Subject: Can someone please explain?
Posted by: Mixamatosis
Date: Jan 21 17
I've read that it's dangerous to mix ammonia and bleach. Variously I've read that it can produce deadly cyanide gas, chlorine gas (which is said to be bad for you) and even explosions.
However swimming pools are kept fit for use with chlorine, and our urine contains ammonia but then we may clean toilets with bleach. Also many cleaning products contain either ammonia or bleach and it would be easy to use them unthinkingly in combination.
How is it that people aren't generally harmed by these dangers when swimming in swimming pools or doing daily cleaning, or are we being harmed at low level and is the harm cumulative?
Posted by: Mixamatosis
Date: Jan 21 17
I've read that it's dangerous to mix ammonia and bleach. Variously I've read that it can produce deadly cyanide gas, chlorine gas (which is said to be bad for you) and even explosions.
However swimming pools are kept fit for use with chlorine, and our urine contains ammonia but then we may clean toilets with bleach. Also many cleaning products contain either ammonia or bleach and it would be easy to use them unthinkingly in combination.
How is it that people aren't generally harmed by these dangers when swimming in swimming pools or doing daily cleaning, or are we being harmed at low level and is the harm cumulative?
526 replies. On page 22 of 27 pages. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
brm50diboll 
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Spanish does not seem that it would be that difficult to learn from reading it, but understanding speech is a different matter. We have large numbers of Hispanics in Texas (most of whom are American citizens) who preferentially speak Spanish. We also have a number of Spanish language TV stations and networks. I realize that Mexican Spanish (colloquially referred to as TexMex in Texas) is different from Castilian Spanish, but native Spanish speakers here speak at a rate much faster than English speakers do. I can't keep up with the speed of their speech. Reading Spanish is one thing, understanding spoken Spanish is a different thing. I am well past the age of optimal language acquisition, so I don't really plan to pursue languages anymore. Reply #421. Apr 19 19, 3:53 PM |
Mixamatosis
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And then there's learning a language only to find real speakers use slang a lot.... Reply #422. Apr 24 19, 1:41 PM |
havan_ironoak
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brm50diboll said in an earlier post "Mexican Spanish ... is different from Castilian Spanish" That brought back memories! I took Spanish in high school many years ago and our (Italian born) Spanish teacher was a stickler for proper pronunciation and grammar. One of the first students to drop the class was Hispanic because he'd learned so many bad habits growing up that it was tough for him to learn it properly. Oddly though I also recall my teacher relating the story about how Castilian Spanish not being "pure Spanish" either. Seems one of the early Castilian kings had a speech impediment and rather than risk disfavor in the royal court, the nobles all adopted some of his speech habits. e.g. While people speaking "pure" Spanish would pronounce a double "L" as if it were a "Y," the Castillian court adopted their king's soft "j" pronunciation. So while pure Spanish would say that yellow is " ah ma ree o" Castillians would say " ah ma ree jo" Reply #423. Apr 29 19, 7:10 PM |
| Mixamatosis
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Your post reminded me of the difference in Spanish between areas that pronounce c before e or i as s (including parts of Spain and nearly all of Latin America) and areas that pronounce it as th. I had been told that the th sound also came from a King who had a speech impediment and pronounced his s sounds as th so his court adopted his way of speaking. However I also read that this was a myth, and not the origin of the difference. Reply #424. May 01 19, 1:22 AM |
| brm50diboll
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So, returning back to Astronomy, I have pretty much covered stars and our solar system. I suppose I should next examine larger scale celestial structures. Let me begin with star clusters. Star clusters range from a low of ten or so stars to a high of several hundred thousand stars. Smaller than the minimum, and we have multiple star systems. Larger than the maximum, and we have dwarf galaxies. The exact boundaries are not completely fixed and are subject to some debate. For example, the very large globular cluster Omega Centauri is felt by some to be a remnant of a dwarf galaxy that was cannibalized by the Milky Way and stripped of its outer stars. But I digress. Star clusters can be divided into two distinct groups: open clusters and globular clusters. They are quite different from each other, as I will explain. Both are held together by gravity, but open clusters contain fewer stars, are held together more loosely, tend to break up over time, contain younger stars, and are usually found in the plane of the Galaxy itself, whereas globular clusters contain many more stars, are packed together more tightly, hold together for extremely long periods of time, contain older stars (typically around 10 billion years old or so - twice the age of our Sun), and orbit the Milky Way in a globular "halo" oriented at a high angle to the plane of the Milky Way, although these orbits do cross the plane in two places, so rarely a globular cluster may be "passing through" the disk of the Milky Way, where