Tag Archives: quantum-physics

The Large Hadron Collider – A Machine for Asking the Universe Embarrassing Questions

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Quite often on my socials, I see a T-Shirt designed by the ever-so awesome, Jim’ll Paint It, which says on it “Large Hadron Collider. What does it do? No one knows -> WTF? I once saw it in the wild on a night out with mates, and very drunkenly tried to explain it to the wearer who wasn’t in the slightest bit interested in anything a drunk physics nerd had to say. I do that a lot, try and explain things to people after I’ve had a couple of beers, when they don’t actually care and wish the boring person excitedly gesticulating before them would please shut up so they could get on with their night out. Which is one of the reasons I started writing about this stuff here.

Anyway, enough of my reminiscing on great nights out with friends. You don’t want to hear any of that, you’re here to hear all about the LHC.

Somewhere beneath the gentle vineyards and villages that straddle the French-Swiss border, a stream of protons is being whipped around a 27-kilometre underground ring at a whopping 99.9999991% the speed of light. The machine doing this is so cold that parts of it are colder than outer space. It consumes enough electricity to power a small city. It contains magnets so powerful they could tear everyday metal objects across a room. And the entire purpose of this absurdly expensive, ridiculously complicated contraption is to smash tiny particles together and stare very carefully at the wreckage.

Although this sounds less like science and more like the opening chapter of a hard science-fiction novel. It is, in fact, very real. And it is something you have all heard of.

The Large Hadron Collider, or LHC, is arguably the most ambitious scientific instrument humanity has ever built. It is our attempt to reverse-engineer reality itself. If the Universe is a giant cosmic puzzle, the LHC is the world’s most expensive method of throwing the pieces into the air and watching where they land.

In 2012, it succeeded in finding the Higgs boson, the last missing piece of the Standard Model of particle physics. Today it continues searching for dark matter, probing conditions that existed fractions of a second after the Big Bang, and hunting signs that our current understanding of nature is incomplete.

Which, if we’re being honest, once it’s sussed those out, would be the most exciting outcome of all.

But what actually is the LHC? At its simplest, the Large Hadron Collider is a gigantic circular particle accelerator operated by CERN, the European particle physics laboratory. The ring is buried roughly 100 metres underground and stretches for 27 (just over 16.5 miles) kilometres, crossing back and forth underneath France and Switzerland.

But calling it an accelerator is only half the story, as the clue to its true purpose is in the name. It’s a collider.

Many particle accelerators simply speed particles up and fire them at a target. The LHC does something far more dramatic. It accelerates two separate beams of protons in opposite directions around the ring and then deliberately smashes them into each other.

This turns out to be much more efficient. If one moving proton hits a stationary target, much of the energy goes into pushing the target backwards. But if two equally energetic beams collide head-on, almost all of the energy is available to create new particles.

It’s the particle-physics equivalent of two Formula One cars driving into each other at full speed rather than one car hitting a parked vehicle.

Keeping these proton beams under control is astonishingly difficult. Protons naturally want to continue in a straight line, so the LHC uses more than a thousand enormous superconducting magnets to bend them around the circular tunnel.

These magnets are kept very, very cold, and are cooled to about 1.9 Kelvin, which is roughly a very chilly -271°C. And that, folks, is colder than the average temperature of deep space.

The reason for this is simple but weird. Electricity flowing through ordinary wires encounters resistance, producing heat and wasting energy. At extremely low temperatures certain materials become superconductors, allowing electricity to flow without resistance. The LHC’s magnets need immense electric currents to generate the magnetic fields required to steer particles that are moving at nearly light-speed. Without superconductivity, the whole endeavour would be impractical.

OK, I hear you, you get that, but why is the machine so huge?

And that is because making particles faster isn’t simply a matter of pressing a bigger accelerator pedal. The faster a particle goes, the harder it becomes to bend its path. To keep ultra-relativistic protons moving in a circle, you either need stronger magnets or a larger ring, and the LHC uses both.

Let’s take a step by step breakdown and see how it actually works, and  the journey itself begins with something surprisingly ordinary: Hydrogen.

A hydrogen atom consists of one proton orbited by one electron. Scientists strip away the electron, leaving behind a lone proton ready for acceleration, before setting it off on its grand tour of CERN.

First, it enters a linear accelerator before then passing  through a series of progressively larger booster rings. Each stage adds more energy, like pushing a swing higher and higher, until, eventually the proton beam arrives in the LHC itself. Which is where the real fun starts.

The beams circle the ring over 11,000 times per second, accelerating to 99.9999991% of light speed. At these velocities Einstein’s relativity becomes unavoidable. The proton’s speed can barely increase further, so additional energy instead increases its momentum enormously.

The two beams race around in opposite directions until they meet at four major collision points, where  there are some of the most sophisticated scientific instruments ever built waiting for them.

These are ATLAS, CMS, ALICE, and LHCb.

ATLAS and CMS are the giant all-purpose detectors responsible for the Higgs discovery. ALICE specialises in studying quark-gluon plasma. LHCb focuses on subtle differences between matter and antimatter.

When the beams cross, protons collide, which is where many popular descriptions get the story slightly wrong as the point isn’t really to smash particles apart to see what’s inside them. The real goal is to convert energy into entirely new particles.

Einstein’s famous equation, E = mc², tells us that mass and energy are different forms of the same thing. Sufficient collision energy can literally become matter, and as the protons collide, for a fleeting instant, particles that haven’t existed naturally since the early Universe can pop into existence. Most of them survive for merely tiny fractions of a second before decaying into other particles, and the detectors capture these decay products.

Imagine investigators arriving after a firework factory explosion. They never saw the explosion itself. They only have scattered debris, burn marks, smoke patterns and fragments. From that evidence they reconstruct what happened, which is essentially what ATLAS and CMS do, but they do it millions of times every second.

And here’s a neat callback to the quantum measurement problem.

Before detection, quantum mechanics often describes multiple possible outcomes existing in superposition. Once the detector records an actual event, one specific outcome becomes reality’s official entry in the ledger. Every collision is therefore an example of a quantum process producing a definite measurable result. The detectors don’t merely observe the aftermath. They convert quantum possibilities into cold, hard, recorded facts.

No article on CERN or the LHC would be complete without mentioning the big one. The Higgs Boson. If particle physics has a celebrity, the Higgs boson is the most famous by a country mile.

To understand why though, we need to talk about the Higgs field.

According to modern physics, fields exist throughout the Universe. The electromagnetic field exists everywhere. So do the fields associated with electrons and quarks. The Higgs field is another such field. It fills all of space.

Particles moving through it interact with it to differing degrees. Some interact strongly and acquire large masses. Others interact weakly and remain relatively light. An imperfect but useful analogy would be to imagine walking through a crowded room.

A celebrity trying to cross the room gets constantly surrounded and slowed by admirers, whereas a complete unknown person, such as you or I, could walk through almost unhindered.

The Higgs field acts a little like that crowd and the Higgs boson is a ripple in this field, just as a photon is a ripple in the electromagnetic field.

By the late twentieth century the Standard Model had become an astonishingly successful theory. It explained quarks, leptons, gluons, photons, the weak force and an enormous range of experimental results, but there was still one piece missing.

The Higgs.

Without it, the mathematical framework simply didn’t work correctly. The Standard Model was like a jigsaw puzzle with a hole in the middle, and physicists spent decades searching for it.

Multiple generations of accelerators looked for clues, and found…

Nothing.

Then the LHC arrived on the scene, and on the 4th July 2012, CERN announced that the ATLAS and CMS experiments had independently observed a new particle consistent with the long-predicted Higgs boson. The statistical confidence even exceeded the famous five-sigma threshold, meaning the probability of the result being a random fluke was roughly one in several million. After nearly fifty years of theoretical expectation, the particle had finally been found. We had the Higgs Boson.

One of the most memorable images from the announcement was theoretical physicist Peter Higgs sitting quietly in the audience as decades of speculation became experimental reality. A truly remarkable sight, that pulls at the heart strings and to this day still lubricates my tear ducts with the memory. And as the significance of the result became clear, he reportedly wiped away his own tears. Just imagine it. Your life’s theoretical work becoming a fact of science. Wow. Just WOW!

A year later, in 2013, Peter Higgs and François Englert (sadly, Robert Brout had passed away in 2011 and Nobel doesn’t award posthumously), very much deservedly, received the Nobel Prize in Physics.

The discovery was monumental not because it opened a new chapter but because it completed an old one. For the first time, every fundamental particle predicted by the Standard Model had been observed and humanity had found the final missing actor in nature’s best-tested theory.

