Tag Archives: Space Science

Here’s A Question That Is Cleverer Than It Sounds. Why Is the Night Sky Dark?

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Slight change of pace this week folks, my back is still playing up, and I haven’t had much of a chance to do a lot of research this week. I’m also feeling a bit guilty following on from last week’s article, which got far fewer obsessive rewrites than I would usually dedicate to my musings.

So, today, I have a simple question for you. Have you ever looked at something which is everyday and innocuous, like a flower or a feather, or the night sky, and wondered, “Why is that the way it is?” Of course you have, we all have at one time or another, often without realising we are doing it. Well, it turns out that some of the greatest discoveries in science began with people asking surprisingly simple questions. Such as, “Why do apples fall?”  or “Why do planets move?” or, “Why does time seem to flow in only the one direction?” Questions I have attempted to answer in previous articles.

One such question, as I alluded to in the title, is, “Why is the night sky dark?”  And this very question came to be known as Olbers’ Paradox, and it may even be one of the most deceptively simple questions ever asked.

Why is it called Olbers’ Paradox? I hear you ask. Well, it is named after the German astronomer Heinrich Wilhelm Olbers, who first wrote about it in 1823. Olbers wasn’t the first one to ask this question, others such as Johannes Kepler, Edmund Halley and Jean-Philippe de Chéseaux had asked the same question over the preceding couple of centuries, and I’m sure it is a question that has been asked going way back to the Stone Age.

When you think about it, like many deceptively simple questions, it hardly seems worth discussing. The sky is dark because it is night, isn’t it? Case closed. Everyone can go home now that we have answered that one. Hang on a minute though, let’s not forget that the universe has a habit of making fools of us whenever we think we have an easy answer such as that one.

To actually find the answer, we have to look back into the dim and distant past and try to imagine what ancient astronomers thought the universe was like. For centuries, many believed the universe was infinitely large, filled with stars, and had existed forever, which, when you think about it, sounds like another perfectly reasonable answer. If the universe had no beginning and stretched endlessly in every direction, then it stands to reason there would be stars everywhere you looked. And that, my faithful readers, is where things start to go wrong, and leads me to analogy time!

Now then, imagine you are standing in an endless forest and no matter which direction you look, your line of sight always and inevitably falls upon a tree. There may very well be lots of gaps between the trees, but with an infinite number of trees spread across an infinite landscape in our endless forest, every view eventually ends with bark, twigs and leaves. Now, swap all the trees for stars.

If the universe is infinite and has existed forever, then it now stands to reason that every line of sight should eventually end on the surface of a star. Therefore, the night sky should not be mostly black. It should be one giant wall of starlight or, put another way, the entire sky ought to be bright. Very bright. So bright, it should potentially be as bright as the surface of an average star, and it is at this point that nature gently clears its throat and points out that the night sky is, in fact, not blindingly bright. It is actually very dark with little pinpricks of light scattered all over it. So, why is that? What has gone wrong?

The first thing to come to mind might be to say that distant stars are simply too faint to see, which again, sounds completely reasonable until you dig into the subject I dread the most. The maths.  OK, while distant stars are dimmer, there are also loads more of them, and every time you look deeper into space, the number of stars increases dramatically. These extra stars effectively make up for the loss of brightness, and an infinite universe would therefore provide an infinite number of contributions to the brightness of the sky. Yeah? Well, no. And this is one of those annoying situations where maths refuses to cooperate with our common sense.

Maybe, scientists began to wonder, clouds of dust are blocking the light, and again, this feels like a perfectly reasonable solution. Unfortunately, as soon as we bring physics into the picture, that perfectly reasonable solution gets binned very, very quickly.

This is because physics tells us that dust absorbs light, which means it also absorbs energy, and absorbing energy makes things warm up. Given an infinite amount of time, all that dust would eventually become hot enough to glow, and rather than obscuring and hiding the starlight from our view, it would simply absorb it and reradiate it. The sky would still end up bright, and once again, the universe has outsmarted us.

For a surprisingly long time, nobody had a satisfactory answer to this and the paradox sat there quietly pointing out that something about our picture of the cosmos was wrong.

The breakthrough finally came when astronomers realised that the universe has not existed forever, a realisation that turned out to actually be quite important.

Modern measurements show that the universe is about 13.8 billion years old, and as unimaginably ancient as that may seem, it is not eternal. As you and I know, from my previous articles as well as from science, light travels at 299,792,458 metres per second, which is a finite speed. Therefore, we can only see objects whose light has had enough time to reach us, which in turn means that a lot of the universe simply lies beyond our current cosmic horizon. We can’t see everything.

