Path: ...!feeds.phibee-telecom.net!3.eu.feeder.erje.net!feeder.erje.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Bill Sloman Newsgroups: sci.electronics.design Subject: Re: how the laser happened Date: Wed, 26 Jun 2024 14:04:56 +1000 Organization: A noiseless patient Spider Lines: 81 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Wed, 26 Jun 2024 06:05:02 +0200 (CEST) Injection-Info: dont-email.me; posting-host="4e0501dee833d2c81811b202a133eb1c"; logging-data="2077234"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19giuGlrAORCoBScFlSXXz940F9eXtT6iY=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:+qJuS0XTqnsIDvg7RqsLa3XfjNM= Content-Language: en-US X-Antivirus-Status: Clean In-Reply-To: X-Antivirus: Norton (VPS 240625-10, 26/6/2024), Outbound message Bytes: 4475 On 26/06/2024 7:43 am, Joe Gwinn wrote: > On Tue, 25 Jun 2024 08:19:03 -0700, john larkin wrote: > >> On Tue, 25 Jun 2024 11:50:05 +0100, Martin Brown >> <'''newspam'''@nonad.co.uk> 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 >>> >>>> What's interesting is that any decent neon sign shop could have built >>>> a HeNe laser in 1920. >>> >>> They would have needed to make the mirror just cavity right though. >> >> I know a guy who built a HeNe. It wasn't hard. >> >> T> >>> A nitrogen gas UV pulsed laser is possible just by getting the pressure >>> right and creating the population inversion. Self starting - there was >>> a (dangerous) experiment in SciAm Amateur Scientist column to do it >>> sometime in the 1970's. June 1974 in fact - cover shows the BZ reaction. >>> >>> https://www.scientificamerican.com/article/the-amateur-scientist-1974-06/ >>> >>> The failure to discover fullerenes in soot was a lot more surprising >>> since they were there all the time since the invention of fire just >>> waiting to be extracted by benzene. For a long time space dust had a >>> spectrum that could not be reproduced on Earth by any known compound. >>> >>> Much like Helium was in the sun but more pervasive. >> >> Too many powerful old farts declare things to be impossible. > > . > > This is often paraphrased as "Science progresses one funeral at a > time". https://en.wikipedia.org/wiki/Planck%27s_principle The irony is that Max Planck wasn't that kind of powerful old fart. He published Einstein's four 1905 papers without bothering to get them refereed. https://en.wikipedia.org/wiki/Annus_mirabilis_papers Science does have a hierarchy problem, but it frequently surmounts it. -- Bill Sloman, Sydney -- This email has been checked for viruses by Norton antivirus software. www.norton.com