Monthly Archives: September 2026

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!

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

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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!

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.

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

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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.