SAS E-Bulletin-- Week of August 10, 2001
compiled and edited by Shawn Carlson
Link to Last Week's E-Bulletin
ANNOUNCING NEW MEMBERSHIP BENEFITS
News flash: Tinkers Guild has just released The Amateur Astronomer on CD-ROM and SAS members can get their copies of the first edition for 25% off the retail price. Also, we've added three of the greatest citizen science magazines available to our list of discount subscriptions. Now your membership is more valuable then ever! Details follow.
| Twenty five percent off The Amateur Astronomer collection on CD-ROM. NEW RELEASE! Every astronomy related column from the acclaimed "The Amateur Scientist" column plus thousands of additional pages of observation techniques, telescope construction tips, and stunning photographs. With more than 500 astronomy projects, this is the most complete resource for citizen astronomers ever assembled! You'll receive the complete astronomy columns of Albert Ingalls, C.L. Stong, Jearl Walker, Forrest Mims and Shawn Carlson. Runs on Windows, Mac, Unix and Linux. Retail Price $60. SAS Member price just $44.95 (Save 25%) |
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| Natural History Magazine: This is the best magazine for the natural history buff ever published! Published by the world-famous American Museum of Natural History, you'll get one year of Natural History (10 issues). And if you can visit the museum your subscription also entities you to one-time free general admission pass to the Museum, discount on an IMAX® show during your visit, plus discounts on purchases in Museum shops. Newsstand rate is $40 per year. Discount subscription rate is $23. SAS Member rate is just $19.95. (Sorry, only members living in the US can take advantage of this offer.) |  |
| Popular Science: Great popular articles that keep you on the leading edge of science and technology. Newsstand price $47.88. Subscription price: $24.00 SAS Member price is just $13.95 (Sorry, only members living in the US can take advantage of this offer.) |  |
| Discover Magazine: A great magazine dedicated to keeping you informed about the latest happenings in science and technology. Newsstand price: $40 per year. Subscription rate: $25. Special SAS Member rate is just $19.95 (Sorry, only members living in the US can take advantage of this offer.) |  |
If you'd like to purchase The Amateur Astronomer CD-ROM, you can do so directly through the SAS On-Line Store. To take advantage of any of these great savings on the magazines, just send email to Nancy (don't forget to include your name, address and your precisely specified wants) and tell her what you need. And don't forget, you are still entitled to discount subscriptions to Scientific American, Popular Mechanics, and Explorations. For details about these services and about all of the benefits of your membership, please link to our Membership page.
NEWS FLASH: SAS Lowers Membership Rates for ALL International Members
It's true. The E-Bulletin has reduced the costs which we must bear to support foreign members and now we get to pass those savings on to you. So the Board of Directors has decided that starting with your next renewal, all international members will pay the same rate as domestic members.
What a great fringe benefit of living in the electronic age!
NEWS FLASH: Walter Alvarez Joins SAS's Board of Scientific and Technical Advisors
Walter Alvarez is one of the world's greatest and most well known scientists. In 1980, Walter and his father, Nobel Prize winning physicist Luis Alvarez, proposed that the dinosaurs were suddenly wiped out 65 million years ago when an asteroid impacted the earth. Today, the evidence overwhelmingly supports the Alvarez theory. Walter is a professor of geology at UC Berkeley, a member of the National Academy of Sciences and an all-around sweet guy. He's just proposed what I think is a great citizen geology project for SAS members, but this E-Bulletin was already too full of material related to the Perseids for the details to fit here. So look for all that next week!
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A science dynasty. Geologist Walter Alvarez (on right) with his father physicist Luis Alvarez at the clay layer demarking the KT boundary-- the geological disconformity that gave the critical clue to explaining what killed the dinosaurs. |
And speaking of Advisors, I've updated the list on the SAS Web page. If you take a look you'll see that we now have some of the greatest living scientists on tap to help make sure our citizen science projects remain at the cutting edge of research.
