Lothus MarqueMar 4, 2023
Katie Mack

‘The most common response I get when I talk about dark matter is: “isn’t this just something physicists made up to make the math work out?”
The answer to that might surprise you: yes! In fact, everything in physics is made up to make the math work out.’

My latest for BBC Science Focus:

https://www.sciencefocus.com/news/everything-physics-made-up/

Yes, everything in physics is completely made up – that’s the whole point

A physicist's task is to constantly create equations that keep up with our observations of physical phenomena.

BBC Science Focus Magazine
Mar 3, 2023 at 11:06pmMastodon for iOS
Show threadDavid ZaslavskyMar 3, 2023
@AstroKatie Haha I love that (and so true, too... I never really thought about it that way)
Show threadClemens aka dataMar 3, 2023
@AstroKatie even the math is made up to make the math work out 😁
Show threadStephaneWithAnEMar 3, 2023
@AstroKatie What do you mean that these things I see, hear and smell are numbers on a few scales that parts of our bodies register? :D
Show threadGeoff 🏴󠁧󠁢󠁳󠁣󠁴󠁿Mar 3, 2023
@StephaneWithAnE Whether they actually *are* numbers, rather than things that look suspiciously like numbers, is a bit philosophical. But it's *really* suspicious.
Show threadStephaneWithAnEMar 4, 2023
@_thegeoff Philosophically speaking, letters may not be able to accurately represent numbers! ;)
Show threadThree plus or minus fiveMar 4, 2023

@_thegeoff @StephaneWithAnE
They don't represent numbers. They represent continuua that relate to other continuua. x^2 + y^2 = 1 is not clue as to x and y; it's a description of a circle.

I know I’m being pedantic about a joke, but I think it’s useful insight

Show threadStephaneWithAnEMar 4, 2023
@ThreeSigma @_thegeoff Maybe "circle" is all there is and the maths is just an approximation or a way to talk about it? (I know, I know, I'm just continuing in the same line of thought)
Show threadThree plus or minus fiveMar 4, 2023

@_thegeoff @StephaneWithAnE
Yes. Or even that circles and other platonic objects don’t exist but are just useful fictions.

But the maths and other fictions have predictive power. So even if they are not real, they map to the real thing. So, it is in some way a valid representation of the underlying reality.

Science isn’t about discovering Truth. It’s about finding what works.

Show threadGeoff 🏴󠁧󠁢󠁳󠁣󠁴󠁿Mar 4, 2023
@StephaneWithAnE Not even Greek letters? ;)
Show threadStephaneWithAnEMar 4, 2023
@_thegeoff The answer is in the second word, "letter" :)
Show threadGeoff 🏴󠁧󠁢󠁳󠁣󠁴󠁿Mar 4, 2023
@StephaneWithAnE So represent π in numbers then. 😜
Show threadStephaneWithAnEMar 4, 2023
@_thegeoff It's technically possible but cannot be completed?
Show threadGeoff 🏴󠁧󠁢󠁳󠁣󠁴󠁿Mar 4, 2023
@StephaneWithAnE "π", however, includes all of it. In principle at least. The general idea of one particular infinity.
Show threadSimon BrookeMar 4, 2023

@_thegeoff @StephaneWithAnE irrational numbers (including π) ARE numbers. That, by definition, is what they are.

The fact that you cannot accurately represent them in figures is irrelevant; a purely lexical problem.

Show threadsimonbpMar 3, 2023

@AstroKatie I feel like planetary rings are both the proof and exception to that. Every time we think we understand rings, we discover something else that throws most of previous theories out the window.

