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January 29

Challenger Deep vs. mantle and magma

If you traveled through the Earth's crust horizontally (keeping with the curvature of the Earth) from the bottom of Challenger Deep, would you remain within the oceanic crust, or would you eventually hit magma (outside of a mid-ocean ridge or other volcanic event) or even the mantle layer? — Preceding unsigned comment added by 67.42.179.140 (talk) 09:47, 29 January 2016 (UTC)[reply]

Take a look at this cross section, you will see that you don't have to go very far away from the trench at 10.9 km depth to get below the oceanic crust and into the mantle. Further to the west and you would be into the asthenosphere in the back-arc basin, which is not 'magma' just hot enough mantle that it flows. At the spreading centre in the back arc-basin there will be a series of magma chambers that you would almost certainly run into. Mikenorton (talk) 10:18, 29 January 2016 (UTC)[reply]

Thank you sincerely! 67.42.179.140 (talk) 23:38, 29 January 2016 (UTC)[reply]

Dateline as applied to historical dates

I have frequently wondered about historical dates and if they were in USA time and date or, if occurring West of the International Date Line. Example: We are told a time (presumably local) and a date for the bombing of Hiroshima, Japan: August 6, 1945. But being far West of the date-line it was a day later in Japan. So if the bombing occurred on August 6 US date, then Hiroshima was bombed the morning of August 7, 1945. So many events in the pacific do not correct for this obvious modifier of date an time. Why not and did Hiroshima get leveled on Aug 7, in actuality? - When it was still August 6 hereSteveSmS 10:30, 29 January 2016 (UTC) — Preceding unsigned comment added by Smshepard51 (talk • contribs)

It depends on the circumstances, but for most events which are tied to a single country, local time is used (international events sometimes use UTC). The Hiroshima bombing happened on August 6th 8:15 AM Japan time, which would have been August 5th for most of the United States (except Hawaii) - the official transcript of Truman's announcement of the bombing says "On August 6, while returning from the Potsdam Conference aboard the U.S.S. Augusta, the President was handed a message from Secretary Stimson informing him that the bomb had been dropped at 7:15 p.m. on August 5.", which would be Eastern Time. Smurrayinchester 13:01, 29 January 2016 (UTC)[reply]

(A weirder example of this practice: Western media talks about Russia's October Revolution, even though according to Western calendars, it happened in November - at that time, Russia's Julian calendar was about two weeks behind the more widely used Gregorian calendar). Smurrayinchester 13:06, 29 January 2016 (UTC)[reply]

Also in World War I, the Armistice took effect at 11 am French and British time, but in Canada it's commemorated in Remembrance Day ceremonies at 11 am local time. It wasn't even 11 am in Germany: the Western Front was effectively a time zone boundary, and it was noon on the other side. Since I learned this, I've liked to imagine German soldiers taking prisoners and telling them to "drop your weapons and set your watches ahead 1 hour!" --76.69.45.64 (talk) 15:16, 29 January 2016 (UTC)[reply]

And, of course, the French Revolutionary calendar, which decimalized the months, was used to mark key events during the Revolution. Pro-monarchy revisionist historians have back-filled our textbooks with historically-equivalent Gregorian calendar dates, so we know (for example) when Robespierre was guillotined. As any staunch Republican can tell you, 18 Brumaire was the day that freedom ended, or began, or something. It's very difficult for me to keep dates and Republican-ideologies straight.

Equally problematic are those historical events that took place in space: for example, during the Apollo 11 mission, humans first set foot upon the moon either July 20 or July 21, depending on your time zone. The mission used Houston time for many flight purposes, so we often commemorate July 20. On the moon, both July 20 and July 21 occur on the same lunar day - in fact, half of the month of July is the same lunar day - but regrettably, few humans use the lunar day as the defining astronomical event for their calendar. Some great distant time in the future, when errors of a few thousand hours accumulate, I suspect the unix epoch will be defined to begin at the exact instant humans first walked on the moon, with error of just a few thousand hours or so.

Nimur (talk) 16:32, 29 January 2016 (UTC)[reply]

And, of course, the French had the Thermidorian Reaction, which like the October Revolution, only makes sense on the local calendar. The rest of us would have called it the July Revolution or July Reaction, but historiographically speaking, there's another coup d'etat in July, and we call that the July Revolution. --Jayron 32 17:13, 29 January 2016 (UTC)[reply]

Not to be confused with the Thermite reaction. --ColinFine (talk) 22:31, 31 January 2016 (UTC) [reply]

Not to be confused with the termite reaction. StuRat (talk) 08:19, 1 February 2016 (UTC) [reply]

Gas giants and fast winds

When I watch astronomy documentaries that feature gas giants, I always hear about the extreme wind speeds and how devastating it would be on Earth. To me, this does not seem to be a fair comparison - wind speed is a relative quantity. Doesn't the danger just depend on how rapidly you navigate between different air currents? Could you comfortably fly at minimum true airspeed in a non-turbulent, 800km per hour air current on Jupiter? Plasmic Physics (talk) 10:30, 29 January 2016 (UTC)[reply]

