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Author Topic: How small a spot could you focus from earth to the moon using a laser?  (Read 2491 times)

Offline thedoc

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With the best laser, how small a spot could you focus from earth to the moon?
Asked by Oilinky, via Twitter          
« Last Edit: 15/06/2010 17:58:01 by BenV »


 

Offline thedoc

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We posed this question to Graeme Hirst from the STFC Central Laser Facility...

Graeme -   You're trying to fight a thing called diffraction and that depends on how big you can make your laser beam down at the earth.  A back of the envelope calculation - laser light spreads out about one wavelength in 10 metres.  Its 400,000 kilometres to the moon.  Youll probably get something about 40 metres across [on the moon].  As a football metaphor, wed be looking at something about twice the size of the 18 yard box.


               
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« Last Edit: 15/06/2010 17:58:25 by BenV »
 

Offline syhprum

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I always understood that the ranging laser that utilises the reflectors placed on the moon by the Apollo astronauts has a spot size of about 4 Km but I am sure this is not the ultimate that can be achieved.
 

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