After such a triumphant discovery, you may be wondering what the LHC did next, and is still doing as I type this article. The Higgs may be the headline act, but it isn’t the whole show, as those clever dudes at CERN have been recreating the early universe.

The ALICE experiment studies something called quark-gluon plasma. Now then, ordinarily quarks are permanently confined inside protons and neutrons. But at the unimaginably high temperatures that existed shortly after the Big Bang, quarks and gluons formed a superheated fluid.

Heavy-ion collisions at the LHC briefly recreate these ancient conditions and for an instant, the Universe is returned to a state it last experienced nearly 14 billion years ago.

As we discussed in the dark matter article, most of the matter in the Universe appears to be invisible, and the LHC is very much hunting for this dark matter. Although it can’t directly see dark matter particles, if collisions create them, they may escape the detector unnoticed, so scientists are searching for the telltale signature of missing energy and momentum. Something leaves the collision carrying energy away, but nothing visible accounts for it. Thus far, no confirmed dark matter particle has emerged, but the search very much continues.

Physicists once hoped the LHC might discover evidence for supersymmetry, often shortened to SUSY. This idea predicts that every known particle has a heavier partner and supersymmetry could help explain dark matter, unify forces and solve various theoretical problems. Indeed, it was one of the most anticipated possibilities before the LHC began operations, and so far it has found…

Nothing.

Which is itself a scientific result. Nature is under no obligation to reward our favourite theories. Sometimes experiments confirm ideas, and sometimes they eliminate them, and both outcomes move science forward.

Then we have the matter-antimatter mystery. The LHCb experiment investigates why the Universe contains far more matter than antimatter. According to current theory, the Big Bang should have created them in nearly equal quantities, yet a Universe made of equal matter and antimatter would mostly have annihilated itself, an eventuality which quite clearly did not happen, and somewhere in the laws of physics, matter gained a slight advantage. LHCb is hunting for clues.

As we look at the bigger picture, the most remarkable thing about the Large Hadron Collider is not that it found the Higgs boson.

It’s that humanity built a 27-kilometre machine colder than outer space, accelerated particles to within a hair’s breadth of light speed, recreated conditions from the first moments after the Big Bang, and then used the resulting subatomic shrapnel to test ideas about the deepest structure of reality. All the Higgs really did was to complete the Standard Model.

But the Standard Model is not the end of the story. It still cannot explain dark matter. It says nothing about dark energy. It does not incorporate gravity. It leaves major questions unanswered. Which, in turn, means the LHC stands in a curious position, as it is both humanity’s triumph and an admission of ignorance.

We built it to answer questions. Instead, it gave us something scientists secretly like even more.

It gave us better questions!

P.S. I’ll do a post about the current upgrades the LHC is getting at the moment when it is up and running again.

ER=EPR: The Equation That Might Explain Everything (Or Nothing)

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Remember a few weeks back when I mentioned Wormholes and ER=EPR? Yes you do, it was in my Hawking Radiation article, I think, or was it… ??  Anyway, doesn’t matter. Wormholes and ER=EPR sit right at the edge of modern physics, and they’re both properly strange on their own. But put them together and things get stranger still. ER=EPR suggests spacetime itself might be built from quantum entanglement. And if that’s true, it could be a genuine clue toward unifying General Relativity and quantum mechanics. The Holy Grail of physics, finally within reach.

Ok, let’s start the whole shebang with wormholes, quantum weirdness, and the possibility that space is made of entanglement. Imagine you’re standing in the middle of an empty field, staring up into the night sky, without a single light around for miles to pollute your view.

As you stare into vastness above, a star on the other side of the Milky Way is so unimaginably far away that even the light, the fastest thing in the universe, has taken tens of thousands of years to reach the Earth.

That, folks, is what Douglas Adams was explaining when he wrote, “Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.”

But what if distance is an illusion? What if the universe has secret shortcuts hidden beneath the surface of reality? And what if those shortcuts are connected to one of the strangest phenomena ever discovered: quantum entanglement?

Welcome, my readers, to the wonderfully bizarre world of wormholes and the mind-bending idea known as ER=EPR, a concept so radical that it suggests space itself might emerge from invisible quantum connections!

For decades, wormholes belonged mostly to science fiction. In Star Trek: Deep Space Nine, a wormhole is the biggest McGuffin that kept the show running through 7 seasons. A cosmic tunnel, allowing Benjamin Sisko et al. to travel from the Alpha to Gamma Quadrant whenever they want. In Stargate SG1, MacGuyver could travel to countless worlds throughout the galaxy. Then in Stargate: Atlantisss… Sorry, got a bit carried away there. Despite all the televisual sci-fi applications and cinematic exaggerations, the actual truth is that wormholes were born not in Hollywood. They came from Einstein’s equations.

Back in 1935, Albert Einstein and Nathan Rosen discovered a curious mathematical feature hidden inside General Relativity. Their equations seemed to allow a bridge linking distant regions of spacetime, which became known as the Einstein-Rosen Bridge (I know I’ve mentioned it before, but it was this that got me into all of this).

There was a catch though in that the bridge wasn’t a practical tunnel as it collapsed too quickly for anything to pass through. You couldn’t fly a spaceship through it. You couldn’t send a message through it. The mathematics allowed its existence, but nature appeared to slam the door shut before anyone could use it.

This didn’t stop physicists thinking about them. How could they? The idea was irresistible! If spacetime can bend under gravity, perhaps it could also fold. Going back to one of my previous analogies, imagine drawing two dots on a sheet of paper. The shortest path is a straight line between them. But if you fold the paper so the dots touch, you’ve created a shortcut. A wormhole is essentially the universe doing something similar with space itself.

Unfortunately, the universe isn’t that eager to cooperate.

Every serious attempt to build a traversable wormhole runs into a major obstacle as the tunnel wants to collapse. To hold it open, physicists believe you’d need something called exotic matter, a substance with negative energy density. That’s not just rare. It’s something we’ve never discovered in the quantities required to prop open a cosmic tunnel, and it is at this point that the story should have ended as an interesting mathematical curiosity.

It didn’t. What it did instead was to become much stranger. And to understand how and why, I need to take you on a detour into the quantum world.

Imagine two particles born together in a special way. Quantum mechanics says they can become entangled, meaning their properties are linked no matter how far apart they travel. Measure one particle and you instantly learn something about the other. As we all know, Einstein absolutely hated the idea, which he famously called “spooky action at a distance.”

The weirdest part is that entanglement has been tested repeatedly and appears to be a genuine feature of reality. Yet despite how strange it seems, it cannot be used to send messages faster than light. The universe somehow preserves Einstein’s speed limit while still allowing these remarkable correlations to exist.

So physicists faced a mystery. Why does entanglement exist? What is happening underneath? For years no one really knew.

Then, in 2013, physicists Juan Maldacena and Leonard Susskind made an outrageous proposal. They suggested that two ideas Einstein helped create in the same year, 1935, might actually be the same thing. One of these papers introduced us to the Einstein-Rosen bridge, while another introduced us to the Einstein-Podolsky-Rosen paradox, and it is this that led to the modern concept of entanglement.

Maldacena and Susskind condensed their shocking idea into these characters:

ER = EPR.

Which in plain English simply means…

A wormhole and quantum entanglement may actually be different descriptions of the same underlying reality!

At first glance, it sounds completely absurd. You’re telling me two entangled particles on opposite sides of the galaxy are connected by a wormhole? Remarkably though, that’s close to the idea. Not a giant science-fiction tunnel. Not a portal for spaceships. Not a shortcut you can travel through. Instead, a tiny, non-traversable geometric connection embedded within spacetime itself.  If you look at it like that, all of a sudden, entanglement doesn’t appear quite so magical, does it?

Instead of imagining particles somehow communicating through empty space, ER=EPR suggests they’re connected in a deeper geometric sense. Space says they’re separated. Reality says they’re linked. And that’s where the rabbit hole becomes truly dizzying.

Physicists began asking a new question.

If entanglement creates connections, could enough entanglement actually create space itself?

This, folks, is one of the hottest ideas in theoretical physics today. Instead of treating space as the stage on which physics happens, some researchers suspect space is more like a fabric woven from quantum entanglement, and if you pull on enough quantum threads, the fabric itself might fall apart.

Think of it as a knitted jumper. From a distance you see a smooth surface, but when you get up close, you can see all the individual threads. Likewise, space may look continuous and seamless because we’re observing it from far away. But zoom in deeply enough and the smooth fabric of reality could be built from an unimaginably vast network of quantum links joining everything together. If that’s true, then what we call distance might not be fundamental.

