Observing Seasons

What patterns did you notice yesterday in the graphs we looked at? Do the Northern and Southern Hemispheres have the same seasons? Explain. The Northern and Southern Hemispheres have opposite temperatures. No, when it is winter in the North, it is summer in the South.

Scientists use models to demonstrate ideas, explain observations and make predications. Today we will use a light bulb to represent the sun. Students will also have a model of the Earth. The pencil is the axis of the Earth. Earth rotates in its axis. Please handle these with care. They are expensive!

Find the following on your globe: Equator North Pole South Pole Northern Hemisphere Southern Hemisphere Green dot: Mid-latitude location in North America like Phoenix. Black dot: Mid-latitude location in Southern Hemisphere like Australia, South America or Africa. Blue dot: High latitude location in Northern Hemisphere.

We will stand in a circle Our Earths will spin counterclockwise (Just like Earth) and our axis will point straight up and down Turn to sunset at the green dot It should be rotating from light to dark Turn to noon at the green dot It should be directly facing the sun Turn to midnight at the green dot It should be facing directly away from the sun Turn to sunrise at the green dot It should be rotating from dark to light

When the axis is vertical, do all the dots stay in the light for the same amount of time? Yes Does the model we just worked with explain why we have seasons? Nope, it shows day and night but it does not explain the data we looked at with different amounts of night and day. So…… What causes the different amounts of light?

The Earth is tilted on its axis. The axis runs through the North and South Poles. The North Pole of Earth always points to the North Star called Polaris. Polaris is really far away so we will just point our North Poles at the wall with Polaris on it. How much does the Earth tilt? 23.5 degrees Align your globes with Polaris. The A, B, C, D posters represent Earth in different locations as it travels around the Sun. Spin your model Earth slowly and make observations. What do you notice about the day lengths of each dot? They are different

Looking at the green dot, that’s us in Phoenix. Who sees longer daylight hours? What season would this be? Summer, days are longer Who sees longer nights? What season would this be? Winter, days are shorter Who is seeing equal amounts of night and day? What season(s) is it? Spring and Fall Spring follows winter Fall follows summer

Looking at the black dot in the Southern Hemisphere. Is the North Pole pointing towards or away from the sun? What season do you think it is? Are the seasons the same in the Southern and Northern Hemispheres? No Is it ever the same season in the Northern and Southern Hemispheres? Nope, when it is Summer in the Northern Hemisphere, it is winter in the Southern Hemisphere.

Now lets look at a high latitude position in the Northern Hemisphere. This would be places like Alaska. Spin your globes and look at how much day and night you see. What do you notice? Extreme amounts (24 hours) of day or night and some locations get day and night. What do you think happens at the South Pole? The exact opposite. When the North Pole has 24 hours of light, the South Pole has 24 hours of dark.

Why do we have seasons? Because the Earth is TILTED. The titles portion is not really any closer to the Sun though. The seasons are caused because there are portions of the Earth that get WAY more sunlight hours and thus have more time to warm that part. Now we can all move through all 4 stations and observe what is happening in each Hemisphere.

Answer the questions. Final thoughts Would a planet with no titled axis have seasons? Nope! Earth’s tilt results in seasons because there are more hours of daylight. The tilted spin axis results in seasonal changes in hours of daylight and night through out the year. The ANGLE of light is more direct in summer months and results in more intense heat.