Why this expedition? To prove this “proportional glass” could be built. Was built. Bourne (though probably more correctly, a contemporary) has not gotten credit for the invention of what may be one of the greatest military and scientific inventions of all time. You’d think a careful description of a working telescope would be sufficient evidence of its invention. However, critics do not believe the design worked (my video should convince you otherwise!) and that the materials of the day would not have sufficed to make such a device. I wish to show it works even with the materials of the day. And I’m sure I can do it. Here’s why — the crazy design — and it is crazy by modern standards, suggests the Elizabethan’s knew the limitations of their own materials. For instance, it’s lens of 12 to 18 inches! That’s enormous! Big because the imperfections of the glass will average out over the huge face of glass. It was 1/4 inch at its thickest point, because the glass of the time wasn’t so good – they didn’t want light hanging around in there getting all blurry. A big f/ number – for more forgiving optics. It all adds up. Here is another clue the perspective glass part worked, from one of my heroes, William Shakespeare, in Richard II, written in 1595:
Each substance of a grief hath twenty shadows,
Which shows like grief itself, but is not so;
For sorrow’s eye, glazed with blinding tears,
Divides one thing entire to many objects;
Like perspectives, which rightly gazed upon
Show nothing but confusion, eyed awry
Think about it. William Shakespeare is writing about the most critical part of this telescope in the same era! He notes if one looks at a perspective (the big lens of the proportional glass) just right, it’s image is confusion (that’s how things look when you look at a lens at its focal point). Presumably, if NOT viewed rightly upon, the image is clear!
See? Perspective glasses were common enough for the Bard to refer to them for the audience. People used them; they knew about them.
If you don’t trust me, trust William Shakespeare! The Bard don’t lie.
You want more? I got more. Take a seat. So I’ve convinced you that the big perspective glass lens was available. What about the concave mirror?
Ever heard of master painter Jan van Eyck? He was able to generate photo real paintings in a time when photo real might have been a surprise – in the 1400’s. Checkout Portrait of a Man.
Pretty nice… kind of makes one think of Vermeer centuries later. You think van Eyck might have known a thing or two about optics like Vermeer did … gaze upon this for a moment … look in the middle…
What you spy there is a convex mirror. You flip that around, and you have a concave mirror – the other half of the Bourne telescope a CENTURY before Bourne’s design.
You know Jan van Eyck wouldn’t lie. Well, maybe he’d fudge the truth when painting your lovely face or flat tummy, but not about the mirror in the background.
Shakespeare has a perspective glass; Van Eyck has a nice mirror. Bourne tells us if you look at the perspective glass with the mirror, you create a ‘proportional glass.’ Why doubt this?
If one guy says he has peanut butter, and another guy says he has jelly …. it’s not much of a stretch to believe a third guy if he said he made a sandwich. Yet few believe Bourne made his sandwich.
Credits:
“Portrait of a Man by Jan van Eyck-small” by Jan van Eyck (circa 1390–1441) – Selected work 1 from Self Portrait: Renaissance to Contemporary (Anthony Bond, Joanna Woodall, ISBN 978-1855143579).. Licensed under Public domain via Wikimedia Commons – http://commons.wikimedia.org/wiki/File:Portrait_of_a_Man_by_Jan_van_Eyck-small.jpg#mediaviewer/File:Portrait_of_a_Man_by_Jan_van_Eyck-small.jpg
“Van Eyck – Arnolfini Portrait” by Jan van Eyck (circa 1390–1441) – Web site of National Gallery, London. Licensed under Public domain via Wikimedia Commons – http://commons.wikimedia.org/wiki/File:Van_Eyck_-_Arnolfini_Portrait.jpg#mediaviewer/File:Van_Eyck_-_Arnolfini_Portrait.jpg