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points by throw0101c 4 days ago | 0 comments

When Kepler published his models:

* https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_m...

People did not understand how or why they worked, but they switched over to them from the Ptolemaic (Tychonic, etc†) system anyway because the math was easier. It was only later (Newton, Einstein) that we understood the "why" and "how".

† https://tofspot.blogspot.com/2013/08/the-great-ptolemaic-sma...

[–] advisedwang 3 days ago

Kepler did understand the data he had, where it came from, what his laws were claiming, how to verify that the data fits the laws, how the data dis-proves heliocentricity etc, which is really what the article is talking about.

[–] throw0101c 3 days ago

Kepler's models showed that the planets travelling in elliptical orbits matched observations, but Ptolemy (and Brahe, etc) also produced models that (tried to) match observation.

If Kepler's models explained the how and why, why were Newton and Einstein necessary?

[–] dfabulich 3 days ago

Newton and Einstein answered "how" questions with more generality and more precision.

Kepler's model predicted the behavior of the planets, and so does Newton's model, but Newton's model is more general, applying not only to planets, but also to apples, cannonballs, trains, and other objects with mass.

Einstein's model is more accurate and precise than Newton's model, especially about the orbit of Mercury. Einstein's model also predicts gravitational lensing (e.g. during eclipses), which Newton's model doesn't.

"Why" questions are very hard for physicists. Generally, when we ask "why" questions, we're asking what prior Event X caused Event Y. But for universal laws, there is no prior event that caused the universal law to be true. The best we get is more generality. Planets orbit the sun for the same reason apples fall to the earth, but we don't know why gravity happens, only how. Magnets resist each other for the same reason the floor is hard, but we don't know why magnetism happens, only how.

[–] throw0101c 3 days ago

> "Why" questions are very hard for physicists.

Yup:

* https://en.wikipedia.org/wiki/Principle_of_sufficient_reason

[–] colonwqbang 3 days ago

On this topic: Feynman "Why do magnets repel?"

https://youtube.com/watch?v=MO0r930Sn_8

[–] whatshisface 3 days ago

Newtonian mechanics doesn't explain the why of itself, it explains why Kepler's laws are true, an explanation that won't make sense if you don't know what Kepler's laws are saying, and which won't hold any significance to you if you don't know why Kepler's laws are thought to be true.

[–] bpshaver 3 days ago

Weren't Kepler's models worse at prediction, at first? We adopted them because they were more parsimonious.

[–] hocusPokeUs 3 days ago

This is just going to devolve into more tribal elders pontificating to be possessed of knowledge the average person won't be able or allowed to falsify; the expert can clearly see how their interpretation is correct and it's disrespectful to challenge elders nonsense

Tao and such are merely biological beings serving biological imperative to survive. Educated as they are they are well aware social society expects them to engage in knowledge role-play to barter for food

The recursive non-fractal nature of reality where "function exits" when a human dies naturally fosters signal attenuation and the formation of new spoken traditions among the future generations

There is no propagating our social ways 100 years into the future. We can only propagate our material outputs. The semantics we define to describe something are lost to time.

The provenance to future people was past people; that's all that matters in the future not how we communicated together now

[–] VikingCoder 3 days ago

> how to verify that the data fits the laws

What? He worked meticulously to match the observations.

I don't understand your claim here at all.

[–] MillironX 4 days ago

When the article brought up the cancer drug analogy, I thought roughly the same thing. We still don't know why certain drugs work (take gabapentin as a prime example), but we're still comfortable using them on a regular basis.

[–] matheusmoreira 4 days ago

Yeah. Medical practice is often based on purely statistical statements like "in case of A associated with conditions B if you do C you'll help D% of the patients". Sometimes looking up a drug's mechanism of action yields nothing, literature just says it's unclear and gives us some educated guesses if we're lucky. Makes me a little sad that medicine has been reduced to this instead of the romantic "understand how the body works, how it fails and how to fix it" ideal.

[–] melagonster 4 days ago

Not so bad, I sure doctor know how diabetic work usually.

