Today I learned: About the GNOME Shell Extension NASA APOD Wallpaper Changer.
Well, it changes your desktop background to the NASA image of the day, every day.
I just felt felt like mentioning it, because although you do not realize it that much, spaceflight has an impact on everyone's life. And it is an existentially important endeavour for humankind. With this extension you get a glimpse at what spaceflight does and you get a breathtaking wallpaper too.