Cart before the horse ?

[CraigD]

The data was about spiral galaxies with too many turns and superstructure, both of which needed to be much older than the age of the universe predicted by current theories. The machine was broken. I figured science would throw out the old broken prototypes into the circular file and go back to the old drawing board.

Indeed, the machine (prevailing theories of cosmology and galaxy formation) was broken, and required rework.

 

Rather than throwing out the whole collection of theories, what’s appears to have been reworked most in the past 15 years is not the estimated age of the universe, but models for galaxy formation. Thanks in part to a lot more simulation power, these models have become much more sophisticated, allowing for the cyclic appearance, disappearance, and reappearance of features such as arms and bars one thought to occur infrequently and for only narrow ranges of initial conditions.

[Ceedee]

I am left wondering what validity any simiulation can have if it is based upon the same fudged data as we base everything else on. I assume logically that the simulation can not know more than we do ( it can only work it out quicker ) and as such it must be fed the same unknowns.

Why are we surprised when simulation develops into something like what we see when it couldnt really develop into anything else.

i do understand that the simulations are great and should we actually get real data to feed into them would be a marvelous tool.

[CraigD]

I am left wondering what validity any simiulation can have if it is based upon the same fudged data as we base everything else on. …

True – if a simulation is based on invented data, its predictions – no matter how accurate the simulation – are inventions with no connection to observed reality.

 

In the case of galaxy formation simulations, the data doesn’t need to be completely invented. We can observe a remote galaxy well enough to make a pretty good estimation of the total number, mass, distribution, and motion of its stars. We can observe multiple galaxies with similar properties at different distances, showing us what similar galaxies look like at different times. If our observations and the estimates based on them are correct, and the laws of physics are the same far away as they are here – 2 critical but reasonable assumptions – then we can use or model to infer data that we can’t observe - namely, the mass, distribution, and motion of matter we can’t directly observe.

 

Modeling is a complicated discipline with a high risk of artificial error, so model data and results need to be published and reviewed. If multiple, independently designed models confirm one another, our confidence in the results is increased.

 

“Fudging” implies altering observed data to make it agree with a model. Using a model and observed data to infer data that can’t be directly observed isn’t fudging. Because astrophysical models usually use published observational data, “fudging” – altering – the data is difficult to slip past any peer review. So, IMO, as galaxy formation models improve, the validity of their predictions improve.

[InfiniteNow]

I would like to thank the good Doctor for spending some post time reminding us all that he is, in fact, a good guy. Cheers, and nice post. :doh:

[Ceedee]

"We can observe a remote galaxy well enough to make a pretty good estimation of the total number, mass, distribution, and motion of its stars. We can observe multiple galaxies with similar properties at different distances, showing us what similar galaxies look like at different times"

 

This is where my problem arises. Can we extrapolate like this when as far as i can gather those basic facts are best guesses and not facts. We dont even know how our own galaxy works let alone another. We base mass on guestimates derived from luminosities and suchlike which are far from being facts. I understand that we have to pick something to work from but as i have said before we tend to extrapolate from these guesses to incredible extremes and then pronounce that we understand matters that we really dont.

 

or maybe im missing something.

[Tormod]

or maybe im missing something.

 

You are missing a lot. The weight of a galaxy is not a fixed number, and as such is relatively non-interesting to get accurately. However, the way to measure something's mass is to observe how it affects objects around it. We can also observe how a galaxy rotates and make estimates on how many stars there are.

 

Here is a well-written text on the subject of how a galaxy is studied. It is from 2000, but still valid on most counts.

 

http://www.maa.mhn.de/Scholar/Interstmat/ismglxyb.html

[Ceedee]

excellent link tormod thank you.

 

thats one of the few articles i have read that doesnt gloss over these unknowns and rather accepts and acknowledges that theres a lot of guesswork and estimates going on. These type of texts are what i like as they present a truer picture of what we know / dont know rather than claiming its all fact. This in turn prevents layman such as i from assuming we know more than we actually do, and ,in pointing out the "guesses" ,lets me decide for myself what validity this information can have when taken further down the line.

