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

Posted on October 9, 2026 by Mal Andrews

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 4^th 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)

Posted on October 3, 2026 by Mal Andrews

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).

Posted on September 25, 2026 by Mal Andrews

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!

Nobody Knows Why Looking Changes Everything – Welcome to the Measurement Problem!

Posted on September 18, 2026 by Mal Andrews

Hello everyone! This week I’m going to try and answer one of the questions I’ve received regarding my piece on the Block Universe. And that is, why does observing a quantum system change it. It is a very good question, and it’s an extremely tricky one to answer as it’s one of those aspects of the teeny tiny stuff that took me a while to wrap my head around.

So what is the answer? Why does observing a quantum system change it? And the answer is…

Well, actually, nobody really knows why.

It is, in fact, one of the deepest questions in physics. And nearly a century after quantum mechanics was developed, nobody knows with certainty why measurement produces definite outcomes. The mathematics predicts experimental results with extraordinary accuracy, but what the mathematics means is still debated.

To take a closer look, imagine you’re in a casino where every roulette wheel is somehow landing on every number at once. Not one result. All of them. Red, black, odd, even, 17, 32, 8, 0. Every possibility exists simultaneously in a cloud of uncertainty. You walk over, look at the wheel, and suddenly there’s only one answer staring back at you. Red 17. One outcome. One reality. The mystery at the heart of quantum physics is that nature seems to work a little like this, and nobody is entirely sure why.

For centuries, scientists imagined the Universe as a giant clockwork machine. Objects had definite properties whether anyone looked at them or not. A football occupied a particular position in the air or on the field, a cannonball travelled along a specific trajectory, and a cat was either asleep or awake.

Then quantum mechanics came along, yet again, and politely informed us that, at the smallest scales, reality appears to be playing by very different rules indeed.

According to quantum theory, particles such as electrons are described by something called a wave function. Rather than telling us exactly where a particle is, the wave function describes all the possible places it could be found. Before measurement, an electron can exist in what physicists call a superposition, which is a state containing multiple possibilities at the same time.

Imagine flipping a coin spinning in the air. While it’s rotating, you can’t honestly call it heads or tails. In a loose sense, it represents both possibilities. The quantum world takes that idea far beyond anything we’re used to. Before measurement, particles don’t merely hide their properties. According to the mathematics, the multiple possibilities genuinely matter.

The famous double-slit experiment, which I mentioned in my Five Things… article, reveals this bizarre behaviour in dramatic fashion. Fire electrons through two narrow slits and they create an interference pattern, exactly what you would expect from waves passing through both openings simultaneously. Somehow, each electron behaves as though it explores multiple possible paths at once. Yet the moment scientists place detectors at the slits to discover which route the electron takes, the interference pattern disappears. Suddenly the electrons behave like ordinary particles. It’s as though nature says, “If you’re not asking, I’ll keep my options open. If you are asking though, I’ll commit to an answer.”

This puzzle sits at the centre of what physicists call the Measurement Problem.

The equations of quantum mechanics describe the wave function evolving smoothly and predictably through time. Left undisturbed, the mathematics allows all these possibilities to continue existing in superposition. Yet whenever a measurement is performed, we observe only one result. Not many. Not a mixture. Just one. The electron appears here. The detector clicks. The cat is alive or dead. The equations predict probabilities perfectly, yet they don’t clearly explain why one specific reality emerges from many possibilities.

Popular science often makes this sound even stranger by claiming that consciousness creates reality. As catchy a headline as this is, most modern physicists don’t believe the human mind is the crucial ingredient. In quantum mechanics, “observation” doesn’t mean a conscious person staring at something. It means a physical interaction that extracts information. A detector can do it. A photon can do it. Even the environment can do it. This is the tricky bit, folks, and it’s the one that I wrestled with when first studying this stuff. Once you can get your head past a person looking at it as the observer, it really does make perfect sense, trust me!

That’s because obtaining information isn’t passive. To discover where an electron is, something must interact with it. Light must bounce off it, a detector must absorb it, or some other physical process must occur. At the quantum scale you cannot simply peek without participating. The act of learning something about the system inevitably becomes part of the system’s story. With me? Of course you are.

