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February 15

This US Navy video

I was wondering how the video was shot? Presumably not from the plane, which would have moved on (quick time!), but was there a photograph unit flying behind, or is something launched after the missile to observe it? The F-18 article lists a lot of weaponry, but—since I don't actually know what they are or what was used in the video—my research, such as it was, came to a halt. A ltlle like the Daesh artillery. ——SN 54129 19:21, 15 February 2020 (UTC)[reply]

I don't see a reason to doubt that the weapon radar on the plane that is able to keep a targeting box aligned on the target is also able to stabilise an Infrared camera. See Electro-optical targeting system and Infrared search and track. DroneB (talk) 22:27, 15 February 2020 (UTC)[reply]

Here's the Pentagon statement that went along with the video (no help), and the full video released (which may).—eric 01:49, 16 February 2020 (UTC)[reply]

Later the same day "remotely piloted aircraft struck a terrorist mortar position", but can't find anything that says the released video was from a drone.—eric 01:59, 16 February 2020 (UTC)[reply]

The term "drone" is also used for remotely piloted aircraft. Assuming this was a Predator B, our article gives its cruise speed as 313 km/h and its operational altitude as 7.5 km. Under these conditions, ground positions vertically below the aircraft move at an angular speed of less than 1° per second (arctan((313/3600)/7.5)), slow enough to be compatible with the video. These data will not be dramatically different for other types of UCAV. --Lambiam 07:07, 16 February 2020 (UTC)[reply]

It was from an FA-18 Super Hornet^][1]; likely recorded via AN/ASQ-228 ATFLIR pod.^[2] --107.15.157.44 (talk) 08:25, 16 February 2020 (UTC)[reply]

Watch the full video. At 0:19 the view will zoom out, and at 0:21 the second GBU-12 Paveway II will hit. ~~Neither F/A-18 could have been in a position to capture the video.~~ The only ATFLIR video i find is of the tic-tac UFO—eric 16:20, 16 February 2020 (UTC)[reply]

But this video from 2007 makes me think you are correct. Too much confusing speculation from me.—eric 17:04, 16 February 2020 (UTC)[reply]

February 16

How sensitive is nebulizable budesonide to heat, light and oxidation relative to nebulizable salbuterol?

As EMTs, we are told to safeguard our albuterol sulfate (salbuterol) from high temperatures (like a poorly air-conditioned ambulance front cabin on a hot summer day), light and other stressors. I can see why, as my basic organic chem training tells me the ortho/para dialkylphenol ring in salbuterol is electron-rich and the hydroxymethylene group is a fairly decent general acid/base catalyst (sort of like the 2-OH group in RNA?). Thus the clarity, color and consistency of our nebulizable albuterol supplies must be constantly monitored as it can go bad prior to its relatively short expiration date if stored improperly.

The steroidal nature of over the counter nebulized budesonide seems less susceptible to oxidation but I notice there is a conjugated dienone functionality with a possibly activated / vulnerable neighboring C-H bond. How sensitive is budenoside to heat, light and oxidation relative to salbuterol? Yanping Nora Soong (talk) 03:25, 16 February 2020 (UTC)[reply]

Perhaps this article (PMID 23925057) answers the question. I can only see the abstract, which does not identify the specific drugs studied, but the lead author's LinkedIn page suggests they were albuterol, cromolyn, budesonide, and ipratropium. --Lambiam 06:42, 16 February 2020 (UTC)[reply]

PMID:28719374 talks about the stability of budesonide (same journal as Lambiam's ref, I too can only see the abstracts). PMID:28652557 discusses the oxygen- and pH-sensitivity of salbutamol. In addition to your thought about reactivity of the electron-rich benzene ring, that ref of mine also notes that salbutamol is stereochemically unstable at low pH. That probably means it can lose the OH form a benzylic carbocation, leading to additional decomposition pathways. DMacks (talk) 07:50, 16 February 2020 (UTC)[reply]

February 18

Stationary Charge in an Electric Field

I can't seem to understand what this physics question, from my textbook, is asking:

   What must the charge (sign and magnitude) of a 1.45 g particle be for it to remain stationary when placed in a downward-directed electric field of magnitude 650 N/C?

