Blind guides

Sometime, they know the way.

From:
Introduction to Modern Astronomy …

For the medieval astronomer/astrologers the Universe was a small place, the Earth was the center, and events in the heavens were orderly and designed to benefit humanity. The only change that was deemed appropriate was cyclic change such as the (mostly) orderly motion of the planets on the sky or the daily travel of the sun around the heavens, for cyclic change returns one to the starting point and so is not really change at all. In Europe of the Middle Ages this belief was elevated to the level of religious dogma, and one dared challenge this world view at considerable personal peril.

However, the Copernican revolution began a long process that changed completely our perception of the heavens and humanity's place in the Universe. Beginning in the 16th and 17th centuries and continuing until today, observations and increased theoretical understanding demonstrated that the Universe is enormous, that it has existed for periods that dwarf human lifetimes, and that we do not occupy the center of the Universe (for there is no center).

Probably less appreciated is a change with antecedents in events observed hundreds of years ago, but that has accelerated at breathtaking pace over the last 30 years. As observational astronomy at wavelengths other than visible light (Radio-Frequency, X-Ray, Gamma-Ray, Ultraviolet, …) has become more commonplace, we have begun to appreciate that the Universe is party to scenes of unimaginable violence.

Far from an orderly stage for stately and gentle physical processes, the Universe at various times and various places undergoes violent cataclysms releasing energy on a scale to numb the mind of even the most analytic physical scientist.

The medieval natural philosopher would perhaps have had even greater difficulty accepting this insight than accepting the Copernican hypothesis that the Earth was not the center of the Universe, for it would have destroyed the strongly held belief that the Universe existed as a nurturing cocoon for humanity.

However, it is supremely ironic that these violent processes that on the surface seem hostile to the place of humanity in the Universe are in fact essential to the production of the present Universe. In particular, our modern understanding is that there would be no matter as we know it, no life as we know it, and no humanity to contemplate these questions, in the absence of violent processes that would, of themselves, destroy all life within countless light years.

The development of these ideas has been a truly remarkable odyssey in the history of human thought. These lectures represent an introduction to how this modern worldview has come about, and a survey of the often beautiful, sometimes astonishing, but never dull, Universe described by these evolving ideas.

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46 thoughts on “Blind guides

  1. Astronomy has always been an high order research philosophy, because it is used for trade, war and agriculture.People understood cycles. Some even better than we do. In lower latitudes, they are much more striking than they are in the lands of the Kings of the North.Explaining the behaviour of cycles is an high order science. And it still works today. Kopernic introduced a theory that was correct in every way except one:It was unworkable.Captains still had to use epicycles to steer their ships by, right up until the Era of chronometers.Bear that in mind when you hear someone disparage the ancients!

  2. If you draw a line infinitely long it will get to the edge of the universe eventually.This is true no matter where on earth you draw it.Ergo; the earth IS the centre of the universe.QEDPDQ

  3. However, the Copernican revolution began a long process that changed completely our perception of the heavens and humanity's place in the Universe. Beginning in the 16th and 17th centuries and continuing until today, observations and increased theoretical understanding demonstrated that the Universe is enormous, that it has existed for periods that dwarf human lifetimes, and that we do not occupy the center of the Universe (for there is no center).

    Let's get this right.The Jews and the Arabs and various other religious groups already knew the sun was the centre of the solar system. <Edit> I have removed a line disparaging Florida.I had just read an article about a Koran Burning episode in its history. It followed on from a news article about the US army destroying Korans in an Afghanistan Prison / "Information Centre".I got incensed and then I got stupidWhich lead to another smart remark now removed.Sorry about that.<Edit ends.>One day our children are going to wonder at our lack of insight:"Didn't we have access to the internet?""So why did we keep on saying such foolish things?"

  4. For the medieval astronomer/astrologers the Universe was a small place, the Earth was the center, and events in the heavens were orderly and designed to benefit humanity. The only change that was deemed appropriate was cyclic change such as the (mostly) orderly motion of the planets on the sky or the daily travel of the sun around the heavens, for cyclic change returns one to the starting point and so is not really change at all. In Europe of the Middle Ages this belief was elevated to the level of religious dogma, and one dared challenge this world view at considerable personal peril.

