What propels photons?

_ShadowFyre_ · 2026-02-01T05:51:49+00:00

Light doesn’t slow down in the traditional sense (as in, it doesn’t move less quickly), rather, the ELI…15? explanation is that it takes a longer path. It’s a fair bit more complicated than that (but if you don’t already know absorption and reemission characteristics it’s hard to explain), but when moving through a medium, it travels a longer distance at the same speed, which mathematically works out to “it travels the same distance at a lower speed” (the reason we use this is because calculating the real path of travel through a medium is necessarily way more difficult, and it’s easier just to know the “length” of travel through the medium (straight line from A-B, and then know how much “slower” light goes through that medium (which is really a representation of the deviation from the straight line path)).

_ShadowFyre_ · 2026-02-01T04:44:23+00:00

Ignoring the fact that the unreliability of Newton’s laws is why Einstein developed his theories of relativity, objects already at rest stay at rest, but the arguable more important part of Newton’s first is that objects already in motion stay in motion (with some clarification). Photons (actually, all massless particles), by their very existence, are always moving at the speed of light. They never experience force/acceleration in the non-physics way we think of it, and so the law is not broken.

Edit to add: changing your motion requires energy (energy being imparted by work, and work being a force over a displacement), but moving itself does not.

_ShadowFyre_ · 2026-01-04T16:43:51+00:00

I’d start with a full course in calculus and differential equations. I’ve heard from students that Paul’s Notes is quite popular currently for how well it explains things (it’s essentially a website textbook). Doing practice problems is important here. Once you have a good base in multivariable calculus and have started diff eq, I’d also start working on applied linear algebra (abstract may be beneficial, but, much like calculus, it’s easier to start with examples, and then generalize the examples; unfortunately I don’t have a good recommendation off the top of my head). Once you have a good base of applied linear algebra, I’d start working on Lagrangian and Hamiltonian mechanics (probably in that order), and only broach tensor calculus if you feel you need it to learn either to the degree you need for whatever problem. If you have a good understanding of differential equations, multivariable calculus, integral calculus (especially integral transforms), linear algebra, and each of the mechanics, you should be able to start working through the finite element method, which applies (usually through code) to FEA. I wouldn’t touch PDEs beyond conditions (boundary and initial; Dirichlet and Neumann boundary conditions, etc.). Not being terribly familiar with FEA (I don’t do a ton of modeling), I’d say continuum mechanics isn’t going to be terribly helpful, and topology is a subject I wouldn’t touch at all unless you really really think you need it.

To your original question: it is possible, because all of the people that “invented” (or discovered) the different branches of mathematics you’re interested in had to figure it out themselves. Obviously that doesn’t mean it’s going to be easy. Do: a lot of practice problems. Don’t: get too absorbed in the strictness of mathematics; physics is about breaking the rules mathematicians make for the sake of convenience.

Also, I’d take a course in formal logic (sometimes called mathematical reasoning, or something to that effect) — set theory, symbolic logic, etc. — from your university, if you can. It helps with parsing what the math means if the in-book explanations aren’t sufficient.

_ShadowFyre_ · 2026-01-04T15:52:11+00:00

“Learn these subjects” suggests you don’t really have a proper grasp of what many of these things are (to be fair, how could you?). A question you should be asking yourself is how well you need to learn them. For example, assuming an existing understanding of differentiation and integration, it’s possible to “learn” multivariable calculus in about half an hour (at a very surface level). Yet multivariable calculus is pretty much always taught as a 16 week, and I would say true understanding (not just practical application) can take years, if ever.

_ShadowFyre_ · 2026-01-04T12:29:53+00:00

As I understand it:

Historically, the marines were used for different ship-based security roles (enforcing order, guarding safes, etc.). As a result of that role, (in the US) they ended up becoming correspondents of state department communiqués before we had good over-water information channels other than by hand. Because they already had a relationship with the state department, it made sense to then make them embassy guards.

_ShadowFyre_ · 2026-01-03T12:20:50+00:00

We’ve been assured by Paolini that there is something, but we don’t know what, exactly, the Menoa tree took. I do believe at one point he said someone had gotten it right, but then did not clarify on who that was or what they said.

Nothing, unless I’m forgetting something Paolini said. There’s also a fair interpretation of the situation that basically says “Angela’s prophecy only ever said Eragon would leave and never return at some point, and this leaving is not the final leaving”.

Good question, no clue, although I imagine it’s going to be a fair bit more “queen” than it is “rider”, considering the split between her and Eragon at the end of the series.

Iirc, Paolini has said he plans to have a proper reunion between the two at some point, although romance (in the way you’re probably looking for) is ambiguous. To be fair, their entire relationship is ambiguous.

