Talk:List of unsolved problems in physics

 Unsolved problems in : Note: Use the unsolved tag:  , where "F" is any field in the sciences: and "X" is a concise "explanation" with or without links. The appropriate category tag will automatically be added.''

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.

Hubble tension
Currently there are several types of measurements of the Hubble constant, which seem incompatible with each other, given the experimental errors. The situation is described in Hubble tension, it seems that this is an unsolved problem that could be added to the astronomy section. --Davius (talk) 20:26, 18 November 2023 (UTC)


 * It is in the "Cosmology and general relativity" section. StarryGrandma (talk) 05:11, 19 November 2023 (UTC)

Quantum gravity: Problem of time.
The statement says 'background parameter', which is actually untrue. Everything happens due to a consistent use of cause and effect over time. Take any influence, set Δt to zero, and any influence becomes zero. Also, cause and effect can not exist at the same time, which is when Δt = 0. Any state can be only singular at any given time. Since no more than a single state can exist during any given time, without time, any influence or force can't have any effect, and thus a local big bang can not have occured that created all 3 of time, space and filler. Time needs to exist for any state change, so that must have existed before the big bang. But also space, since a point can't contain volume, and so if all energy that exists in the univere today would be from a point, this would lead to an energy density equation looking like E/v in 4D => E/0^4 => E x ∞^4. If that were true the amount of energy released would be enough to fill any part of space with an infinite amount of energy. The big bang was not a singular event, but happens 'locally' in each segment of space and has a volume to start out with. This then makes then energy density equation into E/v in 4D => E/f, where f is a finite greater than zero => E x f^4. This yields a finite ampount of energy, and a finite amount of energy density, which satisfies the current observation. So, first time, then space, then filler, in that order, but t is always present for any influence greater than zero. — Preceding unsigned comment added by 62.238.45.149 (talk) 11:40, 24 November 2023 (UTC)

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 we read: 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)
 * 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
 * Voids can be thought of as large volumes with very low galaxy density surrounded by the walls and filaments of the cosmic web.


 * 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)