Stephen Hawking, considered by some to be one of the most intelligent people in the world, has a bright idea to unite the world. The leading nations should combine their resources and effect a return to the moon by 2020. The effort would be followed by an expedition to Mars in 2025 and a lunar base in 30 years. He made this proposal at the Starmus Festival, which celebrates the sciences and arts in Trondheim, Norway according to the BBC.

Why the moon? Why Mars?

Hawking gave some familiar reasons for an expanded space program. It will unite a competitive world.

Space exploration will excite interest in the sciences in young people. It will help to save the Earth now beset by depletion of natural resources and the ever-present threat of climate change. Spreading out into space will make sure that human civilization is not destroyed by a catastrophe such as an asteroid strike.

Takes a shot at Donald Trump

Hawking took the occasion to take a shot at President Donald Trump, the leader of one of the countries that will have to take the lead in any international space program. The issue was human-caused climate change, which Trump has expressed some skepticism about Hawking suggested that the president has made the “most serious, and wrong, decision on climate change this world has seen.”

What is the state of play on space exploration?

With the new administration in the United States, NASA’s deep exploration goals are in a state of flux again.

The Journey to Mars, the program of record since President Barack Obama announced it during a speech at the Kennedy Space Center in 2010, seems to be dying. Media rumors suggest that the Trump administration wants NASA astronauts to head back to the moon, the sooner, the better, in partnership with commercial companies. No word exists as to when an official announcement will be made.

The European Space Agency has been touting the so-called Moon Village as the next, great international space project when the International Space Station reaches the end of its operational life in 2024. Russia, Indian, and China each have lunar ambitions. A number of commercial companies, including Moon Express and Astrobotic, have plans to start lunar mining enterprises.

The bottom line is that the stage has been set for a return to the moon, something that has been proposed and then canceled twice by two presidents who happen to have been named George Bush. The only thing necessary will be for a world leader, almost certainly President Trump, tp pulled the trigger and start the ball rolling.