On 1/26/2014 7:29 AM, Jesse Mazer wrote:
Also note that this is just a quirk of how Schwarzchild coordinates are defined, you can
define other coordinate systems on the same curved spacetime that don't have this issue,
like Kruskal-Szekeres coordinate:
https://en.wikipedia.org/wiki/Kruskal–Szekeres_coordinates#Qualitative_features_of_the_Kruskal-Szekeres_diagram
<https://en.wikipedia.org/wiki/Kruskal%E2%80%93Szekeres_coordinates#Qualitative_features_of_the_Kruskal-Szekeres_diagram>
In KS coordinates the "time" coordinate remains timelike inside the horizon, and the
"radial" coordinate remains spacelike (these coordinates also have the nice feature that
worldlines of light rays always have a 45 degree angle on the coordinate diagrams, just
like in diagrams of inertial coordinate systems in special relativity). And in
principle, even in the ordinary flat spacetime of special relativity you can define some
kind of non-inertial coordinate system where a coordinate that is timelike in one region
switches to becoming spacelike in another, and vice versa--this sort of thing isn't any
type of physical effect, it's just due to the way you define your coordinate system.
Which is also a good illustration of why proper-time (i.e. clock-time along a path) is
regarded as fundamental in physics. It's the same however to label the events with
coordinates, whereas coordinate time can be changed arbitrarily to make the picture simple.
Brent
--
You received this message because you are subscribed to the Google Groups
"Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/groups/opt_out.