Two regions of space could appear far apart while secretly being held together by deep patterns of entanglement and the geometry of the universe would emerge from information itself. The more you think about it, the more you realise that it’s an absolutely breathtaking possibility because it suggests that, at the deepest level, reality may be made not of matter or energy, but of information.

This idea has become especially important in black hole research, and all you regular readers know how much I love a black hole! To recap, black holes are where General Relativity and quantum mechanics collide head-on, creating paradoxes that seem impossible to resolve. ER=EPR offers a potential way out by linking black holes, information, and entanglement through hidden wormhole-like connections. While it is far from being proven, many physicists regard it as one of the most promising clues we have toward a theory of quantum gravity.

So where does that leave us? Have wormholes been discovered?

No.

Has ER=EPR been proven?

Not yet.

Can we travel through a wormhole to another galaxy?

Almost certainly not.

Yet even as speculation, the idea is extraordinary. A century after Einstein revolutionised our understanding of space and time, physicists are beginning to suspect that space and time themselves may not be fundamental at all. The universe may be more like a vast quantum web, with wormholes and entanglement representing different ways of viewing the same hidden structure.

In that picture, the deepest secret of reality is not matter, nor is it energy, it’s not even space!

What it is, is the invisible information-theoretic connections that bind everything together, stitching the cosmos into the seamless universe we experience every day.

Where Is It? What Is It? Why Can’t We See It? Dark Matter & Dark Energy Explained (Well, Sort Of).

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And just like that, another Friday has appeared from nowhere. This week folks, I’m going to do a bit of a follow up on last week’s article. If the measurement problem is the biggest mystery in quantum physics, then Dark Matter and Dark Energy are the biggest mysteries in cosmology. Together they make up about 95% of the Universe, yet we still do not know exactly what either of them is. Ordinary matter, meaning stars, planets, gas, dust, trees, people and everything you’ve ever touched, accounts for only about 5% of the cosmos. Dark Matter contributes roughly 27%, while Dark Energy contributes roughly 68%.

So, are you ready? Hang on to your hats, it’s time for us to dive into another rabbit hole of truly cosmic proportions!

And we’ll start with a universe that really doesn’t add up, and as is obligatory, an analogy. Imagine you’re sat staring out of a window watching leaves swirling around in a strong wind. You can’t see the wind itself, but you know it’s there because of what it does to the leaves, and Dark Matter and Dark Energy are similar. We don’t directly see them, however, we infer their existence because of their effects on things we can observe. But that’s where the similarities end, as where Dark Matter pulls, Dark Energy pushes. One helps gravity hold the Universe together, while the other seems to be trying it’s very best to tear it apart.

The story begins in the 1930s, when Dark Matter was discovered. Swiss astronomer Fritz Zwicky was studying the Coma Cluster, a truly huge collection of galaxies, within the constellation Coma Berenices. He calculated how much visible matter the cluster contained and compared it to how fast the galaxies were moving. The numbers didn’t make sense. The galaxies were moving so fast that the cluster should have flown apart long ago as there wasn’t enough visible mass to provide the necessary gravitational glue. He proposed there must be a large amount of invisible matter. He called it dunkle Materie or “Dark Matter.”

At the time, and for many years after, most astronomers ignored the idea, until Vera Rubin discovered something even stranger in the 1970s. Galaxies had a rotation problem.

According to Newtonian gravity, stars near the centre of a galaxy should orbit quickly, and stars far from the centre should orbit more slowly, and this is exactly what happens in our Solar System. Mercury, which is very close to the sun, races around it, while Neptune, which is nearly three billion miles from the sun, crawls along in its distant orbit. But galaxies simply appeared to be refusing to obey these rules.

Rubin found that stars far from galactic centres were moving almost as fast as stars much closer in. It was as if galaxies were embedded in enormous invisible halos containing far more mass than all their stars combined, and this discovery became one of the strongest pieces of evidence for Dark Matter.

Which leads us to the question of how do we actually know Dark Matter exists?

And to answer this question, scientists actually have several independent lines of evidence. The first of which is that galaxy rotation actually curves (let me know if I’m overusing the word actually, as somebody actually pointed out to me, I actually do. Apparently). Stars move too quickly to be held by visible matter alone. Secondly, galaxies gather in clusters, which remain gravitationally bound despite insufficient signs of visible mass. Thirdly we have gravitational lensing, something else I’ve touched upon in previous articles. Einstein’s General Relativity says mass bends spacetime, that is, when light passes a massive object, it bends. Astronomers observe lensing effects that require far more mass than visible matter can supply, and it is this that allows scientists to map Dark Matter distribution directly. And lastly, we have the Cosmic Web, which shows us that on the largest scales, galaxies form immense filaments and clusters. Additionally, computer simulations can only reproduce the Universe we actually observe when large amounts of Dark Matter are included.

So, what is Dark Matter? And just like last week with the Measurement Problem, the honest answer is…

…Nobody knows.

There are some things we do know though, and they are that Dark Matter has mass, produces gravity, does not emit light, does not reflect light, and barely interacts with ordinary matter.

So, in a sense, Dark Matter is almost ghost-like as it can pass through ordinary matter seemingly without notice.

Right now, there are several ideas competing with each other as to why, and for decades the favourite candidate was WIMPs.

“WIMPs” are Weakly Interacting Massive Particles, and huge underground detectors have been searching for them, and so far, as tends to happen with the science of the cosmos, nothing definitive has turned up.

We also have Axions, which are extremely teeny-weeny hypothetical particles, and although they are hypothetical, axions remain a popular possibility with scientists. As do sterile neutrinos, which are a heavier cousin of familiar neutrinos that barely interact with anything. Or it could be something completely different and far stranger than our current theories. All we know for sure is that we don’t know what it is, and at present, Dark Matter remains unidentified.

There are some other ideas out there, some of which are pretty wild. Could gravity and everything we know and understand about it be wrong? What If Dark Matter doesn’t exist at all? Maybe gravity behaves differently on enormous cosmic scales?

The best-known attempt at describing this is another scientific theory known as MOND, which stands for Modified Newtonian Dynamics. (another article for later, methinks). And although MOND can explain some weird galactic behaviour, it is Dark Matter that generally provides a better explanation across many observations, including galaxy clusters and cosmological measurements. And this is why most cosmologists therefore regard Dark Matter as the leading explanation.

OK, if Dark Matter is pretty weird, Dark Energy is downright bizarre, and its discovery completely shocked the scientific community, as for most of the twentieth century, astronomers assumed gravity would gradually slow the Universe’s expansion. Which when you think about gravity seems obvious. Gravity attracts. Everything should slowly pull everything else back together. Right?

Well, unfortunately not. Back in the late 1990s, astronomers measured distant exploding stars called Type Ia supernovae and the result was astonishing, and it showed us that the Universe wasn’t slowing down. It was accelerating.  Some mysterious phenomenon was overcoming gravity on the largest scales, and that phenomenon became known as Dark Energy. Cool, yeah!

That leads us to the next obvious question, what exactly does Dark Energy do? And, you’ve guessed it, it’s analogy time!

Imagine throwing a ball upward and now imagine the ball speeds up instead of slowing down, and that is essentially what the Universe is doing, as galaxies, on average, are becoming separated faster and faster over time, and Dark Energy appears responsible for that acceleration.

So, that sort of answers what it does, but what actually is Dark Energy? And you’ve guessed it…

… Nobody knows.

Although several possibilities do indeed exist.

It could be vacuum energy, where empty space may not be empty, as quantum physics says that even a perfect vacuum is seething with fluctuating energy. And Einstein’s equations permit vacuum energy to act as a repulsive force.

This explanation is currently the leading candidate, but, as always when the teeny tiny stuff becomes involved, there is a problem. Theoretical calculations predict vastly more vacuum energy than astronomers observe. This mismatch is one of the largest known discrepancies in physics.

Then we have Einstein’s cosmological constant. He added a term, Λ (Lambda), to General Relativity, and many cosmologists today model Dark Energy as this cosmological constant as it behaves like a fixed energy density which is present throughout space.

Perhaps Dark Energy is a dynamic field that evolves with time, and unlike a cosmological constant, it could strengthen or weaken as the Universe ages.

At this time, however, there is no evidence that currently favours this idea over simpler models.

That’s not all. As dark as this is, there are even stranger things afoot. Dark Matter becomes diluted as the Universe expands, and Dark Energy apparently doesn’t.  As space grows, more space contains more Dark Energy, meaning that Dark Energy ultimately dominates the Universe’s future evolution.

