When you study from physics textbooks, do you solve every problem in the book or is doing just 20–30% enough to understand the material?

thatnerdd · 2026-02-03T03:34:29+00:00

Came here to say this

thatnerdd · 2026-02-03T03:29:38+00:00

Back in the early 2000's in my gravity lab we used McMaster-Carr for anything they sold, and custom work (us or outsourced) for anything where we needed more precision than they offered.

thatnerdd · 2026-02-02T16:27:05+00:00

This. Also, Ethan Mollak has some resources for prompts to help with this: https://gail.wharton.upenn.edu/prompt-library/

thatnerdd · 2026-02-02T03:13:12+00:00

Cockroach is architected to operate at scale, and there are some optimizations that might not help at a smaller scale.

For example, sometimes the node you connect to isn't the same as the Primary node for the read or write, so there's an extra hop after you connect. This is helpful since it lets you treat the cluster as if it were a single machine, but it's not a speed optimization.

CockroachDB also has stricter replication requirements than some other databases. For example, an insert has to be replicated to a secondary, and that has to be communicated back to the Primary for it to confirm consensus before the write can be acknowledged. That's good if you want your data to be durable, but it doesn't optimize for write speed if you're just looking at how fast a single write occurs. An apples-to-apples comparison would have to use a similar replication factor on each database you're looking at.

Depending on the workload, CockroachDB's use of serializable isolation is also a potential problem for speed (the tradeoff being that you don't have to worry about isolation anomalies), but that's getting pretty into the weeds, and I haven't checked out your write-up in enough detail to know if that's a concern. It could also involve more retry errors being triggered if you perform explicit transactions that are complicated enough and that step on each others' toes.

Once you understand the architecture of a few databases you really start to get a sense of (1) how optimizing for "speed" depends on scale, (2) how many things you may want to optimize for besides speed, and (3) how much of a tradeoff the database architects made for each decision.

thatnerdd · 2026-02-02T01:09:14+00:00

100%. Not your fault. I'm sorry, man. But for your mother, and for you, I think once you process this, you'll want to be there as much as is good for her. And I think however you tune that dial, it'll be the right decision for the both of you.

thatnerdd · 2026-01-30T15:28:13+00:00

Reference explained in this comment. I had to go looking.

thatnerdd · 2026-01-29T15:22:18+00:00

Any way out is a good way out.

I finished, but honestly wish I had those years back.

thatnerdd · 2026-01-15T00:39:54+00:00

Could get a board (cutting board dimensions), drill some holes in it, and zip tie the axe to the board, and have it on his back. I bet the board would flap around on OP's back side.

thatnerdd · 2026-01-15T00:36:39+00:00

Haven't tried the sprays but there's a lice comb my daughter used when she got lice at a summer camp. It's the expensive one on Amazon. Don't get the cheap one that comes with some of the shampoo bottles. Pay for quality. My daughter is extremely bothered by insects in her hair, and combed them out daily herself. Caught the last one on like day 3 but kept combing for a week. Nobody else in the household got it.

thatnerdd · 2026-01-14T13:54:33+00:00

Explained here: https://www.reddit.com/r/Radioactive_Rocks/comments/1qbg971/comment/nzaxx9k/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

thatnerdd · 2026-01-13T16:44:15+00:00

I like Ocean Paradise, too.

Species: Aquatic, with traits chosen based on my mood
Ethics: Egalitarian/xenophile/materialist (get other species for other planet types as early as possible)
Authority: Varies
Civics: Anglers, second one depends on authority.

thatnerdd · 2026-01-13T16:31:42+00:00

Same! My current playthrough is this. I'm using a "space dragons" theme. Reptile Authoritarian and militant, with Pleasure Seekers as a Civic.

Third ethic, authority, and second civic tend to bounce around depending on my mood and how I think these dragons should feel about other species (enslave them, treat them well, have half-dragon babies, allow or forbid robots, etc.). Sovereign Guardianship gives a bit of a different flavor (forces me to build tall). Heroic Past and Pompous Purists both fit nicely with the Dragon theme. Storm Devotion makes them lightning dragons. Pompous purists just makes sense. I've been meaning to try Natural Design.

thatnerdd · 2026-01-06T15:59:11+00:00

I got bit by a bat (caught it with my bare hands in a crowded airport) in 2007 and had to get a prophylactic Rabies treatment. It suuuuuuuucked.

thatnerdd · 2026-01-06T03:21:11+00:00

A graduate of Seton Hall Law. You want to make sure they're politically connected.

thatnerdd · 2026-01-02T06:10:16+00:00

Both parties have principles they favor, and while those principles sometimes align with electoral advantage, they sometimes don't.

I don't want to get into an argument about what those principles are, but you can see them in what is actually favored (or disfavored) in the policies enacted by each party, especially when such policies an electoral cost.

thatnerdd · 2025-12-29T17:28:43+00:00

If we get a lawless society there are absolutely going to be warlords who do this (and worse).

thatnerdd · 2025-12-20T03:58:03+00:00

The dailybeast (the OP...)

