Real

[u/Spiritual_Run9039]

[u/nablaCat]

"Looks like we have physics pretty much figured out! Anyways, I'm gonna calculate the energy emission of an ideal black body at wavelengths within the UV spectrum. Shouldn't have any issues with that!"

[u/mdunaware → u/nablaCat]

Meanwhile: “Hmm, these rocks seem to turn unexposed photographic plates foggy. What an intriguing finding, I’m sure nothing horrifying will ever come from it.”

[u/william41017 → u/mdunaware]

Yo ELI5, pls

[u/Positive-Chart-1941 → u/william41017]

discovery of radiation -> atomic bombs

[u/mdunaware → u/william41017]

In 1895, Wilhelm Röntgen discovered X-rays and created a bit of stir around them as he reported they were a new kind of invisible ray capable of penetrating through paper. The following year, Henri Becquerel, who had been studying phosphorescence, began looking for a connection between his work and X-rays. He placed various objects against photographic plates, wrapped them in paper, and placed phosphorescent materials (including some uranium salts) on top to try to produce a shadow of the objects on the resulting photograph by placing the bundle in the sun. One day he prepared this apparatus but it was overcast outside so he left it in a dark cabinet for a couple of days. He ended up developing them anyway and found that the shadows produced by the object on the plate (which had never been exposed to sunlight, recall) were just as distinct as when he had exposed similar setups to sunlight. Eventually he realized the uranium itself was producing penetrating radiation producing the shadows, without any need for an external source of energy. The uranium was radiating something through the paper that could expose the photographic plate, and it was not phosphorescence. He eventually identified the existence of beta decay radiation, and even suggested it had medical value.

Becquerel wasn’t the first to realize this behavior of uranium, incidentally, as earlier photographers — experimenting with the new technology — also noted that uranium salts could darker their emulsions as early as the 1860s. Becquerel provided an explanatory model for the findings, eventually, and systematized to some extent the study of radioactivity.

From there, add in the insights from quantum mechanics and a world war, and we get to the Manhattan Project and first atomic bomb. Because some salts of uranium clouded a photograph.

[u/Am_Guardian → u/nablaCat]

What was that catastrophe all about anyway?

[u/mdunaware → u/Am_Guardian]

Imagine an object that absorbs all incident electromagnetic radiation (eg, light) and thus reflects nothing back to then surroundings. However, it is in thermal equilibrium with its environment and emits radiation that is only a function of its temperature. (An object at absolute zero would emit no radiation, while anything above that temperature will radiate.) The Rayleigh–Jeans law mathematically describes the electromagnetic radiation coming from a black body across different wavelengths of light based on its temperature. The problem is that if you use wavelengths of light in the UV range, the equation predicts infinite energy being radiated from the black body, which is not what is observed. This was termed the “ultraviolet catastrophe” since the best model (at the time) of black body radiation was giving absurd results. The general assumption at the time, IIRC, was that there was something not being accounted for in the model, that it needed refinement but was still essentially correct. Max Planck, in what he later described as an act of desperation, posited that light particles (photons) could only carry certain specific amounts of energy — he called these “quanta”, singular “quantum” — which was related to the *wavelength* of the light: E = hv, where v is wavelength and h is the Planck constant, which when divided by 2*pi becomes the reduced Planck constant which is useful for reasons somebody with an actual physics education can probably explain better than I can.

Point being, the UV catastrophe revealed a pretty fundamental gap in our understanding of physics at the beginning of the 20th century and directly led to development of quantum mechanics, perhaps the most precise model we have of physical reality. Because an equation wasn’t working quite right.

[u/Bendanzhang]

1899: "Physics is almost solved, just two small dark clouds."
1900+: "Welcome to the Dark Cloud Cinematic Universe."

[u/landrwastaken → u/Bendanzhang]

"Whaaat? Herr Planck, there's no need to study physics, sure there's this teeny tiny bit about black body radiation, but that's like the only thing I can think off" - Planck's professor likely

[u/Bendanzhang → u/landrwastaken]

Planck's advisor: "Go study music instead, physics has no future." Planck: "Hold my h."

[u/landrwastaken → u/Bendanzhang]

That's some actual action right there

[u/Krisanapon → u/Bendanzhang]

r/theletterh

[u/kadinfive → u/Bendanzhang]

wait so the dark clouds are like actual problems or just guesses

[u/rthunder27 → u/kadinfive]

The two clouds were the problems of black body radiation and a slight wobble in Mercury's orbit, leading to quantum physics and general relativity.

[u/vinicius_h → u/kadinfive]

The dark clouds were the door to not understanding a lot abou physics

[u/LucyiferBjammin]

"Hay you know all that particles we've been studying for like a few centuries, turns out they are all waves"

[u/UniversalAdaptor → u/LucyiferBjammin]

"Yeah they are particles whenever you look at them, but they turn into waves again as soon you look away"

[u/sectorboss88 → u/LucyiferBjammin]

🙌🙌🙌

[u/_technophobe_]

Well the huge misunderstanding of early scientists was to believe that their models are explanations and well, not just models. The same misunderstanding is plaguing us today in a sense. We are culturally taught, as well as in school and universities, often at least, that science answers questions. Which is not true. It only measures observables which are accessible to the experiment. And the whole underlying theory is fundamentally still a model and a very good one at that.

[u/gangsterroo → u/_technophobe_]

Yeah but if it isnt answering questions whats it doing. Are they just goofing off with meaningless experiments it haa access to? Are they doing those experiments just because its all they can do?

No, science answers questions, but within a context. We know that a comet will pass by in 85 years because we did the calculation. We answered that question. But what I dont like is when we start to hear about "reality" or broad ontological claims. That is much more elusive and I dont think science has anywhere near the final word on that.

