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The Antikythera Mechanism Episode 7 - Making The Saros & Exeligmos Gear Train - Duration: 25:25.
G'day Chris here, and welcome back to Clickspring.
In this video I make the gearing and support structure required
for the eclipse prediction train of the mechanism.
Despite the fact that a solar eclipse is a reasonably common event,
they do tend to be fairly localised.
So most of us rarely get to see more than one or two over a lifetime.
The result is that even though we have a complete understanding of what's going on,
the passage of totality over the surface of the earth
retains its power to completely captivate our attention.
It is to say the least, a profound experience.
And it was perhaps even more so in the Ancient World.
Across many cultures, Eclipses, both lunar and solar
were believed to be omens of great significance.
Foretelling the imminent death of a ruler,
the outcome of a military campaign.
Or on occasion just providing a good excuse to justify a particular course of action.
Little wonder then that the Ancients chose to include an eclipse prediction function
when constructing their all encompassing model of the Cosmos.
At the heart of the eclipse prediction method used, is what we call The Saros Cycle.
Yet another fortunate cosmic coincidence,
where 223 lunar months after a given eclipse,
a nearly identical eclipse will occur.
This leads to what's known as a Saros series,
where over a period of well over a thousand years,
roughly 70 to 80 eclipses, will follow one after the other in sequence,
separated by the regular interval of 223 lunar months.
The observation of any single eclipse from a given Saros Series,
is all that's required to identify the date and the time of all subsequent eclipses
within that series, and so makes possible accurate eclipse prediction.
Now the Saros dial carried the markings for a large proportion
of the eclipse series that were active during the period of the mechanisms construction.
I'll cover this in more detail when I engrave the dial in a later video.
But essentially all the user needed to do to predict an eclipse possibility,
was to crank the mechanism forward until the Saros pointer reached one of the marked cells.
The inscription indicated whether the eclipse was solar or lunar,
as well as the nominal time of day that it was to occur.
And the month of the eclipse was simultaneously indicted on the Metonic dial.
Now since a lunar eclipse can only happen at full moon and a solar eclipse at new moon,
the day of the eclipse could be easily identified.
By simply noting the day that the required lunar phase was to occur,
or by cranking the mechanism forward and using the front dial to observe the day of alignment.
So Ignoring sign convention, and viewed from the perspective of the pointers,
the Saros gearing calculation can be represented as follows.
Again, you'll notice that the 53 tooth gear is cancelled out,
and with simplification, the expression can be reduced to the following.
Which presents the behaviour of this part of the mechanism in a very intuitive way.
Because, you'll recall from the previous episode
that the Metonic cycle is 235 lunar months in 19 years.
So 19/235 is just another way of saying "one lunar month".
We need 223 of these months to represent the Saros cycle,
and we'd like them to be divided over a 4 turn dial.
A slightly less intuitive way of presenting it is as the number of days.
But this does highlight one of the defining characteristics of the Saros cycle:
And that is that its not a whole integer number of days.
That 1/3rd of a day remainder, has an effect in particular
on the location of the repeating solar eclipses.
The earth of course continues to rotate for that additional 8 hours,
and so the location of the repeat eclipse is shifted about 1/3rd of the way around the
Earth.
After 3 appearances, its back very close to the original location.
Which brings us to the Exeligmos pointer.
Its role is to indicate this 8 hour time shift information,
advising the user to add either 0, 8 or 16 hours to the nominal eclipse time.
And again the gearing calculation can be simplified to something
that shows exactly what's going on.
We see 223 lunar months, the Saros period, multiplied by 3.
Or as its otherwise known, The Triple Saros.
So where exactly did this deep astronomical knowledge come from?
Well essentially from direct observation of the night sky.
It turns out that the Saros cycle,
and in fact much of the other astronomical knowledge underpinning the mechanism
was known to the Babylonians for a very long time prior to the mechanisms construction.
Clay tablets from the period suggest a culture that were serious watchers of the night sky.
