Science and Interstellar

Salon has a brief excerpt from Kip Thorne’s book The Science of Interstellar, in which the author/physicist attempts to explain some of the scientific concepts used in the film. I still haven’t seen Interstellar, but I’ve heard mixed things from other physicists and astrophysicists (mostly that the visuals are cool but the plot is lacking and fairly nonsensical).

The excerpt isn’t bad but I think it’s probably a bit too high-level for most readers since all the material explaining many of the concepts is hopefully in the book but left out of the Salon piece.

It seems that the science behind the crazy things like wormholes and black holes in the film are based on the idea that our universe is a four-dimensional space embedded into a larger space. Think of this as a higher dimensional analog of creatures living on the surface of a ball. To those creatures, the universe (a sphere) is three dimensions, but we know that it is four (one of those is time in both cases). This idea shows up quite a bit in modern theoretical physics and in some sense is the basis of string theory and M-theory, a generalization of string theory. In both cases more than four dimensions are required to get sensible physics out of the theory, so these extra dimensions can be both small (compactified) – leading only to quantum effects – or large, where the particles and fields of the Standard Model are somehow confined only to our four dimensional space. In some theories, you can let gravity operate in all dimensions, which can explain why gravity is so much weaker than the other forces: it operates in more dimensions, diluting its apparent strength. This last points appears to be an important part of the physics of the movie.

A few things on terminology:

  1. The bulk: The greater dimensional space that the universe is embedded into. Gravity can travel throughout the bulk, so objects in other universes can have effects on ours through gravity.
  2. Branes: Higher dimensional objects. A particle is 0 dimensions, a string is 1, and a brane is an arbitrary number (up to the number of dimensions in the bulk). Our universe can be seen as a 4-dimensional (3 space + 1 time) brane embedded in the bulk.
  3. AdS: Anti-de Sitter space. This is the name for the spacetime with a uniform negative curvature. In the film, we are not creatures living on a sphere (which is the analog for de Sitter space), but rather creatures living on an infinitely large saddle or potato chip. In reality, as far as we can tell, space is flat, so any curvature would have to be incredibly small.
  4. Tidal forces: Non-uniform forces on different parts of an object. For example, the force of gravity on Earth from the moon is slightly stronger on the side of Earth nearest the moon, so fluids such as water are being pulled to the near side of Earth (instead of everything being pulled together by the same amount), creating tides.
  5. Action: The time integral of a Lagrangian or integral over space and time of a Lagrangian density. In field theories, the Lagrangian density is a function of fields and field derivatives that contains all the physics of the system. The system evolves in such a way that extremizes (maximizes or minimizes) the action, so the evolution of the system can be understood by applying calculus of variations to the action. Part of what theoretical physicists do is to come up with Lagrangians (either for fundamental theories or for effective theories applying only under certain conditions) that describe either novel or poorly understood physical systems in order to understand their properties. These are often designed to fix problems with our current incomplete theories. For example, the Higgs boson comes out of a Higgs field added to the Standard Model Lagrangian in order to fix some problems with unitarity and gauge invariance that are introduced when massive vector bosons (the W and Z) are added to the theory.

CU Wins NCAA Cross Country Championship

Over the weekend, the Colorado men’s cross country team won the NCAA Division I championship for the second straight year. The race was a 10k course in Terre Haute, Indiana. The Colorado team ended up with 65 points although the top two runners were both from Oregon, with the best finishing with a time of 30:19. Stanford came in second with 98 points. The northeastern region sent an all-Ivy set of individual qualifiers with two from Columbia and one each from Harvard and Yale. The Colorado women’s team also did quite well, ending up at #7 out of 31 qualifying teams. For some reason, the women’s course is only 6k instead of using the same 10k as in the men’s race.

