The Galilean Cannon

Editor,

I stumbled upon your site while looking for info about the "Galilean Cannon." I had read an article about it in Scientific American many years ago, perhaps in "The Amateur Scientist" department. (I realize Scientific American is probably not your favorite topic, and understandably so!)

Can you possibly send me any specifics about the"Galilean Cannon"? It's been a few decades since I read about it.

I have no formal degree but worked independently in 3D optical holography in Palo Alto and Santa Clara for a many years.

My mentor back then was retired IBM fellow "Rey" Johnson. I worked at many Silicon Valley firms (1960s-90s) which, along with my Stanford Technical Library card, provided my science education.

I presently make 3D lenticular images some of which can be viewed on my website www.3dpostersdirect.com. (The 3D picture of the old guy is me.) You might find them interesting. Much of my early lenticular background was though Jerry Nims' group in Duluth.

My primary interests are in science and visual arts, which I consider to be the same thing. I use computers for both now.

Your organization is very exciting. Science should be openly available to ordinary citizens, not restricted to the elite.

Hope to hear back from you.

Vic G. Rice

Thanks for writing. Writing for Scientific American led to my career doing science. You can find information about the Galilean Cannon on the web. Here's a short item from The Citizen Scientist about an article I edited for Science Probe!:

"In the July 1992 issue of Science Probe!, Alexander K. Dewdney, made mention of a device called a Galilean Cannon. RedNova Science Toys sells a model of the cannon called the Astro-Blaster for $4.95 US. Basically, he stated that if ball #1 struck the floor with a velocity of 1v, then ball #2 will rebound with the velocity of 3v, ball #3 with 7v and ball #4 with 15v and so on as more balls are added."

The RedNova product couldn't be found in a web search. Readers, can you help? Editor.

Dirty Snow

Editor,

I was somewhat astonished to read that it was only recently discovered that soot or dirt might accelerate snow melting [Dirty Snow, The Citizen Scientist, February 2008]. As I mentioned in my last letter I spent a year in Milwaukee in 1953/4. Arriving from what was then sooty Britain, I was amazed at the bright blue winter skies and the pristine white snow. One important thing that was clear to anyone who looked was that the slightest speck of dirt on the snow ( e.g., from splashes caused by passing cars) produced spires and peaks in alignment with the sun as the discolored snow melted.

When I arrived in Canada in1957 and lived in Montreal for nine years, the same observations could be seen. On moving to Toronto in1966 it was very noticeable that the hazy air over Toronto eliminated what had been easily observed in Milwaukee and Montreal.

I must say that when I commented to local folks about the way snow behaved during bright, clear, sunny days, they thought that was just normal. They were not aware what dirty air did by scattering the light. (Note that some black and white photographers were aware, because they liked the reduced contrast that film speeds of those days could not handle.)

The condition of the sky has concerned me ever since that trip to Milwaukee. As a result, I made a haze meter after I saw the design in Scientific American. After sorting out the wiring error I was frustrated, because it could not be calibrated. Afternoon readings never corresponded at the same angle as in the morning. Then following 9/11, although I only obtained a few reading between clouds, I had an approximately extrapolated calibration from a few points. A similar thing happened after the northeastern power black out. But, because of clouds between readings, I have never been sure of that extrapolated line from a few points. In conclusion, the sky is not as blue as it used to be. And it is clear that my age (79) shows that younger people like to think they have found something new when so many things were obvious to all who cared to look in the old days. And it didn't take instruments to be aware of the difference. OK to print. Keep up the good work & encourage visual observations.

Ivor

The Dirty Snow article gave references to the well known fact that dirty snow melts faster than clean snow. What Vincent Giovannone did was to quantify the phenomenon. Your observations about how the melting is affected by haze are interesting. They remind me of what happened in Brazil when I tried to use sunlight focused through a large Fresnel lens to incinerate bacteria culture trays. The lens worked great in Texas. But the smoke was so thick in Brazil that it was impossible to melt, much less incinerate, the agar trays. Editor.

Explanations for Natural Phenomena

Editor,

I am 79 years old and retired from the Border Patrol. I have always wondered about things I have seen. In cold weather a barbed wire fence will sometimes vibrate like a plucked guitar string. I have also had my car antenna do the same thing so violently that I slowed down for fear of it snapping.

As a very young man I worked on oil drilling rigs. One day while driving to work, traveling west we could see the rigs (there were several in the area) up in the air about 200 feet higher than they should have been. Ordinarily they could not be seen from that distance. This was near Sundown, Texas.

One more: I was working the midnight to 8 AM shift on an oil rig near Seagraves, Texas. That area was famous for sandstorms in those days (about 60 years ago), but it was still that day. We had changed from our work clothes and were waiting for the day crew. A cloud came rolling in from the north, horizon to horizon as I remember, rolling like a barrel. I could still hear well then, and it made a hissing noise as it went over. We were dumbfounded. One man said ". . . I bet there is a tornado at each end of that thing." What did we see?

