Talk:List of unsolved problems in physics

Indirect Detection of Gravitational Waves

I have deleted the entry claiming that gravitational waves have been directly detected for the first time, as this is untrue. BICEP2 did not directly detect gravitational waves; it measured their influence on CMB polarization. The only prospect of a direct detection of gravitational waves is through interferometric methods, e.g. LIGO. Journalists this week are really skewering the science, but The Guardian gets it more right than "I Fucking Love Science", which is what was referenced for that claim. See: http://www.theguardian.com/science/2014/mar/23/primordial-gravitational-waves-tantalising-cosmic-birth-big-bang— Preceding unsigned comment added by 2607:f470:24:2:cc05:415f:b4d7:8728 (talk) 03:33, 23 March 2014

Calculating Band-gaps

The reasoning behind accurate calculations of band-gaps and problems associated with this are not necessarily unknown and vary widely from system to system. To pose such a general question is ridiculous and exaggerated. Reasons for inaccuracies between theory and experiment can be multitudinous in scope and include such things as: stronger than anticipated coupling between layers, inconsistencies in lattice constants, low number of k-points in the calculations, possible doping in the experimental material, inconsistent assumptions as compared to the real system and really the list goes on and ultimately depends on the material you're working with. If the question is directed at a specific material and with good reasoning, it'd be much more appropriate. Otherwise, there are many materials where bandgaps can be reasonably calculated and compared with experiment.

Some of These Might Not be Updated

I don't know about all the areas in this article, but at least for fluid mechanics, upstream contamination can be explained by the decreased surface tension of contaminated fluids, which allows the contaminant to flow upwards toward the container with stronger surface tension. Nknka (talk) 14:09, 6 March 2024 (UTC)

Thanks for the feedback. As the upstream contamination article does not say anything about the open problem and this item in the list has no reference, I took the liberty of removing it from the list.--ReyHahn (talk) 14:24, 6 March 2024 (UTC)

Are voids in space empty or consist of transparent matter?

Does this question from the astronomy section make sense? From

• N. D. Padilla, L. Ceccarelli, D. G. Lambas, Spatial and dynamical properties of voids in a Λ cold dark matter universe, Monthly Notices of the Royal Astronomical Society, Volume 363, Issue 3, November 2005, Pages 977–990, https://doi.org/10.1111/j.1365-2966.2005.09500.x

we read:

• Voids can be thought of as large volumes with very low galaxy density surrounded by the walls and filaments of the cosmic web.

The large-scale structure issue related to voids is the nature of gravitational dynamics. The issue is not "empty" vs "transparent" as far as I can tell. Johnjbarton (talk) 21:46, 10 June 2024 (UTC)

The question had 4 refs, none were reviews or even had significant citations. They did not support the question in any case. I delete the question. Gravitational instability studies of dark matter initialized with primordial density fluctuations seems to be the unchallenged model for large scale structure, so as long as the ingredients don't get upended the big picture problem does not seem to be "unsolved". Johnjbarton (talk) 18:32, 11 June 2024 (UTC)

No, it doesn't make sense, deleting it was correct. Voids really are significant underdensities: we can tell that from their effect on the CMB or galaxy lensing. - Parejkoj (talk) 19:02, 11 June 2024 (UTC)

Fluid dynamics

The second question of granular convection in not "unsolved". The simple reason is that bigger objects simply "bubble up" because smaller objects creep underneath them, that is, bigger object have a smaller density. 95.250.132.37 (talk) 18:02, 17 August 2024 (UTC)

Now all we need a reliable source. Johnjbarton (talk) 18:53, 17 August 2024 (UTC)

Is this ok? Or are you implying that no one has made this simple connection !? 95.250.132.37 (talk) 08:01, 18 August 2024 (UTC)

I'm saying that you are making a claim without a reliable source so no one can take any action. Johnjbarton (talk) 15:29, 18 August 2024 (UTC)

Do you have a source for it being an unsolved problem?

My "claim" is that it is the same as for hot air going up (and cold air going down) and everything else in the same "situation".

Buoyancy is based, in a sense, on a "static" principle, but since time is a thing, and it is unavoidable, that principle is based on a more general dynamic situation.

If you still think that a granular material, when subjected to shaking or vibration, is different from a fluid, then, since I am unfortunately not involved in the scientific environment, if, intead ,you are, please ask someone to "fill the gap" for me, so that there can be the source for you to cite, thanks. 95.250.132.37 (talk) 17:34, 18 August 2024 (UTC)

I added a ref to a 2006 review. Johnjbarton (talk) 17:49, 18 August 2024 (UTC)

That review talks (partially) about the 1st question, nothing about the 2nd question. But, if you have "access" to someone in the field, my invitation to "fill the gap" is still valid. 95.250.132.37 (talk) 15:25, 23 August 2024 (UTC)

The article for Upstream contamination indicates that new research from 2024 has shown this phenomenon is not entirely explained by the previous research. The citation is pre-print research and may not be high quality (I don't have enough expertise to know), but is it sufficient to include here? I recall it previously being present on this page. Nftrot (talk) 15:25, 30 November 2024 (UTC)

In my opinion the article Upstream contamination should be merged in to fluid dynamics because on its own it is not notable. The article is based on an unpublished thesis and one reviewed paper with very few citations. It's a quirky story so the pop-sci magazines wrote it up, but they write up a lot of stuff.

The unsolved problem here is independent verification and interest by scientists in the field. Johnjbarton (talk) 15:56, 30 November 2024 (UTC)

Indeed, I originally found out about the phenomenon through this page. I have very little knowledge in this field and accept that it may be of too little interest among experts to be considered an "unsolved problem". An argument could be made for it being notable due the high degree of novelty as a "real-world" example of a phenomenon with no confident explanation, but some point someone must have thought it insufficiently notable for this page. The last time I saw it here was several years ago, so I'll try to find it in the edit history. Nftrot (talk) 17:03, 30 November 2024 (UTC)

Problems solved in the past 30 years

List of unsolved problems in mathematics has an analogous section, but with a specific starting year (1995). This was chosen over a relative starting date (as per Talk:List of unsolved problems in mathematics#Change in section title) because of WP:NUMBERS#Statements likely to become outdated. Should a fixed starting year also be used here? GalacticShoe (talk) 02:40, 29 August 2024 (UTC)

Sure, but honestly most of that content needs to be verified and much deleted. Specifically every item on the list needs a secondary review reference verifying 1) it was an unsolved problem and 2) it was solved. That's a high bar.

This entire "unsolved problem" concept is not how physics works. Very rarely is physics a "problem" with a "solution" and it usually takes decades to realize that breakthroughs have really occurred. Johnjbarton (talk) 04:26, 29 August 2024 (UTC)

I went ahead and set 1990s as the cutoff. It is better to have a date, if not it means we need to update it every year or so. I also agree that it should be verified, it used to be a much shorter list.--ReyHahn (talk) 17:07, 5 September 2024 (UTC)