LAB NOTES
LN1: Random Number Generators
by Kevin Kilty
Random number generators are an essential tool in many scientific problems. For example, simulations involving random inputs, Monte Carlo methods, cryptography, and the evaluation of multi-dimensional integrals all make use of random numbers. In this series of Lab Notes I will examine random number generators, show how to obtain deviates with a designated distribution, and then present an example application that uses random numbers to examine an issue pertinent to global warming.
It is nowadays common to do very large simulations involving upwards of a billion events. This is especially so in computational fluid dynamics or in the simulation of semiconductor devices. A generator called upon to deliver billions of deviates (individual random values, or what statisticians call realizations) becomes a significant burden on the simulation program. Linear algorithms are fast and efficient, so they are a natural choice for large simulations. Such algorithms include the function rand() which is supplied with most C or C++ compilers. However, linear methods can exhibit undesirable characteristics. For example, linear methods are predictable, which makes their use in cryptography and gambling simulations inappropriate. No single random number generator is appropriate to all problems.
Two important characteristics of a random
number generator are its cycle length and normality. Linear generators
produce what appears to be a random sequence of numbers, but this
sequence eventually repeats. Borland advertised their implementation
of the C function rand() as having a cycle length of about 1E10
when supplied with a reasonable seed value. Microsoft does not
even provide an estimate of cycle length for their C/C++ implementation
in their documentation. However, a very poor choice of seed value,
passed to srand() to initiate the generator, might produce a cycle
length that is very short. Some generators IBM once supplied with
their compilers had cycle lengths of only 65,000 in the best of
circumstances. I have no idea how well the random number generators
used in spreadsheets, like Excel, perform. However, a simulation
using a million deviates made with such a
generator simply repeats the same deviates over 16 times. As a
result the statistics generated with the big simulation are no
better than those from a small simulation.
Random number generators supplied with compilers are usually designed to provide numbers uniformly distributed over some range, usually 0 to 1. A generator that truly supplies a sequence where each number appears with constant frequency is called normal (do not confuse this with the normal or Gaussian distribution). It is a fact that many generators are not normal. In particular some generators appear to be normal in the most significant digits of the deviates they supply, but are not normal in the less significant digits. In other words, when examined with a coarse division of classes their output appears normal, but a fine division will show that some ranges of numbers occur much more often than others.
Evaluating difficult integrals in many dimensions, such as those which occur in radiation heat transfer problems, requires a generator which provides random vectors, or, if you will, random points in space. Unfortunately many available generators exhibit a correlation from one point to another. Rather than filling an N-dimensional space with points, such generators tend to place points on planes. This is called the Marsaglia effect. A wonderful illustration of this is available as a JAVA applet.
I have used a fast linear algorithm over the past decade.
It has a cycle length of nearly 1E13. I do not recall its source,
and I confess that I have not fully explored its normality at
anything but a cursory level. All I have done is too make a coarse
division and verify that the deviates are distributed uniformly.
A good project for someone to pursue is to
fully characterize this algorithm. A generator that is extremely
normal and of long cycle, yet which is fast and efficient is tt800.
A very complete source of information on
random number generators is available at this web site.
LN2: Real Time Holography
by Ely Silk
When there is a need to observe slow changes induced by temperature, pressure, or other stresses, the experimenter will often employ real time holography. Typically, a holographic plate is exposed to the field being examined prior to any stress, processed, and then precisely replaced to allow examination of the field under stress. If the hologram is not processed in place (expensive!), the very real problem of replacing the plate in exactly the same position is encountered. In any event, the emulsion is often found to have shrunk or distorted. What is a scientist to do?
Photopolymers are one solution. On plates you prepare, a special coating develops as it is exposed to laser light illuminating the unstressed field. At the end of the exposure, the plate is blasted with a bright, white light to desensitize the remaining emulsion. You can then stress the field while viewing it through the hologram, which is still untouched by human hands. The visible results are shifting interferometric fringes revealing density, temperature, or pressure changes. Perfect for watching extremely slow motion or surface variations in real time!
If this interests you, start by getting hold of the following article: "Characterization of an acrylamide-based dry photopolymer holographic recording material," Opt. Engineering, V33(12), pp. 3942-3946 (Dec. 1994). If you plan to use a red light laser, substitute methylene blue for the dyes Dr. Suzanne Martin discusses in her paper. I suggest building a small chamber with leveling feet which draws in filtered air to accelerate the drying of the plates you prepare. Use the photopolymer plates as quickly as you can due to short shelf-life.
