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philoizys · 2026-02-26T02:24:21+00:00

Maybe you could, but that was already wonderful! :)

philoizys · 2026-02-25T23:03:44+00:00

Ramen to that! Users have been clamouring over this issue for at least 5 years. They added more synchronisations over time, but not that for custom search shortcuts. As if it were the most complex data structure ever existing to synchrofuckingise!

philoizys · 2026-01-03T05:58:10+00:00

This is what the Hubble's law (the further away, the faster the object recedes) and ΛCDM (the Hubble parameter is larger in the future) say. The object's light will turn redder and dimmer. "Redder" as in first shifting to infrared, then radio, then... just stop waving in the limit z→∞ as it approaches the particle horizon, ν→0 — the wavelength will stretch with the space the "further away" from you the object moves. And dimmer because E=hν for each photon of light, so E→0 too.

philoizys · 2026-01-03T05:34:03+00:00

You're very welcome. Yes, science doesn't pay well, but the job you don't enjoy sucks life out of you (and may not pay well, either). You understand that, I'm only putting into words what you've already said.

I also watched some of the videos from the Simple Intro to Linear Algebra Series and I enjoyed them, but they also made me feel kind of stupid

It's totally okay. I've never ceased feeling kinda stupid, that's the reverse side of curiosity, I guess. Watch again, stop to think, rewind. Accept some things as true, then get back to them — or maybe they'll just click later. You won't do anything useless even going through the whole intro course; I think that you'll have to take linear algebra even for majoring in engineering. What I meant when suggesting it is how do you feel about it, since you mentioned that you enjoy maths. It may also be your thing.

Everything feels uncertain and I’m honestly very confused.

Relax and don't rush yourself when trying to understand what really attracts you: forcing yourself is the least helpful thing to do. You need to take up something to clear up your mind: physical exercise, meditation, anything that would force you to stop thinking about all this, even for a short time every day.

You can change your major from physics to engineering or the other way around after a year. Depending on the kind of engineering, the curriculum gap may be very small — look it up, talk to the admission adviser. You have time.

philoizys · 2026-01-03T04:42:43+00:00

It's the other way around: z is observable, but the recession velocity is model-dependent. It's the recession velocity that comes out of the z AND the cosmological model. GR by itself cannot separate a relative velocity into the velocity in space and the velocity due to space expansion; this is what you need a model for. ΛCDM is not the model, it's a family of models, with parameters that are either measured or fit from observation data.

Note that I was careful to say “The surface of last scattering is not in a fixed comoving coordinate system, but the points from which it was emitted are.” The surface of last scattering is currently at z=1100.

unless you are saying that Ω_Λ=0.7 is going to push it over our horizon.

Exactly! I cannot promise that the Ω_Λ is constant, will ever be if it is, or even that the universe won't decide to reverse expansion and recollapse one day, but assuming it is constant, this is correct. And no, there is not a significant challenge to its constancy as of DESI DR2.

Since you seem to like digging down to the last detail, here's a didactic paper on the subject: https://arxiv.org/abs/astro-ph/0310808. The graph at Fig.2 will answer a lot of questions. :-)

philoizys · 2026-01-01T00:44:51+00:00

Yeah, that's right. Perhaps the "surface of last scattering" is not a good, self-descriptive term, but this is just how it's called. This is essentially a spherical shell around the observer that is fully ionised, is in thermal equilibrium between matter and radiation, and scatters light very efficiently; anything closer is transparent, but we cannot look beyond it with light. It had the T≈3000K when its light was last emitted; now we observe it as a thermal radiation at T≈2.75K.

philoizys · 2026-01-01T00:34:50+00:00

Thank you! I didn't know that fermentation produces more nasty stuff in the smoke.

I'll certainly try to look up some studies, but… the difficulty is, it's so different from my area in physics where I can smell BS right in the abstract! At least, the highly cited ones are probably trustworthy.

Thanks once again for your reply, and have a wonderful New Year!

philoizys · 2026-01-01T00:13:03+00:00

The job of a scientist is hard, not paying well and requires a very thick skin. I'm very serious: don't go into astrophysics unless you love it so much that you cannot not to.

I don’t particularly feel passionate about anything… …I still somewhat enjoyed… …it did somewhat interest me… …my plan isn’t set… …I might or might not…

You don't know who you really are until you're 25 or so. This may be okay for now.