For decades this left physicists wondering why the weird quantum world of that pesky teeny tiny stuff doesn’t spill over into everyday life. If electrons can occupy multiple states at once, why can’t cats? Why don’t we see cars parked in several places simultaneously?

Which leads to something you will all be very familiar with, even if some of you struggle to understand it, and no discussion of the measurement problem would be complete without the most famous feline in science, Schrödinger’s Cat.

Are you ready? I’m going to attempt an explanation that hopefully makes sense. In 1935, physicist Erwin Schrödinger invented a deliberately ridiculous thought experiment to show how strange quantum mechanics becomes if you apply it to everyday objects. Imagine a cat sealed inside a box with a tiny amount of radioactive material, a detector, and a vial of poison. If the radioactive atom decays, the detector triggers and releases the poison. If the atom doesn’t decay, the cat lives.

According to quantum mechanics, before anyone opens the box, the atom exists in a superposition of both decayed and undecayed states. With me so far? Good. OK, if you follow the mathematics all the way through, the cat should also end up in a superposition of being both alive and dead at the same time. Schrödinger wasn’t suggesting that cats really exist as zombie-like half-alive creatures. It was quite the opposite. He had designed the experiment to highlight the apparent absurdity of extending quantum superpositions into the everyday world. Yet when the box is opened, nobody ever finds a cat that’s simultaneously alive and dead. They find one or the other. The actual question is: at what point did reality make up its mind? Was it when the atom decayed? When the detector clicked? Was it when the box was opened? Or did both outcomes somehow continue to exist? That deceptively simple question lies right at the heart of the measurement problem and continues to fuel debate among physicists nearly a century later.

This brings us to one of the most important advances in modern quantum theory, which is decoherence.

I could write a whole article on this, but in another attempt to keep it simple, this isn’t my analogy, but it is the most beautifully simplistic one I could find. Imagine dropping a single drop of blue food colouring into a glass of clear water. At first, the drop is obvious and distinct. But within moments the water molecules begin colliding with it. The blue colour spreads throughout the glass until the original blob is impossible to identify. The information about where it started hasn’t vanished. It’s just been dispersed among trillions of molecules.

And something remarkably similar appears to happen in the quantum world. A quantum system begins with delicate patterns of possibility that allow superpositions and interference to exist. But the system never remains perfectly isolated. Photons strike it. Air molecules collide with it. Heat radiates through it. The environment is constantly interacting with everything around it, and as this happens, information about the quantum state leaks into the surroundings and becomes distributed among enormous numbers of particles. The special quantum coherence that made the system behave in a wave-like manner effectively gets diluted into the environment.

The result is that quantum weirdness fades astonishingly quickly for large objects. Your coffee cup isn’t in two places at once because it’s interacting with countless particles every second. The environment is continually monitoring it, as it were. Quantum coherence becomes spread out so rapidly that classical reality emerges almost instantly.

For a while, many physicists hoped decoherence would completely solve the Measurement Problem, and although it solved a huge part of it, it didn’t solve all of it.

The food-colouring analogy helps explain why. Imagine the colouring spreading throughout the water. You’ve explained why the original neat drop is no longer visible. But you haven’t explained why you should focus on one particular blue molecule rather than another.

Likewise, decoherence explains why quantum superpositions stop being observable and why the world looks classical. What it doesn’t fully explain is why a specific outcome appears. It tells us why the roulette wheel no longer displays all possibilities simultaneously. It doesn’t completely explain why you experience red 17 instead of black 32.

This is why competing interpretations still exist. The Copenhagen interpretation accepts collapse as a fundamental part of nature. Many-Worlds suggests every outcome occurs and reality branches into multiple universes. Objective collapse theories propose that collapse is a real physical process waiting to be discovered. Bohmian mechanics argues that particles always possess definite properties guided by hidden quantum processes. All reproduce the experimental data, however, none of them have achieved any universal agreement.

And that’s what makes the measurement problem so extraordinary. Quantum mechanics may be the most successful scientific theory ever devised. It powers modern electronics, lasers, GPS corrections, MRI scanners and emerging quantum computers. Yet beneath its incredible success lies an unanswered question that goes right to the heart of reality itself.

