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Best anki testimonial that I've read.

respectfully disagree. i think that the value of llm suggestions are driving us toward a kind of standardization that is really good. we'll all be java programmers soon!

ok, but i'd wager brain cancer (the cause of death in this case) lacks this correlation. And yes RIP, Mutombo seemed like an exceptional person.

All other factors being equal: Taller person = more cells = more cell divisions = more chances for cell mutation = increased risk of (any) cancer. (credit/source: Hank Green and possibly SciShow on YouTube)

I love being wrong! Luckily I wagered $0.00.

Taller people usually have bigger heads and, I think, bigger brains.

This doesn't mean they are more intelligent.


actually there is a correlation between height and cancer

The goal is to make a prediction about the boundaries or interiors of black holes that can be tested. It’s based on the common sense belief that information is conserved even if it reaches the center of a black hole.

If I understand correctly, the idea that information is preserved is based on QM using unitary matrices. That's hardly a "common sense" belief.

The belief that that applies even at the center of a black hole is an additional non-common-sense step.


The black hole information paradox presents an apparent theoretical contradiction between black hole radiation, which Hawking predicted carries no information about its past, and quantum theory, which conserves information at all times. The common sense belief would be that information is conserved, perhaps because there is something measurable inside a black hole and not a singularity.

Maybe I should have said that the ideas in the article are an approach to resolving the paradox, rather than invoking common sense.


> The common sense belief would be that information is conserved

I'll say it once more, since you didn't seem to understand my point the first time: "information is conserved" is not a "commonsense belief". (Unless you mean "commonsense within the quantum mechanics community".)

Commonsense is "I've seen a shredder. I know information can be destroyed."


Ok, well, would you expect a shredded book to be indistinguishable from a shredded bowl of jello, or a shredded pot of coffee, or a shredded parcel of ionized plasma?

But a shredder doesn't actually destroy information.

Back to the original discussion, though: Time and again I'm fascinated by the fact that it's the quantum mechanics community that believes in unitarity / information being preserved so strongly. After all, the collapse of the wave function violates unitarity, too.


> But a shredder doesn't actually destroy information.

See, people keep talking about the "common sense" idea. Well, in the common sense view, yes, a shredder actually does destroy information, because you can't read the page any longer. The "common sense" people don't have any notion of information in the quantum sense, or unitarity, or waveform collapse, or any of that stuff.

"Common sense" does not mean "common sense among postgrads in quantum mechanics". Those are two completely different things.

The "common sense" level is probably something like, black holes exist, and maybe some notion that something called "quantum mechanics" exists. Most people don't have any kind of "common sense" about the details.


Oh I didn't mean to say a shredder not destroying information was common sense. Maybe I just didn't like this particular example too much because I think even for non-physicists it's still imaginable someone could – in theory – piece together the shredded paper again.

Anyway, I agree with your overall point.


In 1676 Roemer estimated the speed of light by timing the orbit of Jupiter’s moon Io, noting that as the Earth approached Jupiter, Io emerged from behind Jupiter a little earlier every day, and as the Earth traveled away from Jupiter it appeared a little later every day, with the time of day varying by 22 minutes over a year. Knowing the difference between the two distances, he reckoned that light travels that distance in 22 minutes, or 227 thousand km/s. The actual speed is about 300 thousand km/s. Not bad!

I always appreciate these stories about how very specific observations that most people would miss can give away far deeper details of the universe that many wouldn't even consider. Eratosthenes using shadows and figuring out the size of the earth within a few percent is another well known one.

https://en.wikipedia.org/wiki/R%C3%B8mer%27s_determination_o...

https://en.wikipedia.org/wiki/Speed_of_light#First_measureme...

Another interesting thing about using the timing of moon eclipses:

> Galileo proposed a method of establishing the time of day, and thus longitude, based on the times of the eclipses of the moons of Jupiter, in essence using the Jovian system as a cosmic clock. The times of the eclipses of the moons could be precisely calculated in advance and compared with local observations on land or on ship to determine the local time and hence longitude.

https://en.wikipedia.org/wiki/Galilean_moons#Determination_o...


It's amazing to think that with nothing more than a telescope and careful timing, he managed to get so close to the actual speed of light.

