Thorondor

Nothing is completely foolproof, but LORAN is much, much more resistant to jamming than GPS. GPS satellites orbit over 20,000 km from Earth and transmit at very limited power (less than 50 W). That makes it easy to overpower their faint signals. On top of that, GPS operates at a frequency over 1 GHz which means you can broadcast a jamming signal with a small antenna. LORAN is the opposite. It uses low frequency, extremely high power signals transmitted from stations relatively closer to the receiver. Those design choices make it less precise but vastly more robust.

Air-independent propulsion.

The US is the second largest textile exporter in the world. Sources: https://ncto.org/facts-figures/us-textile-industry/ and https://www.trade.gov/selectusa-textiles-industry It's true that a significant amount of that is fabric and fibers, and most of the clothes sold in the US are not actually sewed here. But on the other hand, US companies also show up in other places in the clothing supply chain as well - American fashion design and marketing contribute a lot of the final value of many clothing items sold here and overseas.

> Can you provide the source? In the WTO's broader medical goods category, Germany actually exported slightly more than the US in 2022 ($202.6 billion versus $189.6 billion), so such a huge difference in a few years?

Sure, these are my sources. World Bank (2023): https://wits.worldbank.org/trade/comtrade/en/country/ALL/yea... Observatory of Economic Complexity (2024): https://oec.world/en/profile/hs/medical-instruments

> China accounted for approximately 44.2% of the 104 new molecules in 2025, compared with 26.9% for the U.S. and 15.4% for Europe.

Source for this? My source was Citeline's 2026 annual review at https://pulseforinnovation.org/by-the-numbers-citelines-rd-a... which states:

> Findings from Citeline’s latest report, Pharma R&D Annual Review 2026, highlight the continued U.S. leadership in the life sciences ecosystem... The U.S. leads all other countries, currently advancing over 11,600 medicines – more than half of medicines in development worldwide.

> I will just give 3 examples

In general, I was referring to "major industries" in the sense of economic categories, as defined by (for example) the UN: https://unstats.un.org/unsd/publication/seriesm/seriesm_4rev... Here shipbuilding is considered to be part of "manufacture of other transport equipment." I admit my wording was a bit imprecise; if you are going down to the level of specific products like ships or solar panels, clearly it will be easy to find examples of things that the US does not produce on any significant scale. Nevertheless, a few comments on your examples:

> China completed roughly 91% of the world’s shipbuilding tonnage in 2025

Source on this? 91% is a lot and I can't find anyone else making this claim. However I'll concede that the US is far behind China, South Korea, and Japan in shipbuilding.

> [China] holds more than 80% of solar module manufacturing capacity

You are correct that the US has "only" 60 GW of domestic solar module production capacity according to https://www.utilitydive.com/news/onshored-solar-supply-chain... However, as context - the only purpose of producing solar modules is to generate solar power, and the US was the 2nd-largest producer of solar power in 2025 according to https://en.wikipedia.org/wiki/Solar_power_by_country Surely that makes us a leading player.

> [China] produces more than three quarters of global batteries

True but the US was the 2nd largest producer. In battery cells, we have an estimated capacity of 96 GWh in 2026. https://poweralliance.org/2026/03/18/american-energy-storage... Likewise in lithium-ion batteries: https://elements.visualcapitalist.com/ranked-the-top-lithium...

Weights should not be 0 (at least not frequently) but in a ReLU-based neural network, activations are 0 pretty often. You're absolutely right about die area though.

Hardware engineer here. Special casing the multiply by 0 and multiply by 1 paths is harder than it sounds. In software, the cost of adding special cases is simply performance. You're adding more instructions that execute in sequence on a CPU that already physically exists. Doing this for your multiply case is worthwhile because the speedup is large for 0 and 1 while the cost is not that large (relative to the time taken for the whole multiplication operation) for other values.

Hardware is different. Every operation that can be performed in hardware by a chip needs dedicated circuitry. Special casing 0 and 1 means adding at least OR reduction on each operand and a dedicated multiplexer for every bit of the output. Those transistors use power even when they're not in use (leakage power is a huge issue on modern semiconductor processes). They also degrade timing by adding more gates on critical paths through the multipliers. (The timing issue here is that all operations that happen between one flip-flop and another flip-flop need to finish within one clock cycle.) And unless there are whole blocks of 0's and 1's (this does happen in certain neural networks), you typically won't see a direct speedup anyway. In software terms, the matrix multiply is scheduled as many parallel operations that cannot be accelerated much overall by skipping a few operations in some "threads."

All of this makes zero skipping a nontrivial topic. People do still try to do it but it needs serious consideration as, depending on the application, the case is rarely one-sided.

Yes, but a car can't use electricity at 1 MV and converting the megawatt back to something lower than 1 MV still produces a lot of heat.

A mirror virus would not be able to infect normal cells. Viruses depend on (chiral) host cell machinery such as ribosomes to reproduce.

> Take a look at the structure of something like CMOS and you’ll see why running transistors in anything other than “on” or “off” is definitely not energy efficient. In fact, the transitions are where the energy usage largely goes. We try to get through that transition period as rapidly as possible because minimal current flows when the transistors reach the on or off state.