When you look closely enough at nature, possibility seems to come before certainty, but how certainty finally emerges from possibility remains one of the deepest mysteries in all of science.

Phew. I made it! I hope that makes sense, as I stated at the beginning, it’s a very tricky question to answer, and there are so many different ways an attempt at answering it can be made. A bit like the subject matter itself, I guess!

Newton’s Laws: The Three Rules That Keep the World Moving

Posted on September 5, 2026 by Mal Andrews

Another delay in posting, so apologies again, but at least I’m only a day late this time. Anyway, here it is, and this week I’m going to delve into the Laws of Sir Isaac Newton.

Whether you’re kicking a football, driving a car, or watching a rocket launch into space, you’re seeing Isaac Newton’s laws of motion in action. Just take a moment, and imagine you’re sitting on a bus, and the driver, without warning, suddenly slams on the brakes, and your body lurches forward. Why does that happen?

Or imagine a football soaring across the pitch after a powerful kick from Harry Kane has sent the ball screaming into the back of the net from 30 yards out. What is it that makes it speed up, slow down, and eventually stop?

And how does a rocket, weighing hundreds of tonnes, actually manage to leave Earth and get into space?

The answer to all of these questions, and many more, can be traced all the way back to three ideas developed by Sir Isaac Newton more than 300 years ago. Published in 1687, Newton’s laws of motion became the de-facto foundation of classical physics and at the same time transformed our understanding of how the universe actually works.

It is remarkable that these laws are simple enough to explain everyday events while being so powerful they can help send spacecraft into orbit.

Now my faithful few, it’s time to dive in and take a closer look.

Let’s start with the First Law and look at why things don’t like to change.

Newton’s First Law is often called the Law of Inertia, which in simple terms, says that things tend to keep doing whatever they’re already doing. An object sitting still wants to stay sitting still, and an object moving along, minding its own business as it travels in a straight line wants to keep moving along, minding its own business, travelling in that same direction at the same speed. It will only change speed or direction if some force acts upon it causing it to do so.

As obvious as this may sound now, at the time it was a revolutionary idea.

Before Newton came along, most folk believed that motion required a constant force, which, if you think about it, in everyday life seems true. Roll a ball across the floor and it eventually stops. Newton, however, realised the ball doesn’t stop because moving objects naturally come to rest. It stops because forces such as friction and air resistance are working against it and if you were to remove those forces the ball would keep rolling indefinitely, and that tendency to resist changes in motion is called inertia.

You experience inertia every day. It’s why passengers lean forward when they are traveling in a bus and the driver brakes suddenly. All their bodies are simply trying to do is continue moving at the speed they were already travelling.

Newton’s Second Law applies to what happens when you push things. We all know that objects don’t always trundle along, moving in the same way. They can speed up, they can slow down, and they tend to change direction all the time. This is where Newton’s Second Law comes in.

It explains the relationship between force, mass, and acceleration, and in its formulaic state it is usually written as F = ma. In other words, force equals mass multiplied by acceleration. The idea is straight forward enough, the harder you push something, the greater its acceleration is. But the heavier the object, the more force you’ll need to produce the same effect.

Imagine you are pushing an empty shopping trolley along the isles of your favourite supermarket. It moves easily (unless you’ve got the one with the dodgy wheel). Now fill it with your weekly shop and suddenly it takes much more effort to get it moving. The force you’re applying might be the same, but the mass has increased.

This beautiful law is one of the most useful tools in science and engineering as it helps designers calculate everything from the power of a car engine to the thrust needed for a rocket launch.

That takes us nicely onto Newton’s Third Law. And that is, every force has a partner in crime.

By now, you might be wondering how movement starts in the first place, and the third law explains this. And this is the famous saying you have heard many, many times before, as Newton said, “For every action, there is an equal and opposite reaction.” Put simply, this means that whenever one object pushes on another, the second object pushes back with exactly the same force in the opposite direction.

