Boson battles brains (Image: John Lund/Getty)

Editorial: “‘Boring’ Higgs has powers we never dreamed of“

THE Higgs boson may have the right mass to wreck the universe – hurray! Death by Higgs is the simplest way to do away with a paradoxical menagerie of disembodied intelligent beings that shouldn’t exist, yet remain in the best cosmological models.

What’s more, the end is a comfy 20 or 30 billion years off. “That’s quite a few billion; it’s not like we should rush out and buy life insurance,” says Sean Carroll at the California Institute of Technology in Pasadena, who put forward the idea along with Kimberly Boddy, also at Caltech.


“That’s quite a few billion years away – it’s not like we should rush out and buy life insurance”

The paradox arose a decade or so ago, when physicists realised their models led to a future filled with Boltzmann brains: fully formed conscious entities that pop out of the vacuum. It sounds bizarre, but there’s nothing to stop matter sometimes randomly arranging itself in just the right way for this to occur. The problem arises when you add in the universe’s accelerating expansion.

This provides limitless time, space and energy for Boltzmann brains to form, even after life as we know it has winked out, causing them to eventually outnumber ordinary consciousnesses. But that would make the brains’ experience of the universe more typical than ours, which is a problem as our understanding of the cosmos assumes that we are typical observers.

Theories have been proposed in which the universe ends before the brains take over, solving the paradox, but these are mostly based on untested physics like string theory. By contrast, the Higgs boson can do it using well-accepted physics.

For this to work, the Higgs boson’s accompanying field must be metastable, meaning it can spontaneously settle down into a lower energy state. A bubble of space would then sprout up, with its own physical laws, and expand at the speed of light to destroy everything in its path, including the universe as we know it.

The idea isn’t new, but now that the Higgs has been found, we have a measurement of its mass: about 125 gigaelectronvolts. Carroll and Boddy combined that value with the most recent mass estimate for another elementary particle, the top quark, and calculated that physical laws favour a metastable Higgs over a stable one (arxiv.org/abs/1308.4686).

That sounds promising, but the metastable Higgs looks only a tad more likely. New measurements of the top quark’s mass are expected in 2015, when the Large Hadron Collider switches on after a two-year rest, and they could make a stable Higgs field more likely.

The new data should also help to pin down another unknown. If the Higgs field is metastable and flips into a lower energy state, will the affected regions grow faster than the universe is expanding? If yes, the Higgs field will destroy the universe and the Boltzmann brain paradox is resolved.

Even if not, the field may yet be able to destroy the universe. But whether it will in this scenario can only be resolved via a thorny problem related to the nature of probability in multiple universes. Anyone wanting a swift answer to Boltzmann brains will be hoping we don’t have to go there.

This article appeared in print under the headline “Death by Higgs rids us of cosmic brains”