“In Einstein's equation, time is a river. It speeds up, meanders, and slows down. The new wrinkle is that it can have whirlpools and fork into two rivers. So, if the river of time can be bent into a pretzel, create whirlpools and fork into two rivers, then time travel cannot be ruled out.”

American theoretical physicist, science communicator, futurologist, and writer of popular science

Michio Kaku is an American theoretical physicist, science communicator, futurologist, and popular science writer. He is a professor of theoretical physics at the City College of New York and the CUNY Graduate Center. He has written several books on physics and related subjects, and he is a familiar presence in radio, television, and film. He also writes regularly for his own blog and for other popular media outlets. In 2021, he received the Sir Arthur Clarke Lifetime Achievement Award for work that helped connect science and science fiction.