New T2K CCQE Neutrino Cross Section Result

T2K released a preprint today measuring the charged-current quasielastic scattering cross section of muon neutrinos on carbon using the ND280 off-axis near detector. The measurement reports the total cross section, the double-differential cross section using muon kinematic variables (muon momentum and angle with respect to the beam direction), and also reports a fit to the axial mass parameter of a theoretical model. There is good agreement between the measured flux-averaged cross section and the expectation from theory, and agreement between the measured and expected differential cross sections are also mostly good. The axial mass extraction is also reasonably consistent with expectations, so overall, everything seems to fit pretty well to expectations from the NEUT Monte Carlo generator and also from previous measurements.

Problems at ESPN Over Evolution?

So former Red Sox pitcher/failed wannabe videogame mogul Curt Schilling has apparently been spewing a bunch of ignorant nonsense over Twitter in recent days, mostly involving attacking evolution. Schilling is currently one of ESPN’s many famous former players on the payroll to provide on air commentary once in a while. One of the networks actual commentators and journalists, Keith Law, responded with a series of tweets answering some of Schilling’s inane questions that supposedly should stump supporters of evolution. As a result, the Lawhas been ordered off Twitter for a few days. ESPN has been quite evasive over the official reason for this (they say that it’s not about his opinions), but the timing suggests that the suspension is for embarrassing Schilling in public. Unlike Schilling, Law is employed to provide actual content, so we would hope that the network would give him the benefit of the doubt over this. He kept his tweets much more factual and respectful than Schilling’s.

Erdogan on Latin America

In one of the more absurd news stories of the past week or two, Turkish president Erdogan claimed last week that when Columbus reached the New World he found Islam already spreading throughout the population and even saw a mosque on top of a hill in Cuba. He went on to offer to build a mosque on top of that same hill in Cuba. Needless to say, Erdogan’s remarks – which are not in fact a joke – have been met with near-universal mockery. Despite this, Erdogan is continuing to insist that what he said is true. The Washington Post has some interesting thoughts on why Erdogan isn’t backing off his comments and also has a blog post reviewing the sources he’s probably citing. The Post’s Ishaan Tharoor thinks that maybe Erdogan doesn’t actually care about the truth and this whole affair is a purely cynical political ploy to shore up support for Erdogan by somehow declaring that denying these claims is tantamount to insulting Muslims. The Guardian also reports on this but avoids any editorial comments.

Reportedly, the story about the mosque comes from some random paper from the ’90s that used a version of Columbus’ journal recorded by Bartolomé de las Casas in the mid-1500s. The actual journal has been lost, so there is no true primary source. Wikisource has a copy of the Spanish text of an 1892 edition here. The relevant portion is the entry for October 29th, where it says:

Señala la disposición del río y del puerto que arriba dijo y nombró San Salvador, que tiene sus montañas hermosas y altas como la Peña de los Enamorados, y una de ellas tiene encima otro montecillo a manera de una hermosa mezquita. [from Wikisource]

Which I would translate (my Spanish isn’t great but you can easily find better translations online) as:

He [Columbus] describes the position of the river and port mentioned above and named San Salvador [Holy Savior], which includes beautiful tall mountains similar to the Peña de los Enamorados [Lovers’ Rock], and one of them has on top of it a ridge [or mound/hill] that looks like [lit. in the manner of] a beautiful mosque.

The Spanish text looks like it’s been modernized but if we assume that it is a reasonably faithful rendering of de las Casas’ manuscript it’s clear that the mosque Erdogan mentions exists only in his own mind. The reports that the mention of a mosque in the journal are metaphorical are understating how clear it is that it’s not describing an actual building.

As for the additional claim that Islam was spreading throughout the Americas prior to Columbus, there is no credible evidence accepted by legitimate historians of this. To a non-expert like me this seems highly unlikely even if we accept the claim that contact between the Muslim world and Latin America (and the Caribbean in particular) was common before Columbus’ first voyage.

