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April 13

Mean corpuscular hemoglobin concentration (MCMH)

Normal range Mean corpuscular hemoglobin concentration (MCMH) is listed by MedlinePlus as 320 to 360 grams per liter (g/L), meanwhile the UK National Health Service system i'm looking at states the normal range 290-350. That's 30 to the downside and 10 to the upside in terms of variation in normal range. Ostensibly a result which would be considered "normal" by the United States National Library of Medicine can be flagged as "abnormal" in overseas healthcare systems. My questions are:

1) are there any reasons for this variation in normal range?
2) is the "normal range" typically benchmarked against the range of the domestic population?
3) do normal ranges for this parameter vary dependent on variables such as age, gender, ethnicity, or is it a "one-size fits all range"?
4) the result i am looking at specifically is a read of 357, where all other blood test parameters are normal range. This is certainly not medical advice, but scientifically speaking can any deductions or conclusions be drawn from this outlier 357 read in isolation (assuming the data is reliable)? Uhooep (talk) 00:16, 13 April 2019 (UTC)[reply]

Hemispatial neglect, and turning 180 degrees

I have heard of patients with hemispatial neglect who only "noticed" one side of their room: for example, they might keep all their things on the right-hand side, and fail to perceive the left-hand side of the room. But "left" and "right" and relative. When the person turns around 180 degrees to leave the room, what happens? Do they think all their stuff has vanished? Equinox ◑ 02:22, 13 April 2019 (UTC)[reply]

In your own life you can only see things that are roughly in front of you, and unless you have eyes on the back of your head like my sixth grade teacher had you cannot see things when the back of your head is "facing" them. Do the things in front of you disappear when you turn around 180 degrees? --Guy Macon (talk) 02:34, 13 April 2019 (UTC)[reply]

Our article cites research: Left of what? The role of egocentric coordinates in neglect, (1997).

Human perception, and non-normal conditions therein, (including disease and illness) makes for a fascinating field; I think we can safely say that our best research sometimes finds and describes elements of human behavior that we cannot really explain, nor can we easily ascertain a physiological cause. Nimur (talk) 02:37, 13 April 2019 (UTC)[reply]

Heat from heat lamps vs heat from heaters

Besides the fact that maybe it's directional, does the heat from those heat lamps (looks like a light bulb, emits almost only IR and some red light) have anything that makes it therapeutic or in any way different from the heat of another common household heater? I notice it emits some red light, which the heater doesn't, so I wonder whether it is at a higher frequency or concentrated around a different wavelength? --Doroletho (talk) 12:31, 13 April 2019 (UTC)[reply]

Do our articles on Black-body radiation, Color temperature, and Heat therapy answer your question? --Guy Macon (talk) 13:00, 13 April 2019 (UTC)[reply]

Penetration depth of infrared radiation in our skin depends on its wavelength. IR-A (from 0.78 to 1.4 μm) is the most penetrating. For this reason the infrared lamps used for therapeutic purposes produce mainly IR-A radiation. DroneB (talk) 13:39, 13 April 2019 (UTC)[reply]

Depends on the wavelength, depends on the age of the lamp. The wavelength can be chosen to optimise for therapeutic use. Older (1930s-1950s) lamps looked like "lamps" and were sold as therapeutic, but didn't yet have this under control, so they'd also make things uncomfortably hot on the surface. The more specific ones started to appear (as domestic products) in the 1960s. Andy Dingley (talk) 16:36, 13 April 2019 (UTC)[reply]
The heat from an ordinary heater is not at any "frequency"; it's just heat, which is random motion of molecules. If it's an electric heater and you see some light, that's a secondary effect (although it does contribute slightly to heating things as well). It warms the air in the room, which in turn warms your skin (and other objects) by conduction. On the other hand, an IR lamp warms your skin (and other objects) directly by radiation, and as Drone said, the IR may penetrate a little way into your skin, but it does not warm the air. In short, you may feel the heat in a slightly different place in the two cases. That's all. --76.69.46.228 (talk) 02:25, 14 April 2019 (UTC)[reply]
I guess there is a typo in that reply: heater resistance to air and air to skin heat transfer is convection, not conduction. Tigraan^{Click here to contact me} 11:00, 15 April 2019 (UTC)[reply]

An electric heater is also glowing super bright, just in the infrared, which you can't see. Any object at a temperature above absolute zero radiates heat. The amount of heat it radiates at specific wavelengths is dependent on temperature, so only certain temperature objects will give off visible light. As already noted above, see blackbody radiation. The difference between an electric space heater and a heat lamp is that the heat lamp also gives off radiation in the visible range. --Jayron 32 11:35, 15 April 2019 (UTC)[reply]
Well, the real question is how much (for a given heating power) is dissipated in radiation vs. convection for the heating lamp (vs. the heater). Time for the math!

For the heating lamp, I will assume the fraction is somewhat close to 100% (I cannot find specs online).

For the heater, let's compute the blackbody radiation vs. convection by assuming a temperature of about 127°C (clearly that is more than the outside temperature of the heater, though it may be less than the temperature of the resistance inside - I did not find any specs online here either). The value is conveniently taken to have a 100K difference in the convection computation and a 400K absolute temperature in the radiation computation. The blackbody radiation is

\sigma T^{4}=5.67\times 10^{-8}W/m^{2}/K^{4}*(400K)^{4}\approx 1.5kW/m^{2}

. For convection, assuming a heat transfer coefficient of about

10W/K/m^{2}

(highly debatable, but that's the rough ballpark for natural convection), we have about

h\Delta T=10W/K/m^{2}\times 100K=1kW/m^{2}

of convection.