Think of it like being in a vast city at night during a power cut. If someone starts switching on lights across the city, you only see the ones whose light has already reached you. The fact that more lights exist farther away doesn’t matter.

The universe works in a similar way as there has only been a finite amount of time for light to travel to us, so we do not receive light from every possible star. In fact, this finite age does most of the work.

So, is that the problem solved? Well, not quite. Another part comes from the discovery that the universe is expanding.

When astronomers like Edwin Hubble began studying distant galaxies, they found something remarkable. Space itself is stretching, and as it stretches, light waves stretch with it. Their wavelengths become longer, their energy drops, and the light is shifted towards the red end of the spectrum. Push this process far enough and visible light can become infrared radiation, microwaves, or radio waves. In essence, the universe has been turning down the brightness knob a bit more.

Although a huge amount of ancient light still exists, much of it has been stretched beyond the range that our human eyes can detect. If our eyes were designed to see microwaves instead of visible light, the sky would actually look rather different. In fact, it would be glowing, but not with starlight.

This glow is something you have very likely heard of and is known as the Cosmic Microwave Background, and was discovered by astronomers over 60 years ago, way back in 1964. What’s more, it fills the entire sky. It is the earliest light we can observe, released about 380,000 years after the Big Bang, and before any stars were formed. It has been travelling through expanding space for billions of years, and over those billions of years it has cooled to just 2.7 degrees above absolute zero.

So, thinking about it, the night sky is not dark at all. We are simply looking at it with the wrong kind of eyes.

What makes Olbers’ Paradox so fascinating is that it starts with an observation so ordinary that most people never think twice about it. Every child has looked at a dark night sky, every human civilisation has seen the same darkness between the stars, yet hidden within that darkness was a clue that the universe had a beginning.

Long before anyone discovered the Big Bang, long before anyone measured the expansion of space, and long before anyone detected the Cosmic Microwave Background, the night sky was already giving the game away. It was quietly telling us that the universe could not be infinitely old and unchanging. How about that for a large expanse of darkness!

It makes you think though, doesn’t it? Well, it does me. Sometimes the most profound discoveries do not come from finding something new. They come from finally noticing something that has been staring us in the face all along. In the case of Olbers’ Paradox, the clue was not a bright star, a spectacular galaxy, or an exotic black hole. It was all the blackness in between!

Neutron Stars and Pulsars: Nature’s Most Extreme Laboratories

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First of all, I must apologise to you, my faithful few, for the lack of an article last week. Firstly, I was away visiting a friend in Spain and hadn’t got an article close enough to finishing for publishing. Secondly, I am still suffering with my back, which has been making it somewhat difficult to sit and do the necessary research to make these articles as entertaining and explanatory as I try and do.

Anyway, all that aside, I’m sort of coming in a day early this week, and I’m heading back to the cosmos in an attempt to explain Neutron Stars and Pulsars. What they are, where they come from, and what they do. Hopefully. As ever, you’re the judge, have a read and let me know your thoughts.

Among all the objects in the observable universe, neutron stars are arguably the most extraordinary. They are the collapsed remnants of massive stars that have ended their lives in titanic supernova explosions, compressing more mass than our Sun into a sphere only about twenty kilometres (about 12.5 miles) across. Now then, these astonishing objects are so incredibly and immensely dense that they challenge our understanding of matter itself and offer scientists a glimpse into physical conditions that can never be recreated here on Earth.

So, where do they come from? Well, the story of a neutron star begins with a massive star, typically one containing at least eight times the mass of our own Sun. Throughout most of its life, a star generates energy through nuclear fusion, using immense temperatures and pressures in its core to combine lighter elements into heavier ones. During the longest phase of a star’s existence, hydrogen nuclei fuse together to form helium, releasing enormous amounts of energy in the process. This energy creates an outward pressure that balances the inward pull of gravity that keeps the star stable and shining brightly.

As the supply of hydrogen gradually becomes depleted, the star begins fusing progressively heavier elements. Helium fusion produces carbon and oxygen. In stars that are sufficiently massive, carbon is then fused into elements such as neon, sodium and magnesium. Neon fusion creates oxygen and magnesium, while oxygen fusion produces silicon, sulphur and a variety of other elements, too many to list here, and, if I’m honest, I don’t know all of them and if I carry on researching them, this article is never going to see the light of day (see what I did there?). Eventually, silicon fusion forms iron and nickel in the star’s core, with each successive stage requiring temperatures far greater than the last, which creates a layered structure within the star somewhat like the layers of an onion.