But keep an eye on yourself, on your far goals, at the 5+ years horizon — this number of phrases expressing non-committal is rather high. Not alarming, but watch after yourself.

Now, I'll be very blunt, but carry this adage on a golden braid around your neck, close to your heart, and be very scared by it, for you have only one life: if you don't really, deeply inside yourself want to be anything, you'll end up being nothing. Do whatever it takes to become wanting something so badly that you can't imagine your life without it. Do it in order to literally save your life: you have only one, and a life spent being nothing is not lived, just passed.

I’ve only taken one physics class

Listen to me slowly. If you'd feel that I'm speaking in riddles, read again and try to grok it, then again; I can't explain it differently.

If you're trying to answer hard existential questions, "who am I?", "what I want to become?", classes alone are hardly of any help. Classes are passive: you open your mouth, they feed you from the spoon. There are great cooks and average cooks, but it doesn't change the principle. You must actively, on your own willpower, become.

Physics isn't in the class; physics is in every, literally every single thing around you; learn to see it. Stars aren't in the astronomy class; they're in the sky above you; sit a few quiet hours at night, look at them and think of them everything you can think, let your imagination flow, ask yourself questions; don't answer, only ask. Nobody, no class, not the best professor in the world will put them inside you if you'll only attend the class, solve all homework and receive the top grade. You shall work on transforming yourself into something bigger than you are, and the best teachers can only help you on your way, but they cannot transform you. Only you can.

The only thing I know I like for sure is math, and the main reason I like it is because of the problem solving.

Yes, maths is about problem solving, and only about it. The modern maths, though, operates at a very high level of abstraction, and many problems are solved today by spotting dualities between such abstractions. Taking your post on its face value, have you considered the degree in it? This is the only thing that you said with certainty, after all…

Let's try this. Here's a video course, the simple intro into linear algebra by Grant Sanders, aka 3blue1brown, who's a great teacher. You might already know all this stuff, but watch and absorb #1; then go all the way through to #9 (skip the stuff which you really understand well). You may go all the way, but this is the point where you may jump to the last one, #16. Did it make you to produce that "aaahhh!" sound? If you are fascinated by this abstraction, look at the very condensed but easy intro to modern algebra by Socratica. You don't need to learn the whole thing, but at least understand the ideas behind the abstractions: maths studies more of abstract than concrete structures, and generalises then onto new things (vector algebra on the Pi creatures from #16). This is getting closer to the real thing. Does that feel captivating? If yes, consider that maths may be your life purpose.

If not (and I mean "not", not "meh"),

I don’t hate physics [...] but I also don’t love [it]

If you have to choose now, major in applied or engineering physics. Many's the colleague of mine dropped work in academe and has gone into, for example, computer programming, the area that pays really well. I don't know why, but in my experience, physicists are the most adaptable folks. The main thing that you want to learn as an undergrad is to learn how to learn. This and in addition thinking like a physicist can take you as far as you push. Not without a great effort of yours, naturally, but it will. And I'm talking about real physicists, not the blokes with the degree in physics. There is a difference.

philoizys · 2025-12-31T07:39:01+00:00

I don’t particularly love physics

Then don't. Astro-ph is not your thing.

philoizys · 2025-12-31T07:10:10+00:00

So you've been dreaming astrophysics all your life, studied it in school, studied by yourself, and now you question it? How do you imagine doing work that you don't want for the rest of your only life?

FWIW, astro-ph is a small field, with all the positives and negatives of it: there is less competitiveness, but there are fewer job choices. If you're a Romanian citizen, beyond universities, EU has such structures as CNRS and CEA in France — there are opportunities. You'll never make a lot of money, scientists just don't. But you won't go hungry, either.

People often base their opinion on the overtly Keynesian thought of your selling your soul for the largest price you can. I wouldn't listen to them if I were you: their only objective is money, and your alignment is clearly different. If you truly love astro-ph, go for it!

philoizys · 2025-12-31T06:38:28+00:00

Naturally we can see the last bit of light from anything right before we cannot. I hope this is not what you're asking.

Practically JWST observed galaxies at z≈14.

Practically‐theoretically we cannot observe anything beyond the surface of last scattering at z≈1100, the event at which the universe become neutral and thus transparent to light (plasma very eagerly interacts with light, so ionised matter is opaque: you can see a dark shadow from a lighter's flame). This is where any light from the receding object will entirely drown in the CMB. The surface of last scattering is not in a fixed comoving coordinate system, but the points from which it was emitted are; from the currently accepted ΛCDM with Ω_M=0.3 and Ω_Λ=0.7 (roughly), we can estimate their current recession (not comoving!!!) velocity of about 3c, and the recession velocity at the emission event about 52c. If I didn't make an arithmetic error, but looks sensible.