it is vulnerable to having some of its outer stars stripped. Famous examples of these types: For the open clusters, the Pleiades in Taurus, which is only a few million years old and contains several very large blue stars that will have short lives and eventually go supernova. In 50 million years, the Pleiades will be gone: its larger stars dead and its smaller stars stripped away into the general disc of stars in the plane of the Milky Way. Our Sun was likely originally a part of an open cluster formed from a nebula. Its "siblings" were stripped away long ago and are unrecognizable as such now. As for globular clusters, the most famous in Northern skies is probably M13, the Hercules cluster. Which reminds me: I should explain what designations like M13 mean. Maybe next time. Globular clusters can contain hundreds of thousands of old red stars, and are very impressive to look at in a telescope, or even in binoculars. The zodiac sign of Sagittarius contains many globular clusters. Reply #425. May 15 19, 2:01 PM |
| Mixamatosis
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Interesting article on 'The Ultimate Limit of Human Endurance. FYI, comments etc https://www.bbc.co.uk/news/health-48527798 Reply #426. Jun 06 19, 3:36 AM |
| brm50diboll
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Thanks, Mix. Interesting article. Don't think it will stop aging, though. Being in good condition helps people live to a greater percentage of their theoretical maximum life spans, but doesn't really seem to increase that number, which appears to be around 120 years and is controlled by a biological clock, telomeres, and oxidative stress. Studies in mice have shown life span prolongation with severe calorie restriction, which may work by decreasing basal metabolic rate and consequent oxidative stress. Would be difficult to carry out such experiments on humans, but not impossible. Think I'll have a double cheeseburger, though. Reply #427. Jun 06 19, 12:00 PM |
| Mixamatosis
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I certainly wouldn't want to live to be 120 and don't expect to either. Why is it that so many old people can't walk, I wonder? Not being able to walk, or walk steadily, means not enough exercise and a risk of falls, which is always a danger to older folk. Reply #428. Jun 07 19, 2:45 AM |
| brm50diboll
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There are multiple reasons why many (certainly not all) older people have difficulty walking: arthritis, spinal nerve root compression from collapsed vertebrae due to osteoporosis, muscle damage, inner ear balance problems, medications that cause orthostatic hypotension, strokes or ministrokes that affect the cerebellum or pons (which are important for balance), Parkinson's disease, and many others. Fixing problems works best when the problem is relatively acute (fresh). The more chronic and long-lasting a problem is, the less likely it will respond well to treatment. If someone has already had several back surgeries, for example, it is unlikely another one will fix their difficulty walking from severe osteoarthritis of the lumbosacral spine, for example. Reply #429. Jun 07 19, 11:03 AM |
| Mixamatosis
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Oh dear, all this to 'look forward' to. Reply #430. Jun 09 19, 1:54 AM |
| brm50diboll
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OK. I had mentioned that I needed to explain what M designations meant, such as M13, the Hercules globular cluster. M stands for Messier; specifically, Charles Messier, an 18th century French astronomer who catalogued "Deep Sky Objects". Like many discoveries, Messier's were accidental but wouldn't have been possible without his keen attention to detail. Messier actually had no idea what most of the objects that ended up in his catalog really were. He started out as a comet hunter. Comets appear fuzzy when viewed through a telescope, but they move from place to place in the sky at a fairly quick pace when they are first discovered in a telescope before (or even if) they become visible to the naked eye. But faraway comets are dim, fuzzy objects, and it turns out that most dim, fuzzy objects in the sky are *not* comets. The difference is that these other objects stay in the same place night after night while comets move. In order to aid himself and other astronomers who were searching for comets, Messier decided to make a list of prominent objects that had been mistaken for comets: dim, fuzzy objects that *didn't* move. He listed the exact position (right ascension and declination, which I discussed in this thread a long, long time ago) of these objects, so that if any astronomer saw a dim, fuzzy objects in those places, they would immediately know that night that the object was *not* a comet and not waste any further time on it. But Messier didn't really know what most of these things were, just that they *weren't* comets. Many of these objects got called "nebulae", but, by our modern understanding of the term, many of them weren't true nebulae as we know those today. The list eventually reached 110, from M1 to M110. Some of the objects on that list are extremely famous today. Here's a few of the all-stars: M1, the Crab Nebula in Taurus, a supernova remnant. The aforementioned M13, the Great Hercules globular cluster. M31, the famous Andromeda Galaxy. M42, the Great Orion Nebula. M44, the Beehive open cluster in Cancer. M45, the famous Pleiades open cluster in Taurus. M57, the Ring Nebula in Lyra. And on, and on. Now, some of these were complete "duds" that weren't worth mentioning at all: binary stars misidentified in telescopes with poor optics. But the vast majority of them eventually were sorted into the following classes: 1) Diffuse nebulae, where stars are born, like M42. 