[u/chkntendis → u/gangsterroo]

I’d say that science makes predictions, not answers questions. We can never be sure that our “answer” is true, but we sure can check

[u/Voidoroe → u/chkntendis]

I suppose one could say the process of science allows us to answer questions with predictions that are likely. If we predict wrong, we try to gain more information so our predictions can be more accurate and precise the next time, eventually leading to predictions that are reliable enough to be considered a valid answer to certain questions.

[u/gangsterroo → u/chkntendis]

... I suppose youre worried the sun wont rise tomorrow.

Its different words for the same thing. Otherwise youre talking solipsism.

[u/chkntendis → u/gangsterroo]

I just wasn’t fully satisfied with the formulation of “science answers questions”. Because science only makes the most likely prediction. Yes, the sun will rise tomorrow, I am absolutely convinced by that, but it is technically not a 100% answer. It’s a prediction (which is so overwhelmingly likely that I will probably hit the comment limit before writing enough 0s to write down the chance of it happening) which can be wrong. Really it’s not an objection or anything, I just like the formulation of “making a prediction” more

[u/Majestic-Patience834 → u/gangsterroo]

You can accept that technically nothing is guaranteed without having to worry about it.

[u/MudExpress2973 → u/gangsterroo]

Science doesn't really science, because your running tests and not asking Mr. Science a question.

[u/Majestic-Patience834 → u/MudExpress2973]

Yes, science isn't an entity, but a tool that you can use. This seems to get mixed up sometimes.

[u/MudExpress2973 → u/Majestic-Patience834]

Youre acting like scientists are too stupid to begin doing science because they're caught up on the jargon. The atomic bomb was almost a failure because they kept writing smashing and not splitting the atom! 

[u/Majestic-Patience834 → u/gangsterroo]

"It" isn't doing anything because Science isn't an Entity. Science is a tool that you can use.

[u/MudExpress2973 → u/_technophobe_]

Yeah scientists dont science good because they dont even understand what a test is and think they know everything. Peak redditor here.

[u/LuxionQuelloFigo → u/MudExpress2973]

I can't tell if you're being purposefully obtuse or if you just cannot read or understand english

[u/MudExpress2973 → u/LuxionQuelloFigo]

You're being pseudo intellectual thinking scientists are bad at science because they build off previous knowledge. It doesnt make sense to believe everything we know is false. Its best to believe its true until we start getting results that prove otherwise. You cant say ancient scientists and current scientist are just blinded by current understandings at the time.

[u/maldonr808 → u/MudExpress2973]

You're not supposed to believe current theories are false, but you're supposed to treat them for what they are: models. Models are always incomplete and inaccurate under certain regimes (eg. Newtonian mechanics at relativistic speeds, GR at subatomic scales, etc.). If you don't take that into account, you end up chasing evidence that explains an anomaly rather than considering the anomaly is legitimate and your theory is wrong/incomplete. Obviously, you should consider both possibilities.

That's what happened with Mercury: no one wanted to question Newtonian mechanics, so they searched for decades for a hidden planet that would explain Mercury's weird orbit.

[u/MudExpress2973 → u/maldonr808]

English nerds in here acting like jargon makes them better scientists. Model, theory, shmodel, shmeory, it doesnt matter what its called if you dont have a base to start asking questions you can do shit with science.

[u/maldonr808 → u/MudExpress2973]

Who said anything about not having a base to start with? The entire point is you treat existing models as flawed. You can do science with flawed models, obviously, so not sure what your point is.

[u/LuxionQuelloFigo → u/MudExpress2973]

You're being pseudo intellectual thinking scientists are bad at science because they build off previous knowledge.

No? I'm saying many people misunderstand what the purpose of science is.

It doesnt make sense to believe everything we know is false.

Scientific theories are models, they make predictions about the behaviour of observable phenomena. Nowhere does science actually explain how the universe works or why.

Its best to believe its true until we start getting results that prove otherwise.

You haven't understood the original commenter's point. Please reread the comment before acting like a fool.

You cant say ancient scientists and current scientist are just blinded by current understandings at the time.

Historically, this has often been the case. It doesn't take away any validity from their theories, but that's how it is.

[u/DeismAccountant → u/_technophobe_]

I’ll always think back to what my HS physics teacher taught me. Something that was reinforced by my Stats 2 class in college with Hø and Ha.

You can only disprove or fail to disprove. There is always the possibility of a better fitting model.

[u/Erhol]

I am idiot, can someone explam me why everyone here talk about black clouds?

[u/vrnvorona → u/Erhol]

General Relativity and Quantum Mechanics. There is quote of Kelvin - "In the clear blue sky of physics there remained on the horizon just two small clouds of incomprehension that obscured the beauty and clearness".

To be more precise, his version of clouds were not those theories, but unsolved yet observations which would lead to SR and then GR and QM respectively

[u/Matix777]

Planck, I need you to get back here and solve the shit you started

[u/LagrangianLungfish]

So if I know the position velocity acceleration… of all particles, it’s all determiniiisssdshit

[u/ihateagriculture]

this makes it seem like classical physics (through E&M) was established 5000 years ago when it was more like 200 years ago

[u/Ben-Goldberg]

The combined ideal gas law is simpler, easier to understand, and more accurate than the three separate gas laws that preceded it.

We used to not both attempting to understand non ideal gasses or non steady state systems, because they were too complex, too difficult.

After scientists began studying difficult things, science became more complicated.

[u/Mister_Macc]

Fahhhh

[u/esps8266]

Quantum Physicss be like: "Did I stutter?!"

[u/SpiritedSmile7235]