Since we use that analogy in the Threads to think more about what we are seeing, the analogy has been reproduced here in the Teacher Background so that you don't have to search for it in the text of the Thread itself. Think about making peanut butter and jelly sandwiches. Imagine you are only allowed to have a spoonful of each ingredient, but you have a choice between both large or small pieces of bread to spread the ingredients over. Think about the thickness of the sandwich in relation to the bread size. Then we can bring the meaning around full circle.
Light is made up of little bits of energy.
In the winter for us, our hemisphere of the Earth is tilted back at an angle from the Sun, and so the sunlight is spread out along that angle. Spread-out sunlight means cooler temperatures. One thing to remember about the planet Earth is that our atmosphere works like a big blanket to keep heat on the surface longer. This is why the longest day of the year, the summer solstice, is rarely if ever the hottest day of the year. It takes time for the surface of the Earth to heat up or cool down, with the atmosphere surrounding it.