Tuesday, March 17, 2015

Phil Plait's CNU Talk

Plait is promoting his new book Death From The Skies. He gave a highly entertaining talk last night at CNU to an appreciative audience which included, I'm happy to say, many students.

My only complaint is that he focussed exclusively on asteroid and comet impacts. I was hoping for a discussion of more exotic extinction events, like Betelgeuse going super nova (any yom now!) or gamma ray bursts.

So I guess I'll have to buy the book. Before it's too late.

D is the New F (repost from my other blog)

The Myth of Raising Standards through Minimum Grades 

There is a trend at America’s colleges and universities to raise standards by instituting minimum grades.

Typically the minimum grade is a C-. It may be in the form of a prerequisite: You may not take BIOCHEM 202 unless you have completed BIOCHEM 201 with a grade of C- or better. Or it may be in the form of program requirements: You must achieve a grade of C- or better in all courses required by the major.

This is not raising standards. It is creating grade inflation and grade compression.

Imagine you are teaching physics to a senior biology major. Imagine the student is in the second semester of his senior year. (FACT: Biology students often delay taking a physics until the last possible moment!) Now imagine the student needs a C- to graduate. When you compute your grades you find that this student earned a D+. What do you do? Do you give a biology student a D+ in a physics course, preventing graduation?

Well, what you are likely to do (and what I've done) is to give a C- because—you simply don’t want to prevent a student from graduating because of the minor difference between a D+ and a C-.

 I have seen grade distributions that confirm this. Distributions that demonstrate that professors show a great reluctance to give D’s if the student needs a C-. That’s grade inflation (giving higher grades than deserved) and grade compression (C- now incorporates earned C-’s and D’s—patently unfair to the true C- student.)

Employers know what a D means (or used to mean.) They can no longer be confident what a C- on a transcript means.

Another effect: I just (as in new to this version of the post) had a student ask me if she should drop a class. You see, the final day to do so is fast upon us, and her professor told her that it will almost be impossible for her to raise her grade from a D to a C. That means, given D being the new F, she'll have to repeat the course anyway.  

This is all based on apple pie “raise the standards” nonsense. In my view, if a student completes BIOCHEM 201 and is not ready for BIOCHEM 202, the student should fail 201. A D has historically meant a passing grade. It includes the message: you passed, barely, and if you don’t work harder we are not optimistic that you can do well in 202, but we are going to let you try. Because, well, you did pass. Likewise if you fail to master the content of a course required for a major then you should fail the course. If you get a D then you pass, and let the D stand on the transcript.

In the twisted universe of minimum grades, there is no difference between a D and an F. They are equivalent failing grades. The D is the new F.

Monday, March 16, 2015

Christians Behaving Badly

1) Dear flock, I need $65M for a new jet. Because Jesus.
2) I have committed additional crimes. But jail == persecution.

Of course Christians can and do commit crimes. What is unacceptable is when they cry persecution when society makes them pay for their crimes. Stephen was persecuted. Kent Hovind was not. 

Jerry is still Jerry

I see that in my two year hiatus Jerry Coyne hasn't gotten any smarter regarding anything outside his discipline. In this post he criticizes CNN for printing a silly article on whether Judas is in heaven or hell. Well, to be fair, it is a downright awful piece. But that's beside the point. Look how 'ole Jerry levels his criticism. The writer of the piece, a pastor by the name of Craig Gross, does not actually take a stand on Judas' eternal fate. And at one point Gross writes:

Let me tell you a little bit about what the Bible says about Judas: 
He was personally chosen to be an apostle by Jesus. 
He spent 3 1/2 years traveling with Jesus. 
He saw all the miracles of Christ in person. 
He watched as Christ healed the sick, raised the dead and cast out demons. 
In terms of experience with Jesus, whatever you can say about Peter, James and John, you can say about Judas. 
On top of all this, he handled the money, which is most of the time the most trusted one in the bunch. No one suspected that Judas would betray Jesus, which tells me he was a believer. 
His life was changed. 
He knew Jesus personally. 
In a dark moment of his life, he made a mistake. A big one. He sold Jesus out for 30 silver coins or so. The moment he knew what he had done, he felt remorse, and he killed himself. 
I am not here to debate theology. The facts are the facts. 

(Boldface added.) Now any reader with normal reading comprehension and normal levels of charity regarding imprecision of writing would understand and grant that Gross is arguing that it is indisputable that these points are found in scripture. And that Gross calls them "facts" for purposes of the in-family (or at least among those who for the sake of argument accept the premise, i.e. that it is a legitimate question within biblical Christianity) debate regarding Judas' fate. 

But not hair-trigger Jerry. Missing, uncomprehending, or just ignoring that Gross's lead-in was "Let me tell you a little bit about what the Bible says about Judas" Coyne takes the most uncharitable possible interpretation, that Gross was itemizing data regarding Judas that he expects unbelievers like Jerry to accept as cosmic facts simply because they are in the bible. A normal person would grant that Gross understands that a) if you do not accept the bible as a holy book then b) you would also not accept relative bible minutia as scientific fact.  

