80 years ago today, the first images of Earth from space were taken. A 35mm camera mounted on a captured V-2 rocket launched from White Sands Missile Range in New Mexico. This photo is a frame from the rocket's journey to 65 miles (105 km) above Earth's surface. //

The camera snapped a new frame every second and a half. The V-2 slammed back into the desert at about 500 feet per second and smashed it, but the film survived in a steel cassette, and a recovery soldier said the scientists jumped up and down like kids.

Have you ever seen a bonsai up close? You take a tree that wants to grow thirty meters tall, and every year you cut back its roots and wire its branches so it keeps exactly the same shape. Some live for centuries. They're beautiful. They never get any bigger.

That's what conservatism becomes when it only preserves and never builds. We protected everything, including the things that should have been allowed to die.

In 2022 Elon wrote that unless something changes, Japan will eventually cease to exist. A lot of people here called it rude. I was annoyed too, for about a day. Then I looked at the census again.

WHAT AMERICA SHOULD TAKE FROM THIS

Japan shows you can keep your culture without apologizing for it. Don't let anyone tell you that pride in your country is the problem.

Japan also shows that a nation can get culture right and still lose, if it protects its old companies, its old voters and its old arrangements against its own young people. It dies politely, with clean streets and trains on time.

You still have what we lost: a system that lets things fail and lets new things be born. Bankruptcy, startups, people who move across the country for a better job. Elon is a product of that system. Every bailout, every subsidy for a company that should have died, every rule that protects the insider against the newcomer moves you a little closer to us.

If you know someone who says "America should just be more like Japan," send them this. Both halves.

A nation isn't saved by preserving its past. It's saved by having someone to hand it to.

Despite the common term “PVC glue,” the product used to join PVC pipe is technically PVC solvent cement. Unlike traditional glue, which acts as a surface adhesive, solvent cement chemically softens the surfaces of the pipe and fitting. Once joined, those surfaces fuse into a single, continuous material structure.

This process, known as solvent welding, creates a strong, watertight connection between compatible pipe and fittings when the joint is properly assembled and fully cured. //

Pipe Diameter Pressure 60–100°F
½" to 1¼" Up to 180 psi 15 min
1½" to 3" Up to 180 psi 30 min

There are many types of “pure” water: chemically pure, biologically pure, or a combination of both. RO water, while biologically pure, it is not very chemically pure. The purity (and therefore corrosivity) of RO water is a function of the total dissolved solids (TDS) of the feed water: the lower the TDS, the more pure the RO water. In hospitals, RO is often combined with deionization (DI), and many hospitals follow AAMI TIR standards. RO/DI water is starved for minerals and tends to want to “steal” them from the piping.

All of these factors need to be fully understood and identified before selecting the piping material.

So What Is the Best Material?
Our experts overwhelmingly agree that copper should not be used in this application. Copper can easily leech into the RO water, diminishing its purity. Brass isn’t as easily corroded as copper by RO water, but it still should be avoided for this application.

For any system that includes deionization, Schedule 80 PVC is not recommended. The aggressive nature of the DI water will extract additives from the PVC, weakening the piping structure and contaminating the high-purity water. However, for single-stage RO systems, PVC is acceptable.

For this application, our experts suggest the following materials.

PEX
Many have found that cross-linked polyethylene (PEX) piping/tubing work best in this application. PEX is resistant to the corrosion that is caused by minerals and other contaminants in the water. These contaminants do not build up in the piping, and they do not break down from the constant exposure of the contaminants, which means the RO system can do its job while minimizing the possibility of damage to the plumbing system.

PP
For Types II and III water, polypropylene (PP) piping is suggested. PP is commonly used in these applications and will support not only the resistivity/conductivity levels, but also the other components of the water spec, primarily total organic carbon (TOC).

Keep in mind that PP does not meet ASTM E84 25/50 flame/smoke Ratings, so take care if the piping is within a plenum.

PVDF
For Type I water, PVDF is suggested. PVDF will support the high resistivity levels desired, as well as the tight TOC and other constituent restrictions. Also, to meet AAMI/TIR 34 standards, PVDF with BCF (bead and crevice free) joints to prevent bacteria buildup in the joint crevices should be specified.

