knzhou

20 ms·

151.
by knzhou 6y ago
> what specifically leads to such bold conclusions (e.g. "owe an apology", "wasted time and effort", "statistical error", "screwed up", etc.)? They used a test with a false positive rate of about 2
152.
by knzhou 6y ago
To evaluate stuff like this, you just need basic physics knowledge (enough to do dimensional analysis with) and estimation skills. One fun read along these lines is "The Art of Insight in Science and Engineering". For stuff like t
153.
by knzhou 6y ago
I answered this here: https://physics.stackexchange.com/questions/287101/where-doe... The basic answer is that the extra energy that goes to the rocket comes from harvesting the kinetic energy that the fuel itsel
154.
by knzhou 6y ago
"Tidal effects" are defined in terms of having different gravitational fields in one place than another (i.e. the tidal bulge near to the moon occurs because the moon's field is stronger there).
155.
by knzhou 6y ago
You mean dark matter annihilation? There are some hints: an excess of gamma rays detected by Fermi-LAT, an excess of X-rays detected by Chandra, excess ionization detected by EDGES, and excess positrons detected by AMS-02. However, all of t
156.
by knzhou 6y ago
This entertaining article lists what happened to the early LSD researchers: https://slatestarcodex.com/2016/04/28/why-were-early-psyched...
157.
by knzhou 6y ago
> If light is emitted at a constant wavelength independent of the stretching of the universe, doesn't that imply light is traveling through a higher spatial dimension, otherwise the emitter itself would be stretched with the univers
158.
by knzhou 6y ago
I guess, but it depends on how one parses the poster's setup. You're correct that for particles interacting under a 1/r^2 force, the energy turns out finite in quantum mechanics. My comment was referring to the fact that once
159.
by knzhou 6y ago
I'd say that's a perfectly fine explanation. And in fact the light does get stretched. For sufficiently low frequencies, that's fine because there's enough time for new (unstretched) light to enter and exit the appar
160.
by knzhou 6y ago
This is definitely related, though not the whole story. Quantization did get rid of some infinities, but as GP kind of states, it also introduced others. My comment focuses on what we do for those.
161.
by knzhou 6y ago
The issue with these animations is that they're getting rid of all the thermal noise. In reality, single proteins are flying around the whole length of the cell many times a second, just from their thermal motion. And when processes li
162.
by knzhou 6y ago
The official way this is handled is called renormalization. Basically, we just declare that we have no idea what is going on at such short distances, and put in some regulator by hand to get rid of the infinity. One very crude regulator (wh
163.
by knzhou 6y ago
> If space is expanding why aren’t the radii of fundamental particles and their orbits and molecules also expanding? And if that we’re the case we couldn’t notice space expanding. > Does space only expand somewhere else? Only between
164.
by knzhou 6y ago
Well, if you're uncomfortable with LIGO, you're in good company. Once a whole decade went by in physics where people couldn't agree if it would work in principle or not. And it is true that a lot of common explanations are ba
165.
by knzhou 6y ago
> If your explanation is that gravitational waves stretch and squash spacetime so light takes different amount of time to bounce from an emitter back to a measurer, then you don't have even a slight understanding of how it works. We
166.
by knzhou 6y ago
You're right that this is glossed over in popular explanations, but the point you make is exactly the starting point for all formal courses and textbooks. The first part of the argument is that for single point particles falling, the
167.
by knzhou 6y ago
> To be clear, you're saying fields are essentially virtual mathematical notions from which emerges actual stuff? Perhaps, but I think that's a bit unfair. There's no dividing line between "mathematical notions"
168.
by knzhou 6y ago
I went to a school with similar dynamics, and if it's any comfort, I can assure you that the bullshit doesn't pay off. Those of us that pursued our interests deeply had our pick of college, those obsessed with simple metrics like
169.
by knzhou 6y ago
While I'm with you on the Greek, bra/ket notation is one of the best anywhere in physics. Here [0] are some examples of why it generally looks simpler, and here's [1] a derivation which would be a nightmare to write without i
170.
by knzhou 6y ago
"Field" is the abstraction we use in physics to say "there is a value associated with each point, and we're just not going to say whether it's representing the displacement of some invisible jelly, or the rotation
171.
by knzhou 6y ago
In theoretical physics, "why X" stands for absolutely nothing more than "please derive X from some other principle". Some people will use Y to derive X. Others will say that's not a real explanation, you really sh
172.
by knzhou 6y ago
They don't. All of the "evidence" here is cherry-picked clips where Biden stumbles for 2 seconds within an hour-long speech. Even now, Biden's a far better speaker than all the people snidely passing these clips around.
173.
by knzhou 6y ago
This is one of those completely false things that people only believe is true by repetition. Go back and actually read the full set of WHO statements in mid-January. They have a bunch of statements saying that nations should get prepared, o
174.
by knzhou 6y ago
The central kind of thing that this ban is meant to prevent is people posting on Youtube to drink bleach as a COVID cure and laughing over the ensuing deaths. We've disapproved of that kind of speech for centuries -- this slope isn&#x2
175.
by knzhou 6y ago
There are constant new outbreaks, at the rate of several per year. (If you want to try to keep up, see here: https://promedmail.org/ ) The vast majority fizzle out, and for the rest, travel restrictions are not often usef
176.
by knzhou 6y ago
There are legitimate arguments that travel restrictions are counterproductive, so you should argue against those, not against some perceived double standard that doesn't actually exist.
177.
by knzhou 6y ago
No, that's wrong. WHO essentially never encourages travel restrictions, their whole philosophy is that open international collaboration is crucial (that's why the W stands for "world"!). At the height of the Ebola epid
178.
by knzhou 6y ago
It doesn't work that way. It's trivial to build a rigged tree of evidence that makes any claim look good. Remember gish gallops from 90s internet arguments?
179.
by knzhou 6y ago
There's an endless flood of these bad comments. I'm just going through them (a new one posted every 2 minutes) and making the same rebuttal. People are stupid -- especially people who think they're smart contrarians.
180.
by knzhou 6y ago
The ban is meant for 4chan-based messages like "drink bleach/rubbing alcohol/methanol to cure yourself now!", which have killed plenty of people.

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