Point of order - the earliest water clock was dated to around 1500BC
It is a fair point that they almost certainly used some slow and very tedious method of cutting the teeth into the gear.
But they had geometrical constructions that have now largely been forgotten. Their brightest people were probably as clever as they are today but less was known. They did have time on their side though.
Odd choice of technology for a space faring civilisation.
-- Regards, Martin Brown
Yes, go to any sailing forum and observe the interminable discussion about sextant vs. GPS...
Mike.
for 127 points on a circle
Use piece of string, divide it into 128 sections (by successive halving, or just by repeating the same 1 unit measure 127 times), overlap the first and last section to make a loop, wrap it around the apropriate sized circular form.
You could cut a circle at r=128 using a lathe, or cutting compass, use that to measure the string and then reduce the radius to 127. use a pantograph to scale as needed.
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Unfortunately perfectly spehrical. you need three to get planar surfaces.
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That's not a "time clock". On this side of the pond, a "time clock" looks like this: The first patent for a time clock was in 1890. As far as I can tell, no water was used or was necessary. With a water clock, I suppose Archimedes and Associates could have "punched the clock", but then, punched cards also hadn't been invented.
Slow, tedious, monotonous, boring, and dangerous were not considered a problem in an age when slaves were cheap and did all that. It was also considered a social disgrace for a member of the upper classes to get their hands dirty. I suspect that some of the slaves may have been better educated and more clever than their upper class masters. The masters had no reason to learn to read, write, or operate the machinery. I think it's conceivable that some of the more amazing inventions of the distant past, were actually contrived and built by slaves, rather than their masters with their clean hands.
True, but not totally forgotten: There's a Nova video on the topic (in 3 parts): Archimedes got very close to inventing calculus.
No doubt that some people in 250BC were clever and very bright. However, was it the upper classes, who dabbled in politics, society, abstractions, royal succession, and religion, or was it the ordinary slaves who were relegated to the mundane tasks of building astronomical appliances?
Well, I meant that as a bad joke, but it's not so difficult to believe. A visitor from a space faring civilization arriving on earth would most likely be greeted in the traditional human manner of "kill them and eat them". Under such circumstances, offering something useful to the natives might dissuaded them from having their visitors for dinner. Anything more sophisticated than a mechanical calculator would probably have been considered magic or the "work of the devil" resulting in exactly what the alien visitors were trying to avoid. That's unfortunate as we may have missed our chance at getting a scientific computer 2200 years early. Instead, we had to settle for a crude wind-up toy version.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
ch
I allowed my own experience to mislead me. The Greeks had been using lost w ax casting technique to make clay molds from about 500BC
The clay molds had to be baked after the wax had been melted out to get rid of any residual water before the molten bronze was poured in, which one mi ght fear might distort them, but classical Greek bronze statues were made u p of a number of separately cast sections, so the molds seem to have been p retty stable (and seem to have been reused to make several copies of the sa me statue.
Only if the sand hasn't been properly dried out. A modern would probably ev acuate the sand mold and let the molten metal flow into the evacuated mold.
So it wouldn't been sand cast, but cast into a clay mold.
I'm envious. It doesn't look as if you did much background reading - clay m olds do seem to have worked better for the Greeks.
-- Bill Sloman, Sydney
Lasse posted a link to a video showing exactly how files were likely made with the technologies available at that time. Read a few posts up, it is a very interesting video.
Rick C.
I didn't realize that lost-wax casting was available to the Greeks. That's a good indication of what little I know about classical Greek art. So, I just did some remedial reading and Googling, looking for how the Greeks might have used lost-wax casting to make rather thin gears. This document seems to indicate the thickness of the various gears: The thickness of most of the metal sheets appears to be from 1 mm up to 2 mm, except for fragment 26, which is has a layer of 2.6 mm. I don't know if it's possible to cast 1mm or 2mm thick gears, but I would guess(tm) it's rather difficult. It seems that forging, hammering, and sanding between two flat stones, would be easier.
The gear teeth were in the form of equilateral triangles with an average circular pitch of 1.6 mm, an average wheel thickness of 1.4 mm and an average air gap between gears of 1.2 mm.
That's very thin and very fine. The bronze Greek statues were apparently quite massive. There was plenty of detail, but nothing that fine.
That also brings up another question. One of the YouTube videos shows the gears being cut by a home made steel square file, where the teeth were cut by a home make hardened steel chisel tip. If that was used to cut bronze that was 1.4mm thick, then the maximum teeth spacing would need to be about the same 1.4mm and then only if the teeth were cut at an angle to the center axis. I don't think the method shown would work to make such fine teeth. The files that author made look very fine, but I can't determine the tooth spacing without a reference dimension.
Also, note the thickness of the gear shown in the above video at 0:27. My guess is that bronze (brass?) gear is about 3mm thick. 1.4mm would have either cracked when bent by the file, or wobbled badly resulting in a sloppy tooth cut. The tooth precision is fairly important in a device that has so many gears. Without anti-backlash gears, the tolerances would tend to accumulate, resulting in some potentially large errors.
