To anyone who doesn't use abstract mathematics on a daily basis, the concept of an imaginary number sounds absurd. We can't use them to count things, as we can with natural numbers.
If we see green apples fall from a tree every day, why should we reason inductively and conclude that every apple that falls from the tree will be green? Why not conclude instead that the next apple to fall from the tree will be red?
“To those who are trained in science, creationism seems a bad dream, a sudden coming back to life of a nightmare, a renewed march of an Army of the Night risen to challenge free thought and enlightenment.” - Isaac Asimov
It is not difficult to find online forums and blog posts that proclaim facts and arguments as if they were certain. People of all philosophical alignments will do this. Theists will proclaim what they believe to be indisputable facts like: "Something must have caused the Big Bang", and atheists are often guilty of prophetically declaring their favourite origin story for the universe: "Quantum fluctuations produced the universe" or "Many-worlds explains fine-tuning".
There is a split in the philosophical community with regards to this issue. By and large, the majority of philosophers of physics claim that space and time are real and important entities, but there is a small faction who maintain that space and time are just useful theoretical constructs that don't have the independent existence we sometimes attribute to them.
We can get most of the way to deriving the constancy of the speed of light just from the Principle of Relativity alone. In other words, the speed of light being constant is just a consequence of the laws of physics being the same in all inertial frames.
Although the purpose of the Drake Equation is to estimate the number of alien civilisations with which we could potentially make contact, in truth we have absolutely no idea how many alien civilisations are out there.
It is almost certainly the case that time behaved differently at the Big Bang singularity to how it does now, and that it is not possible to define a time "before the Big Bang". Defining a time before the universe would be nonsensical anyway because time is a part of the universe, not external to it.