Consider the political context of Spain in 1492 – at that time a union between Castile [Castilla] ruled by Isabel I [called Isabella in English for some reason even though that’s Italian and the name is actually Elizabeth] and Aragón, ruled by Fernando II [i.e. Ferdinand in English]. At the beginning of the year, the emirate of Granada fell and was subsumed into Castile. Shortly after, all Jewish people in Spain were ordered to convert to Christianity or leave the country. However – and this is very important to note – Muslims were still allowed to remain for another 10 years until the Spanish monarchy broke the terms of the Treaty of Granada ensuring the rights of Spanish Muslims.

So, when Columbus left from a port in Andalucía, he and his crew left a country that had just ended centuries of warfare between various competing Christian and Muslim states (and Granada had been allied with Castile at various points anyway) and still had a large minority of Muslims who were supposed to be tolerated by the authorities. Some of the crew may have even been converts or descendants of recent converts. They traveled west, expecting to reach Asia. Had they reached the Caribbean and found that many among the Taíno people practiced Islam, we would almost certainly know. Columbus and his crew must have been at least somewhat knowledgable about Islam (even the metaphorical usage of the word mosque assumes that the reader knows what one looks like), and they thought that they had reached Asia, where it might not be surprising to find people practicing a familiar religion. Furthermore, had many in the Americas already practiced any religion known to Europeans, we might expect the writings of men such as de las Casas (who, though he came to regret it, was shamefully one of the first to call for the use of African slave labor in the colonies) and Sepúlveda to have very different views on the treatment of the native people of the New World.

Now, is it possible that an errant ship here or there from Asia, Europe, Africa, or Oceania could have reached the shores of the Americas? I don’t see why not, but to the extent that this ever happened, it would be little more than a historical curiosity. Even the purported (as far as I know its identity has largely been confirmed by archaeologists) Norse colony in Newfoundland and any possible related colonies on the North American mainland left little to no influence on the course of history other than inspiring some some literature. At the very least, the lack of Old World diseases in pre-Colombian America and the staggering death tolls of the plagues introduced by Europeans soon after arriving would appear to preclude any significant or sustained contact between the people of the Americas (or at least people outside the Arctic region where the continents are close together) and the various interconnected societies of Europe, Africa, and Asia.

Thus, this appears to be just one in a long line of dubious attempts to stake a claim to a discovery of the New World prior to Columbus and just one in a long line of even more dubious attempts to co-opt the cultural identities of the native peoples of the Americas. Columbus remains important not because he was the first to make the trip – he almost certainly wasn’t – and not because he was a good man – he wasn’t – but rather because of what happened after his first voyage. For better or worse, Columbus brought knowledge of the existence of the New World (even if he still thought it was Asia) to the rest of Europe and helped usher in an era of European colonialism.

Speaking of Football…

While MIT is now past the first round of the D-III tournament, to no one’s surprise, Columbia football has now lost it’s 21st game in a row and has no wins in the last two years. One more game and they’ll be halfway to tying their epic 44-game losing streak in the mid-80s. As with nearly every other game in the past few years, the team lost in a blowout, this time to Brown.

MIT Football Undefeated

In stark contrast to Columbia’s historically awful last couple seasons, MIT football is undefeated in regular season play and now in the NCAA Division III tournament. Their first round game is going on right now. This is not a joke. MIT really does have a football team and really is undefeated.

MIT plays in the New England Football Conference and in NEWMAC for most other sports. Going undefeated is quite the feat for MIT. Division III, if you don’t know, does not allow for athletic scholarships unlike Divisions I and II. The Ivy League is Division I but operates under rules similar to Division III due to a special rule in the D-I membership guidelines, with no scholarships and major recruiting restrictions (as well as very limited academic support for athletes compared to the rest of D-I). Even Columbia would probably beat nearly any D-III school at football or basketball but wouldn’t be expected to be competitive with anyone in D-I outside the Ivy League and maybe the Patriot League.

An update:

MIT actually won their first round game to reach the round of 8.