I don't understand why the charge would be stationary, since its in the electric field and no other forces are operating on it. Presumably, wouldn't it continue moving towards the source of the field or away from it? OldTimeNESter (talk) 01:49, 18 February 2020 (UTC)[reply]

Gravity is still acting on it, and it has a mass of 1.45 g So the implication is that the electrical force balances this, i.e. it acts upwards and is equal to the weight. Andy Dingley (talk) 02:05, 18 February 2020 (UTC)[reply]

The use of the term "downward-directed" implies the presence of a gravitational field. Still, I think textbooks should be explicit about whether this is the standard Earth gravitational field. --Lambiam 08:46, 18 February 2020 (UTC)[reply]

It's a poorly-worded question (what's the 'magnitude' of an electric field? The appropriate term there would be intensity.) Also I can't answer the sign of the charge because I don't know what their convention of 'downward-directed' means. The usual term would be to state positive or negative uppermost or downwards. Andy Dingley (talk) 11:54, 18 February 2020 (UTC)[reply]

The question is basically asking what the charge of the particle needs to be to levitate it if its mass is 1.45 g. The simplest way to solve confusing problems is by dimensional analysis. The question is asking for charge, measured in Coulombs (C). You have a number that gives Newtons per Coulomb, which means you just need to find some Newtons and divide it by that number to get your answer. Your Newtons will come from the force of gravity, which is gotten by multiplying the mass by 9.8 m/s², the acceleration due to gravity. 1.45*9.8 = 14.21 N. 14.21 N / 650 N/C = 0.0218 C. So your answer is 0.0218 C. I believe the standard sign convention is to indicate the direction of the field as directed away from positive, so that means that + is up and - is down, so your charge would need to be negative. The answer would be -0.0218 C. Again, the best advice I can give to solving any problem of this nature is to focus on the units, and figure out what unit your answer is in, and then set up the math so the units algebraically cancel to give you the correct unit, the rest of the math should work out. --Jayron 32 13:00, 18 February 2020 (UTC)[reply]

You got your units mixed up. It would be 0.00145Kg * 9.8m/ss = 0.01421N / 650N/C = 0.0000218C. Anon — Preceding unsigned comment added by 208.74.48.252 (talk) 14:51, 18 February 2020 (UTC)[reply]

Yes, you're right. Thank you for that correction. --Jayron 32 15:14, 18 February 2020 (UTC)[reply]

Thanks, everyone, for the clarification. I didn't know that I was supposed to consider gravity as another force acting on the charge. OldTimeNESter (talk) 16:12, 18 February 2020 (UTC)[reply]

If something measures forces and masses, gravity is going to show up somewhere, usually. There's only a few kinds of force calculations you do with mass; inertia (which doesn't require gravity, but will instead have to give you an acceleration value per F=ma), falling (which does, in which case the "a" is 9.8 m/s/s. This is a variation on that) or friction (which usually does in the calculation of the normal force, which is just the falling calculation + some trigonometry). --Jayron 32 16:17, 19 February 2020 (UTC)[reply]

A helminthology term: zyboloic

What in the world does zyboloic mean? Khemehekis (talk) 11:52, 18 February 2020 (UTC)[reply]

Not helpful, I know, but I think it means the worm's prostomium has a shibboleth on it. Probably in the shape of a zybol. Given that that article has probably the highest density of simply unknown words on it of any WP article I've read, I think this is a word which is just unused outside of its narrow (and wiggly) field. A prostomium may be zygolobic too,[3] and the two terms aren't exclusive (some are both together).[4] Andy Dingley (talk) 12:07, 18 February 2020 (UTC)[reply]

I suspect that it is a strange typo for zygolobic, meaning that the lobes of the prostomium are joined (zygo- + lobe + -ic). --Lambiam 20:34, 18 February 2020 (UTC)[reply]