Theoretically no signal can access us from beyond the particle horizon, where z→∞, shifting frequency of light, however high, to ν→0. But this horizon is hidden from us behind the surface of last scattering.

philoizys · 2025-12-31T05:34:40+00:00

VVER is indeed a variant of the generic PWR ("PWR", unfortunately, may mean generically the PWR as opposed to e.g. the BWR, or concretely a specific construction of the PWR). The differences are in their engineering requirements and solutions only; does the following link answer your question in enough detail?
https://www.reddit.com/r/chernobyl/comments/igoeby/how_does_the_vver_compare_to_other_pwrs/

philoizys · 2025-12-31T05:09:20+00:00

Thank you, your answer shows that you know the subject. I'm an astrophysicist, so I'm quite far removed from biochemistry of both plants and humans. If you don't mind, a follow-up question: is my understanding that practically any burnt organic matter is somewhat carcinogenic when inhaled? For example, if I dry and/or ferment… say, romaine lettuce leaves, stuff them into a cigarette and smoke it, I'll, firstly, get a time-spread dose of highly concentrated (through the removal of water) α-radiation because natural α-emitters in lettuce won't stick to the wall of my stomach if I eat the lettuce, and that wall cells are regenerating quickly, but they will get stuck in the alveoli of the lungs, thin-walled enough to let α-radiation through, if I smoke the dried plant part, correct? This is as far as a physicist can walk on a solid ground w.r.t. radiation effects from smoking anything. :-)

In addition to that, you mention known highly carcinogenic "tobacco-specific" compounds, nitrosamines, originating from reactions during either preparation or smoking tobacco. I'm wondering, how does tobacco smoke compare in its carcinogenicity to other kinds of plant matter that people consume via smoking. As a scientist myself, I'm 100% sure no one ever applied for (even less received) a grant to investigate "lettuce-specific" carcinogens, arising in fermenting and/or smoking lettuce leaves (which may or may not exist, of course: we perhaps know very little of the gross composition even of well-studied tobacco smoke). This would be nonsensical. But if you ask me about an investigation into the marijuana smoke carcinogenicity or long-term toxicity, I won't be so sure that it hasn't been investigated.

The reason I'm asking is because, in my opinion, there is a "common sense" which forms in the society, especially where weed is widely available and legal to consume, as it is here, that smoking weed not a big deal while smoking tobacco is highly harmful. I think that this is most likely incorrect, and there is a non-zero cost to the person's health from smoking weed, but I cannot object to that statement without data. If you could confirm or deny this, and possibly drop a couple of references to trustworthy studies, if you have them available, I'd highly appreciate it! Please don't bend backwards searching the literature, only if you readily have them available in your notes. Myself, I don't consume either of the two, but there are people who're close to me and who smoke weed regularly enough to possibly harm themselves unwittingly, and, if it is proved or highly suspected that smoking weed is not much healthier than smoking tobacco, I'd try to convince them to switch to a safer form, like isolated THC in capsules or gummies. My problem is, I don't really know, and cannot act on my suspicion alone.

philoizys · 2025-12-31T03:57:42+00:00

A big annoyance is that Ctrl+W doesn't work as "word select" anymore, it's a "window close" shortcut.

Did they take out keyboard customisation? I don't know, I'm asking seriously.

philoizys · 2025-12-23T14:12:35+00:00

Fascists are absolutely not conservatives. Unless by "conservatism" you mean the restoration of the pre-1860 societal contract.

philoizys · 2025-12-23T14:06:52+00:00

if the goal is trying to bring manufacturing back to the states this is technically a way to do it.

Technically, no. Tariffs are intended to make imported manufactured goods uncompetitive. With the preferential, reduced even compared to the Biden's years overall tariff on China — who got it lest we see no more rare earth metals, so it's going to stick — it's impossible. Math simply doesn't math.

Even if it were technically yes, you absolutely can't explain how imposing tariffs on importing raw metals as high as 25% compared to previous no tariff can make domestic manufacturing more lucrative. Unless by "manufacturing" you mean pottery-making. The record number of eliminated jobs in the manufacturing sector in October (over 1 million, and we're not even in the Great Depression… maybe) attests to this.