With continuous detailed observations, that spanned generations.
These observations were used to develop sophisticated predictive models,
and much of the research supports the idea that at least some of this knowledge
made its way into Ancient Greek culture.
So the astronomical heritage of the mechanism is relatively well understood.
But we know much less about its engineering heritage,
or the workshop tradition that enabled its creation.
Currently, the best source of information is the device itself.
Because its features directly imply the existence of certain tool technology.
Now the exact nature of that technology is the big question,
and we may never know for sure.
But we can certainly try a few things out and see what might have been the case.
So with that in mind, its time to open up a hole position that I marked back in episode 2.
This is the pivot location of the E assembly, and its a perfect opportunity
to make the very first hole in the mechanism using some of that ancient tool tech:
The Pump Drill.
I'll be adding a considerable amount of gearing under the E assembly in a later episode,
that essentially supports it.
But in the meantime I need a temporary support and this bearing will do the job.
For this part of the train there are 5 wheel assemblies to make,
as well as their supporting structures.
Starting with the E assembly,
the scans show that the ring gear was fastened in place using rectangular pierced lugs
and styled cotter pins.
Most of the mechanism uses simple tapered pins fastening,
so this is different, and certainly gives this assembly a distinctive character.
Its important when installing the lugs that the wheel alignment be maintained
throughout the process.
So to help with that, I used the small jig that served a similar purpose
when making the main solar drive wheel B1.
With a simple bushing installed, it can now serve in a similar role
as a drilling platform for opening up the holes for the lugs,
and also as an alignment tool during the fitting process.
That first hole serves as a convenient drilling guide for the hole that'll receive the lug.
I turned the lugs to be a light interference fit in the holes,
so a gentle tap with a hammer was enough to seat them tightly home in preparation for peening.
Ok, so with the first lug in place, the next step was to open up the matching rectangular hole,
so that the wheel can slide into position over the lug.
The alignment jig now becomes essential,
making it possible to progress through the fitting process for all 4 lugs,
whilst being quite sure that the wheel alignment is being accurately maintained throughout.
The cotter pins were then brought to a close fit with the lugs and pushed firmly into place.
OK, so with the E assembly complete for now, I moved on to the F assembly.
Which unlike most of the wheel assemblies made so far, rotates on a post support structure.
The wheel assembly consists of 2 wheels that are permanently staked onto a square hub.
Requiring the formation of the hub, as well as the opening up of the wheels to match the square.
Off camera I turned up the post and riser that make up the supporting structure
for this assembly.
Its a simple disc spacer, and a post that passes through the main plate
to be fastened with a pin and washer on the other side.
Next up is the bearing for the Saros pointer,
which is yet another composite structure consisting of a rectangular block body
and a separate spacer flange.
The Saros arbor was formed with a very light taper to ensure that the wheels were a firm,
well registered fit.
And the pivot sections turned to be a close running fit in the bearing.
Now Its helpful to consider the H and I assemblies together,
since they share this most unusual pivot block as a common support structure.
The arbor for the Exeligmos assembly was constructed in the usual way,
but I made a temporary and quite short version of the H arbor
to allow for a specific depthing technique that I'll show in a moment.
What I call the HI Pivot block is an unusual little idea,
that will eventually require a small clearance notch to be removed in a later episode.
In fact it'll remain loose in the mechanism until I can cut that notch.
For now though, its enough to simply depth and plant the 2 assemblies
in a suitable place on its surface, and form the basic profile.
The main plate was then opened up, and the square bearing hole formed.
These two positions are essentially absolute locations, governed by the dial artwork.
And depthing could have been conducted from these positions before filing out this square
hole.
But at the risk of the position almost certainly moving as the square was formed,
and so compromising the depth.
So its worth pointing out that the Makers choice of putting the F assembly on a post,
rather than an arbor, permits the use of a very simple and practical depthing tool.
This means that depthing can be left until after the square bearing has been fitted,
and so any position error can be accommodated without issue.
