The Universe can expand without there being anything outside it for it to expand into, says science writer and astrophysicist Adam Becker. He explains this mind-bending idea to BBC Earth's Michael Marshall and Melissa Hogenboom, with help from the animators at Pomona Pictures.
Join over six million BBC Earth fans by liking us on Facebook, or follow us on Twitter and Instagram.
If you liked this story, sign up for the weekly bbc.com features newsletter called "If You Only Read 6 Things This Week". A handpicked selection of stories from BBC Future, Earth, Culture, Capital, Travel and Autos, delivered to your inbox every Friday.