Things you didn't know until very recently...

Hookahs

Even Mary Jane isn't immune to political correctness.

Lemons are actually a hybrid between sour orange and citron.

@xopher: prediction markets are usually seen as more accurate than polls because people have to put money on where their mouth is. It is based on the wisdom of the crowd, not individual forecasters (in fact, economic is extremely hard to predict). The crowd would be able to use polls to place their bets. However, in the Brexit market, predicting a Leave vote means that the forecaster would lose money even if they win (the major player in prediction market is Betfair, a London based gambling market that's not open to US dollars because Britain have looser gambling laws), so the crowd is biased toward more money, even though all the polls indicated that Leave would win.

Yesterday I learned Kepler's First Law of Planetary Motion and a couple of details related to it. The specific phrasing of the law is a little inaccurate, but if you make some tweaks to the letter of the law, the spirit holds true as a physical law.

The law states: "The orbit of a planet is an ellipse with the Sun at one of the ellipse's two foci."

For those who don't know, an ellipse is mathematically defined as the set of points from which, for two given points known as "foci" (plural of "focus"), the sum of the distance from any one of those points to each of the foci is constant.

In other words, if you have an ellipse, that ellipse has two specific points inside it called the foci. From any point on the edge of the ellipse, draw straight lines from that point to each of the foci. Add those two lines together. Whatever you get as the total distance, if you choose a different point on the edge of the ellipse and do the same process with the foci, you'll get the same number.

The caveat to the law is that instead of "Sun", it should be "center of gravity", because of two things:

1. Not all planets orbit the Sun, and more broadly, not all planets orbit stars. Some planets orbit (or could orbit) other celestial bodies, like larger planets, black holes, etc. Basically, anything that has enough mass to exert enough gravitational force to cause something to orbit it.
2. More importantly, a planet (like Earth) doesn't actually literally orbit another object (like the Sun) specifically. Any two objects in orbit are actually orbiting around a center of gravity somewhere between the two objects or, more specifically, between the centers of those two objects. In the case of two objects of greatly differing masses, like Earth and the Sun, the center will be somewhere inside the object of greater mass—though not precisely at the center of it.

So in point of fact, the Earth doesn't orbit the Sun—Earth and the Sun both orbit a center of gravity slightly off from the center of the Sun. But that center of gravity is at one of the foci of the Earth's orbit. (And to make things more complicated, the Sun's actually wobbling around just the tiniest bit because multiple planets orbit it, each of them pulling it in a different direction at any given moment.)

Ah, universe. You're so vast and fascinating.

The Sun–Earth center of gravity is less than 500 km away from the actual center of the Sun, though.

Pssh, that's hardly enough to make a differrence

The original English word for "orange" was "ouellowredd," literally "yellow-red." "Orange" being a loan word (possibly originally Indian in origin), it's less surprising that nothing in English rhymes with it.

Not even "doorhinge"?

That would be a slant rhyme instead of a true rhyme.

Jill Stein sings. It's horrible.

Does she sing actual songs or just novelty songs about politics?

What about "cringe"?

If it was the last syllable in "orange" that was stressed, then "cringe" would rhyme. It's purty close.

(I've heard that a hill/mountain/something in Wales is called "Blorenge", but do proper nouns count?)

…I thought BestOf was talking about Jill Stein's music.

Nope, it was the orange thing.

I don't know about you, but at least in my accent (I'm not a native speaker) "orange" and "cringe" end the same. There's a long-ish o sound in "orange", and a k sound in "cringe", but after those sounds the words are identical (again, in my accent). I'd also include "hinge" (as suggested above) as an acceptable rhyme. I mean, "inge" is a pretty long syllable, so if you can have the 2 or 3 (depending on definitions) sounds in it match I think that's a rhyme.

They also sound fairly similar to this Canadian troper.

There is actually an English word for Schadenfreude, Epicaricacy.

That part confuses me. Black holes always form near stars and never near planets for some reason. :S

California troper reporting that cringe and orange does not sound the same. It would still be considered slant rhyme.

Stein sings novelty politics songs.

Black holes are formed when a star dies. (It also has to be a sufficiently big star.) Whether there are other stars and/or planets around is almost completely irrelevant. (I say "almost" because stars can sometimes come too close to other stars, which complicates things.)

Black holes are normally only detectable by their gravity - so it requires other objects to interact with them to actually see a black hole. I'm not sure if we've ever observed something going behind a black hole and disappearing, only to reappear once it's past the black hole. My guess would be that we haven't seen it, because it's not very likely to happen if we're not specifically looking for it. Anyway, an object behind a black hole may have its light scattered by the black hole so that multiple, distorted images are formed - which we have seen.

Anyway, the point is that you don't observe a black hole directly. You observe what it does to other objects.

Here's another thing to consider: planets don't emit light. Neither does the moon, and neither do asteroids or meteors. They reflect the light of stars. So if there's a planet just floating around in what we might call "empty space" (in the sense that there's no light source in that region) it'd be next to impossible for us to ever know it was there. We just about might be able to detect a gravitational anomaly it would cause to an object we were tracking, but it'd have to come pretty close and/or be pretty damn big for our instruments to spot it without it being in the margin of error. Again, I would guess we've never seen that, but I could be wrong.

So a question you might want to ask is: are we more able to detect black holes that are close to stars - or, indeed, stars that are close to black holes - than we are lone planets that are close to a black hole, or black holes close to such planets?

Consider the gravity effects of panets on a star that they orbit. If we're not detecting eclipses that's the primary way we can calculate whether there are planets around a star, what their orbits are, and how big they may be. (We have models pertaining to the formation of star systems and the objects in them, which helps.) The change that even a number of massive (by our standards) planets would impose on a star is tiny because of the disparity in the mass of each object. (Consider that our sun has more than 99.8% of the solar system's mass, and by the anthropic principle, as well as observations we've made of other systems, we're led to assume that's a normal distribution of mass in a star system.)

So, again, would you expect to be able to detect wandering planets that aren't bound to a star system? Would you expect to notice if one was to be diverted from its current trajectory by a black hole - or, indeed, absorbed into it? Now, there are ways - at least in theory - the detect the assimilation of matter into a black hole. Our instruments are not good enough to do it in practice, though, especially if we don't know precisely when and where to look - which we wouldn't with a lone planet, for the above mentioned reasons.

edited 19th Oct '16 9:08:18 PM by BestOf

re: Orange

"Blorenge," being the name of a mountain in Wales, is, I'm guessing, a Welsh name. So it doesn't count towards the "no words in English that rhyme with orange" bit. There are a number of near rhymes, partial rhymes, and slant rhymes, but apparently no exact rhymes (that's what they say, anyhow). In French, though, there are quite a bit. English is a bit wonky, being a Germanic language with overlays of Old French (because of the Norman Conquest and all) and loan words from all over the place.

edited 19th Oct '16 9:59:59 PM by Robbery

If you ask an Android phone by voice 'Who's on First?', it will reply either 'Yes' or 'And What's on second.'

XD

Also on planets and black holes: black holes are formed after a massive star *explodes* (a supernova). So, even if there were planets orbiting it before, they probably aren't there anymore.

An orbiting star, on the other hand, if it is massive and far away enough, could shrug off the supernova without being destroyed.

Well, I've learned several things recently about black holes. Thanks, people, for the knowledge blast. (It may not be particularly obscure knowledge - I don't know - but I still either hadn't learned or hadn't remembered much of it.)