This process effectively turns a massive star into a cosmic factory. Over millions of years it manufactures increasingly heavier elements, transforming hydrogen into helium, helium into carbon and oxygen, and then producing many of the elements that make up planets, oceans and living things. The carbon in your cells, the oxygen you breathe, the calcium in your bones and much of the iron in your blood were all forged within stars long before our Solar System existed. Cool, yeah? We really are made from stardust!

Anyway, this process continues until iron accumulates in the core, which in turn marks a critical turning point in a star’s life because, unlike lighter elements, fusing iron does not release energy. Instead, it requires energy, and as a result, the star suddenly loses its ability to generate the outward pressure needed to oppose gravity. Once the core becomes dominated by iron, the balance that has sustained the star for millions of years collapses as gravity gains the upper hand and the core implodes in just a fraction of a second.

This collapse is so incredibly violent that the outer layers of the star are blasted into space in a supernova explosion, while deep within the collapsing core, electrons and protons are crushed together to form neutrons. What remains is an incredibly compact object composed almost entirely of neutron matter. If the remaining core contains too much mass, the collapse continues and a black hole forms. If the mass falls within the appropriate range, however, the core stabilises as a neutron star.

A useful analogy is to imagine gravity and quantum forces playing a tug-of-war.

As gravity is trying to crush the star, a quantum effect known as neutron degeneracy pressure is pushing back. If the core’s mass is within the appropriate range, that is 1 to 3 times the mass of the Sun, the two balance and a neutron star survives. If gravity is too strong, gravity wins and a black hole forms. So basically that means, if the collapsed core is heavy enough to avoid becoming a white dwarf, but not so heavy that it must become a black hole, the inward pull of gravity is balanced by neutron pressure and the object settles into a stable neutron star.

That is, if the remaining core is relatively small, it becomes a white dwarf, and this happens to stars less massive than those that produce neutron stars. If the core is roughly between about 1 and 3 times the mass of our Sun, the collapse can be halted by quantum-mechanical forces between neutrons, and the core stabilises to become a neutron star.  If the core is more massive than the maximum mass a neutron star can support, as even neutron pressure cannot resist gravity, the collapse continues indefinitely and creates a black hole. Simple stuff, isn’t it!

It is the supernova itself which is responsible for creating and dispersing many heavy elements into interstellar space, enriching future generations of stars and planets. Even heavier elements, including gold and platinum, are now thought to be produced primarily during neutron-star mergers, where two neutron stars collide in one of the most energetic events in the universe.

The resulting neutron star is almost impossibly compact. Although it typically measures only about twenty kilometres in diameter, it contains roughly one and a half times the mass of the Sun. Some neutron stars are even more massive. Which means that a quantity of neutron-star material no larger than a sugar cube would weigh around a billion tons on Earth, and make a decent meal for Nibbler and his kind from Futurama, remember I mentioned this in a previous article? Another comparison offered by NASA states that a teaspoon of neutron-star matter would weigh millions of tons. If our own planet were compressed to the same density, Earth would shrink to a sphere only a few hundred metres across.

Such enormous density gives rise to equally extraordinary gravity. At the surface of a neutron star, gravity can be approximately one hundred billion times stronger than it is on Earth, and an object falling towards the surface would accelerate to a significant fraction of the speed of light before impact. The gravitational field is so intense that it bends light itself, allowing an observer to see more than half of the star’s surface simultaneously because light from the far side can be curved around the object on its journey through space. Remember my article on spacetime?

Despite decades of study, scientists still do not fully understand what lies inside a neutron star. The outer layers are thought to consist of an ultra-dense crust of atomic nuclei immersed in a sea of electrons. Deeper inside, neutrons dominate the structure, and are packed together far more tightly than in ordinary atomic nuclei. At the very centre, conditions may be so extreme that matter exists in exotic forms unknown elsewhere in the universe. The core may contain superfluid neutrons, superconducting protons, strange particles called hyperons, or even quark matter, in which the fundamental constituents of protons and neutrons exist freely. Determining the true nature of neutron-star interiors remains yet another one of the greatest unsolved problems in modern physics.

As is the way with all things cosmic, some neutron stars can reveal themselves in a more dramatic fashion. These objects, known as pulsars, are rapidly rotating neutron stars that emit beams of electromagnetic radiation from regions near their magnetic poles. The magnetic axis is usually tilted relative to the spin axis, so as the star rotates the beams sweep through space in much the same way that the beam from a lighthouse sweeps across the sea. Whenever one of these beams crosses Earth’s line of sight, astronomers detect a pulse of radiation, that is, the object appears to be flashing on and off, even though what we are actually witnessing is the star’s rapid rotation. Every pulsar is a neutron star, but only those whose beams happen to point towards Earth can be observed as pulsars.

