I'm actually studying to become an astrophysicist, so obviously space intrigues me greatly.

There's actually a surprising number of things we simply don't know about space.

How about this?

Einstein's equation for general relativity still has a known contradiction in it, unless we specifically know how to quantize space-time (we don't), or we "cheat" by replacing a quantum mechanical operator in one side of the equation and put in the expected value. What this is

*is* semi-classical gravity.

Problem is, it works way too well, almost suspiciously well. So much so, it feels like a cop-out.

Here's the math of which I'm speaking:

If we look closely on the right hand side of the equation, we see that T has a hat over it. That's to indicate it as a quantum mechanical operator, since we know matter is quantized, as per quantum mechanics, we

*have *to put the hat over the T.

Problem is, quantum mechanical operators are weird. Unlike with normal multiplication, where you can put the numbers in any order, this doesn't work with quantum mechanical operators.

For example this:

Is not the same thing as this:

Because of the nature of quantum physics, the equation, as it currently stands, might as well say, "Some apples = some oranges." Which is an absurdity.

Like I said, we can cheat and swap out the quantum mechanical operator for the expected value to get this:

"Why not put hats on the operators on the left hand side of the equation?"

Well, we would.... If we knew how spacetime was quantized. And we do not.

So, we're stuck. Either we find out how spacetime is quantized, or we cop-out and use semi-classical gravity.

So, despite the fact that physics can explain

*A LOT *about the universe, problems like this do crop up. What makes this matter even more complicated is that we can't just discard either relativity or quantum mechanics, as they have demonstrated their veracity on multiple occasions.

Problems like this are exciting for scientists, because they want to seek the solution to the problem. No doubt, when (not if) we find the solution to the problem, there will be a whole new field of science.