Photograph the shifting fringes for a permanent record. Once you get the hang of it, the process is remarkably easy and straightforward. With my 35 mw red diode laser, typical exposures were 2 - 5 minutes for 2" square plates. So, the next time you feel like just sitting around and watching mushrooms grow, you'll be able to!
OBSERVER'S NOTES
Perseid Meteor Shower is Coming!
August 11/12, 2000
The Perseid meteor shower is an annual pelting of our planet by pebbles and dust from the comet known as Swift-Tuttle.
The shower will be most active the night of Saturday, August 11 and the morning of Sunday, August 12. You may see a few early meteors before midnight, but you'll see many more in the hours just before dawn.
Like all astronomical events, the Perseid Meteor Shower is best viewed far from city lights-in the mountains or deserts. If you live in San Diego Country, (SAS's birthplace before the National Headquarters moved to Rhode Island) Mt. Laguna, Julian, Palomar Mountain, the Anza-Borrego Desert are all nearby dark-sky sites. To park anywhere in the Cleveland National Forest, however, you'll need $5.00 Wilderness Pass or risk a $100 fine. You can purchase one at the Laguna Mountain Lodge & Trading Post (619-473-8533). Those of you who live in other parts of the country will need to find your own dark skies.
Typically meteors appear all over the sky, and this shower is no exception. But the last quarter moon will be in the southern half of the sky after midnight. So your best bet will be to concentrate on the northern half of the sky.
Meteor showers are particularly delightful
for the beginning astronomer because you need only your eyes to
see them. Dress warmly, lie back on a lawn chair or sleeping
bag and watch the sky. Binoculars might help if you see a smoky
trail left by a long, bright meteor.
In a typical year, you might see 80-100 meteors per hour. This year you'll see fewer since the last quarter moon will wash out some of the fainter ones.
Meteors are actually fairly simple to photograph.
All you need is a camera capable of time exposures, a normal lens
(preferably f/2 or faster), fast color film (e.g., Ektachrome
P-1600 slide film), a tripod and a locking cable release. With
the lens open all the way,expose the film for five to thirty minutes.
When processed, your shots will show parallel star trails and,
if you're lucky, meteor streaks crossing the
trails.
You can find more information from the following Web sites.
Dennis Mamanna
Fleet Space Theater and Science Center Balboa Part, San Diego
Additional Notes on the Meteor Shower this Weekend.
PHOTOGRAPHY
Because the moon will be in its last quarter phase during this
year's shower, using a super fast film (e.g. 1600 ISO) may not
be a good idea. This fast film would overexpose very quickly under
the light of the moon. Instead, meteor experts recommend something
a bit slower (e.g. 200 or 400 ISO). I've had good luck with star
photographs using Kodak's EliteChrome 200 slide film-and it can
be "pushed" to 400 if you so desire. I can't speak to
its effectiveness with meteors, however.
Use a manual (or mechanical) camera; if
you have an automatic camera, it may become very confused at trying
to focus on and shoot something it cannot see! Aim the camera
toward the northern sky (away from the brightest moonlight), open
the lens all the way (or mostly), focus on infinity, and take
exposures of 5 minutes or so. If a very bright meteor falls through
your field of view during your exposure, you may capture it crossing
the star trails. Please disable your flash, since the a burst
of strobe light in the darkness will accomplish only getting others
in the area ticked off
at you!
MORE INFO FROM THE INTERNATIONAL METEOR
ORGANIZATION
The annual Perseid meteor shower will reach maximum activity Sunday
morning August 12. Like last year the moon will be in the sky
reducing the number of meteors seen. Last year there was an small
opportunity late in the morning to view the Perseids in a dark
sky once the moon set. Observers who watched during this period
remarked that the display was far richer than that seen in 1999
despite a bright aurora display. This year the moon free period
lies between dusk and moonrise on Saturday August 11. This time
will be approximately 9 pm local daylight time (2100) and midnight
depending on your location. At this time of night the Perseid
radiant, the area of the sky the meteors seem to come from, will
lie low in the northern sky. For the Southern Hemisphere and north
tropical areas it will actually be located
below the horizon and no activity can be seen from there until
later in the night. With the radiant lying so low in the sky from
north temperate areas the horizon will block a great majority
of the Perseid activity. The Perseids that do travel upwards will
just be skimming the upper regions of the atmosphere allowing
them to last several seconds and create a long streak across the
sky. These "earthgrazers" are exciting to see but are
only seen once or twice per hour.