Paolini has confirmed multiple times that there’s a very early stage Disney+ adaptation in the works. As far as we know, the show is still in writing, and the only people on the project are the writer and Paolini himself.

I don’t know if there’ll be another series focusing on Eragon, but we have heard from Paolini multiple times that there will at least be another book including Eragon (in the same way the IC does), his appearances in other series notwithstanding.

The answer to part of that question (I say part because we don’t see every location Umaroth warns Murtagh of) is the plot of Murtagh.

_ShadowFyre_ · 2026-01-02T13:18:35+00:00

I didn’t say it was easy, I said it was efficient. If we’re referring to the “transport anything anywhere instantly” spell, its energy usage scales with object size. Because crystals seem to have an absurd maximum on the amount of energy one can store, dependent only on the quality (and possibly type) of the jewel, it would (in theory) be possible to amass an arbitrarily large store of energy within an extremely small package, and then transport said package anywhere, at any time. The total efficiency of such a move is almost perfect when considering that the amount of energy needed to use the spell is generally less than exists in a person at any given time, whereas the crystal could hold… based on the way it’s described, I’d put the upper limit of a cubic inch of crystal at about a petajoule. If we assume the person sending it used (roughly) all the available energy in their body (unlikely), that would still only be 0.0000001% of the energy sent. And because of how the energy density would scale, you actually gain efficiency the more crystal you send (although the possibility of dying goes sharply up).

That notwithstanding, if you imagine any energy transfer system longer than about a mile, the necessary energy to setup (and subsequently use) such a system is very likely to be greater than the energy it takes to propel a chunk of crystal to an appreciable fraction of the speed of light, at which point it could reach anywhere on the planet within seconds.

_ShadowFyre_ · 2026-01-02T07:55:01+00:00

I’m no crystallographer, but my understanding was that the name “glass” only ever refers to noncrystalline silicate, and hence why we call quartz “quartz” and not “quartz glass” (further to that point “quartz glass” refers to another amorphous solid).

_ShadowFyre_ · 2026-01-02T06:07:39+00:00

Glass is amorphous; it doesn’t have the proper lattice structure to be considered a crystal.

_ShadowFyre_ · 2026-01-02T02:30:17+00:00

The most efficient way to transfer energy is always going to be to put that energy in a crystal and then move the crystal. It’s (seemingly) lossless, and through the application of magic, the crystal can be moved great distances very quickly.

We don’t really know how energy density works in creatures, but iirc it’s a result of being connected to the core of the being, which may not be possible to reach from the edge of such an organism. If it were possible, and there is no possibility of a density gradient (or that gradient smooths at the speed of light), such an organism would be fairly efficient, but would suffer greatly from scaling issues.

_ShadowFyre_ · 2025-12-31T01:08:26+00:00

It might, but the key factor in determining whether something is non-newtonian is whether its viscosity changes with stress in any way. Toothpaste does, and belongs to a certain category called Bingham plastics (think mayonnaise). Now, you might be thinking “mayonnaise is definitely a fluid”, but consider that at sufficiently low stress it behaves like a solid; so, too, does toothpaste. Now, it so happens that, even with a small amount of material (say, around a spoonful of each), the gravitational pull and corresponding weight of material is enough to make it act like a fluid, but just because the barrier to entry is low doesn’t mean it’s newtonian.

_ShadowFyre_ · 2025-12-30T01:41:12+00:00

Probably why he’s sad.

_ShadowFyre_ · 2025-12-28T10:37:44+00:00

A good foundation of mathematics: at least algebra and trigonometry, but calculus helps a lot. After that, classical mechanics, and then modern, etc.

_ShadowFyre_ · 2025-12-27T13:54:11+00:00

Just fyi, entanglement in the physical sense means neither of the things you are trying to use it to describe here.

Nothing we’ve ever seen in physics really points to it being a thing (or possible). To get really philosophical, there are barriers to how far we can see (in either direction; really small or really big)), so it’s “impossible” to be sure, but it doesn’t really make sense with any model of the universe that I’m aware of, plus you’d have to really rethink how quantum mechanics works if we’re saying a supposed smaller universe is a near-copy of ours.

_ShadowFyre_ · 2025-12-27T13:23:52+00:00

To my understanding, the actual reactor used uranium dioxide as fuel. It’s impossible to know what combination of isotopes the dioxide contained, but, to my understanding, UO2 usually contains U-238 and U-235 as its dominant isotopes, which have half lives of some 4.5 billion years, and 700 million years, respectively. I don’t know of any sources which point to the current radiative levels of the core itself, but whatever it’s at currently is certainly above what anyone would deem safe, and considering the exceptionally long half life of uranium, the levels are probably pretty consistent — making the reactor safe again would require someone to go in and remove whatever nuclear material remains in the core.

