copernicus challenged the aristotelian model of a geocentric universe.
copernicus challenged the aristotelian model of a geocentric universe.
who challenged the aristotelian model of a geocentric universe?
copernicus
showing that the sun rotated had two effects. firstly, it showed that the traditional aristotelian model of the universe must be wrong, because that model assumed that the sun had only a diurnal (daily) motion around the earth, and not a rotation on its own axis. secondly, it showed that there was nothing necessarily unusual about rotation of a body in space. in the aristotelian system, night and day were explained by the sun moving round a static earth. for copernicus' system to work, there had to be an explanation for why half the earth was not in permanent daylight, and the other in permanent darkness, as it completed its annual motion around the sun. this explanation was that the earth rotated on its own axis once every day. however it was very difficult to prove that the earth was rotating, so to show that the sun rotated made the copernican model at least more plausible. while the rotation of the sun did not prove copernicus right, it proved his opponents wrong and made his ideas more likely to be true.
letters on sunspots
anagenesis suggests that evolutionary changes can occur in a species over time to a sufficient degree that later organisms may be considered a different species, especially in the absence of fossils documenting the gradual transition from one to another. this is in contrast to cladogenesis—or speciation in a sense—in which a population is split into two or more reproductively isolated groups and these groups accumulate sufficient differences to become distinct species. the punctuated equilibria hypothesis suggests that anagenesis is rare and that the rate of evolution is most rapid immediately after a split which will lead to cladogenesis, but does not completely rule out anagenesis. distinguishing between anagenesis and cladogenesis is particularly relevant in the fossil record, where limited fossil preservation in time and space makes it difficult to distinguish between anagenesis, cladogenesis where one species replaces the other, or simple geographic immigration/emigration patterns. recent evolutionary studies are looking at anagenesis and cladogeneis for possible answers in developing the hominin phylogenetic tree to understand morphological diversity and the origins of "australopithecus anamensis", and this case could possibly show anagenesis in the fossil record.
anagenesis