    Is it worth going to town on this?Who cares what a middle aged astronomer used to think?What hew thinks now is more important, surely?The rest is just history.So how do you find out what a man used to think?Do you know for a fact what you used to think?When you were a baby you thought like a baby.Then you learned not to think like that then you forgot what you used to think, say and do.Then you spend your next 60 years trying to remember your first thoughts?Is it really so?Don't be silly.People were as people are. Pragmatic, interested, curious even. Stymied by what they once believed but courteous enough to pass on to others what they now find.

  5. Alright, cause you brought it up. I refer back to my analogies of us just being "who's" from whoville. Maybe I overcomplicate, but the level of understanding of a place soo vast, from a place so small… While I love the intrigue of discovery, I just think sometimes we make stone soup to make sense of the senseless.My blog is the hub of the universe, it just got to busy being placarded.

  6. Originally posted by Unasia:

    I just think sometimes we make stone soup to make sense of the senseless

    Nice one.Actually I was looking up one of the authors just now and he has some pretty far out papers on Neutrinos and black holes. We were never going to get together.That doesn't mean he isn't very clever. Quite the reverse.His problem is that he spent too long on the intro. It is at least two lectures online according to what his write ups say. All he needed to do was explain epicycles which he does SPLENDIDLY….eventually.

  7. Also; I am using USA web sites because I don't know any other places that even come close.I have the HIGHEST respect for the USA when it comes to publishing research. It makes the UK look like crap.Maybe that is because most people using English search terms in science are USAns or maybe it is because so much university research and the teaching syllabus of so many top colleges is online from the USA.I don't know.I just look down the first page of Google, get what I want and dive in. I aught to be more circumspect but when your brain is hot yer gots ter trot.I was doing something on oil research papers about a year or so back and it turned out INDONESIA, of all places, was the best for that. I wasn't going to quibble. When you want something and you got it, you use it and then move on. Originally posted by Weatherlawyer:

    Unless you live in Florida you can get hold of a Koran and see for yourself. (I think.)

    I had just been reading something about that Jackarse who got all those lovely troops killed in Afghanistan because he wanted cheap publicity so put out a statement about burning copies of the Koran.Why that man is still alive defeats me. If you like, I'll kill him for you. Just get me in your country and give me a weapon.

  8. There are a lot of things that escape the realm of comprehension for me, propagated by greed, malice and hate. The real moral problem is the propagation of the story, the media becomes a tool for those with lots of money or power, used effectively. We need to expose those of cruel intent for what they are, and it is happening. The internet and its deep dockets of truth change the ball game. blah, blah, blah. Wound me up.

  9. If you want to understand British political history at home in the 19th and 20th centuries, you could do a lot worse than read what the Wikipedia has to say about the Peron years of Argentina.Of course what the working class saw happening to them they were only too willing to copy when it came to others.That's how an empire is run.And why they wash away in time.

  10. I shouldn't have dragged politics into this but I was wound up to bursting too.In the good old days there was no way to get these things straightened. The BBC was used as a tool agains the working class in Britain at one time and with the working class party in power it was once more, under Tony Blair:http://forums.theregister.co.uk/forum/2/2012/03/03/tony_blair_rsa/(NSFW)What surprised me is how easy it was for Wingnuts and Swiftboatmen to take over the net too.Since then, I have not held back.Nor will I.

  11. Originally posted by Weatherlawyer:

    understand British political history

    As a mater of fact, I was watching a series on the monarchy..interesting to say the least. But I will have to watch it a couple more times I think it to get it the names and dates down pat. There is a sense of community that seems to find home in its midset that we lack that on many levels, no one trusts anyone.

  12. Originally posted by Unasia:

    There is a sense of community that seems to find home in its midset that we lack that on many levels, no one trusts anyone.

    Erugh!!Is there a self strangling icon?The British monarchy were a bunch of rabid lunatics. They couldn't wait to kill one another.In a peasant's revolt after the first black Death plague, Wat Tyler tried to lead the serfs to freedom. The young king jumped on his horse and pretended to accept him. Then literally stabbed him in the back.So that was the upper class firmly fixed for the next thousand years.After that there were a bunch of Henrys killing everyone they disagreed with. Just like every tin pot dictator you ever read about in the news.It culminated with Henry 8 whom god was pleased to leave infertile probably because he was such a deceitful, lying, murdering bastard. All his children died fruitless as he deserved but couldn't live long enough to enjoy.Pity.After that we had to get the Scots in and then we ended up killing them, had a dictator for life and then more Scots, a couple of Dutch ones.Then we gave America to a bunch of ne'er do wells and then look what happened! 😀

  13. Originally posted by Weatherlawyer:

    probably because he was such a deceitful, lying, murdering bastard.