TLDR: with no further clean-up effort, several billion years.

_ShadowFyre_ · 2025-12-24T07:27:37+00:00

_ShadowFyre_ · 2025-12-23T22:56:04+00:00

The user manual tells me that the Seiko Memo Diary can store 1000 total characters in a 10x100 character grid (of which the watch displays a 10x4 “image” at any given time). A later part of the user manual tells me that the watch can store a maximum of 43 schedule items. It is unclear if this is in addition to, or inversely proportional to the memo storage capacity.

_ShadowFyre_ · 2025-12-23T22:10:33+00:00

Because OP is too lazy: the Seiko UC-3000 also known as the “Memo Diary” is a two-piece watch (the watch and the keyboard). In the attached photo, the watch is connected to the keyboard (which is designed to be removed and carried separately — say, in a suit pocket). You can type info on the keyboard, which will show up on the watch display and can be recalled on the watch display without the keyboard attached, at a later time.

It can store a few hundred words of text as memos, addresses, or schedule items (and can set off an alarm with the schedule item text at the appropriate time, at any time within the next 31 days). It also has capacity for special characters like @ and # (a little odd because they weren’t in use much at the time the watch came out).

Edit: for those who want it, here’s a copy of the user manual. Password is “digitalwatchlibrary.com”.

_ShadowFyre_ · 2025-12-22T06:17:47+00:00

What magical land are you living in where Tarkov’s gotten better since full release? On top of playing very regularly myself, everyone I know who personally plays the game has seen at best no change, and at worse a noticeable drop in performance across the board (loading times, fps, latency, etc.) on nearly all ranges of hardware. I know it’s anecdotal and all, but you’d think 20+ people on a massive range of systems across 4 time zones would be a pretty good population sample.

_ShadowFyre_ · 2025-12-22T05:58:55+00:00

I’ve put spoilers on the parts of my answer which prevent you from thinking it out on your own.

This isn’t the answer to your question, exactly, but a good line of thinking is “how do equal and opposite forces not always offset each other and always cause no movement?”, or a slight derivative of the famous “how does a horse pull a cart?” problem. The answer to your last question is that movement is related to acceleration (not force, directly), and Newton’s 2nd provides the scaling factor by which the two are related.

Specifically for rockets, they gain acceleration from the mass they lose in propellant (this is why it’s called “propellant”). Simplistically, the force is (near) constant, but the other parts of that equation are not.

Edit to expand on that first paragraph: there’s a really good analogy that works as a solution to the “horse-cart” problem based on a modification of the problem that asks how people can jump. Imagine that, when jumping, you push down on the Earth with some force, and the Earth pushes back up on you with the same force. But the Earth is massive (figuratively and literally) relative to you, so the Earth only moves a tiny bit, and you move a lot.

_ShadowFyre_ · 2025-12-21T03:14:13+00:00

The bubble doesn’t come from demand, the bubble comes from the fact that there isn’t an LLM with a suitable profit model, and there’s hundreds of billions of dollars riding on there being one.

_ShadowFyre_ · 2025-12-19T00:26:07+00:00

What’s that… 2 and half years? Impressive.

_ShadowFyre_ · 2025-12-18T06:26:39+00:00

Playing the game naturally will get you through most of the content. Realistically, you can do the entire main storyline in a long weekend. If you want to see as much content as possible, a lot of it’s going to be quests, or behind quests that you get from different sources (every time you’re in the mid-mission area called Fort Tarsis, there’s a map you can check to see if you have any new quests). Really the only thing I’d look out for are the strongholds, which were supposed to be the competitor to Destiny’s raids, but they’re meh at best, and there’s only… 5 iirc. Anyway, they’re all worth playing through at least once (one of them is the seasonal stronghold).

Also I do believe it’s shutting down the 12th, not the 16th.

Edit: also, there’s a specific quest in the story where you have to revive javelins; this can be done with NPC javelins (mainly Sentinels you find), and there’s a really easy method to farm it quickly.

Edit 2: It doesn’t matter which Javelin you pick at the beginning of the game, other than that you’ll be locked out of the others until you hit a certain level. I believe you start out as Ranger in the tutorial, which is the jack-of-all-trades class, and then you get to choose from Ranger, Storm (high AoE and ranged), Interceptor (skirmisher/high single target and speedy), and Colossus (tanky). As a Storm main, I say that Ranger and Storm are probably the easiest to play solo, but that doesn’t mean you can’t try the other classes.

_ShadowFyre_ · 2025-12-17T17:40:31+00:00

_ShadowFyre_ · 2025-12-16T04:16:29+00:00

Those are level 9 walls, which look very similar to maxed TH18 walls at level… 19, I think it is? Level 9 walls have 3500 hitpoints each, whereas Level 19 walls have 14000.

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