As the night progresses the Perseid radiant will rise higher into
the northeastern sky. Those living in high northern latitudes
have the advantage of the radiant being located higher in their
sky. Unfortunately morning twilight will also arrive earlier for
them cutting short their show. North tropical and north temperate
latitudes are best suited to see the display with the lower radiant
altitudes being offset by a longer night as one proceeds southward.
As one approaches the equator the Perseid radiant does not rise
much higher than 30 degrees before morning twilight interferes.
This again limits the amount of activity seen. It gets worse as
one travels past the equator into the Southern Hemisphere. From
30 degrees south the radiant rises only 3 degrees high so the
best observers in Australia, South Africa, and southern South
America can expect is 2-3 Perseids per hour. What can mid northern
latitude observers expect to see this year? Since there will be
moonlight in the morning sky it definitely will not be as impressive
as the 2000 display. Activity will increase as the night progresses
as the radiant rises higher into the sky. The moon will rise around
midnight and will be located high in the southeastern sky during
the last dark hour before morning twilight. This last dark hour
before morning twilight (approximately 4 to 5am on August 12)
will offer the most activity. To offset the bright moonlight it
would be advisable to face away from the moon toward the north
or northwest. One should look high enough into the sky so that
the bottom of their field of view is not wasted on the ground.
This means that most people should view 60-70 degrees high (90
being straight up). In similar circumstances in 1982 I was able
to count up to 38 Perseids per hour from a rural observing site.
Those who watch from urban areas or experience hazy skies will
see less activity.
Meteor photography is also possible if you aim the camera far
away from the moon. Use slow to medium speed film such as ISO
100 to 400. A manual single lens reflex camera is necessary as
you need to keep the shutter open for 5-10 minutes. Aim the camera
so that the bottom of the frame lies just above the horizon. A
good direction to aim would be due north as the star trails are
least in this direction. The stars will show parallel paths on
your photo. Any meteor caught on film will cross these paths and
will be easy to find. A meteor must be as bright as the brightest
stars to be recorded on film. Even during the Perseids the rate
of success averages only 1 meteor per roll of 24 exposures. It's
all a matter of luck! Advanced meteor photographers often use
a motor driven mount to prevent the stars from trailing in their
photos. Therefore any streak on the photo could be a meteor or
a man-made satellite.
Sky & Telescope, the AMS, and the International
Meteor Organization are interested in your Perseid counts. The
basic information needed is your location, the time you watched,
the number of Perseids seen, the number of other meteors seen,
and the sky conditions (clouds, limiting magnitude). You may also
try to estimate the brightness of each meteor by comparing it
to stars of a known magnitude. Reports can be sent to me at: lunro.imo.usa@home.com
<mailto:lunro.imo.usa@home.com> and to Sky & Telescope
at: observers@skypub.com<mailto:observers@skypub.com>
A weekly preview of meteor activity is also
published each Thursday at:
http://www.amsmeteors.org/lunsford/
Clear Skies!
Robert Lunsford
Secretary General of the International Meteor Organization
Visual Meteor Program Coordinator of the American Meteor Society
A Member's Complaint about
Efston Science
I placed a large order with Efston Science in early May, but relieved
nothing for six weeks. I am convinced that the only reason I got
it at all is that I called them and twisted some arms. The first
part of the order, in all fairness, arrived on time and in good
condition only a couple weeks after the order. This was a Jensen
toolkit and it arrived from a company in Arizona. The rest of
it was a nightmare.