Due to its cost, PVDF would usually be reserved for ultra-pure water in applications where water approaching 18 µohm is required.

PVC and CPVC cements are solvent-based chemicals that literally dissolve the outer surface of the pipe and fitting. When you push the two pieces together, the softened surfaces fuse at a molecular level, forming one unified piece — not just a surface bond. Once the solvent evaporates and the joint cures, you’re left with what is, in essence, a seamless pipe.

This is why the material chemistry of the cement must match the pipe. The solvent mix that softens CPVC is not the same formula that softens standard PVC, and using the wrong one means the pipe surface never fully dissolves — leaving you with a weak, brittle joint waiting to fail. //

Using CPVC cement on PVC pipe: Weld-On, one of the most reputable solvent cement manufacturers in the industry, confirms that CPVC solvent cement technically will work on PVC piping — though they still recommend using the correct PVC cement for the job. //

Even though CPVC cement can technically bond PVC, using it routinely on PVC is not recommended. The solvent chemistry is calibrated for CPVC’s harder structure, which can result in:

Inadequate solvent action on the softer PVC surface, causing over-dissolution or uneven bonding
Brittle joints that don’t have the flexibility PVC connections normally need. //

A joint made with the wrong cement may hold water temporarily but fail under pressure cycling, temperature swings, or mechanical stress. The bond never achieves the seamless molecular fusion that proper solvent welding creates. //

Several manufacturers offer all-in-one transition cements specifically formulated to bond both PVC and CPVC. These products are engineered as a true middle ground — not a compromise, but a deliberately formulated blend.

When choosing a multipurpose cement, look for:

Explicit “PVC/CPVC” labeling on the can

Incompatibility Risks: While CPVC cement may create an initial bond with PVC pipe, it is not a permanent solution; the chemical differences prevent the materials from fusing correctly, leading to likely failure over time.

Chemical Differences: PVC and CPVC have different chemical compositions—specifically the higher chlorine content in CPVC—which requires specialized cements and primers designed to react with those specific resins.

Potential for Leaks: Using the wrong cement increases the risk of leaks caused by high water pressure, temperature fluctuations (both extreme heat and cold), and general aging of the weak bond.

Best Practices: To ensure a watertight, "inseparable" connection, always use PVC-specific cement and primer for PVC projects, apply both quickly, and give the pipe a quarter-turn during insertion to distribute the adhesive

SISHEN, South Africa — A South African freight operator has claimed the title for running the world’s longest freight train, taking the distinction away from Australia.

National rail operator Transnet Freight Rail reports it ran an empty 696-car, 7.6-kilometer-long train — that’s 4.7 miles long — on its 861-km (535-mile) Iron Ore Export Line between the port of Saldanha and Northern Cape mine at Sishen. Australian mining company BHP had held the record since 2001 with a 682-car, 7.35-km (4.56-mile) train at its operation in Western Australia’s Pilbara region. According to the Guinness Book of World Records, that train was loaded and also set a record at 99,732.1 metric tons. Before that, Transnet had held the record.

Most of what our Founding Fathers thought was essential to a good education is barely taught in schools anymore:

• Classical languages
• Religion
• Theology
• Biblical literacy
• Penmanship
• Cursive writing
• Calligraphy
• Spelling
• Grammar
• Syntax
• Vocabulary
• Etymology
• Memorization
• Recitation
• Dictation
• Logic
• Formal reasoning
• Rhetoric
• Oratory
• Public speaking
• Debate
• Dialectic
• Persuasive writing
• Essay composition
• Letter writing
• Philosophy
• Metaphysics
• Epistemology
• Ethics
• Moral philosophy
• Natural law
• Virtue
• Character formation
• Moral reasoning
• Civics
• Constitutional history
• Founding documents
• Political philosophy
• Natural rights
• Duties of citizenship
• Classical literature
• Epic poetry
• Poetry memorization
• Shakespeare
• The Great Books
• Ancient history
• Greek and Roman history
• Medieval history
• Church history
• Western civilization
• Chronological history
• Historical biography
• Geography
• Map reading
• Mental arithmetic
• Arithmetic drills
• Euclidean geometry
• Mathematical proofs
• Astronomy
• Natural history
• Music theory
• Choral singing
• Hymnody
• Drawing
• Fine arts appreciation
• Aesthetics
• Physical education
• Calisthenics
• Self-discipline
• Etiquette
• Manners
• Courtesy
• Respect for elders
• Personal responsibility
• Prudence
• Temperance
• Fortitude
• Justice
• Intellectual humility
• Independent judgment
• The pursuit of truth
• The cultivation of wisdom
  //

