40 Years Ago
Published on Jul 16, 2009 at 9:38 am.
1 Comment.
Filed under NASA, history, space exploration.
40 years ago today a giant Saturn V rocket lifted off from the Kennedy Space Center on a trip of a lifetime. The astronauts were going to the Moon. The Saturn V rocket was an amazing piece of equipment. It was the largest rocket that was ever built (the Soviets had tried to build one similar in size, but it was not successful). I’ve already written about the Apollo 11 mission, so you can go look at that post for more information.
I didn’t want such a historic day to go by, though, without at least mentioning it. I remember watching the whole mission on TV. School was not in session, so I was home, and I was glued to the television anytime anything significant was going on. Naturally, there was nearly continual coverage of the mission. It is hard to put into words how significant this mission was in the history of human exploration.
The Apollo 11 mission itself was largely a full blown test of the Apollo systems. It demonstrated that we had the ability to get to the Moon, land, take off, and safely return to Earth. I use the term “safety” here, recognizing that the entire operation was really quite risky, and would likely not have been undertaken in today’s climate of intolerance to risk. But, in the 1960s, people were a bit more willing to allow NASA and the astronauts to take some risks.
But, as I said, the Apollo 11 mission was primarily a test of the systems. Yes, some science was done, and some instruments were left on the surface of the Moon. But, very little time was spent on the lunar surface compared with the later missions (about 2.5 hours). Some samples from the surface were collected, but nowhere near as many as on later missions. This was primarily a proof of the technology, and more extensive lunar surface exploration was done in later missions.
One of Apollo 11’s surface science experiments, the Lunar Laser Ranging Experiment is still in operation. It consists of a set of corner reflectors that lasers from Earth can reflect off of to make very accurate measurements of the Moon’s distance from Earth. Even today, these reflectors remain and lasers sometimes still are used to make these measurements.
-Astroprof
Image courtesy NASA
Red Moon
Published on Jul 12, 2009 at 2:50 pm.
No Comments.
Filed under books, science fiction.
I’ve been very busy with extra projects at the college the last couple of weeks. However, I try to wind down at bed time by reading a chapter or two from a novel. The latest one has been Red Moon, by Michael Cassutt. Like the last book that I reviewed here, this one is a well researched and realistic novel.
The novel is written as if it is an interview by the author of a certain Russian engineer named Yuri Ribko. The author writes as if he is transcribing Ribko’s tale, sort of ghost writing Ribko’s autobiography. The story is set in the Soviet Union in the decades marking the height of the space race. Ribko is an engineering student who manages to get a job at Sergei Korolev’s bureau, the organization that built the rockets and spacecraft that competed with the United States’ NASA. Ribko tells of the political intrigue and difficulties facing the Soviet rocket scientists as they tried to work amidst the bureacratic nightmare of the Soviet Union to compete with the Americans.
The author has clearly researched the Soviet space program, and that lends realism to the events that he portrays. But, this is a novel, as is clear in the author’s acknowledgments. Ribko, his family, and the events surrounding them are fiction. Still, the story is well written and sounds authentic. In the novel, we find that Korolev was murdered, and the aircraft crash that killed Yuri Gagarin was the result of sabotage. The author then contends that many of the Soviet’s missteps that allowed Apollo to beat the Soviet Union to the Moon were the result of sabotage. I personally do not think that to be the case, but the novel is so well written and plausible sounding that I suppose it can cause those who are enthralled by conspiracy theories to accept the premise. But, this is a work of fiction.
Given that it is a fictional work that is intertwined with science and technology, I’m going to claim it for science fiction in my tags for this post. I really enjoyed the book, and I think that anyone who has any interest at all in the history of the space race would find it very entertaining and interesting. Cassutt, the author, has written a very well researched book, and he has set his characters among very real events that happened. I find such historical novels very interesting if well done, as is the case with this one.
-Astroprof
Interesting book by Joven
Published on Jul 5, 2009 at 10:29 pm.
2 Comments.
Filed under books, science fiction.
A week or so ago, Byrd was at the library with her niece and brought home a book that was on the new rack. It was called The Book of God and Physics, by Enrique Joven. At first, I thought that it might be a book about reconciling science and religion. Instead, though, it is a novel. It is really a mystery, but since it is a fictional work that makes references to science, I’ll claim it for science fiction. 
