All right, so now I'm back to what happened in Europe after 1450. There were two Germans, Georg Peuerbach who lived to be 40, no, 38 years old and a student of his 13 years younger than him named Johannes Muller who got very preoccupied in the mid-15, excuse me, 1450s with astronomy.

Mueller's Latinized name is Regio Montonus because he was born in Konigsberg, the City of Kings. Regio Montonus is the Mountain of Kings. Regio Montonus is the key figure In leading into Copernicus. I've marked off some things here, I'll just read them very quickly. This is from a letter, you can see it's Noel Swerdlow publishing this letter.

That I may begin this discourse with the highest starry sphere. Which has thus far afforded the subject of our discussion, I cannot but wonder at the indolence at the common astronomers or our age, who just as credulous women, apologies. Receive as something divine and immutable, whatever they come upon in books either of cables or their cantos, for they believe in writers and make no claim to find the truth.

But what shall I say of the nature of the motion of the eighth sphere which our illustrious Ptolemy concluded to move through one degree and a hundred years but 743 years after him, Al Batani, needless to say Arabic. Through one degree and about 66 years, so that's one example of Regio Montanus, deploring, in this case the Alfonsine tables, other examples.

And therefore, in the computation of the true motion of the sun, there would be an error of about one degree, which is unfitting as it is in giving judgements, casting horoscopes no one should fail to notice an eclipses and other things. Further when the sun is in the beginning of Ares and the fixed ecliptic by computation it will be removed from the equator by about six degrees to the north.

How therefore could we compute the position of the sun in the equator? But enough of these things. Now we go to Mars. Mars was seen to differ in the heavens and in computation by two degrees in relation to the fixed stars and other observations. Remember two degrees is four moon widths.

That's quite substantial. And other observations. At times the difference of this kind of one and a half degree is distinguished and sometimes much less. Now some in describing this error to the epochs of the mean motion have erred beyond reason, for if the error were only such epochs of the mean motions, there should be found a constant difference between the computed position and the true position, which is not found.

We go on and complain some more about Mars. Finally he turns to Venus. I have seen Venus slower in the heaven than the computation that predicted by about three quarters of a degree. And it is also extremely difficult to avoid falsehood in computing its latitudes. You can read the rest of that on your own.

The last one of this. Now as I recall yes it's moon. I have also observed other eclipses differing greatly from computation and duration in the size of the eclipsed part. Constraining which the proper place of speaking a greater length will be elsewhere. And if the moon has an eccentric and a epicycles in a way that has been claimed, it will follow necessarily that in a particular position, the moon appear about four times greater than in another position, everything's being the same condition.

So, this is somebody, the first place I know of, that's crucial statement now. I've already told you I don't know what they studied in Arabic manuscripts. First place I know of where people start singling out the failure of Ptolemaic astronomy away from salient events. That the errors are way past anything like observational.

Okay and Regio Montanus says doing this I think that and I don't recall the date of that letter but it's, he died in, I have to look that up, sorry 1476, he lived 40 years.1436 to 1476. He finished something that his teacher, Peuerbach, had begun a careful Latin translation, and ended up not with the whole Almagest.

It was published as the epitome of the Almagest, by Regio Montanus, which is translation of a good two-thirds, with commentary. Very detailed, very learned commentary. This is the book Copernicus learned astronomy from. As did almost everybody else after the book was published. Now, keep in mind, printing press roughly 1450, he's dying in 1476, so this a young person jumping on the printing press.

He decides to form a project. The project is to print, all in the original Greek. The whole of the Almagest, the whole of Euclid, the whole of Apollonius, the whole of Archimedes. He died before he could do that. But the project continued, and all of them by a century later, were out in the original Greek.

Other things he did, he produced a text in trigonometry that everybody used for the better part of 150 years. And attached to it were a set of trigonometric tables. Now hear this, to seven digits, seven places, every minute of arc. Think of the computational effort. And, shortly before he died, he published Effimerides.

Effimerides are predictions of things that are going to happen astronomically in subsequent years. 800 page Effimerides for the skies, excuse me, it's 900 pages, stretching from 1475 to 1560. What that does for you is a set of predictions that can then be compared with observation and start deciding what's good.

He himself carried out extensive observations that was continued by a protege of his named Walther, and at roughly the time of Galileo, all those observations got published though by then they were a little bit secondary. So it, it is Regio Montanus more than anybody else who sits up cut Copernicus and you'll see that dramatically in coming moments.