Wikipedia:Reference desk/Archives/Science/2023 November 19

= November 19 =

[Geology] Are there any lava flows on the surface of a true desert?
There are volcanic mountains in deserts, but their lava leaves these volcanoes from high above the Earth's surface, far from the sandy surfaces of deserts, and never reaches the desert surface. Are there any deserts on Earth which have volcanic fissures at ground level, where effusive eruptions are constant or frequent? If yes, please link to any photos or videos showing this. 180.129.39.136 (talk) 11:39, 19 November 2023 (UTC)


 * Does Erta Ale count? It's constantly created new "ground levels", of course -- the lava has to go somewhere. --jpgordon&#x1d122;&#x1d106;&#x1D110;&#x1d107; 19:01, 19 November 2023 (UTC)
 * Yes, that's almost the feature I'm looking for. Are there any videos of fissure vents (if any) in the nearby surrounding desert?
 * Unfortunately, after reading the Tourism [] section of the article, I realise that it's very dangerous to get good footage of the volcano and its surrounding area. 180.129.39.136 (talk) 02:35, 20 November 2023 (UTC)


 * The first sentence of the article Desert you link above begins "A desert is a barren area of landscape where little precipitation occurs . . ." Sand is not an essential component; further down in the lede we have: "Other deserts are flat, stony plains where all the fine material has been blown away and the surface consists of a mosaic of smooth stones, often forming desert pavements . . ."
 * Most of Antarctica qualifies as a desert because very little precipitation falls; the snow and ice there, accumulated very gradually, just never melts, and the snow gets blown about by winds but is not new snowfall. {The poster formerly known as 87.81.230.195} 51.241.161.192 (talk) 20:40, 19 November 2023 (UTC)
 * Yeah, but the OP made it pretty clear that sandy deserts were being referred to. --jpgordon&#x1d122;&#x1d106;&#x1D110;&#x1d107; 23:15, 19 November 2023 (UTC)
 * If, at some place, effusive eruptions from volcanic fissures at ground level are constant or frequent, it will soon cease to be a sandy desert (assuming it was one to start with). --Lambiam 09:39, 20 November 2023 (UTC)
 * You can see the result of some fissure eruptions in the desert about 80 km east of Damascus, Syria: rows of craters with some surrounding lava fields. There are also lava flows in a 250 km radius area around Medina, Saudi Arabia, clearly visible in satellite images. Some of them reach sandy areas.
 * If there's a thick layer of loose material on top of the bedrock, I somehow doubt you'll get clear fissure eruptions. The molten rock may be inserted underneath the sand. PiusImpavidus (talk) 10:39, 20 November 2023 (UTC)
 * I think the Medina satellite images are a very good example of what I would have liked to see when the lava flows were still active, captured on video. 180.129.39.136 (talk) 10:28, 21 November 2023 (UTC)

invisibility shields
hello i would like to ask how invisibility shields can generate wormholes. thanks very much.

Timetravel11 (talk) 12:43, 19 November 2023 (UTC)


 * What makes you think they can? AndyTheGrump (talk) 12:49, 19 November 2023 (UTC)
 * by searching for metamaterials and invisibility cloaks wormholes i was able to find papers on the subject. thanks a lot. Timetravel11 (talk) 12:54, 19 November 2023 (UTC)
 * Not an actual wormhole as such - a way to conduct a magnetic field from one place to another without it causing a magnetic field outside. This sort of thing can be used to measure the Aharonov–Bohm effect which is yet another of the really strange effects one gets in quantum mechanics. So one can actually detect the magnetic field - just one needs to go all the way round to do it! NadVolum (talk) 16:32, 19 November 2023 (UTC)

With the cloaking device active, light is 'deflected' around the object to make it appear as if it did not exist, rendering it invisible.

See Wormhole: "Wormholes, a common element in science fiction, are consistent with the general theory of relativity, but whether wormholes actually exist remains to be seen." Schwarzschild wormholes, also known as Einstein–Rosen bridges, can be modeled as vacuum solutions to the Einstein field equations.

