We cannot explain the phenomenon of gravitational lensing without general relativity, and this is where MOND spectacularly fails.
Evidence-based reasoning underpins all scientific thinking, and it involves testing hypotheses or theories against data. Validating a theory requires replicable measurements from independent groups with different equipment and methods of analysis. Convergence of evidence is critical to the acceptance of a scientific idea.
Scientific knowledge is, by its nature, provisional. This is due to the fact that as time goes on, with the invention of better instruments, more data and better data hone our understanding further. Social, cultural, economic, and political context are relevant to our understanding of how science works.
The early universe was a dusty place, and the UV radiation from the hot, young black holes and stars would get enshrouded by dust, re-radiated, and scattered into red wavelengths like infra-red, causing these objects to remain obscured.
Science is evidence-based and provides a continuing understanding of complex natural phenomena. Our understanding is constantly evolving and continually improving.
We knew from theoretical models that mergers of massive, gas-rich galaxies were more frequent in the past. Now we've found that these mergers are responsible for producing both the nearby obscured quasar population and their distant cousins.