Nothing to add. Every item here starts with learning to read well. Then a great teacher asks the right question, and it passes from a person to a child. In a class of six, the teacher hears every recitation and catches every stumble. Whoever has the best teachers wins. //

Republican authors (Cicero, Plutarch, Sidney, Cato's Letters) and Enlightenment political thinkers (Locke, Montesquieu)

They would want us to remain obsessed with understanding the conditions required for self governance — the civic virtue and political system

Birds’ compact nervous system seems to help them handle tasks very quickly. //

The crows solved the task the same way primates do, using the same mathematical logic despite having a very different brain structure. And they did it two times faster.

Mostly Ignorant Ars Centurion
3y
383
Buffy said:
Or the Saturn V.

Seriously, though, one of Starships selling points is that it's cost per launch is low, but if you have launch 22 of them for a single lunar mission, it starts to add up.
I think you raise a fair question, so it got me thinking about it.

SpaceX estimates that a fully reusable Starship will cost between $2-$10M per launch. Let's use the upper bound of that estimate, then add a zero to make sure and call it $100M per launch.

Let's say Musk is hugely incorrect and it'll take 20 launches to fuel up a depot.

We're talking $2B to fuel a depot, plus the cost of the depot vehicle, so let's say it's double a normal Starship and is $200M. That's $2.2B to deliver about 100 metric tons of material to the Lunar surface.

Artemis launch costs are a little over $4B per launch, but we'll round down. $4B to deliver an estimated 27 metric tons to the Lunar surface.

Granted, I'm estimating here, but I used a lot of worst-case thinking with Starship costs and it still comes out to half the cost of the only other viable-ish option. Lots for SpaceX to prove yet technically (so does Artemis for that matter, but I'd argue not as much).

Super3DPC Ars Centurion
8y
360
dmsilev said:
A more serious back-of-the-envelope calculation. A full fuel load for Starship is something like 1500 tons, roughly 3/4s LOX and 1/4 liquid methane. We don't really know what the actual LEO capacity of the current version of the stack is, just that it's at least 26 Mk 3 Starlinks plus the dispenser. Call it 55 tons minimum. Let's assume that there's a fair amount of margin in these test flights, future optimization, etc. and say that in the near future 100 tons of payload per flight is reasonable (with the 200 ton design goal well into the future). If they need to transfer a full fuel load into the lunar Ship, that's ballpark 15 launches even without any boiloff or transfer losses.

So yeah, I believe 22 as an estimate, unless HLS Ship doesn't need a full load of fuel for TLI, Lunar capture, and descent/ascent.
It sound like something completely absurd for flag and footprints mission. But for long term permanently manned outpost on the moon, there really is no other way. At the beginning of establishing a base, before ISRU can start, we need lots of hardware on the moon. Habitation module, rovers, construction vehicle, all have to be delivered pretty much in one peace to the Moon.

Face it: the limit is not SpaceX. The limit is rocket equation. There's no way of landing dozens of tons of hardware on the moon with chemical rockets without refuelling dozens of times in earth orbit.

dmsilev Ars Tribunus Angusticlavius
17y
7,869
Subscriptor
The other thing to consider is that getting from LEO to the lunar surface is something like 5.5 km/sec of delta v (Solar system "subway map" chart). Add in another 1.5 or so km/sec to get off the lunar surface and into LLO, where the crew could transfer to Orion for the ride home. That's 7 km/sec needed, which from searching around seems to be pretty close to the dv budget for a fully fueled Starship. So, for Musk's "6 to 8" estimate to work, each tanker really is going to lift 200 tons of cargo to LEO.

Super3DPC Ars Centurion
8y
360
ISUAero1986 said:
I know a few people inside the program that will privately admit the plan is stupid and NaSA should never gone this route.
What we're seeing is the limit of chemical rocket. I agree that for flag and footprint mission or crew rotation mission, using starship is absurd unless the crew being rotated numbered in high tens. But for establishing moon bases, using chemical rocket, dozens of times of refueling is the only way to go to land dozens of tons of cargo on the moon.

