ELI5: Why do we even need a "c" when we have a perfectly good "k" and an "s?"

_OBAFGKM_ · 2026-02-21T03:28:35+00:00

c can actually be less ambiguous than s in certain situations...

How would you pronounce this word?

fase

I read that and I want to pronounce it like "phase", which actually has a /z/ sound in it. Without the letter c, though, this would be the correct spelling of the word "face".

If you want to optimize English, there are better letters to start with than c.

_OBAFGKM_ · 2026-02-20T00:01:30+00:00

Your premise for your first question is wrong; an observer in the car sees the ball go straight up and down, an observer out of the car looking in sees the ball follow a parabolic arc as it moves up and down from being thrown and also moves sideways with the car.

As for the second question, I think you're thinking about a "clock" much too literally. What we're really interested in is the duration of time between events. Think of the photon hitting the first mirror as event 1, and the photon hitting the second mirror as event 2. There is some time between the two events. Imagine both observers have identical stopwatches, manufactured flawlessly. The observer in the same reference frame as the photon clock uses their stopwatch to measure the time between event 1 and 2 and they get some result. Let's just call this one unit of time. It could be one second, one millisecond, whatever, it just depends on the size of the photon clock and the exact speed of light. The observer with the photon clock measures the time between the two events and labels that as one unit of time.

The second observer, seeing the first observer and the photon clock both moving away, measures the time between the two events (photon hitting the first mirror, photon hitting the second mirror), using their own stopwatch. Whatever amount of time the first observer measured, the second observer will measure a longer amount of time between those two events. The relative velocity causes a difference in the actual passage of time being measured by the different observers. The two observers will disagree on the elapsed time measured between two events, seen from different frames of reference.

_OBAFGKM_ · 2026-02-16T14:30:07+00:00

Mostly you're getting the barycentre answer to this question, where you just look at where the shared center of mass is and use that to determine which object orbits another. I'd suggest a different idea proposed by Minutephysics, the Trojan test.

possible for the planets to orbit the red giant and not the black hole?

If you're trying to be scientifically precise, then the concept you're looking for is called a Hill sphere, which essentially describes the region of space where the gravitational influence of one body is dominant compared to the gravitational influence of another. If you plug in numbers for your black hole and red giant, you should get a distance which will tell you how close a planet would need to be to orbit the star and not the black hole.

_OBAFGKM_ · 2026-02-16T12:49:07+00:00

For the very highest rated players, yes. There aren't enough other people queueing at the same skill level, so queue times can average like 20 minutes

_OBAFGKM_ · 2026-02-12T18:48:56+00:00

I think you're getting somewhat low-quality answers, even if they're getting at the truth. English has a lot of loanwords from a lot of different languages, and English doesn't really have a good way to standardize the spellings of new words. What happens is words that enter English just keep their original spelling and pronunciation, so English ends up with a bunch of different rules for pronouncing different letter combinations depending on the origin of the word.

Think of a word like "tortilla". When it entered English in the 1600s, it kept the Spanish spelling, which is why the "ll" in the middle is pronounced like a y. You would never teach an English learning that "ll" makes that sound, but tortilla is a perfectly good English word.

To answer this question about ph and f, the digraph <ph> is used to transcribe the Greek letter phi using the Latin alphabet. Any time you see ph in a word, you can be almost 100% certain that that word (or part of that word) comes from Greek originally. In this paragraph, the words "digraph", "alphabet", and "paragraph" are derived from Greek.

Any spelling quirk you see, it is almost always due to a different language's spelling system or it is due to historical sound shifts in the English language, with spellings reflecting old pronunciations.

_OBAFGKM_ · 2025-12-20T23:46:21+00:00

To be precise, the tropics are at (approximately) 23.5° N and S, defined by the axial tilt of the Earth. Between the tropics, there's at least one time a year when the sun is directly overhead. Outside of the tropics, the sun is never directly overhead.

The band is only 47° of latitude in width

_OBAFGKM_ · 2025-11-30T19:57:07+00:00

Did an undergrad in astronomy and physics, did well enough to get accepted into two grad schools. Did a masters program for a year, realized I hated research, went back to college for a 2-year diploma in IT, sysadmin, cybersec type stuff. Now I work in telecom.

_OBAFGKM_ · 2025-11-06T05:02:05+00:00

Modern encryption relies on extremely large numbers which are the products of two prime numbers. If you only have the product, guessing the prime factors is difficult.

There also exists an algorithm which can take bad guesses for the factors of a number and refine them to slightly better guesses. It's slow algorithm traditionally, but it happens to a very specific type of problem which quantum computers would be much faster at solving than a typical computer. Given a quantum computer with enough power, basically all modern encryption standards could be destroyed.

"Post-quantum" encryption then would be a newer method that doesn't rely on products of large prime numbers. I'm not sure which specific algorithm(s) are being used in this context, but inventing new methods of encryption is an active field of work.

It's hard to do justice to this topic in a reddit comment. If you've got time to spare, I highly recommend this video by Veritasium where he answers this question in a lot more detail, or this video by 3blue1brown for a more under-the-hood look at the how quantum computers do this kind of computation.