Both values are kind of close, so the fraction is somewhere in the middle, but keep in mind that the computation assumes blackbody radiation. If the outside of the heater is painted "white", the radiation drops proportionnally to the emissivity. Scare quotes around "white", because what will actually matter is the emissivity around peak emission in the infrared, and I highly doubt that visible-white paint is infrared-white. The dominant transfer in that case could be resistance → walls by radiation then walls → air by convection, rather than resistance → air by convection directly. Tigraan^{Click here to contact me} 16:02, 15 April 2019 (UTC)[reply]

April 14

Neutrinos interacting

If two or more neutrinos get close enough, will they interact by the weak force or any other manner? What happens?Rich (talk) 19:52, 14 April 2019 (UTC)[reply]

The chance of interaction is very low. But if an antineutrino and neutrino interact perhaps they will form two photons, or an electron – positron pair if they are higher energy. Graeme Bartlett (talk) 21:43, 14 April 2019 (UTC)[reply]

~~Neutrino § No self interaction says no. (Don't feel bad; it's easy to miss that sentence.)~~ Since they do have mass, in principle they will be gravitationally attracted to each other, but gravity is so weak and the neutrino mass is so incredibly tiny that this will be effectively undetectable. --47.146.63.87 (talk) 21:47, 14 April 2019 (UTC)[reply]

I have edited your link, note that is just a "suggestion". Also neutrinos with energies over 91GeV may scatter off each other using the neutral current. (I don't know if the CMB measurements have ruled this out). Graeme Bartlett (talk) 22:33, 14 April 2019 (UTC)[reply]

Yeah, and then I realized that's the wrong thing: it's about a single particle interacting with itself. I thought I was all clever searching the article for text. --47.146.63.87 (talk) 22:35, 14 April 2019 (UTC)[reply]

Also, this question from the Ref Desk archives may be of interest. --47.146.63.87 (talk) 22:31, 14 April 2019 (UTC)[reply]

This question was also useful. Essentially you are asking if there is a Yukawa potential (from a Yukawa interaction) affecting pairs of neutrinos. This is an interesting search term ... seems like I end up going a different way every time though ... there are a lot of very clever physicists with ideas out there. This time I ended up at [1] talking about how sterile neutrinos (only?) might interact with dark matter. It can be perplexing. But it is interesting, in that I think it is by considering the weak interactions of light particles that we might understand what the universe will do for interesting chemistry, physics, and people in the endless trillions of years after its "death" (in terms of our own high energy, short time scale physics) is over. Wnt (talk) 07:33, 15 April 2019 (UTC)[reply]

April 15

Ocean rocket launches.

How do ocean rocket launches affect-effect the atmosphere of Earth? — Preceding unsigned comment added by 2600:100D:B066:D7C5:5579:804:B6BA:FDF (talk) 17:38, 15 April 2019 (UTC)[reply]

Same way as non-ocean ones. Most launch sites, except the Russians, are (for safety reasons) on the coast anyway. Most large launch vehicles are hydrogen-oxygen fuelled, so their combustion is pretty benign - although there's an energy cost in preparaing both propellants. Solid rocket boosters are using ammonium perchlorate oxidisers with aluminium as a fuel (and some rubber as a binder), so although they're less clean, again their main impact is in the energy which goes to produce the precursor chemicals. A few rockets, military, smaller and the Titan II booster use mixed oxides of nitrogen as an oxidiser, which is unpleasant stuff and powerfully acidic. However on the scale of oceans, and given how few rockets we launch, the overall effects are small. You could calculate the numbers to check, but I'd be interested to compare the total fuel burn of a rocket launch, vs. the driving habits of the large number of spectators watching it. Andy Dingley (talk) 19:16, 15 April 2019 (UTC)[reply]

Foam dropping on the roof in the Notre Dame fire

As the idea of aerial water drops for Notre-Dame de Paris fire was discarded, how effective would foam drops have been instead (or similar less damaging fire retardants)? Don't know if the option of non-water fire retardants has been considered as well. 212.180.235.46 (talk) 22:02, 15 April 2019 (UTC)[reply]

Firefighting foam is usually created by mixing a foam concentrate into the hose stream at the pumper, and it becomes foam as it passes through a nozzle of appropriate design. Occasionally the pumper also adds compressed air to the hose stream to enhance the foam generation at the nozzle.

I have never heard of a firefighting aircraft equipped with either a nozzle or a pump; such aircraft work by simply dropping water or a fire retardant solution on or near the fire. They have no ability to generate foam. Jc3s5h (talk) 22:19, 15 April 2019 (UTC)[reply]

The Notre Dame spire fire was a "fully developed" structure fire. At this stage in a fire, there is often no real way to extinguish it: the tactics used by a fire fighting team are largely designed to prevent the flame from spreading.

You can read more about structure fire fighting at the data and tools section of the National Fire Protection Association website.

A few years ago, NFPA actually published an entire article on a misting fire safety system for St. Patrick's Cathedral, in New York City. They emphasize that the key is to flood the air and the environment early - using nitrogen and water mist to displace oxygen and cool the wood structure before ignition even happens.

"By the time hoses and equipment could be lugged up the spiral steps during a fire event, however, it would likely be too late to mount an effective attack on an attic fire, say fire officials. “Our best estimate is it would probably take somewhere between 20 and 30 minutes before we could get water on the fire if it was up in that area,”..."

Twenty to thirty minutes after ignition is, regrettably, usually too late to save a structure. Even if you can extinguish the flame, the building has already been structurally destroyed by the immense heat. Even parts of the building that have not been directly engulfed by flame have been exposed to radiant heat "flux". Here's a whole book on Fire Safety Challenges of Tall Wood Buildings. The direct exposure to line-of-sight infrared (heat) radiation is often enough to destroy the structure.

Aerial flame retardant will not extinguish a fully-developed structure fire - that's simply not what it is designed to do. For example, the pink gunk that you see Cal Fire Air Attack dropping out of planes and helicopters is "used to slow or retard the spread of a fire" - not to extinguish it.