The book was originally published in Spanish as El castillo de las estrellas and was translated into Englishby Dolores Koch. The science in the book is mostly astronomy, particulary the history of astronomy, and it is quite good. That is not surprising, the author, Enrique Joven is an astrophysicist at the Instituto do Astrofisicia de Canarias.
The story is told in first person form from the view of a Jesuit priest who teaches at a school in Spain. On the side, he is doing research into the Voynich manuscript, a mysterious book that passed through the hands of Rudolf II, the Holy Roman Emperor who employed Tycho Brahe and Johannes Kepler. The Voynich manuscript is written in an unknown lanquage, illustrated with odd plants, stars, people, and buildings. It has never been translated. The Wikipedia page for the manuscript shows a lot more activity over the last year, likely coinciding with the publication of this book. I will admit that I had never heard of the work until I read this book, but Joven writes about the lead character looking up information about the manuscript on the internet, so Iwondered just what I might find if I did just that. It looks like the thing actually exits.
The lead character in the book continues his research into the manuscript along with two colleagues that he has met online. The novel turns into a fascinating historical mystery as the investigators try to find out who actually wrote the work, and how it passed from hand to hand to get to the present. Clues keep pointing back to Johannes Kepler as perhaps having devised a code to translate the work, or part of it. In the novel, the book passes from Kepler to the hands of the Jesuits, who split the bulk of the text from the cipher key. I guess that is how the “God” part of the title got there. The key gets lost in history, and the investigators try to find it. But, there are others interested in finding the missing key who have their own motives, and they are willing to do almost anything to get it.
Once I got into the book, it was very interesting and was hard to put down. It was a very good read. However, it is a work of fiction. There are quite a few historical facts in the book, and many of the historical figures mentioned are real. But, I am sure that there are also a number of so-called facts put into the book as historical speculations in order to make the story flow. So, the book is a fun read, but don’t take it as a history text! Just enjoy it and take it for what it is: a very well written novel. I really liked it. So, if you get a chance, you might want to check it out.
-Astroprof
Aphelion, 2009
Published on Jul 4, 2009 at 1:17 pm.
1 Comment.
Filed under astronomy, physics.
Last night, Earth reached the farthest point in its orbit from the Sun. This distance is called the aphelion of Earth’s orbit. The exact distance varies a bit from year to year due to perturbations in Earth’s orbit from the other planets, but it doesn’t vary by very much. We were just under 152,100,000 kilometers from the Sun at about 02:00 UT. That was about 9pm last night, according to the clock here in Texas. This is in the heat of summer for us in Texas. It is hot today. The high the last few days had been about 103° F (39.4° C). Factoring in the humidity, and it is pretty uncomfortable out.
In school, most people hear that the Earth’s orbit is a bit elliptical. Our educational system does a pretty good job of explaining that. However, for whatever reason, people tend not to learn why we have seasons. When I ask my students why we have seasons, a great many seem to feel that we are hot in the summer because we are closer to the Sun then. That isn’t so for us in the Northern Hemisphere. In fact, we were closest to the Sun this year on January 4, when we were just under 147, 100,000 kilometers from the Sun. We call the closest distance to the Sun perihelion. That was when we were near our coldest around here! You can then show the students that the tilt of the Earth is why we have seasons. The Earth’s axis tilts about 23.5° from the axis of its orbit. During part of the year, one hemisphere is tilted more towards the Sun than the other. That hemisphere gets more direct sunlight, so it is warmer. All too often, though, students don’t completely give up their misconceptions about why we have seasons. They suppose that the tilt brings one hemisphere closer to the Sun than the other. While the tilt does make one hemisphere slightly closer to the Sun than the other, on average, the effect is rather small. Most people live in the temperate zones. Putting a few numbers into a back-of-the-envelope type calculation, that means that the tilt of the Earth has no more than about 1500 kilometers of motion for most people. While that sounds like a lot compared with the size of many familiar distances, it is vary tiny compared with the 2,500,000 back and forth from the average that the Earth’s orbital motion makes. So, it is not the distance that makes for the seasons, but rather the solar illumination. The more direct and the longer the duration of sunlight, the warmer that it gets.
