Learn with ABA English – Your body clock

Good day hot stuff,

How are you today? Let us know in the comments section!

Napoleon said: “Six hours’ sleep for a man, seven for a woman, and eight for a fool”. Do you agree? What time do you wake up naturally and how many hours do you need?

To learn more about your internal body clock, follow the steps:

1. Read the text
2. Understand the vocabulary
3. Watch the mini-documentary


Hello, my name is Till Roenneberg, and my colleagues and I investigate the body clock and I will explain to you now why so many people in our society, two-thirds of our society, are woken up in the middle of the night.

Our daily lives are controlled by three clocks: one is ticking away in a body. It’s synchronized to the clock that is provided by the rotation of our Earth, which makes day and night, so that’s the second clock. And more recently in our history we have added another clock which is the social clock.

Now, if we look at the social clock on the wall and it tells us a certain time and we now look at the internal time of an individual, it can be completely different.

Body clocks are set by the sunlight and the darkness of the night.

When we were still working outside, when we were farmers, we could look at the sun and we know what time of the day it was, and the body clock was also synchronized with the sun. Nowadays, our body clocks run differently because we don’t see the sun anymore and that makes our body clocks go later and later and later.

Take a late type, he falls asleep according to his body clock but he has to wake up on a work day with his alarm clock, way before his body clock would have woken him. Now this difference between what the social clock wants us to do and what our body clock wants us to do we call social jetlag.

Now the sleep behaviour of most people is very different on work days and on weekends. While during the workweek they get too little sleep and are woken up by the alarm clock in the middle of their biological night, they sleep in on weekends in order to fill up their tanks with the sleep they need.

When we look at the body clocks in all organisms on this globe we find that it’s the sun and the darkness that sets these clocks. The difference between the time of our night and darkness and the sun time, and the social time can be quite remarkable. Let’s presume that someone needs to get up at 6 o’clock to go to work, if this somebody works in Prague he may get up with the sunrise. Now, in the most western city in Europe, Santiago de Compostela in Northern Spain, this person has to get up one and a half hours before the sun rises. So there are huge differences between what our social clocks tell us and what actually sunrise and sunset tell us.

By every longitude we travel from east to west in the time zone, the body clock becomes later by four minutes and that is exactly the time it takes the sun to rise from one longitude to the next.

Now we’ve seen that very few people in our population can actually live according to their body clock, so they suffer from social jetlag. Living against their body clock has consequences for most people. Most people with social jetlag are likely to be smokers, they are more likely to drink alcohol, and people with social jetlag drink a lot of caffeine during the day. And now we’ve discovered another consequence of living against the body clock, and that is that if you are already a little chubby and not very thin, it is very likely that living against the body clock makes you even become obese.

In view of all of these consequences, it is high time we do something against social jetlag.


cuckoo120507_560Colleagues – a person who works with you.

Two-thirds – two out of three or 2/3.

Ticking – to make a small, quick, and often rhythmic tapping sound.

Provided – to make (something) available.

Certain – not having any doubt about something : convinced or sure.

Farmers – a person who runs a farm.

Nowadays – at the present time.

Jetlag – a tired and unpleasant feeling that you sometimes get when you travel by airplane to a place that is far away.

Globe – an object that is shaped like a large ball with a map of the world on it.

Remarkable – unusual or surprising : likely to be noticed.

Longitude – distance measured in degrees east or west from an imaginary line (called the prime meridian) that goes from the North Pole to the South Pole and that passes through Greenwich, England .

Likely – used to indicate the chance that something will happen.

Chubby – someone who is a little bit fat.

Obese – very fat : fat in a way that is unhealthy.

High time –  it is about the right time for something.

Mini-documentary Video

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