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June 9

Determine a fluorescent lamp fixture's voltage requirement

I have a 6 W UV-C tube with a fluorescent lamp fixture. The seller says it's for 110 V. However, it failed to turn on after proper installation. The seller returned money to me and let me keep it. I now have a 220 V transformer. How do I know if it's safe to test if the fixture was actually a 220 V one? -- Toytoy (talk) 15:06, 9 June 2022 (UTC)[reply]

According to customer service at Amerlux, a light manufacturer, the ballast is voltage rated, not the fluorescent tube. She also noted that a UVC tube is ultraviolet only. It will not fluoresce, so it will not produce visible light. I assume that you know that and you were trying to use it for a different purpose than lighting a room. 97.82.165.112 (talk) 18:17, 9 June 2022 (UTC)[reply]

A fluorescent UVC lamp will give off some visible light, as the spectrum of the glowing gas is quite complicated. PS do not let UVC irradiate you for long as it will cause sunburns even on the eye. You can also smell the ozone produced. Graeme Bartlett (talk) 01:13, 10 June 2022 (UTC)[reply]

History and Future of the Sunda trench between the Australian Plate and the Sunda Plate?

I'm trying to get a feeling for what the portion of the planet north of the currently extant Australian plate looked like while Australia was farther south. Is there any way to know whether there were more islands (to the size of Papau New Guinea?) that were subducted into the Sunda Trench or not? Also as the Australian plate moves north, is there any way to know whether Australia would subduct into the Sunda trench presumably raising the Java, Borneo, etc (and as such perhaps causing some of the islands to join) or whether you'd end up with the Australia plate staying on the surface and causing a massive crunch.Naraht (talk) 15:10, 9 June 2022 (UTC)[reply]

Continents and islands never subduct. They just collide with each other. So, Australia will collide with islands lying between it and the Asia and then with Asia itself. This collision will raise a new great mountain belt. As to the past, some island have been probably accumulating at the North margin of the Australia as it moved North. I also should note that New Guinea is a part of the Australian continent, not a true island. Ruslik_Zero 21:02, 9 June 2022 (UTC)[reply]

Only limited amounts of continental material are ever subducted due to their relative buoyancy, a result of their much lower density than oceanic crust. The northern part of the Australian continent has been colliding with the Pacific Plate since the Late Cretaceous. This has led to the progressive accretion of several terranes representing island arcs and microcontinents. This paper looks at that history and where these bits and pieces have ended up in terms of the present geology of New Guinea. Mikenorton (talk) 22:32, 9 June 2022 (UTC)[reply]

Further west, in the Timor area, the oceanic crust that used to lie north of the Australian continent has now been completely consumed by subduction along the Sunda Trench system and there is ongoing collision, involving some subduction of the Australian continental margin, according to this study on that region. The collision caused by the continental margin entering the Sunda Trench is diachronous, propagating steadily westward with time. Mikenorton (talk) 22:51, 9 June 2022 (UTC)[reply]

From studying the papers, it feels like the Australian Plate is undergoing two *different* type of collisions. On the east side of the northern edge, New Guinea has crunched into quite a bit of land on its way north but at this point, only New Britain and New Ireland are going to be crunched in the near term. After that, it will simply continue north, however, that depends on whether the Philippines are moving east fast enough to get in the way or not.

OTOH, in the west, the Australian Plate will continue to subduct but this is causing the Sunda plate to rotate counter clockwise slightly, but the continent itself is heading just enough east of directly north that it won't necessarily crunch the islands farther west in on the Sunda Trench.

Feels like any the Techtonics of the Sunda plate and the Philippines are more complicated than anywhere else on the Planet.Naraht (talk) 15:11, 10 June 2022 (UTC)[reply]

I think that's a fair description. The long term effect of the collision with the Sunda Plate and all those other minor plates to the east is hard to predict. Mikenorton (talk) 19:36, 10 June 2022 (UTC)[reply]

Big Ear's design and Wow signal

Per Wow! signal, prior to detecting it, the Big Ear was assigned to the scientific search for extraterrestrial intelligence (SETI). Then, per article, due to Big Ear's design it couldn't fully pinpoint the signal's place of origin. So why was Big Ear assigned to SETI if it lacked the basic ability to determine signal's right ascension (which looks essential in such activity)? Poor decision? Thanks. 212.180.235.46 (talk) 16:54, 9 June 2022 (UTC)[reply]

Every position measurement has some measurement uncertainty (see the quoted errors on the right ascension and declination values in the article). "Normally" there would be a single contiguous error ellipse centred on one point, and one would look for an optical counterpart within that ellipse. Here, the uncertainty is spread over two non-contiguous ellipses – that might look weird at first glance, but it's just an extension (induced by the design of the telescope) of the ordinary measurement uncertainty. Not a big deal, really. --Wrongfilter (talk) 17:34, 9 June 2022 (UTC)[reply]

You can find some details here: [1]. The telescope had two feed horns that looked in slightly different directions. The signal processing equipment was capable of distinguishing a signal in one horn from a signal in the other. The problem is that the program that made a record of the data simply didn't include this information. That's something you'd obviously want to have, and it was added in a later version of the software. This does seem to be a poor decision, and the report's author agrees: it is listed among the "especially important changes done later that should have been done earlier". But it's not a limitation of the Big Ear, it's just an oversight in the data recording software that could have been (and should have been, and later was) easily remedied. --Amble (talk) 18:46, 9 June 2022 (UTC)[reply]

Let me try an clarify my previous answer a bit more, in light of Amble's excellent findings. Obviously, noone would buy a bathroom scale that tells you "you weigh 75kg or 90kg". The difference is that, even with the measures mentioned by Amble, which could have identified the horn that detected the signal, we still wouldn't know where the signal came from. A paper referenced in the article (Caballero 2022) lists 38 stars in the positive horn and 28 stars in the negative horn (already reduced to G-type and early-to-mid K-type stars). So, identifying the horn reduces the uncertainty and the number of stars to investigate by a factor of two, which is great but does not fully solve the problem. --Wrongfilter (talk) 20:55, 9 June 2022 (UTC)[reply]

You can understand why this extra record wasn't usually necessary by thinking about what happens when the telescope would scan across a normal radio source. One horn crosses the position of the source and sees the signal, then the other horn. The radio sources are in discrete locations on the sky and sparse enough to avoid "confusion", so you see two bumps, one after the other, and it's completely obvious which bump came from which horn. The Wow! signal only has one bump. You can look at the right distance before and after it, and where you'd expect to see another bump, there's no signal. Either the first horn saw it, and it turned off before the second horn got there, or else the first horn saw nothing, and it turned on before the second horn got there. So the record for this signal had an ambiguity that wasn't present in the record for normal radio sources on the sky. --Amble (talk) 21:22, 9 June 2022 (UTC)[reply]