E.g. Quaoar

Show threadJim ReaMar 3, 2023
@AstroKatie You were asking a couple of days ago about doing a public talk. You weren’t asking for topics but I think this would be an excellent one. BTW, if someone else asked how to do a good public science talk I would tell them to go watch Dr Katie Mack’s presentation to All Space Considered (Griffith Observatory) from a couple of years ago and just do what she did 👍
Show threadSunnJax 🌷🏳️‍🌈 Mar 3, 2023
@AstroKatie Thank you for posting here. I miss your cosmic thoughts.
Show threadGaryMar 3, 2023
@AstroKatie I want a refund and an apology for the Calculus class of fake math that desecrated me back in the 90s.
Show threaddecitectMar 3, 2023
@AstroKatie I’m a fan of math like I’m a fan of skydiving … leave it to others and just enjoy the aesthetics of others doing it!
Show threadTony FiskMar 3, 2023
@AstroKatie it just gets a little frustrating when there's nothing (yet) to back the math up.
Show threadKatie MackMar 3, 2023
@arfisk Not sure what you mean. Back it up with what?
Show threadTony FiskMar 4, 2023
@AstroKatie In relation to 'dark matter', corroborative evidence that distinguishes WIMPS from MACHOS. However neat the maths that describes them is, I'm unaware of any direct evidence for axions etc.
Sure, they explain what we observe, but can anything else? (eg normal unseen matter, or MOND)
Show threadclacke: exhausted pixie dream boy 🇸🇪🇭🇰💙💛Mar 4, 2023
@arfisk I think you are making the point of @AstroKatie 's article.

The label "dark matter" might be a bad name because it evokes the idea of something like WIMPs. But all dark matter is is a bunch of equations that fit with observations.

There isn't enough detail yet to allow philosophers, much less the general public, to say what dark matter "really is".
Show threadF.U. 🅭…Mar 8, 2023
@arfisk @AstroKatie
MACHOs and MOND are nearly ruled out, but BTW physicists don't like to mention that the W in WIMPs might be wrong too.
Baryons interact with 4 known forces.
Leptons: 3 (no strong).
Neutrinos: 2 (no EM).
It's entirely possible dark matter has NO weak interaction, which would make them literally undetectable except in the way we already have (observing their gravitational effect on "regular" matter).
Show threadBigsmiffyMar 3, 2023

@arfisk @AstroKatie

Apart from observation?

Just like Newtonian gravity

Show threadshac ron ₪‎Mar 3, 2023
@AstroKatie So physics is basically very slow machine learning?
Show threadclacke: exhausted pixie dream boy 🇸🇪🇭🇰💙💛Mar 4, 2023
@shac Physics works the opposite from machine learning as it seeks the simplest and most useful equation possible rather than an incredibly complex black box to throw observations into.

@AstroKatie
Show threadBigsmiffyMar 3, 2023

@AstroKatie

These same people
Newton, you just invented this thing called gravity to make the maths fit the observations. But you have no idea what gravity is.

Newton
Correct

Show threadPeterMar 4, 2023
@AstroKatie https://youtu.be/cxnwAJzMjts
Star Wars: Attack of the Clones | Younglings Help Obi-Wan Find Kamino | 4K HDR

YouTube
Show threadclacke: exhausted pixie dream boy 🇸🇪🇭🇰💙💛Apr 29, 2023
@petelind Private video. Do you remember what it was about?
Show threadMichael WymanMar 4, 2023
@AstroKatie those darn mathematicians just can’t work out the math without going to physicists to help make up stuff that makes it all work.
Show threadJens HannemannMar 4, 2023
@AstroKatie Paging Dr. Planck and Dr. Maxwell…
Show threadJesse SkinnerMar 4, 2023
@AstroKatie If you were to bet, what do you think the chances are that dark matter turns out to be an epicycles-type mistake/placeholder, ie. that we'll have some earth-around-the-sun moment that both blows our minds and replaces dark matter with something completely different?
Show threadKatie MackMar 4, 2023
@JesseSkinner Seems incredibly unlikely
Show threadPaul HayesMar 4, 2023
@AstroKatie I can't agree with "the equations [...] don't include a particle at all". Ignoring QFT for simplicity's sake...That abstract mathematical "wavefunction" is only part of the "fuzzy" probabilistic (https://arxiv.org/abs/quant-ph/0601158) description of a particle (https://www.math.ru.nl/~landsman/Nesta.pdf). The notion of "particle" has been defined more precisely and accurately but it hasn't been defined away. The fact that not all its measurable properties can be simultaneuosly definite doesn't imply it's not 'real'.
Quantum Probability Theory

