How should one look at buddhist mythologies and cosmologies from a scientific perspective Although it could well be that those words were not directly from Gautama himself, yet just in case, assuming Gautama probably wouldn't lie except for educational purposes, how can those rather surreal descriptions of the world, which again share (too) many similarities with the hinduist ones, reconcile with modern science? Should one just regard them as "white lies" so that Buddhism be more easily accepted? How self-consistent are those descriptions anyways?

Also, I read somewhere before that those "insights", including Karma could be partially gained/observed through meditation. How true is this statement in terms of canonical literature reference?
... reconcile with modern science? ...


Modern science is always changing with new theories and discoveries but Buddhism is presented as eternal or timeless which is valid in the past, present and future. Hence these two cannot be fully reconciled. Since is refinement of theories and models getting closer to the truth while Buddhism is based on publically released ultimate realities. As science advance many of the concepts are in harmony and while there are perhaps hardly any scientifically proven discoveries which contradict Buddhism.


  ... which again share (too) many similarities with the hinduist ones ...


If you compare Hindu cosmology with Buddhist cosmology (especially Buddhist cosmology of the Theravada school) there are wast differences. In Hinduism there is a creator but in Buddhism the universe goes through expansionary and contractionary phases.


  ... reconcile with modern science? ...


You cannot. But Buddhism has a theory of cyclical phases of the universe like the big bounce theory, parallel universes (see Parallel universes by Piya Tan), evolution, etc.

Also see: Buddhism and science, Buddhism and Modern Science - by Dr. Granville Dharmawardena (especially the highlighted areas), Is Buddhism the Most Science-Friendly Religion?


  ... including Karma could be partially gained/observed through meditation. ...


Meditation (especially samatha) can lead to psychic powers / supernormal knowledge like clairvoyance (divine eye) which can be give insights to the working of Karma. E.g.


  
    Thus, by means of the divine eye, may I see beings passing away and reappearing, and how they fare according to their karma.’
  


Source: Nimitta Sutta similar passage in Kaya,gatā,sati Sutta, Samanna,phala Sutta, Maha Assa,pura Sutta, Kevaddha Sutta.