An indignant Jerry, completely missing the boat, responds
Seriously? Those are facts? Who says so? Clearly, for Gross “facts” consist of “whatever the Gospels say.”

Let's do baby steps Jerry. Gross is not asking you, Jerry Coyne, to accept as fact that Judas saw all of Jesus' miracles. That would be silly, don't you think, given that he knows you don't affirm the miracles in the first place. This is the hard part: He is making a "here's all that we know for sure" baseline for those who accept, perhaps only in a "for the sake of argument" way, biblical Christianity, and want to debate the fate of Judas.

As I remember he often did, Jerry then doubles down on his stupidity, offering us his theology:
But if I were a Christian, the answer would seem clear to me. Without Judas’s betrayal, Jesus might not have been crucified, and his whole mission—to expiate the sins of humanity—would have been a dismal failure. Judas thus played a necessary role in saving all of us, and so he should find his reward in heaven.
We could ask, say, a Christian sixth-grader why what is clear to Jerry is in fact not clear at all. I am confident that her or she would answer something along the lines that it is possible that Judas meant the betrayal for evil (and is accountable) while God used it for good. But what would be unfair, because that would be resorting to our conveniently and intentionally impenetrable "sophisticated theology" that we unleash anytime someone like Jerry shows how we are obviously wrong.

Finally Jerry, angry and bewildered, writes:
But the question of whether Judas is in hell is far less important than this question: Why did CNN publish such a ridiculous piece?

Yeah, why CNN published the piece is a really important fate-of-the-free-world question.

Perhaps CNN did a calculation regarding the choice:

a) Let's write what Jerry Coyne finds acceptable, or

b) Given that we often publish opinion and op-ed and human interest and fluff, and given that Easter is upon us, and given that, say, half our readers self-identify as Christians, let's publish an opinion piece that they might find interesting.

And they chose b, those bastards.

Saturday, March 14, 2015

Pi = 3 (Reposted in honor of Pi Day)

A “proof” that purportedly demonstrates that the Bible is scientifically unreliable comes from the description of the furnishings of Solomon’s Temple. We read:
Then he made the sea of cast metal. It was round, ten cubits from brim to brim, and five cubits high, and a line of thirty cubits measured its circumference. (1 Kings 7:23)
Aha! A circumference of thirty and a diameter of ten means pi =30/10 =3. Either Solomon’s Temple was built in Indiana or we have a serious problem.

Or do we?

(The sea, by the way, was a humongous brass basin almost certainly used by the priests for ceremonial washings.)

Notice again the same fallacy as in the “bats are birds” complaint. The underlying assumption is that the ancients were morons. (This assumption is usually reserved for ancient Hebrews alone. The Aztecs, for example, are assumed to be cultural and scientific geniuses who knew the secrets of the Super String landscape, which they enjoyed discussing over high protein meals derived from their own species.)

Any civilization building anything circular would have known that the ratio of the circumference to the diameter is slightly greater than 3. The Mesopotamians of a much earlier era used the approximate value of 25/8 = 3.125. The Egyptians may have had a much better value long before Solomon’s Temple. Here we see the assumption of stupidity: The Hebrews either didn’t know what their neighbors knew or they did know but didn’t bother to put accurate information into their sacred writings, in spite of its potential effect of weakening claims regarding the veracity of the holy words.

Not that any of that matters, because what is provided in the Bible is a description (“He made”), not a blueprint (“Makest Thou”).

There are several possible explanations—each one could stand alone but all may contribute to a certain extent.

The simplest explanation is technological. It was not possible to cast a brass object of such size in the shape of a perfect circle. So if one intended, roughly, to give its size using the (redundant) parameters of a circle—circumference and diameter, there would already be built into the description an error—given that the object was only approximately circular.

So the simplest explanation is that we are being given a rough description in terms of approximate dimensions of an imperfect shape.

However, even if we assume that the sea was a perfect circle, there is no problem. For even if it was perfectly circular, it was not infinitely thin.

The figure on the left shows a representation. What if the sea had some thickness? And what if, as in the artist’s conception shown, it was even flared at the rim? Then the 10 cubits could refer to the “outside” distance across, giving us information on its total size, while the circumference could be the inner circumference, telling us about the sea’s capacity.

Is this plausible? Let’s continue on with the biblical passage, just after where the dimensions are provided, and look at further descriptive details:
24 Under its brim were gourds, for ten cubits, compassing the sea all around. The gourds were in two rows, cast with it when it was cast. 25 It stood on twelve oxen, three facing north, three facing west, three facing south, and three facing east. The sea was set on them, and all their rear parts were inward. 26 Its thickness was a handbreadth, and its brim was made like the brim of a cup, like the flower of a lily. It held two thousand baths. (1 Kings 7:24-26)

In verse 26 we are told that its thickness was a handbreadth, which fits nicely with the value of Δ ≈ 4.1 inches. We are also told that the brim was like the brim of a cup, which is consistent with the conceptual drawing. Either or both of these effects renders the criticism, which is based on a infinitely thin perfect circle, meaningless. The numbers given are perfectly compatible, even with a literal reading, as long as verse 26 in addition to verse 23, is taken into account.