    I shouldn't have said that."Because he was a deceitful, lying, murdering, treacherous, evil bastard even worse than the rest of them." is what I should have said.

  14. I am afraid all I am is talk.I wouldn't really kill that areswipe, not even George Bush.Mind you killing George Bush would be an hell of thing to put on your CV.Hmmm…:idea:

  15. He came to the Arena in Kalamazoo a number of years ago, they broadcast it on the radio, he sounded more like a televangical preacher than anything. I must admit to having a strong distaste of him myself,but recognition of what he is, a puppet, and the new one..puppet. It a false structure, or its representation is.The process here has been degraded, by redistricting, recognition of corporations as people…the list is endless, most all pointing to someone somewhere getting rich while most suffer. No one here has faith in leadership or the management of … its full of political appointees who dont know shit about their posts but are good yes men, save a few.

  16. Mr President they hauled you off air when you were about to tell us about the economy. Can you tell us now sir, what were you going to do with it?

  17. Originally posted by Unasia:

    did you say you used to work on motorcycles at one time?

    You lost me on that one.

  18. Note to self:When Opera screws your paragraph spaces, add a couple on the end with blank space marks in between.

  19. Originally posted by Weatherlawyer:

    I'm not even going to comment on Introduction Part 2:http://csep10.phys.utk.edu/astr161/lect/sense/sense.html

    One or two of the students at the Tenesee uni where this came from wrote that one of the lecturers was boring. I think that his writing style graces the internet but imagine his introductions needed to be reworked. If you lose your audience at the intro, you lose the audience. Ken Ring did it with his book about the moon. If you are giving a lecture to a set of people of widely varying backgrounds and unknown beliefs, you MUST restrict yourself to the subject not the background to the subject. Get the brief correct and the sheep will follow. But lose them first with remarks they find offensive, boring or pointless and you won't get them back. The beauty of the ideal in the day of the Internet is that if you interest people in your ideas they will do their own research in their own time. The problem with college is that they have to do it to schedule. However with the course online like it is, you can jump right in to any page you like. Here's a good one: http://csep10.phys.utk.edu/astr161/lect/retrograde/aristotle.html That thing is hidden 10 links in. Half way. See what I mean?

  20. Originally posted by Weatherlawyer:

    You lost me on that one.

    I thought you said you used to do repairs?, I have an old 72 suzuki 185 that needs some carb help.

  21. Righ.Yeah.Ok.Put the kettle on, I'll be round your place in a moment.That's was actually a nice little bike. It handled really well for a lightweight. I believe the oil filler is under the seat. inexperienced riders always forget to fill that. The fuel mix is through the oil feed via the crank so you may have bearing problems by now.I can't remember if you had to put some oil in the tank too.Boy was that a while back! 40 years and more.They used to say that you never got OLD Japanes bikes."THEY" were people you met in pubs who were only there because their British bikes were broken down and thus they still had enough money to buy beer.40 years ago the oldest Japanese bikes were only 5 or 10 years old and their electrics were just starting to get old by then. But they were so fast they didn't often last that long anyway.They were fast and the tires were slick and the electrics worked in the rain. No end of accidents saw off a lot of them.British bikes had the saving grace that if it was raining the bike wouldn't start. They used to last a long time. Try the condenser and if that doesn't work check out the battery. Duff electrics can be mistaken for carburettor trouble sometimes….Ah, just remembered, you won't get a spark if it's anything but a duff condenser, if it is an electrical fault.(Ooh! I just got old. Thanks a bunch!)

  22. its an enduro, has the original manuals, good restoration bike for tooling around. Yeah its a oil injector, but if you suspect problems, you can pre-mix. getting warmer and its a summer project, it will haul me round the back yard in a most fun way. Its low miles, needs to be have lights and signals replaced and seat recovered, but it reminds me of my youth and trail riding.I will put way more effort in than its worth..but. Anywho, if you had been, some guys hang on to parts forever..like me and I was hoping.

  23. Originally posted by Unasia:

    its an enduro, has the original manuals, good restoration bike for tooling around. Some guys hang on to parts forever..like me and I was hoping.

    I often felt like getting a TS 90 or 125 but these days they are all detuned 50 cc things in Britain. Besides I am old and fat now, so a 650 BMW from that era would be more my style these days.I have a spare room full of carpenters tools I don't imagine I'll ever use again. Some nice stuff too. I wonder if someone would like to swap.****Take the tank off and flush it. See if the filter is any good if you can. The carb will probably need a strip down. I bet that would be a piece of cake with a PC camera to record the parts as they come off and hide under your table.Is it electronic ignition?The manual is worth about 50 quid in good nick. So you are quids in with that.

