Presumptive GOP nominee Donald Trump just picked up one of the smartest men in the entire world as a fierce critic. This man has been lauded by the science community globally for his works in astrophysics, but seems to be baffled by Trump’s popularity.

Acclaimed astrophysicist Stephen Hawking admitted Monday Trump’s rise and admiration by American voters has truly stumped him. The Republican candidate “is a demagogue who seems to appeal to the lowest common denominator,” Hawking said on the ITV morning show in the UK.

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Hawking’s research has led to extraordinary breakthroughs in cosmology and understanding black holes and general relativity. He is also a supporter of Britain remaining with the EU in the June 23 referendum. “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,” Hawking said.

Trump is opposed to the UK staying within the EU, believing the country will economically sustain better if it is independent of the Union.