Well yes, the devastation is only happening on Earth because we have 1. a ground that is not moving in sync with the winds and 2. things that are fixed to the ground. if you don't have that, there is nothing to "devastate".--74.101.111.23 (talk) 14:46, 29 January 2016 (UTC)[reply]

Right, and if Jupiter had a surface like Earth, that would slow the winds down dramatically. Similarly, on Earth, you tend to get much higher winds aloft, where there is no friction with the ground. Assuming your spaceship moved with the wind, the only devastation caused by it would be when you hit an eddy between two different bands (or spots), with winds moving in opposite directions. Then you would be in for some major turbulence. I wonder if we could make a ship that could survive that. StuRat (talk) 18:08, 29 January 2016 (UTC)[reply]

Jupiter's atmosphere is not "air" as we know it. If the pressure did not kill you immediately, you would suffocate trying to breathe the 89% hydrogen plus 10% helium mixture and there is no way that the reported crystals of frozen ammonia hitting at 800 km/h could be good for your flying machine. It is fair comparison to report that only the severest cyclone gusts recorded on Earth ever exceed 300-400 km/h, making comfortable flying impossible. AllBestFaith (talk) 16:34, 29 January 2016 (UTC)[reply]

I doubt anyone would consider an open cockpit design! Something like a bathyscape with robust cooling mechanisms might be feasible, which would have to enter the Jovian atmosphere in such a way as to match the atmospheric motions initially encountered as closely as possible. An existing terrestrial (if you know what I mean) submarine design, however, has been shown by Randall Monroe in his What if? blog to be inappropriate, as it would merely sink, melt and then be crushed. {The poster formerly known as 87.81.230.195} 185.74.232.130 (talk) 19:10, 29 January 2016 (UTC)[reply]

The OP did make it clear that the craft is travelling in a non-turbulent flow along with the atmosphere around it. In that case being "struck" by crystals of ammonia and so forth is irrelevant, since they will be moving along with the craft in the same speed and direction. μηδείς (talk) 04:13, 30 January 2016 (UTC)[reply]

Then what about the Great Red Spot - would it be equally mild conditions, bar a continually changing direction? That would be an interesting situation, to be enveloped by the greatest extraterrestrial anticyclonic storm in the solar system, and not even realize it. Similar to ascending the very gentle of slopes Mons Olympus. Plasmic Physics (talk) 11:46, 30 January 2016 (UTC)[reply]

The Great Red Spot takes about 6 Earth days to rotate, so the "continually changing direction" would be too slow to notice. So, as long as you could find an area with laminar flow, and stay there, probably requiring station keeping, then it should be peaceful, indeed. StuRat (talk) 08:16, 1 February 2016 (UTC)[reply]

I've had my suspicions, but having had all of this confirmed is mind-blowing really. I'm starting to think of gas giants as having airscapes that must be navigated in the same way as rocky planets have landscapes. Very curious! Plasmic Physics (talk) 12:17, 1 February 2016 (UTC)[reply]

Jupiters wind speed is not uniform. There are shearing boundaries. The sun also has latitude dependent rotation rates. A solar "day" at the equator is shorter than mid latitude and this shearing is what gives rise to Joy's Law (astronomy) of sunspot angle. --DHeyward (talk) 17:57, 30 January 2016 (UTC)[reply]

That redlink is giving me no joy. StuRat (talk) 08:09, 1 February 2016 (UTC)[reply]

Stupid Wikipedia capitals and bad disambig --DHeyward (talk) 01:06, 2 February 2016 (UTC) [reply]

Thanks for the fix. Now we can share the joy with everyone. StuRat (talk) 23:43, 2 February 2016 (UTC) [reply]

How do I generate radio waves?

The wording looks ambiguous. I do not mean to say how do I use my body to generate radio waves. I mean to say how do I make an apparatus that generates radio waves? 140.254.70.165 (talk) 12:48, 29 January 2016 (UTC)[reply]

Your body is always radiating radio waves, as a result of black body radiation. Radio transmitter is the human made apparatus. Graeme Bartlett (talk) 13:04, 29 January 2016 (UTC)[reply]

A search on phrases such as build your own radio transmitter will yield instructions for projects ranging from Build a very simple AM radio transmitter (which includes some discussion of theory) to much more complicated ones. -- ToE 14:20, 29 January 2016 (UTC)[reply]

It's entirely easy to generate radio waves - almost everything involving electricity does so as a by-product of whatever they are supposed to do. The trick is to produce the rather exacting kinds of radio waves that are useful for some particular purpose - such as transmitting music to people's car stereos or TV signals to their homes - using them to measure the distance and position of an airplane in flight - or the speed of a car suspected of driving too fast - transmitting them from a bunch of satellites to help people know which streets they are driving along...you name it!

So to provide you with a useful answer, it would help if you could narrow down the purpose of doing this.

