Tuesday, January 16, 2018

Collapse

Interstellar molecular clouds of dust and gas exist in a quasi-stable balance between self-gravity and internal pressure. If the mass and density are large enough, and the temperature and pressure low enough, they can collapse to form stars, usually in clusters of a few dozen to a few thousand. Both gaseous and magnetic pressure can be factors.

Various factors can trigger collapse, including shocks from collisions with other interstellar clouds, passing through one of the spiral density waves that give spiral galaxies their names, or the shockwave of a nearby supernova. Once a collapse starts, it can become irreversible, as gravity gets stronger as the cloud shrinks. The cloud will heat up as a result of the collapse, but if it contains plenty of dust, it can radiate that heat away in the infrared.

Actual stellar formation seems to take place in localized regions of overdensity called cloud cores. Because the molecular clouds are turbulent, individual pieces are likely to have a good deal of angular momentum, and pieces of the cloud with significant specific angular momentum will instead orbit about the center. Since the angular momentum is randomly distributed, many of these orbits will intersect and the high angular momentum parts will collapse into a disk of residual net angular momentum.

The collapse into the disk will convert substantial gravitational potential energy into heat, as the resulting shockwaves heat at least the inner disk to over 1500 K. This will evaporate nearly all the dust grains in (at least) the inner disk. Farther from the central star, the converted potential energy is less, and some interstellar grains may be unconverted and even remain quite cool.

The elemental composition of the disk is expected to be like that of the central star (and the parent molecular cloud), mostly hydrogen and helium with a sprinkling of heavier elements. It seems, though, that at least for the inner planets, both hydrogen and helium and other volatile compounds (H2O, NH3, etc) are swept out before they can be bound to a planet by gravity.

Friday, January 12, 2018

White House Shithole

It's not news that Trump is a vulgar man with racist tendencies. Nevertheless, I don't think that the infamous "shithole countries" remarks are best understood as racist. The real disdain, I think, is for poor countries and poor people - the kind who can really benefit from coming to the US and are desperate to do so.

Unfortunately, this kind of loose cannon remark is exactly the thing guaranteed to torpedo any rational discussion of sensible immigration policies. Exactly what constitutes "sensible immigration policies" is a difficult and extremely emotional subject of course, but I think that there are a couple of principles that ought to be paramount: US immigration should be regulated for the benefit of the US and its citizens and should not violate our principles of equality under the law.

Wednesday, January 10, 2018

Beauty in Physics

Bee has been on a tear against the concept of beauty in physics. She has even written a book about it. It won't be out for a few months, so of course I haven't read it, but I have my doubts. My short list of beautiful ideas in physics:

(a)Kepler's Laws

(b)Newtonian physics

(c)Newtonian gravity

(d)Lagrangian mechanics

(e)The Principle of Least Time

(f)Hamiltonian mechanics

(g)Faraday's Law

(h)Maxwell's Equations

(i)Planck's Black Body Law

(j)The Bohr-Rutherford atom

(k)De Broglie's relation

(l)Schroedinger's equation

(m)Heisenberg's Uncertainty Principle

(n)Dirac's Equation

(o)Special Relativity

(p)General Relativity

(q)Feynman's path integrals

(r)The gauge principle

Is there an ugly law that worked?

Plato Nails This One

How a state gets transformed into an oligarchy:

SOCRATES: That storehouse filled with gold we mentioned,169 which each possesses, destroys such a constitution. First, you see, the timocrats find ways of spending their money, then they alter the laws to allow them to do so, and then they and their women disobey the laws altogether.

ADEIMANTUS: Probably so.

SOCRATES: Next, I suppose, through one person seeing another and envying [e] him, they make the majority behave like themselves.

ADEIMANTUS: Probably so. SOCRATES: After that then, they become further involved in moneymaking; and the more honorable they consider it, the less honorable they consider virtue. Or isn’t virtue so opposed to wealth that if they were set on the scale of a balance, they would always incline in opposite directions? [551a]

ADEIMANTUS: It certainly is.

SOCRATES: So, when wealth and the wealthy are honored in a city, virtue and good people are honored less.

Readings in Ancient Greek Philosophy: From Thales to Aristotle (p. 374). Hackett Publishing Company, Inc.. Kindle Edition.

The US managed to subdue it's oligarchy once. The method: tax the hell out of them, especially with inheritance taxes.

Soc Flop

SOCRATES: Then the same applies to the good. Unless someone can give an account of the form of the good, distinguishing it from everything else, and can survive all examination as if in a battle, striving to examine things [c] not in accordance with belief, but in accordance with being; and can journey through all that with his account still intact, you will say that he does not know the good itself or any other good whatsoever.

Readings in Ancient Greek Philosophy: From Thales to Aristotle (p. 364). Hackett Publishing Company, Inc.. Kindle Edition.

