How Long is a Day?

describe the terms ‘solar day’ and ‘sidereal day’
explain why a solar day is longer than a sidereal day
interpret charts and diagrams showing the variation in daylight length during a year
demonstrate an understanding that there are seasonal variations in the rising and setting of the Sun

      
pic   Ian Britton - Freefoto.com

The Sun rises in the East and sets in the West. It culminates (reaches its highest point) around noon.

How much time passes between sunrise and sunset? Obviously this varies throughout the year. In winter the sun rises later in the day and sets earlier. We should understand these patterns. Below is a download link to a spreadsheet of sunrise and sunset times. You are going to analyse this data looking for patterns. We will then explain these patterns in terms of the relative motion of the Sun and Earth.

Right click HERE and choose "save target as" to download an Excel file of sunrise and sunset times in London in 2005.

Use this data to produce the following graphs.

1. How sunrise time varied throughout the year.

2. How sunset time varied thought the year.

3. How the number of daylight hours varied throughout the year.

From these graphs and/or the data find

a) Which was the longest day?  b) Which was the shortest? c) Which two days had 12 hours of daylight?

What is daylight saving?  Why was it introduced?

Ian Britton - Freefoto.com
Spring	Summer
Autumn	Winter

The cycles of life on Earth are bound to the seasons. In the summer it is warm, the Sun is high in the sky and the days are long. In winter it is cold, the Sun is low in the sky and the days are short.

Days vary in length throughout the year due to the tilt of the Earth.

The Earth receives many types of electromagnetic radiation from the Sun. The important two are light and heat (infra red). For six months of the year the Northern hemisphere is titled towards the Sun. Radiation from the Sun arrives from almost above our heads. For the other six months the northern hemisphere is tilted away from the Sun. Radiation from the Sun arrives at angle.

Because of this
a) it is much more spread out over a larger area so it is less concentrated and
b) it passes through a much thicker amount of atmosphere so more of it is absorbed before it reaches the Earth.

Shine a torch on a piece of paper. Now turn the paper through 45 degrees so that the light hits it an angle. How does this explain why it is colder in the winter?