed.(opens the full-size picture)
Move by day, keep the last hour calm.

Dim the evening

In the evening, do the opposite. Make the last hour before bed quiet, without bright lights or big screens. Bright light then may signal your brain that it is time to be awake.

A soft lamp and an armchair, with a TV and a laptop each crossed out in red. Labels say Last hour: quiet and dim and Bright light may say: stay awake.(opens the full-size picture)
A lamp and a chair, not a bright screen.

Larks, owls and everyone between

Some people are natural early larks, others are night owls, and most are somewhere in between. You cannot change your type completely, but more morning light and dimmer evenings are within your reach.

A bell curve with a small bird at the Larks end on the left, an owl at the Owls end on the right, and the middle filled in and labelled Most people. A label says Morning light plus dim evenings: within reach.(opens the full-size picture)
Most people sit in the middle.

Working nights or flying across time zones?

If your days and nights are not the usual way round, treat these steps as aims, not a test. The jet lag article below looks at timing light after travel.

YOUR TURN

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Read the full lesson script

Your body has a clock that helps decide when you feel alert and when you feel sleepy. In this lesson, you'll learn how light sets that clock, and how to use it.

Light and darkness are the main signals that set your body clock. That's why the timing of light matters so much.

Morning light tends to move your clock earlier, so sleepiness comes earlier at night. Evening light tends to move it later, so bedtime drifts later.

In one small study, eight adults spent a week camping with only natural light. Their body clocks moved about two hours earlier. Eight people is a very small study, but it shows how strong light can be.

So spend some time outside in daylight every day when you can, especially in the morning. Being active during the day helps too. Just avoid hard exercise in the hour before bed.

In the evening, do the opposite. Make the last hour before bed quiet, without bright lights or big screens. Bright light then may signal your brain that it's time to be awake.

Some people are natural early larks, others are night owls, and most are somewhere in between. You can't change your type completely, but more morning light and dimmer evenings are within your reach.

So remember: light is the main signal for your body clock. Morning light moves it earlier, and evening light moves it later. So get outside in the day, and keep your last hour dim. Before the next lesson, spend some time outside in daylight tomorrow morning, and dim the lights in your last hour tonight. In the next lesson, you'll find your caffeine cut-off.