Nimur (talk) 00:53, 16 April 2019 (UTC)[reply]

Firefighting foam is primarily meant to suppress a fire arising from flammable liquid, by coating the surface and preventing the formation of flammable vapor. It does little to cool and suppress a deep-seated structural fire in materials with some mass - water is the only effective means of stopping such a fire. A fire burning in mass needs masses of water to cool it, since a film will quickly dissipate and heat + fuel+ oxygen = fire again. Acroterion (talk) 01:05, 16 April 2019 (UTC)[reply]

And for the enthusiastic or innovative entrepreneurs in our audience: California's Fire Technology summit took place about a week ago; and the 2019 European Fire Safety Engineering conference is next month. As much as I love technology and fire-safety, we all want to have fewer fires in the first place. Everyone should do the stupidly obvious things to help with fire-prevention, because statistically, most fires are caused by stupid, easy-to-resolve problems. Fires are a lot easier to prevent than they are to extinguish.

Free resources and coloring books for kids: every week is fire prevention week.

Nimur (talk) 01:18, 16 April 2019 (UTC)[reply]

To second Nimur, the point of sprinklers isn't necessarily to put a fire out, it's to react early, sound the alarm, to suppress fire growth until enough resources can be brought to bear to extinguish the fire, and to give building occupants time to safely evacuate. Happily (if that word can be used unironically in this case), life safety wasn't the primary concern in the Notre Dame fire, but it is in most other cases.

The movies where water comes out of the whole ceiling in a fire are nonsense - you want maximum water and maximum pressure at the point of need, not spread out over the whole place (causing water damage in the process), and you can't have 6" pipes all over the place, so individual heads go off when the heat reaches them, and no more. And that water is most definitely not clean - it's usually black from sitting in pipes for years. Acroterion (talk) 01:44, 16 April 2019 (UTC)[reply]

Certainly possible, but no longer necessary. Many sprinkler/deluge systems now have pressurized gas in the pipes to prevent accidental discharge in case the pipe or head gets damaged. The water stays in a reservoir or pumping station and may be discharged/recharged. Matt Deres (talk) 13:40, 16 April 2019 (UTC)[reply]

Back during the September 11th attacks I wondered if you could rig up a cruise missile full of halon to attack a fire. Of course, it would have to do all sorts of probably undoable things like dump most of its fuel at the last minute, then coast to a gentle-ish landing before spraying the stuff out. But ... do you think it's conceivable, or just nuts? Wnt (talk) 04:07, 16 April 2019 (UTC)[reply]

with respect. :-)) Richard Avery (talk) 12:47, 16 April 2019 (UTC)[reply]

On the topic of the original question, this morning (rather, Monday evening), L'Express ran an article, Pourquoi le largage d'eau est impossible (Why aerial water drop was impossible...). Nimur (talk) 16:07, 16 April 2019 (UTC)[reply]

April 16

How to prove flat Earth

believers really mean it, and are not an elaborate parody of, say, Creationists? That is, besides our gut feeling about someone being a real crank and not a caricature of a crank, what scientific method do we have to test this? The question can be extended to Earth representations. How could we conclude whether the author of a drawing believed on a flat Earth? Nowadays, we also draw maps on flat surfaces, but without any intention of making a flat-Earther claim. --Doroletho (talk) 00:02, 16 April 2019 (UTC)[reply]

If there were a scientific method to prove when someone is being sincere, the world would be a very different place. Someguy1221 (talk) 00:08, 16 April 2019 (UTC)[reply]

Well, sometimes you can prove whether someone truly believes in some crazy stuff. Some HIV infected AIDS denialists didn't get anti-viral treatment. Some breatharians starved to death. --Doroletho (talk) 00:14, 16 April 2019 (UTC)[reply]

I would challenge your premise that this constitutes proof. I am completely ready to believe that some people will allow themselves to die for the sake of pride. But if you are simply asking for that degree of commitment, well, I'm certainly not aware of any flat earthers who have made realistic efforts to fund a private spaceflight or navigate to the edge of the world. Considering that freakin' teenagers have circumnavigated the globe by sail, one might conclude they are deliberately avoiding feasible tests that could prove their hypothesis wrong, similar to how most pseudomedical and pseudoscientific studies are designed in such a way that no conclusions can actually be drawn. Make of that what you will. Someguy1221 (talk) 04:22, 16 April 2019 (UTC)[reply]

Those teens made sure to stay away from the edge. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:50, 16 April 2019 (UTC)[reply]

Well there was this infamous example which failed spectacularly [2] www.gofundme.com/showBoBthecurve. However to be fair, even if I did believe in a flat earth and wanted to prove it, I'm not sure that giving money to B.o.B is something I'd consider. Especially since it's not really clear he had a coherent and realistic plan of how to spend the money. And although the media may sometimes overplay it, [3], it's not like flat earthers aren't willing to spend money attending conferences and such although the travel and socialisation may be sufficient perks for the money spent. The OP is correct it can be difficult know what people are really thinking when they make outrageous claims e.g. [4] [5] Nil Einne (talk) 01:36, 17 April 2019 (UTC)[reply]

We have a well-referenced article on pseudoscience, citing dozens of books and papers that analyze and describe pseudoscience at large. If you don't find our encyclopedia sufficiently detailed, the Plato Encyclopedia also has a well-referenced article, Science and Pseudo-Science.

What more do you think we can we say on this topic that hasn't already been said elsewhere?

