Uranus and Neptune

It's because the sun isn't remotely a point source.

You can make the rays from any point parallel, but you can't make the rays
from different points on the Sun parallel to each other; the Sun has a
minimum divergence angle due to it's finite size; and imaging optics can't
change that.

On 14 May 2012 20:39, brooksn wrote:

> Ok, tried looking this up before asking. Why don't lenses and mirrors
> effect angular spreading? They obviously do in short distances, ie the
> ants I fried as a kid on my drive way, or the parabolic troughs used for
> solar power generation in the SW U.S.
>
> So why wouldn't it work, to at least some degree, for longer distances? I
> can see if there is some loss or an inability to 'perfectly' align the rays
> to be absolutely parallel. But we don't need perfect, hell if our target
> is an entire moon or planet and its within the solar system...? I'm sure
> I'm missing something, its been awhile since I took college physics.
> Brooks
>
> --- In spacesettlers@yahoogroups.com, Ian Woollard
> wrote:
> >
> > On 14 May 2012 17:50, brooksn wrote:
> >
> > > But the question is, if instead of harnessing power at the source and
> > > 'laser' beaming it to the outer solar system with potential losses due
> to
> > > the loss of focus, if you just passively reflect it and slightly curve
> it
> > > for 'straighter' rays how much improvement can we expect?
> > >
> > Absolutely none. Conventional optics (lenses and mirrors) don't decrease
> > the angular spreading rate at all.
> >
> > More or less all you can do is collect the energy over a bigger receiver
> > area. You also can't use conventional optics to generate a higher
> > temperature than the surface of the sun for related reasons.
> >
> > You can use lasers though, and you can even pump them up with sunlight.
> > They can give you a very narrow beam.
> >
> > --
> > -Ian Woollard
> >

--
-Ian Woollard