[–] paulus_magnus2 3 days ago

Kepler did make progress - he showed that equal area covered by the planet on the orbit implies that the orbits are elliptical (and vice versa). Enough progress for the next guy to take it further.

The next guy was Newton - he knew the solutions to a central force problem (thanks to his invention of Calculus - notation for calculating with infinitesimals). Movement with conserved angular momentuum <=> movement with the equal-area property <=> happens for a force ~1/r^2. From that he concluded that the central force is "gravity". The deriveration is simple enough for 1st semester physics student, but you will need to cleverly change variables once or twice to get a familiar integral.

https://en.wikipedia.org/wiki/Central_force

https://en.wikipedia.org/wiki/Classical_central-force_proble...

[–] the__alchemist 3 days ago

> thanks to his invention of Calculus

Nonsense! It was pilfered.

[–] throw0101c 2 days ago

Leibniz enters the chat:

* https://en.wikipedia.org/wiki/Calculus#History

[–] godelski 3 days ago

I'd be careful with the inference you're making here. Tbh we could easily conclude that neither Newton nor Einstein explained "why". One could argue we still don't know and won't even after we have a TOE.

I'd take Asimov's "Relativity of Wrong" here. And I also think there's motivation for why scientists care so much about elegance.

[–] datsci_est_2015 3 days ago

> And I also think there's motivation for why scientists care so much about elegance.

It's an intuition you build pretty early on in science courses in undergrad, somewhat related to Occam's Razor. It's why the optimal packing of 11 squares[1] is so unsatisfying. It flies in the face of all the intuition we've built that simple (and symmetric) solutions are more likely to be true. Machine learning practitioners use this intuition when performing model selection as well: the simpler model (i.e. with fewer free parameters) is less likely to be overfit to the data.

[1] https://en.wikipedia.org/wiki/Square_packing#/media/File:Pac...

[–] godelski 3 days ago

  > It's an intuition you build pretty early on in science courses in undergrad

I think this intuition is much harder to reach than many think, which causes the frequent over confidence [0]

  > It's why the optimal packing of 11 squares is so unsatisfying.

Idk, maybe one of those "beauty is in the eye of the beholder" kinda things?[1]

[0] https://m.youtube.com/watch?v=hV41QEKiMlM

[1] https://pingyou.com/papers/eleven-squares.pdf

[–] datsci_est_2015 2 days ago

Does your [1] link not simply prove my point that humans will search for something satisfying symmetric given a result that is less satisfying and less symmetric?

"Beauty is in the eye of the beholder" - but let me just quickly find an alternative representation of the solution that is much more symmetric and satisfying. There, "beautiful"!

[–] godelski 1 day ago

Yes, but that "satisfying symmetric" (I'd say elegant since symmetry isn't required) is meaningful and finding these elegant solutions has been shown to be important for solving further problems. Math and physics aren't as concerned with the answer as they are with understanding

[–] throw0101c 3 days ago

> I'd be careful with the inference you're making here. Tbh we could easily conclude that neither Newton nor Einstein explained "why". One could argue we still don't know and won't even after we have a TOE.

Why be careful? What would be wrong with that conclusion (if it's true)? I'm comfortable with arriving at ambiguity:

* https://en.wikipedia.org/wiki/Principle_of_sufficient_reason

* https://edwardfeser.blogspot.com/2023/04/what-is-law-of-natu...

[–] godelski 3 days ago

I think Feser makes part of the argument for me (though it is clear he isn't a physicist) though I'd encourage you to read Asimov's argument.

There's the metaphysics problem in that all models are wrong. There's more than one competing version of physics (as will help you read Asimov's argument/rant). There's many valid ways to interpret "why" something happens. Physics is trying to understand the causal change of events so that we can generate a model that makes strong and accurate counterfactual predictions. Were that type of model "complete" would we have answered "why" things happen? Depends which "why" you're asking. You could still proclaim, as Fesser notes, "that's the rules God made", which isn't meaningfully different than "that's the way it is".

As for the PSR I'd claim everything does happen for "a reason". But is that reason always knowable? Certainly not. And arguably my namesake proved that there can't ever be any fully complete physics model.

So why be careful? Because my responses are limited, you must ask the right questions. ;)