So, with all that conflict, confusion and unknowns, what does all this actually mean for the future?

Well, we know that current observations suggest that the Universe will continue expanding, as expansion continues accelerating, distant galaxies will drift beyond visibility, and the cosmos will ultimately grow increasingly dark and cold, leading to what is known as the Heat Death or Big Freeze (pretty sure I’ve mentioned this in a previous article), trillions upon trillions of years from now, stars will eventually burn out and galaxies will grow isolated in an immense ever expanding darkness.

So why can’t we see Dark Matter and Dark Energy? The answer is actually quite simple as they don’t interact with light. No absorbing it, no emitting it, no reflecting it, nothing for a telescope to actually catch. We only know they’re there because of what they do to everything around them.

And what they do couldn’t be more different. Dark Matter shapes galaxies and galaxy clusters from the inside, holding cosmic structure together like an invisible scaffold. Dark Energy, on the other hand, barely registers on local scales at all. Our solar system, our galaxy, even our galactic neighbourhood, are all gravitationally bound tightly enough that it can’t get a grip. It only shows its hand once you zoom out to the vast, mostly empty stretches between galaxies, and that is where it dominates completely.

There is a search going on as I write this as modern observatories are attempting to solve these mysteries. One of the most important is the European Space Agency’s Euclid mission, launched in 2023. It is creating a massive three-dimensional map of billions of galaxies to investigate the nature of Dark Matter and Dark Energy and how cosmic structure evolved over time. And alongside Euclid, projects such as the Vera Rubin Observatory, James Webb Space Telescope, and the upcoming Nancy Grace Roman Space Telescope are expected to provide unprecedented data.

There is quite an astonishing bottom line to all this, as the most remarkable fact is not that Dark Matter and Dark Energy are mysterious, it’s that everything familiar is the exception, not the rule. All stars. All planets. All oceans. All people. Every great civilisation. Every work of art. Every living thing that has ever existed! Together all that and more only makes up about 5% of reality. The remaining 95% of the Universe consists of things we can detect only indirectly and do not yet fully understand. So, in other words, humanity has become extraordinarily good at studying the cosmos, only to discover that most of it is still hidden from view. And that, folks, may turn out to be one of the greatest scientific surprises of all time!

The Block Universe: Is Time an Illusion? And Lunchtime Doubly So?

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A change of pace this week folks, let’s take a look at one of the more far-out theories that has come from Einstein’s theories. Have you ever woken up in the morning and wondered what actually happened to yesterday? Not what happened yesterday, but what happened to it now that it is over and in the past. If you haven’t, take a moment now and consider a simple question: Where is yesterday? Where did it go?

To the majority of us, the answer is instinctively simple. It has gone, it’s over, yesterday has vanished into the past, tomorrow has not yet arrived, and only the present moment is real, what we are doing in the now exists. This is a view that is so deeply woven into human experience that it feels beyond dispute. That there is no other way to answer that question. But, there is another theory, and it is one of the most intriguing ideas to emerge from modern physics, and this theory suggests that intuition may be wrong.

According to the Block Universe Theory, also known as Eternalism, the past has not  actually disappeared, the future is not awaiting creation, and the present is not uniquely real. Instead, all moments in time, every heartbeat, every supernova, every historical event, and every future conversation, exist together within that vast four-dimensional structure we know as spacetime. If this is true, the universe is not a story being written as it expands and events unfold naturally. In actuality, it is a completed manuscript.

To understand the Block Universe, imagine a DVD containing your favourite movie. On that DVD, every scene exists simultaneously, the opening scene, the climax, and the ending are all physically present and the characters experience events in sequence, but the entire film already exists. Supporters of the Block Universe argue that reality may be similar. Rather than viewing reality as a three-dimensional universe moving through time, physicists describe the universe as a four-dimensional spacetime, where time is treated as another dimension alongside length, width, and height. In this picture, your birth exists, your current moment exists, and your future exists, all these events occupying different locations within spacetime itself, and the sensation time is flowing may simply be the way our consciousness experiences moving through this structure.

Now then, a common misconception is that the Block Universe somehow contradicts Einstein’s theories, whereas in reality, many physicists believe the idea arises naturally from relativity.

This is a principle known as the relativity of simultaneity. I’ve mentioned this in my Special Relativity article remember? It’s the throwing the ball on the moving train analogy. This is the core concept from that theory that states that whether two separate events happen at the same time depends on the observer’s point of view, that is, two events that look simultaneous to one person can happen at different times for another person in motion. Einstein’s Special Relativity shows that observers moving relative to one another can disagree about which distant events are occurring “right now.” There is no universal cosmic clock that defines a single objective present for the entire universe.

Let’s consider two observers moving differently through space. Now then, where one observer may regard two distant events as simultaneous, another observer may calculate that one event happened earlier than the other. Neither perspective is privileged as both are permitted by the laws of physics. However, this then creates a profound problem for the everyday notion of “the present.” If there is no universally agreed-upon present moment, then what exactly separates the real present from the unreal future?

Many philosophers and physicists argue that the simplest answer to this conundrum is that all moments exist equally, and that the distinction between past, present, and future becomes a matter of perspective rather than the fundamental reality.

Einstein himself famously remarked that the distinction between past, present, and future is “a stubbornly persistent illusion,” a statement often associated with block theory enthusiasts as  an interpretation of spacetime. Importantly, though, Einstein’s equations do not explicitly state that the Block Universe is true. Rather, they describe spacetime in a way that many researchers believe is compatible with, and perhaps even suggestive of, a block-like reality

Now it’s time for the pesky teeny tiny stuff to make its appearance as quantum mechanics makes its entry, and as friendly as relativity may appear to the Block Universe, quantum mechanics brings with it complications. 

Quantum theory describes a world fundamentally different from the clockwork universe envisioned by classical physics. We know, from my two-parter, that particles can exist in superpositions of states, where outcomes often appear probabilistic rather than predetermined. Entangled particles exhibit correlations that seem astonishingly non-local. With this in mind, quantum mechanics appears to threaten the entire Block Universe concept.

If the future already exists, how can quantum events be genuinely uncertain? And the answer to that question depends on which interpretation of quantum mechanics you adopt.

First off, we have the deterministic view, and that is that some interpretations, such as the Many-Worlds Interpretation, preserve a deterministic mathematical evolution of the quantum wave function. In these interpretations, reality may still be represented as a vast block-like structure, although it is one that is far stranger than originally imagined.

Next, we have the indeterministic view, which is that other interpretations treat quantum events as involving genuine randomness. Here the future may not be completely fixed until measurements occur, and some physicists see this as direct evidence against a fully formed Block Universe.

And finally, we have the current situation, which is that in actuality, there is no consensus as modern physics has not yet produced a universally accepted synthesis of quantum mechanics and general relativity. It is because of this that the relationship between quantum theory and the Block Universe remains an active area of investigation rather than a settled question.

So, in short, quantum mechanics does not definitively rule out the Block Universe, but it doesn’t conclusively prove it, either.

That leads us on to the problem of free will, and no consequence of the Block Universe generates more debate than its apparent attack on free will. If your future already exists, are your choices truly choices?

Let’s suppose that somewhere within the four-dimensional structure of spacetime there already exists a future version of you deciding whether to accept a job, move cities, or buy that really fast car you want.

Has this decision already been made? If you think about it, at first glance, the answer appears somewhat disturbing, and many critics argue that a Block Universe implies a fixed future and therefore eliminates genuine freedom. That is, if every event is already part of spacetime, then the sensation of choosing may merely be an experience within the block.

However, defenders of free will offer several responses.

Compatibilists argue that free will does not require the future to be open as a decision can still be free if it arises from your values, beliefs, reasoning, and desires, even if that decision is a permanent feature of spacetime. In this view, your future choice exists, but it is still your choice.

Another argument arises from the observer’s perspective. This is because while the future may exist, you don’t have access to it. From within time, uncertainty remains unavoidable, and you deliberate, and evaluate options, and make decisions exactly as before. The difference here is that the existence of future events in spacetime would not grant anyone knowledge of them.

Then we have the libertarian objections. Philosophers who believe genuine free will requires alternative possibilities often reject the Block Universe entirely. They argue that a future that already exists cannot be meaningfully changed and therefore cannot accommodate true freedom.

And like many of these conflicting theories, the debate remains very much unresolved.

