Theoretical physicist Stephen Hawking has once again opened up about his fears and warned the world to be hesitant about making contact with alien life.
He said planet Gliese 832c potentially had alien life but said humans needed to be wary.
“One day, we might receive a signal from a planet like this, but we should be wary of answering back,” he in the documentary, Stephen Hawking’s Favourite Places.
“Meeting an advanced civilisation could be like Native Americans encountering Columbus. That didn’t turn out so well.”
He claimed alien life could be "rapacious marauders roaming the cosmos in search of resources to plunder, and planets to conquer and colonise”.
His fears have not changed since he first spoke out about it on the Discovery Channel in 2010.
He said as he grew older he became more convinced humans were not alone.
“After a lifetime of wondering, I am helping to lead a new global effort to find out,” he said.
Planet Gliese 832c has five times the mass of earth and a similar temperature.
It’s been described as an inhabitable super earth, that’s 16 light-years from our planet.
A light-year is about 9.5 trillion kilometres, which sounds like a lot, but in the perspective of space it’s not that far.
Mr Hawking has also warned earth could become as hot as Venus as a result of climate change.
He told the BBC climate change could turn the planet into a hothouse, and Trump’s decision to pull out of the Paris Climate agreement to reduce CO2 levels could accelerate the threat.
“We are close to the tipping point, where global warming becomes irreversible,” he said.
“Trump’s action could push the earth over the brink, to become like Venus, with a temperature of 250C, and raining sulfuric acid.”
Hawking also said humans may have to consider life on a planet elsewhere because of the destruction of earth due to climate change.
Live Science reports experts don’t believe earth could hit those extreme temperatures because it is further away from the sun than Venus and doesn’t have a carbon dioxide atmosphere as thick.
Pennsylvania State University climate scientist Michael Man said: “Hawking is taking some rhetorical license here”.
“Earth is further away form the sun than Venus and likely cannot experience a runaway greenhouse effect in the same sense as Venus — ie a literal boiling away of the oceans. However Hawking’s larger point — that we could render the planet largely inhabitable for human civilisation if we do not act to avert dangerous climate change — is certainly valid.”
This story originally appeared in news.com.au