The reason they don't "Burn Up" is that Oxygen is a caustic gas ( quite harmful to metals.. ala the reason yer car gets skin cancer
Removing the Oxygen from the atmosphere in the light bulb eliminates the oxidizing affects on the bulb and increases its life span by ALOT!. Also different gasses can be put in to change the way the light behaves ( like Halogen, Xenon, Sodium Vapour)
From what I know the light bulbs are at a vacume but not a total one ( the glass would need to be like 1" thick if it was at -14.7 PSI below sea level pressure) So it may be at a slightly lower pressure, but just filled wit Nitrogen/CO2 or gases that prolong the life of the lightbulb.
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C-ya
Joe - Owner/Editor
www.ProCooling.com
Where the Completely Addicted Come to Cool Off
Somebody set up us the bomb.
[This message has been edited by Joe (edited 12-06-2000).]