Beakman explains that the seasons are created by the Earth's axis being tilted. He brings Capernicus in to explain more and then uses a model to show how depending on Earth's orbit and axis the amount of sun on a given portion will affect seasons.
The team at NASA is trying to launch a capsule and bring it back to Earth. To do so, they need to calculate its change in trajectory as it moves from an elliptical orbit to a parabolical orbit. Katherine discovers that they can use Euler's Method to approximate the change in trajectory.