I don't know if you're a student at the UA, but the Students for the Development and Exploration of Space (SEDS) club there has (or at least they did when I was a member in 2016) a pretty impressive Dobsonian that has a mirror that was specially built by the Mirror Lab when they were testing out some new manufacturing techniques. I believe they were developing the lightweight honeycomb structures that are now common. It's pretty old and not super fancy, but the mirror itself makes it an interesting piece of astronomy history.

The change in the words isn't the important part - tracing the changes through time is how we arrive at the original PIE word. The important part is that the words were conserved throughout the daughter languages which indicates that the original PIE speakers had words for them and the were used enough and important enough to be passed down from the generations. A lot of really common words in IE languages can be traced back all the way to the hypothesized mother tongue simply because they are commonly used words. The fact that there are tons of preserved words relating to horses, chariots, and wagons tell us that the original PIE speakers likely used them a lot.

This is a phrase that was popularized by U.S. President Dwight D. Eisenhower during his farewell address. In it, he warned to beware the dangers of the "military-industrial complex". The initial drafts of this speech actually include the wording of "military-industrial-congressional complex," which is really more what he was talking about, but the congressional portion was removed to not upset politicians. This is an important point to make, as congress is an important player in the complex.

Anyway, the idea is that the way these three things interact creates huge conflicts of interest between them and it generates a feedback loop of corruption and wasteful spending. So you have politicians in congress that want to continue to be voted in - the easiest thing they can do to pad their resume is point to jobs that they've generated for their constituents. Since they're in the government, they can vote for bills that will award big contracts to companies that are based in their districts. Since the US military is so huge, most major contracts are defense related. This generates jobs for the citizens of that district, generates big money for the company that gets awarded the contract, and helps the politician get re-elected. So everyone wins, right? Well, not really. When this starts happening, there's a feedback loop that occurs that starts to inflate the prices of everything because everyone wants a piece of the pie - corporate lobbyists spend a ton of money on politicians, politicians want to spread out the jobs so it becomes difficult to effectively build things, and the military likes fancy expensive things. But the really big issue is that it promotes extremely wasteful spending; when it's in everyone's best interest to just fund a ton of military projects, things that get funded are not actually beneficial to the military capabilities of the country and instead it starts focusing on whatever benefits corporations and politicians the most, because the military stops actually being the main beneficiary of military spending. And once we have all this bloated military spending and equipment, suddenly using it in conflicts to justify its existence becomes in the best interest of politicians and corporations that benefit the most from it.

Fun fact, you can see Alpha Centauri B in the night sky of Pandora in the first film. It's an unusually bright star.

>Ideally, you want the pressure at exit to be equal to ambient pressure. (This is mainly about efficiency?)

Yes, this is ideal. I'll expand on this a bit. Take a look at this image of possible nozzle flows. The first one is underexpanded (as in the nozzle didn't expand enough, so the flow is higher pressure than ambient), the second is perfectly expanded, and the third is overexpanded.

Let's go back to Newtonian physics. Remember how every action has an equal and opposite reaction? This is how rockets work - gas is pushed out the back, and that pushes the rocket forward. However, if the nozzle is not perfectly expanded, then that means the gasses are moving out at an angle - either radially outwards (underexpanded) or inwards (overexpanded). So if that gas is moving away from the rocket, there must be an equal and opposite reaction in the same direction - if some gas is moving up from the rocket, then the gas must have pushed it down. Since it's a circle, it cancels out, but this is the primary issue with exit pressure not at ambient - some of the energy coming out of your rocket is being futilely used to push on the walls of the nozzle rather than to push the rocket forward. With a perfectly expanded nozzle you don't have that problem, as all of the momentum is pushing straight up the rocket's velocity vector.

Ultimately, it's a trade off. Nozzles have a weight associated with them, after all, which is extremely important when launching something to orbit. For the first stage of a rocket, the nozzles are typically optimized for lower altitudes, as they will spend the most time at lower altitudes gaining speed. However, once they are higher up, their plumes become absolutely huge because of this. Once you get to high altitude or vacuum, the second+ stage nozzles can get pretty big and it becomes a tradeoff between how much weight the extra nozzle ends up adding.