Why does it get darker earlier in the winter than it does in the summer?

Although the earth might look flat, if you look at it from outer space, it's a big sphere. But it's not straight. It's actually a bit wonky, and the amount of tilt is actually about 23.5 degrees. This means that part of the earth is tilted towards the sun, and part of the earth is tilted away from the sun. On one part of the orbit, the top of the earth is tilted towards the sun, which is the warm summer. This is when you get longer days. Further round in its orbit, it'll be pointed away from the sun. This is our winter, and the days are a lot shorter. Therefore, the length of the day is actually all down to how angled our planet is in space.