Sounds like you might be thinking of power electronic circuits rather than CMOS. In a CMOS logic circuit, current does not flow from Vdd to ground as long as either the p-type or the n-type transistor is fully switched off. The circuit under discussion was operated in subthreshold mode, in which one transistor in a complementary pair is partially switched on and the other is fully switched off. So it still only uses power during transitions, and the energy consumed in each transition is lower than in the normal mode because less voltage is switched at the transistor gate.

The main issue is that when objects spin really, really fast, they tend to explode due to centrifugal force.

The tensile stress on a spinning round, homogeneous object is p * r^2 * w^2, where p is density, r is radius, and w is angular velocity. Using your numbers for a steel cylinder with density 8 g/cm^3 gives a tensile stress of (8 g/cm^3) * (5 mm)^2 * (2pi*1 MHz)^2 = about 8 TPa which vastly exceeds the tensile strength of steel or any other known material. Using cows connected by ropes would be even worse because the enormous centrifugal force would be borne by only a small rope.

You're ignoring the units of G. The gravitational constant has units N * m^2 / kg^2 = m^3 / (kg * s^2). That contains a length unit raised to the third power, which exactly balances the factor of 8 that you identified.

Landauer's limit assumes that computation uses a thermodynamically irreversible process and erases bits of information. This is not necessarily true for all useful computers [0]. So theoretically speaking, it's not impossible to create an adiabatic microprocessor. Skepticism is definitely warranted though.

[0] https://en.m.wikipedia.org/wiki/Reversible_computing

To prove that it's possible to buy ads targeted on microphone audio. If this kind of targeting was really as widely available as the article implies, a journalist would be able to do it fairly easily and write an article about it.

In my experience, there are a lot of applications that are "trivial" enough that PID works fine. I'm reasonably comfortable with state space modeling for systems with more variables. But OK, I'll bite - always open to picking up something new. What resources would you suggest for someone who wants to learn more about nonlinear controls?

Nuclear energy is hardly the only power source that has made an entire city uninhabitable. The Banqiao dam failure flooded 30 cities and affected over 10 million people. https://en.m.wikipedia.org/wiki/1975_Banqiao_Dam_failure

Then there's Centralia, PA, which was turned into a virtual ghost town by a coal mine fire. https://en.m.wikipedia.org/wiki/Centralia_mine_fire

And we're not even considering the effects of global warming here. Sure, nuclear has risks, but our civilization needs energy and nuclear has proven to be one of the least risky ways to produce it.

Data scientist, I'd guess.

The most frequently discussed perovskite absorbers for solar cells are methylammonium lead trihalides, which are (at least partially) organic compounds.

Yes, it's thought that neutron stars are about 5-10% composed of protons and electrons. In fact, that's why a neutron star can have a magnetic field – charged particles are required to carry an electric current.

I agree that the comment you're responding to was off-topic, but calling it "Facebook-style misinformation" goes too far. It's well documented that the Obama administration sent multiple plane loads of cash to Iran in 2016. [0][1][2]

[0] https://www.cnn.com/2016/08/03/politics/us-sends-plane-iran-...

[1] https://www.wsj.com/articles/u-s-sent-cash-to-iran-as-americ...

[2] https://www.wsj.com/articles/u-s-sent-two-more-planeloads-of...

When nitrogen compounds combust, they tend to produce nitrogen gas (N2). Since nitrogen molecules contain a very strong nitrogen-nitrogen triple bond, a lot of energy is released when they form.

You'd need a lot of shielding. A planet is about the right order of magnitude, though it's still not clear that a human could survive. You wouldn't die of acute radiation poisoning; a few thousand km of rock would be enough to absorb the gamma rays. At 400 AU, you wouldn't immediately boil to death, either. Part of the collision-facing surface of the planet would be converted into plasma and ablated into space, which would insulate the rest of the planet from the worst of the heat.

My guess is that you'd still die from shock waves propagating through either the atmosphere or the planet itself, but it's difficult to predict the exact effects.

The question is currently closed, so I can't post a new answer. I voted to reopen it, and I've edited the title to focus on the aspect of the question that is not adequately answered by the duplicate.

Hi Ben, as the person who initially flagged your question as a duplicate, I'm sorry. I can see why this was frustrating. I'll try to provide a more detailed answer here.

According to a 1948 paper by Bekesy [0], a human ear can detect sounds through several mechanisms. In a gravitational wave, since the whole head would vibrate, sound would reach the ear by bone conduction through the skull. Fortunately, this also happens to be the most sensitive mechanism. The smallest vibration amplitude detectable by bone conduction is about 4 x 10^-9 cm at around 3 kHz. If a typical skull is about 17.5 cm from front to back, that gives a minimum detectable wave amplitude h (the fractional expansion and contraction of spacetime) of about 2 x 10^-10.

