The Large Hadron Collider, which is a particle accelerator, shoots particles at incredibly high speeds, smashes them together, and scientists observe the fallout. According toScience Alert, these high-speed collisions have helped us discover a lot of new particles, but according to Rees, these discoveries come with several risks to humanity. In a new book, called On The Future: Prospects for Humanity, he gives some pretty dire possible outcomes of this type of advancement in science.

"Maybe a black hole could form, and then suck in everything around it," he writes, as Sarah Knapton reported over at the Telegraph. "The second scary possibility is that the quarks would reassemble themselves into compressed objects called strangelets. That in itself would be harmless. However, under some hypotheses, a strangelet could, by contagion, convert anything else it encounters into a new form of matter, transforming the entire earth in a hyperdense sphere about one hundred meters across." That's about the length of one soccer field or 330 feet.