Dark Matter Just Got Darker

Like most galaxies, the spiral galaxy M74 has more visible matter at its center than near its edges (NASA image)
In 1932, astronomer Dr. Jan Oort was studying the motion of stars in the Milky Way and could not understand his results unless he assumed there was a lot of matter in the galaxy that he was not seeing. As a result, he proposed the existence of matter that he assumed was very real but was not detectable using the instruments available at the time. Just a year later, astrophysicist Dr. Fritz Zwicky found that he had to make the same assumption to understand the Coma galaxy cluster. Several years later, he referred to this undetectable matter as “dunkle Materie,” which is German for “dark matter.”

However, the most compelling evidence for the existence of dark matter came more than 40 years later, when astronomers started measuring the speeds at which stars orbit the center of the galaxy they are in. If you look at the photo of a spiral galaxy above, you will see that it is much brighter at its center than it is at its edges. Based on such observations, it was assumed that most of a galaxy’s mass is located at its center. If that assumption were correct, it would mean that the stars near the center of the galaxy would orbit the center faster than the stars at the edge of the galaxy, just as the planets near the sun orbit much faster than the planets far from the sun.

In 1975, Dr. Vera Rubin and Dr. Kent Ford announced at a meeting of the American Astronomical Society that their studies indicated the stars in a galaxy orbit the center at roughly the same speed, regardless of where they are in the galaxy. This was a shock, and about the only thing that could explain it was the assumption that there was a lot of mass spread throughout the galaxy that could not be detected. Dark matter, which up until that time was mostly a curiosity, soon became a staple of modern astronomy. Today, astrophysicists estimate that 83% of the matter in the universe is dark matter – stuff that we cannot (as yet) detect directly.1

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The SEEK Graduation Ceremony

Yesterday, I had the distinct honor of speaking at the 2012 SEEK graduation ceremony. As I told the graduates, I do a lot of speaking around the world on many different topics, but speaking at homeschool graduation ceremonies is my very favorite kind of speaking engagement. I thoroughly enjoy being a part of such an important time in the lives of students and parents, and this specific graduation ceremony was particularly enjoyable. The event was efficiently organized and ran like a well-oiled machine, but more importantly, it was inspiring and uplifting.

It began with a short welcome by a graduate named Jensen. When people speak in public, they often take on a completely different personality. Sometimes, this is good, and sometimes, it is awkward. Jensen simply didn’t do that. He came up and welcomed us as if he was talking to each one of us individually. His personality came shining through in his welcome, and it set the tone for what was a very real, very enjoyable evening.

After a sincere opening prayer given by another graduate named Troy, we were treated to a graduate (Joe) who played and sang “If I stand,” by Rich Mullins and Steve Cudworth. Now I play the piano well enough so that I don’t offend anyone, and I thoroughly enjoy listening to those who can really play. I also sing in a way that doesn’t offend too many people, and once again, I love to listen to those who can really sing. Well, this student could really play and really sing, and he could do them both at the same time! The song, of course, is chock-full of meaning, and the chorus says it all:

So if I stand let me stand on the promise that you will pull me through
And if I can’t, let me fall on the grace that first brought me to You
So if I sing let me sing for the joy that has born in me these songs
And if I weep let it be as a man who is longing for his home

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Homeschooling with Heroes

The U.S. capitol building at night. (My photo)

Last week, I had the privilege of of speaking to the Bolling Area Home Educators (BAHE), a group of military homeschoolers who live on the Joint Base Anacostia-Bolling near Washington, DC. In other words, I got the opportunity to speak to heroes and their families. These brave men and women sacrifice so much in order to keep up safe, and those who choose to homeschool their children sacrifice even more. The nature of military life often means one spouse is gone for extended periods of time, which means that the spouse who stays at home must carry the burdens of parenting and educating alone. In addition, homeschooling is made significantly easier when you have a consistent network of other homeschoolers in your area. Because our military heroes rarely stay in one location for more than a few years, a military homeschooler rarely has the consistent support network enjoyed by most other homeschoolers in the U.S.

