Day, Night & The Seasons

1. Day, Night & The Seasons D. Crowley, 2007

2. Day, Night & The Seasons • To know what causes day, night and the seasons

3. Diet The best way to diet is to fly to the moon. Can you explain why this is not entirely true?! Although on the moon your weight would be less (because the pull of gravity is much smaller), your mass remains constant. So if you fly to the moon, although you’ll weigh less, there will still be the same amount of you there!

4. Day & Night • What causes the Earth to experience day and night? • See if you and a partner can come up with an explanation to this in the next five minutes…

5. Day & Night • Day and night are caused because the Earth is spinning on its axis • Every 24 hours the Earth completes one rotation - and most places on Earth experience 12 hours of sunlight (when that part of the Earth faces the sun), and 12 hours of dark (when that part of the Earth does not face the sun) So during one day, the dot will experience ~12 hours of sun, and ~12 hours of dark.

6. Seasons • The Earth is actually tilted, as shown below - by what has this got to do with the seasons? Earth Sun

7. Seasons • The seasons are caused by tilt of the Earth, either away or towards the sun as it orbits it during a year… Summer - in the Northern Hemisphere, the Earth’s tilt is closer to the sun Winter - in the Northern Hemisphere the Earth’s tilt is further from the sun So this is winter for the Southern Hemisphere! So this is summer for the Southern Hemisphere!

8. Summary • So day and night is caused by the spinning of the Earth on its axis (once every 24 hours) • Seasons are caused by the Earth being tilted - so during every year (when the Earth orbits the sun) the tilt is either closer to the sun or further away. If you are living on the bit of the Earth where the tilt is closet to the sun, you experience summer, and when the tilt is furthest away you experience winter • This is why when we experience summer, the Aussies experience winter (because we live on different hemispheres (top / bottom of Earth)) Spring Summer Autumn Winter

9. Sun in your eyes • In the summer in the UK the tilt of the Earth means we are closer to the sun than during winter - we notice that the sun seems a lot higher in summer, and we get much more sunlight (longer days) • In winter the sun seems lower in the sky, and the days are much shorter - this is because during summer the sun shines more directly on us, so we experience more sunlight (hotter) and for a longer period of time • During winter, the angle the sun shines on us is much more reduced, so it appears lower in the sky and is visible for a much shorter time. It also means the sun’s rays are more spread out, so it doesn’t get quite as hot! Summer Winter

10. Equator & Poles • Why is it hotter at the equator? • Why does the North Pole have 24 hours of sunlight during the summer? It is hotter at the equator for a number of reasons. Firstly the tilt of the Earth causing the seasons is much less of a factor here, so it gets a good amount of sun all year. Also, the angle the sun’s rays hit the equator is much more direct than that at the poles, causing the equator to heat up. The North Pole can experience sunlight for a whole day during summer. This is because during the summer, the North is closest to the sun, experiencing longer days. As the pole is right at the top of the Earth, the spin does not affect it - i.e. the pole remains facing the sun for a whole day! The Earth spins, but the North Pole remains facing the sun - so the sun never seems to set