{"id":24411,"date":"2023-03-03T08:00:53","date_gmt":"2023-03-03T07:00:53","guid":{"rendered":"https:\/\/www.sciencefocus.com\/?p=138256"},"modified":"2023-03-03T09:36:37","modified_gmt":"2023-03-03T08:36:37","slug":"yes-everything-in-physics-is-completely-made-up-thats-the-whole-point","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/rss_feed\/yes-everything-in-physics-is-completely-made-up-thats-the-whole-point\/","title":{"rendered":"Yes, everything in physics is completely made up \u2013 that\u2019s the whole point"},"content":{"rendered":"

A physicist’s task is to constantly create equations that keep up with our observations of physical phenomena. <\/p>

By Dr Katie Mack\n \t\t<\/p>

Published: Friday, 03 March 2023 at 12:00 am<\/p>

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Researching a cosmic mystery like dark matter<\/a> has its downsides. On the one hand, it\u2019s exciting to be on the road to what might be a profound scientific discovery. On the other hand, it\u2019s hard to convince people it\u2019s worth studying something that\u2019s invisible, untouchable, and apparently made of something entirely unknown.<\/p>\n

While the vast majority of physicists find the evidence for dark matter\u2019s existence convincing, some continue to examine alternatives, and the views in the press and the public are significantly more divided. The most common response I get when I talk about dark matter is: \u201cisn\u2019t this just something physicists made up to make the math work out?\u201d<\/p>\n

The answer to that might surprise you: yes! In fact, everything in physics is made up to make the math work out.<\/p>\n

When I first got into science, what excited me was the prospect of learning some ultimate truth about the Universe. Stephen Hawking once described cosmology as an endeavour to \u201cknow the mind of God\u201d.<\/p>\n

But while that characterisation is inspiring, in practice, physics isn\u2019t built around ultimate truth, but rather the constant production and refinement of mathematical approximations. It\u2019s not just because we\u2019ll never have perfect precision in our observations. It\u2019s that, fundamentally, the entire point of physics is to create a model universe in math \u2013 a set of equations that remain true when we plug in numbers from observations of physical phenomena.<\/p>\n

For example, Newton\u2019s second law of motion, which says that force equals mass times acceleration, is a mathematical model that tells us that if we measure the force exerted on an object, in appropriate units, we should get the same number as the product of the object\u2019s mass and the acceleration it experiences when subject to that force.<\/p>\n

In Einstein\u2019s version of gravity, general relativity, the equations get far more complicated, but the goal of the exercise is the same. There\u2019s always a level of abstraction built into the effort because what allows us to make predictions or design new technologies is a set of equations that can be written down and calculated, not a philosophical discussion on the nature of reality.<\/p>\n

This level of abstraction is especially apparent in particle physics, because the existence or non-existence of a single particle on a subatomic scale is a rather fuzzy notion. The equations describing the motion of an electron through space don\u2019t actually include a particle at all, but rather an abstract mathematical object called a wavefunction that can spread out and interfere with itself.<\/p>\n

Is it ever true, then, to say that an electron is \u2018real\u2019 when it\u2019s in motion? If we believe that electrons are real things, have we just made up the wavefunction to make the math work out? Absolutely \u2013 that was, in fact, the whole point. We couldn\u2019t get the equations to work if the electron was a solid, isolated particle, so we made up something that wasn\u2019t, and then the numbers started making sense.<\/p>\n

It may be that in the future, we find some solution that we prefer to a wavefunction and we abandon that concept altogether. But if we do, it will be because the math stopped working out: we\u2019ll have some experimental or observational result that doesn\u2019t add up when we put the data into our current equations. Then, if we\u2019re doing our jobs right, we\u2019ll find a new set of equations that better describe the electron\u2019s behaviour, and we\u2019ll give those equations names and conceptual analogies and textbooks will be written saying \u201cthis is what\u2019s really happening.\u201d<\/p>\n

A scientist\u2019s notion of what\u2019s really happening is always driven by the math. Before it was accepted that the Earth orbits the Sun<\/a>, astronomers used epicycles \u2013 little orbital loops \u2013 to describe planetary motions in an Earth-centred system. This construction is often used, a little unfairly, as a prime example of \u201cmaking up something to make the math work\u201d going wrong.<\/p>\n

While it\u2019s true that we abandoned epicycles in the 17^{th<\/sup> century, it was the math that made us do it. Newton\u2019s equations of universal gravitation and Einstein\u2019s general relativity are not made of stronger stuff than the old equations of epicyclic motion \u2013 all these frameworks are just symbols on a page \u2013 but they fit the observations better and make predictions easier, so we use them as the basis of our abstract model universe.<\/p>\n}

Dark matter, dark energy, cosmic inflation, black hole singularities, and all the other hypothetical denizens of our current cosmology might seem less real than falling apples or electricity or fluid flow because we don\u2019t experience them in our everyday life, but from a physicist\u2019s perspective, they\u2019re all equally good fodder for mathematical abstraction.<\/p>\n

While the way we observe something determines what kind of data points we can use, in the end, everything we do is to make the math work out. We certainly hope that all this calculating brings us a better description of reality, but the mind of God is best left to the philosophers; we don\u2019t have an equation for that.<\/p>\n