View Full Version : Medieval microscopes and telescopes?

Tom Mazanec
2018-Mar-19, 02:58 PM
The Middle Ages had mirrors and lenses. Why did it take so long to invent telescopes and microscopes?

2018-Mar-19, 03:55 PM
A really good question. I dug into this at one point and these seem to be relevant:

- What was new in manufacture in the early 1600s was that eyeglass lenses could be made more precisely and repeatably, in particular so that the region of optical quality (and the same optical prescription) became larger. This fits with the appearance of refractors at multiple places in Europe at about the same time (I long wondered how it was possible that no one had ever put lenses together to make a Galilean telescope...)

- It feels frustrating how many people had considered the "lighthouse problem", the opposite of a prime-focus reflecting telescope, for centuries. But AFAICT none wrote about what happened if the rays went the other way into a parabolic mirror. With hindsight, the first telescope that could have been made by stranded time travelers would probably have been an obsidian-mirror reflector, with long enough focal length that someone's eye could act as the eyepiece peeking around the edge of the tube and getting the beam a bit off axis. (Obsidian makes pretty good telescope mirrors except for being a very hard glass to work, and having notoriously low reflectivity when to coated with a metallic film ). Diocles in ancient Greece, and al-Haytham a millennium later, studied the focal properties of a paraboloid (I dunno, maybe a fixation the idea of light as proceeding from the eye held up reversing the perspective?). A glass sphere masked to a radial zone might be enough to act as a refractor objective.

- It seems possibly (though of course there is no evidence) that isolated, serviceable telescopes might have appeared almost any time in the last millennium, but individually and with their production kept as a trade or state secret. (I keep thinking of all the predecessors of the Antikythera mechanism of which we have no record).

With all this hindsight, there do seem to be missed opportunities -Al-Haytham invented the cmerar obscura around AD 1100, only one lens short, and Robert Grosseteste wrote circa AD 1220 that he knew how to make what certainly sounds like a telescope, as did Roger Bacon slightly later.

2018-Mar-21, 03:59 PM
The construction of a microscope was delayed due to a lack of petroleum jelly: https://boyslife.org/hobbies-projects/projects/200/make-a-microscope/

2018-Mar-21, 05:49 PM
there was a commentry years ago that in China and Japan they had glass but never developed optics, choosing jewellery instead. Now I remember that stained glass windows were all the rage in the mediaeval period and there was considerable skill and art in making clear and coloured glass. Obviously generating clear glass is a major chemical achievement but also requires good starting materials. The glass spherical bead of Leeuwenhoek was not the first such bead, the Romans could have made that, but he is credited thanks to his painstaking drawings made using his simple microscope.