Let’s take something as simple as walking down the street as an example. Most of us simply assume that, when walking, they move forward because their legs push them ahead. But, this isn’t the case as what actually happens is way more interesting. As your foot pushes backward against the ground, the ground pushes forward against your foot, and that reaction force propels you forward. Exactly the same principle explains swimming. As you push water backward, the water pushes you forward. It also explains rocket launches. As engines expel hot gases downward, those gases push back on the rocket, which sends it upward, soaring into the sky and beyond.

Without Newton’s Third Law, space travel wouldn’t be possible.

If you’re looking for proof that Newton’s laws aren’t just dusty ideas from a physics textbook, look no further than Apollo 13.

In the 1995 film, Tom Hanks portrays astronaut Jim Lovell, commander of the ill-fated lunar mission that suffered a catastrophic explosion on its way to the Moon. At one point, with the spacecraft’s systems being shut down to conserve precious power, Lovell turns to his crew and says:

“We just put Sir Isaac Newton in the driver’s seat.”

It’s a great Hollywood line, but it’s memorable because of its roots in reality.

The real Apollo 13 mission faced a daunting physics problem. After the explosion, the crew had to nurse a crippled spacecraft home from hundreds of thousands of miles away, with power limited and most of the systems switched off, so they could no longer rely on their computers in the normal way. Instead, they had to trust in the laws of motion and gravity, Newton’s laws, to carry them around the Moon and safely back to Earth. Even seemingly harmless actions could become a problem. The crew were warned by Mission Control not to vent any waste from the spacecraft into space as this might create a small thrust, tiny enough that it could nudge them off course. In the vacuum of space, where there is no air resistance to slow things down, even tiny forces matter, and that is what Jim Lovell meant by “putting Newton in the driver’s seat.” The astronauts were placing their faith in the very laws Newton had described nearly three hundred years earlier.

The First Law kept the spacecraft moving along its path once it was set in motion, and the Second Law explained how small, carefully planned engine burns would alter their path when course corrections were needed. The Third Law explained why those engine burns worked at all, as gases expelled in one direction pushed the spacecraft in the opposite direction.

It’s one of those rare moments where science, history and popular culture intersect perfectly. At the height of the Space Age, surrounded by cutting-edge technology, three astronauts ultimately trusted one of the oldest and most fundamental ideas in physics. When everything else seemed uncertain, Sir Isaac Newton was still safely at the wheel.

As individually simple as Newton’s laws are, they produce a powerful picture.

The first tells us that motion doesn’t change without a force. The second tells us how much motion changes when a force is applied. The third explains where many of those forces come from in the first place.

Together, the three laws create a complete picture of how objects move, interact, and respond to the world around them. From bicycles and footballs to aircraft and planets, these three principles describe an astonishing range of motion.

More than three centuries after Newton wrote them down, they remain among the most important ideas in all of science.

So, the next time you’re on a bus and the driver brakes suddenly, or you’re at the footy and a screamer hits the back of the net, or you‘re watching Apollo 13 and Tom Hanks utters that famous line, you’ll be witnessing those three elegant laws at work.

Although the technology may change, the universe is still playing by Newton’s rules.

TIME IS NOT WHAT YOU THINK IT IS – The Day Einstein Destroyed Common Sense

Posted on August 31, 2026 by Mal Andrews

Hello everybody, apologies for the three-day wait for this one, I’ve been away with the family over the weekend, during which I have managed to properly injure my back. Despite the pain though, it’s time for another promised article, the one on Special Relativity, and for this one I’m going to start with a classic.

Imagine you’re sitting on a train moving smoothly through the countryside, and while you’re sitting you happen to pull out a tennis ball, you conveniently have with you, and toss it to a friend sitting opposite you. Everything feels normal, the ball travels over the table exactly as expected, and your friend catches it. Now imagine I am standing beside the tracks watching as you make the same throw as the train passes by me. To you, the ball moved at about 20 mph, however, to me, observing from outside, the ball moved at the train’s speed plus the speed of the throw.

For centuries, this simple idea seemed obvious, and it was the foundation of Isaac Newton’s view of the universe. Then, in 1905, a 26-year-old patent clerk named Albert Einstein published a paper that changed everything. In that paper, he came to a startling conclusion. Space and time are not fixed but actually bend to accommodate one unbreakable rule. And that rule is:

The speed of light is always the same.