The temporary version of the H arbor, means the HI pivot block can be used in a similar
manner.
A small pin ensures that it pivots from the Exeligmos position,
and the block can then sweep over the surface of the main plate,
to find the correct depth of engagement for the H assembly.
Again removing the risk of the Saros pointer bearing being poorly positioned
when filing the square.
Now of course the very compact nature of the machine
means that vertical clearances also need to be accurately set.
I mentioned in Episode 3 that I think the composite structure of the assemblies,
and in particular the use of spacer components,
was the secret to achieving the incredibly close clearances implied in the wreckage.
And here's a perfect example of what I mean.
The height of the saros pointer assembly is set by the height of the bearing in which
it sits,
and that height can be easily set by this little spacer.
I originally made it slightly oversized,
but its a straight forward job to set a clearance of just a few hundredths of a millimeter,
by simply abrading the spacer until the barest daylight remains between the adjacent assemblies
No special tools, or absolute measurement are required.
Just keen eyesight, and a flat abrasive surface.
The entire mechanism could have been set to very close clearances
using this simple trial and fit method,
and I'll continue to use it as I move forward with the build.
Ok, so with the depthing and clearances set, the temporary H arbor was removed,
and replaced with the permanent full length version.
This arbor threads up from underneath the plate,
and so requires that a fastening pin be positioned just above the wheel and pinion.
And I used the bit component of the pump drill on its to form the hole.
It is much slower than using the driving mechanism,
but using it by hand gives greater control over the hole position.
The other assemblies were pinned using the same technique,
and with that complete, its time to put it all together and see how it performs.
In the next video I'll make a start on one of the more remarkable sections of the mechanism:
The gearing that models the lunar orbit.
Thanks for watching, I'll see you later.
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If There's Acid Rain, Is There Basic Rain? - Duration: 3:10.
♪
Pretty much everyone's heard of acid rain: rain that's more acidic than normal because
it mixed with pollutants in the atmosphere.
Acid rain can corrode buildings, weaken nutrients in soil, and harm plants and animals — so
it's not very nice stuff.
But acids are only one side of the pH spectrum.
So what about basic rain?
Why don't we hear more about that?
Well, because even if it can happen, it's probably not worth losing sleep over.
While scientists do describe acidity in a few different ways, depending on what they're
doing, one of the most common is using pH.
And one way of understanding pH is to focus on the concentration of hydrogen ions in a
substance.
As pH drops, the substance is more acidic, and essentially there's more hydrogen ions
available for bonding.
And as pH goes up, the substance is more basic.
It either grabs hydrogen off of other molecules, or forms hydroxide ions that can grab free
hydrogen ions.
Pure water's pH is exactly 7, which is perfectly neutral.
And natural rain's pH is about 5.6; it's slightly acidic from mixing with carbon dioxide
in the atmosphere.
Rain can get more acidic if water in the atmosphere mixes with gases like sulfur dioxide or nitrogen
oxides, which mostly come from pollution.
And once rain's pH falls below 5, it's officially known as acid rain.
Acid rain can be surprisingly acidic: Some samples have been comparable to vinegar, or
even stomach acid — with a pH of around 1.5.
Because of how the pH scale works, that's about 10,000 times more acidic than normal
rain!
In principle, things could go the other way, too.
If atmospheric water mixed with the right stuff, it could become basic instead of acidic.
But rain's natural acidity means that it would need a lot of compound to turn basic,
and there isn't much stuff in high enough concentrations in the atmosphere to affect
rain so strongly.
Plus, we just release way more pH-lowering chemicals than pH-raising ones — making
the challenge even harder…not that this is something to strive for.
But that doesn't mean basic rain is impossible.
Rain near deserts and other dusty places with calcium-rich soil tend to have more neutral
rain.
Calcium compounds are a pH-raiser when they mix with atmospheric water.
And there are even a few places where enough calcium or ammonia get into the atmosphere
by natural sources or pollution and turn rain slightly basic.