Nimur (talk) 00:41, 16 April 2019 (UTC)[reply]

Related to this topic, there is a blog "100 Proofs that the Earth is a Globe" currently being written by physicist and web-cartoonist David Morgan-Mar, which as of this date has got up to Proof #10. Necessarily he analyses claimed proofs of a flat Earth in the process. {The poster formerly known as 87.81.230.195} 2.122.2.132 (talk) 06:26, 16 April 2019 (UTC)[reply]

I read the OP to question about more ancient maps and the discovery that the earth was indeed a globe at a later stage in history and thereby how would one prove if the aforementioned map maker had been aware of the earth being a sphere, or if they had believed the earth to be flat. — Preceding unsigned comment added by 81.131.40.58 (talk) 08:19, 16 April 2019 (UTC)[reply]

The main "proof" of a flat earth, as a cultural phenomenon rather than geodesy is that, "NASA says it is, I disbelieve everything The Government tells me on principle, I am supported in this by my group of friends and our venal leaders." So any appeals to logic or measurement are largely irrelevant to that.

There is very little simple 'ignorance' in the FE movements, certainly not in the more vocal advocates. Andy Dingley (talk) 09:11, 16 April 2019 (UTC)[reply]

Jonathan Swift, in 1721, said "Reasoning will never make a Man correct an ill Opinion, which by Reasoning he never acquired". 300 years later, humanity has not gotten much better at this. Here's a decent article from a neuroscience perspective that explains why actual facts aren't that relevant to changing people's minds on anything. --Jayron 32 12:25, 16 April 2019 (UTC)[reply]

The kind of "thinking" on the flat earth is the same as the claims that we never went to the moon. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:16, 16 April 2019 (UTC)[reply]

"Any fool can look out his window and see that the earth is flat." --Guy Macon (talk) 14:50, 16 April 2019 (UTC)[reply]

There are experiments such as the Bedford Level experiment, which Flat-Earthers claim shows that the Earth is flat. The Bedford Level is a slow flat canalized river, 6 miles (10km) long. It is long enough to show the horizon distance, when there is no wind. A strong wind can force water from one end of a lake to the other, causing a slight difference in height. If the experiment is done correctly, then it does show the expected curvature. LongHairedFop (talk) 20:49, 16 April 2019 (UTC)[reply]

Like the Universe, the Earth is approximately flat. Wnt (talk) 03:45, 17 April 2019 (UTC)[reply]

Some people believe their own lies [6]. 2A00:23C2:B80:4500:E5AF:BD7B:5868:3521 (talk) 12:19, 17 April 2019 (UTC)[reply]

I don't have a good idea how flat-earthers handwave away time zones (etc.), but two sets of simultaneously-taken images, one set from several points on Earth at similar latitudes but widely spaced in longitude, and a second set at a spread in latitude from sites at the same longitude, showing the Sun's (or Moon's) altitude and azimuth from those positions, could in principle provide data that would be awkward for the approximately-spherical Earth model. Such data does in actuality give results which are incompatible with a flat-Earth model, of course. I also would need to think about how they handwave away the rotated appearance of the Moon seen at very different latitudes; if you are used to living at around 40 degrees N, when you arrive at 30 degrees S for the first time and look at the sky, the Moon "is upside down". BSVulturis (talk) 05:37, 19 April 2019 (UTC)[reply]

hibernation

Hibernators need to put on weight before undergoing hibernation. But what happens to the unfortunate animal that didn't manage to build up enough body fat before winter hits? I'm guessing it could be one of the follow scenarios:

1. The body's internal mechanisms knows there's not enough body fat to hibernate, so it skips/delays hibernation until enough food is found.

2. The body doesn't know or doesn't care that there's not enough body fat, and enters hibernation anyways. The animal quietly dies during hibernation.

3. The body doesn't know or doesn't care that there's not enough body fat, and enters hibernation anyways. Hibernation continues for as long as possible until all the available body fat is used up, and the animal exits hibernation early. There's not enough fat to continue hibernation, so the animal's only choice is to find food in the winter. This similar to scenario 1 except delayed by a few months.

Which scenario is the closest one?

I'm interested in the behavior of hibernators in general and the American black bear in particular. Thanks. Mũeller (talk) 07:38, 16 April 2019 (UTC)[reply]

Keep in mind that bears are not the only kind of hibernator. Hummingbirds have a form of hibernation that happens every night. and one human supposedly hibernated for 32 years. --Guy Macon (talk) 12:13, 16 April 2019 (UTC)[reply]

For the human part, emphasis on "supposedly". (She was drinking milk and trimming her nails... even "sleeping" sounds unlikely, let alone anything else close to "hibernating".) Tigraan^{Click here to contact me} 08:32, 19 April 2019 (UTC)[reply]

Not direct answers, but what I've found implies 1 or 3. Bears do not usually die of starvation in dens, most deaths from starvation are before or after hibernation and involve primarily cubs and yearlings; In northeastern Minnesota, where food is unavailable for about seven months and bears hibernate for five to seven months, it was noted that while no Ursus americanus - American black bears died of starvation while hibernating, some died in spring after emerging from the den.

Bears, incidentally, are not a very good example of hibernators, as their state of torpor is not the same as classic hibernation (although definitions vary). Henry ^Flower 14:51, 16 April 2019 (UTC)[reply]

When was and for how long was the background radiation around room temperature?

