Wikipedia:Reference desk/Archives/Science/2019 March 25

= March 25 =

Pediatric Anesthesia
Would a pre-school child undergoing a diagnostic lumbar puncture (spinal tap) procedure in a NYC hospital during the years 1954-6 typically have been given anesthesia for the procedure? If not, when did anesthesia start being routinely administered to children having such procedures? Did the medical community at that time acknowledge that pre-school children felt pain?```` — Preceding unsigned comment added by 2607:FCC8:9C4B:3500:8548:1AF5:FDDD:D935 (talk) 00:25, 25 March 2019 (UTC)
 * I think that the problem is not whether pre-school children feel pain or not but that any anesthesia has its own risks especially in children. Ruslik_ Zero 09:01, 25 March 2019 (UTC)
 * On the contrary, the existence of pain in babies has been a subject of much debate. As the article details, attitudes have changed a great deal. Based on our article, I think the answer for the OP's question is likely "No", though they have neglected to provide a specific jurisdiction. Matt Deres (talk) 02:10, 26 March 2019 (UTC)
 * Let's clarify that we're talking about local anaesthesia. The decision is whether to give one needle to numb the pain of the second needle, or to use one needle for the procedure on the theory that one can be quick enough to obviate the need for anaesthesia. Pre-verbal kids tend to respond just as poorly to a needle loaded with local anaesthetic as they do to the spinal needle. In general, you'd be using lidocaine, which only went on sale in 1948, so perhaps was not very widespread in use by 1954. It would be interesting to know when lidocaine began being added routinely to lumbar puncture kits. - Nunh-huh 16:08, 27 March 2019 (UTC)

Newby Island
How much garbage in all (by weight) has been dumped in the Newby Island landfill? How much of it is estimated to have completely decomposed? 2601:646:8A00:A0B3:D957:1488:1878:1C03 (talk) 09:02, 25 March 2019 (UTC)


 * Consider using the search engine at the EPA's website. In just a few seconds, I found case studies, permits, site overviews, ... even a full-length book A Case Study of San Jose's Municipal Waste System (1973)...
 * Surely if you spend a little effort searching, you can find the exact data you seek. One item of caution: big, old sites like this have multiple (perhaps dozens or hundreds) of permits, so the records might be scattered across dozens of listings spanning decades.  It may be a full-fledged archive research effort to distill all the history into one summary number.
 * Nimur (talk) 13:44, 25 March 2019 (UTC)

Why will the largest optical telescope stay 10 meters for over 3 decades then jump to 39?
In fact two 30-39m scopes and a 24.5m will open in 2024-27. Sagittarian Milky Way (talk) 14:19, 25 March 2019 (UTC)
 * Because no body built them yet? -- Jayron 32 14:20, 25 March 2019 (UTC)
 * To put it simply: it took a long time to find somebody to pay for a new telescope; and even after that, the cost is only one of many difficult obstacles that had to be resolved. You can read the long and storied saga of Thirty Meter Telescope in our article.  These are expensive and unique instruments, and their technical parameters (including primary aperture) have to be very strongly justified.
 * Why build a 12-meter telescope if we already have a 10-meter telescope?
 * What do we plan to see with 30 meter apertures that we could not see with 10- or 20- meter apertures?
 * Will a very large ground-based telescope see better or worse than a smaller-sized orbital telescope?
 * Why should we use visible-spectrum light to study deep space in this century?
 * ...These are the kinds of difficult scientific questions that actually have pretty good answers. You can download the TMT Press Kit, containing FAQs and response summaries, plus cool photos.
 * Nimur (talk) 15:55, 25 March 2019 (UTC)


 * One problem is that a single large lens or mirror will tend to deform under it's own weight to a significant degree, meaning it's optics would change whenever it is moved into a different position (see Hubble_Space_Telescope for an account of how a tiny deformation can cause image distortion). The new solution is to be "...segmented and consist of 492 smaller (1.4 m), individual hexagonal mirrors".  Of course, all those mirrors will require electromechanical controls to adjust them, and presumable an AI program to figure out how to constantly re-aim each individual segment to optimize the image.  These are not trivial advances. SinisterLefty (talk) 18:30, 25 March 2019 (UTC)


 * Keck I has 36 mirrors. Though maybe 9-15 times the area is more than proportionally more difficult, with 14-22 times the mirrors needing to be controlled 3-4 times more accurately and more than 3-4 cubed the materials being suggested by the square-cube law. Sagittarian Milky Way (talk) 20:39, 25 March 2019 (UTC)


 * I can think of several possible systems for adjusting the mirrors:


 * Set each mirror to a precise position based on detailed calcs and devices which measure the current position within nanometers. Don't use any visual feedback.  These adjustments could be made during the day, perhaps with minor fixes needed to counter temperature changes at night.


