Earth could be reduced to a dense mass measuring just 330 feet across if particle accelerators set off a catastrophic chain of events, the astronomer royal has warned.
In his latest book, On The Future: Prospects for Humanity, Prof Lord Martin Rees, outlines the existential threats facing the planet, which include climate change, nuclear war and artificial intelligence.
In a chapter addressing whether mankind is doomed, he argues that scientists carrying out experiments which smash atoms together into quarks - such as protons and neutrons - could theoretically destroy humanity.
“Maybe a black hole could form, and then suck in everything around it,” he writes. “The second scary possibility is that the quarks would reassemble themselves into compressed objects called strangelets.
“That in itself would be harmless. However under some hypotheses a strangelet could, by contagion, convert anything else it encounters into a new form of matter, transforming the entire earth in a hyperdense sphere about one hundred metres across.”
Prof Rees said the third risk from particle accelerators, such as the Large Hadron Collider at Cern, was from a ‘catastrophe that engulfs space itself.’
“Empty space - what physicists call the vacuum - is more than just nothingness. It is the arena for everything that happens. It has, latent in it, all the forces and particles that govern the physical world. The present vacuum could be fragile and unstable.
“Some have speculated that the concentrated energy created when particles crash together could trigger a ‘phase transition’ that would rip the fabric of space. This would be a cosmic calamity not just a terrestrial one.”
Prof Rees pointed out that particles of much higher energies than are created in accelerators already collide frequently in the galaxy, without ripping space apart.
However he warns that current understanding at the frontiers of physics is still ‘shaky’ and it would be ‘presumptuous’ to assign a probability to the likelihood of a calamitous, world ending accident.
“Innovation is often hazardous, but if we don’t forgo risks we may forgo benefits,” he said.
“Nevertheless, physicists should be circumspect about carrying out experiments that generate conditions with no precedent, even in the cosmos.
“In the same way, biologists should avoid creation of potentially devastating genetically modified pathogens of large-scale modification of the human germline.
“Many of us are inclined to dismiss these risks as science fiction, but give the stakes they could not be ignored, even if deemed highly improbable.”
On The Future: Prospects for Humanity is published by Princeton University Press on 24th October.