A Harvard scientist has issued a chilling warning about a mysterious interstellar object hurtling through our solar system, and says it could spell disaster for Earth. 

Professor Avi Loeb, who is well-known for pushing bold and often polarizing theories about extraterrestrial life, has been tracking the object, named 3I/ATLAS, since it was first spotted on July 1.  

If the object is an alien craft, Loeb warned it could be carrying a probe or even a weapon. He predicted that such an intercept vehicle would reach Earth between November 21 and December 5, 2025. 

The timeline is based on calculations that 3I/ATLAS will pass behind the sun from Earth's perspective this October, a time he ominously suggested could be used to prepare the attack.

Referring to the object as a 'mothership,' he explained that its position would be an efficient way to seed habitable planets with probes.

This strategy would allow the devices to 'intercept the planets while the mothership continues on its journey to the next star.'

'It may come to save us or destroy us. We'd better be ready for both options and check whether all interstellar objects are rocks,' said Loeb.

Chris Lintott, an astronomer at the University of Oxford, has dismissed Loeb's claims as 'nonsense on stilts,' telling Live Science that the alien probe theory is an 'insult to the exciting work going on to understand this object.' 

Loeb has remained adamant that something about 3I/ATLAS does not add up. 

He said its retrograde orbit, meaning it's moving against the flow of the solar system, is oddly aligned with Earth's path. 

'3I/ATLAS might be an alien probe,' he said, citing its 'unusually rare trajectory,' which just so happens to align closely with the orbital plane of the inner planets, including Earth. 

He puts the odds of that happening naturally at just 0.2 percent. 

'At its closest point to the sun on October 29, fears of an alien invasion could send stock markets crashing,' Loeb said. 'In that scenario, citizens would lose their trust in governments to protect them.' 

He went so far as to compare the potential chaos to a military ambush, saying: 'Facing a high-tech alien visitor could feel like Iran's air defenses when US B-2 bombers appeared, silent, unstoppable, and overwhelmingly powerful.' 

The object, believed to be about 12 miles wide, is unusually large for something hurtling in from outside the solar system. 

According to Loeb, if it were natural, we would have already spotted millions of similar objects. 'But we haven't,' he said. 

He has published three pre-print papers laying out the case and has even suggested that NASA attempt an interception using its Juno spacecraft when the object passes near Jupiter.

'In my view, we need a risk scale for interstellar objects,' Loeb said. 'A zero would be a natural comet. 

'A 10 would be a verified technological object, possibly powered by an engine or emitting artificial light.'

He also believes governments should already be forming task forces, including scientists, policymakers and even psychologists, to determine how to respond and how to break the news to the public without triggering panic.

Loeb's warnings have grown increasingly urgent, culminating in one dramatic statement: 'It may come to save us or destroy us. We'd better be ready for both options.'

If 3I/ATLAS is more than just a rock, he said Earth is woefully unprepared. 

'The visitor,' he warned, 'is already in our backyard.'

Even if the object turns out to be artificial, Loeb admitted there's little humanity could do. 

At nearly 60 miles per second relative to Earth, it's moving far too fast for any of our current rockets to reach.

'If the hypothesis that 3I/ATLAS is a technological artifact proves correct, there are two possible implications: either its intentions are entirely benign, or they are malign, said Loeb. 

'In the first case, humanity need only wait and welcome this interstellar messenger with open arms. It is the second scenario that causes serious concern.'

He added that because the second possibility has serious consequences, we can use the idea behind Pascal’s wager. 

'Blaise Pascal argued that it’s smarter to believe in God because the possible benefits of believing are much greater than the losses if you’re wrong,' Loeb explained.

'Similarly, in our case, it makes sense to warn humanity about the risk from 3I/ATLAS, even if it turns out to be just a theory. 

'The cost of not warning could be much worse than the cost of being wrong.'