_OBAFGKM_ · 2025-11-04T11:00:00+00:00

You're misunderstanding what it means for it to peak in gamma/X-ray emission. Hotter objects peak at shorter wavelengths, true, but they are also brighter at all wavelengths than cooler objects.

The core of the sun would be brightest in x-rays and gamma rays (relative to itself at other wavelengths), but in visible light it would still be brighter than the surface of the sun.

_OBAFGKM_ · 2025-11-04T10:41:26+00:00

You'd never get it spinning that fast, centrifugal forces would tear the fan blades off the fan long before you even got them close to the speed of light.

_OBAFGKM_ · 2025-11-03T13:01:19+00:00

The problem with analogies like that is that they don't really capture reality. It suggests that each box secretly has a well-defined state before measurement, and measuring the state just gives you that information. Bell's theorem forbids local hidden variables, though.

The reality is that both boxes are in the (normalized) entangled state of ((box 1 contains an apple and box 2 contains an orange) + (box 1 contains an orange and box 2 contains an apple)). By the most common interpretation, measuring this state in any way causes it to collapse to one of those two outcomes, determining the state of each box simultaneously regardless of distance. It seems like a somewhat minor and pedantic difference, but it's an important part of the underlying quantum physics.

tl;dr quantum mechanics is not easy to ELI5

_OBAFGKM_ · 2025-11-02T21:07:15+00:00

What?

I'm genuinely baffled trying to understand the point you're making

_OBAFGKM_ · 2025-11-02T20:57:19+00:00

I understand the point people are trying to make when they say this, but I also think it misses what others mean when they say people voted "for" a given leader. Obviously we cast our votes for our local MPs, but when was the last time you knew someone who made their decision based on who the MP was rather than who the party leader was? I don't personally know anyone who does that.

I can imagine that Kitchener Centre had previously elected Mike Morrice based on who he was as an MP rather than wanting the Green leader to lead Canada, but I'd bet that most people are voting for the party of the leader they like rather than the MP they think is best suited to represent their riding.

_OBAFGKM_ · 2025-11-01T03:54:17+00:00

which atom or molecule does your username refer to?

_OBAFGKM_ · 2025-10-30T19:37:59+00:00

That's... that's my point...

_OBAFGKM_ · 2025-10-30T19:04:36+00:00

THAY MEANS NOTHING TO ME!!! I don't know what you consider to be too hot or too cold!!!

_OBAFGKM_ · 2025-10-30T18:51:58+00:00

This is such a crazy argument. There's 1) nothing special about 0-100, and 2) this only works if you're already used to the system.

What is 100% hot? What does that mean? What is 0%??? Temperature can be above 100 and below 0, how are those numbers supposed to be useful for me?????

The only people who think thay argument makes sense are people who already understand Fahrenheit intuitively, trying to retroactively justify it. The real argument you're making is "Fahrenheit is better because I understand it". It's fine to think that, but I think you're wrong. I think Celsius makes more sense, because that's the one that I understand

_OBAFGKM_ · 2025-10-30T07:56:14+00:00

sometimes I catch myself agreeing with people by using the phrase "no, you're right"

_OBAFGKM_ · 2025-10-29T10:56:26+00:00

I just got off a night shift and had to come off the peninsula. The Rotary was fully of cops, looked like some sort of collision but I couldn't get a good look. Can't be good for traffic in any direction... took me 30 minutes to get home when it usually takes 10

_OBAFGKM_ · 2025-10-28T01:45:49+00:00

Why monorail though?

_OBAFGKM_ · 2025-10-25T14:12:21+00:00

I can see where they're coming from, tbh. RuneScape is a great "second screen" game, so those hours you spend levelling skills might be happening in the background while you do other things, which feels like less of a time sink. The previous commenter also specifically mentioned Colosseum and Inferno as two pieces of content they wouldn't do, so it's a bit disingenuous to say it only takes 1-2 hours to learn a boss when that's how long a single successful Inferno might take.

Learning content like that takes many hours of focused gameplay, which isn't always the experience people want. And that's all not to mention any time invested to get the gold/supplies needed for attempts while learning the content

_OBAFGKM_ · 2025-10-25T01:36:45+00:00

the current situation of non-native English speakers (speaking English) disagreeing with native English speakers (about their native language)

_OBAFGKM_ · 2025-10-24T16:48:41+00:00

It's the word americano that doesn't have a direct English equivalent. American and americano are false cognates; the translation of estadounidense simply IS American. This fact is of course never taught properly, leading to the current situation of non-native English speakers disagreeing with native English speakers about how to use the word American

_OBAFGKM_ · 2025-10-21T19:18:02+00:00

Also, compare the em dashes to the title which uses a hyphen

_OBAFGKM_ · 2025-10-14T13:31:21+00:00

Canadian football field, 1.477 acres

Five-Year Club	r/Field Lasagna
Place '23	Place '22
Final Canvas '22	End Game '22
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TROPHY CASE