A theoretical physics FAQ
mat.univie.ac.at
mat.univie.ac.at
If I want to calculate the efficacy of relativity where can I find observational data on mercury's orbit?
If I want to calculate the efficacy of quantised photons where can I find observational data on blackbody radiation?
If I want to calculate the speed of light where can I find observational data on io?
If I want to calculate the efficacy of quantum mechanical models where can I find observational data on qm phenomena?
Are there resources of others showing from experiment to theory with calculations of real data defending the theory's math
Or even just access to these and similar datasets?
> you don't "calculate the efficacy of [a theory]"
How would you describe in a single sentence the growing precision of our calculation of the speed of light constant over the last 300 years?
> data don't "defend the theory's math"
How would you describe in a single sentence the way Einstein used Mercury's retrograde motion to assure himself of the advocacy of his theoretical mathematical model for gravitation?
I don't know, first I'd talk about how it was discovered that light behaves like c really is a constant (that's not intuitive nor trivial). You could guess from Fizeau (1851) and Michelson-Morley (1887) experiments, but it wasn't really until the 1905 Einstein's paper that it was understood that you don't need aether, the speed of light can (and should) be a universal constant and it all makes sense.
>How would you describe in a single sentence the way Einstein used Mercury's retrograde motion to assure himself of the advocacy of his theoretical mathematical model for gravitation?
He shows (see here: http://www.gsjournal.net/old/eeuro/vankov.pdf) that his theory (after reasonable approximations) predicts a precession of the perihelion of Mercury that agrees with the experimental result, then he stops. That's what you do in Physics: look, my nice theory predicts this observable in agreement with the experimental data. That's a very good sign, but the data could be explained by other theory as well. Data can "prove" that a theory is wrong (if your theory has falsifiability, as it should), but they can never show that your theory is all that there is, nor your maths... There are other theories of gravitation, for instance Logunov's, that are interesting and agree with data (more or less) but have a few problems with maths.
BTW, I don't think he ever really doubted his GR theory, it comes from a very simple, yet profound idea that once realised had to be right. You have to do all the technical work afterwards, that was difficult, but a few mathematicians could have done/did it (Hilbert). In any case the idea is to check your predictions with the measurements from more and more precise experiments to find out if you're wrong, not the other way around (that... well, I've met that funny epistemology a few times in social sciences.)
> Data can "prove" that a theory is wrong (if your theory has falsifiability, as it should), but they can never show that your theory is all that there is, nor your maths.
Where you got '"prove"' and 'all that there is' I am unsure
My wording was:
op> how well different theoretical models express experimental data
Which mirrors your own reiteration of that point
> the idea is to check your predictions with the measurements from more and more precise experiments
Which is literally what I was asking for: measurements from .. precise experiments
> predicts a precession of the perihelion of Mercury that agrees with the experimental result
Right, where's the experimental data on the orbit of Mercury?
If you are unable to answer the question that's fine but as is I fail to see what you are trying to accomplish with your ire and misdirection
If you're interested in the data you can browse the references, go to the libraries (as physicists have to do even at college, because it's kind of hard), find out first what exactly you are asking... even mail someone. And you can also measure things by yourself, this is a free universe and everybody can study its properties (Mercury is out there and maybe you can afford a nice telescope). What is unreasonable, very unreasonable, self-entitled in my opinion, is expecting that experimental physicists provide some kind of repository of (internal-notes redux) data for casual readers of pop sci. That would cost their time (or some overworked PhD student's) and project money, the bad news is no one is willing to do that nor paying for it. It's not that there's some kind of conspiracy, it's that people are actually busy working.
> What is unreasonable, very unreasonable, self-entitled in my opinion, is expecting that experimental physicists provide some kind of repository
> It's not that there's some kind of conspiracy
You seem to be arguing with someone else
> I don't usually comment on HN about Physics because... well, never mind, it really was a bad idea this time.
If you are knowledgeable on the subject I would encourage you to comment, but keep the comment on the topic being discussed
If by seeing "how well different theoretical models express experimental data" you're planning to apply idk assorted non-linear regression models from equations you're not familiar with to see which one has the minimum chi-square or something like that, well I guess that's what hobbies are for. Differences tend to appear at the limiting cases, there you need more Physics than Levenberg–Marquardt fun, so it's better to start there.
I have to warn you that your wording matches the usual stuff you get from Physics cranks (the bane of the trade), hence the knee-jerk reaction, sorry about that. I'll try harder next time.
to express concepts like these to anyone interested using real world data to show why these concepts are important
Like why Newtonian physics is insufficient to explain Mercury's orbit
Or how infinitely divisible energy leads to the 'ultraviolet catastrophe'
Or how one can approximate the speed of light just using orbital data of io and earth (romer's initial method)
I can appreciate that my wording may have been ambiguous
Brevity can sometimes be the enemy of clarity but questions can help avoid assumptions
I'm not an Astronomer (nor Astrophysicist, I know about GR coming from a Theoretical Physics bkg), so I suspect you could get more recent data, but a classic reference from the GR book of Weinberg is a paper from G. M. Clemence: http://adsabs.harvard.edu/abs/1947RvMP...19..361C (it can be obtained if you look around, there's a similar free-to-read paper from the same Clemence: https://www.jstor.org/stable/3143142?seq=1#page_scan_tab_con...) that has as reference this: http://adsabs.harvard.edu/full/1943AJ.....50..126C (full text), that quotes the Astronomical Papers of the American Ephemeris, Volume 11 (it says II, but it's actually 11), part I. Google is your friend (they've scanned those!) and you can find the data at https://catalog.hathitrust.org/Record/000068403. This is how a little of preliminary research works, you have to do it yourself all the time... Luckily now you don't have to go hunting for a paper copy without being sure about the contents all the time (although it still happens).