  24. Originally posted by Unasia:

    what kinda carpentry stuff

    Have you got an old BMW you want to swap?Some nail guns, electric saws, planers, routers, chop saw, door jig, lock jig.:awww: Doesn't sound that much now. Maybe a Honda 250?What's that mole grips doing?

  25. In my day we used brown packaging paper with grease or gasket goo. Hematite? Or something like that. But I don't remember them ever working.You will never find a part. Maybe in Australia or on some half closed down forum in France or VietNam.If you ask around on (any number of) classic vehicle forums you might come up with an idea for a work around. There must be a modern material you can cut a gasket from.I once repaired a gas fire element for a Calor (bottled gas) heater with some plasterboard adhesive and PVA glue. Not pretty but worked perfectly. What you need is a thin, soft, hard-wearing, petrol proof, man-handle-able, squashable-without-straining-the-clip/thread piece of something like a gasket, material.Or similar. Something gaskety.Maybe. I used to hate that you were always bent in three wrong directions and stretching two more trying to get a spanner to wind something up or down and it would only move 1/8th of a turn if that, so you had to twist the spanner round to get it to seat for the next fraction of a turn.I hated all that.Seems like you have a sticking float.Apart from that the bike looks amazing for its age. Pity it wasn't an Honda 750 from that era. It would be worth a bomb.

  26. remember me askin about a carb…mole grips stop gas now when everything leaks. The petcock does not seem to want to work like it should, or, like I think it should. I have cleaned the carb out thoroughly, and believe I am down to a lil gasket at the botton of the bowl needing to be replaced. But I found some a nice vid on a lot of it, I just have to commit. Musta been in the building trades. I am all set on most for now in tools, I do keep an eye out.at the re-store we get a bunch of old tools in, they are kind about pricing it. (Most always I give them more than they ask).

  27. more of a o-ring type of gasket, so it should not be to bad. Yeah, nice chrome. good project bike. I had a Yamaha 175 when I was younger, same year,lotsa fun.

  28. This is where the above website gets going:http://csep10.phys.utk.edu/astr161/lect/retrograde/aristotle.htmlTake a look at the animation half way down the page and bnear these two things in mind:1. The behaviour of the moon would be as erratic as Neptune or worse if it were within the ability of the planets to over-ride god's safety device, the moon.2. The most impressive planets are all close to us at the moment.And 3. I have no idea what that means. Though I do have an idea what I mean.

  29. Originally posted by Astronomy 161:

    Planets usually move East on the celestial sphere, the background stars.

    At times the planets moved westward: "Retrograde Motion".
    Also the planets were observed to be brighter at certain times also a challenge to explain.
    Aristotle taught that the heavens were unchanging, that the only motion permitted objects in the heavens was uniform circular motion, because such motion brought everything back cyclically to its starting point and therefore was (in a sense) unchanging. This explained the uniform circular motion of the planets about the Earth (which, as any fool could see, was clearly the center of the Universe).Except:Neither the varying brightness of the planets, nor their occasional retrograde motion sphere, were easily reconciled with this idea of "unchanging objects" executing "uniform circular motion".

  30. Originally posted by Astronomy 161:

    Aristotle proposed that the heavens were literally composed of 55 concentric, crystalline spheres to which the celestial objects were attached and which rotated at different velocities. And that the angular velocity for each sphere was constant. In the Aristotelian concept there was an outermost "Prime Mover" causing the outermost sphere to rotate at constant angular velocity and this motion was imparted from sphere to sphere. By adjusting the velocities of these concentric spheres, many features of planetary motion could be explained. (Except for varying planetary brightness and retrograde motion.) The "solution" to these problems came in the form of a mad, but clever proposal: Planets were attached, not to the concentric spheres themselves, but to circles attached to the concentric spheres. [This is the rebirth of the idea of orbits and it is important not to be so clever as to forget what took a lot of effort to put into your 20/20 hind-sight!] These "Epicycles" executed uniform circular motion as they went around the concentric spheres "Deferents" to which they were attached.

    As the centre of the epicycle moves around the deferent at constant angular velocity, the planet moves around the epicycle, also at constant angular velocity. But the apparent position of the planet on the celestial sphere (indicated by the line drawn from the earth through the planet)appears as the blue line.