After the base is established and can do fuel ISRU production, we can use lunar cycler to reduce the number of refueling launch from earth (material and crew transfer vehicle from earth to lunar cycler then dedicated lunar orbiter from moon to cycler and back). But without dozens of refueling flight per lunar landing, there's never going to be ISRU on the moon. Not on the scale required for on site lunar orbiter / lander.

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Four of the court's nine justices did not participate in consideration of the appeal by the music labels. They did not provide a rationale for their recusal. The remaining justices determined that the case could not be resolved in the coming term, resulting in the lower court's ruling being upheld. //

A provision of US copyright law allows artists to terminate copyright transfer agreements and reclaim their rights after decades under certain ‌circumstances. ⁠For example, copyright grants from before 1978 must be at least 56 years old, and the copyrighted work cannot have been written for hire. The law was meant to address the lack of bargaining power for unknown artists who signed away rights to their works that later became more valuable.
Invoking this law, Vetter sent a copyright termination notice to Windsong in 2019, with an effective date of 2022. Resnik Music Group bought Windsong later in 2019.
Vetter ⁠sued Resnik in federal court in Baton Rouge, Louisiana, in 2023, alleging that Resnik "refuses to relinquish claim to the 'Double Shot' copyright outside of the United States and purports to retain the exclusive right to exploit the work in all foreign countries."
US District Judge Shelly Dick ruled in favor of Vetter ⁠in 2025 and declared him the "sole owner of all right, title and interest throughout the world" of his reclaimed "Double Shot" copyright. The 5th Circuit affirmed Dick's ruling in January.

When Samaritan’s Purse retired its McDonnell Douglas DC-8 freighter N782SP after a final humanitarian mission to Jamaica in late 2025, aviation lost more than just another aging cargo aircraft. The retirement marked the near-complete end of the first-generation jetliner era, a period when four-engine aircraft symbolized the future of global aviation.

Built on December 24, 1968, the aircraft accumulated nearly 99,000 flight hours across a 57-year lifespan. Its career included service with Finnair, the French Air Force, and eventually one of the world’s best-known humanitarian organizations. Instead of heading for the scrapyard, the jet now lives on as a static display and educational platform at Liberty University.

While its rival, the Boeing 707, largely disappeared from civilian skies decades ago, the DC-8 continued hauling cargo well into the 2020s.

The reasons were deeply technical: an overbuilt airframe, extraordinary structural durability, and one of the most successful re-engining programs in aviation history. In many ways, the DC-8 became the ultimate example of how smart engineering and adaptability can extend the life of an aircraft far beyond what its designers ever imagined. //

Boeing was heavily committed to developing its next-generation narrow and widebody aircraft, including the 757 and 767, which represented the future of its commercial lineup.

A modernized 707 risked prolonging the life of an older platform that could compete internally with these newer, more profitable designs. In contrast, Douglas had fewer competing priorities and a greater incentive to extend the DC-8's life, making the Super 70 program a central part of its survival strategy.

The DC-8 also held a subtle but important physical advantage that made its conversion more practical. Its main landing gear sat higher relative to the wing and fuselage. This provided better ground clearance for the larger-diameter CFM56 engines. This reduced the amount of structural modification required when compared to the 707.

It also lowered engineering complexity and overall conversion cost. In the end, this seemingly small design difference helped tip the balance in favor of the DC-8, allowing it to successfully transition into a long-lived, economically viable cargo aircraft while its rival faded from the skies. //

The DC-8 became particularly popular for routes where acquisition cost mattered more than maximum fuel efficiency. Even as aviation technology advanced, the aircraft continued proving itself as a reliable workhorse. //

Humanitarian organization Samaritan's Purse gave the aircraft one of its most meaningful final chapters. After being rescued from storage in Roswell in 2015, N782SP flew more than 200 relief missions worldwide, transporting millions of pounds of humanitarian cargo into disaster zones and crisis areas.

This tool provides visual feedback about shading in rows of solar panels (PV, thermal, etc.) Please read the introduction before using this tool.

There is an old and unsettling theological idea about demons: they cannot truly be satisfied.

