Katherine J. Mack (born 1 May 1981)[3] is a theoretical cosmologist who holds the Hawking Chair in Cosmology and Science Communication at the Perimeter Institute.

[4][1][5] Mack is also a popular science communicator who participates in social media and regularly writes for Scientific American, Slate, Sky & Telescope, Time, and Cosmos.

[2][15] After earning her doctorate, Mack joined the University of Cambridge as a Science and Technology Facilities Council (STFC) postdoctoral research fellow at the Kavli Institute for Cosmology.

Her research considers dark matter,[23] vacuum decay,[24] the formation of galaxies, observable tracers of cosmic evolution, and the Epoch of Reionization.

[8][17] Mack is a popular science writer and has contributed to The Guardian, Scientific American, Slate, The Conversation, Sky & Telescope, Gizmodo, Time, and Cosmos, as well as providing expert information to the BBC.

[34][35][36][37][38][39] Mack's Twitter account has over 300,000 followers; her response to a climate change denier on that platform gained mainstream coverage,[40][41] as did her "Chirp for LIGO" upon the first detection of gravitational waves.

[50][51] Her first book, The End of Everything (Astrophysically Speaking), was published by Simon & Schuster in August 2020, the firm having won the rights in an eight-way bidding battle.

[52][53] It considers the five scenarios for the end of the universe (both theoretically and practically),[52] and has received positive reviews both for its science outreach accuracy and its wit.