>Are songs not just "buttons" pressed in a certain order with certain delays (and pedals and whatnot)?

The rest goes into some more delicate theory points but this is something that's easy to address. Music is not just a series of instructions that players repeat like machines. Sheet music leaves out a lot of details because it would make it unreadable to include everything and because it is expected that players will add their own interpretation. How loud or soft something is played is a good example, a composer may specifically put in some places where they feel the dynamics need to be a certain way but players can add their style elsewhere or even ignore the composer completely.

If you want to go down a rabbit hole look up The Firebird Suite Finale on youtube. There are videos of the composer, Stravinsky conducting it, along with many of others throughout the years. You could argue that Stravinsky's version is the correct version but even between different videos of him you can hear changes and I would argue they aren't even the best sounding versions.

And then of course once you get into jazz and more out there genres players start improvising. In jazz you'll often get a sheet that has a quick melody to play at the beginning and the end, with the majority of the performance expected to be improvised based on the chords given. And even those chords will often be modified by musicians because they can.

The Tsar Bomba was also more of a pissing contest winner than anything. The Soviets wanted to have a bigger bomb than the US so they built something completely impractical. It was way too heavy and they had to drop its power so the pilot actually had a chance of escaping the blast after he dropped it.

How close each nuclei is to each other matters. The neutrons get emitted randomly and if everything is packed together tightly that doesn't matter because no matter where they go they're going to hit another fissile nucleus. Once the reaction begins to emit energy it's going to push that core apart and now some of the nuclei being emitted are going to miss a fissile nucleus and just go away into the surrounding environment. Eventually you also convert enough fissile nuclei to non-fissile and they might just absorb the neutron taking it out of the reaction without a new fission. But that won't matter for a bomb, it becomes more of an issue in reactors.

You can use radioactive sources to determine the density of something. The Cs-137 source emits photons when it decays (and betas but those don’t matter here). We know what energy those photons have as well as how many we should see in a second based on what we know about the age of the source itself. You can use that plus a bunch of fancy math to figure out how many photons you should count in a detector a certain distance away. Next we put something we want to know the density of in between the source and the detector and see how much lower our count is. For a lot of common materials we already have tables of what are called interaction coefficients. You use the right table and do some algebra with your measurements and you can figure out the density of the thing you want to measure. This is useful for knowing how well dirt is packed together, how dense rocks are, and it sometimes gets used in manufacturing for quality control.