    Much edited by me from original material: http://csep10.phys.utk.edu/astr161/lect/retrograde/aristotle.html All of it excellent if rather wordy.

  31. S***y f******g Opera coding once again make a perfect FAIL on everything I do.Edit:End quote before new code (image in this case) begin quote after said code.

  32. I can't help thinking that if the use of epicycles was reintroduced to the internet, we would be able to understand the solar system a lot more easily.And with that, the behaviour of earth's systems!

  33. Kepler believed in the Copernican system. Against his own will, he was forced to the conclude that the orbits of the planets were not circles but ellipses.The Martian orbit was the most elliptical of the planets for which Brahe had extensive data. Thus Brahe gave Kepler the data that would allow him to banish Brahe's own theory.1. For an ellipse there are two points (called foci) The twin radii of an ellipse are best demonstrated with some string and two nails hammered into a board.Place the pins through the ends of the string. Pull the string tight with a pencil so that the pencil point draws on the board. Move the pencil as far as you can in the string.Notice how the angle of the string changes as the lengths of string either side of the pencil changes.The shape you draw using just one nail is called a circle. With two nails it is an ellipse.2. Try it with different distances between pins and try it with more than two of them.3. How does the string's length control things?Show me!!!

  34. Precise Observations before the Invention of the Telescope:Tycho Brahe made important contributions to astronomy by devising the most precise instruments available before the invention of the telescope.Brahe made his observations from Uraniborg, on an island in the sound between Denmark and Sweden called Hveen.He compiled extensive data on the planet Mars, crucial to Kepler in his formulation of the laws of planetary motion, demonstrating that the orbit of Mars was an ellipse.He made the most precise observations that had yet been made by devising the best instruments available before the invention of the telescope. His observations of planetary motion, particularly that of Mars, provided the crucial data for later astronomers like Kepler to construct our present model of the solar system. He made observations of a supernova (literally: nova= "new star") in 1572 a "star" that appeared suddenly where none had been seen before, and was visible for about 18 months before fading from view.Brahe's meticulous observations showed that the supernova did not change positions with respect to the other stars. Therefore, it was a real star, not a local object. This was early evidence against the immutable nature of the heavens, although Brahe did not interpret the absence of parallax for stars correctly, as we discuss below. By measuring the parallax for a comet, he was able to show that they were further away than the Moon. It was very difficult to ascribe uniform circular motion to a comet. He made the best measurements that had yet been made in the search for stellar parallax. Upon finding no parallax for the stars, he (correctly) concluded that either the earth was motionless at the centre of the Universe, or the stars were so far away that their parallax was too small to measure. Brahe did not believe that the stars could possibly be so far away and so concluded that the Earth was the centre of the Universe and that Copernicus was wrong. He set Kepler the task of understanding the orbit of the planet Mars, which was particularly troublesome. It was the Martian data that allowed Kepler to formulate the correct laws of planetary motion.

  35. The Earth-centered Universe of Aristotle and Ptolemy held sway on Western thinking for almost 2000 years. Then, in the 16th century a new {an oriental} idea was proposed by the Polish astronomer Nicolai Copernik:"On the Revolutions of the Heavenly Bodies"Copernicus proposed that the Solar System is heliocentricThe system led to a simple explanation of both the varying brightness of the planets and retrograde motion: They are not always the same distance from the Earth. Copernicus could not question the assumption of uniform circular motion. Thus, in the Copernican model the Sun was at the centre, but the planets still executed uniform circular motion about it. As a consequence, the model could not explain all the details without epicycles.His ideas remained obscure for about 100 years after his death. But Kepler, Galileo, and Newton would build on the heliocentric Universe of Copernicus and produce the revolution that would sweep away completely the ideas of Aristotle and replace them with the modern view of astronomy and natural science.The idea of Copernicus was not really new! A sun-centered Solar System had been proposed as early as about 200 B.C. by Aristarchus of Samos.If the Earth actually spun on an axis (as required in a heliocentric system to explain the diurnal motion of the sky), why didn't objects fly off the spinning Earth?[This vaporous nonsense still performs a useful function for Meteorology but these days it is called Coriolis Effect]If the Earth was in motion around the sun, why didn't it leave behind the birds flying in the air? If the Earth were actually on an orbit around the sun, why wasn't a parallax effect observed?That is, stars should appear to change their position with the respect to the other background stars as the Earth moved about its orbit.

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