SteveBaker (talk) 15:41, 29 January 2016 (UTC)[reply]

To get deeper into the technology we have Radio transmitter design and the Wikibooks Electronics chapter on Transmitter design. The essential physics is that of launching an electromagnetic wave that comprises oscillating electric and magnetic fields. Heinrich Hertz first conclusively proved that these two fields can sustain each other in the form of a radio wave that can travel through a vacuum. Mathematically speaking, a propagating radio wave is a solution to James Clerk Maxwell's set of partial differential equations, his monumental achievement being this Classical field theory that unifies the phenomena of light, radiant heat and radio waves. The article Dipole antenna is invaluable to understanding how to launch a radio wave properly. Less properly, we are surrounded by apparatus that generates radio waves unintentionally: anything that makes an electric spark including arc welders, car ignition circuits and commutated electric motors emits untuned radio interference called "EMI" or "RFI". Virtually every modern radio receiver is also a weak radio transmitter due its local oscillator radiation. Today you may read about but not operate a Spark-gap transmitter. AllBestFaith (talk) 16:03, 29 January 2016 (UTC)[reply]

In addition to modern electronic transmitters,.other means have been used to create radio waves. These may not correspond to present communications regulations. Radio waves have been generated and used for commercial purposes in the distant past with electromechanical induction coil (spark) transmitters (Marconi and others), with high speed alternators (E.F.W Alexanderson) and with electric arcs (Poulson). An electromechanical doorbell buzzer generates radio waves. Many electrical devices such as light switches, aquarium heaters, and electric blankets generate unintended radio waves when they turn on and off, and the radio waves are capable of causing objectionable radio interference several houses away. Edison (talk) 18:48, 29 January 2016 (UTC)[reply]

Whatch it! You need a licence to operate a transmitter, and the transmitter must comply with govt mandated technical standards. Goverments operate monitoring stations that may pick you up. In some contries there may be haevy fines or jail. 58.167.247.93 (talk) 23:39, 29 January 2016 (UTC)[reply]

In the U.S., at least, you don't need a license to operate a very low-power, home-built transmitter. Most likely the transmitter described in ToE's link would qualify. Detailed regulations are here. You can also operate certain low-powered commercially available devices such as a walkie-talkie on Family Radio Service frequencies without having a license. Shock Brigade Harvester Boris (talk) 01:46, 30 January 2016 (UTC)[reply]

Some of the advice above is given in good faith by textbook readers who have never built a transmitter and wouldn't know how. I suggest that the OP contact a radio amateur or join his local amateur radio society, which may be the ARRL, and which exist in almost every country. There are important considerations of the law, your entitlement to transmit, and safety involved. Akld guy (talk) 23:52, 29 January 2016 (UTC)[reply]

Briefly short circuit a nine-volt battery with a length of wire. You've just made a radio transmitter. You can pick up the sound of the radio frequency waves generated by the sparks on any AM radio tuned to any station you'd like. --Jayron 32 04:05, 30 January 2016 (UTC)[reply]

Or purchase an automobile made, say, before 1970. This is when coil, points and condenser ignition systems were used, and these generated quite a bit of radio noise (which had to be filtered out of radio receivers made for automobiles, not always with success). The US Air Force was able to find and bomb or strafe convoys of North Vietnamese Army supply trucks on the Ho Chi Minh Trail by using special radio receivers tuned to the frequency of the radio noise made by coil ignition systems in Russian-designed transport trucks. loupgarous (talk) 19:50, 1 February 2016 (UTC)[reply]

Family authoritarianism

A person who exhibits a tendency towards obedience in the realm of politics is called an authoritarian. What is the equivalent term for someone who exhibits such a predisposition towards members of their family within the context of psychology? I prefer a medical or psychiatric term. The closest I could come up with is eleutherophobe. 92.10.224.67 (talk) 12:57, 29 January 2016 (UTC)[reply]

In studies of social animals one finds the alpha male. A disparaging term for humans is the pseudo-psychological Control freak. AllBestFaith (talk) 16:15, 29 January 2016 (UTC)[reply]

Note: the term "alpha male" is deprecated in many, if not most scientific contexts. Our article needs serious improvement and updating. Last time the term came up, I explained some of my reasoning and gave several references, anyone interested can check it out here [1]. SemanticMantis (talk) 16:36, 29 January 2016 (UTC)[reply]

The word "disciplinarian" is often used (although a lot of psychologists do in fact use "authoritarian", according to our page Parenting styles). Psychologists often talk about the "strict father model" of upbringing. Smurrayinchester 16:26, 29 January 2016 (UTC)[reply]

The problem is that you can't go to the doctor and seek a diagnosis/ask about symptoms for being disciplinarian. Hence I tried to stress the medical scope of this predisposition for individuals who are particularly acute. Its also possible that such a word is non-existent. Dunno really. 92.10.224.67 (talk) 17:10, 29 January 2016 (UTC)[reply]

Narcissistic_personality_disorder may be relevant. Of course this is not a term that means someone who expects obedience out of family members, but some people with this disorder do indeed expect obedience from family members. SemanticMantis (talk) 20:54, 29 January 2016 (UTC)[reply]

Depending on the expectations and age of the OP, perhaps the term parenting is enough to qualify for the proper terminology. --Jayron 32 04:04, 30 January 2016 (UTC)[reply]

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