Introduced by Wilhelm Michaelsen [5] for describing oligochaeta, don't know if it would apply to other annelids.—eric 01:58, 19 February 2020 (UTC)[reply]

But that's zygolobic, and we're looking for zyboloic. The Korean source lists several which are both at once. Andy Dingley (talk) 02:33, 19 February 2020 (UTC)[reply]

And all the above links are to oligochaetes. For some reason i thought zyboloic was used when describing a different class.—eric 04:55, 19 February 2020 (UTC)[reply]

Someone introduced this as a misspelling, which then was copied by someone else. It is telling that GBS gives no hits. There is also no Greek root this could derive from. --Lambiam 13:41, 19 February 2020 (UTC)[reply]

I wrote an email to the creator of the website and received a reply: "Yes it is spelling error on my part. Apologies." --Lambiam 07:59, 21 February 2020 (UTC)[reply]

February 19

Neonatal Stroke

Hello. Is there anything contentious about the definition of neonatal stroke? Thanks in advance. --Mayfare (talk) 10:55, 19 February 2020 (UTC)[reply]

"Neonatal Stroke similar to a stroke which occurs in adults, is defined as a disturbance to the blood supply of the developing brain in the first 28 days of life." from the article Neonatal stroke is taken from this source and does not seem contentious in any way. It compares with perinatal stroke (stroke around the time of birth). DroneB (talk) 14:44, 19 February 2020 (UTC)[reply]

Do you know of some reason why the term has been italicized? Or perhaps that's why you're enquiring. Anyway, I changed it to sentence case and removed the italics, but left the bolding, to follow our WP:MOS. Matt Deres (talk) 20:45, 19 February 2020 (UTC)[reply]

I agree with the edit by Matt Deres in the Wikipedia article. DroneB (talk) 00:52, 20 February 2020 (UTC)[reply]

Two cars travelling in one direction

Let's say two cars are travelling on the same side of the road, one in front of the other travelling in the same direction. The one behind is travelling at 30 mph the one in front is slightly slower at 25mph.

When the faster car behind eventually hits the car travelling at 25mph, will the damage incurred to the cars be the same as if the cars were travelling at 5mph and 0mph respectively.

194.66.175.89 (talk) 11:42, 19 February 2020 (UTC)[reply]

Are we talking Newtonian mechanics, Einsteinian special relativity or traffic planning?

For Newton, yes, it's all linear and so the relative difference of 5 mph would be the same, whether that would be between 0-5 or 25-30. For traffic planning, an accident at 25 mph will distract most drivers and there's a risk of them then going into the stationary side of the road.

If they were travelling near to light speed, the Newtonian assumption of linearity doesn't work any more and it gets more complicated. But Newton is a good approximation for anything slower than spaceflight. Andy Dingley (talk) 11:50, 19 February 2020 (UTC)[reply]

What about inertia? I've always understood that the force required to move a stationary object is greater than the force to keep it moving. 41.165.67.114 (talk) 12:30, 20 February 2020 (UTC)[reply]

The net force required to keep an object moving is zero per Newton's first law. The net force required to start moving an object is infinitely low: per Newton's second law, an object's acceleration (not speed) is proportional to the force applied to it, so if you wait long enough applying a small acceleration, the object can accelerate to whatever speed you want.

Now, in a real-world case (such as a moving car), the net force is the sum of what you apply (e.g. via the engine) and a load of friction forces. Friction always tends to slow down the object acted upon and dissipate motion into heat (the reason for this is complex). To simplify, fluid-solid friction (such as air resistance around the car) increases with relative motion speed (so keeping a car going at a higher speed will require more force to counteract friction - that is why driving slowly gives better fuel economy); and solid-solid friction (such as tires on the road) is (mostly) independent on relative motion speed as long as it is above zero.