 

i look forward to finding more articles such as that one.

[HydrogenBond]

Part of the problem is that if one starts with nebulous foundation premises and then logically extrapolates from there, the subsquent logic can be perfect, but any extrapolation from a fuzzy foundation propagates the fuzzy until it can become an illusion that appears logically consistent.

 

For example, at one time it was believed that the earth was flat. Based on this assumption, the middle ages mind would logically extrapolate. The subsequent logic was good, but their conclusions would always come out as a logical illusion. This logically consistent illusion prevented exploration for hundreds of years until Columbus. He was considered crazy because everyone knew he would fall off the edge. The Queen of Spain was probably taken more by charm then by the logic of contemporay reasoning. She sponsored him and Italy lost their chance to be the new world commerce superpower.

 

Applied science is probably purer than theoretical science because the proof is in the puddy not in the ingredients. Simulation is not applied science since one can start with tooth fairies and gum drops and still make it come out the way you want.

[Tormod]

For example, at one time it was believed that the earth was flat. Based on this assumption, the middle ages mind would logically extrapolate.

 

Actually this is not a good example. There is very little evidence that people in the middle ages actually believed the Earth to be flat, actually historical evidence points to the opposite. We know that the Greeks used the difference between the length of shadows cast by poles in two different areas to calculate the circumference of the Earth before year 1.

 

Here is a brief background.

 

http://www.phy6.org/stargaze/Scolumb.htm

[Doctordick]

There is very little evidence that people in the middle ages actually believed the Earth to be flat, actually historical evidence points to the opposite.

You are absolutely correct; however, there is some evidence that it was known that people had been to the other side of the atlantic prior to Columbus. That could very well have influenced Columbus's estimates. Some of you might find it interesting to read 1421 a rather interesting book.

 

Have fun -- Dick

[Qfwfq]

I third Tormod.

 

Nicolaus Copernicus (1473-1543), in 1492 he was already nearly 20, "De Revolutionibus Orbium Caelestium" first published in 1543 but he had written it long before. In those days the ptolemaic doctrine had long been radicated and was also the doctrine supported by the peripatetics. Aristotle had long been a figure of absolute authority for natural philosophers. Only simple people didn't realize the world wasn't flat.

 

I don't agree though that Columbus' estimate could have been influenced by previous transatlantic journeys simply because he wasn't aware of them and very few Europeans were. Also, he would not have underestimated the globe's size had he known. When he reached the islands off America and returned home he believed he had been to India, that's why the natives were called Indians. It was Vespucci that realized the mistake and that's why the new world was called America.

[Doctordick]

I don't agree though that Columbus' estimate could have been influenced by previous transatlantic journeys simply because he wasn't aware of them and very few Europeans were.

I have read somewhere (something I read probably thirty or forty years ago) that Columbus actually talked to one of three survivors [i don't know if "survivors" refers to surviving the trip or to surviving to Columbus' time] who had been storm driven west for some substantial time before landing at a place unknown to them. The return trip east was so difficult and long that many of the crew were lost. Where did that storm drive them?

 

Gavin Menzies claims that he found, in Columbus's records, a reference to a storm driven ship which landed at the Isle of the Seven Cities in the time of the Henry the Navigator and were welcomed by the inhabitants and invited to attend services in good Portuguese. According to Menzies, the story is corroborated by the sixteenth-century Portuguese historian Antonio Galvao with the following passage:

So in this year, also 1447, it happened that there came to Portugal a ship through the streight of Gibraltar, and being taken with a great tempest, was forced to run westward more willingly than the men would [wish], and at last they fell upon an island which had seven cities and the people spake the Portuguese tongue, and they demanded if the Moors did yet trouble Spain ... The boatswain of the ship brought home a little of the sand, and sold it unto a goldsmith of Lisbon, out of which they had a good quantity of gold.

 

Dom Pedro understanding this, being then governor of the realm, caused all the things thus brought home, and made known, to be recorded in the House of Justice.