You all know this, I’ve written about it plenty of times in my articles now, but at the time, this was revolutionary.

299,792,458 metres per second, which is around about 186,000 miles per second, fast enough to travel around the earth about 7 times in one second, and fast enough to reach the moon in about 1.3 seconds. What makes light particularly special though, is every observer measures it moving at exactly that speed, regardless of their own motion.

I know this sounds impossible but just suppose you are standing still and you are measuring a beam of light from a torch (flashlight to my American readers) and I come racing towards it at 99% of light speed. Common sense tells us that I should measure the light moving only a little faster than me, but I don’t. And neither do you. What we both actually measure is exactly the same speed. Nature is somehow protecting this value, but it’s doing it at a price. Reality itself must change.

The first casualty of this is time. Now then, Newton believed time flowed identically everywhere, however, Einstein discovered that time behaves more like an elastic material. That is, the faster you move, the slower your clock runs compared with someone standing still, and physicists call this time dilation.

Imagine two identical clocks. One of them is safe and sound on Earth, hanging on your kitchen wall while the other is flying through space at enormous speed. If you were to retrieve the travelling clock after its journey it would show that less time has elapsed than the one on your kitchen wall. It has literally experienced less time, not because it has malfunctioned, and not because of some kind of optical illusion. It is showing less time because time itself has passed more slowly for it.

There are tiny particles produced high in the Earth’s atmosphere called muons which without relativity should decay long before reaching the ground, but lots of them survive. Why do they survive? Because they travel near light speed, and their internal clocks run slower. Exactly as Einstein predicted.

On to the next question. If time can stretch, what about space? Well, it turns out space makes sacrifices as well, as an object moving rapidly relative to you becomes shorter in the direction of travel, and physicists call this Length Contraction.

Imagine a spacecraft that is 100 metres long while resting in its space port. After undocking and zooming off to Alpha Centauri, as it approaches light speed, a stationary observer sees it become shorter and shorter, while the crew onboard experience nothing unusual, as from their perspective, it is the rest of the universe that has changed. And this is one of relativity’s strangest lessons. There is no single universal viewpoint as different observers can measure different lengths and times and still all be correct.

Moving on, most people believe they know what “at the same time” means. Einstein showed that they don’t.

Imagine a train, again. There’s a massive thunderstorm raging overhead and bolts of lightning strike both ends simultaneously. To someone standing on the station platform, they would see both flashes arrive at the same moment, so to them the lightning strikes happen simultaneously. However, to someone sitting on the moving train, because it is moving towards one flash and away from the other, the flashes reach them at different times, and to them the strikes were not simultaneous.

So, which person is correct in what they witness? The answer is both of them, because simultaneity itself depends on motion, and this idea was a shock for physicists as it meant that even the ordering of events can depend on your frame of reference.

Ok, let’s move on again. Before Einstein, space was space, time was time, and small furry creatures from Alpha Centauri were small furry creatures from Alpha Centauri.

Sorry, got a bit keyboard happy there, forget the small furry creatures from Alpha Centauri

Back to space and time, before Einstein, these were always perceived as separate things, but after Einstein, physicists realised they are really aspects of a single entity. That’s right, you’ve guessed it. Spacetime

Every event in the universe has three spatial coordinates and one time coordinate, and together they form a four-dimensional reality called spacetime. You are not merely travelling through space, what you are doing is continuously moving through spacetime. Right now. At this very moment.

This brings us back to the equation that everyone knows, especially if you are a regular reader of my stuff, and are aware of the trouble I had when trying to produce a quick mid-week article on it recently.

E = mc²

Perhaps the most famous equation in history. And to translate it into plain English, without all the complicated maths this time, it basically says that mass and energy are different forms of the same thing. Matter can become energy, and energy can become matter, and the conversion factor is the speed of light squared.

Since light speed is enormous, even tiny amounts of matter contain staggering amounts of energy, and as you regulars know, this principle powers the Sun, nuclear reactors, nuclear weapons, along with many other processes throughout the universe.

While we are on the subject of the speed of light, let’s take a look at it.

