The Moronic Principle
I lived in DC for a number of years, and while I was there, I was a member of the Smithsonian's "Associates" program, which is basically a paid activities club. For an annual fee, plus the cost of the specific event, you could tour the back rooms in your favorite Smithsonian complex, attend a lecture series by a visiting scholar, see special exhibits only open to small groups, etc.
One of the cooler things I learned was how we experimentally validate our understanding of planetary formation.
As you might expect, this is something of a challenge for the experimental scientist because we have neither sufficient unused raw material for a planet, nor the space in which to build one, nor the ability to create the required pressure and heat on a planetary scale, nor millions of years to wait for a baby planet to be born.
Or not form, or be born deformed, if the experiment were a failure.
But we do have some raw material. It falls to earth in meteors. And places like the Smithsonian have collected quite a bit of it. And we can generate the pressure and heat required, just not on a planetary scale. All you have to do is put a tiny piece of raw meteor between the pointed tips of two diamonds and put the diamond sandwich in an industrial vise.
Under normal conditions, even the strongest vise on earth wouldn't be able to generate anywhere near the pressure required to make a planet, but since pressure is force over surface area -- i.e., pounds per square inch -- if you make the surface area very, very small -- say, mere microns -- you can actually generate the extremes of planetary formation. (In mathematical terms: you make the denominator very, very small such that a medium-sized number divided by a very, very small number yields a really, really big number.)
But you need more than pressure. You need heat approaching that of the sun, which you can get if you focus a pair of high-intensity lasers at the microns-wide chunk of meteor between the tips of the diamonds in the industrial vise. Again, human-scale energy in a near-infinitesimal space results in cosmic extremes, albeit on the microscale.
So you do that for a bit, then you let your tiny meteor fragment cool. You cut it open and take a look under a microscope. What you find is pretty much what you expect. All the iron in the fragment melts into a ball at the center, just like the Earth's spinning core (which gives us our magnetic field) with other minerals forming a crust on the exterior. You can then do chemical analysis on that crust to see if it contains the kinds of inorganic compounds we find on planets, versus what we find in meteors. And it does.
You can repeat this experiment under different conditions, such as in a vacuum, in the presence of water, or oxygen, or methane, or whatever, and see if you get different results. You can vary the heat and pressure and so accumulate a lot of physical data with which to make predictions about far away planets we've never even seen. All without leaving the lab.
Now, what we've achieved here is not absolute proof of anything, obviously, but it is nice confirmatory evidence consistent with our many other observations, and if you combine it with a number of other experiments, and they all (or almost all -- science is rarely pure) tell a concordant story, then we have good reason to believe our model of how planets form is correct, even though no one has ever directly witnessed such an event, and probably never will given the timescales involved.
I think about things like this whenever I hear someone opine about vaccinations or global warming or evolution or some other heavily politicized science in order to remind myself that what I'm experiencing at that moment is good experimental evidence that they are a moron, and that the phenomenon of morons is well understood and I don't need to investigate further.