The classical mechanics calculation might be tricky, to say the least, as well.
For the UV catastrophe I've always liked the Jeans cubic cavity and the Gamow observation that opening an oven doesn't kill you. And of course, the fact that integrating Planck's law gets you Stefan-Boltzmann's, very neat result.
I should think about all this a bit more in order to give you better feedback.
There is also the CERN opendata portal but this tends to be more about releasing large datasets which require non trivial efforts to analyse. I thought this would be too difficult to make use of but there was a publication earlier this year using CMS data[3].
[1] https://zenodo.org/ [2] https://hepdata.net/ [3] https://arxiv.org/abs/1704.05066
4: There are too much quantum mechanics experiments. Which one? If the experiment is easy enough most Physicist prefer to measure it themselves and not download a bunch of data that you can't be sure about the details. If it's complex the data usually must be carefully analyzed.
([not a qm experiment] IIRC in the last LIGO experiment the noise was much higher than the signal, perhaps 100x, the nice chirp that most article show has a lot of preprocessing.)
2: In the first result of https://www.google.com/search?q=black+body+radiation+experim... I get https://www.phys.ksu.edu/personal/rprice/BB.pdf Is that enough? Be careful because it is not a canonical source, it's not a peer review article, the author describe it as:
> Other Projects and Papers:
> Although not the groundbreaking by any means, the following are some papers I’ve had to write for various classes during my undergraduate career at the University of Arizona Physics Department. Perhaps to someone they may provide some value or reference:
I think it's a standard experiment in 2nd or 3rd year of Physics, so there must be plenty of tables flying around. I measure something like that once, with a tungsten incandescent lamp. (IIRC tungsten is not black enough, you have only 50% of the expected light at one end of the visible spectrum and 60% at the other end, or something similar, also the glass and lens absorb part of the light and it's difficult to get the data about them, so ... there are a lot of details that you must check before using the data.)
In Chemistry they use more tables, you can buy books with tables and tables of experimental data, but it's more difficult to have a clean theory to compare with them.
If you are an expert they probably know of you already and would be happy to collaborate on whatever further research is done using their acquired data. (This happens between experimentalists and theorists all the time).
Some larger collaborations may provide their raw data broadly. Eg, I believe all Hubble Space Telescope data becomes publicly available (the PI’s get some limited time exclusive use to their run data, so they don’t get scooped, but it’s made public later.). Other setups like CERN and FermiLab may do similarly. In these cases it’s up to you to dig deep into the instrument manuals and do your own calibrations and adjustments.
Regarding matching experiment to theory, that’s basically done by experimental research groups directly, in their own publications, probably widely available in the Arxiv.
I jest, but honestly I am confused abit by your flippant response
Is my request that controversial? The speed of light has been studied for hundreds of years.. asking to see even just romer's data should hardly be an affront on the time of contemporary researchers
Do you think science should be accepted as only solutions without evidence?
I agree, spend your time advancing science but does publishing fall under your description of 'sharing'?
I blame the journal format for the lack of resources I am seeking: it is impractical to publish terabytes of raw data in a journal so why even describe the data beyond your results?
I feel the journals have inadvertently created a system of belief which is antithetical to science
Look at the recent revelations concerning reproducibility
One argument against gatekeeping 'amateurs' is the researchers are busy researching and we require more checks than those researchers have time to do themselves
How would you feel about a closed source project that lacked any documentation and only showed vague benchmarks but promised revolutionary results?
Is it healthy? No. Is it rational given the situation? Sadly, yes.
Don't use someone else's data. That defeats the purpose. But aside from Io and Mercury, you can do a huge amount with a modest amount of equipment at home.
For example, for the blackbody spectrum, you need an empty kiln, a diffraction gradient (for separating wavelengths of light) and a photometer (for measuring the intensity of light). Heat the kiln to a temperature, put the diffraction gradient in front of an opening in it, and then measure the light intensity with the photometer at various angles from the grating to plot out the spectrum at that temperature. Change the temperature and repeat.
The original quantum mechanics work was based on emission lines of atoms. You need a tube with appropriate monatomic gases and a way of exciting it. They sell these for lab classes. Then you put current through the tube, put your diffraction gradient in front of it again, and measure the angle of the distinct lines you see. Those are exactly the data that Heisenberg was trying to explain.
A lot of other quantum mechanical predictions are made via statistical mechanics and describe the thermodynamic properties of material. Now you're back in measuring latent heat, specific heat, expansion coefficients, and all those unsexy things that you can do pretty straightforwardly.
There are lots of ways to measure the speed of light. John Baez describes some at http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLigh....
A lot of the stuff you hear about isn't feasible to reproduce because it's enormous or time consuming or expensive. You're not going to build another LHC (but you could probably build a little cyclotron and measure meson decays). You can certainly learn how to make observations of Mercury and measure its shift of perihelion over the course of the next couple years, but that's pretty low payoff for your time compared to table top experiments.
> Are there resources of others showing from experiment to theory with calculations of real data defending the theory's math
Yes. Experimental physics papers. Theoretical physics gets all the attention, but it's the minority of the actual activity of the field.
1. Head over to physics.stackexchange.com.
2. Sort all answers by votes.
3. Start reading (read the corresponding questions first).
4. Emerge three days later slightly enlighted with a stubble on your face.
5. ???
6. PROFIT!!!