They don’t sleep. They don’t rest. They hunger but are never filled. They desire but are never content. Whatever they possess only produces the desire for something else.

Whether one accepts that as literal theology or simply considers it as a thought experiment, imagine how horrible such an existence would be.

You are starving, but eating never makes you full.

You are exhausted, but sleep never comes.

You desperately want something, finally possess it, enjoy it for a moment—and immediately begin wanting something else.

Forever.

Forget the cartoon version of hell with red devils, pitchforks, flames and boiling cauldrons.

What if hell is simply never being satisfied? //

C.S. Lewis famously made an observation that cuts directly into this problem. In Mere Christianity, he argued that when we discover within ourselves a desire that nothing in this world can satisfy, perhaps the explanation is that we were made for something beyond this world.

People sometimes summarize that idea by saying there is a “God-shaped hole” inside the human heart. That isn’t actually Lewis’s phrase, but it captures something important.

We keep trying to fill an infinite longing with finite things.

And finite things eventually run out. //

Even good things—family, achievement, adventure and friendship—cannot bear the weight of becoming our ultimate purpose.

Christian theology has another word that appears surprisingly often when describing this problem:

Rest.

In Matthew 12, Jesus describes an unclean spirit wandering through dry places “seeking rest” and finding none.

That’s an interesting description of evil.

Restlessness.

Augustine famously approached the same idea from the opposite direction when he wrote that our hearts are restless until they rest in God.

Perhaps those ideas belong together.

Maybe separation from God isn’t merely punishment imposed upon a creature from the outside. Perhaps part of the punishment is what naturally happens when a creature separates itself from the only thing capable of ultimately satisfying it. //

If that’s even remotely accurate, perhaps we occasionally manufacture little pieces of hell right here on Earth.

Not because food, money, technology, possessions or pleasure are evil. They’re not.

The danger comes when we expect them to accomplish something they were never designed to accomplish.

That raises a question worth asking occasionally:

Am I enjoying the things in my life, or am I asking them to fill a hole they were never designed to fill?

Christianity offers a remarkable answer.

Jesus Christ did not enter history promising humanity a better shopping list, greater status, more possessions or another temporary distraction.

He offered something completely different.

Forgiveness.

Reconciliation with God.

Eternal life.

And something our perpetually hungry culture increasingly doesn’t know how to provide:

Rest.

“Come to me, all you who labor and are heavy laden,” Jesus said, “and I will give you rest.”

Maybe that’s the Gospel hook we’ve overlooked.

Perhaps heaven isn’t getting everything we’ve ever wanted.

Perhaps heaven is finally discovering what we were created to want.

And perhaps salvation begins when a tired, hungry human being finally stops trying to fill an infinite hole with finite things, turns toward Jesus Christ, and discovers that the invitation has been there all along:

Come to Me.

I will give you rest.

The FBI's Safe Online Internet (SOS) Challenge—which has taught cyber safety and digital citizenship to more than a million students in 3rd to 8th grades since October 2012—ends effective June 1, 2026 (due to budget constraints).

Additional resources for educators:

• https://consumer.ftc.gov/identity-theft-and-online-security/online-privacy-and-security
• https://www.staysafeonline.org/
• https://www.cisa.gov/audiences/educational-institutions
• https://beinternetawesome.withgoogle.com/en_us

On December 14, 1986, an improbable chapter in aeronautical engineering reached its defining test when the Rutan Model 76 Voyager began its takeoff roll down the runway at Edwards Air Force Base. Conceived by aerospace visionary Burt Rutan and brought to life in Hangar 77 at the Mojave Airport, Voyager was engineered to achieve what had long eluded aviation: flying nonstop and unrefueled around the planet. Burt realized that utilizing advanced carbon fiber, aramid composites, and lightweight paper honeycomb could yield an airframe weighing under ten percent of its total takeoff mass, allowing the remainder to consist almost entirely of aviation fuel. Empty, the aircraft weighed just 939 pounds; laden with 1,200 gallons of fuel distributed across seventeen internal tanks, its weight ballooned to 9,694 pounds.

