Why wasn't the telescope invented earlier?

[quantropy]

There seem to be lots of reasons why one would have expected the telescope to be invented considerably earlier than it was:

• Lenses (of a sort) had been around since ancient times
• Optics was a significant part of the curriculum for centuries before the invention of the telescope
• The idea of such a device had been around at least since Roger Bacon
• Most of all, the military advantages of such a device seem so obvious that you'd have thought those in charge would have put lots of resources into creating one

So why didn't it happen until the 17^th Century?

[himself]

The real Scientific Revolution consisted mainly of shifting science from a knowledge of nature to the domination of nature. (cf. F. Bacon, "The Masculine Birth of Time") No one was thinking of scientia in terms of technological advances. Astronomy was taught as a branch of mathematics, not of physics. Yet when Grosseteste wrote of lenses, he said:
Haec namque pars Perspectivae perfecte cognita ostendit nobis modum, quo res longissime distantes faciamus apparere propinquissime positas et quo res magnas propinquas faciamus apparere brevissimas et quo res longe positas parvas faciamus apparere quantum volumus magnas, ita ut possibile sit nobis ex incredibili distantia litteras minimas legere, aut arenam, aut granum, aut gramina, aut quaevis minuta numerare.
Robert Grosseteste, Bishop of Lincoln, De iride.

Note he also described the microscope. But it is hard to say how Grosseteste could say the Milky Way was made up of innumerable stars without a telescopic device of some sort. But even after its 17th cent. invention was its introduction to China and the Ottoman and Mughal empires by Europeans, it made zero impact in those cultures. Even in Chinese astronomy, knowledge barely budged. But the Chinese word for astronomers was "calander-makers." Even in the 17th century, grinding the lenses appropriately was not an easy task, and many of those who looked through them could see nothing in the restricted field of view available. Impurities in the glass oft gave images a green tinge, or even a halo, and it was not clear whether the rest of the image was any more reliable.

Looking backward, we can ask ourselves "how could they not have seen the way forward?" But hindsight was not then available.

[James Hannam]

Hi there quantropy and welcome.

I am dubious about the medieval precursors to telescopes, but there is goodish evidence that they existed in the first half of the sixteenth century. I came across a reference to one in England, actually well known to historians. I understand there are others.

bedejournal.blogspot.com/2015/04/the-earliest-reference-to-telescope.html

Best wishes

James