I've got a new batch of techs to add, mostly to fill what I see as a few gaps in the tree. For each new tech, I have already settled on images and tech quotes, and I have at least three buildings that are new or moved from other techs (none of which will fall below allowing at least three new pieces of content). Following are the details and my rationale. I will go ahead with these changes if it seems like everyone is happy with them.
Statistics X62, Y19. Requires Industrial Lifestyle. We have at least one mathematical tech in the earlier eras (Mathematics and Geometry in Classical, Algebra in Medieval, Calculus in Renaissance), so I would like to continue the pattern to some of the later eras. Statistics is a particularly important branch of mathematics that laid the groundwork for numerous Industrial technologies and organization. I plan to add a university-level Mathematics Department to replace the Mathematics Academy, a National Census, a Public Health Agency, and the Metric System.
Thermodynamics and Modern Sanitation will require Statistics.
Incandescent Lighting X68, Y19. Requires Electricity. The light bulb is the quintessential invention (and the symbol of technology in Civ I) and deserves its own tech. Also, the Electricity tech is rather overloaded. Edison's Workshop and all the lighting techs at Electricity will be moved to Incandescent Lighting.
Telephone X68, Y11. Requires Electricity. I always found it puzzling that Telephone Network is opened at Telegraph. Telegraph and Telephone are far enough in history and distinct enough that they are really two separate techs. Also, you need Electricity to build a Telephone Network, which requires Telegraph. In addition to moving Telephone Network, I plan to add Call Center and Polling Firm at Telephone. I also plan to add Mail Order Catalogue at Telegraph to fill the gap created there.
Civil Engineering is moved to X69, Y17 and requires Incandescent Lighting and Telephone instead of Electricity
Management X70, Y9. Requires Psychology, Civil Engineering, Foreign Policy. The late 19th century is the time when management as a discipline matured. In particular, this is meant to capture Frederick Taylor's system of scientific management. I plan to move Assembly Plant here, and add IQ Testing Center, Racial Profiling, Business School, Wristwatch Maker, and Time Zones. On a somewhat related note, I would like to see the Assembly Plant become a prereq for more Atomic Era buildings, a role similar to Factory and Manufacturing Plant. I am debating internally whether I want to call the tech Management or Scientific Management.
Industrialism, Trench Warfare, and Fascism will require Management.
Abstract Mathematics X72, Y7. Requires Modern Lifestyle. This is the Atomic Era mathematical tech. It was around the late 19th, early 20th centuries that pure mathematics as we know it today matured as an academic discipline. I'm not sure exactly what to add here, but I am planning on several major mathematical theorems that are built as Great Wonders, such as Fermat's Last Theorem, the Godel Incompleteness Theorem, the Church-Turing Thesis (though that might fit better at Decryption Machines), and the Millennium Problems. While we're at it, it might be interesting to put some other major theorems in the game at other techs, such as the Pythagorean Theorem, the Quadratic Formula, and the Four Color Theorem. But that's getting a bit ahead of ourselves.
Encryption Machines requires Abstract Mathematics.
Theory of Relativity requires Abstract Mathematics instead of Modern Lifestyle. Also, Theory of Relativity is moved to X73, Y7.
Computer Science X79, Y13. Requires Early Computing, Modern Physics. We have a lot of computer techs around this time: Early Computing, Semiconductors, Microprocessor, and Personal Computers. But they all focus on hardware. The Computer Science tech would focus on software. Buildings include Software Firm, Computer Science Department, Programming Language, User Experience Research Lab, and Supercomputer. Might also call this tech Programming or Software Engineering.
Personal Computers requires Computer Science.
Postmodernism X79, Y5. Requires Pop Art, Globalization. We arguable have an overabundance of art-related techs in the Industrial and early Atomic Eras. Postmodernism would come later than the rest, and I think it is historically important enough to merit its own tech. New content includes Retreat Center, Environmental Art Studio, Portland Building.
Mass Media requires Postmodernism instead of Pop Art.
Chaos Theory X87, Y1. Requires Information Lifestyle and Climate Models. This is the Information Era mathematical tech, and a catch all for contemporary mathematics. Compared to Abstract Mathematics in the previous era, the focus is more on applications. I went with Chaos Theory because that was a branch of mathematics that captured the public imagination in the 1990s and in some ways feels appropriate for the ethos of the period. New content includes Biosphere 2, Traffic Engineering Agency, Financial Risk Monitor, ArXiv.
Communication Networks requires Chaos Theory instead of Microwaves, Satellites, Laser.
Computational Sociology X94, Y17. Requires Machine Learning, Online Community. Computational Sociology is an emerging discipline that applies quantitative methods to sociological research. Arguably there is some overlap with Media Psychology. New content includes Center for [AI/Biotech/Nanotech] Safety and Social Media Surveillance. Also, the Applied Sociology Lab is currently misplaced at Cybersociology and will be moved here. Speaking of which, I need a better sense of what the Cybersociology tech is for.