Science fiction often treats the speed of light as something that can eventually be exceeded, Special Relativity, however, says otherwise. As an object accelerates its energy increases, the energy required for further acceleration rises dramatically, and near light speed the required energy approaches infinity. Because infinite energy is impossible, a material object of mass can never quite reach the speed of light. Photons can travel at light speed because they have no rest mass (remember my equations the other week?). Everything else though must remain below that cosmic speed limit.

Perhaps the most famous story in relativity is the Twin Paradox. Ready for another analogy? Good, here we go.

Imagine identical twins. One of them stays on Earth, while the other is on our imagined spaceship travelling to Alpha Centauri at near light speed before eventually returning home. When they meet again, the Earth-bound twin is older, while the space-faring twin is younger.

This sounds impossible as shouldn’t each twin see the other moving? The key to this is that the traveller accelerates, turns around and changes reference frames and the Earth twin does not. When all the mathematics is done, the traveller genuinely ages less. Which is why Matthew McConaughey has hardly aged at all when he returns from his interstellar travels and visits his aged daughter. And what is really mind boggling about this is that if fast enough journeys were possible, your future descendants could be older than you after your return!

Moving along once more, many people think relativity is only useful to astronomers, whereas in reality you and I are using it all the time as we drive around to unknown destinations, or have a nosey at our phone to see where the kids are. You’ve guessed it, I’m talking about GPS navigation

GPS satellites carry incredibly precise clocks and those clocks do not tick at exactly the same rate as clocks on Earth so engineers must correct for relativistic effects or navigation errors would rapidly build up. Every time your phone finds a location, a small victory for Einstein is taking place!

So, what did Einstein really teach us?

More than a century later, Special Relativity remains one of the most thoroughly tested ideas in science. Experiments involving high-speed particles, atomic clocks and modern technology continue to confirm its predictions. But at its deepest, the lesson isn’t a mathematical one, it’s a philosophical one.

For thousands of years humans assumed time was universal, space was fixed, and simultaneous events were absolute. Einstein showed us that none of these assumptions are true and the universe is stranger, more elegant and far more astonishing than common sense ever imagined.

Special Relativity’s big reveal is that space and time aren’t the fixed stage we assume they are as they are flexible, they stretch, they bend around each other, and they do it all in service of one stubborn rule. And that rule is the speed of light never changes, no matter who’s watching.

Einstein’s General Theory of Relativity – The Revolutionary Idea That Changed Our Understanding of Reality

Posted on August 14, 2026 by Mal Andrews

I’ve chosen a biggie this week folks, Einstein’s General Theory of Relativity. And boy it really is a biggie! It would take volumes and volumes of books to take you through everything, and years and years of research and study for me to write it. So, I’m going to have a go and see if I can put together some kind of short comprehensive guide for you. Ready?

Imagine you’re standing on Earth, feeling gravity pull you toward the ground. For centuries, scientists believed gravity was an invisible force acting across space. Then, in 1915, Albert Einstein popped his two penneth in and proposed something that was truly astonishing. Einstein proposed that gravity isn’t really a force at all, and that instead, massive objects such as planets, stars, and galaxies actually bend the fabric of space and time itself, and what we experience as gravity is actually the result of moving through this curved spacetime.

In a flash, Einstein had overturned centuries of thinking and by doing so he gave humanity a completely new picture of reality.

Before General Relativity, Isaac Newton’s theory of gravity was king, and his equations successfully explained falling apples, planetary orbits, ocean tides, and the motion of the Moon.

However, for everything that Newton’s laws could explain, there were still some puzzles remaining. Newton’s explanation of gravity appeared to act instantly across vast distances, while Einstein’s Special Relativity showed that nothing can travel faster than light. There were also subtle discrepancies in Mercury’s orbit that Newton’s theory couldn’t fully explain, and Einstein believed there had to be a deeper explanation, and there was.

Einstein’s breakthrough began with a simple thought experiment.

Imagine you’re trapped inside a windowless lift (elevator to my American readers).

In one scenario, the lift (elevator) is sitting on Earth, and in another, it’s floating in deep space, but it is accelerating upward. In both cases, you feel pressed against the floor. But, without looking outside, you can’t tell which situation you’re in.

