Hello, and welcome to July’s Lost in Space-Time, your dispatch from the outskirts of fundamental physics with me, Richard Webb, New Scientist executive editor and physics nerd extraordinaire. This month: is the Higgs boson so dull because it’s hiding a secret? Plus, an easier way to catch gravitational waves, whether there’s anyone like us in the future out there, and a question about the quantum brain.
Is the Higgs hiding a secret?
I wasn’t in the best place for the announcement of the discovery of the Higgs boson when it reverberated around the world of physics and beyond almost nine years ago to the day, on 4 July 2012. That would have been in the main auditorium at CERN just outside Geneva, where the breakthrough at the Large Hadron Collider (LHC) was presented. But I’d like to think I was in the second-best place.
Every year, at least in non-covid times, the Lindau Nobel Foundation holds a jamboree at Lindau – just the other end of Switzerland and then some, on the German side of Lake Constance – at which past Nobel prizewinners meet, talk with and hopefully inspire young scientists in their field. In 2012, coincidentally, it was the turn of physics, and I had managed to blag a press invitation.
It meant I was rubbing shoulders for the announcement, live-streamed to the hall, with the likes of Carlo Rubbia. He shared the Nobel prize back in 1984for leading the charge towards CERN’s last breakthrough, the discovery of the W and Z bosons that mediate the weak nuclear force. As head of CERN subsequently in the 1990s, he also played a major part in getting the LHC off the ground.
What impressed me back then was how, when I interviewed him just minutes after, Rubbia was already looking to the future, wondering aloud whether the LHC would be the right machine to tease out all the Higgs’s properties – or whether we would need a bigger, or perhaps just better, “Higgs factory” to do that. (Why not indeed use your moment of triumph to make a pitch for more funding, a cynic might ask. Fortunately, I’m not one.)
If you’ve caught up with a feature in last week’s issue of New Scientist already, you’d know that Rubbia hasn’t got his way – yet – but he was right on the money about how particle physicists would be thinking now, nearly a decade on. We’ve learned a lot about the Higgs from studies at the LHC – principally, that it seems to be deadly dull, conforming in every way so far to the predictions of the “standard model” of particle physics. Regular readers of this newsletter will need no telling that this doesn’t satisfy most people with skin in the game. There’s just too much that the standard model doesn’t tell us for it to be anything approaching the final answer – for example, about how gravity fits into the general picture of physics, or which particles, fields or other phenomena constitute dark matter and dark energy.
Ironically, given the way it was sold by Rubbia and others back in the 1990s, it’s true that the LHC is not necessarily the best instrument for detecting subtle ways the properties of the Higgs may deviate from standard model predictions that might indicate new physics. It collides protons with protons. Protons are themselves composite particles, made up of smaller quarks, so this is a messy business. Even now, the fine details of the interactions between the Higgs and other particles have only been measured to between 10 and 20 per cent precision, leaving plenty of wiggle room for anomalies to be uncovered.
So how do we do that? Well, the LHC will return in a new and boosted form later this year after a two-year upgrade programme. The minimalist hope is that finding new answers is purely a numbers game. The more data you collect, the smaller the statistical uncertainties become and the easier it is to spot deviations from what you expect.
Hopes for a Higgs factory haven’t died. In June 2020, the 23 member states in CERN’s council agreed that to build an electron-positron collider (which produces much cleaner results as the electron and its antiparticle are fundamental particles), should be their priority. But wrangling over where to site such a machine, what form it should take and who should pay for it, is a discussion that’s been ongoing since way before even 2012.
CERN’s own proposal is for a “Future Circular Collider” with a circumference of 100 kilometres, dwarfing the LHC’s 28 kilometres. But technical and financial feasibility studies, which started last year, are only due to be completed in 2027, and the world has a lot of competing spending priorities. The LHC, even though it may not seem so cutting-edge any more, is still the best bet we have for further answers in the foreseeable future.
Attempts to work out the true nature of the Higgs boson could lead to the construction of an accelerator that dwarfs even the Large Hadron Collider in size Credit: CERN/Maximilien Brice
Gravitational waves come of age
The other big physics discovery of the century so far came in 2016, with the announcement by the US collaboration at the Laser Interferometer Gravitational-Wave Observatory (LIGO) of the discovery of gravitational waves, the ripples in space-time predicted by Albert Einstein’s general theory of relativity. In last month’s Lost in Space-Time , I highlighted an arXiv paper about the possibility of discovering primordial black holes created in the big bang through their distinctive gravitational wave signature, and ended by saying that the triumph of gravitational-wave astronomy would be proving it could take us to places that conventional astronomy can’t.
And boy it’s proving it, day by day. Whereas the first two observation periods of LIGO produced 11 detections between them over 400 days, just the first half of the third observation period, O3, where analysis is ongoing, has produced 39 detections from under 200 days. Recently, my colleague Leah Crane reported the latest novelty in that thicket of data: that LIGO and its Italian partner, Virgo, spotted the signal of a black hole devouring a neutron star not just once, but twice within 10 days in January 2020.
