Hello, and welcome to December's Lost in Space-Time, the physics newsletter that shines a light on the quantum world and is surprised to see it come straight out the other side. Why that's a Thing will be revealed in what follows, as we also look at some of the biggest "why?" questions in the universe, muse about the nature of time and wonder whether, if we're lost in space-time, wormholes could offer a shortcut through it.
Quantum transparency
This might seem an overly candid thing to say in what purports to be a newsletter about fundamental physics, but there’s rarely much particularly new to say.
I should clarify what I mean: there are new questions, questions about questions, hypotheses and theories about the nature of material reality in abundance. There’s even sometimes the odd rumour of a new finding – for example, whether the LHCb experiment at CERN has seen a new particle beyond those predicted by the standard model of particle physics. (As I mentioned in a previous newsletter, I’m a sceptic , but keep tuned on that one – the word on the street is that the collaboration will be releasing an analysis of the latest data very soon, and it might contain some surprises.)
But it’s rare that there’s news of the stamp of: Higgs boson found, gravitational wave discovered, box ticked. Pleasingly, though, this month there was – and while it’s nothing like on the scale of those discoveries, it’s another of those satisfying “theoretical prediction comes good after decades” stories.
It concerns an effect known as Pauli blocking, and you might have seen my colleague Leah Crane’s news story about it. Three groups have now independently demonstrated the existence of the phenomenon, in which gases of atoms collected in a magnetic trap and cooled down almost to absolute zero suddenly become transparent to light.
Blue laser light shone on an atomic trap is used to investigate quantum transparency at JILA, Colorado. Credit: Christian Sanner, Ye labs/JILA
That is quite a party trick, if you attend the sort of parties that have the right cryogenic equipment to hand. That does rather raise the perennial question of what this is good for, to which I give the perennial answer: this is fundamental physics, so we don’t know yet.
On one level, this is just another of the myriad weird states of quantum matter that we know exist at temperatures close to absolute zero, from superfluids to Bose-Einstein condensates. Push it on to another level and, as Leah mentions in her news article, Pauli blocking might help in fulfilling the promise of quantum computing at scale. When a medium becomes transparent, it’s because photons of light are no longer being absorbed by atoms. If you could put the atoms that form the bits of a quantum computer in a Pauli-blocking state, it might be less vulnerable to light-induced disturbances that would otherwise destroy the delicate states on which the computing depends.
That’s all a bit “might” and “would” for the moment – and for me, there are some intriguing fundamental speculations too. Pauli blocking is related to the Pauli exclusion principle, the quantum-mechanical phenomenon by which more than one building block of matter, be it an electron, atom or whatever, can’t exist in the same quantum state. (Both effects are named after Austrian physicist and pioneer of quantum theory Wolfgang Pauli.) By restricting what particles can do, the Pauli exclusion principle provides structure to their interactions and underpins the stability of atoms in the first place.
Pauli blocking occurs when all particles in a system are scrunched up in different quantum states as tightly as they can be, and it’s not a stretch to think that further investigations of the phenomenon might give us some further insights into some of the “whys” about the nature of matter. Just don’t necessarily expect that to generate news anytime soon…
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That “why” put me in mind of the New Scientist news of the month – the magazine turned 65! To celebrate our anniversary – a kind of age of mature wisdom and reflective capability, I like to think – my colleagues and I put together a special features section looking at 13 of the most intriguing “why?” questions surrounding our existence and that of the universe.
I’ve taken it upon myself to highlight a classic feature from the New Scientist archive each month, and the mention of why time only flows one way reminded me of one from 2013, “Saving time: Physics killed it. Do we need it back?” . Without wanting to reveal too much of journalism’s internal processes, the article arose when our then-Australasia correspondent, Mikey Slezak, was visiting London. Far, far too late in his pub welcome night, he revealed to me that his master’s thesis had been on the philosophy of time. It’s a subject on which I can have some very insightful opinions when I am two or more drinks down, and both of us rocked into the office next day with sore heads and an idea for a compelling feature – if only we could remember what it was.
Fortunately, Mikey eventually did. Its starting point is a bald fact intrinsic to Albert Einstein’s theories of relativity – that space and time aren’t absolute, but relative to the observer. That’s mind-bending enough, but you just have to work through the maths a bit further to see that a logical corollary of the relativity of time is that ALL OF TIME MUST EXIST AT ONCE. (Yes, the all-caps is deserved here.)