2) Planetary nebulae, a misnomer, as it has nothing to do with planets but looks planet-like. These are dying stars shedding their outer layers with M57 as the prototype. 3) Supernova remnant nebulae, like M1. 4) Open clusters like the Pleiades, M45. 5) Globular clusters like M13, and, finally, 6) Galaxies like M31. Galaxies were the last to be correctly identified, not until well into the 20th century did that happen, after the work of Edwin Hubble. Prior to his work, those Messier objects we now know to be galaxies were thought to be nebulae inside our own Milky Way, which was once thought to be the whole universe. Hubble straightened us out on that one. Reply #431. Jun 16 19, 5:45 PM |
| brm50diboll
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There is a total solar eclipse visible from parts of Chile and Argentina ongoing right now. I am watching the feed of it on YouTube. Reply #432. Jul 02 19, 2:19 PM |
| brm50diboll
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A galaxy is a very large (millions, sometimes even billions) collection of stars held together by gravity and usually the stars revolve around the center, which often contains a supermassive black hole. In addition to stars, galaxies usually contain nebulae, which are large clouds of gas and dust (predominantly hydrogen) which often serve as birthplaces for new star formation. Galaxies are classified by size and structure. The smallest galaxies are called dwarf galaxies, which often orbit slowly at some long distance (hundreds if thousands of light years) around a larger galaxy. We live in the Milky Way, a fairly large (but by no means giant) barred spiral galaxy which has a few dwarf galaxies around it (which may eventually be absorbed into the Milky Way - in fact - the Milky Way likely reached its present size by cannibalizing dwarf galaxies over the eons). Two significant dwarf galaxies near the Milky Way are the Large and Small Magellanic Clouds. Both of these dwarf galaxies are found in the extreme southern part of the sky, so they are best seen from the Southern Hemisphere, which is how they got their names, as they were studied in Ferdinand Magellan's famous first voyage around the world (which Magellan himself did not complete, though some in his crew did - but I digress.) They appear to the naked eye as faint clouds in the night sky, several times larger by comparison than the apparent size of the Moon, but much dimmer than the Moon. There are many other dwarf galaxies (dwarf galaxies are the most common type of galaxy) and they usually contain the name of the constellation they are found in if they are relatively close to us. Most dwarf galaxies are too dim to be seen by the naked eye. Larger galaxies, such as our Milky Way (the word galaxy comes from the Greek root meaning milk as they have a Milky appearance), have more complex structures. There are irregular galaxies, elliptical galaxies, spiral galaxies, and a few other variants. Spiral galaxies may be further subdivided into normal spiral galaxies and barred spiral galaxies, so-called because of a prominent "bar" seen near their centers. Because we are in the Milky Way, we do not get a good look at its structure. That would best be seen from outside the Milky Way. But, after a great deal of effort, we have managed to construct a model of what the Milky Way looks like, and it is a barred spiral galaxy. Reply #433. Jul 15 19, 10:51 AM |
| brm50diboll
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Galaxies tend to have supermassive black holes at their centers. The one at the center of our Milky Way is called Sagittarius A*. Matter caught near the supermassive black hole spirals inward toward the event horizon in an accretion disc, heating up and emitting radiation as it approaches the event horizon. Those supermassive black holes which have little trapped matter (such as ours) are called quiescent. They are difficult to detect and generally are discovered (as Sagittarius A* was) by analyzing the orbits of some nearby stars. Those supermassive black holes with more trapped matter in their accretion disc radiate powerfully particularly in the radio region of the spectrum. Galaxies which contain those type of supermassive black holes are referred to as active galaxies. The nearest active galaxy to us is Centaurus A, a mostly elliptical galaxy with an equatorial dust band which appears to be the result of cannibalism of a spiral galaxy. The most active supermassive black holes are "eating" so much matter that they actually emit more radiation from the black hole than the rest of the galaxy put together. These tend to be very old, very large, and very distant (highly red-shifted from Hubble's Law) galaxies known as quasars. There are no nearby quasars. They likely represent an early stage of galaxy evolution in our universe which has long passed. When we look at quasars 10 billion light years away in our telescopes, we are actually visualizing the distant past of 10 billion years ago. Reply #434. Aug 13 19, 5:04 PM |
| brm50diboll