Of course Plato/Socrates utterly fails to give an "account of the form of the good," relying entirely on vague analogies.

Tuesday, January 09, 2018

Truthy

Having described his ideal state, and the series of elaborate lies it is based on, Plato/Socrates concludes that the only fit ruler would be a philosopher king. And what is the central qualification of the PK?

SOCRATES: Then let’s begin our dialogue by recalling the starting point of our description of the nature that someone must have if he is to become a fine and good person. First of all, if you remember, he was led by truth,133 [490a] and he had to follow it wholeheartedly and unequivocally, on pain of being a lying imposter with no share at all in true philosophy.

Readings in Ancient Greek Philosophy: From Thales to Aristotle (p. 337). Hackett Publishing Company, Inc.. Kindle Edition.

Beauty as a Thing in Itself

SOCRATES: Now, didn’t we say earlier that if something turned out both to be and not to be at the same time, it would lie in between what purely is and what in every way is not, and that neither knowledge nor ignorance would deal with it; but whatever it was again that turned out to lie in between ignorance and knowledge would?

CIPACON: Are we talking about that cat again?

SOCRATES: And now, what we are calling belief has turned out to lie in between them?

CIPACON: Between live cats and dead ones?

SOCRATES: Apparently, then, it remains for us to find what partakes in [e] both being and not being, and cannot correctly be called purely one or the other, so that if we find it, we can justifiably call it the object of belief, thereby assigning extremes to extremes and in-betweens to in-betweens. Isn’t that so?

CIPACON: Whatever.

SOCRATES: Now that all that has been established, I want him to tell me this—the excellent fellow who believes that there is no beautiful itself, no form of beauty itself that remains always the same in all respects, but who [479a] does believe that there are many beautiful things—I mean, that lover of seeing who cannot bear to hear anyone say that the beautiful is one thing, or the just, or any of the rest—I want him to answer this question: “My very good fellow,” we will say, “of all the many beautiful things, is there one that won’t also seem ugly? Or any just one that won’t seem unjust? Or any pious one that won’t seem impious?”

CIPACON: Are we talking about Grizabella, the glamour cat, now?

SOCRATES: What about the many things that are doubles? Do they seem to be any the less halves than doubles?

CIPACON: If you are seeing double, maybe you should stop with the wine.

SOCRATES: And again, will things that we say are great, small, light, or heavy be any more what we say they are than they will be the opposite?

CIPACON: We are talking about pets, again, right?

Not Exactly Readings in Ancient Greek Philosophy: From Thales to Aristotle (p. 332). Hackett Publishing Company, Inc.. Kindle Edition.

Monday, January 08, 2018

"I'm a Stable Genius"

These wise words of the Dear Leader set me thinking about a situation that comes up every year or ten. I had a bunch of X-rays taken today and was quite intrigued by the giant CCD array being used, so I asked the tech some technical questions about it, only a few of which she knew answers for. She asked why I wondered and when I mentioned that I was currently an Astro student and interested in imaging, she said something like: "You must be really smart."

Usually I'm forced to give an honest answer and admit that I'm not nearly smart enough, but Dear Leader has given me an option.

I could just say that I'm a stable genius. I have spent more than a few hours in stables, and, often as not, I find that I'm one of the smarter animals present.

Not Exactly a Socratic Dialog

SOCRATES: Now, see whether you agree with me about this: if a carpenter attempts to do the work of a shoemaker, or a shoemaker that of a carpenter, or they exchange their tools or honors with one another, or if the same person tries to do both jobs, and all other such exchanges are made, do you think that does any great harm to the city?

CIPCON: Huh?

SOCRATES: But I imagine that when someone who is, by nature, a craftsman or some other sort of moneymaker is puffed up by wealth, or by having [b] a majority of votes, or by his own strength, or by some other such thing, and attempts to enter the class of soldiers; or when one of the soldiers who is unworthy to do so tries to enter that of judge and guardian, and these exchange their tools and honors; or when the same person tries to do all these things at once, then I imagine you will agree that these exchanges and this meddling destroy the city.

CIPCON: Sounds implausible.

SOCRATES: So, meddling and exchange among these three classes is the [c] greatest harm that can happen to the city and would rightly be called the worst evil one could do to it.

CIPCON: That's ridiculous.

SOCRATES: That, then, is what injustice is. But let’s put it in reverse: the opposite of this—when the moneymaking, auxiliary, and guardian class each do their own work in the city—is justice, isn’t it, and makes the city just?

CIPCON: That’s the dumbest thing that you've said today, and that's clearing a very high bar. You could really use a course in elementary logic.

Not Quite Readings in Ancient Greek Philosophy: From Thales to Aristotle (p. 303). Hackett Publishing Company, Inc.. Kindle Edition.

