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Author Topic:   archaeology and evolution
caffeine
Member (Idle past 1280 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


Message 91 of 96 (576510)
08-24-2010 10:40 AM
Reply to: Message 90 by Dogmafood
08-24-2010 10:26 AM


Re: Telescopes in ancient times
Indeed it is. I was surprised to hear that the Minoans had telescopes. I presume this is the type of thing that passes for confirmation for some. Is there an image of these lenses anywhere?
Not that I've been able to find. All I came across was brief references in a few articles to a lens found on Mt. Ida from about the 5th century BC, most of which appear to have been copied from each other; but then I found one article about them from the American Journal of Archaeology:
Sines, G. & Sakellarakis, Y. A., Lenses in Antiquity, American Journal of Archaeology Vol. 91, No. 2 (Apr., 1987), pp. 191-196
There are pictures of the the lenses in the article, but it's not open access so I can't see them.

This message is a reply to:
 Message 90 by Dogmafood, posted 08-24-2010 10:26 AM Dogmafood has not replied

Replies to this message:
 Message 92 by nwr, posted 08-24-2010 11:13 AM caffeine has replied

  
nwr
Member
Posts: 6484
From: Geneva, Illinois
Joined: 08-08-2005
Member Rating: 8.7


Message 92 of 96 (576517)
08-24-2010 11:13 AM
Reply to: Message 91 by caffeine
08-24-2010 10:40 AM


Re: Telescopes in ancient times
caffeine writes:
There are pictures of the the lenses in the article, but it's not open access so I can't see them.
It turns out that I can access them, as long as I do it from a university computer. Presumably, our campus library has a subscription to the journal that includes internet access from campus.
The paper indicated that the lenses pictured were concave, so could not be used as magnifiers. That would also make them unsuitable for telescopes. The authors believe that they were used as ear ornaments, and valued as art objects.

This message is a reply to:
 Message 91 by caffeine, posted 08-24-2010 10:40 AM caffeine has replied

Replies to this message:
 Message 93 by caffeine, posted 08-24-2010 11:25 AM nwr has replied

  
caffeine
Member (Idle past 1280 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


Message 93 of 96 (576519)
08-24-2010 11:25 AM
Reply to: Message 92 by nwr
08-24-2010 11:13 AM


Re: Telescopes in ancient times
The paper indicated that the lenses pictured were concave, so could not be used as magnifiers.
Are you sure you'e looking at the same lenses? In the free preview bit of the article, it describes one as 'a plano-convex lens, 8mm in diameter and 4 mm thick, which has a focal length of 12mm, thereby giving a nomlnal magnification of 20X.'

This message is a reply to:
 Message 92 by nwr, posted 08-24-2010 11:13 AM nwr has replied

Replies to this message:
 Message 94 by Coragyps, posted 08-24-2010 11:38 AM caffeine has not replied
 Message 95 by nwr, posted 08-24-2010 12:24 PM caffeine has not replied

  
Coragyps
Member (Idle past 990 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 94 of 96 (576524)
08-24-2010 11:38 AM
Reply to: Message 93 by caffeine
08-24-2010 11:25 AM


Re: Telescopes in ancient times
An 8-millimeter telescope? Wow.

This message is a reply to:
 Message 93 by caffeine, posted 08-24-2010 11:25 AM caffeine has not replied

  
nwr
Member
Posts: 6484
From: Geneva, Illinois
Joined: 08-08-2005
Member Rating: 8.7


Message 95 of 96 (576533)
08-24-2010 12:24 PM
Reply to: Message 93 by caffeine
08-24-2010 11:25 AM


Re: Telescopes in ancient times
caffeine writes:
Are you sure you'e looking at the same lenses?
Good point. I did not read it carefully enough on the first read.
Yes, the paper mentions several lenses, and some of the pictured lenses are plano-convex, so can be used for magnification.
The pictured lenses appear to be from crystals, but the paper also mentions glass lenses that might have been used as magnifying glasses or for igniting fires.
A telescope requires two lenses, one of them with a long focal length, and careful alignment of those lenses. And part of what makes a telescope work is not just the magnification, but the larger amount of light picked up and the greater resolving power dues to a large diameter objective lens.
For evidence of early telescopes, I would want to see evidence of a largish diameter lens and evidence of the apparatus that held the lenses in a suitable alignment.

This message is a reply to:
 Message 93 by caffeine, posted 08-24-2010 11:25 AM caffeine has not replied

  
Brian
Member (Idle past 5215 days)
Posts: 4659
From: Scotland
Joined: 10-22-2002


Message 96 of 96 (577715)
08-30-2010 7:32 AM


article
I was just passing through, but if anyone would like this entire article if you drop me an email bj25 at le.ac.uk I will send you a copy. Remember this is for education purposes only.

  
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