The incredible spin rates of pulsars originate during the collapse of their parent stars. As the original star’s core shrinks from hundreds of thousands of kilometres across to only a few tens of kilometres, angular momentum is conserved, similar to a figure skater spinning faster when pulling their arms inward, and as a result, neutron stars can rotate at extraordinary speeds. While many pulsars rotate once every few seconds, others complete hundreds of rotations every second. The fastest known pulsar, PSR J1748−2446ad, spins approximately 716 times per second, equivalent to about 43,000 revolutions every minute.

The discovery of pulsars was one of the most remarkable moments in twentieth-century astronomy. In 1967, while analysing data from a radio telescope at the University of Cambridge, graduate student Jocelyn Bell Burnell noticed a highly regular series of radio pulses arriving from space. The signals were so precise that, for a short time, members of the research team jokingly referred to the source as LGM, standing for Little Green Men! Further observations soon showed that the signals originated from a natural astronomical phenomenon, leading to the discovery of the first known pulsar and providing the first direct evidence for the existence of neutron stars.

One of the most remarkable characteristics of pulsars is their astonishing precision. The regularity of their pulses makes them among the best natural timekeepers in the universe. In some cases, their long-term stability rivals that of atomic clocks here on earth. This precision enables astronomers to use pulsars for testing Einstein’s theories of relativity, searching for gravitational waves, creating highly accurate timing systems and even investigating methods of navigating future spacecraft using pulsars as galactic positioning beacons!

While pulsars are impressive, there is an even more extreme variety of neutron star that exists. These objects, known as magnetars, possess the strongest magnetic fields known in nature. The standard unit for measuring magnetic fields is the Tesla (T), and according to the European Space Agency, their magnetic fields can reach around one hundred billion Tesla. For comparison, Earth’s magnetic field is only a tiny fraction of a Tesla, that is 0.00005 T, and even powerful MRI scanners operate at only 1 – 3 T. The magnetic field of a magnetar is powerful enough to distort atomic structures, fracture the star’s crust and release immense bursts of X-rays and gamma rays. Only a few dozen magnetars have been identified, which makes them among the rarest of known stellar remnants.

Neutron stars also play a crucial role in some of the most violent events in the cosmos. In binary systems, two neutron stars can orbit one another for millions or even billions of years, and as they do so, they gradually lose energy through the emission of gravitational waves causing them to spiral closer together. Eventually they collide and merge, and these mergers generate enormous bursts of energy, produce ripples in spacetime and create spectacular explosions known as kilonovae (article on kilonova vs supernova coming soon). They are also believed to be responsible for producing many of the universe’s heaviest elements, including gold and platinum, as mentioned above.

The landmark detection of GW170817 in 2017, the first-ever joint detection of gravitational waves and electromagnetic radiation from a binary neutron star merger, represented humanity’s first direct observation of gravitational waves generated by a neutron-star merger and marked the beginning of a new era in astronomy.

What makes neutron stars so fascinating is that they exist at the boundary between the familiar and the extreme. They are not as mysterious as black holes, whose interiors remain hidden behind event horizons, yet they exhibit physical conditions far beyond anything achievable in terrestrial laboratories. They allow scientists to study gravity, nuclear physics, magnetism and relativity under the most demanding conditions imaginable. Every new observation brings us closer to understanding the behaviour of matter at densities and energies that push the laws of nature to their limits.

So, in many ways, a neutron star can be thought of as a giant atomic nucleus floating through space, an object the size of a city, containing more mass than the Sun, spinning hundreds of times each second, powerful enough to bend light and warp spacetime, and still holding secrets that challenge some of the brightest minds in modern science!

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

These are ATLAS, CMS, ALICE, and LHCb.

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

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

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

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

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

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

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

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

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

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

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

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

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

The Higgs.

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

Multiple generations of accelerators looked for clues, and found…

Nothing.

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

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

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

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

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

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

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

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

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

Nothing.

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

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

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

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

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

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

It gave us better questions!

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Maldacena and Susskind condensed their shocking idea into these characters:

ER = EPR.

Which in plain English simply means…

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

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

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

Physicists began asking a new question.

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

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

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

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

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

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

No.

Has ER=EPR been proven?

Not yet.

Can we travel through a wormhole to another galaxy?

Almost certainly not.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

…Nobody knows.

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

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

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

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

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

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

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

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

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

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

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

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

… Nobody knows.

Although several possibilities do indeed exist.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

However, defenders of free will offer several responses.

