If Stephen Hawking was a star, he'd have gone out like a supernova.

Not one to fade into retirement quietly, the famous physicist's predictions were a constant feature of front page news until the very end, leaving us to question which of his warnings were profound words of wisdom, and which were the nervous concerns of a celebrity scientist.

But whether you agree with them or not, these five warnings will rightfully keep humanity talking for years to come.

1. Humanity is on a path to either disaster or the stars

There are a lot of words we could use to describe Stephen Hawking. It's hard to know if 'optimistic' is one of them.

"We face a number of threats: nuclear war, global warming and genetically engineered viruses," Hawking told Radio Times in 2016, according to Sarah Knapton at The Telegraph.

"Although the chance of a disaster on planet Earth in a given year may be quite low, it adds up over time, becoming a near certainty in the next thousand or ten thousand years."

Hawking reckons our destiny is to become a space-faring species. If we can avoid knocking ourselves off in the next century or so, at least.

"However, we will not establish self-sustaining colonies in space for at least the next hundred years, so we have to be very careful in this period."

We'll do our best, Professor Hawking.

2. We need to get up and move around a little more

Hawking made his mark in science by studying things with enormous masses – black holes.

Whether that qualified him to become a spokesperson against obesity is up for debate. But in 2016, he did just that, delivering a speech addressing the seriousness of growing waistlines.

"Today too many people die from complications related to overweight and obesity," Hawking said in a video ad promoting a Swedish non-profit company called GEN-PEP. "We eat too much and move too little."

The answer, according to the advertisement, is to eat less and get up and move around for at least half an hour each day. Or a whole hour if you're a kid.

"It's not rocket science," Hawking claimed.

Well, no. But we're not sure everybody would agree with that statement.

3. Artificial intelligence will replace us all

Our time dominating this planet will soon come to an end. Worst of all, we might have crossed the point of no return.

In an interview with Wired magazine last year, Hawking warned: "The genie is out of the bottle. I fear that AI may replace humans altogether."

The best we might be able to do is ban AI's use in the military and pay attention to how it's slowly taking over our jobs.

Does this mean that if we do head for the stars, we should do it without the help of artificial intelligence? The debate on that one continues as well.

4. Aliens probably won't want to be our best friends

While we're keeping trim, working on our environmental problems, keeping AI relatively unintelligent, and putting our feet on Mars, we should also try to keep quiet.

Hawking was convinced aliens were out there somewhere.

"As I grow older I am more convinced than ever that we are not alone," Hawking said in a 2016 film, Stephen Hawking's Favourite Places.

"After a lifetime of wondering, I am helping to lead a new global effort to find out."

While he was keen to help us find them, he wasn't all that sure we should be offering a warm handshake too quickly. Any species we stumble across will more than likely have some pretty awesome technology.

"If so, they will be vastly more powerful and may not see us as any more valuable than we see bacteria," warned Hawking.

5. At the rate we're going, experts will be extinct

Well, ok, he never said "extinct". But we know he was thinking it!

In a speech he delivered in March 2017, he claimed, "We are witnessing a global revolt against experts."

With fake news becoming big news, Hawking responded to questions on the state of the media by encouraging us to listen to the advice of those who devote their time to studying problems.

Hawking told the audience that solutions to our environmental challenges and potential AI threats will come from science and technology.

And this is one piece of advice from Stephen Hawking we can all get behind.