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.
We Have No Idea How Many Aliens There Are
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.
Why The Universe Had No Beginning
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.
Universes of Another Kind
There are other kinds of multiverse that physicists discuss, but there's an entirely different kind of multiverse that is discussed by philosophers, not physicists. This is the multiverse of "possible worlds", and was introduced as a semantics that made modal statements much easier to analyse.
Black Hole Fun
If it's possible to have a favourite astronomical object, I'm sure black holes would be fairly high on everyone's list. You can't escape from one, you can't know what's inside one, and they're invisible - what could possibly be more terrifying and exciting to talk about?
Consciousness Has No Place In Quantum Physics
While I will be quick to point out that a theory of quantum mechanics based on consciousness has not been ruled out, it is certainly not the only way to formulate the laws "in a fully consistent way". Pilot wave theory, GRW collapse theory, many-worlds theory, and decoherence theory are all consistent attempts at trying to make sense of quantum mechanics.
Electrons – Waves or Particles?
Embracing wave-particle duality helps us to come to terms with the strange results of the double-slit experiment, but it leaves us with a very confusing picture of what an electron actually is.
The Only Mystery of Quantum Mechanics
"It is absolutely impossible to explain in any classical way and has in it the heart of quantum mechanics. In reality, it contains the only mystery." - Richard Feynman