One reason the Block Universe fascinates both scientists and science-fiction writers (I have just completed a novel using this very theory as the premise) is that it appears naturally compatible with some forms of time travel. If all moments exist, then travelling to another time may be conceptually similar to travelling to another place. And that is an excellent tool for writing into fiction as General Relativity contains solutions to Einstein’s equations that permit unusual spacetime geometries. Although whether such structures could exist physically obviously remains, like most things in this field, uncertain. That said, the Block Universe does not automatically enable time travel, but it provides a conceptual framework in which the idea becomes easier to imagine.

The Block Universe is not merely a theory about clocks and calendars. It is a new view of reality, as it challenges some of humanity’s most fundamental assumptions. Is time really flowing? Does the future already exist? Is consciousness responsible for our experience of temporal passage? Can free will survive in a universe where every moment is equally real? How does quantum uncertainty fit into the picture?

And once again, my faithful few, more than a century after Einstein revolutionised our understanding of space and time, these questions remain very much unanswered.

Perhaps time truly flows, and the future has yet to be written. Or perhaps, at this very moment, every chapter of your life already exists within an immense four-dimensional cosmic structure, not waiting to happen, but simply waiting to be experienced.

Five Things That Sound Completely Made Up (But Are Annoyingly Real)

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Following on from last Friday’s article, one of the side effects of learning about Hawking radiation is discovering that modern physics is less a collection of facts and more a collection of increasingly unsettling revelations. Every time you think you’ve found the weirdest thing in the universe, physics quietly says, “Hold my equations.”

Here are five examples.

1. Right now, you are hotter than a black hole.

Let’s begin with an insult to black holes. And that is that right now you are hotter than most, if not maybe all, the black holes in the universe

Despite their reputation as the ultimate cosmic monsters, most black holes are astonishingly cold. Hawking showed us that black holes possess a temperature, and the larger the black hole, the colder it becomes. Therefore, a black hole with roughly the mass of our Sun would have a Hawking temperature of only a tiny fraction of a degree above absolute zero.

Meanwhile, you are sitting there at around 310 Kelvin (37°C), radiating infrared energy into your surroundings like a particularly self-satisfied space heater. So, thermally speaking, you’re absolutely thrashing a stellar-mass black hole. That is the same object capable of swallowing stars is, from a temperature perspective, a pathetic overachiever. The universe’s most feared gravitational predator is colder than deep space and vastly colder than the cup of tea that is slowly cooling beside me.

Hawking radiation revealed that black holes aren’t just gravitational objects. They’re thermodynamic objects. And thermodynamics has a wonderful habit of humiliating our intuitions.

2. Space ain’t empty.

The phrase “empty space” is one of the most misleading expressions in science. You got it, empty space is most definitely not empty.

What looks like nothing is actually a restless sea of quantum fields. According to quantum field theory, even a perfect vacuum contains fluctuations, tiny disturbances that constantly appear and disappear throughout space. This isn’t a rare occurrence, it’s happening everywhere, right now, around you, and, amazingly, it’s happening inside you! Between every atom in your body! Creepy and weird or what!!

In fact, Hawking radiation exists because black holes interact with these quantum fluctuations near their event horizons, and without the vacuum’s constant activity, Hawking’s discovery wouldn’t work. Which brings us back to that unsettling conclusion that nature doesn’t seem particularly fond of “nothing.”

Give the universe an empty stage, it’s competing with the best improv stand-up comedians. It immediately starts improvising itself!

3. Black holes ain’t that heavy.

If black holes are gravity taken to the extreme, neutron stars are gravity’s terrifying warm-up act. A teaspoon of neutron star material would weigh around a billion tonnes

Now then. A neutron star forms when a massive star dies and its core collapses so completely that atoms themselves are crushed. Electrons and protons merge into neutrons and produce an object roughly the size of a city but containing more mass than our Sun.

The result of this is density on a scale that defies common sense. A single teaspoon of neutron star material would weigh roughly a billion tonnes. That’s not a billion kilograms. That’s a billion tonnes. The sort of weight that makes the phrase “pick it up carefully” somewhat academic.

If you somehow brought that teaspoon to Earth, it wouldn’t politely sit on a kitchen counter and reality would very quickly become an SEP (you know what that is, you’ve read the Hitchhikers Guide to the Galaxy, it’s when Ford and Arthur arrive at lords on a battered sofa at the beginning of Life, the Universe, and Everything, Ford, clocking Slartibartfast’s ship out of the corner of his eye has to explain to Arthur there’s an SEP over there, try and catch it unawares by glimpsing it from the corner of your eye). Somebody else’s problem.

And at this point, every Futurama fan is now thinking exactly the same thing. “Wait… isn’t this basically Nibbler?” To which science’s answer is both inconvenient and hilarious, and the answer is, “yeah, sort of.”

Nibbler’s species, the Nibblonians, are famously absurdly dense. In one episode, Nibbler casually produces poo that weighs thousands of pounds, despite  Nibbler himself being roughly the size of an enthusiastic housecat. For once, science fiction wasn’t completely making things up. A neutron star packs so much mass into such a tiny volume that a teaspoonful would weigh about a billion tonnes. Compared to that, Nibbler is practically watching his figure.

Somewhere in the universe, one suspects Nibbler is looking at a neutron star, nodding approvingly, and muttering, “Hmm… at last… a sensible-sized snack.”

Physics occasionally likes to remind us that density can be every bit as terrifying as size. And occasionally, it reminds us that Futurama was alarmingly well-informed.

4. Whatever is out there in the blackness, we can’t see it.

If Hawking radiation teaches humility, dark matter delivers the knockout punch. And that is most of the universe appears to be made up of something we can’t actually see.

For centuries we assumed that stars, planets, gas clouds and galaxies were the universe. Then astronomers started measuring how galaxies rotate, and the numbers didn’t add up.

Galaxies should have flown apart. But, instead, something invisible appeared to be providing extra gravity and holding everything together. Astronomers now call this missing ingredient dark matter.

And here’s one of those questions, you, my lovely readers, like to ask. What is dark matter?

The awkward answer is we still have absolutely no idea what it is. What we can infer is its existence from its gravitational effects. That is, we see the way it influences galaxies and bends light, but direct detection remains elusive. The evidence, however, says something is there. We just don’t know what.

Imagine discovering that most of your house consists of invisible rooms nobody can enter. That’s roughly where modern cosmology currently stands with dark matter.

5. What the hell is light doing?

And finally, quantum mechanics saves its strangest trick for last, and that is reality refuses to make up its mind until you look.

This is one of my favourites, and you can easily amaze your family and friends with it. This is the famous double-slit experiment, and it works like this.

If you fire particles through two narrow openings and don’t measure which slit they pass through, the resulting pattern suggests each particle behaves as if it travelled through both slits simultaneously.

Measure which slit it used and the pattern changes completely and the wave-like behaviour disappears and suddenly the particle acts as though it picked a side all along.

This doesn’t mean consciousness magically creates reality, despite what countless internet memes may suggest. What it does mean is observation and measurement play an extraordinarily deep role in quantum mechanics.

The universe, at its most fundamental level, appears less interested in giving definite answers than we would like, and it behaves more like a collection of probabilities than a collection of certainties.

Which is either fascinating or deeply irritating, depending on how much sleep you’ve had.

As I said, you can amaze your friends with this one, and I first saw this demonstrated in a physics class in high school many, many moons ago. All you need is a laser pointer and a couple of perfectly parallel holes in a piece of cardboard. Copy and paste this into google and it will show you how:

Can you do your own double slit experiment with cardboard and a laser pointer?

Let’s link these all together.

At first glance, these facts seem unrelated.  One is about black holes. One is about empty space. One is about neutron stars. One is about dark matter. One is about quantum mechanics.

But they all point toward the same uncomfortable conclusion. Reality is under no obligation whatsoever to resemble common sense.

Black holes glow. Nothingness isn’t empty. Matter can become unimaginably dense. Most of the universe appears invisible. And particles sometimes behave as if they’ve forgotten how choosing works.

Hawking radiation sits right in the middle of this collection of cosmic absurdities. It exists because gravity, quantum mechanics, thermodynamics, and information theory all collide at the edge of a black hole.

And every time physicists dig deeper into that collision, the universe responds with another fact that sounds fake, isn’t fake, and somehow makes everything even stranger.

I tell ya. You simply cannot win with Physics. Sort one thing out and it throws a spanner in the works.

Some of you asked: “How Do You Know So Much?” And honestly? Obsession, mostly. And I won’t shut up.

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Hi folks, quick interim post.

A few of you have been asking how I know so much about this stuff and how I write my articles. So, I thought I’d give you a little insight.

Truth is, I don’t know everything, obviously no one does, and although I’m not a professional physicist, I am a very well-read and well-studied amateur.