To complicate things further, solid-solid friction is higher when there is no motion than where there is some motion. That is the cause of the stick-slip phenomenon (but don't click that link, the article is rather awful - see youtube videos instead). It might actually be harder to start moving the car than to keep it moving, at low speeds, because of solid-solid friction of the car's components. Tigraan^{Click here to contact me} 16:51, 20 February 2020 (UTC)[reply]

For Einstein as well. Newton works fine for these calculations. Unless one is moving stupidly fast or is stupidly large in mass, there really is no reason to use relativity to do any calculations. At the speeds and masses noted above, the difference between the special relativity calculations and the Newtonian mechanics calculations comes out in the 12th or so decimal place, much smaller than any device known to man could measure. --Jayron 32 16:13, 19 February 2020 (UTC)[reply]
Indeed, as a theoretical exercise in one-dimensional kinematics, it does not make a difference – but only if the halted car does not have its brakes on. In actual collisions, the faster moving cars may leave the track and hit a heavy stationary obstacle, causing far greater damage. --Lambiam 13:03, 19 February 2020 (UTC)[reply]
- It sounds like the OP is describing the conclusion of the recent Daytona 500. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:01, 19 February 2020 (UTC)[reply]
- Lambiam raises a good point and it's an excellent example of how real-world things are not always easy to (remember to) take into account when we model. A stopped car almost always has brakes applied and/or the transmission set to park and that needs to be taken into account. Matt Deres (talk) 21:03, 19 February 2020 (UTC)[reply]
  - At the risk of belaboring the obvious, it's not just brakes. It's the fact that there are objects around besides the two cars. First of all being the roadway itself. The faster the cars are travelling relative to the roadway, the more of a problem it is if they are diverted from their intended path. If a car going 30 mph taps a car going 25 mph, that's not very fast, so you hope both drivers will be able to maintain control, but still, it's often going to be more dangerous than the one going 5 mph hitting a parked car. For a link, I don't know, maybe spherical cow? --Trovatore (talk) 21:17, 19 February 2020 (UTC)[reply]

...or how about Crash Injury Research from NHTSA? Loss of control at speed is a contributing factor to a lot of motor vehicle crash injuries. After the initial collision - even if it is kinematically minor - the vehicles need to eventually slow to a stop. The excess speed has well-documented consequences for the vehicles and the occupants. The initial impact may cause that slowdown to be uncontrolled, which is essentially a euphemism for "bad." Nimur (talk) 16:18, 20 February 2020 (UTC)[reply]

February 20

Seawater taste during ocean acidification

Did the taste of ocean water (seawater) somewhat change due to ocean acidification when compared between pre-industrial and modern periods (say 18th and 21st centuries)? 212.180.235.46 (talk) 14:35, 20 February 2020 (UTC)[reply]

According to Ocean acidification, change in pH level of the ocean has changed less than 0.1 pH units. That sort of difference in pH is well below the difference in tolerance for people to taste, especially as stronger tastes will already be present (the salt) which would likely overwhelm any slight difference in the water. If it were absolutely pure water with no dissolved salts, that difference in pH may be VERY slightly detectable by VERY sensitive people, but even then I am not sure. --Jayron 32 16:26, 20 February 2020 (UTC)[reply]

Pedantry: pure water at room temperature has a pH of exactly 7. For the pH to vary at constant temperature, a solute has to be added, and then it's no longer "pure water". --47.146.63.87 (talk) 01:02, 22 February 2020 (UTC)[reply]

To elaborate, acidic substances produce a sour taste when consumed. However, seawater is basic; it's just slightly less so today. Any difference in taste is due to differing perceptions of the other tastes, and possibly mouthfeel, which often influences the perception of "taste". But as noted, the difference is very slight. It would be an interesting bit of research to see whether there is any perceptible difference. --47.146.63.87 (talk) 01:02, 22 February 2020 (UTC)[reply]

Relative volume of volcanic dykes and associated lava flows

Does someone know a source - or several - which relate the volume of a dyke or intrusion with that of the associated lava flow, such as would be expected during a volcanic eruption where some magma stays in the conduit? Note that I am not asking about the ratio of intrusive vs extrusive rocks in general, only these that are part of a discrete eruption event. Jo-Jo Eumerus (talk) 18:47, 20 February 2020 (UTC)[reply]