But, wouldn’t the difference in distance between Earth and the Sun in January and July have any effect? Shouldn’t that make the Southern Hemisphere’s summer hotter and winter colder? It would seem that way at first glance. But, let’s put some numbers into the calculator and see what happens. When you look at the math, Earth’s orbit is actually pretty circular. The aphelion distance is, in fact, farther from the Sun. But, at Earth’s distance, that is only about 3.4% farther at apehelion than at perihelion. But light intensity from the Sun drops off as the distance squared, so that extra distance does result in a bit less solar power reaching Earth, about 6.5% less, when you do more back-of-the-envelope math. So, it looks like it really should be warmer in the southern summer and colder in the southern winter compared with those of us in the northern hemisphere. However, things are a bit more complicated than that.
One of the most important differences in the northern and southern hemispheres is the distribution of land mass. Earth’s continents and oceans are not equally distributed around the planet. The northern hemisphere has a disproportionate percentage of land compared with the southern hemisphere. Likewise, the southern hemisphere has a disproportionate percentage of ocean. This is particularly apparent at the mid temperate latitudes, where the effect of the seasons is most pronounced. So, how does this have any effect on things?
Water tends to reflect more light than land. In fact, when light strikes water at an angle of about 53° or more from perpendicular, then at least half of the light is reflected. Even when light strikes the surface at less than this angle from perpendicular some light is reflected. Smooth water can act almost like a mirror. Now, some light is also reflected from land, but normally not nearly so much. That means that more sunlight can be absorbed in the Northern Hemisphere than in the Southern Hemisphere. That warms causes the temperature of the ground to rise. Furthermore, water has a very high specific heat — much higher than the minerals that make up rocks. The temperature increase due to a certain amount of heat energy absorbed is inversely proportional to the specific heat of the body absorbing the heat. There is a lot of water in the Southern Hemisphere, so all that water takes far more heat to make it rise in temperature than does the land in the Northern Hemisphere. It also means that the water in the Southern Hemisphere can give up more heat at night than the land and so it doesn’t cool as fast. Putting all this together, it means that the Southern Hemisphere summer and winter temperatures are moderated somewhat compared with those of the Northern Hemisphere, even though the Southern Hemisphere gets slightly more solar heating in the summer and slightly less solar heating in the winter compared with the Northern Hemisphere. And, if that isn’t enough, the elliptical nature of Earth’s orbit makes it speed up and slow down as it goes around the Sun. That makes it take longer to go through the part of the orbit in July than in January. The cumulative effect of all this is so extensive, in fact, that the Earth’s average surface temperature is actually warmer in July and August than in January and February, even though Earth is farther from the Sun in July and August! You can see this effect in the following graphic produced using a tool at NASA’s Earth Science Office’s web site:
Click on the image to make it bigger and easier to see. Each color represents data from a particular year. Note that in all years, the peak appears typically in late July (give or take a little).
So, that is the astronomy lesson for the day, the way I’d explain it to my students.
-Astroprof
CoS 108
Published on Jun 26, 2009 at 11:20 am.
2 Comments.
Filed under blogging.
I’ve been busy with summer school and other faculty duties, so I’ve gotten behind in blogging. I am doing a star party tomorrow ( June 27) at Dinosaur Valley State Park. It’s going to be a hot one (temperature wise, with highs over 100 predicted). If you want to read blog entries, though, for the past week, then go over to Starts With a Bang blog, where the 108th edition of the Carnival of Space.
-Astroprof
KAGUYA’s last images
Published on Jun 20, 2009 at 3:36 pm.
No Comments.
Filed under moon, space exploration.
