Lake Braddock

It was a fateful day in September 1995. I had just finished my dissertation at UCLA (though I wouldn’t officially graduate until December) and I had obtained a postdoctoral fellowship at the Naval Research Lab in Washington, DC. I flew out to look for a place to live in advance of our arriving October 1. My good friends Bill and Kim Amatucci put me up for a couple of days, though Kim was in the throes of her last trimester of her pregnancy with Nick. I didn’t see much of her. Now that I think of it, I might not have seen her at all!

Jennifer, a realtor, drove me around all day looking at houses to rent. At the end of the day, we visited 9637 Westport Lane in Burke, VA. The house was nothing special, and in fact the family was in the process of moving out, so it was a mess. However, it had the requisite 3 bedrooms (one for me and Kathy, one for Katie and Megan, and one extra - Sarah had not yet arrived), and was fine. I hadn’t yet found the place. But it was near sunset, so when we left the house, I walked on a path up a small hill, and found myself on the top of a dam, looking out over a lake. This is what I saw.

I knew instantly that this was the place. One of the things I knew I was going to miss was living near the ocean, which I had done all my life up until that point. A lake is not an ocean, but at least it’s water, and this was an especially nice lake. We loved it so much that two years later we bought a house a block away, and ultimately spent 6 years in Lake Braddock until we moved to Ormond Beach in 2001. But that’s a tale for another post….

Extraterrestrials

Where is everybody?

Legend has it that this is the question that Enrico Fermi asked when discussing the existence of alien civilizations. If, as we know now (but Fermi did not), there appear to be many planets forming many solar systems around stars in our Milky Way galaxy. And some fraction of those stars should be able to support life, and on some of those planets life actually emerges, why have none of those civilizations made contact AND remained in contact?

In 1975, Michael Hart made the case that the reason that "there are no intelligent beings from outer space on Earth now" is that there are none. He made some fairly good arguments, but his dismissal of the so-called "temporal explanation" seems the most dubious to me. The temporal explanations state that other civilizations have arisen so recently (or at least become capable of interstellar travel so recently) that they have not had time to reach Earth (assuming that that are colonizing the galaxy). Hart estimates that it would take a civilization (namely, humans) about 2 million years to colonize the galaxy. Since this is so much less than the age of the universe (~10 billion years), it seems unlikely that if other species existed they would not have visited us yet.

However, it is well known that life as we know it, based on carbon, needs elements other than hydrogen and helium to evolve. Since H and He were the only elements created in the big bang (this is an incredibly bad term, but I'll leave that to another post), stars are required to process H and He into heavier elements through nuclear fusion. Several stellar generations are needed, though, because the death of one start, via a supernova, for example, provides fuel for the start of another solar system. If stars are needed, then galaxies are needed, so that there are many stars around to feed on each other. Therefore, it is plausible that a certain minimum time is need for the primordial hydrogen and helium atoms to condense into galaxies, then stars, then have several generations needed to produce the stuff from which life is made. Exactly what this minimum time is is open to debate, but I think it's relatively well accepted that there is a minimum time. So that tells me that the temporal explanation might just be the right one.

But all this is to point out a recent paper in which the authors argue that it is still a good idea to look for extraterrestrials, and their idea is that we should look in the infra-red. If a civilization is advanced, they must use lots of energy, and will have lots of waste energy, and that will ultimately end up as radiation in the infrared region of the spectrum.

The G-hat infrared search for extraterrestrial civilizations with large energy supplies
Wright, et al.
arxiv:1408.1133

It's a brief review of the history of SETI. Well worth a read.

Embry-Riddle student at NRL

On my first day at NRL, I'm eating lunch in the cafeteria, when I hear, "Dr Reynolds?" It was Yishi Lee, a former undergraduate and masters student at ERAU. He had worked with me on a project concerning radiation in the low-earth-orbit (LEO) environment, and did his thesis with a space physicist titled "A 3D model of the auroral ionosphere." He was more interested in hands-on engineering work, so he's currently in the PhD program at the University of Denver, studying robotics.