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Galaxies are organized into larger groups, galaxy clusters and superclusters. Our Milky Way belongs to a gravitationally-bound group of galaxies known as The Local Group. Besides the Milky Way itself, of course, most of the galaxies in The Local Group are dwarf galaxies invisible to the naked eye. The Milky Way is the second-largest member of The Local Group. What is the largest? That would be the Andromeda Galaxy, or M31, about 2.5 million light years away. The Large and Small Magellanic Clouds, both satellite galaxies of the Milky Way, obviously belong to The Local Group. The Pinwheel Galaxy in the constellation Triangulum is another spiral galaxy that belongs to The Local Group. Around 30 galaxies in all belong to The Local Group. Because of Hubble's Law that the universe is expanding, most galaxies are red-shifted, meaning they are moving away from our Milky Way. The only galaxies that are blue-shifted (moving towards us) are certain members of The Local Group. Only because these galaxies are close enough to be gravitationally-bound is blue-shifting possible. The Andromeda Galaxy itself is blue-shifted and moving towards the Milky Way. Estimates are that Andromeda and the Milky Way will collide and eventually merge to form a giant galaxy in about four billion years. No big rush. Reply #435. Sep 20 19, 7:21 PM |
| brm50diboll
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Most of what we know about the universe is actually due to the field of spectroscopy. By analyzing spectra from various celestial bodies, we can learn all sorts of things, particularly their compositions, temperatures, and velocities. Although not immediately apparent to casual observers, spectra contain many small dark lines of various thickness and intensity which can be seen under magnification and whose locations (by specific wavelength) are characteristic of specific chemical elements. Each element has its own unique "fingerprint" of spectral lines that will identify that element as being present in a celestial body when observed in its spectrum. Certain lines are sufficiently famous as to get their own names: the hydrogen alpha lines, the twin calcium lines, the yellow sodium lines, and so forth. But one thing will cause each element's lines in a particular spectrum of a celestial body to be shifted a fixed amount from the usual place: movement of that celestial body. This is known as the Doppler effect (which also applies to sound, though sound doesn't have spectra.) The more the lines are shifted from their rest positions, the faster the celestial body is traveling (radially) with respect to us and there is a well-known formula in physics that allows the amount of shift to calculate the relative radial velocity. If a body is moving generally towards the observer, the spectral lines will be shifted to shorter wavelengths from the rest positions, a phenomenon known as blue-shifting, as blue light is a short wavelength of visible light (actually, violet light has the shortest wavelength of visible light, but I do not know why the phenomenon wasn't called "violet-shifting" - maybe too cumbersome a phrase). If the celestial body is moving generally away from the observer, then the spectral lines are shifted towards longer wavelength as compared to the rest spectrum. That phenomenon is known as red-shifting, as red light has long wavelengths in visible light. The amount of red-shifting can, in some cases, be considerable. Large red shifts mean the body is moving away from us at great speeds, sometimes thousands of kilometers per *second* in extreme cases. There is a general pattern to the spectral shifts seen with distant celestial bodies, particularly galaxies. But I will leave my specific analysis of Hubble's Law and its consequences for the field of cosmology (the study of the universe as a whole) for next time. Reply #436. Oct 08 19, 1:24 PM |
| brm50diboll
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Hubble's Law shows that the velocity at which distant galaxies (those not in the Local Group) are moving away from us is directly proportional to their distance from us. That is, the farther away a galaxy is from us, the faster it is moving away from us. The most distant known galaxies are actually moving away from us at a significant fraction of the speed of light (extremely fast.) How can this be? It is evidence that the universe itself is *expanding*. Expanding into what? Well, there are more dimensions than the three spatial dimensions we can perceive with our senses. How can we understand higher dimensions if they cannot be perceived? Various models are used to try to help people with this difficult concept. On my next post, I will look at one of the more common models used to describe the expansion of the universe. Reply #437. Oct 31 19, 2:40 PM |
| brm50diboll
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There is a transit of Mercury across the Sun ongoing right now. It is being carried live on several YouTube channels. Not particularly exciting, just a small black dot slowly moving across the Sun, but this is a relatively rare event. The next transit of Mercury will not be until 2032. Reply #438. Nov 11 19, 7:31 AM |
| Mixamatosis
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A Fox using science? https://www.youtube.com/watch?v=D2SoGHFM18I Reply #439. Dec 19 19, 1:59 PM |
| brm50diboll
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Very interesting video, Mix. It is known that certain bird species have iron crystals in certain neurons of their brain that are believed to help birds navigate by giving them a sense of the Earth's magnetic field. I don't know about foxes, though. The Russians have selectively bred foxes over several generations to produce tame foxes. Foxes are interesting. Reply #440. Dec 24 19, 11:54 PM |
526 replies. On page 22 of 27 pages. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
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