Warning: This post contains spoilers for season seven of Game of Thrones. Neil deGrasse Tyson is putting his scientific expertise to use solving one of the Internet’s most pressing questions: How was the undead Viserion able to bring down the Wall on Game of Thrones? The famed astrophysicist took to Twitter Sunday to drop some thermal physics knowledge on fans still wondering about the difference between regular and blue dragon fire following the climactic finale of Thrones‘ seventh season.