For any physical theory, you can always just ask "why x", like a child who constantly asks "why" over and over again to every answer, but you will always hit a bottom. There seems to be a popular mentality that "why x" is always a meaningful question, and from that, we can conclude that we don't know anything at all, because all our beliefs rely on a "why x" we don't know the answer to, an so they are all baseless. We can't make any truth claims about the behavior of particles, galaxies, or anything, because you can just infinitely ask "why" until we hit a bottom and then you would say "I don't know."

But, personally, I find this point of view rather bizarre, because, again, it can make it seem like we don't know anything at all and have no foundations for truth claims in the slightest, and are completely ignorant about everything. I think it makes more coherent sense to just allow for to be a bottom to the questioning. Eventually a string of "why" questions will reach a bottom, where that bottom shouldn't be answered with "I don't know" but it should be answered with "it is what it is," because, for all we know, it is indeed an accurate description of reality at a fundamental level and there is nothing beneath it.

That shouldn't be taken as a strong claim that there definitely isn't anything beneath it, as if we should just accept our current most fundamental theories are the end of the line and stop searching. It should be taken as the weaker claim that as far as we currently know it is the bottom, and so we can indeed make truth claims upon that basis. The child might ask, "why do things experience gravity?" You might say, "time dilation near matter." The child then may ask, "why does time dilate near matter?" In my opinion, the appropriate response to that is just, "as far as we know, it is what it is." That could change in the future, but, given our best scientific models at the present moment, that is the end of the line of the explanation.

That seems to be a fairly controversial point, though. Most people in my experience disagree, but I don't see how you can have a basis for truth claims at all if you claim that "why gravity" does indeed have an answer but you can't specify it, because then it would also be baseless to claim that gravity is caused by time dilation near matter, because you've not established that time actually does dilate near matter, as you would be claiming that this relies on postulates which you've not defined. It seems, again, simpler to just take the most fundamental theories as the postulates themselves, as the fundamental axioms.

There is a popular point of view that we shouldn't do this because scientific theories often change, so something you believe today can be proven wrong tomorrow. But then we end up never being allowed to believe anything at all. We always have to pretend we're clueless about nature because if we believe in any of our most fundamental theories, then our beliefs could be overturned. But personally, I don't see why this to be a problem. A person who believed Newtonian mechanics was fundamental to how nature worked back in the 1700s were shown later to be wrong, but that person's beliefs were still closer to reality than the people who rejected it and upheld outdated Aristotelian physics, or people who refused to belief in anything at all. It is fine to later be shown to be wrong, nothing to be upset about, nothing negative about that. We are better off, imo, as treating our best physical theories as indeed fundamentally how reality works, the "bottom" so to speak, until we find new theories that show otherwise, and we change our minds with the times.

That doesn't disallow speculation or research into potentially more fundamental theories. Theories of quantum gravity are such a speculation. They remain in the realm of speculation because no one has demonstrated in the real world that it's actually possible to construct a device such that quantum effects and gravitational effects are both simultaneously relevant and necessary to make predictions. The theories thus describe separate domains, and there isn't a genuine need for a new theory until we can figure out how to bridge the two domains in reality.

We don't actually know what would happen if we bridge the two domains. We may find that our theories of turning gravity quantum are all wrong and that in fact it is quantum theory that needs to be abandoned. We may also find that the domains aren't even bridgeable. We already know of certain physical limitations that make the domains unbridgeable, such as, building an interferometer sensitive enough to detect both gravitational and quantum effects simultaneously would collapse into a black hole. There may be more things like this we will discover later on that just render the two theories unbridgeable in physical reality.

Many physicists are convinced that the bridging will end up turning gravity quantum, but this is just a complete guess, there's no actual empirical evidence for it other than a complete historical coincidence that when studying the strong interaction physicists happened to accidentally stumble upon mathematics that also seemed to be able to also predict a particle that could explain gravity, giving birth to String Theory. People thought it must be correct because it wasn't intentional but discovered by accident, but this isn't a good criterion at all for suggesting it's correct, and ultimately the theory never went anywhere.

If we are to talk about theories replacing quantum mechanics and general relativity, we don't have a clue what these would look like because it's just speculation, and so it could go either way.

That's the real answer. Always check on whose payroll somebody is.

Aren't the first two things just experimental proves of Einsteins relativity theory from over 100 years ago?

I don't know about quantum gravity though.

Unexplainable yet. We may be able to understand how Gravity works.

But of course you are right, there are absolutely things that can not be explained. It is (very probably) impossible to explain why our nature constants are the way they are or why forces act the way they do. The easiest answer to why they are the way they are is to say "They are this way, because if they would be a little bit different we could not ask this question". This sentence implies, that we live in some form of a multiversum and that there are multiple universes existent (in which form doesn't matter) but it is impossible to detect them.

There is an actual logical proof that there are propositions in mathematics that are neither provable nor refutable.

https://plato.stanford.edu/entries/goedel-incompleteness/

Everything we know about all space and time is technically just entirely made up by us.

Entropic gravity

No, it's pain receptors

And yet, jumping from the Burj Khalifa at 1m off the ground is not very dangerous, so it's not the Burj Khalifa that's doing it

That is not a decent salary, that is so low. I made almost that much just out of college in the U.S. Once I made it just over 10 years as EE, I was double that.

55k dollars in the US gets you a crappy apartment and a 7 year car loan.