Republic

OK, I've only read the first three books of Plato's Republic, but I'm not one to let that dissuade me from an opinion. The tone of the Republic seems much different than the dialogs, possibly indicating that Plato is no longer attempting to recreate Socrates, but express his own thoughts, even though he still attributes them to Socrates. The Socrates of the Republic is far more didactic, declaiming his ideas and mostly winning the equivalent of "Well duh" from his interlocutors.

I suppose we can credit Plato with the invention of the totalitarian state, at least as an intellectual concept. He argues that by systematic thought control, a few well chosen big lies, and a bit of selective pruning of the unsuitable, the ideal governors and guardians of the state can be educated and entrusted with its governance.

My reaction was that this represents a woeful misreading of human nature, but one that continues to be made pretty widely even in our day - what Steven Pinker calls the "blank slate" fallacy.

Among other dumb ideas, he thinks that each person should only be permitted to do the things that he is best at.

SOCRATES: Well, now, we prevented a shoemaker from trying to be a farmer, weaver, or builder at the same time, instead of just a shoemaker, in order to ensure that the shoemaker’s job was done well. Similarly, we also assigned just the one job for which he had a natural aptitude to each of the other people, and said that he was to work at it his whole life, free from having to do any of the other jobs, so as not to miss the opportune [c] moments for performing it well. But isn’t it of the greatest importance that warfare be carried out well? Or is fighting a war so easy that a farmer, a shoemaker, or any other artisan can be a soldier at the same time, even though no one can become so much as a good checkers player or dice player if he considers it only as a sideline and does not practice it from childhood? Can someone just pick up a shield, or any other weapon or instrument of war and immediately become a competent fighter in an [d] infantry battle or whatever other sort of battle it may be, even though no other tool makes someone who picks it up a craftsman or an athlete, or is even of any service to him unless he has acquired knowledge of it and has had sufficient practice?

Readings in Ancient Greek Philosophy: From Thales to Aristotle (p. 265). Hackett Publishing Company, Inc.. Kindle Edition.

Friday, January 05, 2018

America's Illiteracy Problem?

Joe Scarborough has an Op-Ed in the Post today strongly suggesting that that the President doesn't read because he can't:

Mika Brzezinski and I had a tense meeting with Trump following what I considered to be a bumbling debate performance in September 2015. I asked the candidate a blunt question.

“Can you read?”

Awkward silence.

“I’m serious, Donald. Do you read?” I continued. “If someone wrote you a one-page paper on a policy, could you read it?”

Taken aback, Trump quietly responded that he could while holding up a Bible given to him by his mother. He then joked that he read it all the time.

I am apparently not the only one who has questioned the president’s ability to focus on the written word. “Trump didn’t read,” Wolff writes. “He didn’t really even skim. If it was print, it might as well not exist. Some believed that for all practical purposes he was no more than semiliterate. Others concluded that he didn’t read because he didn’t have to . . . He was postliterate — total television.” But “Fire and Fury” reveals that White House staff and Cabinet members believed Trump’s intellectual challenges went well beyond having a limited reading list: Treasury Secretary Steven Mnuchin called him an “idiot,” Cohn dismissed him as “dumb,” national security adviser H.R. McMaster considered him a “dope,” and Secretary of State Rex Tillerson infamously concluded that the commander in chief was a “moron.”

I'm the last person to defend the Dumpster, but I'm pretty sure I've seen him fluently reading a teleprompter, so I'm pretty sceptical of the claim. There does seem to be evidence that he never reads by choice though.

Wednesday, January 03, 2018

Old Times Not Forgotten

Age: Radioisotope 207Pb/ 206Pb dating of refractory inclusions (CAIs) found within chondritic meteorites, the oldest Solar System solids known, yields an age of 4.568 Gyr. Dating with other isotope systems yields similar ages. Chondrules, as well as most differentiated meteorites that originated within small bodies, solidified only a few million years later (§ 8.7). Rocks formed on the Moon and Earth are younger: lunar rocks are typically between 3 and 4.4 Gyr old, and terrestrial rocks are ≲ 4 Gyr old, although terrestrial mineral grains as old as 4.4 Gyr have been found.

de Pater, Imke; Lissauer, Jack J.. Planetary Sciences (p. 512). Cambridge University Press. Kindle Edition.

The ages of the refractory inclusions and the chrodrites tell us when they first solidified, almost certainly when the solar system was first condensing. From studies of regions of stellar formation, and deductions from basic physics, we know that stellar systems form in relatively dense molecular clouds containing a lot of dust. As the most of the mass concentrates in the star (I'm not considering multi-star systems here) most of the angular momentum ends up in the outer reaches which are flattened into a disk by gravity and viscous dissipation. The micron sized dust particles in these disks stick together, accumulating over a few million years into planetesimals each formed from roughly a trillion, trillion, trillion (10^36) dust grains.