I have heard but can’t find remark by some famous scientist that the universe was once at room temperature. Does this refer to the presently cold microwave background radiation? Anyway, how long ago and for how long did the temperature last between about 100 fahrenheit to 70 fahrenheit? Was the universe made ip of atoms at that time? How dense/large was the universe? I don’t remember if the famous scientist said that was a good time for organic chemicals to form and biochemistry to happen, but I got the impression that was what he or she was thinking about.Rich (talk) 14:03, 16 April 2019 (UTC)[reply]

See Chronology of the universe. According to the chart there, the universe was on the order of 10³ K (which is the ballpark of "room temperature" as close as we can get) sometime during the "cosmological Dark Ages" which would have been about 380,000 - 150 million years after the big bang. This time frame is when the universe cooled from 6000K down to about 60K, and given that room temperature (basically 300K or so) is between those numbers, there's you time frame, probably closer to the end than the beginning of that time period. --Jayron 32 14:09, 16 April 2019 (UTC)[reply]

The current temperature of the microwave background is about 2.7 K. So, the room temperature (~ 300 K) was at z ~ 100, which corresponds to the age of the universe of about 10-15 million years. At that time there was no stars, galaxies or any other celestial objects. The universe consisted of cool hydrogen-helium gas with small admixture of deuterium and lithium. So, no organic compounds could exist at that time. Ruslik_Zero 20:53, 16 April 2019 (UTC)[reply]

Well couldn’t carbon have been created by cosmic rays striking beryllium or lithium?Rich (talk) 07:40, 17 April 2019 (UTC)[reply]

How so? In order to get a larger atom, you need to have extremely high-pressure inside-of-a-star type situation, where nuclear fusion can happen. A "cosmic ray" striking a smaller atom cannot magically make it become larger! See Stellar nucleosynthesis. For carbon, you need the Triple-alpha process. In Big Bang nucleosynthesis, you don't get any atoms larger than beryllium, and you don't get any stable nuclei larger than lithium. There are some wacky hypotheses that carbon-based life could have evolved in a narrow epoch when liquid water could have formed in the ambient universe and where there was a nearby star to provide a source of carbon, see Chronology of the universe in the section titled Speculative "habitable epoch", and I think the emphasis on that is "speculative". I don't know that anyone much takes it seriously. --Jayron 32 12:00, 17 April 2019 (UTC)[reply]

The beryllium article says energetic alpha particles can make a beryllium nucleus into a carbon 12 nucleus.Rich (talk) 05:06, 18 April 2019 (UTC)[reply]

So it does. However, that is beryllium-9. There wasn't enough stable beryllium-9 around prior to star formation for that to be a thing. Any beryllium created would be Be-7, and that would have decayed into lithium. And that also would not have formed carbon in the method described in the beryllium article, which requires Be-9. See Big Bang nucleosynthesis. I quote "Essentially all of the elements that are heavier than lithium were created much later, by stellar nucleosynthesis in evolving and exploding stars." --Jayron 32 12:30, 18 April 2019 (UTC)[reply]

Very very very thin gas right? Sagittarian Milky Way (talk) 02:20, 17 April 2019 (UTC)[reply]

Chronology of the universe § A more detailed summary actually gives some figures for density at several points. Already, when the universe was about 20 minutes old and Big Bang nucleosynthesis ceased, the spherical volume of space which will become the observable universe is about 300 light-years in radius, baryonic matter density is on the order of 4 grams per m³ (about 0.3% of sea level air density). --47.146.63.87 (talk) 07:28, 17 April 2019 (UTC)[reply]

Effect of path of Bluetooth cable on signal strength

I'm making a mount for my Bluetooth antenna to attach it to my desk. I have a question regarding the cable that connects the USB Bluetooth dongle to the amplifier. Does it matter what shape it forms? In [my first attempt] (I will have to scrap this for unrelated reasons), the cable forms an S or N shape, but I could also design a mount to produce a U shape or, much less conveniently, a straight line. Does the shape of this cable have an affect on the signal? Thanks. 78.149.180.132 (talk) 21:16, 16 April 2019 (UTC)[reply]

Assuming the Coaxial cable has Characteristic impedance that matches the dongle and amplifier (usually 50 or 75 ohms) at Bluetooth frequencies 2.400 to 2.485 GHz, its shape will have very little effect (not affect). DroneB (talk) 00:31, 17 April 2019 (UTC)[reply]

April 17

Interstellar Propulsion

I wish you all a good day!

I was wondering if actual technologies exist, which could allow humanity to travel across the galaxy. I recall that a good friend of mine has had a book during our time at high school which dealt with such ideas and it offered quite outlandish ideas. I remember that he spoke of a "photon rocket", which he called "the only existing way to actually travel across the known universe". I was wondering if there ever were plans to build a real interstellar spaceship.

Thank you most kindly for your answers!--2A02:120B:2C17:3CA0:D43D:F270:18DE:3724 (talk) 10:06, 17 April 2019 (UTC)[reply]

There are a number of technologies that could be described that way, and I would point you towards our article on Laser propulsion. As mentioned there, testing is ongoing for several of these. In the near future, you are only likely to see them used to propel very very tiny probes. Generally, the real devil in interstellar travel is the rocket equation, i.e. that fuel costs increase exponentially with total required delta-v for the payload. Pushing a colony ship to a good fraction the speed of light using conventional rockets would take a fuel tank heavier than the observable universe, for instance. Terrible. But if you can propel a spacecraft by shooting it with a laser beam from a ground station, and you can keep that beam on target over a considerable distance, you are kind of cheating - you don't need to take your fuel with you, and in scientific terms that saves hella weight. Someguy1221 (talk) 10:24, 17 April 2019 (UTC)[reply]

Possibly he is thinking of Breakthrough Starshot, which is not a way for people to travel but is at least a plan. The closest to a plan for humans I recall is Project Orion and subsequent proposals for nuclear pulse propulsion which seems like it would be ... inelegant at the logistical level. But reading through that article I see some interesting developments toward a fusion rocket which might be more reasonable. Wnt (talk) 11:31, 17 April 2019 (UTC)[reply]

Even with a ship taking thousands of years a big problem would then be slowing down at the far end. My guess is that the initial effort to make a workable system would be to somehow get robots to the far end so they can build something like a laser system to slow things down as they reached there. A huge undertaking but mainly of technology rather than materials. As to sending grown people - unlikely. More likely grow people at the far end. Dmcq (talk) 12:14, 17 April 2019 (UTC)[reply]