 

There be some that think that those islands whereupon the Portugals were thus driven were the Antiles or New Spain, alleging good reasons for their opinion.

Apparently from a translation of Galvao by H. Harrisse in 1892. Furthermore, from my personal readings of history, I am sure there were a number of interactions across the Atlantic shortly before Columbus's trip. He certainly had heard enough rumors to know something was out there.

 

In 1267 Jamal al-Din, a Persian astronomer presented Khubilia Khan with a number of astronomical items as gifts. Among them was a globe of the earth. Apparently it had on it a fairly accurate map of Asia and Europe with little information on Africa and nothing but a few random islands covering the rest of the seas. Adding this to the history of Columbus's arguments to the Spanish crown, it was the idea that one could sail west to China which was under discussion; not that there was nothing out there. I suspect the official position was "there wasn't anything valuable out there!"

 

Have fun -- Dick

[Qfwfq]

:hihi:

 

Uh, if this Antonio Galvao claim were true, it would hardly have been unknown in the days of Columbus. Why then did only he go down in history? In the sixteenth century the eastern Americas were already being explored. If that Portuguese communtiy was long enouhg established that they remembered the Moors, why was no trace of them found? Google finds hits for "António Galvão, Tratado dos Descobrimentos" but I believe a serious historian could easily find sure facts in contradiction with the writings of this guy. Sure he wasn't a 16th century crank?

 

Recently there has been some evidence although not quite certain that, some time before 1492, a Chinese navigator sailed the world mapping most of the coasts, including American. The Navigatio Brendani was considered pure folklore, it had been handed down by word of mouth for generations before being written, until some pointed out that many of the incredible depictions could have been based on facts such as the volcanic activity in Iceland. In Europe no one knew of the continent and Columbus fully expected to reach Asia, everybody believed he had reached India until Vespucci discovered the Pacific.

 

The official position wasn't "nothing valuable" it was a matter of whether it could be a more practical way to Asia than those in use. A better way to Cathay was considered a great advantage sure indeed, circumnavigation of Africa marked the beginning of decline for the Italian Maritime Republics as well as the middle eastern countries.

[Doctordick]

Qfwfq, when you first responded to my posts I had hoped that I had run across an intelligent educated individual who could provide me with active and rational discourse. At this point it appears that I was quite wrong. :gift:

The official position wasn't "nothing valuable" it was a matter of whether it could be a more practical way to Asia than those in use.

You are apparently a complete sucker for the official academic line. If you had any understanding of history at all, you would certainly comprehend the fact that almost all discoveries in the history of science (and that would be everything from geography to nuclear structure) were seen because the observer failed to accept the academic line as unbiased truth! Do you really think that the intelligentsia of Spanish maritime authority would have opposed financing an experimental trek to the west if they thought anything valuable would come of the trip? The distance to China was well known many years before Columbus and it was only Isabelle's ignorance which ended up financing the trip. As I understand it, Columbus was eventually imprisoned because of the fraud he had exercised on the Spanish government. :steering:

 

You ought to read Gavin Menzies treatise; at least try to think things out for yourself. :hyper:

 

Have fun -- Dick

[ughaibu]

http://www.colostate.edu/Depts/Entomology/courses/en570/papers_2000/wells.html

[ingannilo]

Let go the notion of truth as an establishment of fact and more of something that cannot be argued against; accept the immovable center of your existance to be you and that everyone's varies to an infinate degree.

 

Carts lead horses to the tops of skyscrapers, and the response to every answered question.

 

Again, I achknowledge that it's pretty hard to take my posts seriously with their spelling errors, but we all do our best, and a cut/paste to google doesn't mean anything to me if the point still gets through.

 

my two cents.

John

[InfiniteNow]

Qfwfq, when you first responded to my posts I had hoped that I had run across an intelligent educated individual who could provide me with active and rational discourse. At this point it appears that I was quite wrong. :steering:

Oh well... I guess the simple courtesy and respect for fellow humans couldn't last long... What was that about old dogs and new tricks???