P.S. The DeWalt Portable Power Station is really, really close. I have no idea why they don't allow it to run like a UPS.

Use power tool batteries. The bigger ones have plenty of energy (18V 5Ah). For many people it's perfectly fine to share a battery between the UPS and an infrequently used drill, which amortizes costs. Ideally one of the tool companies would even pick up manufacturing. There are some multi-battery tools already if you want to really have fun.

https://www.ryobitools.com/pow...
https://www.ryobitools.com/out...

Cordless power tools typically use interchangeable lithium ion battery packs. There's a few different systems out there from Ryobi, Ridgid, Milwaukee, Makita, etc. It's not just impact hammers and drills; there are fans, radios, lights, hedge trimmers, garage door openers. Some of these companies support dozens of tools. Many of these tools see daily use by professionals, but a lot are sold to home owners and hobbyists where most of their time is spent sitting on a shelf. The battery packs are reasonably big, 70 watt-hours are not uncommon.

I cannot for the life of me figure out why these companies don't offer a combination charger + uninterruptible power supply as part of their pantheon of tools. That way these battery packs could be doing something useful by providing emergency backup power to an electrical device, when they aren't being actively used in another tool.

Residential heliostats. We have two. Natural light is awesome.
.
Multisplit air heat pumps. After adding insulation and reducing air leaks, the new
heating system as 4 zones. We can heat the whole place on the coldest day
with about 48 kilowatts of heat, which is less than the flue loss on our old
propane furnace.

Attic trapdoor tent, to reduce one source of air leaks. I feel like camping any
time I have to unzip and enter the attic.

Serious gutters. I really wish we had aluminum instead of the rusty steel, but
more importantly for us are the hardcore micromesh guards that finally, finally,
finally will keep out the needles.

I'm also loving the new 10 year battery only smoke detectors. Anything that cuts
down maintenance is a win.

I forgot to mention PDF rendering engines. Neither support the entire spec, nor do I blame them.

poppler - widely used
pdfium - high performance, recently open sourced

I've found these tools useful, with an honorable mention to gnupdf. I've never used it personally, but the code looks pretty solid. That said, when I really needed to produce great multilingual PDF I pulled out the PDF spec, gritted my teeth, and generated it directly.

leptonica - turn images into PDF
tesseract - turn images into searchable PDF
qpdf - linearize PDF for random access over HTTP
jhove - basic validation
jhove-pdf-a - validation with better compatibility guarantees
pdftk - command line tool for splicing pages together or apart
ttx/FontTools - tool for modifying custom fonts
reportlab - python library, easy to use but works best with Latin scripts

Clock speed can be quadrupled by switching to a pipeline architecture. See 24:28 of the video.

Serious answer. An optical fiber is only transparent for a limited range of colors. As soon as you modulate a single color (monochromatic laser beam) the resulting light beam is by definition no longer monochromatic. Here's a fun, beginner oriented book on the topic.

You have chosen to measure life in terms of personal dollars; nothing I write is going to change that. But I have a different perspective. A revolutionary jet engine would be fantastic. It goes way beyond corporate profit. A better engine contributes to air travel; making it faster or safer or more accessible. Something to be very proud of.

This is an age old issue. For example during the Dutch Tulip Bubble in the 1600's people were pissed off that too much energy and wealth was wasted in the hands of (parastic / useless / unproductive) tulip speculators. I'm also an MIT engineering graduate, around the time of the first dotcom bubble. Some of my talented technical friends spent their precious time chasing dollars, which at the time meant selling knicknacks over the internet. Others stuck with engineering and did just fine, including the aero-astro folks. If you are facing this decision, think long and hard what is really important. We are only on this planet for a short number of years, spend it wisely.

Use Advanced Search and restrict to Full view only. Here is a scan from the New York Public Library. Speaking of popular fads, there's also a version for people with 3D glasses

I've raced for about 20 years in cross country skiing (starting with high school, then at the NCAA level in college, and now in citizen races) and have probably entered well over 100 events. More importantly I've known a lot of racers over the years. I've never, ever heard of knee damage being a common problem for cross country skiers. In fact, cross country skiing is one of the more gentle sports on joints, especially compared to long distance running which has a lot of pounding. There are tons of old people (70+) competing in citizen races, and they are often quite fast. Even the skating technique is not so troublesome, although it is a little more wearing than diagonal stride over very long distances. Are you thinking of something in particular that causes knee damage?

If Google wants to be really clever, they could make sure there is support for scanning in the exact same specification. Historically there has been a huge imbalance between paper sources (printers) and paper sinks (scanners), so it's no surprise that ideas like the paperless office never took off. However, in the last five years, fantastic scanning equipment has reached consumer availability; for example the Fujitsu Scanscap S1500 has an automated document feeder and has dual sensor bars, which allows duplex scanning without weird paper paths and associated jams. It works great for evaporating large piles of random paper from financial documents to old notes from school to obscure manuals for equipment. Hopefully Google will step up to the plate, make Scanning a first class citizen of this initiative, and finally fix the historical imbalance. This will - quite literally - have tons of impact on people's lives. I care enough that I'm willing to help make it happen.