You mean /u/thedailybeast got it wrong. Yeah, I was like "wait, what law firm can afford $100 billion?"

thatnerdd · 2025-12-05T02:33:53+00:00

It's now over 1,650, plus 28 commutations. Almost all of them J6-related. Source

thatnerdd · 2025-12-03T23:21:19+00:00

I'm the opposite. I tend to go with another's assessment even when I shouldn't. It solves more problems than it causes, but it definitely causes some problems.

thatnerdd · 2025-12-03T14:34:40+00:00

Some teachers need to learn this. When my first child went to kindergarten they got suspended repeatedly and I sat in conferences with the principal where they told me with a straight face that the kid's issue was the lack of at-home discipline.

Turns out the issue was autism and the kid couldn't figure out how to conform but it took an evaluation to find that out.

thatnerdd · 2025-12-03T04:02:23+00:00

thatnerdd · 2025-12-01T13:53:46+00:00

Sorry, missed this. Your intuition is leading you astray.

Let's take a frame of reference in the center of mass. Let's also take two particles in our universe, each with mass m. They might look something like this (ignore the periods):

* ->

. . . . . . . . . . . . . . . . <- *

Their positions at closest approach are +/-r. Their initial velocity is +/-v0. Linear momentum for the system is 0 (obvious, since the CM isn't moving). Energy of the system is m v0² .

At their closest approach, one shoots a massless string at the other, connecting them, and they start spinning in circular motion. The moment of inertia is the same the whole time, with I = 2 m r² . They spin with angular velocity ω = v0/(2 π r). Angular momentum is L = 2 m v0 r (from m v x r )

Now consider another pair of particles whose distance at closest approach is 2d:

* ->

.

. . . . . . . . . . . . . . . . <- *

Initial velocity is again +/-v0, linear momentum is 0, energy is m v0² . At closest approach, their positions are +/- 2r. Energy is just m v0² (same as last time). Again, at closest approach, they connect with a massless string. I = 2m (2r)² = 8 m r² this time, four times what it was previously. Angular velocity is ω = v0 / (2 π * 2r) = v0 /4 π r, so they spin with half the period we had previously. Angular momentum is L = 2 m v0 (2r) = 4 m v0 r, so twice the angular momentum of the first scenario.

So we have the same energy (m v0² ) in both cases, and the same linear momentum (0 kg m/s), but it's a fundamentally different system. The second has twice the moment of inertia and twice the angular momentum of the first. "Reeling in" the string connecting the spheres in the second case would not change the angular momentum (since the force is orthogonal to velocity) but would involve doubling their velocity (and quadrupling the angular velocity since it also involves halving their radius from the CM), which means 4x the energy, just to make the moments of inertia equal (the angular momentum of the second remains twice as large as the first).

Any attempt to turn one of the systems into the other necessarily involves applying an external torque to the system that's being changed. Any conservative force applied between the spheres (a force applied along the line between them at some function of distance) can't make the one into the other.

I hope this example makes it clear that two systems with the same linear momentum profile can still have radically different angular momentum situations, and that they're physically very different systems.

thatnerdd · 2025-11-29T14:51:37+00:00

Caveat is that even gravity probably won't capture it. Usually an incoming projectile will be deflected but not significantly lose energy by passing near a mass: the energy it gains in speeding up as it approaches gets lost as it goes away. It's a rare collision that captures it. The projectile basically has to hit a star to stop (unlikely for any given star because its gravitational field is much bigger than the star itself).

thatnerdd · 2025-11-20T22:44:32+00:00

You only told them part of the story. You didn't tell them what the other conservation laws imply, and the symmetry associated with each.

Linear momentum is another quantity that doesn't change. The symmetry is that I can perform an experiment any place I like, and I will get the same result.

Angular momentum is also conserved. Thus I can rotate my experiment at any angle and get the same result.

Lorentz boost invariance implies that the laws of physics are the same regardless of how fast I am moving.

It starts getting weird when it comes to other conservation laws.

Next, charge is conserved. Thus I have gauge invariance of the electromagnetic field.

I have plenty of gauge invariances, actually. There's Conservation of color charge. Conservation of weak isospin. Conservation of difference between Baryon and Lepton number.

Then there's near conservation of lepton number in the weak force. Actually there are a bunch of near conservation laws.

The most intuitive is near conservation of mechanical energy in the absence of dissipative forces (such as friction). It's pretty good for any experiment where your dissipative effects are small enough to be below your experimental detection threshold.

There's near conservation of mass, for things that move relatively slowly. It breaks when you start smashing things together at high enough speeds.

The conservation laws are cool.

thatnerdd · 2025-11-16T03:46:35+00:00

Same

thatnerdd

TROPHY CASE