Thank you very much, Gentlemen!--2A02:120B:2C17:3CA0:7443:7455:66DD:2543 (talk) 18:06, 17 April 2019 (UTC)[reply]

Or just transform into a machine civilization and then upload the digital brain contents via radio or laser beams to another civilization far away. There is then no need to build any spacecraft. The transmissions can be one way communications. You can just send a message that explains how to decode the next message after which the next message containing the data is sent. That data then also contains the instructions on how to build a machine that can run the algorithm that will render some particular individual. This entire message is then repeated over and over again. Count Iblis (talk) 21:58, 17 April 2019 (UTC)[reply]

rather less feasible and with unknown technology and unknown aliens! At least what I was saying will soon be feasible and could be replicated in quantity. The only real downer is that the various steps would take a very long time. Dmcq (talk) 22:29, 17 April 2019 (UTC)[reply]

It could actually be faster to communicate with aliens to go there than send messages. That is, people on a ship going close to the speed of light would have time dilation effects which would make the decades, centuries, or millennia seem like only years aboard the ship. Of course, those back on Earth wouldn't get in on the communication any sooner. SinisterLefty (talk) 19:17, 18 April 2019 (UTC)[reply]

There are different ideas like the Bussard ramscoop as a method of interstellar travel, i.e. taking some number of years to reach nearby stars that are a few light-years away. Travelling across the galaxy (diameter around 185,000 light years iirc) without faster-than-light travel is something else entirely. I can't even think of any science fiction where that happens, though there probably is some. 67.164.113.165 (talk) 21:08, 18 April 2019 (UTC)[reply]

Tau Zero comes to mind. 93.136.13.167 (talk) 17:24, 19 April 2019 (UTC)[reply]

April 18

illegal street drugs causing death

In the news there's always stories of somebody taking an illegal drug and dying, obviously that doesn't happen in the vast majority of cases, but what illegal drugs are least/most likely to cause death when bought on the street. Including cases where the person buying the drug gets a tainted supply, which I assume is more likely for certain drugs. — Preceding unsigned comment added by Xcarry (talk • contribs) 10:53, 18 April 2019 (UTC)[reply]

That's going to be a complicated question to answer. Is a drug more lethal because it frequently kills quickly or because it creates chronic users who die slowly? Many users also combine drugs in various ways or use different drugs at different times for different effects. When they die, is it due to the last drug they took, weakness from the stronger drugs' effects, or the combination? Our article at Drug overdose is a reasonable place to start and see also the references cited and external links. Matt Deres (talk) 13:35, 18 April 2019 (UTC)[reply]

Here are drug factsheets from the United States Drug Enforcement Agency.

Beware of the incredible power of conditional probability when comparing diverse different things that are more- or less- likely.

Nimur (talk) 15:10, 18 April 2019 (UTC)[reply]

I'm more talking about if a normal amount is taken just one time, what drugs are least/most likely to cause death, either because the type of drug is often tainted or because some people just have bad reactions to it. — Preceding unsigned comment added by Xcarry (talk • contribs) 15:58, 18 April 2019 (UTC)[reply]

The class of synthetic opioids including fentanyl and its various analogues is often cited for being particularly deadly; the opioid crisis has lots of numbers on the deadliness of these drugs. See File:US timeline. Deaths involving other synthetic opioids, predominately Fentanyl.jpg for some data. --Jayron 32 16:14, 18 April 2019 (UTC)[reply]

An interesting side issue is whether they would be more or less deadly if legal. Before heroin was made illegal, many heroin addicts held down jobs and pretty much lived a normal life. During alcohol prohibition in the US many people went blind from bad booze, but that never happens today (alcohol still kills a bunch of people every year, but they don't go blind). The government adding poison and letting the poisoned booze re-enter the market didn't help... Tobacco kills many people in the long run, but overdoses are rare. Tylenol is legal and nonaddictive, but paracetamol hepatotoxicity is by far the most common cause of acute liver failure in both the United States and the United Kingdom and Paracetamol overdose results in more calls to poison control centers in the US than overdose of any other pharmacological substance. It's complicated. --Guy Macon (talk) 16:49, 18 April 2019 (UTC)[reply]

Clarification for North American readers: paracetamol is another name for acetaminophen, the active ingredient in Tylenol. --76.69.46.228 (talk) 07:15, 19 April 2019 (UTC)[reply]

The question of whether the legal system and criminalization of drug use is the correct tool to improve health outcomes from drug use is indeed an issue. We only have the data we have today; however you do see that in places where drug use is treated as a health issue rather than a criminality issue, you do see decreased fatality rates. Here is a good article with lots of data on the effect of the changes to the drug policy of Portugal; the numbers are rather stark; it is almost alone among Western nations do see a decrease in opioid-based fatalities during the opioid crisis. It is only one data point, but it does seem to bear out that making drugs illegal makes them more deadly. --Jayron 32 17:12, 18 April 2019 (UTC)[reply]

N.b. Jayron's claim about Portugal compared with other Western conutries may or may not be true, but it doesn't seem to appear in the article cited. The implication that Western nations other than the US have recently been suffering an opioid crisis also does not seem to be supported by our article. Henry ^Flower 17:37, 18 April 2019 (UTC)[reply]

Our article does not do a good job of showing the worldwide perspective on it, it is very US centric, but the article I cited (which itself has many connections and citations to the research) does make the case that Portugal's trends on negative health outcomes due to drug use have gone in the opposite direction from those countries that have maintained a criminality-as-treatment for drug use. You can see some data here and here for example. Portugal consistently ranks very low in comparison to other countries (for example, less than 1/3 the death rate for the EU average, and about 1/10th that of the US) Other countries with low drug death rates like Italy and the Netherlands have also, to some extent, deal with drug users differently than those countries with higher death rates like the US and Canada. Generally, those countries that treat drug users with prison have higher death rates, and those that use other methods (such as court-enforced medical treatment or therapy) have lower rates. --Jayron 32 18:14, 18 April 2019 (UTC)[reply]