I got into it via my father, whose interest started with radio propagation when he was in the RAF. He was always fascinated with physics and space travel, planetary science, and in particular, anything to do with the possibilities of FTL communications.

In 1996 I bought my first tiny house in a small market town a few miles south of Norwich, and my dad lived around the corner. At the time I was working shifts in a factory, a week of days a week of nights, then I would get a week off.

During this time and for most of the rest of the nineties, my dad was always over and making use of my computer knowledge and internet and he introduced me to sites, such as Warp Drive When, and Breakthrough Propulsion Physics and other fun stuff. And it wasn’t long before I was hooked, and within a couple of years my knowledge had far surpassed my father’s.

I’m a serial learner, once I get my teeth into a subject I don’t stop. It’s an obsessive trait I’ve had all my life, and only in recent years have I discovered it’s due to OCD/ADHD/Autism. Every one of us is on the spectrum somewhere, for me and my particular place on it, it has turned me into a compulsive seeker of knowledge.

As for the articles themselves, I bang out a rough draft of what I know on the subject matter I have chosen, and then I do my research. I know quite a lot of useless stuff, how it works, when it was first performed etc.  Once my draft is complete, I then start the research to make sure I’ve got the science correct, haven’t missed anything, and check timelines and people etc. I have a ton of books on the subjects I write about, and I have also subscribed to several scientific journals over the years and have those, Nature, Science, JBIS and a few others. And of course, I have the internet.

With the Quantum Teleportation article, I remember the experiments and I remember the time, and as I said in my article, I was genuinely so excited at the time I wouldn’t shut up about it. As I said above, once the draft is written, I then google it to make sure I’ve got all the awesome dudes who participated, as readers can be ruthless if I make a mistake, miss someone out, or get something wrong.

I then do a second phase over the whole thing and rewrite it before I re-read it out loud to myself, as this is the best way to pick up errors in the narration, typos, dodgy grammar etc.

Once I’m satisfied with it, I send the final draft to some very old friends from school, get them to read it and to see if it makes sense to them. With their feedback, I tweak the final article and it’s ready to go. This is also why some typos and wrong words still get through occasionally.

And that’s it. Physics is a subject that I love, and I love it so much, I want to share it with everybody else, so they will love it too.

When I resurrected this WordPress site after a four-year hiatus, I wanted to write about general sciency stuff. A bit of physics here, a bit of astronomy there, and a bit of paleoanthropology (my first love, don’t get me started on it, honestly, I won’t shut up for days!) in between.

As physics has consumed most of my adult life though, that is the direction my writings have naturally taken, and going forward, apart from the odd article in the other sections from time to time, physics is where it looks like it’s staying.

One last thing before you go. I love receiving your messages, and I have to admit I was a bit overwhelmed at how engaged some of you guys are, flattered at how many new readers are joining, and I’m genuinely thrilled at the messages I have received. Mostly via social media, which is why I added the email address to the home page.

If you want to get in touch to suggest future articles, point out mistakes, or even have a go (I’ve had a couple of those), please do. At present I am able to reply to everyone who gets in touch, unless they’re a complete arsehole.

Thank you for your time. You are AWESOME!

Mal
hello@malandally.co.uk

The Black Hole Glow: A Journey into Hawking Radiation

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Howdy my loyal readers. I’d like to start my saying thank you for the messages I’ve received asking if there is anything else they should know about black holes, and as they are a common theme through most of my articles, I’m going to indulge you with this one, on how Stephen Hawking discovered that the darkest objects in the universe may slowly evaporate away

By any reasonable definition, black holes should be simple. They pull things in. Nothing gets out. End of story. Yet in 1974, Stephen Hawking discovered something astonishing, and that was, black holes are not completely black. Given enough time, they glow, lose mass, shrink, and may eventually disappear altogether. That prediction is now known as Hawking radiation and remains one of the most profound (you’ve heard my ear worm already) insights in the history of physics.

This was a problem nobody expected, although I’m pretty sure Stephen Hawking had an inkling. You see, Black holes emerge naturally from Einstein’s theory of General Relativity. According to the classical picture, they are regions of space where gravity becomes so powerful that nothing, not even light, can escape once it crosses the event horizon. I know, I know, this is old news to you guys, I’ve stated it several times in previous articles.

For decades, physicists assumed black holes could only grow. Matter falls in. Energy falls in. Nothing comes out. Yeah? Then along came Stephen Hawking, and he combined Einstein’s gravity with quantum mechanics and arrived at an answer nobody could have anticipated. Black holes should emit a faint thermal glow. And this implication was extraordinary. Simply put, it meant that Black Holes could die.

As humoungously massive as it is, the Universe is never truly empty, and to understand Hawking radiation, we need to start with a strange feature of quantum mechanics, and that is what appears to be empty space isn’t actually empty.

According to quantum field theory, the vacuum of space is filled with fluctuating quantum fields. That is, teeny tiny disturbances constantly occur throughout space, causing particle-like excitations to briefly appear and disappear. Something that physicists call vacuum fluctuations.

OK. This bizarre activity actually happens everywhere in the universe, and this includes some of the most extreme environments surrounding a black hole.

And this takes us to the famous story that everyone learns. And that is, the most common explanation of Hawking radiation goes something like this:

Near the event horizon, a particle and antiparticle appear as a pair. Now then, normally they would immediately annihilate each other, but if the pair forms close enough to the event horizon, gravity can separate them before they reunite. Which means, one particle escapes into space, while the other one falls back into the black hole. To a distant observer, the escaping particle looks like radiation emitted by the black hole itself.

And this is because, the particle that falls inward, effectively carries negative energy relative to faraway observers, thus reducing the black hole’s mass, so over immense stretches of time the black hole slowly evaporates.

It is an absolutely, beautiful explanation.

But, and there’s always a but, you know this by know, surely guys, there’s one problem.

This isn’t really how Hawking derived the result.

To look at the deeper truth, among physicists, this particle-pair story is considered a useful mental picture, but is not the actual mathematics (maths again, I know. Regular readers already know my issue with maths). Anyway, Hawking’s original calculation used quantum field theory in curved spacetime. And that is, the essential idea is subtle. Different observers can disagree about what counts as empty space. A vacuum for one observer may appear to contain particles to another observer. But, near a black hole’s event horizon, spacetime is distorted so severely that these differing perspectives become physically important

When Hawking compared the state of quantum fields before and after a black hole forms, he discovered that an observer far away would detect radiation emerging from the black hole. So, in other words, Hawking radiation is less about particles popping out of nowhere, and more about the deep relationship between quantum fields, spacetime, and observation itself.

One of Hawking’s greatest discoveries was that black holes possess temperature, and the temperature of a black hole is inversely proportional to its mass, so the heavier the black hole, the colder it becomes, and this leads to a surprising consequence.

A supermassive black hole containing millions or billions of solar masses is incredibly cold, and a tiny black hole is extraordinarily hot, and this relationship means, small black holes radiate far more efficiently than large ones.

Because Hawking radiation carries energy away, the black hole loses mass, and this results in the slow death of a black hole.

As it shrinks, something curious happens. The black hole gets smaller as its temperature rises, then radiation increases which causes the mass to decrease even faster, and therefore the process accelerates.

If the theory is correct, then the final phase could end up with an enormous burst of energy, however, what exactly happens during those final moments remains unknown.

If you got the time to watch one, don’t expect to watch one evaporate as the evaporation process is incredibly slow. A black hole with roughly the mass of our Sun would survive for approximately 10⁶⁷ years, and this is one hell of a lot of zeros, and an incredibly long time. Trillions upon trillions upon trillions of times longer than the current age of the universe. Told you it was a long time.

And what’s more, supermassive black holes live even longer! Fortunately for the universe, black hole death is not an urgent problem, and nothing to worry about. Not for a verrrrrry longtime, at least!

Before Hawking’s discovery, physicist Jacob Bekenstein, argued that black holes should possess entropy, a measure of information content (remember my last article? You did read it, didn’t you?), and Hawking’s calculations confirmed this. In fact, black holes possess staggering amounts of entropy. Even more surprisingly, that entropy scales with the surface area of the event horizon rather than the black hole’s volume!

This observation helped inspire one of the deepest concepts in modern theoretical physics, and that is the Holographic Principle (you know this, I mentioned it way back in my original Black Hole article). This principle suggests that information contained within a region of space may be fully encoded on its boundary surface. It may sound like science fiction, but it has become one of the central ideas in attempts to understand quantum gravity

There’s a problem though, and that is the Information Paradox, and that is the question that changed theoretical physics forever.