 * Use visual feedback, say by aiming at a known target far enough away to qualify as an "infinite" focal point, and adjust each mirror until the image is closest to the target. This method could be complicated if adjusting one mirror means the other mirrors then need to be adjusted to match, requiring many iterations to perfect the image.  Perhaps a target like a crater on the Moon might work, but the Moon is of course only visible part of the night, and presumably these adjustments couldn't be made during the day, even if the Moon was visible.  And aiming the telescope at a new target may require more fine-tuning of the individual mirrors.


 * Same as above, but use the actual target for the night to calibrate the mirrors. Here the problem would be the lack of a reference describing what the image should look like.  Some images, for example, may actually be blurry, due to a gravitational lens that isn't focused right on Earth, clouds of gas between us and the target, etc., and trying to make those images appear sharp could yield interesting results.


 * A combo of the 3 methods might actually be used, in the order above, to increase the image precision at each step. Dynamic changes in the atmosphere during the calibration would also make the focusing problem more complex.  Adaptive optics may be of interest here. SinisterLefty (talk) 23:05, 25 March 2019 (UTC)


 * They make an artificial star with a sodium laser maybe something else for infrared and tell the software to keep that laser dot sharp. There's a low density layer of sodium atoms or ions in the mesosphere from lucky sea salt molecules that got high enough to be split by UV. Sagittarian Milky Way (talk) 01:43, 26 March 2019 (UTC)


 * Hubble is near 30 years old and has a 2.4-meter (7.9 ft) mirror. The James Webb Space Telescope has one of 6.5-meter (21 ft).


 * Its "only" for infrared tho but that offers to actually find allot more. Forget earth based telescopes. Pray for JWST. --Kharon (talk) 23:25, 25 March 2019 (UTC)
 * If it ever happens it'll be one of the most useful scopes ever. Don't forget diffraction-limited sharpness per meter is better at smaller wavelength though. Sagittarian Milky Way (talk) 02:17, 26 March 2019 (UTC)
 * Infrared is nice if you want to study Kuiper belt objects, clouds of dust or high-redshift galaxies, but there's a lot of interesting stuff to see in visible and near-ultraviolet too. The main advantage of large telescopes is that you need a shorter integration time to gather sufficient light. If you're observing rather static dust clouds, that's nice as you can observe more of them in your allotted observing time (but it would have been easier to get four times the observing time on a telescope half the size). If you're observing binary white dwarfs it's a different matter. To see anything interesting, the integration time must be only a small fraction of the time scale on which their spectral features change, which is the timescale of their orbital period. And of course, these are blue. Short integration times are most important when observing fast phenomena, which tend to be most visible in short wavelengths.
 * The diffraction limit of a larger telescope could be interesting, but in contrast to radio telescopes, big optical telescopes are usually limited by seeing. Adaptive optics help, but are never perfect. PiusImpavidus (talk) 16:28, 26 March 2019 (UTC)


 * Using a mirror that can be adjusted to compensate for deformation under its own weight is called active optics. We've got an article on that. PiusImpavidus (talk) 16:28, 26 March 2019 (UTC)


 * Another method that might be considered is to use many smaller telescopes, digitally capture each photon, then combine them into an image with the combined light gathering power of all of them. This could have many advantages, such as being more fault tolerant (say by dropping images where clouds passed over), less expensive, averaging out atmospheric conditions if the telescopes are widely spaced, etc. Even amateur astronomers could contribute. SinisterLefty (talk) 00:01, 26 March 2019 (UTC)
 * What you're re-inventing is called Astronomical optical interferometry. {The poster formerly known as 87.81.230.195} 90.200.138.194 (talk) 00:42, 26 March 2019 (UTC)
 * Which is much easier in radio waves, they can see astounding detail with a virtual radio dish the size of the Earth. If tech ever advanced enough to do this with infrared and light in space the resolution would be stupifying. Sagittarian Milky Way (talk) 02:02, 26 March 2019 (UTC)
 * In radio and submillimetre this interferometry with separate detectors is done, but it's important that you collect the light as an electromagnetic wave, not as photons (obviously, the light is both at the same time). If you collect the light as a bunch of separate photons, losing the phase information, you can no longer combine them to do interferometry. You can still stack them though, and that's often done, in particular by amateur astronomers, to get useful results from relatively cheap equipment and poor sites. PiusImpavidus (talk) 16:28, 26 March 2019 (UTC)


 * Yes, the "stacking" method is what I was talking about, since that method doesn't require precise measurement of the distances of each telescope from the others. Thus you could combine info from thousands of telescopes all over the world. SinisterLefty (talk) 10:08, 27 March 2019 (UTC)
 * Ha! That sounds surprisingly similar to a NASA research proposal I once ...um, read.  If only I could find some way to distribute and control a billion network-connected cameras to a billion different locations around this planet, ...
 * Competitive, creative computational astronomers: the applications are open for 2019... "How might we use data fusion and emerging super-resolution techniques...?"
 * Nimur (talk) 16:35, 29 March 2019 (UTC)
 * Because it didn't jump top 100 meters. Count Iblis (talk) 01:27, 27 March 2019 (UTC)