I ordered, for example, a wire inoculating loop; they no longer carried the model so they switched it with plastic. Plastic. Have you ever tried to sterilize a plastic inoculating loop in a fire? I ordered a 100 ml burette. They told me they no longer carry that model so I could buy a 50 ml burette for the same price or pay double for a 100 ml burette. I kindly told them about truth in advertising laws and they decided after much soul-searching to give me what I bought (since I had prepaid by bank card).
When ordering they requested that I fill out a form and fax it back to them. This was so that I could verify that I was the card holder and not some thief. I do a lot of ordering online and the reason for allowing bank cards is to avoid such paperwork and hassle. I called them to cancel the order, at which time they told me that they could just call the bank themselves, they didn't need the fax. Just yesterday they informed me that one of the reasons the order took so long is that they had to verify my address with the bank. Ten weeks?
Perhaps someone else might have a better
experience with this company. Once they shipped the order it arrived
in good order, nothing broken. Two things alarm me about the company:
1) They tend to substitute order items without permission if something
is not in stock.
2) They do not own up to their mistakes when confronted, they
always blame someone else.
George Hrabovsky
Based on George's experience, and a few
other complaints we've received, I have removed to link the Efston
Science from our site. SC.
Feedback
More on SAS Non-Support of Amateur Cosmology
Hi Shawn!
Just wanted to respond to the comments about the stance on theory
in SAS. I want people to realize that SAS supports all areas of
amateur science where an amateur can reasonable expect to contribute.
This is mostly experimental since you have the apparatus you build
right there in front of you; measurements can be taken, errors
accounted for and factored in for analysis of results and the
like. Theory is a lot harder in one respect and easier in another.
It is harder to become good a theory since it requires an extensive
background in both mathematics and the subject area you are interested
in. The mathematics is required for both computational purposes
and the discipline it brings in proving that your ideas are logically
self-consistent. It is easier in that you need very little money
to pursue theory (at a minimum you will need pencil. paper, and
a couple of reference books).
I believe that all experementalists should have at least a passing
familiarity with theoretical work. Without theory experiments
can be thought of a flailing about without a purpose. Think about
it. Every experiment has a purpose. It tries to demonstrate the
validity of an idea. That underlying idea is theory.
Can amateur scientists really contribute to cutting edge theory?
Not without vast amounts of work. The people who do work in theoretical
cosmology have put years of their lives into the required studies.
Quantum gravity is one of my areas of research. I do not seriously
believe that I will ever solve the problem of quantum gravity.
I have put thirty years of work into studying mathematics and
physics to reach the level of proficiency that I have. It is not
something you can do in a couple of years. It is not something
you can do without graduate level mathematics and physics. If
I ever solved the problem of quantum gravity, and I mean no offense
to Shawn or anyone else in SAS, the last place I would publish
the results would be in the Bulletin:-) I believe strongly that
there are many interesting problems in every science that can
be addressed by amateur theorists. We do not understand the theory
behind even relatively simple fluid flow, we do not understand
the basic dynamics of simple chaotic systems, there are many open
problems that can be addressed by even a modest level of mathematical
ability (these can be within the grasp of anyone willing to put
a few months of effort into developing the mathematical tools).
The nice thing about developing math skills is that you can then
use the experience gained in future work.
To sum it up: I do not believe that an amateur will solve quantum
gravity or inflationary cosmology or the mystery of life in the
universe. I do think that there is ample opportunity for amateurs
to contribute to theoretical work, and that there are very rich
and rewarding projects to be done in this area. I look forward
to working with people who are willing to do the necessary background
work to become amateur theorists.
George
E. Hrabovsky
President, MAST and Accredited Mathematica Consultant (my only
credentials :-) )
The Search for F.B. Lee
Dear SAS,
I am glad to hear that Mr. Lee is still with us! His articles live in a special place in my heart. As a 7th grader (~1975) I discovered the "Amateur Scientist" book in the school library and was immediately drawn to the linear accelerator and electrostatics articles. I think I re-read those articles weekly for a year! I had forgotten his name until the summer of 1998 when his daughter showed up at a Tesla coil related gathering held in Rochester N.Y. to sell spun aluminum toroids in the small flee market.
