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Earth Science

Judith Kpakpo

Day and night

What are day and night?

Daytime is when you can see the sun from where you are, and its light and heat can reach you. Nighttime is when the sun is on the other side of the Earth from you, and its light and heat don’t get to you. 

We get day and night because the Earth spins (or rotates) on an imaginary line called its axis and different parts of the planet are facing towards the Sun or away from it.

It takes 24 hours for the world to turn all the way around, and we call this a day. Over a year, the length of the daytime in the part of the Earth where you live changes. Days are longer in the summer and shorter in the winter.

Top 10 facts

  1. It takes 24 hours for the Earth to turn all the way around (rotation). That makes one day and one night.
  2. At any moment, half of the world is in daytime and half is in nighttime.
  3. The world is like a ball. We call the top half the Northern hemisphere and the bottom half the Southern hemisphere. The (imaginary) line between them is called the equator.
  4. In the Northern hemisphere, we have summer in June, July and August and winter is in December, January and February.
  5. In summer the days are longer than they are in winter. In London, the longest day is about 16 hours and 39 minutes and the shortest is 7 hours and 45 minutes.
  6. In the Southern hemisphere the seasons are the other way around. When it is summer in Europe, it is winter in Australia. Imagine celebrating Christmas on a long, hot summer day!
  7. To help us understand where we are in the world, we also split the world into right and left halves called the Eastern hemisphere and the Western hemisphere.
  8. The (imaginary) line between the Eastern and Western hemispheres is called the ‘Prime Meridian’ and it goes through Greenwich Royal Observatory in London.
  9. The world is split into time zones. Continental Europe is in the time zone to the east of Britain, so time is one hour ahead there; when it is 1pm in Britain it is 2pm in France.
  10. On the opposite side of the world from London is the International Date Line. On one side of the line time is 12 hours behind Britain, and on the other side time is 12 hours ahead of Britain. That means that it is a different day on each side of the line.