I thought modern astronomy could use a different definition. Starting approximately with the launch of Hubble space telescope - but thanks to not only orbiting instruments, but other advancements as well - astronomy enjoys a development so great textbooks practically need to be rewritten every decade.
I would argue a more relevant landmark would be the introduction of photographic plates. Prior to that astronomers had to sketch what they saw and judge brightnesses qualitatively (usually by comparison to other stars). Photographic plates introduced a whole new level of quantitative rigor to the field.
Or the introduction of the CCD. It produces digital images (which can be analyzed by software automatically), has a linear response to input (so you can reliably measure the brightness of objects), and has much higher quantum efficiency (nearly every photon is detected).
Where to draw the line between modern and pre-modern astronomy is a bit of a subjective question, but there's no doubt that the introduction of the telescope was revolutionary.
Hubble launch approximately coincided - and contributed - to a rapid expansion of astronomical knowledge. All other tools, both Earth-based and space-based, since early 1990-s contributed vast heaps of data which reshaped astronomy - noticeably changing the speed of development, hence the need for distinction.
This is very poor history. Much of the negative characterization of Galileo rests on two incorrect (but commonly believed) assertions:
> Worse than this, [Galileo] placed the Pope’s words on the subject in the mouth of Simplicio, the simpleton, not a smart move.
Galileo probably did not intend to put the Pope's words in Simplicio's mouth. This is a charge that Galileo's accusers leveled, but there's no evidence for it. Galileo had Simplicio voice a common anti-heliocentric argument that didn't necessarily have any particular association with the Pope.
> The Inquisition now produced the written version of the statement that had been read to Galileo by an official of the Inquisition immediately following his interview with Bellarmino expressly forbidding the teaching of the heliocentric theory as fact.
This is a mischaracterization of the Inquisition's 1616 injunction to Galileo. The author here makes it sound like Galileo was simply told not to treat heliocentrism as a fact, but that Galileo was free to entertain the hypothesis. This is a staple of Catholic apologia surrounding the Galileo affair, but it breaks down the second you actually look at the Inquisition's statements on the matter.
First of all, the Inquisition officially declared heliocentrism to be incorrect and heretical:
> Proposition to be assessed:
> (1) The sun is the center of the world and completely devoid of local motion.
> Assessement: All said that this proposition is foolish and absurd in philosophy, and formally heretical since it explicitly contradicts many places the sense of Holy Scripture, according to the literal meaning of the words and according to the common interpretation and understanding of the Holy Fathers and the doctors of theology.
> (2) The earth is not the center of the world, nor motionless, but it moves as a whole and also with diurnal motion.
> Assessment: All said that this proposition receives the same judgement in philosophy and that in regard to theological truth it is at least errouneous in faith.
So it's clear that the Church was not simply saying, "Hey, heliocentrism is just a hypothesis." They took a clear stand that it was incorrect and heretical, because it contradicted Scripture.
Next, this is how the Inquisition described their injunction to Galileo:
> the same Most Illustrious Lord Cardinal warned Galileo that the above-mentioned opinion was erroneous and that he should abandon it;
> [...] ordered and enjoined the said Galileo, who was himself still present, to abandon completely the above-mentioned opinion that the sun stands still at the center of the world and the earth moves, and henceforth not to hold, teach, or defend it in any way whatever, either orally or in writing; otherwise the Holy Office would start proceedings against him.
This is the injunction Galileo was convicted of breaching in 1633. The injunction didn't allow Galileo to treat heliocentrism as a hypothesis. It outright said that heliocentrism was false, and that Galileo was not allowed to teach or advocate it in any way whatsoever.
A third problem with this history is that it massively plays up Tycho's model of the Solar system. Tycho's model was obviously attractive to the Church, as a model that was able to match the data while keeping the Earth stationary at the center of the Universe. The problem with Tycho's model was that it was horribly inelegant. Whereas the basic features of the motion of the planets and Sun across the sky (and sunspots across the disk of the Sun) all appear naturally in a heliocentric system, you have to put them in by hand as separate assumptions in Tycho's model. It looked like an inelegant kludge put together in order to avoid a moving Earth.
Finally, in answer to the comment that Galileo's downfall was his hubris, I'd say that his "hubris" was his belief that he might be allowed to make a forceful argument for the ideas he believed in, without being muzzled by the authorities.
The ruling in 1616 was about the notion that heliocentrism was proved fact, using it as a hypothesis and pointing out it gave better results was fine. See for example the letter from the very cardinal that delivered the verdict to Galileo:
Also, keep in mind that in 1616, how the motion of the Earth would escape the notice from everyone standing on it was a serious scientific challenge, and that predictions of heliocentrism such as stellar parallaxes were not being observed.
> The ruling in 1616 was about the notion that heliocentrism was proved fact, using it as a hypothesis and pointing out it gave better results was fine.
That's incorrect. You can read the 1616 ruling on heliocentrism, which I both quoted from and linked to above. The Inquisition did not mince words in definitively stating heliocentrism to be both false and heretical.
> in 1616, how the motion of the Earth would escape the notice from everyone standing on it was a serious scientific challenge
Even were that true, it would not justify the Church's muzzling of Galileo, nor their ruling that heliocentrism was false because it violated Scripture. However, I think the argument about parallax was less problematic than you think. There was an obvious answer to it, which is that the stars are very far away, and therefore have small parallax motion.
> You can read the 1616 ruling on heliocentrism, which I both quoted from and linked to above.
Yes, but you have to keep in mind it's a translation from 1616's Italian. You can look up the letter where the distinction put into terms like hypothesis and theory is written out clearly.