But it's not widespread.
Because so many more pollutants turn rain acidic, scientists have actually been searching
for ways to use the science of basic rain to their advantage.
When acids and bases react, they neutralize each other, making a substance that's much
less harmful and reactive.
And some researchers have considered releasing calcium carbonate or another base-maker into
the atmosphere, or leaving them on the ground in places affected by acid rain, to neutralize
the extra acid.
So even if basic rain isn't a thing most of the time in most of the world, the science
behind it might help us battle our environmental issues.
Thanks to our Patreon patrons for asking this weird question!
If you want to learn about more strange precipitation, check out our video about animals falling
from the sky.
And if you want to keep discovering all kinds of science with us, you can always go to youtube.com/scishow
and subscribe.
♪
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Academy of Art University - W...
For more infomation >> Academy of Art University - W...-------------------------------------------
Man Left His Life And Family Behind To Live In The Wilderness But Made One Fatal Mistake - Duration: 7:14.
Christopher McCandless is considered by many to be something of a modern-day
folk hero his decision in the early 1990s to abandon the comforts of modern
life and live simply has inspired others to reconsider how they spend their own
lives yet the truth is that he was mostly unknown saved for the friends and
family who knew him and his untimely demise at the age of 24 wasn't quite the
romanticized adventure it was made out to be while there's certainly value in
appreciating his rejection of material things Christopher McCandless is story
maybe at heart a cautionary tale
Christopher McCandless his life story was a mysterious and tragic one born in
El Segundo California on February 12 1968 he relocated in 1976 with his
family to Anam Dale Virginia when his father Walter accepted a job with NASA
one might think this was a recipe for the family's success but a startling
discovery changed everything Walt's career provided a comfortable
life for Christopher but that didn't mean it was always a happy one already
known for his stubbornness in temper Christopher was livid when he learned
his father had been keeping a shocking secret Christopher learned that his
father had a secret family in California complete with six half siblings whom
Christopher never met this revelation changed the way the young man thought
about the world and he stopped speaking to his parents until his college
graduation Christopher attended Emory University
where he was a good student who maintained a 3.72 GPA and expanded his
interest in social issues such as South African apart eight it was also at that
point that he began to renounce the wealth and comfort he'd grown up with
Christopher referred to college as a 20th century fad and when he graduated
he donated over $20,000 that his parents loaned him to Oxfam a charity that
fights world hunger in 1990 he left most of his possessions at home as he stepped
off for the adventure that would define his life Christopher denounced his
family and started a new life never speaking to them again
he even gave himself a new name Alexander Supertramp inspired by the
1908 book the autobiography of a super tramp by William H Davies on a mission
to achieve a more meaningful life christopher travelled through several
states until his car stopped functioning due to a flash flood in Carthage South
Dakota but that didn't seem to upset him much this piece of my life has also been
abandoned he wrote in a note whoever can get it out of here can habit
Christopher interpreted that setback as a sign from the universe that he should
have end in every comfort he enjoyed in his past life he continued the rest of
his journey with no particular destination however he could whether
that meant illegally hopping on trains hitchhiking biking or even canoeing
throughout his adventure christopher kept a journal while a bit bizarre many
people have found inspiration and passages like this it is important in
life not to be strong but to feel strong to measure yourself at least once if you
want something in life reach out and grab it
Christopher eventually settled in Alaska where he found shelter in the abandoned
bus 142 in the remote Stampede trail he stayed in this makeshift home for months
living off the land by hunting animals like squirrels and porcupines 43 days
and do we stay in the bus he shot it relatively small 600-pound moose he was
so proud of himself that he took a picture with the carcass in an effort to