Lost wax casting often involves a vacuum pump. I'm not sure that's true with sand casting. I don't know anyone that pours hot metal inside a vacuum chamber. I suggest we switch to lost-wax casting, and drop the sand casting theory.
Possibly, if the casting could be made thin enough (1.4mm). I don't think it can be done but I'm not sure.
Don't be. Mine was badly planned and executed. I couldn't find any photos, but it was basically a pile of firebricks, a propane burner, propane tank, crucible, and some Unistrut bracing to hold everything together. This is close, but mine was 2-3 times as big: I only cast a few test objects from aluminum. I would have done more, but my father had a stroke and I had to drop everything and temporarily move to Smog Angeles. I'll probably build something similar again for my knife making projects, but this time using a much smaller furnace: or maybe something electric:
I do my research after I submit my claims and assertions. Some day, I might learn to reverse the order. In this case, I don't know anything about Greek art and history but do know something about metalcraft, machine shop practices, and old hand tool technology.
As far as I can determine from an hour of light reading, the Greeks were primarily into casting big and heavy statues. I found nothing on casting small objects, such as gears. I suspect it might be possible to tell if the gears were cast or forged by cutting a sample of the bronze from the gears and looking at the grain structure. However, I also suspect that the Greek museum would never allow that.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
the same statue.
Which of course would require moulds in parts each strictly concave; quite a constraint!
Mike.
:
They were the statues that got famous and were copied in marble, which can' t be recycled (while bronze can).
There would have to have been a bigger market for smaller decorative object s.
Your jeweller wouldn't have wanted to cast many big statues.
The chances of such small objects surviving isn't great - bronze can be mel ted and cast into a more fashionable shape whenever tastes change.
You could probably get an internal image of a whole gear with synchrotron X
-rays. Paleontologists are now pulling internal structural detail out of mi neralised fossils with the really energetic X-rays you can out the re-purpo sed Standford Linear accelerator and similar machines.
-- Bill Sloman, Sydney
OK, well it was a long time ago I read this and it's not my field anyway.
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On Aug 10, 2018, Jeff Liebermann wrote (in article):
Umm. A Starship in the Iron Age? Methinks that dissuasion involves at least a laser blaster. Even a Colt 45 would suffice.
Joe Gwinn
Nothing happens without proper motivation(s). What would motivate an alien race to give the backwards planet Earth a visit? Forget about Star Trek and "go to where no man has gone before". The explorers probably took one look at Earth, and just kept going. Think about what motivated the European explorers and immigrants that followed Columbus. Motives vary, but a good percentage were looking for trading partners and were out to make money for themselves or for their backers. Same with the alien visitors. They land on Earth and realize that the residents have little or nothing to offer. However, if human science and technology could be accelerated, they could return in a thousand solar rotations and perhaps the humans might have evolved into better and more profitable customers.
So, what gifts would an alien race leave behind to accelerate progress? It's not going to be a better weapon as they would most likely exterminate themselves. It's not going to be an encyclopedia because no human of the day would understand it. It has to be something that would help humans do something that they already are doing, but better. Something that humans can understand and appreciate. Reading the stars to predict the future has been around for a long time and shows little indication of disappearing. So, the alien visitors left humans with a better way to read the stars and predict the future. Eventually, humans will find better uses for the device, and progress will lurch forward.
Incidentally, the ideal gift problem is the same for giving presents to worthless slacker teenagers.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
There are methods for doing anything geometrical. A Nova last year explained how they tapered the columns of the Parthenon. It's such a gradual taper no one knew how. Then a diagram was found on the wall of an unfinished building, which the builder used as a scratch pad. He just drew the column actual size in the horizontal dimension but squashed to 1/100 vertically. Then a compass with its center a few feet away could make the curve. The curve marked the diameter at the top and bottom of each cylindrical stone, since it was actual size in that dimension.
The same way Harrison made clocks, I suspect. His methods, or most of them, would have been available to the Greeks. Some modern watchmakers use the same scratch methods. R. L. Ronnie makes his own tools from scratch which are works of art by themselves. But most people in this group, if they did it, wouldn't bother to engrave the heads of all the screws in the tools. I think that's an indication that people who are able to figure out how to do such things are in a special class.
On Aug 11, 2018, Jeff Liebermann wrote (in article):
I would hazard that the better analysis is why we landed on the Moon, and will someday land on Mars.
Or the reasons that Anthropologists spend years studying early stone age cultures.
For all the talk of mining the asteroids an the like, no way the money works with present day technology.
As for future commercial activities, it would have to be raw materials of some kind, ones that couldn?t be synthesized cheaply on the home world of the alien explorers.
A gift of tools and in particular how to make them is very powerful. For instance, how to mine and fashion iron and steel is fundamental. Steel is much more useful for say woodworking than copper and bronze.
And, if the culture is sufficiently advanced, the idea of science and the scientific method.
Purported Old Chinese saying:
Give a man a fish, and he eats for a day. Give a man a fish-hook, and he eats for a week. Teach a man how to make fish-hooks, and he eats for a lifetime.
