(urth) Travelling North aka miscellaneous thoughts on Wolfe

[Jeff Wilson]

On 6/9/2010 10:38 AM, Gerry Quinn wrote:
> I know that even 'hard' SF writers generally get a free pass when it
> comes to FTL travel. But the method described in 'Urth of the New Sun'
> has two problems with it.
>
> First, there is the usual issue of travelling faster than light. Special
> relativity is well established, and while it could be replaced by a new
> 'aether' theory, any such theory would have the same issue with a
> maximum speed. We regularly push stuff to >99% of light speed and we
> know what happens.
>
> Secondly, the 'tacking' method of travelling faster than the wind works
> for sailboats. But the analogy between wind and light radiation doesn't
> hold up because light does not exert pressure in directions orthogonal
> to its direction of travel, as moving air does.

That's not entirely correct; if the light is reflected at an angle, it 
imparts momentum at an angle normal to the reflecting surface. For 
example if light traveling due north strikes a mirror facing SW and is 
reflected to the west, the mirror is pushed NE. This sort of thing 
really happens, and produces a measureable effect on natural and 
artificial satellites _over_a_period_of_years_.

The trick then is not how The Ship is propelled, but rather how The 
Ship's inertia is nullified to allow this 
more-feeble-than-a-thousand-year-old-butterfly push to make it 
accelerate so quickly.

-- 
Jeff Wilson - jwilson at io.com
IEEE Student Chapter Blog at
< http://ieeetamut.org >