Cloaking devices were introduced in the 1966 Star Trek episode "Balance of Terror in the hands of the Romulan species and Invisibility cloaks work well within the Fictional universe of Harry Potter. Wikipedia WP:RS rules restrict us Muggles to sceptical viewing of video titles such as "Invisibility Cloak Findings at Duke University" where the touted "invisibility cloak" is no more than a resonant microwave structure that makes minimal disturbance of a simulated electromagnetic field of one particular frequency. Math professor Gunther Uhlmann in "Electromagnetic wormholes explained" admits that "a prototype does not yet exist" and that obtaining a material with a negative index of refraction that does not exist in nature would be needed. Philvoids (talk) 17:13, 19 November 2023 (UTC)


 * Note that while the cloaking device as a science fiction element may have started with Star Trek, invisibility in fiction and the cloak of invisibility has a long history as a supernatural or magical concept. Nil Einne (talk) 10:05, 20 November 2023 (UTC)
 * There are many examples of "invisibility cloaks" that are essentially a television strapped to your chest and a camera strapped to your back. If aligned just right, the television shows what is behind you, so you are invisible. It makes for good clickbait along with a photo of some guy in a weird hoodie that hides all the wiring. 12.116.29.106 (talk) 13:22, 21 November 2023 (UTC)

Cause of the rain that caused the 1315 western european Great Famine
What caused the extreme rainfall? The descriptions in that article sound a lot like a volcanic event and the list of volcanic eruptions in Iceland mentions Katla in 1311? Has anyone investigated this connection? — Preceding unsigned comment added by 78.1.161.168 (talk) 22:29, 19 November 2023 (UTC)
 * Article: Great Famine of 1315–1317. Philvoids (talk) 00:32, 20 November 2023 (UTC)
 * The article says The Great Famine may have been precipitated by a volcanic event, but the reference for that statement refers to "huge volcanic eruptions in Indonesia", not Iceland. CodeTalker (talk) 00:59, 20 November 2023 (UTC)
 * Thanks, too bad that it looks like third hand information. Indonesia was my first thought and I checked Wikipedia's list of eruptions of the Holocene, but the last candidate was from 1257 and the next one mentioned in Indonesia was much later. Which one are we missing 78.1.161.168 (talk) 01:37, 20 November 2023 (UTC)
 * The article Little Ice Age suggests that it, though usually considered to have started in the 16th century (perhaps because of a paucity of earlier data), may actually have begun around 1300. Its section Possible causes mentions seven possible causes (which may all have contributed), including initial cooling caused by four volcanic eruptions in Indonesia starting with the one in 1257 "followed by three smaller eruptions in 1268, 1275, and 1284, [which] did not allow the climate to recover." See also Little Ice Age volcanism. {The poster formerly known as 87.81.230.195} 51.241.161.192 (talk) 05:11, 20 November 2023 (UTC)


 * This article by Professor Brian M. Fagan, Frozen: Britain's Little Ice Age, says that the 1257 eruption of Mount Samalas was one of three possible causes of the 1315 famine, the other two are "a prevalent high over the Azores and a low over Iceland", and "a dramatic reduction in sunspot activity... However, the very latest research suggests that variations in solar activity play only a small role in the Earth’s climate". Alansplodge (talk) 19:03, 20 November 2023 (UTC)
 * I read Brian Fagan's book about the Little Ice Age a while ago, but it's over 20 years old, I was hoping climatology filled in the gaps in the meanwhile. The series of eruptions 30-60 years ago doesn't look realistic to me. The ash clouds wouldn't be floating around that long. The event sounds a lot more like 1816 famine that as caused by a 1815 eruption of Mt Tambora. This ash cloud also affected northwest Europe and left the rest of the continent alone. As for Azores high and Iceland low, they're well known meteorological patterns that still happen today, why were they so strong in those several years? Has there been any recent scientific work on this? If some volcano blew up in Iceland or Indonesia or the Andes in 1313/14 that would be an easy explanation, but no mention of this on the internet... 78.1.74.220 (talk) 21:02, 21 November 2023 (UTC)
 * You seem to be looking for a simple one-factor, fairly immediate cause in a hugely complex and semi-chaotic large-scale system (planetary weather/climate) which we are only beginning to grasp, in which everything (may) affect everything else in ways we struggle to comprehend or even conceive of, and which can involve rebalances that can take decades-to-centuries to play out. Good luck with that. {The poster formerly known as 87.81.230.195} 51.241.161.192 (talk) 01:40, 22 November 2023 (UTC)
 * It is obviously an outlier event in the last 1,000 years in that part of Europe. The other Great Famine with a Wikipedia article (Great Famine of 1695–1697 or Seven ill years) was preceded by volcanic eruptions in the immediately preceding years, same as the Tambora famine (which lasted 2-3 years too). Obviously we know a lot more about ENSO/NAO/etc than 20 years ago and even long-term natural climate change is a major topic lately. I'd be surprised if no one has researched this since 2000. 78.1.74.220 (talk) 02:26, 22 November 2023 (UTC)