Cosmological models are largely settled on the structure of the very early universe which, moments after the big bang, could be modelled as a smooth, homogeneous fluid.
There are three primary techniques for studying binary star systems. The first technique, direct imaging, allows astronomers to visually resolve both stars in the binary system when they are sufficiently separated.
Earth's geology is uniquely characterised, within the solar system, by its layered differentiation and active plate tectonics, facilitating ongoing crustal recycling.