Scientists, politicians and business people are beginning to ask themselves on unthinkable question.

What if our world becomes literally uninhabitable?

The past five years have collectively been the hottest on record, while 2016 was the single most scorching.

Should we be looking for alternative living arrangements?

And if so, where could we go?

The most obvious answer is the move, especially since U.

S President Donald Trump has instructed NASA to return there with humans.

By 2024.

NASA thinks that humans could live sustainably there by 2028 a cz, long as they can find the right technology to help us survive the freezing lunar night.

Two of the world's richest men have different ideas, however.

Fairyland musk.

The answer lies on Mars.

He has set up a company, Space six, which he hopes will eventually be able to take humans up to the Red Planet.

And he says that by 2050 he plans to have a city there.

Jeff Bezos, however, thinks that we shouldn't be going to a planet that's all.

Bring on the 19 seventies ideas of the Princeton scientist Gerard O'Neill, the others and founder has suggested instead that we should look to live on spinning colonies that orbit the sun will be reflected in through a giant array of mirrors on the weather, he says would be like Maui on its best day.

Willie around.

Mr Bezos believes that the best way to achieve this vision is to mine materials from the moon, where the gravitational pull is weaker and therefore it is cheaper and easier to launch them into space.

He has set up a company, Blue Origin, which is building a moon lander, which he hopes will take humans back to the moon by 2024.

Some critics say these are the idol or being expensive fantasies of middle aged men who grew up during the space race on which threatened to detract attention away from earthbound attempts to tackle climate change.