This observation became known as the Equivalence Principle, and that is gravity and acceleration are locally indistinguishable, and for Einstein, this was the clue that unlocked a completely new understanding of gravity.

This is where spacetime comes in, and it is so breathtaking in its simplicity it is mind blowing.

Einstein realised that space and time are not separate things, but instead, they form a single four-dimensional structure which he called spacetime.

Now then, you have to think of spacetime as the stage on which everything in the universe exists and moves. And, to do so, I’m going give you a classic analogy.

Imagine a giant trampoline stretched tight, and as it is stretched tight, it is flat. If you now place a bowling ball in the centre of the trampoline it creates a dip, and if you now roll a tennis ball nearby, its path curves as it rolls.

The tennis ball isn’t being directly pulled by the bowling ball, all it is doing is simply following the shape of the surface, and this is how planets move through spacetime that has been curved by stars and other massive objects.

I know it’s not perfect, but this analogy captures Einstein’s revolutionary insight that it is mass that changes the geometry of the universe.

So, to your first question, I know you have loads. How does gravity really work?

And the answer to this is when most people think about gravity, they imagine an invisible force pulling objects together, however, Einstein saw something completely different.

Here’s another simple analogy (there’s going to be a few of these, so stick with me).

Imagine it’s nighttime and you are driving along a mountain road. Although you keep the steering wheel pretty straight, the road curves left, looking from above, someone might reasonably think that an invisible force has pushed your car sideways when in reality, you’re simply following the shape of the road.

According to General Relativity, planets are doing exactly this, and the Earth isn’t being pulled around the Sun by a mysterious force, it is moving along the curved road of spacetime created by the Sun. The sun is the bowling ball on the trampoline, and the tennis ball is the Earth. Geddit? Of course you do!

Ok, let’s look how that applies to the whole of the cosmos.

At the heart of General Relativity is a set of mathematical relationships called the Einstein Field Equations, and physicists often summarise them this way, and again, it is incredibly brilliant in its simplicity.

Matter and energy tell spacetime how to curve, and curved spacetime tells matter how to move, and these equations connect the contents of the universe to the shape of the universe itself! Cool, huh!

These equations can describe everything from planetary motion to black holes and even the evolution of the cosmos.

And that neatly leads us on to the next question you are bursting to ask.

“If gravity isn’t a force, then why doesn’t the Earth fly away from the Sun?”

And for that answer we have another simple analogy.

Imagine you are throwing a ball. If you throw it gently it lands on the ground nearby to you, however, if you throw it harder, it travels further and if you were to throw it harder and fast enough, the Earth’s surface curves away beneath it as quickly as it falls. The ball keeps falling but never reaches the ground, and that is essentially what an orbit is.

Earth is constantly falling through curved spacetime around the Sun.

One of General Relativity’s strangest predictions is that time does not flow at the same rate everywhere, and near a massive object, time passes more slowly, and the further away, time passes more quickly.

OK, analogy number 3? 4? I’ve lost count already.

Imagine time as a river. Far from massive objects, the river flows quickly, and near a massive object, the current slows. Two people that have been travelling through different parts of the river can reunite and discover that different amounts of time have passed for them.

This isn’t science fiction; this is science fact, as GPS satellites must account for relativistic time effects to provide accurate navigation. To really delve into time, you should read The Order of Time by Carlo Rovelli. This book is a brilliantly understandable read, and you’ll have your head wrapped around time in no time. And it’s got Smurfs in it!

Something else General Relativity told us is that light can bend. Before Einstein, all the science nerds simply assumed that gravity only affected matter. General Relativity predicted that gravity affects light as well.

And to explain it, you guessed it, another analogy.

Imagine you are riding a bicycle along a painted line on the ground, you aren’t intentionally turning. You are simply following the path beneath you. Light behaves similarly. It travels along the straightest possible path through spacetime, and if spacetime itself is curved, the path of light appears bent. Observations of the famous solar eclipse of 1919 confirmed this prediction and also made Einstein world famous.