It’s a picture known as the block universe, and it means relativity kills not just the perception of a one-way flowing time that is essential to our experience of the universe, but the conception of time’s passage as a beating drum that underpins all the rest of physics, quantum theory included.
So, what gives? Trying to solve the mystery of time is fundamental to making progress on unifying general relativity and quantum theory – and no less importantly, in squaring what science tells us about reality with our perception of it. Mikey’s feature is an enjoyable romp through the efforts of physicists, such as Lee Smolin at the Perimeter Institute for Theoretical Physics, and philosophers, such as Craig Callender at the University of California, San Diego, to get a flowing time back (and the fact that no one can agree how).
I just love the quote it ends on, too, written by Einstein in a letter to a family of a recently deceased friend: “Now he has departed from this strange world a little ahead of me. That means nothing. People like us, who believe in physics, know that the distinction between past, present and future is only a stubbornly persistent illusion.” Now there is a strangely beautiful thought.
Wormholes and how to use them
It’s time for me to attempt to answer a reader’s question, as I try to every month. This time, I’m going to tackle two related questions posed in our physics subscriber eventearlier this year: “Do wormholes exist in reality?”, asked by Lise Smith, and “Will humans ever be able to travel through a wormhole?”, from Adam Miron.
For anyone who’s yet to be sucked into these sorts of questions (those who aren’t Star Trek fans, in other words), wormholes – “Einstein-Rosen bridges” to their friends – are distortions in the fabric of the universe that form tunnels that connect bits of space that might be as much as billions of light years from each other the long way around.
First question first: well, no one knows whether wormholes exist, but there’s no reason why they shouldn’t and every reason to believe they might. Wormholes exist as solutions to Einstein’s field equations of general relativity, and there’s kind of a lesson from the past century of physics that things predicted by general relativity tend to exist in reality (see also: holes, black; waves, gravitational). If they do exist, we might be able to use them in the way they are used in Star Trek: as shortcuts between different parts of the universe.
Wormholes might form shortcuts through space-time - if they exist Credit: Shutterstock / Jurik Peter
But would we survive passing through one? Well, recent research seems to give more credence to that idea than you might initially suppose. For a start, in 2019, theorists discovered that quantum effects mean a person-sized wormhole could exist and indeed persist for the whole history of the universe . In 2020, they added the insight that the sort of accelerations we would experience within a wormhole should be eminently survivable – albeit with the massive caveat that if we were to hit anything else, even a photon of light, while passing through at close to the speed of light, we might not survive the collision.
Don’t try this at home, even if you could, in other words. Just as a bonus on the whole wormhole thing, I’d also point out another recent speculation from the intersection of general relativity and quantum theory about what’s known as the ER = EPR equivalence: that tiny wormholes in space-time could be the conduits through which the “spooky action at a distance” of quantum entanglement works, and this could in fact be the thing that stitches the fabric of the universe together. Heady stuff, and if you’re interested, you might consider reading this New Scientistarticle from physics superstar Sean Carroll at California Institute of Technology that explains more.
All you need to know about general relativity
Of which, more news: I mentioned in my last newsletter that I had been hard at work on the latest New Scientist Essential Guide on all things general relativity. It’s called Einstein’s Universe: Relativity and the cosmos it built and I’m pleased to say it’s out now, available in newsagents in the UK and Australia and from the New Scientist Shop wherever you are in the world. Well worth the entry price, but then I would say that. Comes with a free wormhole for every reader (I wish).
also in new scientist
1. I’m personally thrilled that New Scientist’s live events are returning, with a three-day edition of our award-winning festival of science, New Scientist Live, to be held in Manchester, UK, on 29 to 31 January. I'm hosting a stage there, and hope to see you there – but if you can’t make it physically, you can be there virtually, as this time all the talks will be streamed live.
2. I mentioned tests of quantum reality in last month’s newsletter, but if you haven’t, do have a read of this feature that appeared in New Scientist last month about the experiment that could prove reality doesn’t exist…
3. It’s not fundamental physics, but it is fun and I think you’ll like it – I’ve been working with astronomy writer Stuart Clark lately on a feature about how exoplanet discoveries have upended our conceptions of how our own solar system formed. Read it and you may never feel the same about Jupiter again…
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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