The trip got off to a very military start, because a good friend of mine has his private pilot’s license, and he agreed to fly me there in a Cessna Cutlass 172RG. Since we were flying into the DC area, there were all sorts of restrictions related to where we could fly, and he was actually given instructions on what to do if the fighter jets came to escort us out of a restricted area. Since there were so many restricted areas, I assumed we wouldn’t see any actual military traffic. It turns out that I was wrong.

We were flying towards the Manassas Regional Airport at an altitude of 5,000 feet. There was a solid layer of white clouds at around 2,000 feet, well below where we were. As we were flying, air traffic control told us to be aware that there were two F/A-18 jets doing some maneuvers in our area at about 3,000 feet. We scanned the sky below us and sure enough, we got to see them flying around! Of course, they were flying so quickly that they were hard to follow for any length of time, but it was amazing to watch from our point of view!

Once the bird’s-eye view of military maneuvers was over, we landed, and it was time to get a ground-level view of military life and homeschooling. Because the guest housing at Joint Base Anacostia-Bolling was full, we ended up staying in the guest quarters at Fort Belvoir, another military base in the D.C. area. It was very interesting to see life on the base from the inside.

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Those Plates, They Are A-Movin’

This map of a portion of the earth shows the motion of specific locations relative to a fixed point. The arrows indicate the velocity of each location, and the blue lines are the outlines of what are thought to be the plates that are producing this motion. (Click for credit)

In the theory of plate tectonics, the earth’s surface is broken into several distinct plates which move about, carrying the continents with them. As a result, a fixed location on the planet is not really stationary. It is actually moving along the earth! We don’t notice the motion, of course, because it is happening very slowly. However, according to the theory, it is always happening. If scientists make certain assumptions about how this motion occurred in the past, they can conclude that at one time, all the continents on earth were grouped together in a supercontinent called Pangaea. Over time, the motion of the plates then separated the continents into the positions we see today.

If you assume that the plate motions we think are happening today are representative of how fast the plates have always moved, you find that it would take hundreds of millions of years for the continents to have moved from Pangaea to where they are today. However, many young-earth creationists think that plate motions were much faster during the worldwide Flood, and some have produced detailed computer models that attempt to explain how the Flood happened in the context of this catastrophic plate tectonics. Other young-earth creationists are skeptical about plate tectonics, claiming that there isn’t a lot of evidence to support it.

I tend to disagree with the young-earth creationists who are skeptical about plate tectonics. While I am definitely not a geologist or geophysicist, I do think there is a lot of indirect evidence to indicate that the plates are real and that they are really moving. Interestingly enough, I recently ran across an article by Dr. John Baumgardner that, in my mind, really clinches the case for the reality of plate tectonics.1 Not only that, the data used in the article are just plain cool!

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The Freshwater/Saltwater Shuffle

Question: What is the significance of the freshwater fish groups represented by the individuals pictured below?

Saddled Bichir, a representative of the Polypteriformes. (Click for credit)

Atlantic sturgeon, a representative of the Acipenseriformes (Click for credit)

A bowfin, representative of the Amiiformes (Click for credit)

Believe it or not, the answer is as follows: The most recent evolutionary analysis says that nearly all saltwater fishes* evolved from fishes that were members of these freshwater groups!

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The 2012 Midwest Homeschool Convention

I spent the past weekend in Cincinnati, the site of the Midwest Homeschool convention. This was the original Great Homeschool Convention, and it is one of the most popular homeschooling conventions in the nation. As usual, the attendance was huge, and I gave a total of seven talks over a period of 2 and a half days. There was a steady stream of people coming to my booth to ask specific questions, so when I wasn’t giving a talk or answering questions on stage, I was generally answering questions at my booth. It was very busy, but I had a blast!