preserve it he smoked the meat but magnets appeared five days later the
young man had no choice but to let the Wolves habit I now wish I had never shot
the moose he wrote one of the greatest tragedies of my life it was evident that
Christopher was ill prepared for his new lifestyle he only owned a camera some
paperback books including one for identifying plants a zero point two two
caliber rifle a compass and a sack of rice more than three months after he
started living in the bus Christopher finally attempted to return to
civilization he packed up the few items he owned and even shaved his beard yet
when he reached the top clinical River he realized it was impossible
Christopher crossed the river months earlier when it was four
despite falling on the ice in the process yet when he returned in July the
glaciers had melted in the waters were rushing again he had no choice but to
walk back to the bus after returning to the bus christopher realized he was in
danger I need your help he rode in a torn page from a novel I am
injured near death and too weak to hike out of here I am all alone this is no
joke in the name of God please remain to save me I am out collecting berries and
shall return this evening in time Christopher resigned himself to his fate
I have had a happy life and thank the Lord
goodbye and may God bless all the final entry in his journal read happiness is
only real when shared on September 6th 1992 the 24 year olds decomposed body
still in a sleeping bag was discovered by a moose hunter starvation was
officially ruled his cause of death but it may have actually been a bit more
complicated than that Christopher indeed starved but it was
later revealed that this was likely due to eating wild potato seeds that have
been known to prevent nutrients from properly being absorbed it also would
have gradually paralysed the already weak young man so hunting for more food
would have been impossible in January of 1993 writer Jon Krakauer made a splash
when his account of Christopher's odd life was published in an outside
magazine article titled death of an innocent he expanded the story in his
1996 biography into the wild which further raised Christopher's profile
writer and director Sean Penn adapted the book into an acclaimed film of the
same name in 2007 Christopher's story continues to divide
people to this day he's this Rorschach test people read into him what they see
Krakow remarked some people see an idiot and some people see themselves not
surprisingly admirers of Christopher's philosophy and those who are simply
fascinated by it go as far as to make a pilgrimage to the Magic Bus itself it is
by no means an easy trip Christopher made a choice that many believed to be
foolish and selfish but the alternative was following a predetermined path that
he didn't truly believe in no matter where you stand on the matter
it's hard not to appreciate that he lived life he believed in whether you
think of Christopher McCandless as a young philosopher who died too soon or a
naive kid who took in necessary risks it's no surprise that so many have been
captivated by his journey what do you think about Christopher McCandless in
his life comment below I hope you like this video then please hit the subscribe
button in click on Bell icon to never miss the video from our Channel
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4 signes que votre relation est en danger ! Surtout le 3 !! - Duration: 7:53.
For more infomation >> 4 signes que votre relation est en danger ! Surtout le 3 !! - Duration: 7:53. -------------------------------------------
نيوتن - عقول قذرة | newten - Dirty Mindz (Official Video) - Duration: 1:11.
His mind never get get older
عقل جامد
from NP colder
Every rapper in the yard
من فضايحة انا عندي folder
From small to the big He's pimp like a pig
You coma 2 newten with a confidence 2 show your power
He put in your f**k'n a hole big tower
yo yo
عله....... ايدي...... مربيه
لكنانا كنت ا*** فيه
كلما بيكثر من الثرثرة لايناتو جداً مستنثرة
هدفي سامي ...هدفك انو تنشهر بوسط اعلامي
soooooooo
Don't stand امامي
بغني لحد ما اوصل لحبل اعدامي
ma own f**k'en fataly
اسلوبي انا....جداً قتالي
Doooon get 2 newten zone
هووون بيركع كل الكون
must shrup(shut up)في حضور نيوتن
من سم بنشاتي هوو شرب
لكن هنة منقدم طرب
من قصف كلماتي انضرب
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MY FIRST KPOP SONGS - Duration: 5:15.
*My first ever kpop song
Exo - call me baby
Exo - don't go
Exo - thunder
Big bang - bang bang bang
Seventeen - pretty u
Bts - save me
Infinite - bad
Astro - breathless
Astro - growing pains
Shinee - sing your song
Exo - heart attack
Got7 - just right
Got7 - if you do
Big bang - let's not fall in love
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