What does physics still have left to answer?

This question is intentionally broad, but why aren’t we done with physics, why is it when we live in a world where we have enough knowledge of physics to get us through day to day life, we still push to learn more?

Elon Musk famously only employs engineers and not physicists because he thinks that physics is advanced enough to do everything he wants to do, the engineers now must find a way to apply that. That’s what engineering is, taking abstract things such as maths and physics and finding a way to put them to use.

We advance our knowledge of chemistry and biology for obvious reasons, they’re useful in everyday life, small scale, human scale. Why do we still push to know more about stars millions of lightyears away? Why do we want to know what happens when particles, that we don’t even have the technology to see, interact? Other than medical physics, what real use does physics have now we’ve advanced this far?

I know these questions sound narrow-minded and even almost a little idiotic, but they lead onto bigger questions… Why do we pursue knowledge? Why do we want to know things just because we want to know them? To an even more vague extent, what makes us curious?

These are the kind of questions where even if you ask 100 physicists, you will get 100 different answers. Everybody has a slightly different reason for wanting to know the secrets of the universe, and before I explore my reasons behind enjoying the pursuit of knowledge and some alternative reasons, I think it would make sense to first answer the question “What does physics still have left to answer?”. And it’s important to note now that this isn’t a lecture, I’m not going to break down the maths and the fundamental laws behind all of this (I can see you’re upset about that… maybe next time), this is more just a way to present some ideas and maybe spark an interest within you to go and look into some of these questions more.

Let’s start with the obvious, the so-called ‘Theory of everything’ – famously sought after by the esteemed cosmologist Stephen Hawking. With modern physics, we can write equations and make predictions on basically everything the issue arises when we compare the everyday world, our realm, to the world of very, very small things, the quantum realm. When you break everything down to fundamental particles, things get weird. Photons colliding with other photons, and electrons slamming into neurons don’t behave under the normal confines of an elastic collision.

This difference was brilliantly described by a physicist who’s name escapes me and I can’t seem to find, possibly one of the people working at the Large Hadron Collider (LHC) James Beacham, he described collisions of quantum particles like being a head-on car crash, whereupon impact, the cars disappear, turn into two bikes, then disappear again two skateboards shoot off in opposite directions perpendicular to the line of the impact.

So, what the theory of everything is, is a theory that allows us to connect these two realms by some sort of equation, a numerically quantitative way to view the entire universe from beginning to end.

Another well-known, almost infamous theory is the multiverse theory; the theory that there exists an infinite number of universes. To any sci-fi fans, the idea of infinite parallel universes where every situation and possibility has occurred and will occur should not be alien. However, this isn’t the only way a multiverse could occur, there could be an infinite number of universes identical to ours, it isn’t likely, but if you placed a bet 13.8 billion years that you would be sat here reading this today, that would have infinitesimally small odds too, so when you get to infinity, most rules of bookmaking go out the window (and out of an infinite number of windows).

The most fascinating part about this, to me, is that there is no guarantee that any other universe out there will even have any mathematical similarities to ours whatsoever. You could visit another universe and gravity wouldn’t be a thing there – or oxygen. Just because something is so fundamental in our universe, doesn’t mean it transcends across to all the others.

I think there is one more thing that I would like to point out about the parallel universe theory, and it’s a misconception that you see almost everyone make. Just because something is infinitely repeating, does not mean that every possible arrangement of its constituent parts is a given fact. As I mentioned previously, there could be an infinite number of universes all identical to ours.

Another way to express this in more familiar terms to most people is to look at the transcendental number pi. Most people know that Pi is irrational (it cannot be written as a fraction p/q ) and infinitely repeating. Every pattern that we have looked for in pi, we have found, for example, at position 768, we reach the “Feynman point” where we find six “9”s in succession, and at positions 60 you find the number 0-9 in an arbitrary order (then you find them again in the correct order at position 17,387,594,880). But just because we have found every pattern that we have looked for, does not mean that we will find every future pattern we look for. 

I saw it speculated on the internet a few years ago that if pi was infinite then at some point, if you take all the numbers in order and group them correctly, you will be able to use them to create the “RGB” values for a snapshot of time, for any given moment, which is an incredible thought… but it just isn’t true. We know pi to 31 trillion digits (nowhere near enough to create that aforementioned animation of the progression of spacetime) but as far as we know, we could get to digit number 32 trillion, and pi could just repeat itself 141592643… etc. So, you cannot assume that an infinite number of repetitions will guarantee every infinite number of possibilities will be covered. 

What’s the matter? Well, the truth is nobody really knows for sure… We define matter as anything that has volume and mass, so a quark has volume, but why? What makes up the volume of a quark? It’s a fundamental particle, but is it? There’s the theory of point particles called “Preons”, these make up the quarks and leptons that we deem fundamental, now the reason this is so controversial is because, by definition, a point doesn’t have a volume or a mass, but in the case of the preon it makes up something that does, so how can something with a mass and area, a volume, a width, a height and a length, make up something with a quantifiable mass and volume?

And finally, we move onto turbulence, now by its very nature, turbulence is unpredictable, it’s governed by chaos, turbulent flow is the polar opposite of laminar flow, and personally, I don’t know which I prefer. We are probably all familiar with the experience of turbulence from being on aeroplanes, turbulence is just the flow of a fluid when impacted by chaotic changes in pressure and flow velocity. The more viscous a fluid is, the more velocity and pressure it can have before the predictability becomes nullified. So, for something like not viscous at all, like air, it’s pretty easy for turbulence to occur in a way that would disrupt the smooth flight of a Boeing 747.

Now the thing is, we can give ourselves some inclination into when turbulent flow will occur by using the Reynolds number (named after Osborne Reynolds – although he wasn’t the one to discover it, he was the one to popularise its use, it was actually introduced by George Stokes in 1851). The Reynolds number is denoted “Re”, and is found using the equation below:

Reynolds number


ρ = fluid density 

u = flow speed

L = linear dimension

μ = dynamic viscosity of fluid

v = kinematic viscosity of fluid.

The higher the Reynolds number the more the flow tends to be dominated by turbulence. You can look more into this if you want to know about turbulence in pipes, turbulence in stirred fluids and more complex systems, but at its core, turbulence is unpredictable, and as we don’t have an equation to predict the movement of a particle within a turbulent fluid, over a given time. Turbulence is just one more question that physics has yet to answer.

But I suppose this doesn’t really answer the question of why we want to know these things even though they don’t all have obvious uses in our day to day lives. Which is quite funny, actually, because that is a question that psychology can answer, and it’s quite simple at its core, we’re asking why we are curious? 

Curiosity isn’t just a human virtue, it spans across all sentient life, but most mammals lose their sense of curiosity as they leave their adolescent years. Curiosity is the thing that we use to teach us basic skills. Curiosity is what drives a baby lion how to hunt before it understands the harsh reality of starvation, curiosity and practice is how cats learn to catch birds. Animals do still keep their curiosity as they get older, but ultimately it is an innate behaviour in mammal children, but we can thank a particular trait called neoteny for the fact we keep our curiosity well into our adult years. 

As defined by the BBC, neoteny is a term that means the “retention of juvenile characteristics” – and it is what makes us, as a species, more child-like than some of the other creatures in our class of Mammalia.

However, I don’t like to mix physics and psychology so I will draw this one to a close here.


Published by Ryan

Information geek || maths enthusiast.

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