Finally, although it need not be invoked in this case, it is also known that eastern writing of the time was numerically imprecise—we often see this in biblical writings through the use of rounded numbers—for example in discussing Job’s possessions. This potential mitigating factor, that the writers of that era (biblical or not) treated numbers differently than we do, along with the fact that they also treated quotes differently (as faithful to the content of someone’s statement but not necessarily the precise wording) are two inconvenient (for our critics) established truths that they label as copouts. As I mentioned in the previous post, other off-limits methods to counter their claims include arguing on the basis of figure of speech, hyperbole, translation error, or proper context. For their claims regarding biblical inconsistency with science to hold water they cannot relax their unspoken assumption that the ancient Hebrews were idiots and their demand that all contested passages be evaluated, not just hyper-literally, but also as if they were written using modern style and practices.

Friday, March 13, 2015

Interesting Physics Problem that seems to require a Mathematics Answer

Consider the situation shown. There are four small conductors, each with charge either +q or the opposite, -q. There are arranged as shown in (a). One +q is arbitrarily close to one -q. Likewise for the other pair of opposite charges. And the two sets of opposite pairs are arbitraily far apart. Now suppose (b) I connect the distant opposite charges with thin wires. What will happen? There are two possibilities:

1) Nothing happens, because (recall opposites attract) each charge +q will be much more strongly attracted to the opposite charge -q that is close by, because the strength of the attractions drops as the square of the distance. If I make the opposite charge at the end of the wire a thousand times farther away than the neighboring opposite charge, then the neighbors will have a million times stronger attraction. The charge on the end of the wire simply cannot overcome that attraction of the neighbor, and so everyone stays put, fat dumb and happy.


2) The charges will run along the wire, canceling each other out.

In the first case (as in (a)) there will be varying electric potential (voltage) and electric fields, the potential and field being very, very big near the charges. The second case is featureless: there will be no electric fields and constant (taken to be zero) electric potential. As if nothing is there.

These are two very different possibilities.

I don't know how to do "the answer is below the fold," or I would!

The answer is (2). The charges will run along the wire and cancel leaving us with no fields. I can't come up with a good physics explanation--to me the wrong answer (1) has a plausible physics explanation. But mathematics answers the problem unambiguously.  It does so via a uniqueness theorem that applies to the partial differential equations (from physics) that apply to this situation. A uniqueness theorem says something like this: If you find a solution, by any means, then you have found the one and only, i.e., unique solution. A problem cannot have two solutions.      

The relevant uniqueness theorem is this: In a situation such as that shown, the electric field is uniquely determined if the total charge on each conductor is given.

But when we connect the charges by wires we effectively covert the two separate conductors, one with +q and one with -q, into a single conductor with zero total charge (c). So our four conductors become two conductors with no charge. Such an arrangement has no field and a featureless potential.

This is an unusual problem in that (at least to me) the "obvious" physical solution is trumped by the mathematics. A uniqueness theorem from the field of partial differential equations say the answer, physics tuition be damned, must be (2), and so it is.

Phil Plait coming to CNU

The Bad Astronomer Phil Plait is coming to CNU and the Virginia Living Museum on Monday March 16, 7p.m.


Asteroid impacts! Cometary debris! Extinction level events! These are the topics covered in this science based but fun look at giant impacts from cosmic objects. Dr. Phil Plait (the Bad Astronomer) talks about how these events have shaped our history, how they may do so again, and why Hollywood always seems to get them wrong. And lest you think it’s all doom and gloom, Dr. Plait details how we might prevent the next great impact from ruining our whole day. The talk, sponsored by the Virginia Living Museum, will be at the Ferguson Center for the Arts, Christopher Newport University, at 7 p.m. followed by a reception with Dr. Plait at the Virignia Living Museum’s rooftop Abbitt Observatory with night sky observing. Dress for the weather as telescope viewing will be available (weather permitting). $10. Purchase at 757-595-1900 or thevlm.org (service fee) in advance, tickets will not be available at the door.

Thursday, March 12, 2015

Creation Views

This was a one-class Sunday School I did recently. It was a bit controversial. A few people did not like the fact that I argue that a Christian can accept (theistic) evolution.

The pdf for this class is here.

Limited Atonement

I will be doing a Sunday School on that much maligned doctrine. Just like old times, I'll post the lessons here. Even though it starts in two weeks I haven't exactly decided on my approach.

Reciprocal Links

I removed links to blogs that no longer link here. If you wish to restore reciprocal links let me know.