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

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

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

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

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

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

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

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

A thought experiment about how advanced civilisations might preserve knowledge. Not through communication, but through persistence

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I’ve been thinking about the Fermi Paradox again recently, that slightly uncomfortable question about why, if intelligent life is likely in the universe, we don’t seem to have any real evidence of it.

For decades, the search has mostly focused on listening. Radio signals, communication, signs that something out there is trying to make itself known. So far, despite years of searching we have nothing definitive.

This got me wondering whether we’ve been looking for the wrong thing entirely. If you look at what we’re doing as a civilisation, there’s been a noticeable shift.

We’re getting very good at storing information by placing huge amounts of data in tiny physical space. We have materials designed to last for extremely long periods (fused silica, for example), and more recently, even starting to think about storing data off-world

There are already data payloads on the Moon, essentially early attempts at creating long-term archives beyond Earth. In a similar spirit, earlier missions like Pioneer 10 and 11 even carried engraved plaques, simple, durable messages intended to outlast the spacecraft themselves and potentially be understood by any intelligence that might encounter them.

Because we are sending these data stores to the moon, it feels like a subtle but important step, it suggests something quite different about where technology might be heading. Not outward and loud, but inward and durable.

So, I had this idea, and my thought is this:

What if advanced civilisations don’t broadcast signals, those huge technosignatures and radio communications that SETI have been searching for? What if they leave records instead?

Rather than trying to communicate across vast distances, they might create something that simply persists as a kind of long-term archive. If that’s the case, those archives would probably be small and compact. passive (no need for active power), and extremely durable, designed to last for very long periods, and possibly deliberately placed somewhere stable and discoverable.

If you were looking for a place to store something long-term in our solar system, Mars orbit actually starts to make a lot of sense.  It’s relatively quiet compared to Earth orbit as there is less atmospheric drag, fewer large perturbations, and a simpler gravitational environment overall. There’s also the added point that Mars itself likely had a very different past, thicker atmosphere, liquid water, maybe even early-life conditions. So, it’s not just stable, it’s interesting from a biological perspective.

From an engineering standpoint, there are a couple of obvious candidates. Higher Mars orbit (away from atmospheric effects and lower orbital decay), gravitationally stable regions like the Lagrange points (L4 and L5), where objects can remain relatively stable over long periods.

What would we actually see though? If something like this existed, I doubt it would look like a spacecraft in the way we tend to imagine it. It would probably be small. Passive. Unremarkable at first glance. Maybe the sort of things we’d need to look for are:

  • Small objects in unusual but stable orbits
  • Occasional bright reflections, glints, where light catches on a surface
  • Slightly odd thermal behaviour
  • Shapes or edges that don’t quite look natural

In other words, subtle anomalies. Nothing dramatic. Nothing obvious. Just things that don’t quite fit. None of this is especially speculative, it’s just basic orbital mechanics.

One of the most interesting parts of this idea is the possibility that we might already have the data.

We’ve been observing Mars for decades now, with high-resolution imagery, radar data. And thermal measurements, But, all of that work has been focused on the surface, not on systematically looking for small, anomalous objects in orbit. Which means there’s a gap. We might already have the data; we’ve just never really asked this particular question of it.

Is all this actually testable? The answer is yes, and that’s what makes this idea interesting to me.

It’s not just a thought experiment,. It’s something that could be tested, even at a basic level by taking existing Mars datasets and running anomaly detection on them. We can search for anything that looks odd or behaves in an unexpected way while filtering out the obvious stuff such as known spacecraft, debris, noise, etc.

Even if nothing turns up, we’d still learn something about what’s there, and what isn’t.

Why does this matter? I hear you ask. Well, If something like this did exist, even just one confirmed example, it would completely change the situation, because it wouldn’t rely on communication, It wouldn’t rely on timing or distance or whether anyone is still “out there”. It would just be… evidence. At that point, the Fermi Paradox wouldn’t really be about silence anymore, it would be more like: Have we simply not recognised what we’re looking at?

As a final thought, I’m not claiming that there are definitely extraterrestrial archives sitting out there in Mars orbit, but it does feel like one of those ideas that sits right on the edge between speculative and testable. And more importantly:

It’s something we haven’t really looked for.

Given how much data we already have, and how our own technology is evolving — it feels like a question that’s at least worth asking properly, because if those kinds of records did exist, we might not even realise we’re looking at them.

Hypothesis (for clarity)

Advanced extraterrestrial civilisations may prioritise long-term information preservation over visible energetic expansion, and may therefore deploy compact, durable archival systems in stable orbital environments, such as Mars orbit or associated gravitationally stable regions, where such artefacts could plausibly persist over extended timescales and be discoverable through systematic analysis of orbital data.

This is a simplified statement of the idea discussed above.