It would be wonderful if you can establish a partnership with SF if only for access to the spun aluminum products (which are about as common as Condor eggs in this day and age).
Take Care
Zone Purification and Map
Sweet things continue to pour from my Lab Note about Zone Purification in the July 27 E-Bulletin. Last week in response to Jim Hannon's comments re. maple syrup I noted that concentrated sugar solutions like honey and maple syrup generally make poor growth media. Jim's found an excellent Web site that discusses the production of maple syrup. Our exchange also prompted the excellent notes below from Jerry Kram and Capt. Robert Gholsom
=
Shawn,
I have also heard that above a certain concentration of sugar
mold is not supposed to grow. However I also have had it get moldy,
at least the store bought stuff. By the way the unit of measure
for sugar concentration is Brix. Here is a web
site with some information about mold, Brix and flavor of
maple syrup.
[Jim's reference asserts that the traditional maple taste is created by boiling and if that's true then experiments with zone purification and vacuum evaporation are likely to yield unsatisfying results. But, it's a matter best left to empirical observation, I think. SC]
=
Shawn,
The preserving powers of concentrated sugar solutions, such as maple syrup and honey, have long been noted in both folklore and science. The primary mechanism for preventing microbial growth is osmotic pressure. A concentrated sugar solution draws water out of anything placed in it. Microorganisms are killed by dehydration or go into a dormant phase. (Botulism cysts in honey can cause illness in infants, for example.)
The same mechanism explains the use of salt as a preservative. As you noted, there are a few spoilage organisms, primarily molds, that can live in solutions with a high osmotic pressure, but they uncommon enough to make sugaring/salting useful preservation techniques.
Jerry W.
Kram
jwkram@mac.com
Dickinson, North Dakota
==
Good morning, Shawn,
I wanted to add a note on microorganisms
in honey. Spore-forming bacteria, if present in an environment
which isn't conducive to their growth, will form very hardy spores
until conditions are acceptable. Clostridium botulinum, the causative
agent of botulism, is just one bacterial species which can do
this, but is of particular concern because of its ubiquitousness
and the potency of the toxin it produces. Clostridial
spores, and probably those of other spore-forming bacteria, can
be recovered from honey. I'm not sure about maple syrup, but I
would assume it is also likely to be contaminated.
Most of us probably think of getting botulism in association with eating food contaminated with the pre-formed toxin, as in the classic home canning scenarios. The form of botulism I wanted to address is infant botulism, which is actually the most common form of human botulism in the United States (usually between 70-75% of the 100 or so U.S. cases which occur every year). It usually occurs in infants who are less than one year old, but can also occur in adults whose GI flora has been disturbed (surgery, antibiotics, etc). Infants are susceptible because they do not have a "mature" GI flora - they ingest the spores, which sporulate into reproducing bacteria which do not have much intragut competition and colonize the baby's intestinal tract. They then produce the toxin which is absorbed by the child. The good news is that if recognized, the infant fatality rate is less than 1%. Bottom line is that although honey may not be a good bacterial growth medium, it shouldn't be given to infants less than 12 months of age, and would recommend the same precautions for uncooked syrup.
Web Site Accessibility
Shawn,
I think some attention should be paid to making the SAS site accessible
to people with disabilities. There are all sorts of tools to aid
in this process but there has to be a will to do so. Examples
include Bobby, InSight 508, and Macromedia's "Check Page
For Accessibility" extension for Dreamweaver.
Response: A great point and an excellent suggestion. However, SAS is at a very critical phase right now and, unfortunately, no one here in the home office has the time to carry this through. So if one of our members would like to volunteer to take this on, let me know . It would be a great way to give back to the community. In the meantime, I want all of our members to understand that SAS is committed to doing what we can to make our Web site accessible to everyone.
Shawn
Featured Products
Glassware: This week I've added yet still more glassware including petri dishes, serological pipettes, culture tubes, well... you get the picture. Check out the huge and growing assortment of amazing glassware at 50 percent off bulk prices!
Books: New this week is The Art of Science by Joseph Carr, one of the best intro texts for the citizen scientist I've ever seen. You'll find this, and a host of other offerings through our Book link.