I got to meet the Sleepy Man Banjo Boys at this convention. These three young men started posting videos of their bedroom practice sessions on YouTube (an example is given above), and because of their incredible talent, the videos almost immediately went viral. The videos have millions of views, and the Sleepy Man Banjo Boys have appeared as musical guests on The Late Show with David Letterman and the Today Show on NBC. In addition, when they appeared on the Mike Huckabee show (Fox News), they were so popular that they were invited back the very next week. They are the only musical guests to appear in back-to-back episodes of that show.

These talented young men are homeschooled, so it was natural for Great Homeschool Conventions to invite them to appear. They gave a great performance, and later on, I happened to be dining at the same restaurant as they were. As a result, it was my honor to meet them personally. Not only are they excellent performers, but they are also genuinely fine young men who have the right priorities in life. They are just another example of what wonderful things can be accomplished as a result of the individuality and flexibility of home education.

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The MidSouth Homeschool Convention

Over the past weekend, I spoke at the Midsouth Homeschool Convention, which is a part of the Great Homeschool Conventions series. It was held in Memphis, TN, so pictures and tributes to Elvis were abundant everywhere except the convention itself. I didn’t give as many talks at this convention as is typical, so that left more time for my favorite part of a homeschool convention: talking with students and parents.

Since I am not selling anything at homeschool conventions these days, my booth in the exhibit hall looks rather odd. It consists of a plain black-and-white sign that just has my name on it, an empty table, two chairs, and me. In contrast to most of the other booths that try to attract people in with color banners, comfy couches, potted plants, and videos, mine looks pretty bare. The CEO of Home Educating Family thought it was just too bare, so he added one “decoration.” On my plain white sign, he wrote “The Doctor Is In” and gave me a sticky note that said “OUT.” When I left my booth, I could cover the word “In” with the sticky note. Perhaps it doesn’t sound funny to you, but I thought it was hilarious, and I used it the whole time I was there. I regret that I did not take a picture of it before I left.

Although the bulk of this post will deal with a question I got in one of my talks, I do want to mention one thing that really impressed me. It turns out that during the conference, some low-life broke into several of the vendors’ vans. While most vendors didn’t lose much, one vendor’s van was loaded with an iPad and some other important technology, so they were looking at a serious financial loss. In order to help them out, several other vendors took up a collection. Now these vendors are all competitors. If you buy a math course from one vendor, that probably means you won’t buy a math course from any other vendor. Nevertheless, the vendors all gave generously. That really impressed me. Even in business, Christians should put compassion first, and that’s what I saw happening in Memphis.

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How Meaningful are Genome Comparsons?

The information in DNA is stored in specific sequences of the nucleotide bases adenine (A), thymine (T), cytosine (C), and guanine (G). (Click for credit)

We hear a lot about how similar the human genome is compared to the chimpanzee genome. As I have discussed previously, if we compare the genomes one way, they are 72% identical. If we compare them another way, they more than 95% identical. If we compare them yet another way, they are 88-89% identical. That’s a wide range of results! Why can’t we say definitively how similar the human genome is to the chimpanzee genome? There are probably several reasons for this, but I want to highlight a basic one. Even though the human and chimpanzee genomes have been sequenced, we still don’t know them as well as you might think.

To understand why we don’t know these sequenced genomes very well, you need to know a bit about how DNA stores information. As most people know, DNA is a double helix. Each strand of this double helix has a sequence of chemical units called nucleotide bases. There are four different nucleotide bases: adenine (A), thymine (T), cytosine (C), and guanine (G). Taken three at a time, these four nucleotide bases code for a specific kind of chemical called an amino acid. The two strands of the double helix hold together because the nucleotide bases on one strand link up with the nucleotide bases on the other strand.

As shown in the illustration above, the way the nucleotide bases link up is very specific. Adenine (A) links only to thymine (T), and cytosine (C) links only to guanine (G). Because of this, if you know the sequence on one strand of DNA, you automatically know the sequence on the other strand. After all, A can only link to T, so anywhere one strand has an A, the other strand must have a T. In the same way, C can only link to G, so anywhere one strand has a C, the other strand must have a G. So the two strands of the DNA double helix are held together by pairs of nucleotide bases.