Let us suppose a black hole swallows, my laptop I’m writing this article on, books, planets, stars, people, and entire civilizations and the specific details seem to vanish behind the event horizon.

If the black hole later evaporates and only thermal Hawking radiation remains, where did the information go? And that, is what has become known as the Black Hole Information Paradox.

The paradox appears to pit two fundamental pillars of physics against one another. Again, you know this, I’ve mentioned it before. It pits General Relativity against Quantum Mechanics. And this is because quantum theory normally forbids information destruction. What’s surprising is, Hawking’s original result seemed to imply exactly that.  And that is why many physicists consider this one of the deepest unresolved problems in science.

Modern research increasingly views Hawking radiation as an entanglement phenomenon. The radiation escaping from a black hole appears linked to degrees of freedom hidden behind the event horizon, and these quantum correlations may play a crucial role in preserving information.

This current line of thinking has driven decades of research involving Quantum information theory, string theory, holography (my old, now dead, dad was a big fan of holography), and quantum gravity, as well as many other areas.

Moving on, there is another remarkable discovery that Hawking radiation appears closely related to the Unruh Effect.

The what, I hear you say? Another topic for later? Sorry, yes (picture me doing an emoji grimace in apology as I type this), the Unruh Effect predicts that an accelerating observer can perceive empty space as containing thermal radiation. And that is what one observer sees as a vacuum, another observer sees as heat. Many physicists suspect both effects arise from the same underlying physics linking horizons, acceleration, and quantum fields.

Which brings us to the puzzles of tine scales. And that is, there is another challenge lurking inside Hawking’s theory.

When researchers trace Hawking radiation backward in time, some calculations appear to involve wavelengths smaller than the Planck scale (you know what that is), where known physics may stop working completely, and this issue is called the Trans-Planckian Problem. Which suggests we may need a deeper theory of nature to fully understand what is happening near the event horizon of a black hole.

Ah, who was that at the back, another question do I hear? Have we ever seen Hawking Radiation?

Surprisingly, the answer is…

No. We haven’t.

Despite being one of the most famous predictions in science, Hawking radiation has never been directly observed from a real astronomical black hole, and that is because the effect is simply too faint. Remember how long it would take to observe it? That is how faint it is. Even paint dries at the speed of light in comparison. (It doesn’t, bit that sounded cool, didn’t it!).

However, researchers have built laboratory systems that mimic the behaviour of event horizons using optical fibre, fluid systems, and Bose-Einstein condensates, and these analogue systems have produced Hawking-like radiation and, yes there’s another and, in recent experiments, even evidence of the associated back-reaction effects predicted by theory! Cool huh?

While these are not actual black holes, they do provide valuable support for the underlying physics, which leaves us with the final mystery.

And that is perhaps that the most important thing about Hawking radiation is not the radiation itself. There is a deeper lesson, that black holes sit at the intersection of humanity’s three greatest theories, General Relativity. Quantum Field Theory, and Thermodynamics. Unfortunately, those theories do not fit together perfectly, but Hawking radiation exposes the cracks.

Hawking radiation tells us that spacetime has temperature, that gravity may be linked to information, and that entropy and geometry are somehow connected. Oh, and that our deepest theories are still incomplete.

More than fifty years after Hawking’s discovery, physicists are still trying to understand what the phenomenon is really telling us.

The black hole’s faint glow may ultimately reveal not just how black holes die, but how reality itself is built! I’ve said this before at the end of my articles, and I’m going to say it again. How amazingly awesome is that!!

Quantum Teleportation: Not Star Trek, But Still Pretty Wild

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Hello my lovely readers, you may be few, but I love you all the same.

Having had a read through my previous articles since I started this whole bringing physics to the masses journey, I noticed there’s a nice progression developing: Gravity > Relativity > Entanglement > Bell’s Proof, a quick side step into the footy  (let’s not talk about that), which leads naturally onto this week’s article:

Quantum teleportation.

Now then, there’s a misconception about teleportation, and I’ve touched on it with my Star Trek allegories in previous articles.

When most of us hear the word teleportation, we probably all think of Captain James T. Kirk demanding that Scotty gets the malfunctioning transporter fixed pronto and beams him up (or Benjamin Sisko making the same demand of Chief O’Brien, or Captain Janeway…. Sorry, got a bit carried away, on with the article). Quantum teleportation is both less dramatic and far more profound (every time I type the word profound, I can hear Prof Brian Cox saying it in my head).

Unfortunately, scientists have not discovered a way to transport humans, objects, genesis devices, or even particles from one place to another. What they have discovered is a way to transport the quantum state of a particle, that is a complete description of its quantum properties, from one particle to another, potentially over vast distances.

In other words, quantum teleportation does not move matter, it moves information.

And that distinction may reveal something fundamental about the nature of reality.

So, if it’s not Star Trek personnel being teleported, what is?

To understand quantum teleportation, we first need to understand a quantum state.

Again, as I mentioned previously, unlike a classical bit, which can be either 0 or 1, a quantum bit, or qubit to give it its correct term, can exist in a superposition of all states simultaneously: it can be zero, one, or both, at the same time. The state of a qubit contains all the information that can be known about it.

The remarkable achievement of quantum teleportation is that the exact state of one qubit can be recreated in another distant qubit without ever measuring and copying the original state. The original state disappears, and the new state appears elsewhere. There is nothing physical travelling between the two except for a teeny tiny amount of ordinary information.

Quantum teleportation relies on three extraordinary ingredients.

The first ingredient is quantum entanglement.

When two particles become entangled, they cease behaving as independent objects. Instead, they become part of a larger quantum system whose properties are linked regardless of the distance separating them. You know what’s coming, don’t you? Yep, you’ve got it, this is what our old mate Albert Einstein famously referred to as “Spooky action at a distance.”

You’ve read my previous article on Bell’s Inequalities, so you know this already, but I’m going to repeat myself again anyway.

Today, entanglement is one of the most experimentally verified phenomena in physics.

On to ingredient number two. The sender (traditionally called Alice, but who I have renamed Betty in honour of my dear old late Mum), performs what’s known as a Bell-state measurement on the particle she wants to teleport and her half of an entangled pair. This measurement destroys the original quantum state, this destruction is not a bug though, it’s a requirement.

Ingredient three is the classical communication.

Betty then sends Bob, the receiver, two ordinary classical bits describing the measurement result.

It is only after Bob receives those bits that he can perform the operation needed to reconstruct the original state on his entangled particle.

At that moment, the teleportation is complete.

Sound familiar? If you read my “Spooky Action at a Distance” series, it should. I’m about to reuse that same trick about entanglement and the speed limit on information. If you haven’t read it yet… well, what are you waiting for?

Now we have one of the biggest misconceptions concerning quantum teleportation. Why doesn’t it break the speed of light?

Because entanglement creates correlations that appear instantaneous, but usable information still cannot travel faster than light. Bob cannot reconstruct the teleported state until Betty’s classical message arrives. This keeps Einstein’s theory of relativity perfectly safe and intact. No matter how strange quantum teleportation appears, and I know I’m repeating myself here, it does not allow faster-than-light communication.

Let’s look at the rule that makes this all possible, which is a fundamental principle of quantum mechanics called the No-Cloning Theorem. This rule states that an unknown quantum state cannot be copied perfectly, essentially meaning teleportation doesn’t produce two versions of the same particle state, the original state is destroyed, and the distant state is created. Quantum teleportation is a transfer, not a duplication.

The theory of quantum teleportation was first proposed in 1993 by Charles Bennett, Gilles Brassard, Claude Crépeau, Richard Jozsa, Asher Peres, and William Wootters. Their groundbreaking paper showed how an unknown quantum state could be transferred using a combination of entanglement and classical communication. If you really want to have a deep dive into it, let me know and I’ll send you the paper. It took only four years for researchers to successfully demonstrate the effect experimentally using photons in 1997. I remember being really, REALLY, excited at the time, I still get goosebumps looking back to when I first heard the news.

What had once sounded like science fiction had become a laboratory reality.

To me, and I’m sure to many others, this has become one of the greatest ironies of modern physics. Poor Einstein, the phenomenon he disliked most of all, quantum entanglement, became the foundation of quantum teleportation. However, the universe turned out to be even stranger than Einstein imagined.

That’s where Bell came in with his theorem I tried to explain (and hopefully succeeded) in my previous article before the footy one.

For decades, some scientists hoped that hidden variables might explain away Einstein’s quantum weirdness. John Bell showed that certain predictions of quantum mechanics could be experimentally tested and the results repeatedly favoured quantum mechanics and ruled out large classes of local hidden-variable theories.