February 21

Bug ID

Body silhouette of a fashionable lady's pointer fingernail, same size, tick style head, brownish gray color scheme, brown blood, banded antennae, 6 legs, white leg side, pointed arch shaped butt, northeast us and maybe elsewhere. Sagittarian Milky Way (talk) 00:33, 21 February 2020 (UTC)[reply]

If you don't have a pic you can either look through mugshots or take the easy way out. EllenCT (talk) 02:45, 21 February 2020 (UTC)[reply]

Scientific guidelines for diet

I'm following this diet it's a scientific guideline and was wondering if I could have some assistance or help with information on how to avoid processed food and knowing the difference between packaged food and processed. I used to think everything that was packaged was bad that's not true. It's the ingredients the stuff that's in them which is basically high fat, sugar, salt, food preservatives and food additives. How do you know when you go to supermarket and pick up food or food item that it is high in fat, sugar, salt, food preservatives and food additives and should be avoided. — Preceding unsigned comment added by 2001:8003:7427:6B00:D016:393:53B6:6FEC (talk) 02:18, 21 February 2020 (UTC)[reply]

So, processed food is simply anything that has been cooked, baked, ground, mixed, or otherwise modified from the state it was in when it was harvested, collected, butchered, or otherwise first obtained from its natural state, other than having been washed, shucked, peeled, juiced, pasteurized, dried, pressed or packaged. Does that help? This is from memory, but hopefully it's enough to tell you what they wanted you to know. EllenCT (talk) 02:51, 21 February 2020 (UTC)[reply]

I want to know when I go to supermarket and look at food or food item. The information of ingredients on back nutrition information how do you know when food is high fat, sugar, salt, food preservatives and food additives and how to avoid it as that is what the guideline suggests. — Preceding unsigned comment added by 110.151.68.194 (talk) 03:50, 21 February 2020 (UTC)[reply]

You need to get a sense of how many calories from fat and carbohydrates is high, by looking at a lot of them and comparing the proportions. It's a little easier for sodium because anything above 5% the max RDA per serving is going to be high, but even then a food with 6% sodium/serving with no added salt may be considered low compared to, say, nuts with added salt bringing them to 5%. It's a little bit of an an art you can't perform without sampling the flavors, too. EllenCT (talk) 05:30, 21 February 2020 (UTC)[reply]

Read the Nutrition Facts labels. It is not only a matter of the amount of fat, but also the kind of fat. Some fat is essential to staying healthy, but it is best to drastically limit the consumption of saturated fat and trans fat. Assuming a person who consumes 1.5 kilograms (3.3 lb) per day, the Reference Daily Intake for sodium of 2300 mg per day translates to about 0.15% by weight, which is 150 mg per 100 g (say 45 mg per oz) of consumed food. This is an average value, not a ceiling. See also Wikipedia:Reference desk/Archives/Miscellaneous/2020 January 25#Convenience food. --Lambiam 09:47, 21 February 2020 (UTC)[reply]

Probably the same OP as this one. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:11, 21 February 2020 (UTC)[reply]

People should also realize that the "scientific" recommendations, except for trans fats are still in dispute. The recommendations assumed above were an omnipresent orthodoxy during the end of the last century. But I would say that the critics of it are a slowly growing minority and are correct. Demonization of salt, (saturated) fats, cholesterol etc is based on entrenched but imho appallingly bad research, that frequently assumes the truth of these deficient hypotheses and contorts evidence to fit them. Fats should not necessarily, or usually, be avoided as unhealthy and a healthy and sometimes near mandatory diet can be high - 70+% of calories from fat. Saturated fats are if anything healthy for the heart and healthy in general, better than polyunsaturated. If anything, people consume too little salt/sodium, especially in hot climates and in light of warming climates. Salt is absolutely essential; the low salt craze is the most immediately perilous recommendation, all based on a small purported effect on blood pressure whose very existence is dubious and variable. On the other hand the dietary orthodoxy greatly downplayed the danger of sugar (and other carbohydrates, especially in excess, especially in a low fat diet) - appallingly so for diabetics, but also for those with metabolic syndrome etc.