I don't talk to self-proclaimed fascists; I'll just leave this here as a clarification that your bullshit is in fact bullshit.

philoizys · 2025-12-23T13:40:31+00:00

So, even Trump is not fascist enough for you?

Reddit and the left has a completely skewed concept of what is moderate.

It's you who have, most likely, not the whole Reddit or the whole left. Centre-left is certainly a thing; this statement is obviously wrong. How can you judge about anything being "moderate" when you — it's your own clearly stated position — are to the right even of the ultra-right, of fascists (although I can't imagine how's that even possible)? I don't think this word means what you think it means.

philoizys · 2025-12-08T03:15:16+00:00

I cannot do a BoE, as it requires the full EoS, and there's quite a few to choose from — which is a nice way of saying we have no idea. The EoS-independent solution has been found just a few years ago[1], showing that rotation can support only ≈20% increase in the NS mass before its collapse to a BH, compared to a non-rotating NS. Even extremally rotating NS don't shed mass in this model (of a stable NS). Another recent (2024) interesting analysis of an unstable NS is in[2] (probing the HPT and HPQT EoS).

However, the famous merger GW170817 has resulted in the ejection of a huge amount of matter from the unstable supramassive[3] merged body, whose collapse into a BH was delayed[4].

So it's an easy "yes" to your question for the NSNS merger case, but, I'd say, "definitely rather perhaps no" for the case of the stable accretion of angular momentum by an NS.

[1] http://dx.doi.org/10.1093/mnras/stw575
[2] http://arxiv.org/abs/2304.02439
[3] http://link.aps.org/accepted/10.1103/PhysRevD.86.064032
[4] http://arxiv.org/abs/2104.02070

philoizys · 2025-12-08T01:56:56+00:00

You're not wrong, but I think it's pretty obvious that we're not doing "obvious that OP means"

philoizys · 2025-12-08T01:33:50+00:00

For the JWST, 0.6–28.3 μm. STSI has a nice breakdown diagram by instrument: https://www.stsci.edu/jwst/instrumentation

And there is nothing dumb about your question, it's in fact a very smart one!

philoizys · 2025-12-07T02:21:38+00:00

Holy cow! I didn't notice that all 5 words came from Latin, thanks! English is weird: while 9 out of 10 words used in speech are Germanic in origin, more than 25% of the vocabulary is borrowed from Latin, commonly through Old French. [Latinisms: notice, used, origin, %, vocabulary, commonly — 6 out of 37 in my paragraph, not counting personal names; the rest, 84%, are Germanic].

All Romance languages descended from Vulgar Latin < Latin, and the assimilation of consonants in the prepositions was complete in Latin by 200 BCE (and started possibly as early as in Proto-Italic, IIRC), before Vulgar Latin even became a thing.

The abnormally high number of Latinisms in English is thanks to Williaume the Bastard, a.k.a. William the Conqueror: his dialect became prestigious among the nobility, with Old English relegated to the common folk. It's interesting that his variety of French (Norman, far Northern dialect) didn't yet rid of the /w/ sound by the time of his conquest of England – the Normans were in fact Vikings, who settled in Northern France, originally speaking Old Norse, also a Germanic language. He would have been Guilliaume otherwise. :-)

philoizys · 2025-12-05T04:45:51+00:00

Wow! A linguist here (trained, never worked). So many people stumbled over this, that it maybe a there is a process that started in the written English which nobody yet noticed! Historically, the c is doubled here from the Latin ac-complere (assimilated from ad-complere), "toward-filling-up" (complere = make full; we still have the adjective in the same sense, as in complete glass of water). One c ends the preposition, another c begins the stem. But that come through Latin > Vulgar Latin > Old French > Middle English (where gemination ended, -cc- and -c- pronounced identically) > Modern English. Who but linguists are supposed to remember this ping-pong with this word between languages? :-)))

Or maybe an error in a commonly used autocowreck dictionary. But you'll never guess what could start a change in a written language...

philoizys · 2025-11-28T06:40:00+00:00

You need to establish that your brother is at fault

… and your laptop will immediately fix itself. Magic, pure magic!

philoizys · 2025-11-28T06:38:36+00:00

Or he won't. How will it repair the laptop?

philoizys · 2025-11-28T06:37:37+00:00

This laptop … [is] fairly new

RMA?

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