The frequency of the gravitational waves produced in a collision between a neutron star and a small black hole turns out to be pretty close to an optimal match for the human ear. To estimate the amplitude, the first black hole collision detected at LIGO produced a strain of about 10^-21 at a distance of 410 Mpc. (The events in the article were smaller, but within the same order of magnitude.) Thus, since the amplitude scales as 1/r, the gravitational waves from the collision in the article would have been theoretically audible at a distance of about 400 AU or 40 billion miles.

Alas, attempting to test this calculation experimentally would incur certain practical difficulties. Notably, you would be vaporized by gamma radiation from the collision several seconds before the gravitational waves became audible.

[0]: https://asa.scitation.org/doi/10.1121/1.1906433

Professional-managerial class. https://en.wikipedia.org/wiki/Professional%E2%80%93manageria...

Life, including spaceflight, would be pretty much the same as it is for us. Since the entire solar system would be moving, the relative velocities of the planets and moons would be the same as in any other solar system.

The rest of the universe would look quite different, though. Stars "ahead" of the solar system - in the path of its motion - would be noticeably blue-tinted and clumped together. Stars behind the system would be red-shifted. There are some great visualizations at [0].

[0] https://math.ucr.edu/home/baez/physics/Relativity/SR/Spacesh...

Rare earth elements actually aren't that rare. For example, neodymium makes up over 30 ppm of Earth's crust. That's more common than lead, cobalt, tin, thorium, tungsten, molybdenum, and quite a few other elements with large-scale industrial applications.

The difficult part of producing rare-earth elements is separating them from everything else. Tiny pieces of spacecraft dust scattered over a large area don't make very high grade ore...

The joke is that the Ramanujan sum of 1 + 2 + 3 + 4 + ... is equal to -1/12, so the check should be $3 * -1/12 = minus one quarter. [0]

[0]: https://en.wikipedia.org/wiki/1_%2B_2_%2B_3_%2B_4_%2B_%E2%8B...

Most commenters here seem to implicitly accept the framing of the discussion around stay-at-home orders as some sort of tradeoff between different values – for example, saving lives versus protecting the economy, or freedom versus safety. But has anyone considered whether stay-at-home orders have actually saved lives overall?

The UN estimated [0][1] that between 83 million and 132 million people will go hungry around the world because of anti-COVID measures. Some of these people will die from starvation or malnutrition. Some of them will die from other preventable health problems later in life.

According to the Stop TB Partnership, a three-month lockdown followed by a gradual return to normal over 10 months could result in an additional 6.3 million cases of tuberculosis and 1.4 million deaths between 2020 and 2025. [2][3]

It's also plausible that lockdowns could lead to hundreds of thousands of additional deaths from each of HIV/AIDS [4], malaria [5], and several other diseases, though I'm not as confident about these numbers.

I am sure someone will be tempted to respond with some variant on "we could have avoided these deaths by tuning the stay-at-home restrictions more competently." Of course, that's true; but the point is that we didn't. We never do. Historically, every society that has tried to eliminate "non-essential" jobs through central planning has eventually found that even when the planners operate with the very best of intentions, they still make mistakes. Dealing with one problem causes a cascade of other subtle changes with real, harmful consequences, which are harder to mitigate when people aren't allowed to freely choose how to spend their own resources. Meanwhile, problems that are judged to be less important are forgotten, because planners can only focus on a limited number of tasks at one time. Human societies are incredibly complex. Trying to manage them from the top is like developing software using the waterfall model: it would work perfectly with perfect planning, but we all know how that works out in real life.

On a personal level: a relative passed away from cancer recently. Cancer isn't a good way to die at the best of times; and I'll be honest, she almost certainly would not have survived even with better medical treatment. But if hospitals hadn't shut down "elective" and "non-essential" care, she could have gone through a lot less pain and suffering. I am not trying to use this as a bludgeon – I understand there are also a lot of people who have suffered greatly from COVID, and of course, we should make policy based on what's best for everyone rather than a small number of anecdotes. But when I read comments saying things like "I don't know how to explain to you that you should care about other people"... let's just say that I don't know how to respond to that without severely violating HN guidelines.

[0]: https://data.unicef.org/resources/sofi-2020/

[1]: https://africa.cgtn.com/2020/07/17/who-urges-world-not-to-fo...

[2]: http://www.stoptb.org/assets/documents/news/Modeling%20Repor...

[3]: https://www.nytimes.com/2020/08/03/health/coronavirus-tuberc...

[4]: https://www.who.int/news-room/detail/11-05-2020-the-cost-of-...

[5]: https://www.nature.com/articles/s41591-020-1025-y

Not the person you're replying to, but here are a few examples.

CNN: "Experts say travel restrictions the Trump administration put in place to stop the novel coronavirus from spreading could have unintended consequences that undermine that effort." (https://www.cnn.com/2020/02/07/health/coronavirus-travel-ban...)

The Atlantic: "Guiding Trump’s response is a hardheaded nationalism... Critics from WHO and elsewhere have said the bans are unnecessary and could generate a racist backlash against Chinese people." (https://www.theatlantic.com/politics/archive/2020/02/trump-r...)

Part of the reason is Paul Graham's essay about his experience using Lisp at a startup: http://www.paulgraham.com/avg.html