You can, in fact, tax exports. It's prohibited in the US constitution but that's not such a big problem anymore. Nvidia's exports to China are taxed.

Because the US exports mostly services and IP.

I have my very common first and last name. I've gotten class lists with names, addresses and phone numbers, some woman's security system notifications ("Karen has gone to bed for the night..."), and one time a shady real estate development company added me to their dropbox with all their shady plans and accounting.

ED: "But it doesn't work for gravity with linear curvature"

Relativity = gravity is represented by the curvature of spacetime. Curvature is linear, R. The formula treats curvature linearly. As things get closer and curvature spikes, the math just scales at a 1:1 rate

Quadratic gravity = Squares the curvature. Doesn't really change things much when everything is far apart, but heavily changes things when everything is close together.

Pros: prevents infinities and other problems when trying to reconcile quantum theory with relativity ("makes the theory renormalizable"). E.g. you don't want to calculate "if I add up the probabilities of all of these possible routes to some specific event, what are the odds that it happens?" -> "Infinity percent odds". That's... a problem. Renormalization is a trick for electromagnetism that prevents this by letting the infinities cancel out. But it doesn't work with linear curvature - gravitons carry energy, which creates gravity, which carries more energy... it explodes, and renormalization attempts just create new infinities. But it does work with quadratic curvature - it weakens high-energy interactions and allows for convergence.

Cons: Creates "ghosts" (particles with negative energies or negative probabilities, which create their own problems). There's various proposed solutions, but none that's really a "eureka!" moment. Generally along the lines of "they exist but are purely virtual and don't interact", "they exist but they're so massive that they decay before they can interact with the universe", "they don't exist, we're just using the math out of bounds and need a different representation of the same", "If we don't stop at R^2 but also add in R^3, R^4, ... on to infinity, then they go away". Etc.

The theory isn't new, BTW. The idea is from 1918 (just a few years after Einstein's theory of General Relativity was published), and the work that led to the "Pros" above is from 1977.

Your comment has nothing to do with the fact that mass is explicitly part of the source term in Einstein's field equations.

The belief that mass is not a source term for gravity is absurd, and also non-physical.

Which is also mass density.

Sort of. The stress-energy tensor for a single isolated photon has rho > 0. Does that mean the OP is correct and photons have mass? You can say yes and go handwavy about "relativistic mass" or "effective mass" or, as the OP did "abstract mass" but it gets very inconsistent. It's energy, which in some (but not all) circumstances is also mass.

I was going to say that the Woz/Jobs duo has become such an archetype because the different sides of computing can project themselves onto it. The geeks give Woz all the credit, the suits give it to Jobs. As someone who thinks lots of people would be happier and more productive working for themselves I'll project that and give credit to HP for pissing them both off enough to go off and do their own thing.

If you haven't read it, The Hacker Ethic by Pekka Himanen is a good read, and relevant:

https://ia801301.us.archive.or...

Qt is a GUI toolkit that can, but doesn't have to, duplicate the look of the native GUI toolkit. Electron is Node + Chromium shoved in a box with your javascript. You being able to make it look like whatever you want is supposed to be a feature. Microsoft could easily do the same thing just by releasing their own collection of HTML widgets with Windows styling.

The real problem with things like Electron is that they just chuck Node and Chromium in a box with your javascript. They're Google's everything-will-run-in-the-browser plus the brilliant idea of including both the browser and the server in every executable.

A bit more about the latter. Beyond organophosphates, the main other alternative is pyrethroids. These are highly toxic to aquatic life, and they're contact poisons to pollinators just landing on the surface (some anti-insect clothing is soaked in pyrethrin for its effect). Also, neonicotinoids are often applied as seed coatings (which are taken up and spread through the plant), which primarily just affect the plant itself. Alternatives are commonly foliar sprays. This means drift to non-target impacts as well, such as in your shelterbelts, private gardens, neighbors' homes, etc. You also have to use far higher total pesticide quantities with foliar sprays instead of systematics, which not only drift, but also wash off, etc. Neonicotinoids can impact floral visitors, with adverse sublethal impacts but e.g. large pyrethroid sprayings can cause massive immediate fatal knockdown events of whole populations of pollinators.

Regrettable substitution is a real thing. We need to factor it in better. And that applies to nanoplastics as well.