Well, also knowledge of the distances between the objects involved (at least the Earth and Jupiter), which in turn depended on a series of further investigations.

Which is not to denigrate the achievement, but if I were to drop you on an alien world with only a telescope and an accurate time keeper, you're not going to be able to recreate it.


> if I were to drop you on an alien world with only a telescope and an accurate time keeper, you're not going to be able to recreate it.

But you can relatively easily derive the distances too with timekeeper and telescope, by applying Keplers laws?


One can, in principle. Most people lack the talent. (It's a skill that almost anyone could learn, but that doesn't make it a skill everyone has.)

That’s not the definition of talent

From what I've seen, talent is the tendency for a person to naturally develop a skill, if left alone to do so. It isn't some kind of intrinsic capability.

Talent isn't just about innate ability but also about how a person’s environment, interests, and experiences allow them to engage with a skill

The speed of light, because it is so fast, is the most precise physical constant known : 299 792 458 m / s. Less than 7/1000ths away from 300,000,000 m / s. I am not going to sweat this in the least.

So light travels only 0.3 m / nano second, or 11.802 inches.

https://www.youtube.com/watch?v=9eyFDBPk4Yw


Therefore in one cycle of a 3GHz processor, light travels about 4 inches. Wild.

My favorite riff on this: at a previous job we worked on a 12GHz SERDES, which meant each inch of the cable had a different data bit on it

Which is maybe part of the reason RAM needs to be so close to the CPU? Granted though most RAM access takes several CPU cycles.

This is exactly it, the longer your traces (or any sort of write I guess) between processor and memory, the longer delay you have to have for things to "settle". Additionally increasing capacitance means that it takes more effort (read, even longer) for the line to settle.

Does make me realise I don't know so much about the super low level parts of it beyond electrons and holes. One end of the wire needs to be at a lower potential to encourage electrons to flow from that side to the other. Hmmm.


Armed with this fact thinking about electronic devices. How the front of the signal travels and how suddenly the distance matters. Was blown away when I first thought about this.

Speed of light has recently been redefined, and is now _exactly_ 299792458 m/s. It’s no longer a measurement, it’s a definition.

That's a little misleading: either the meter or the second has been redefined to make c = 299792458 m/s.

Since 1983, the meter is defined in terms of the distance traveled by light in a vacuum during 1 second, see https://en.wikipedia.org/wiki/Metre#Speed_of_light_definitio...

The second is (and has been) defined independent of length for a while. It's the time it takes for a certain number oscillations of a caesium atom.

The meter was redefined as the distance light travels in a specific time. So you could say that either the meter or the speed of light was redefined to make the speed of light a round constant, but not the second.


To me, the result is exciting because it shows how algebra, over hundreds of years, came back round to improve Euclidian geometry. Without the background, I wouldn't even know why it was an interesting problem. The motivation is very similar to that of the Langlands program.


There are two authors here, since the post contains an inset about dealing with your own ignorance by another professor. They aren't saying quite the same thing. The inset is saying that every grad student will confront their "absolute ignorance" and it will be difficult, scary and possibly painful. The author of the post is saying it can be a source of joy. I suppose they can be reconciled. It could also be that so little of our behavior is based on knowledge that the only sane reaction is at least somewhat negative, whether characterized by being overwhelmed, or sad, or detached.


yes, just heard about it on Physics Frontiers. Monsalve & Kaiser are talking about primordial black holes, and are offering a theory that if they were imbalanced in color charge, they could be surrounded by a particle cloud, in a big quantum state.

https://pca.st/episode/f0db6ab1-18ff-4201-a6b2-a30b780a266a


very true.


well, without people working downtown, it will be abandoned to drug addicts in a spiral of insufficient public safety resources and declining revenue. so i don’t blame him.


At least then you might get a mayor that works for the people living downtown than whatever suburbanites swarm it on work days.


This comment cracked me up. I do live in downtown Seattle.


Or maybe all of the ridiculous pressure from sky high salaries and no affordable housing led to the homeless population...


There's lots of "affordable housing" aka Byzantine subsidy schemes here in Seattle. What there isn't is consistent enforcement against encampments, littering, and shoplifting


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