Mary knew her her facts. The sun was a star and they couldn't survive without it. She also remembered that muggles used it for energy with solar panels. Some had mentioned time as well.

"The sun gives life itself, as plants can't grow without it, herbivores can't live without plants, and carnivores can't
live without herbivores. In the muggle world they use it to generate electricity with solar panels. The sun also appears to rise and fall when at different times throughout the year, so ancient people made the first calendar based on the sun and were able to tell when to harvest crops based on the sun."