Augmented Reality, Direct Merchandizing, Megacities requires Computational Sociology.
Industrial Ecology X95, Y5. Requires Ecological Engineering, Rapid Prototyping. I'm on the fence on this one, since it comes right after Ecological Engineering and looks rather similar. But I have a lot of things I want to add around this period and the Ecological Engineering tech is getting overloaded. I see Ecological Engineering more about urban design and culture, and Industrial Ecology is more about heavy industry. New content includes Hydraulic Fracturing, Enhanced Geothermal Systems, Aquaponics Tank, Heating and Cooling District, Supercritical CO2 Turbine. Automated Waste Disposal, Generation IV Reactor, and CO2 Reservoir would be moved here, and perhaps some of the manufacturing complexes currently at Rapid Prototyping.
Megacities and Controlled Plasma require Industrial Ecology
Autonomous Vehicles X95, Y15. Rapid Prototyping and Digitization. Would replace the existing Automated Traffic tech.
Automated Traffic. Moved to X100, Y19. Requires Nanotech Lifestyle and Affective Algorithms and Megacities. Why have Autonomous Vehicles and Automated Traffic as separate techs? Again, it comes down to a growing list of new content, which is starting to be too much for one tech. AVs are about individual vehicles and refer to self-driving cars, automated tractors for farms, and automated mining systems. This is an emerging technology today. Automated Traffic is more futuristic. It refers to a traffic system where manual driving has been phased out, allowing for novel transportation system designs. I plan on adding Interlaced Intersections, Subterranean Tunnel Network (see e.g. The Boring Company), Mobile Bodega, Elevated Bicycle Track. I am still sorting out which existing buildings should go at AV and which should go at AT.
Automated Robotics and Hypersonic Flight require Automated Traffic.
Jovian Terraforming X133, Y13. Requires Ecosynthesis, Gravity Control. Using superstrong materials or some sort of active support system, we can "terraform" a gas giant by building a massive shell around it. Previously this concept was folding up in Planet Engineering, but against I want to add too much more one tech. New content includes Terraformed [Jupiter, Saturn, Uranus, Neptune], Interstellar Terraformed Gas Giant. Fusion Candle will probably be moved here.
Stellar Computing requires Jovian Terraforming.
Additionally, there are a number of redundant tech prereqs in the Galactic Era that I would like to clean up.
. Deep Space Colonies requires Planetary Manufacturing
. Kuiper Belt Exploration does not require Planetary Manufacturing
. Weather Control does not require Climate Models
. Subterranean Exploration requires Advanced Shielding and Human Transmutation instead of Astro Environmental Systems and Volcanology
. Colony Arcology requires Sentient Earth, rather than Shielding and Organic Cities
. Drop Advanced Shielding and Planetary Manufacturing from Launch Arcology requirements
. Astroecology requires only Galactic Lifestyle
. Attometer Nanomorphism requires Cultural Evolution instead of Nanotroids
. Teleportation requires Interstellar Communication instead of Quantum Computing
. Weaponized Disintegration does not require Solar Ordnance
. Weaponized Gravity Fields does not require Advanced Warmachines
. Weaponized Antimatter requires Star Lifting instead of Weaponized Disintegration
. Astroimperialism does not require Interstellar Communication
. Picotechnology does not require Teleportation
. Wormhole Traversal does not require Teleportation
I will conclude with some general thoughts on the future tech tree. Right now I am dissatisfied with a few things in how the Galactic Era works. There is a gap between Interstellar Travel and Interstellar Colonization to capture the travel time of the first interstellar journeys, which are likely to be around a century. I like that, but the gap might be too long. By the same token, the portion of Galactic Era after Interstellar Colonization feels a bit compressed, and I would like to have another column or two to work with. Fortunately there are a couple columns in the early Galactic Era without much content, so it should be possible to shift things around without disrupting the other eras.
Another issue is that, to the fullest extent possible, I want to have all speculative physics be in the Cosmic and Transcendent Eras. There are tons of great concepts for colonizing the galaxy and even neighboring galaxies using only established physics, but they get spoiled when wormholes, warp drives, and time travel are available. Perhaps Intergalactic Colonization and Wormhole Communications could both be in the first column of the Cosmic Era. Moving those things forward would give us more room in the Galactic Era to build out great astroengineering works. There are also various gravity manipulation techs in the Transhuman and Galactic Eras, which are also speculative physics, and those are tricky to deal with.
All these changes would require a lot of careful rearranging of the existing content, so this would be a major project and I don't have a clear plan yet.