Possible to load physics in .world from a .sdf?

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Should it be possible to load physics from a .sdf file to a .world file? I've seen examples of light configurations being loaded to a .world from a model sdf folder* but when I tried to replicate this with physics I get the following error:

Warning [parser.cc:835] XML Element[physics], child of element[sdf] not defined in SDF. Ignoring[physics]. You may have an incorrect SDF file, or an sdformat version that doesn't support this element. Segmentation fault (core dumped)

For context - I'm trying to avoid replicating copying and pasting the same physics information into each .world file I create - if the desired physics requirements changes then I can see this will become tricky to manage.

• e.g. the sun model in http://gazebosim.org/tutorials?tut=pr...