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Force of gravity for spherical objects of constant density is calculated from 2 masses + 1 distance + a constant.

Before the experiment you can measure the mass of both objects. In the experiment you measure the force and distance to calculate the constant.

The weight either object gives you the force between that object and earth (adjusting for atmospheric buoyancy). Altitude at your location + size and shape of earth gives distance between object and center of earth, you just learned the constant. So you know 4 out of five variables in an equation and can thus calculate the mass of the earth.

Technically that excludes the weight of the atmosphere above your altitude, but you can get that from the air pressure. Similarly the density of the earth isn’t constant but it is very close to symmetrical so you can get a reasonable estimate.

By ascertaining an approxiamte value of G , perhaps? After that, you know M_earth, and already knowing Earth’s geometry, one arrives at average density rho.

The paper is https://iopscience.iop.org/article/10.1088/1681-7575/ae570f

"Please don't fulminate."

https://news.ycombinator.com/newsguidelines.html

how is this at all related to TFA

> he says he just takes it on faith that it has been the same forever

It’s not faith, it’s a working assumption. There are in facts Physicists working on figuring out what would change if some fundamental constants changed with time. Our best measurements and understanding right now is that they do not. If we show tomorrow that it’s wrong, then we’ll build better theories and move on. There is absolutely no faith involved.

The theistic schism? I had to look it up, and was not cleverer after. Nobody can ever know an ultimate why, for obvious and well established philosophical reasons. At least the scientists are trying to squeeze the knowledge gap down as small as possible instead of making up stories.

> If more people would admit their leaps I think the theistic schism would be far more shallow.

There’s an important gap here between science as practiced and science communication.

Working scientists will absolutely admit their ignorance, shaky foundations, etc. This is especially important in astronomy and cosmology, as the field is relatively young and experiments are impossible, outside of those that nature has already done for us. (Both evolutionary biology and linguistics have similar problems but cosmology has it especially hard.)

This, however, is a losing strategy for communication. Most people equate confidence with credibility (and by high school we’ve beat children down enough that they do so as well), so if you do not sound confident people will not listen to you. (I could pontificate on how this is one of the greatest societal ills of our time, science or no science, but I won’t.) Even outside social situations, most people frankly cannot deal with holding a position and simultaneously not being confident in it, and absolutely cannot deal with holding an entire network of mutually-supporting positions and different degrees of confidence in each, while also having multiple alternatives with different degrees of plausibility for some of them. (This is somewhat more advanced than the programmer’s skill of relying on a deep stack of supporting services and debugging tools while keeping in mind that any given subset of them could be lying, which I’m sure you’re aware is also fairly difficult to communicate the experience of.)

Then there’s the active (if not always successful) effort towards never ever reasoning backwards from things you would prefer to be true or that would make the world nicer for you. (The “History Plots” section[1] of the biennial Review of Particle Physics is there solely as an admonishment never to go with the herd. And that’s for things that have no implications for anybody’s worldview, morality, or livelihood!) It is very uncomfortable to genuinely not know where you are going and also not be able to aim anywhere in particular. (It might among other things imply that the entirety of your life’s work only serves to seal off a dead end and you might not even live long enough to learn that. And either way you’re consigning yourself to a very lonely sort of life if you veer away from the mainstream.)

On the flip side from the vagueness, there’s the experience of doing everything you can to break something and failing, of your forefathers doing the same at their most imaginative and still failing. (The aforementioned RPP has pages and pages of tests for frickin’ energy conservation, without which most of physics and engineering just falls apart. And cosmologists can only dream of doing the same on the scales that are relevant to them, and indeed they do keep things like “modified Newtonian dynamics” around. Note that time invariance [as much as there is such a thing in general relativity] is energy conservation [ditto].) It is a sort of confidence that few others have justifiably had in their lives. (Few other things will infuriate a physicist more than offhand quoting a number with six significant digits. They know—in some cases from direct experience—that this sort of precision takes generations. And a well-established theory needs multiple times the effort.)

So when, say, a cosmologist says that cosmic inflation is a bit of a speculative crapshoot but probably true, the Big Bang is likely true, general relativity they’re fairly sure is true but it sure would be nice to find some cracks, the Standard Model is true despite everybody doing their level best to break it because the foundational issues are quite serious, the mass of a free electron is nearly certain, and the inability to surpass the speed of light is pretty much absolute—this is a dynamic range of confidence that none of us can adequately feel. Now take one of those statements in isolation and try to make your listener understand what the apparent equivocation in it really means.

(I do not believe the typical theist in a debate is on more than an advanced amateur level in all of this.)

Then you get into the cursed philosophical issues, like the (weak) anthropic principle (a class of “why” questions don’t and can’t actually have much of a meaningful answer) or nonexceptionalism in cosmology (it is possible that everything we can or will ever be able to see around us is in fact wildly atypical as a great cosmic joke, but if so we couldn’t ever know enough to join in and any science we do would be completely meaningless, so we might as well proceed on the assumption that it is not, and happily enough it’s been working out thus far.)

[1] https://pdg.lbl.gov/2025/reviews/rpp2025-rev-history-plots.p...

It might also be nice if cosmologists stopped claiming their Big Bang "Theory" wasn't more accurately termed a mere Hypothesis. IIRC, 12 out of 13 predictions failing and necessitating "model" "tweaks" is not a fantastic track record for a Theory, which are supposed to robustly survive investigation.