The mathematics of classical probability theory was subsumed into classical measure theory by Kolmogorov in 1933. Quantum theory as nonclassical probability theory was incorporated into the beginnings of noncommutative measure theory by von Neumann in the early thirties, as well. To precisely this end, von Neumann initiated the study of what are now called von Neumann algebras and, with Murray, made a first classification of such algebras into three types. The nonrelativistic quantum theory of systems with finitely many degrees of freedom deals exclusively with type I algebras. However, for the description of further quantum systems, the other types of von Neumann algebras are indispensable. The paper reviews quantum probability theory in terms of general von Neumann algebras, stressing the similarity of the conceptual structure of classical and noncommutative probability theories and emphasizing the correspondence between the classical and quantum concepts, though also indicating the nonclassical nature of quantum probabilistic predictions. In addition, differences between the probability theories in the type I, II and III settings are explained. A brief description is given of quantum systems for which probability theory based on type I algebras is known to be insufficient. These illustrate the physical significance of the previously mentioned differences.

arXiv.org
Show threadStephen Bannasch (316 ppm)Mar 4, 2023
@AstroKatie would it also be reasonable to say everything in physics is made up to make our perception of reality work out.
Show threadDrew HerzigMar 4, 2023
@AstroKatie This is exactly what I want in a brief article - "Here's what we know at this point, and here's what we don't know - and why". Thank you!
Show threadKatie MackMar 4, 2023
@drewherzig Thanks!
Show threadColin RosenthalMar 4, 2023
@AstroKatie I don’t find this a useful way to think about it. The maths always works out, if it’s based on consistent axioms. That’s just as true for incorrect theories as for correct ones. A good theory is explanatory and predictive (and _correctly_ predictive of course). Not all scientific theories are mathematical either (evolution wasn’t, at least initially).
Show threadclacke: exhausted pixie dream boy 🇸🇪🇭🇰💙💛Mar 4, 2023
@gorhendad_oldbuck The full context of 'to make the math work out' is 'to make the mathematical models work out with the observations'.

Any sound mathematical model or system obviously works out with itself.
Show threadJack of all tradesMar 4, 2023

"Fundamentally, the entire point of physics is to create a model universe in math - a set of equations that remain true when we plug in numbers from observations of physical phenomena." - @AstroKatie

#physics #math

Show threaddynamicMar 4, 2023

@AstroKatie

This is why I think that evolutionary biology is a much more fruitful discipline for understanding fundamental truth.

The theory of evolution through natural selection has robust and generalizable explanatory power, enabling us to ask questions about "how?" and "why?"

Physics, as far as I can tell is fundamentally descriptive.

Show threaddynamicMar 4, 2023

The theory of evolution is generalizable enough that it can be usefully applied in simulated digital environments completely divorced from the kinds of physics that constrain physical universe.

The same cannot be said of Newtonian physics, relativity, or quantum mechanics.

Show threadDan HicksMar 4, 2023
@AstroKatie
:: philosophy of science intensifies::
Show threadStrange New Words (Adam)Mar 4, 2023
@AstroKatie Ether was a theoretical substance that made the math work, but it didn’t really exist — we just didn’t understand light and electromagnetic waves yet. Similiarly, I think people feel that dark matter, a substance that by definition can’t be directly observed or detected but makes the math work great, is a little convenient. It feels like a concept that may be dropped when we learn more about the universe’s true nature (assuming we ever do).
Show threadnickjMar 5, 2023
@AstroKatie including the epicycles
Show threadKatie MackMar 5, 2023
@nickj Are you referring to what I said about epicycles in the piece?
Show threadjollyrogueMar 5, 2023

@AstroKatie I’ll add that to the times I got in trouble in school. Instead of being steered towards theoretical physics I get told I can’t make up things up to make the problem work. 😒

🥸
@mwl

Show threadStephenCMar 11, 2023
@AstroKatie
It is weird how the basics of science get cooked into conspiracy theories.
Show threadStegosaurusApr 28, 2023
@AstroKatie And the math comes from what we CAN see. Hmmm. Maybe dark matter should be renamed universal fudge, as in fudge factor.