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From: Jeroen Belleman <jeroen@nospam.please>
Newsgroups: sci.electronics.design
Subject: Re: how the laser happened
Date: Tue, 25 Jun 2024 23:20:55 +0200
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On 6/25/24 22:46, Phil Hobbs wrote:
> Jeroen Belleman <jeroen@nospam.please> wrote:
>> On 6/25/24 12:50, Martin Brown wrote:
>>> On 21/06/2024 14:05, john larkin wrote:
>>>> There was a thread somewhere above about photon wave/particle duality.
>>>>
>>>>
>>>> This is worth reading:
>>>>
>>>> https://www.amazon.com/How-Laser-Happened-Adventures-Scientist/dp/0195153766
>>>>
>>>> Einstein, in one of his fits of genius, predicted in around 1916 that
>>>> under the right conditions, a photon could pass by an excited atom and
>>>> the atom would kick in another photon, or add to the wave amplitude,
>>>> depending on how you feel about these things. He called it stimulated
>>>> emission. He also declared that the laws of thermodynamics made this
>>>> effect impossible to use in practical situations.
>>>>
>>>> In 1951, Charles Townes invented a work-around trick and built the
>>>> maser, a gaseous microwave oscillator. His superiors thought he was
>>>> crazy to dispute Einstein and almost threw him out of grad school, but
>>>> it worked.
>>>
>>> More interesting still nature beat him to it.
>>>
>>> The natural source W3(OH) dense molecular cloud which has hydroxyl
>>> masers pumped by UV bright young stars embedded in it.
>>>
>>> Very bright ultra narrow band point sources on a fuzzy nebulous object.
>>>
>>> https://articles.adsabs.harvard.edu/pdf/1981MNRAS.194P..25S
>>>
>> [...]
>> The idea has been around for a while. Scifi writer Larry Niven
>> used it in his Ringworld series of stories. (A ringworld meteorite
>> defence system strips bare the hull of a space ship on a collision
>> course with the ringworld surface.)
>>
>> Jeroen Belleman
>>
> 
> Of course the Ringworld is dynamically unstable, so it wouldn’t matter that
> much if it got hit. ;)
> 
> Cheers
> 
> Phil Hobbs
> 

Yes indeed. Niven invented a plot twist to fix that in "The Ringworld
Engineers". Dyson spheres aren't stable either. We're making some
headway into making a Dyson swarm though. ;-)

Jeroen Belleman