The bending of light creates one of astronomy’s most powerful tools, and that is gravitational lensing. This is where massive objects can bend light from distant galaxies and act like giant lenses. If you hold a wine glass in front of a distant light, the image behind it appears stretched, distorted, or sometimes, even duplicated, and galaxies do the same thing to light, and astronomers use these natural lenses to study objects that would otherwise be too distant to see.

General Relativity also predicts objects so dense that spacetime becomes dramatically distorted, and, you’ve guessed it, as these are one of my favourites, it predicted black holes, and with them, their ever brilliantly baffling event horizons, which leads me to my next analogy, the river model of black holes.

Imagine a fish swimming upstream, and way ahead of it is a waterfall. While it is far away from the waterfall the little fishy can easily fight against the current, however, when it gets closer to the waterfall, the water moves faster, until eventually there is a point where the current exceeds the fish’s maximum swimming speed. Beyond that point, escape is impossible, and the little fishy is heading over. A black hole’s event horizon is similar. Beyond it, spacetime is being dragged inward so strongly that not even light can escape. But you know all this, I’ve written about it loads.

General Relativity also predicts that moving massive objects can create disturbances in spacetime itself and these are known as gravitational waves.

Drop a pebble into still water and waves spread outward in all directions. When massive objects such as black holes collide, they create ripples in spacetime that travel across the universe. And those clever scientists detected these waves directly in 2015, thus confirming another of Einstein’s remarkable predictions.

General Relativity has become the foundation of modern cosmology, and it helps explain the Big Bang, the expanding universe, the evolution of galaxies and the large-scale structure of the cosmos itself, and in many ways, modern astronomy is the story of applying Einstein’s theory to increasingly larger scales.

Unfortunately, Einstein’s theory, as brilliant as it is, isn’t perfect. Even though every major experimental test has supported General Relativity for more than a century, physicists know the theory is incomplete as it struggles to explain what happens at the centre of black holes, the earliest moments of the Big Bang, and how gravity works at quantum scales, that pesky teeny tiny stuff again, and finding a theory of quantum gravity remains one of the greatest challenges in science today.

If you remember only one thing about General Relativity, make sure it’s this

For more than 200 years, Isaac Newton’s theory of gravity successfully explained the motions of objects on Earth and the movements of the planets. In Newton’s view, gravity is a force that pulls objects toward one another. The Earth is pulled toward the Sun, the Moon is pulled toward the Earth, and an apple falls because the Earth exerts a gravitational force on it. This picture works remarkably well for most everyday situations and remains extremely useful today.

Einstein’s insight was way more radical.

According to General Relativity, gravity is not fundamentally a force at all. Instead, mass and energy change the geometry of the universe itself by curving spacetime. Planets, stars, galaxies, and even light move through this curved spacetime, following its natural paths. What we perceive as the force of gravity is actually the consequence of moving through a universe whose geometry has been distorted by matter and energy.

A useful way to picture the difference is to imagine a ball rolling across a landscape. Newton would describe the ball’s motion as being caused by forces acting upon it. Einstein would direct your attention to the shape of the landscape itself. If the ground is curved, sloped, or warped, the ball’s path changes naturally as it follows the terrain. In a similar way, planets orbit stars because they are moving through curved spacetime, not because an invisible force is reaching out and pulling them around.

This seemingly simple change in perspective transformed our understanding of the cosmos. From it emerged the prediction of black holes, the discovery of gravitational waves, the realisation that time can flow at different rates in different gravitational environments, and the modern picture of an expanding universe. More than a century after Einstein introduced his theory, it is still one of mankind’s greatest achievements, and it remains humanity’s best description of gravity and one of the most profound (I had to get that word in here somewhere) insights ever achieved in science.

And that my faithful readers, is Einstein’s Theory of General Relativity for you in a nutshell. For anyone who just wanted the 1905 Special Theory, it’s the short, sharp one about speed and simultaneity, no bendy trampolines required. You can pretend the last ten minutes didn’t happen, and, if you’re lucky, and you really want it, Special may get its own piece in a few weeks’ time.

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

Posted on July 31, 2026 by Mal Andrews

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.

Posted on July 28, 2026 by Mal Andrews

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

Posted on July 23, 2026 by Mal Andrews

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!!

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