[ExI] Virtual Reality is where the aliens are

Anders Sandberg anders at aleph.se
Sat Sep 5 21:45:39 UTC 2015

[Delayed posting]

On 2015-08-29 21:04, Rafal Smigrodzki wrote:
> On Sat, Aug 29, 2015 at 1:24 PM, Keith Henson <hkeithhenson at gmail.com 
> <mailto:hkeithhenson at gmail.com>> wrote:
>     *IF* a species was inclined to spread out to the stars, the obvious
>     way to travel is light sails pushed by laser cannons themselves
>     powered by stars.  The spill around the light sails would be visible
>     clear across the visible universe.  We don't see such or at least have
>     not yet.
> ### This image gives me the goosebumps: Sailing through the darkest 
> night on pillars of burning light to claim the farthest shores in the 
> name of life - what could be more poetic?

It is beautiful.

However, I think the light overspill Keith mentions may not be present. 
Eric and me worked out a laser-propelled probe that has an extensible 
"optical power cord cord". Imagine it trailing an optical fiber 
(somehow) delivering the laser light for launch: no diffraction-limit 
caused overspill, you can maintain a tight focus on the probe until the 
fiber cannot be extended more. But an optical fiber is just glass and 
emptiness: it can be replaced with a series of thin lenses separated by 
space, and this arrangement can e expended quite far. The final step is 
to realize that it is all about interference patterns for your 
monochromatic light, and they can be Fresnel structures. So in the end 
the probe gets launched with little overspill at a huge acceleration, 
coasting quietly. It is braking that can be visible, but if the 
acceleration is decent the chance of seeing anything is low.

Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University

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