I see nothing in either of those charts about a decrease in Portugal's opioid-based fatalities, nor about the changes in other Western countries. Henry ^Flower 21:00, 18 April 2019 (UTC)[reply]

Paraquat sprayed on marijuana crops also may have made it more dangerous. It's bizarre how the original intent of the law, to protect people from a supposed dangerous chemical (THC), was perverted to intentionally expose people to a definitely dangerous chemical (paraquat). Those living in the areas sprayed would have been the main victims, but those who consumed it may also have been affected.SinisterLefty (talk) 19:08, 18 April 2019 (UTC)[reply]

@SinisterLefty: As described at your link, the paraquat scare was brief. The fear of chemical contamination was never really substantiated. In general, the intent of the War on Drugs is not to stop drug use, but to raise the price of drugs as high as possible, and control who is able to sell them with impunity, so as to deliver as much profit as possible into the hands of selected organizations. Anything that potentially interferes with the market -- whether it be detectable herbicide residues, domestic sales of methamphetamine precursors usable by local "cooks", or sales of fake drugs by cheaters who would ruin the drive-through drug markets of the inner cities -- will be quickly suppressed. Wnt (talk) 23:19, 19 April 2019 (UTC)[reply]

Portugal is a poor country. Do its citizens have the wherewithal to expend large sums of money on drugs? The obvious place to look for information on this topic is pt:wp (e.g. this article: pt:Legalização de drogas). A skim through this article reveals the following:

Na legislação internacional, existem iniciativas a tal prática na Holanda, Canadá, Argentina, Chile, Inglaterra e Portugal. Observa-se que a política de redução de danos nesses países vem acompanhada de um esquema para tratar o usuário crônico por meio de um sistema de saúde.

There are inline citations. The translation is:

In the international legislation, there exist initiatives to such practice in Holland, Canada, Argentina, Chile, England and Portugal. It is observed that the policy of reduction of damages in these countries comes accompanied by a scheme to treat the chronic user by means of a system of health.

It has been noted that the inhabitants of countries which have access to health services live longer than those who don't. 2A00:23A8:830:A600:3089:80E0:7D9B:95DA (talk) 11:59, 19 April 2019 (UTC)[reply]

At around US$30K annual income, Portugese citizens can certainly afford drugs: [7]. SinisterLefty (talk) 22:00, 19 April 2019 (UTC)[reply]

One reason why opioid deaths have gone up in the US is the push by Big Pharma to have pain level considered as "vital sign": [8]. Prior to this, pain management was considered incidental to treatment, meaning they would give pain killers such as opiods only when the patient requested them. But now in many places patients are asked what their pain level is on a scale of 0-10, and if it's not zero, they are offered those drugs. And many patients assume the medical staff knows what is best, so take those drugs, which they wouldn't have, if they had to request them. The problem, then, is that a certain percentage of people given opioids become addicted. They can continue to get prescriptions for some time, but when they are eventually "cut off", they often turn to the illegal varieties. This process can take years, but often leads to death. The long period between the two has obfuscated the link. SinisterLefty (talk) 22:28, 19 April 2019 (UTC)[reply]

Also note that opioids while having the potential to cause problems via addiction, also have health benefits relative to using NSAIDs, as the latter type of drugs can cause fatal stomach bleeding, while using PPIs to prevent such side effects has been linked to cardiovascular disease, reduced kidney function and dementia. These side effects of PPIs seem to be caused by the PPIs inhibiting the function of lysosomes. Less people dying due to opioid overdose if many more people switch to NSAIDs may then cause a net increase in the number of deaths due to stomach bleeds, heart attacks, strokes, kidney failure and we may not even notice such an increase. Count Iblis (talk) 18:19, 20 April 2019 (UTC)[reply]

Odd TV antenna behavior

I have a TV antenna with a splitter, connected to 2 TVs. The reception on a certain channel is poor when TV B is on only. But when I turn TV A on and put it on the same channel, then TV B all of a sudden has better reception on that same channel. The two TVs are different brands (Samsung for B and Element for A) and are about a meter apart. TV A is connected directly to the antenna splitter while TV B is connected via an Ematic brand digital video recorder. Can anyone explain this ? SinisterLefty (talk) 19:23, 18 April 2019 (UTC)[reply]

I don't have an answer, but is it possible for you to swap the two TVs' connections to the splitter? If the phenomenon also swaps it will indicate that it's internal to the splitter. {The poster formerly known as 87.81.230.195} 2.122.2.132 (talk) 19:47, 18 April 2019 (UTC)[reply]

One possibility: see our article on characteristic impedance. Basically, the signal moves down the cable. If the cable is infinitely long, it never bounces back. If it stops at a TV that has the same impedance as the cable, it doesn't bounce back. If, however, the end of the cable is either shorted or open (unplugged) the signal bounces back. See Signal reflection and Reflections of signals on conducting lines. What may be happening is that the impedance at at the frequency of the TV channel is changing as you change channels.

