by Céline Richard » Sun Dec 05, 2010 11:28 am
This is deeply interesting, thank you a lot!
go back more than about 100 years, and window glass was made by spinning large discs. These were thicker at the center than the edges, so window panes were generally wedge shaped.Glazers usually installed the panes with the thick side down, which is one reason for the belief about glass flowing.
It makes sense a lot
Consider telescope mirrors. They are made of glass, and ground to an accuracy of less than the wavelength of light. If windows could change shape at the rate of a millimeter per century or so (as you might guess looking at cathedral windows), how long would it take for a telescope mirror to become deformed by a few tens of nanometers? Answer: not very long. If telescope mirrors changed shape with time, all but the newest professional telescopes would currently be useless. It's a good thing glass is stable!
Actually, you answered better to my questions than what i have expected to understand. With an accuracy of less than the wavelength of light
Have a very good day, thank you,
Céline
This is deeply interesting, thank you a lot!
[quote] go back more than about 100 years, and window glass was made by spinning large discs. These were thicker at the center than the edges, so window panes were generally wedge shaped.Glazers usually installed the panes with the thick side down, which is one reason for the belief about glass flowing.[/quote]
It makes sense a lot :)
[quote]Consider telescope mirrors. They are made of glass, and ground to an accuracy of less than the wavelength of light. If windows could change shape at the rate of a millimeter per century or so (as you might guess looking at cathedral windows), how long would it take for a telescope mirror to become deformed by a few tens of nanometers? Answer: not very long. If telescope mirrors changed shape with time, all but the newest professional telescopes would currently be useless. It's a good thing glass is stable![/quote]
Actually, you answered better to my questions than what i have expected to understand. With an accuracy of less than the wavelength of light :)
Have a very good day, thank you,
Céline