Hello, and welcome to September’s Lost in Space-Time, your dispatch covering the small, the large, and everything in between. This month, we delve into the mysteries of quantum theory a century after its most famous dissident was given a prize for helping to invent it, while also looking at a bizarre never-ending state of matter and asking how space can be expanding if it’s not got anything to expand into.
The quantum mystery that keeps on giving
If you haven’t yet seen our special feature on the frontiers of quantum theory, I’d urge you to beg, borrow or steal a copy of the New Scientist magazine issue dated 28 August – or you can exploit the magic of liquid crystals and take a look at it in our app or on the website at any time, of course.
I say nominally because Einstein didn’t actually receive the award until 1922, the Nobel committee having decided to tide it over a year as they were unsure whether any of 1921’s nominees were up to scratch. Oh, the ironies of history, especially when you consider the 1920 prize was awarded to Charles Edouard Guillaume (who he?) “in recognition of the service he has rendered to precision measurements in Physics by his discovery of anomalies in nickel steel alloys”.
Albert Einstein won his Nobel prize for his role in creating a theory he spent most of his career trying to undermine Credit: Glasshouse Images/Alamy
The second irony is that Einstein received the Nobel not for general relativity, his magisterial theory of gravity that he’d completed in 1915 , but for his contribution to developing a theory he spent most of his further career trying to undermine. The photoelectric effect mentioned in his award citation – the emission by some metals of electrons when they are illuminated with light – is arguably where quantum weirdness started.
Max Planck had introduced the idea that energy comes in discrete packets known as quanta in 1900, but that was purely as a mathematical device (another note on the mundanities of history: he was trying to make accurate calculations of the heat radiation from light bulbs to assist the manufacturers of same). In his annus mirabilis of 1905, Einstein made quanta real in his explanation of how the photoelectric effect worked: light doesn’t just come in the form of waves, as most people assumed at the time, but also in the form of discrete particle-like quanta called photons.
As you’ll read in the special, this innovation created “wave-particle duality” - the central mystery of the quantum realm, from which, more or less, all the others flow. As quantum theory was developed as a rigorous mathematical theory during the 1920s, Einstein became convinced that the fuzzy, probabilistic depiction of reality it implied couldn’t be a true picture of reality. In 1935, he made that point explicit in a paper, universally known as the EPR paper, he co-authored with Boris Podolsky and Nathan Rosen, “Can Quantum-Mechanical Description of Physical Reality be Considered Complete?”, where he notoriously introduced the concept of entanglement.
This “spooky action at a distance”, a connection between what we measure about two quantum particles when they are separated in space, embodies the various mysteries of quantum theory today. We’ve got a theory that works in explaining the world – do the mathematics, and it gives you the right answer – but seems to go against everything we think we know about how reality should work, suggesting “telepathic” links between seemingly disconnected bits of the underlying physical world, and also that we have some role in creating the reality we see by measuring it.
One response to that is, why should we care, as long as it works? After all, we’re already building technologies such as quantum computers that exploit these effects, so they are undoubtedly real (although the question of whether quantum computers will actually ever be useful for anything is another frontier question we deal with in the special).
Well, it’s natural curiosity, isn’t it? And we’ve got reasons to believe that quantum theory can’t be the final answer – not least, the way it fails to explain gravity, and is fundamentally incompatible with general relativity. When it comes to the mysteries of quantum theory, even a century after it first blossomed, it’s still a journey, not a destination.
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I’ve made it a regular feature of my newsletter to try to answer questions sent in by readers. This particular one featured in our “Your Physics Questions Answered” live subscriber event in March, but it’s also the subject of a special request from D. Schmidthuber to the Lost in Space-Time inbox. He asks: “The universe is expanding – what is it expanding into? What is the larger construct which allows this to happen?”.
Well, now, that is a very good question – ask me another. That’s my shorthand way of saying you’re not going to get a particularly satisfactory answer out of me, because I don’t know, and I don’t know anyone else who does either.
The first counter-question, however, is whether there has to be (or can be) an answer. When we talk about things expanding, we are using concepts of space and time that are valid within space and time. The universe is all of space and time: what reason do we have to think that concepts intrinsic to it are valid elsewhere – or that indeed there is an elsewhere?
That’s what cosmologists of the stamp of the UK Astronomer Royal Martin Rees mean when they counter the question of what space is expanding to, or what’s outside the universe, with “what’s north of the North Pole?”. North is a construct we’ve invented to make sense of Earth’s surface – when you get to the end of north, that’s it.
That said, many cosmologists do try to look further, perhaps motivated by a general human abhorrence of boundaries. But there’s a limit to how far you can go without descending into metaphysical speculation. Questions of the universe’s expansion are bound up with the question of what it is expanding from – you wind the clock of an expanding, cooling universe like ours back and you logically reach the “singularity” of the big bang, an infinitesimally small state of infinite density and temperature right at the beginning. Our observations of the universe, and the theories we’ve built on top of them, take us back quite close to that point, but they don’t take us all the way there. It’s commonly assumed that the big bang is a point where something happened; in fact, all we know about it is that it is a point where our theories of physics break down.
You’ve got to credit Nobel-prizewinning physicist Frank Wilczek for knowing how to sell an idea – “time crystals” are a concept where the intrigue is already right there in the name.
A brief recap: time crystals are bizarre, oscillating materials that seem to run on a never-ending loop. Like regular solid crystals, which break symmetry in space (move sideways along a solid crystal and the presence of atoms in distinct, repetitive patterns means things look different in different directions), time crystals break symmetry in time.
As far as the quantum computer is concerned, part of its processor getting stuck in an infinite oscillating loop is a failure mode – but it is the most direct indication yet that Wilczek’s brainchild is a real-world thing.
Google researchers claim to have created a deathless "time crystal" inside a processor for its Sycamore quantum computer Credit: Erik Lucero/Google
So what are time crystals themselves good for? Well, probably nothing much in the short term. When we get to the heat death of the universe, however, well, it’s another story entirely. That’s the point where there’s no useful energy left to power non-equilibrium processes of the sort that power stars, life – all the interesting stuff. While the rest of the matter in the universe would be hanging around, sulking, with nothing to do, time crystals would continue happily oscillating away to all eternity.
The idea of something that could outlast the heat death of the universe is pretty cool. There’s even been speculation that, given the right technology (which to be fair we’ve got time to develop), we might upload our own brains to a time crystal, in a sense living on for ever. If you like living on in an eternal loop, that is.
3. Our regular columnist Chanda Prescod-Weinstein’s latest contribution looks at the threats to the night sky from too many satellites overhead– a subject of concern to those concerned with science and the pure beauty of the universe as seen from here.
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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