I hope I have asked these questions clearly and that you can tell me what I have seen.

Roy Huntley

Readers, what do you think? I posted Roy's e-mail at the SAS Community Forum under "Explanations for Natural Phenomena," and you can visit the forum to see what Mike and Jim wrote in response. More comments are welcome. Editor.

Window flow: Glass vs. Lead

Editor,

In your "Wanderings" column of 1 February 2008, you state that there is no flow in the glass used in stained glass windows.

While I do not dispute this, I would like to point out that it is possible for an entire stained glass window to flow due to the flow characteristics of the lead used to hold the windows together. Perhaps this is
the origin of the reports on glass flowing.

About 25 years ago we build a house and installed a stained glass window salvaged from an old building. It was clear that the glass had moved over the years and there was some buckling at the bottom. The movement however was not due to glass flow but rather to flow of the lead strips used to hold the window together. As the pattern was symmetrical we mounted the window upside down so the glass would slowly flow back to is original position. Some of the flow may have been accelerated by the warm temperatures in the summertime.

I have also seen wire solder that was stretched to form a tapered section after being stressed by holding up a weight over a period of many days. This is another example of cold flow characteristics.

Allan Rydberg

More About Vacuum Tubes

Editor,

You wrote, regarding my response in the latest issue of The Citizen Scientist (February 2008):

David, I should have stressed that the article emphasized the consumer and computer uses of vacuum tubes vs. transistors/ICs. As for the peak of vacuum tube technology, it would be interesting to see a sales chart. I suspect that far more tubes were sold in the 1950s than in the 1970s. Editor.

The internet is a wonderful place. You can find almost anything (or, at least, a pointer to it) if you know where and how to look. :-)

Here's a report of vacuum tube production from the 1930s until the mid-1970s:

http://deane.bio.ucalgary.ca/TubeProduction.pdf

According to the data in this chart, the peak production year for vacuum tubes was 1955, with 479.8 million vacuum tubes being produced. However, that doesn't necessarily tell the whole story, since there may be an apples-to-oranges comparison being made. For example, the compactron type of vacuum tube wasn't introduced until 1960/61 (by GE), and compactron type vacuum tubes typically contain multiple active sections, rather than the single or dual section in most previous types of vacuum tubes. Thus, fewer "envelopes" may be required, despite the number of active sections being the same. For example, the vacuum tube count in a classic AA-5 type radio of the 1950s could be reduced from five vacuum tubes to only two by using compactrons:

http://home.netcom.com/~wa2ise/radios/compactron1.jpg
http://home.netcom.com/~wa2ise/radios/compactron2.jpg

Another source of the decrease in vacuum tube numbers, not related to the use of transistors in the strictest sense (although definitely related to solid state electronics), is due to the replacement of the vacuum tube performing the power rectification function with solid state diodes. Prior to about 1940, the power rectification function was almost exclusively a job for a vacuum tube (discounting the use of
chemical/electrolytic (slop-jar) rectifiers). Following that period of time, solid state rectifiers started to make an appearance, first with selenium-based rectifiers, which have some awful characteristics and barely deserve the title of rectifier,.and subsequently with silicon rectifiers. (Selenium has some VERY interesting properties. See H. K. Henisch's book "Rectifying Semi-conductor Contacts," 1957, Clarendon Press, Oxford for some of the details.)

Additionally, there's some ambiguity regarding the phrase "vacuum tube technology." Does this mean the technology associated with vacuum tube production (e.g., the physics, material science, engineering, etc. that goes into making a vacuum tube), or the technology produced by using vacuum tubes (e.g., the TVs, radios, computers, etc.)? Note that the sales figures for vacuum tubes may not be directly related to the technology of making vacuum tubes.

David W. Glass

Correction

Editor,

I found Paul Verhage's page when I was looking for the approximate altitude at which the sky no longer looked blue, and you had the answer, thank you. There were, however, a couple of errors:

1. The altitude of 75,000 feet was indicated to be 2.3 km vs. 23 km, a small problem.

2. A somewhat larger problem was the ascertain that space has no gravity. The lack of gravity you referenced in the case of a satellite as free fall is not quite true. Free fall refers to falling toward the local significant gravity source at it's local acceleration rate. The Earth orbiting satellites maintain their local "0" gravity as a result of their angular velocity generating a centripetal acceleration equal to and opposite the Earth's gravitational acceleration.

Ken Hall

The metric conversion error was mine. Paul's response follows. Editor.

NASA is able to generate brief periods of micro-gravity with their airplane, the vomit comet.

If there was a pillar tall enough to hold the Shuttle stationary at its orbital altitude, the astronauts would feel a sense of gravity, albeit, less than at sea level. My calculations have shown there is a 1% reduction in gravity for a balloon at 100,000 feet because of gravity's 1/r-squared nature.

Paul Verhage

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