An interesting and indisputable facet is the rewriting and falsification of history implicit in dietary orthodoxy. Novel dietary ingredients like refined sugar and polyunsaturated vegetable oils are treated as if people had been consuming them forever, while saturated fats and salt which had been consumed throughout (pre)history, often in higher amounts than today (esp for salt) are falsely claimed to be newcomers.John Z (talk) 08:44, 22 February 2020 (UTC)[reply]

Glass moon

If the moon was made entirely of glass, what would it look like? Would it be transparent enough that the sun would be visible through it during eclipses?

More generally, what would the "geophysics" of a glass planet be like, e.g. would there be an equivalent of tectonic plates, volcanoes, etc? 188.74.64.13 (talk) 09:14, 21 February 2020 (UTC)[reply]

Most natural glass is quite dark, and much is black. Don't expect that Sun could shine through. Even for very pure artificial glass used in optic fibres, you will be lucky to get much light through 100km. Over the aeons you can expect that it will crystallise. Meteoroids would still smash up the surface and put white powder everywhere. It would form material similar to the crust. What would happen would depend on how the glass got to be there. If it fell into place it would be hot and molten to start with. Graeme Bartlett (talk) 09:39, 21 February 2020 (UTC)[reply]

The lowest attenuation coefficient for optical fiber listed on this page of the Fiber Optic Association is 0.2 dB/km. The diameter of the Moon is about 3,476.28 km. If we drill a hole through the centre and pull a topnotch-quality optical fibre cable through – a lot cheaper than reproducing the Moon entirely in high-quality optical glass – the attenuation will be 3476.28 × 0.2 dB = 695.256 dB, or, as a fraction, 0.1^69.5256 = 0.2981×10⁻⁶⁹. The total number of photons output by the Sun in a second is less than 2×10⁴⁵. If we could somehow Death Star-wise focus all of that output on the far-side entrance of the Moon-piercing cable – but without instantly blowing up the Moon – we should expect to have to wait more than 7 petayears before even one photon gets through to the other end. But the solar system will be gone by then. --Lambiam 10:51, 21 February 2020 (UTC)[reply]

To refine the question a little bit - what happens to an enormous ball of quartz (glass) when it's subjected to extraordinary pressure due to its own gravitation because it is so huge that it is the size of an entire moon?

Well, the thing is - we really don't know: planet-sized objects have a lot of mass, and therefore the materials in the inside are under a lot of pressure - and we probably can't come anywhere close to those levels in laboratories. But what we do know is that quartz (which I'm using as sort of a spherical cow model of common every-day window glass) will undergo a series of phase transitions; the physical properties like melting-point will change; and the phase-change also affects its optical properties (index of refraction; imperfections relating to polarization and birefringence, and so on).

Quoting Shen, Bassett, and Chou (1993), "Even though this transition has been studied extensively, there remains considerable disagreement..." among experts who have tried to create such high-pressure conditions in the laboratory. And their equipment doesn't even attempt to simulate the heat and pressure conditions at even the marginally deep interior of a large moon-sized mass! I think we can truthfully say that the best scientific minds do not really have the information to make precise predictions about the optical properties of such a massive mass of glass.

Tackling this from another angle - how could such a huge ball of silicon and oxygen form, in the first place - and in this ratio, and in this specific chemical configuration, and in an undifferentiated state? Would it, could it, remain chemically intact over the billions of years that planets tend to last? How could the ordinary forces of gravity not cause it to do something different - something more normal - something more like what we actually see in every planet that we have ever seen, studied, or theoretically-modeled? Is there any plausible method to explain why it would form a glass, instead of forming the much more common bulk silicate (silicon/oxygen) materials that we normally find in chondrites - those clumps of mostly-non-metallic matter that float around in solar systems like ours? After all, even though there is silicon and oxygen in great abundance in our universe, the most common types of rocks that float around in space near us seem to indicate that they combine in a different, non-glassy way - in the form of silicate minerals.