Piloted by decorated veteran Dick Rutan and record-setting aviator Jeana Yeager, the mission faced imminent disaster before leaving California soil. As the aircraft gathered speed, the heavily burdened, flexible wings bowed downward, violently scraping the runway surface and grinding away the wingtips. Despite severe structural abrasion, Dick nursed the craft into the air past one hundred knots. In the chase aircraft, Burt Rutan and Mike Melvill watched both damaged winglets shear off over the Pacific Ocean, yet the crew elected to press forward. What ensued was a punishing nine-day test of human stamina and mechanical endurance. Dick and Jeana were confined to a cockpit measuring just forty inches wide and thirty-three inches high, subjected to continuous mechanical roar after noise-canceling headsets failed.

You think time ages you. Everyone does. But Einstein proved something that changes everything: time is not fixed. The faster you move through space, the slower you move through time. At the speed of light, time doesn't slow down. It stops.

In this video, inspired by Richard Feynman's legendary approach to special relativity, we break down exactly why light never ages, what spacetime actually is, and why every second of your life you are already moving through the universe at the speed of light.

This is not science fiction. This is physics. And it will change how you see time forever. //

“you are always moving at the speed of light through spacetime.”

That motion is divided between space and time. If you are sitting completely still in spacetime then you are spending the maximum amount of time.

The faster you move through space, the slower you move through time.

Recently, I read an article about device fingerprinting, which argues that we’re in the post-tracking-cookie era. They’re no longer needed, because every browser can be fingerprinted with 100% accuracy.

https://royfish.dev/fingerprints-are-the-new-cookies

There’s an EFF page which allows you to test your device fingerprinting. https://coveryourtracks.eff.org/

The information theory idea is that while there are millions of people who have the same time zone, time zone offset, fonts, etc., it’s the combination of all these things that makes it possible to identify.

The EFF has a page on this, which explains. After establishing that 33 bits of entropy is needed for identification:

So for instance, if we know someone’s birthday, and we know their ZIP code is 40203, we have 8.51 + 23.81 = 32.32 bits; that’s almost, but perhaps not quite, enough to know who they are: there might be a couple of people who share those characteristics. Add in their gender, that’s 33.32 bits, and we can probably say exactly who the person is.

The Liberty Bell, with its famous crack, hasn’t been rung in 180 years, but that hasn’t stopped scientists from pondering what the bell might have sounded like when tolling. In honor of the nation’s 250th anniversary, researchers at Penn State University have modeled its acoustic properties, drawing on data collected from one of the bell’s replicas. The work was first presented at a meeting of the Acoustical Society of America in Philadelphia earlier this year, followed by an article in Physics Today.

Historians aren’t sure exactly when the Liberty Bell acquired its distinctive crack, just that it occurred sometime between 1817 and 1846. An 1846 account in the Public Ledger described the ringing of the bell on February 23 that year and mentioned that the bell had developed a crack, which someone had attempted to fix by filing the sides down. But it didn’t work: The February 23 ringing extended the crack even more, so much so that “the old Independence Bell … now hangs in the great steeple irreparably cracked and forever dumb.” Nobody has heard it ring since.

This wasn’t the first time the bell had cracked; the rim cracked shortly after it arrived in Philadelphia in 1752, the first time the clapper struck while testing the sound. It was recast by two local foundry workers, John Pass and John Stow, not once but twice, because the first recast produced a sound that one bystander likened to coal scuttles banging together.

The second recast’s sound was deemed acceptable, and the bell was typically used to summon the Assembly, among other purposes, until it fell into disuse after the American Revolutionary War. As for why the bell was so prone to cracking, a 1975 study of the bell’s chemical composition revealed that the metals used formed “an extremely brittle alloy” that also made it easier for souvenir collectors to chip off pieces from the rim. //

Autapomorphy Ars Praetorian
8y
569
Subscriptor
Since it's hard to imagine frequencies based on a number, I calculated the following based on equal temperament tuning using a standard concert pitch where A4 is 440 Hz.

174 Hz = -16.06 semitones. That's 6 cents flat relative to F2
323 Hz = -5.35 semitones. That's 35 cents flat relative to E3
381 Hz = -2.49 semitones. That's 49 cents flat relative to G3
510 Hz = +2.56 semitones. That's 44 cents flat relative to C4
623 Hz = + 6.02 semitones. That's 2 cents sharp relative to D4#