Japan’s KAGUYA (formerly SELENE) probe crashed into the surface of the Moon as planned this past week. Like many space probes to the Moon, the last action commanded from Earth was to crash into the Moon. This is in part a safety move to make sure that the dead spacecraft does not pose a hazard to any later lunar missions. However, it is also an opportunity to scrape one last bit of scientific data from the spacecraft. The spacecraft crashed into the Moon very near the Moon’s south pole. This is a very important and very poorly studied region of the Moon. The dynamics of orbits means that it is easiest to send a spacecraft from Earth to orbit the Moon nearer the Moon’s equator. Polar orbits are tougher. So, the Moon’s polar regions have been the least studied. Yet, there is reason to suspect that comet impacts on the Moon may have temporarily enshrouded the Moon in water vapor over the history of that body. The floors of deep craters in the Moon’s polar regions might never see sunlight. Thus, those crater floors would be cold — very cold. Any water vapor drifting into those craters would freeze to the surfaces there. In the lab, I’ve used devices called cold traps in vacuum systems. These traps are simply metal plates that are in thermal contact with a reservoir of liquid nitrogen (or some other cryogenic substance). Though the pressure in the vacuum system is near zero, there is always a little gas left. As the gas molecules in the system (water vapor, grease outgasing, residual atmosphere, etc) contact the metal plates, they tend to stick. The pressure in the system drops as more gas is removed by the cold traps. A very similar thing may happen in the craters in the Moon’s polar regions. At least, that is the theory.
I remember being at a conference when the radar data from the Clementine mission suggested that perhaps some of that water ice had been found in the lunar polar craters. Then, over a year later, it hit the public airwaves, with news reporters suddenly jumping on the news. There was a special Nightline segment on the discovery of lunar polar ice. My students were sort of dumbfounded, asking me what all the news was about. After all, didn’t I just tell them the same thing earlier in the semester? Hmm. But, the news media went a bit overboard, in my estimation. They made the ice deposits out to be giant lakes of ice. Sadly, some astronomers jumped on the same bandwagon. Then, there was talk of the giant lakes of ice being reservoirs of water that would support moonbases and colonies.
Now, I can’t say for certain that there are not giant lakes of ice in those craters. However, that is not how I envision any ice there. For one thing, more rocky meteors that icy comets likely hit the Moon. Even the comets are not composed 100% of ice! The Moon itself is a rocky body, and anything big hitting the lunar surface fast enough will pulverize the ground and send rocky debris everywhere. There will be a lot more dust and dirt tossed around than just water vapor. So, I’d imagine that the water vapor drifting into the craters might result in some sort of deposit like a thin frost at best. Now, if all that happened was that the frost was added to over the years, then you might wind up with a lake of ice. But, what about all of the other dust and rocky debris? That gets tossed into the craters, too. And smaller meteorites slam into the craters and churn up the surface, volatilizing some ice and burying nearby ice with dust. So, I always thought of the ice in those craters to be a mixture of ice and dust, more like permafrost than like a frozen lake. Granted, this is not my field of expertise, so I could be wrong on this.
Since the Clementine data, several spacecraft have slammed into the Moon. None have kicked up measurable levels of water. KAGUYA is the latest to run into the lunar surface, and we’ll have to wait to see the data collected by astronomers studying the ejecta of the impact. So far, though, the results are consistent with what I would expect. It would be exciting to find pools of frozen water on the Moon, but I really don’t expect that to happen.
But, as KAGUYA plunged to its end, it was busy sending back images of the lunar surface. I’ve reproduced a few of them here for you (one at the top of the post, and the rest below). These are very high resolution images — some of the best showing the lunar surface from a spacecraft. They show a rugged and foreboding terrain. The impact site was in the shadow, so the last few images are mostly black, with just the tips of crater ridges and mountains lit by the Sun. This is typical of the terrain that I have seen from this part of the Moon. Even if there are giant pools of frozen water in these craters, it would be very difficult to reach the ice. Landing a manned craft on the Moon is tough enough under the best of circumstances. Landing in this terrain would be very difficult. There are very few flat and level places to land. Even a lunar surface vehicle would have a tough time making it across this terrain. So, I am not so sure that a moonbase or lunar colony would really be able to get to any ice deposits here (at least not with our current level of technology).
Though these were the last images sent back by KAGUYA, they are very important. This part of the Moon seriously needs more research, so planetary geologists will be pouring over these images looking for clues to the nature of the Moon’s surface in this area. I am looking forward to hearing their findings.
-Astroprof
Images courtesy JAXA/NHK
CoS 107
Published on Jun 14, 2009 at 1:53 pm.
No Comments.
Filed under blogging.
The 107th edition of the Carnival of Space is now live over at Innumerarble Worlds blog. Go over there and check out the collected entries from the space blogosphere. My very busy academic year continues with heavy summer teaching load.
-Astroprof