I recall this from decades ago, but cannot recall where I got it. .
Slackers are not slackers for want of infomation.
Cut off the food.
Or worse, remove the TV (and all equivalents).
Joe Gwinn
Precise metal-working lathes were not available then
put together first all metal slide rest lathe around 1751, and famously spe nt a long time making high quality lead screws for it by averaging out the errors on one length of one screw against the errors on another length of a nother - a very tedious process.
Obsessive-compulsive. More obsessive compulsive than most of us, not so muc h more obsessive compulsive that they need to be looked after to prevent se lf-harm.
-- Bill Sloman, Sydney
Same reason as sea captains were quite pleased to find islands in the almost endless oceans - a chance to get some fresh food and relax.
Interstellar travel has got to be incredibly tedious unless you can find some way of warping spacetime to allow you get there more quickly.
Alcohol mirrors and shiny coloured beads seem to be de rigueur.
-- Regards, Martin Brown
You mean like Charles Darwin? I seem to recall he stopped at a great many minor whistle stops. That's why they call them explorers, they explore.
Or aliens might be here just to observe. Maybe the like watching porpoises, or sun rise over Ayers Rock is impressive even to them. Let's face it, the view from a space ship gets pretty monotonous.
Money is always appreciated.
Rick C.
Good example. Darwin wanted to take a 2 year joy ride before becoming a parson. It lasted 5 years, but such things were to be expected. The voyage was not intended to be a voyage of exploration. The Beagle was to do detailed hydrographic surveys around the coasts of the southern part of South America and parts of the Pacific. I don't know who commissioned these surveys but would guess military or commercial interests. Darwin was just a passenger.
A parallel would be a starship on a mission of mapping and identifying likely commercial opportunities. The rate of progress of civilizations vary greatly and the odds of the starship talent scouts finding a compatible civilization is negligible. Therefore, they need to leave something with a prospective existing and primitive civilization, that will accelerate their rate of development into a civilization worthy of doing business. I would expect the starship to be stuffed full of suitable educational toys, or maybe a 3D printer. An astronomical calculator would make an idea gift for kick starting a civilization into the space age.
I've been watching various videos on the Antikythera mechanism. It's fairly obvious to me that the device found was not a prototype or the first of its kind. I would guess(tm) that such a device would have had a fair number of more primitive prototypes. It might even have been possible to build a larger version from wood, pegs, stone, rope, and such that perform only some of the calculations. As metallurgy and tools improved, these were combined into the "final" bronze version.
Yep. Coastal navigation is much easier than blue water sailing. One also does not need to carry as much in supplies when hopping from port to port.
I'm sure there were other motivations for the voyage of the Beagle. The problem with only observing the scenery is that there's no money in it, or at least no immediate payoff. I don't know who paid for the two voyages, but I would suspect it was someone with either military or financial motives.
Sure, if they're willing to risk dropping dead from infection by the local bugs.
The first space voyagers would more likely be the social misfits and ne'er do wells of the home world, exactly like the first American colonists were the European unwanted. If one was doing well in Europe, one stayed in Europe. If one was at risk of getting purged by the local despot for the subscribing to the wrong religion or political party, emigration was a good solution. I don't think anyone came to the new world because they were bored with Europe, but it's possible.
Nope. The problem is the same as the alien visitors. What do you give to people who have the potential to do great things and turn into a model citizens, when current indications are that they might not survive into adulthood. Educational gifts would be my inclination, but they already have smartphones, tablets, and computers, which are wasted on chat sessions, Facebook, and playing games. The family car will no doubt be handed down to the kids. My attempts to tech them how to fix things by giving them broken but interesting devices has totally failed. One of the most educational gifts I received when I was a practicing juvenile delinquent were a small pile of old books on chemistry and physics. I didn't understand a word but slowly grew into them as I became older and more sane. The problem is nobody reads books any more. So, the problem becomes the same as the alien visitors problem of selecting the ideal educational gift. It has to be something that will substantially improve on what they are currently doing. For the ancient Greek star gazers, the gift was fairly easy. For todays teenagers, not so simple.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I've a divider for a lathe. It uses holes in a regular pattern of e.g.
13, allowing for a 13 teeth wheel. However, there is a 40 to 1 ratio, i.e. you could also do 13.40 or 13.2 teeth, selecting the number of turns plus the right hole. If you wanted 17 teeth you could select the right holes and the 17 teeth wheel wouldn't look half bad. Now if you use that create a wheel with 17 holes and use that in the divider the deviation would be cut by a factor 40. And you could do that again.In a similar vain, you could estimated the distance for 53 holes. Then you could file an oversized wheel, and then you could correct the filings while going down to size, using a small fixture. Doing some handywork didn't scare the ancient off, the acropolis stones where fitting up to mm's by hand.
[The first lathe didn't have screws that are created on a lathe, they had to be forged. Crude screws in a lathe allow to create much better screws in a next generation. ]-- Albert van der Horst, UTRECHT,THE NETHERLANDS Economic growth -- being exponential -- ultimately falters. albert@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst
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