Anyway, he got an internship to spend the summer at NRL working in their space robotics lab, and has been doing research on actuators that use shape memory materials, like nickel-titantium. Interestingly, there were a lot of talks on this subject at the PCMI workshop that I attended in Utah in July, because the mathematics describing these materials is quite interesting.

I also got a tour of their lab, and I saw their huge frictionless granite table, used for mimicking the frictionless space environment (although there's still gravity, at least it's force free in two dimensions). Unfortunately, the taking of photos is not allowed at NRL, so Yishi is going to send me an official photo of him and his work. I'll post that when I get it.

Drive to DC

Last weekend I drove from Daytona to Washington, DC, because I'll be spending the next two weeks working at the Naval Research Lab (NRL), working with my postdoc advisor, Guru Ganguli. NRL has a bucolic campus, nestled on the banks of the Potomac River, directly across the river from Washington National Airport.

Of course, it's right next to the Blue Plains Wastewater Treatment plant. And if the wind is blowing just right, look out!

I brought Sarah's Flat Stanley that she made 10 years ago, and hopefully he'll be photographed in more historic places than the Georgia state line. However, so far, the only place I've been in NRL, and I am not allowed to take photos at NRL, so he's be staying in the car.

My main improvement to the driving trip was to stop at every rest area. When I drive, or sit for long periods of time, my right leg tends to cramp up. So, to alleviate this, I decided to stop at every rest area and walk around for a few minutes. It worked! My leg was fine, and I think I only missed two rest areas. But I did stop at 14 rest areas in the 800 mile trip. So, if there really were 16, that's about one every 50 miles, which sounds about right.

Zometools

The theme of PCMI 2014 was the mathematics of materials. Normally, it's a more "mathy" topic, like algebraic geometry, or Lie groups. But this year there were a lot of physicists, chemists, and engineers in attendance, which allowed me to understand more than I would have!

One of the subjects was the geometric structure of solids and crystals, and quasicrystals. People were studying how different shapes fit together (in both 2D and 3D). There was a lot of talk about the 5 Platonic solids, the cube, tetrahedron, octahedron, dodecahedron, and icosahedron. To help the students (and me!) visualize these structures, we had Zometools on hand, which are basically very fancy tinker-toys. I was able to bring some home, and here are a dodecahedron and icosahedron that I built using Zometools.

Notice that the dodecahedron has 12 (regular pentagon) faces, 30 edges, and 20 vertices, and 3 edges meet at each vertex. And the icosahedron has 20 (regular triangle) faces, 30 edges, and 12 vertices, and 5 edges meet at each vertex. These are called "dual" polyhedra. This is because if you take one of them and place a vertex at the center of each face and then connect those vertices with edges, you will obtain the other polyhedron!

This can be demonstrated mathematically by looking at something called Euler's formula (or the Euler characteristic):

F + V - E = 2

where F is the number of faces, V is the number of vertices, and E is the number of edges. This equality holds true for all polyhedra, not just regular polyhedra. (Well, there is one important restriction: the polyhedron must be "homeomorphic to the sphere," which basically means that it is concave, and has no parts sticking out.) For our two polyhedra above, they each have the same number of edges E, but switch F and V. This is what "dual" means, switching the roles of the faces and the vertices.

This simple formula is easy to prove. It is so easy to prove that there are (at least) 20 different ways to prove it! A very simple proof is on the Wikipedia page "Euler characteristic".

What about those Zometools? They consist of struts and nodes, and they are all shape-identified. The nodes are "universal" in that they have many different holes in which to place the strut ends, but they are all of different shapes (triangles, rectangles, pentagons) so that only one type of strut will fit in any given hole. This allows you (or forces you) to be able to make certain shapes quite easily. The blue struts have rectangular ends, and the red struts have pentagonal ends. I don't have any of the struts with triangular ends. There are also struts of different lengths.

Zometools are extremely fun to play with, and can be very addicting! And they are useful for researchers. In fact, they were used to develop some of the theory behind quasicrystals, for which Dan Shechtman won a Nobel Prize in Chemistry in 2011.