If it wasn’t for Bell, quantum teleportation might still be considered an interesting mathematical idea rather than a physical reality.

Ah, another question from you? How far have we been able to teleport?

Well, it’s actually a great deal further than you probably think. Quantum states have been teleported using photons, atoms, electrons, superconducting circuits, and solid-state quantum systems.

Researchers have demonstrated space-based teleportation using China’s Micius satellite over distances exceeding 1,000 kilometres. And more recent experiments have teleported quantum information between different physical systems and over telecom-compatible networks designed to support future quantum communications. Just this year, researchers reported teleporting a photon’s state between physically separate quantum dots connected across a 270-metre free-space link, another step toward practical quantum networking.

Looking to the future of this amazing technology, scientists believe quantum teleportation will one day become one of the foundational technologies of a future quantum internet.

Instead of simply sending data, future quantum networks may distribute entanglement between thousands or millions of devices. Quantum teleportation could be used to transfer qubits between quantum computers. It could also be used to construct ultra-secure communication links, enable distributed quantum computing, and build true global-scale quantum networks.

Can you imagine quantum processors in London, New York, and Tokyo acting like pieces of a single giant computer? Well folks, that’s the long-term vision.

Ok, ok, I know you’re desperate to ask the question everyone asks. Could we teleport a person?

Well, in principle, quantum mechanics doesn’t obviously forbid it, but in practice, it is almost unimaginably difficult.

A human body contains roughly 10²⁸ atoms, each participating in an immensely complex web of quantum interactions. Capturing every detail required to reconstruct a person would involve a truly humongously astronomical quantity of information. Oh, there’s also another problem.

Don’t forget the no-cloning theorem in the rules above. The original transported person would have to be destroyed during the process, which raises a somewhat disturbing philosophical question. If a perfect copy appears elsewhere while the original is destroyed, did the person actually travel? Or were they killed while an identical replacement appeared at the other end.

That is a question that science currently has no answer for.

And here we can link back to black holes and wormholes. Deep developments in modern theoretical physics suggest that quantum teleportation may connect to mysteries far beyond communication technology.

Researchers studying black holes discovered unexpected relationships between entanglement, information, spacetime, and wormholes.

There’s the famous proposal, known as ER = EPR, yep, that one from another of my previous articles, which suggests that entanglement and wormholes may be two descriptions of the same underlying phenomenon. Although this is still speculative, these ideas hint that teleportation may reveal something truly profound (there goes Prof B. Cox again. I didn’t know it was possible to have one person saying a single word as an earworm) about the structure of the universe itself.

And then we get to the biggest mystery of them all. Perhaps the most extraordinary aspect of quantum teleportation is that nobody fully understands why reality allows it.

The mathematics works flawlessly and the experiments work repeatedly. And the technology is rapidly advancing.

Yet the deeper philosophical question remains.

Why should information be able to move through the universe in this way?

Quantum teleportation sits at the crossroads of quantum mechanics, information theory, computing, cosmology, and philosophy. Beginning as a clever theoretical idea in 1993, today it is helping scientists build the foundations of the quantum internet.

Who knows, tomorrow, it may help explain nothing less than the nature of space, time, and reality itself! Wouldn’t that truly be profound!

Quantum Entanglement Part One – Spooky Action at a Distance

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Just a quick note before we start: I got a bit carried away with this one. What was meant to be one article on quantum entanglement turned into something closer to a small dissertation, so I’ve split it into two parts rather than dumping the whole lot on you in one sitting which will also give me an extra week do the research and get Part Two much more readable.

This week, Part One: entanglement itself, what Einstein got wrong (and sort of right), and why it doesn’t break the universe. Next Friday, Part Two: what entanglement actually builds, and how deep the rabbit hole goes. Right, on with the show…

Hello, my lovely readers, how about today we take a friendly deep dive into the universe’s strangest connection: Quantum Entanglement.

At some point in your life, you were probably told the universe works like a well-behaved machine. Things move, collide, push, and pull. Causes lead neatly to effects. Objects exist whether or not you’re looking at them.

Then quantum physics came along and politely, but firmly, said:

“Er… Excuse me? I like your thinking, but that’s not quite right.”

And at the heart of that disruption is something both beautiful and unsettling, something the physics boffins call quantum entanglement. The term was first coined by Erwin Schrödinger, you know, the guy with the cat in the box you’re always hearing about?

Einstein famously mocked it as “spooky action at a distance.” He thought it was a flaw, but it actually turned out to be a feature.

Let me try and unpack what that really means, without getting lost in too much maths, (as, I’ve mentioned before, maths isn’t one of my strong points), but still going deeper than the usual surface explanations.

So, what is entanglement?

Imagine two particles created together, say, two photons born from the same event. From that moment on, their properties become linked. They are not just similar, and not just predictable. They are shared, which means if you measure something about one such as its orientation or “spin”, you instantly know the corresponding property of the other.

Even, and this is the truly mind blowing bit, if it’s on the other side of the galaxy.

Well, that doesn’t sound so weird, right? At first glance, it feels normal, I’ll go with the classic analogy, say you have two gloves, one left and one right and you put them in separate boxes. You send one to Norwich and the other one to Waitangi (I chose these two places as I live in Norwich and I googled what is the antipodal point of Norwich City UK; here’s a link for no reason: https://tinyurl.com/4ap8w4d3). When you open one you immediately know what the other one is. No mystery, right? Except this analogy quietly assumes something critical and that is the gloves already had definite identities before you looked.

Unfortunately, quantum particles don’t behave that way.

The twist is that reality isn’t really set until you look. In quantum mechanics, particles can exist in a superposition which is a blend of possibilities. Before measurement, an electron doesn’t have a definite “spin” like up or down, it simply exists in a cloud of probabilities. Are you still with me? I’m going to carry on regardless even if you’re not as you’ll get it at the end, I promise. If I can understand it, absolutely anyone can.

So, when two particles are entangled, it’s not that they secretly agreed in advance that is what they were going to do, it’s more like they didn’t fully decide until one of them was observed and then they both snapped into agreement instantly!

Einstein didn’t like this at all and that’s the part he just couldn’t accept, and was quite vocal about it for many years. He believed in two key ideas: locality, where nothing can influence something else faster than light, and realism: where physical properties exist whether we observe them or not.

Einstein’s big problem with entanglement was that it seems to violate both. So, in 1935, Einstein and colleagues proposed the EPR paradox (I’ll attempt to actually explain this a bit later).

“Quantum mechanics must be incomplete. Something deeper must be going on.”

He suspected hidden variables, unknown factors quietly determining outcomes behind the scenes.

This debate simmered on and on for decades, it sounded philosophical and almost untestable until in 1964, physicist John Bell made a breakthrough.

He showed that if Einstein was right, that is, if hidden variables governed everything, then there should be strict limits on how correlated entangled particles can be. Right?

These limits are called Bell inequalities.

Basically, (without attempting any heavy maths), Bell’s logic boiled down to this:

If particles carry pre-existing answers, and no influence travels faster than light, then their measurement correlations must stay within certain bounds.

Right? Get it? No? Me neither at first and it’ll take yet another blog post to explain it fully, so just go with it for now and I’ll have to tell you all about Bell Inequalities in a different post.

Anyway, back to where we were: quantum mechanics predicts something different. It predicts stronger correlations than classical physics allows.

Physicists tested Bell’s predictions with real experiments, over and over, by taking entangled particles, separating them, and measuring them in different ways.

The result showed that quantum mechanics wins. Every time. Without fail. The observed correlations broke Bell’s Inequality, they couldn’t be explained with hidden variables, and they couldn’t be explained by local interactions either. Furthermore, recent experiments have ruled out all the usual loopholes.

This means we are forced to accept something different and more radical; the universe isn’t both local and real in the classical sense, which means something about our everyday intuition is wrong.

Hang on just a minute, didn’t you say in your last article that you couldn’t have faster than light messaging? If one particle instantly affects another, why can’t we use this to send messages faster than light?

And the answer to that question is quite a simple one, you can’t control the outcome of your measurement. When you measure a particle, you can’t choose “spin up” versus “spin down”; you can only observe whatever happens. Which means you get a random result. While the correlation is instant, there’s no way to encode and transmit information. Nature gives you Einstein’s spooky connection but keeps communications firmly limited by relativity.

And there we have it, the end of Part One, a short one this week as all the extra fun stuff will be packed in to Part Two, which judging by my draft, will be a tad longer. Thanks again for reading, and stay tuned folks, if I pull my finger out and crack on I’ll have Part Two ready for this time next week.