Anders Sandberg (
Tue, 28 Jan 1997 18:26:49 +0100 (MET)

On Mon, 27 Jan 1997, Mike Cowar. wrote:

> Keep in mind this is speculative.
> I do not claim to be an expert.
> Gravity curves light.
> In order for light to be curved,
> it must be affected by friction.
> Educate me.

Neat, but it doesn't match known physical facts (UV light moves just as
fast as any other kind of light in vacuum; anything else would have been
noticed by optics researchers long ago).

One way to undertand the curving of light is to say it always moves in a
straight line - locally. It is just that in curved space (where gravity
causes the curvature) there are no global straight lines; you can draw a
straight line on a paper which is straight both locally and along its
entire length, a curve on a sphere can be straight locally (look at the
equator, the meridians or any oher great circle) but will in the long run
be curved. These "locally straight" curves are called geodesics.

There is no force making the light bend, it is the *direction* that changes
from place to place; the light is moving straight forward.

Anders Sandberg Towards Ascension!
GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y