Radiation and Mars

Even though I'm on sabbatical and focusing on my own research (more on this later), I still read and keep up with developments in physics and physics teaching. One of my interests is radiation and its effects on humans, and how it might block our plans to colonize the solar system (or at least send humans to Mars). Mars One is an organization that is planning to send humans to Mars in the foreseeable future, but first they want to send an unmanned mission in 2018 (and well they should). A colleague of mine at Embry-Riddle Aeronautical University is submitting a proposal for an experiment that will measure the effects of radiation on flies during the trip to Mars. I believe that this is fundamentally the one issue (among all the problems that we need to solve in order to live in space) that will effectively stop us from leaving Earth permanently.

While we're on the surface, there are two factors that protect us from the particle radiation (mostly protons and electrons) that bombard the earth constantly from space: the Earth's atmosphere and magnetic field. The magnetic field deflects the charged particles, except near the poles, and the atmosphere effectively absorbs them. However, there are a few that make it through, and these are thought to cause some of the mutations that are responsible for evolution. The ISS is above most of the atmosphere, but still within the protective magnetic shell, so while astronauts have more exposure than humans on Earth, it is unlikely that the radiation (for the short time they are in space) contributed to any subsequent cancer.

Once you are away from the Earth's magnetic field, say above 100,000 km altitude, humans are fully exposed, and there is no current spacecraft who's walls are thick enough to block this radiation. Eugene Parker has a nice Scientific American article "Shielding Space Travelers," in the March 2006 issue, that describes the problem nicely. It is estimated that each year in 'outer space' is responsible for a 10% increase in the risk of cancer, and a 5% increase in the risk of a fatal cancer. A trip to Mars and back would take 3 years minimum, without any stay on the surface. And going further, say to the nearest star - Proxima Centauri - would mean a lifetime. 20 years in space would probably guarantee your death of cancer. Lifetimes would be extremely short. Of course, once on the surface of Mars (which has no significant magnetic field or atmosphere), protective structures could be built. But any humans that permanently lived there would be confined to the interior of these structures. A very different life.

The motivation for these thoughts is a recent article in The Physics Teacher, called "Three Misconceptions About Radiation" by Susanne Neumann from the University of Vienna. Her list is

1. Radiation is artificial
2. Radiation is harmful
3. Radiation is invisible

Everything is radioactive to some degree, even the water we drink, and simply walking around with a Geiger counter proves that. Radiation is not just linked to our advanced technology. Too much radiation can be harmful, but the necessity of radiation for evolution should not be overlooked. While protons and electrons are "invisible," and other radiation, like IR and UV, is also invisible. But light is a form of radiation, and is in fact, just like IR and UV, but with a different wavelength.

So consider this post as my attempt to inform you about radiation, and to motivate you to learn more.

Catching Up

Since I've got a year's sabbatical ahead of me, and hopefully some good adventures, it's been suggested to me that I keep a blog (or a weblog for those true believers). However, since I'm a few months into my sabbatical, and I've already been to Utah, Iowa, Wisconsin, and Illinois, I thought I'd better let my first few posts catch up to the present.

In July, I spent 3 weeks in Park City, Utah, at PCMI, the Park City Mathematics Institute, a workshop for high school students, high school teacher, undergrads, graduate students, undergraduate faculty, and researchers. The lecture hall was great, with not only a projection screen, but 5 (count 'em) rolling blackboards that were well used.  I learned lots of good mathematics there (more in future posts), and also got a chance to do some hiking and traveling.

The first weekend we went to Arches National Park ...

... and Canyonlands National Park ...

Unfortunately, it was a quick trip, less than 24 hours. It's about a 4-hour drive from Park City, and since we had trouble finding a rental car on July 4 weekend, we didn't leave until about 11:00am on Saturday, which meant that we arrived at Arches late afternoon. A blessing in disguise, though, as the high temperature was 100 F that day, so we missed that. Then we left before noon on Sunday, after visiting Canyonlands in the morning. It was going to be hot that day, too.

Well worth the trip, though I'd like to return in the autumn, winter, or spring. Anytime but summer.