Another possibility: the TV is actually generating an interfering signal and feeding it back down the cable, and the interfering signal changes as you change channels

Or it could be something weird happening in the splitter. Splutters are cheap, somitbmight be worth trying to replace tyhe splitter and see if the problem gets better. --Guy Macon (talk) 22:21, 18 April 2019 (UTC)[reply]

Signal reflections sounds like the most likely explanation so far. Thanks. SinisterLefty (talk) 00:11, 19 April 2019 (UTC)[reply]

April 19

Fear of too many moving objects

Is there a name for a fear of too many moving objects? I know a few people who have this. For example, if they see a big school of sardines on tv, they get upset. Anna Frodesiak (talk) 05:23, 19 April 2019 (UTC)[reply]

Googling the subject yields the term "kinetophobia", which Wikipedia does not have a separate article about. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:06, 19 April 2019 (UTC)[reply]

Kinetophobia symptoms, causes, treatments, etc. also known as kinesophobia. DroneB (talk) 11:14, 19 April 2019 (UTC)[reply]

Well, I'll be darned. Thanks folks. There is Wikipedia:Articles for deletion/Kinetophobia. So, article-worthy? Anna Frodesiak (talk) 11:23, 19 April 2019 (UTC)[reply]

Wikipedia has the sum of human knowledge. Except when it doesn't. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:07, 19 April 2019 (UTC)[reply]

Hang on, this seems like a different thing. Anna Frodesiak (talk) 11:25, 19 April 2019 (UTC)[reply]

We mere mortals cannot see that link. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:06, 19 April 2019 (UTC)[reply]

Many phobia names are coined without any clinical meaning behind them. They're not regulated, per se, so if you suffer from some anxiety about something you can just make up a -phobia name for it. See List of phobias, especially the text at the top, for more on this phenomenon. Note that many of the phobias on that list (of which kinetophobia is not one) are stubs of questionable encyclopedic value. I would be surprised if many do not meet the same fate as the one above. Matt Deres (talk) 12:46, 19 April 2019 (UTC)[reply]

I suspect surviving something like this would cause an extreme version of this fear :-) BK really was an amazing performer. MarnetteD|Talk 18:14, 19 April 2019 (UTC) [reply]

It would surprise me if this wasn't a thing. A quick web search finds a repeated passage about kids with autism:

In fact, 70 years ago, Leo Kanner wrote in his initial account of autism that “loud noises and moving objects” are “reacted to with horror” and things like “tricycles, swings, elevators, vacuum cleaners, running water, gas burners, mechanical toys, egg beaters, even the wind could on occasions bring about a major panic.”[9]

though that doesn't seem limited to large numbers of moving objects. 67.164.113.165 (talk) 07:02, 20 April 2019 (UTC)[reply]

Double bass sound

How can the acoustic double bass produce audible frequencies below those supported by internal maximum dimension of the body? Ie. Body max internal dimension is about 1.5m, but the lower frequency (E1) is at 41 Hz . 80.2.20.230 (talk) 19:55, 19 April 2019 (UTC)[reply]

If the linear density of the strings is high enough, then the lower frequencies are achievable. Mikenorton (talk) 20:53, 19 April 2019 (UTC)[reply]

When vocal cords vibrate at a low frequency then a bass sound is produced. It is not required to resonate in any cavity. Ruslik_Zero 20:58, 19 April 2019 (UTC)[reply]

Subharmonics? 67.164.113.165 (talk) 07:04, 20 April 2019 (UTC)[reply]

so if the strings make the sound alone, why do you need that big doghouse? My question related to the size of the resonant cavity used for so called ampl7fication of the low frequencies. If the body is not large enough to be resonant at the low frequencies, how can it project rhe sound into the air? So how does a double bass produce those low frequency fundamentals, or does it?80.2.20.166 (talk) 13:46, 20 April 2019 (UTC)[reply]

You are incorrect in your assumption that the body of a stringed instrument does not increase the projected volume below resonance. See the measurements at [10]. --Guy Macon (talk) 14:42, 20 April 2019 (UTC)[reply]

Hmm. Did you actually read Zevins report? If so, you will have noticed that his resonance tests on the double bass (Fig 7), show no (or very little) response below about 120Hz when excited from between 10Hz and 1000Hz by a transducer. This is because the body of the bass is not large enough for any lower resonance. If we consider the (internal) resonant chamber dimensions of a typical double bass as being about 4.5 feet maximum in any direction, we can see this length corresopnds approximately to a half wavelength of sound in air of about 120Hz. Is this a coincidence?

So my question remains: How does one percieve low pitch sounds that the double bass body plainly cannot generate? 213.205.242.157 (talk) 18:48, 20 April 2019 (UTC)[reply]

The E1 string of a Double bass vibrates at 41.2 Hz, something you can both see and hear even if the string were suspended between unyielding solid supports. The mass of air moved directly by the thin string is tiny and that source of sound is almost neglible. However in this instrument, as with others in the Violin family, a bridge transmits string vibrations to the large-area soundboard i.e. the front face of the instrument. This soundboard is flexible, it serves to couple the string vibrations to a large air mass and that is how a clearly perceptible volume of sound is achieved. The question seems to imply that Helmholtz resonance of the double bass body cavity is essential to all sound production but that is not so. The distinctive perceived musical quality of the E1 note from this instrument depends on the wide range of harmonic and non-harmonic frequency components generated by the player stroking the bow against a part of the string. Body resonances, both of the enclosed cavity and of the body structure affect most of the audible frequency range but the fundamental frequency of the E1 note is, in isolation as considered by the question, a pure sinusoidal wave of lesser musical interest. DroneB (talk) 20:27, 20 April 2019 (UTC)[reply]

so if the Helmholtz resonance of the body is not necessary, why not just use a plain sheet of wood to transmit the vibrations to the air.? If one tried this, i think it would be found that there was very little transmission of the very low frequencies into the air. Also the bass woukd sound lousy as that would be fewer overtones generated. So why can one hear low frequencies that cannot be generated by any element of the instrument. The double bass article is silent on this issue, but it should not be.80.2.21.198 (talk) 21:07, 20 April 2019 (UTC)[reply]

April 20

TFA?

See Wikipedia talk:Featured articles#2019 redefinition of SI base units. --Guy Macon (talk) 15:31, 20 April 2019 (UTC)[reply]