As a result, we count the length of a genome in terms of how many base pairs there are. The illustration above, for example, has 14 base pairs (the black G is hiding a C behind it, and the black A is hiding a T behind it). Obviously, then, the larger the number of base pairs in the genome, the longer the genome is. Believe it or not, even though the human and chimpanzee genomes have been sequenced, we don’t know for sure how long either of them are!

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Jesus Talks to Pilate After the Resurrection?

I have a little-used category on this blog called “Christian Drama.” It is there because from time to time, I write dramas that are performed at my church. Back in January of 2011, for example, I wrote a 25-minute drama based (very loosely) on the end of John Newton’s life. It turned out pretty well, and I posted the video here so that others might enjoy it. Since then, I have written a few dramas for church, but I didn’t consider any of them worth posting.

Yesterday, of course, was Easter Sunday, which I consider to be the most important Sunday worship service of the year. I was asked to come up with a short drama for the service, and I agreed – with some hesitation. The problem with writing a drama about Easter is that it’s hard to come up with something new. The account of Jesus’ resurrection is so important to the Christian church that it has been written about, preached about, and depicted in all sorts of different ways. How do you come up with something that is original and at the same time meaningful?

Well…here’s what I did. I decided to present a fictional (but maybe plausible?) presentation of Easter from Pilate’s point of view. Pilate was governor of Judaea at the time, so it fell on him to order Christ’s crucifixion. His wife warned him to “have nothing to do with that righteous Man; for last night I suffered greatly in a dream because of Him” (Matthew 27:19), but he felt pressured by the crowd to order Christ’s execution. I suspect that as time went on, he regretted that decision. I wondered how he might deal with that regret. I then wondered how Jesus might have helped him.

Below the fold you will find a wholly made-up encounter between Jesus and Pilate shortly after the resurrection. This is not meant to have even the slightest hint of historical accuracy. It is just meant to communicate the gospel’s message of forgiveness. I hope you enjoy it.

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Just How Evil Is This “Evil Twin”?

This cold-water coral flourished in acidic waters once it was given time to adapt. (Click for credit)
Ocean acidification has been called the “evil twin” of global warming. That’s because rising carbon dioxide levels are not just supposed to result in an overly-warm world. They are also supposed to result in an overly-acidic ocean. How does carbon dioxide in the air affect the acidity of the ocean? Well, the ocean absorbs a large fraction of the carbon dioxide that is in the atmosphere. Some of that carbon dioxide then reacts with the water in the ocean, producing carbonic acid. The more carbon dioxide there is in the atmosphere, the more carbon dioxide the ocean will absorb. As the ocean absorbs more carbon dioxide, more carbonic acid will be made. Thus, rising carbon dioxide levels will lead to a more acidic ocean.

Unlike the link between rising carbon dioxide levels and global warming, the link between rising carbon dioxide levels and ocean acidification is straightforward and has already been seen to some extent. As you may remember from high school chemistry, acidity can be measured using the pH scale. A pH of 7 is neutral. A pH greater than 7 indicates a basic solution, while a pH lower than 7 indicates an acidic solution. The key for this discussion is as follows: the lower the pH, the more acidic the solution. Well, according to the Ocean Studies Board of the National Research council:1

The average pH of ocean surface waters has decreased by about 0.1 unit—from about 8.2 to 8.1—since the beginning of the industrial revolution, with model projections showing an additional 0.2-0.3 drop by the end of the century, even under optimistic scenarios

Now this might not sound like a big change, but the pH scale is logarithmic. That means if the pH decreases by 1 unit, the acidity has increased by a factor of 10! Thus, a drop in pH of 0.1 is actually a change of 26%. This means the ocean is 26% more acidic than it was before the beginning of the industrial revolution. If the models are correct (and who knows if they are), the ocean will increase in acidity by an additional 58 to 100 percent by the end of the century!

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