This is big stuff, hopefully giving us insights into how black holes, objects so massively dense that not even light can escape their gravity, differ from neutron stars, which are almost that extreme but don’t quite make the grade. Making any conclusions on the basis of conventional light-based astronomy is nigh-on impossible.
So what are the next steps for gravitational wave astronomy? Like with the LHC, it’s kind of more of the same for the moment. An upgraded LIGO will come on stream mid-2022, and there’s still the rest of the data from O3 to come. There are also the plans for hugely expensive future boondoggles – in this case the Laser Interferometer Space Antenna, or LISA, a proposed gravitational wave observatory using satellites in space. A test run, LISA Pathfinder, blasted off in 2015.
But I’ve got my eye on something else. One of the most fascinating, under-reported recent developments (although you read it here in New Scientist) in gravitational waves is their successful detection using radio signals from pulsars. These are very fast spinning neutron stars, and the pulses of unknown origin they send out are the most accurate timekeepers in the wider cosmos. The principle is that their timing is so precise that any intervening distortion in space-time caused by a passing gravitational wave will be detectable through subtle shifts in them.
I wrote about this technique over a decade ago (gulp) when it was just a glint in people’s eyes, with the suggestion that it might beat LIGO to the punch. Well it didn’t, but the first results from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) consortium put out this January suggest they aren’t far behind. Hone the technique, and we may be able to access a rich natural experiment telling us all we want to know about gravitational waves and the processes that make them – relatively cheaply, and without ever even leaving the planet.
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In this paper, cosmologist S. Jay Olson at Boise State University in Idaho and philosopher Toby Ord at the University of Oxford (his book on existential risk, The Precipice, is worth a read, just by the by) build a model involving the maximum speed a technologically advanced civilisation could expand through the universe and the probability of a civilisation reaching a stage of being able to do that, throw in an assumption known as the self-indication assumption – basically, that we as observers are randomly selected from the set of all possible observers – and then do some complicated Bayesian statistics to estimate how us seeing evidence of one such expansionist civilisation, several or none changes our assessment of how likely we ourselves are to reach the expansionist stage.
Following still? Just barely myself. The bottom line as I understand it is to vigorously underline a previous result: that a lack of any evidence of such expansionist civilisations suggests a “late-stage filter” for human-like civilisations. In other words, given the necessity of moving at some point as circumstances in our cosmic neighbourhood change, we are doomed. Ultimately. Probably. Although to be fair, the way we’re going, we may not last that long.
Is the brain quantum?
On that cheery note, it’s time to turn to my monthly attempt at answering a question from the more than 1000 sent in my readers to our “Your Physics Questions Answered” live event in March. This month: does the brain exploit quantum physics?
First level answer: yes. The brain is made of atoms and molecules and neural signals consist of electrons, and all of those things follow the laws of quantum physics. But what people usually mean by the question is whether our neural processing takes advantage of “spooky” features of quantum mechanics such as superposition (things being in multiple places or states and once) and entanglement (the states of things being connected over distance).
Feeling a bit in two minds? That could be down to the quantum influences on the brain Credit: Shutterstock/Lia Koltyrina
There things become a lot more messy, and the conservative answer becomes “no”. All we know about superposition and entanglement from lab experiments indicates they are very delicate phenomena, liable to be destroyed by the slightest outside disturbance – and therefore very unlikely to survive in the wet and warm environment of the brain.
On the other hand, there is a lot we can’t explain about cognition and consciousness (watch out by the way for a New Scientist special issue on consciousness due out this week), and we do have evidence of quantum effects persisting in environments we wouldn’t naively expect, for example in the photosynthetic systems of plants. There have also been suggestions made of specific structures in the brain that might maintain quantum effects for longer times, and so contribute to a quantum form of cognition – notably the longstanding suggestion by physics Nobel laureate Roger Penrose and physician Stuart Hameroff that protein tubes called “microtubules” exhibiting quantum effects might explain consciousness, and a more recent suggestion by physicist Matthew Fisher involving calcium phosphate structures known as Posner molecules, which maintain quantum effects for unusually long times.
It’s fair to say most researchers are sceptical and think that classical concepts will be enough to eventually explain the brain. But given the massive complexities involved in this most complex of organs, it’s only fair to answer this question with “we don’t know”.
also in new scientist
1. Where did the first stars come from? Astrophysicist Emma Chapman takes us way back into the dark ages of the universe’s first billion years in an online talk on 22 July.
2. We always talk about the evolution of the universe in terms of gravity, but we know other forces were at play. What role magnetism might have played right from the beginning is the intriguing subject of a recent magazine feature.
That’s it for now. Thank you for reading! If you have any comments or questions, you can let me know by emailing me at lostinspacetime@newscientist.com and I’ll try to answer them in an upcoming newsletter. If you know someone who might enjoy Lost in Space-Time, please forward it on. If you haven’t yet, you can sign up to get it in your inbox every week here.
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