[ExI] Expansion of the Universe

[Tomaz Kristan]

I am not so sure about the laser part. Probes can do the same. They are a
bit slower, but non the less. They can chop an escaping galaxy in half and
send one half to us.

We can't do it with all the galaxies we see, some are already galaxies too
far away, but with some we can. To get some additional energy we will need
in the future.


On Sun, Dec 30, 2012 at 9:47 PM, Anders Sandberg <anders at aleph.se> wrote:

> On 30/12/2012 17:20, Tomaz Kristan wrote:
>
>> The fastest way to go around should be on the tip of the laser beam,
>> which prints a machine into the dust of a distant planet. A machine which
>> do the same. And so forth, across the galaxies.
>>
>> This should be possible with a smart laser modulation, I think.
>>
>
> Why?
>
> If you use a Gaussian beam with a waist width W it has divergence angle
> lambda/(pi W) where lambda is the wavelength. If you want to manipulate
> atoms, you need a waist width less than a nanometre, and a wavelength of
> the same size. That gives you a divergence angle of around 18 degrees. So
> if you want to build something in the Andromeda galaxy 2.5 million light
> years away, you need a laser aperture about 800,000 light years across.
> Somewhat bigger than our galaxy...
>
>
> --
> Anders Sandberg,
> Future of Humanity Institute
> Philosophy Faculty of Oxford University
>
>
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