So, when we say microplastics, we really mainly mean nanoplastics - the stuff made from, say, drinking hot liquids from low-melting-point plastic containers. And yeah, they very much look like a problem. The strongest evidence is for cardiovascular disease. The 2024 NEJM study for example found that for patients with above-threshold levels of nanoplastics in cartoid artery plaque were 4,5x more likely to suffer from a heart attack. Neurologically, they cross the brain-blood barrier (and quite quickly). A 2023 study found that they cause alpha-synuclein to misfold and clump together, a halmark of Parkinsons and various kinds of dementia. broadly, they're associated with oxidative stress, neuroinflammation, protein aggregation, and neurotransmitter alterations. Oxidative stress is due to cells struggling to break down nanoplastics in them. They're also associated with immunotoxicity, inflammatory bowel disease, and reproductive dysfunction, including elevating inflammatory markers, impairing sperm quality, and modulating the tumor microenvironment. With respect to reproduction, they're also associated with epigenetic dysregulation, which can lead to heritable changes.

And here's one of the things that get me - and let me briefly switch to a different topic before looping back. All over, there's a rush to ban polycarbonate due to concerns over a degradation product (bisphenol-A), because it's (very weakly) estrogenic. But typical effective estrogenic activity from typical levels of bisphenol-A are orders of magnitude lower than that of phytoestrogens in food and supplements; bisphenol-A is just too rare to exert much impact. Phytoestrogens have way better PR than bisphenol-A, and people spend money buying products specifically to consume more of them. Some arguments against bisphenol-A focus on what type of estrogenic activity it can promote (more proliferative activity), but that falls apart given that different phytoestrogens span the whole gamut of types of activation. Earlier research arguing for an association with estrogen-linked cancer seems to have fallen apart in more recent studies. It does seem associated with PCOS, but it's hard to describe it as a causal association, because PCOS is associated with all sorts of things, including diet (which could change the exposure rate vs. non-PCOS populations) and significant hormonal changes (which could change the clearance rate of bisphenol-A vs. non-PCOS populations). In short, bisphenol-A from polycarbonate is not without concern, but the concern level seems like it should be much lower than with nanoplastics.

Why bring this up? Because polycarbonate is a low-nanoplastic-emitting material. It is a quite resilient, heat tolerant plastic, and thus - being much further from its glass transition temperature - is not particularly prone to shedding nanoplastics. By contrast, its replacements - polyethylene, polypropylene, polyethylene terephthate, etc - are highly associated with nanoplastic release, particularly with hot liquids. So by banning polycarbonate, we increase our exposure to nanoplastics, which are much better associated with actual harms. And unlike bisphenol-A, which is rapidly eliminated from the body, nanoplastics persist. You can't get rid of them. If some big harm is discovered with bisphenol-A that suddenly makes the risk picture seem much bigger than with nanoplastics, we can then just stop using it, and any further harm is gone. But we can't do that with nanoplastics.

People seriously need to think more about substitution risks when banning products. The EU in particular is bad about not considering it. Like, banning neonicotinoids and causing their replacement by organophosphates, etc isn't exactly some giant win. Whether it's a benefit to pollinators at all is very much up in the air, while it's almost certain that the substitution is more harmful for mammals such as ourselves (neonicotinoids have very low mammalian toxicity, unlike e.g. organophosphates, which are closely related to nerve agents).

Maybe in the book. In the movie there is no science.

Although I don't think I can come up with ANY plausible explanation for the magical bugs.

Lots of people could and did design and/or build personal computers in the 70s. Magazines published designs and sold mail order kits pior to the Apple I. There were also a bunch of pre-built home computers contemporary with the Apple I/II, and several of them were more popular.

Neither Steve was really the singular genius people like to retrospectively paint them as. Together they did good work and were in the right place at the right time with the right motivation.

Which is also mass density. Multiply by c to keep the units straight. (If you're a physicist, you just set c=1, and the units don't matter.)

I guarantee, if you have a mass density of M kg/m3 and you put it in Einstein's field equations, you get gravitation.

No, the box is an essential part of the system. In the thought experiment neither the box nor the photon has mass but both possess momentum since the photon can bounce off the walls of the box. The photon and the box, together, form a system that has mass.

You can see how systems can have mass by rearraning the mass-energy equivalence equation to solve for mass:

m = sqrt(E^2 - (pc)^2) / c

The energy and momentum of a fundamental particle are related so you can't manipulate them independently. But if you have more than one particle it's pretty easy to manipulate the momentum of the system without changing the energy, and thus make m non-zero.

Many teachers, including the pop science variety, like to appeal to your intuition. Sometimes that's okay, sometimes it just stunt's your understanding. Your idea of mass is rooted in pre-20th century physics. The end of the 19th and beginning of the 20th century changed how we think about a lot of things, mass included. You're trying to take your idea of mass as an axiom and make everything else fit. It doesn't. Photons are massless. If they weren't, they would either not travel at the speed of light or have infinite energy. The "thing" that gravitates is energy and various types of energy flux, including momentum. That explains, consistently, how photons can travel at the speed of light, massless particles can interact via gravity, and adding energy to a system can increase its mass.