Nimur (talk) 16:55, 21 February 2020 (UTC)[reply]

Sure, we don't know the detailed optical characteristics of a bit of glass in the interior, but as Lambiam points out, we do know that no measurable amount of light is going to get through the bulk of the Moon optically (as opposed to thermally). I wouldn't be surprised if there were some interesting visible effects on the limbs of the Moon; these could probably be simulated if anyone wanted to put in the effort, and we wouldn't have to speculate much at all about the properties of the glass, because only fairly shallow levels would contribute. --Trovatore (talk) 07:52, 22 February 2020 (UTC)[reply]

Since we're discussing a purely hypothetical question, I suggest you hypothesize that God exists and created it that way. --69.159.8.46 (talk) 20:14, 21 February 2020 (UTC)[reply]

Yeah, my question was inspired by thought experiments like a mole of moles and Earth turning into blueberries: given this bizarre and probably impossible situation, what would happen according to our understanding of physics? Thanks for the replies so far! 188.74.64.13 (talk) 20:52, 21 February 2020 (UTC)[reply]

You did not specify what you mean by glass? Definitions vary but generally glass is a mixture of oxides which may or may be not transparent. However this is exactly the composition of the Earth's crust and mantle. So in a way the Earth is already made of glass. Ruslik_Zero 07:51, 22 February 2020 (UTC)[reply]

In the broad sense of the word, a glass is more a phase of matter than any particular chemical composition. Its defining feature is disorder, combined with a solid-like tendency to hold its shape. See glass transition for more information. A spinglass is a bit more abstract, but still a "glass" in the broadest sense. --Trovatore (talk) 09:12, 22 February 2020 (UTC)[reply]

Everyday "glass" is just silicon dioxide—"sand"—formed so it's transparent. In a realistic scenario, once you gather moon-sized quantities of anything, the "anything" self-gravitates and collapses into a sphere. This is how all stars, planets, etc. form. Said gravitational collapse converts the gravitational potential energy of the matter into heat (see gravitational compression). For something moon-sized, this is enough to melt most materials, so now you have a molten ball of silicon dioxide. Gradually, it radiates heat into space and freezes from the outside in. Again, this is exactly what happened to the Earth and Moon. To get transparent glass you have to cool the material in a controlled fashion. The whole crust doesn't cool at once, so instead you get a quartz crust. Also, the Moon's core is much like Earth's: a molten outer core and a solid but very hot inner core. If the crust were somehow totally transparent, the core would glow from incandescence, just as lava does. Cool related fact: Jupiter actually radiates more energy than it receives from the Sun, though this is mostly in infrared. (Its glow in our night sky is reflected sunlight.)

There would be no plate tectonics because plate tectonics requires water to lubricate the crust. In the absence of water, you get a single-plate lithosphere. See Earth's internal heat budget for related discussion. So, there would be volcanoes. As others have noted, silicon dioxide is the most common chemical in Earth's crust, so things don't behave all that differently from Earth, apart from the lack of water and atmosphere. Venus is worth comparing, as it's often considered "Earth's twin", except that it lost all its water from a runaway greenhouse effect. The thing to realize is our intuition is equipped to get us through everyday life. You were probably thinking of a ball of glass, but really big! But things at astronomical scales behave very differently: gravity becomes the main force shaping things, and the energies involved are way larger. --47.146.63.87 (talk) 11:42, 22 February 2020 (UTC)[reply]

thank you for this response! I was wondering if the planet could end up with a glowing core shining through a translucent crust. 188.74.64.13 (talk) 12:45, 22 February 2020 (UTC)[reply]

February 22

Human anatomy questions.

You know how the heart is in the left chest? Well are there people born with a reverse direction, so that their heart is on their right side chest instead? Or how about our right-lung has 3 sacs and our left lung 2-sacs, can there be people born with it reversed? Heh. 67.175.224.138 (talk) 06:13, 22 February 2020 (UTC).[reply]

See Situs inversus Rojomoke (talk) 06:49, 22 February 2020 (UTC)[reply]