LONDON (AP) — Stephen Hawking understands the workings of the universe — but says he cannot fathom the popularity of Donald Trump.

The British astrophysicist told ITV's morning show Monday that the presumptive Republican Party candidate for U.S. president "is a demagogue who seems to appeal to the lowest common denominator."

Hawking also appealed to British voters to vote to keep the United Kingdom inside the European Union in a June 23 referendum. He said remaining within the EU provided essential support for British scientific research as well as its economy and security.

He said: "Gone are the days we could stand on our own against the world. We need to be part of a larger group of nations, both for our security and our trade."