CanadaPlus

joined 1 year ago
MODERATOR OF
[–] CanadaPlus@lemmy.sdf.org 4 points 17 hours ago* (last edited 17 hours ago)

They still get very hot, though.

Another example: Every incandescent lighbulb. The filament is stupid hot in there, under a rough vacuum, and doesn't melt. I would be surprised if 1 bar even amounted to a full degree of change in melting/freezing point.

Water is volatile, and so it's a better example of variability at familiar scales. You'll notice the freezing point is pretty much vertical at 0C on the phase chart until 100s of bars. (And then gets lower because pressure pushes matter towards denser states, and ice I is, unusually, less dense than the liquid)

The triple point shows up when the boiling point lowers to meet the melting point, and liquid water ceases to exist as a stable substance. It's at ~0C.

[–] CanadaPlus@lemmy.sdf.org 9 points 18 hours ago* (last edited 17 hours ago) (2 children)

Melting point doesn't work like boiling point. Otherwise, what would we make rockets out of? They get really hot in a vacuum, but need to (and do) stay solid.

If you go to really high pressures like in an ocean trench or deeper, melting points will raise too (or lower, in water or silicon's case), but 1 vs. 0 atmospheres is negligible. I haven't seen it even mentioned in any vacuum engineering stuff.

[–] CanadaPlus@lemmy.sdf.org 6 points 18 hours ago* (last edited 17 hours ago)

Ditto goes for most alloys. Glass-like properties aren't typical, otherwise metal blowing would be a thing.

There might be alloys that can do this, but not the usual ones. Some of the low-melting ones can be gooey-seeming, off the top of my head.

[–] CanadaPlus@lemmy.sdf.org 10 points 18 hours ago* (last edited 18 hours ago)

Things still do cool in shaded space, though, it just takes longer. The James Webb took like a month or two to get down to cryogenic IIRC.

I have a feeling OP was worried about gravity, which isn't usually helpful here, but isn't actually a dealbreaker. Glass is heavy too.

[–] CanadaPlus@lemmy.sdf.org 1 points 18 hours ago* (last edited 18 hours ago)

That's pretty much how the Russian economy works right now, in a nut shell. To stop emigration caused by the expensive war, they're giving away a ton of expensive handouts.

The interest rate is at 19% and counting. Very cool, very sustainable. I have a feeling "the last laugh" will be yours, OP, even if they win in Ukraine.

[–] CanadaPlus@lemmy.sdf.org 3 points 1 day ago (1 children)

How sure are we that it's not?

[–] CanadaPlus@lemmy.sdf.org 2 points 1 day ago* (last edited 1 day ago)

Disclaimer that I'm still a noob, too.

I gave my main recommendation there, for transceiver. I haven't done the research to have a model or brand in mind, but a cheap SSB (single side-band) radio seems like it should exist, given that you can make such a device with just 7 transistors. Any remotely modern computer will be able to generate an audio signal that, when mixed up to RF the way a SSB radio does, will look like the mode of your choice. Software-wise, I've really liked working with GnuRadio so far.

Amps go for a lot more new, because they have to handle both radio frequencies and >100W powers, and do so without causing distortion. Ham radio is a dying art, so poking around for ones at estate sales or similar seems promising. 100W is generally the recommended minimum if you don't want to be frustrated.

For the feedline, assuming you're doing coax, the design tension is between bendability and DB/meter attenuation. For radio 50 ohm impedance is standard, not 75, so you can't reuse stuff from cable TV without transformers. (Impedance matching is very important, as you'll learn getting a licence)

For the various accessories you may need to connect cables, amps, antenna wires and maybe filters, Amazon. They even have the obscure stuff I've needed for my direct sample radio.

All the prefab antennas I've seen seem ludicrously expensive, given that it's a chunk of ordinary metal, so probably skip that and cut your own. Antenna recipes are all over the place on ham homepages. If you're doing a bunch of non-resonant antennas, a tuner will save you time, but they cost as much as an amp. Everything that works at the high-power end is expensive.

[–] CanadaPlus@lemmy.sdf.org 2 points 1 day ago (1 children)

No, I wasn't quoting anything there. People are used to choosing who they want to communicate with, sending a message, and everything either working or (rarely) not working. Power, noise, space weather, multipathing, interference and the vagaries of antenna performance all make it a bit more involved when manually operating a radio. And that's not even getting into whatever you need to make your own setup work.

[–] CanadaPlus@lemmy.sdf.org 29 points 2 days ago* (last edited 2 days ago) (4 children)

Yeah, ham radio. If I was doing it all over again, I'd go for the most basic SSB radio I can find that plugs in to a computer sound card - that should in theory be able to do anything reasonable. You'll also need feed lines, an amp and a large-ish antenna, which is where things get a bit more technical hardware-wise, especially if you're in an apartment or have something like an HOA, but it nothing you can't figure out.

And yes, a licence. So far I've found the requirements pretty reasonable in my jurisdiction, they relate to not frying yourself or your equipment, and how not to be a menace to other people sharing the radio bands. You used to need to learn Morse code fluently enough to pass a practical test, but most places have gotten rid of that.

[–] CanadaPlus@lemmy.sdf.org 7 points 2 days ago* (last edited 2 days ago) (3 children)

It's mostly stuff you definitely need to know, though, at least in Canada. There's a bit more to it than sending a text.

[–] CanadaPlus@lemmy.sdf.org 3 points 2 days ago

Oops, my bad. I guess I'll go lie down in front of the horses with the others.

[–] CanadaPlus@lemmy.sdf.org 5 points 2 days ago (2 children)

Nah. Make Mongolia European again.

 

cross-posted from: https://lemmy.sdf.org/post/21879517

A link to the preprint. I'll do the actual math on how many transitions/second it works out to later and edit.

I've had an eye on this for like a decade, so I'm hyped.

Edit:

So, because of the structure of the crystal the atoms are in, it actually has 5 resonances. These were expected, although a couple other weak ones showed up as well. They give a what I understand to be a projected undisturbed value of 2,020,407,384,335.(2) KHz.

Then a possible redefinition of the second could be "The time taken for 2,020,407,384,335,200 peaks of the radiation produced by the first nuclear isomerism of an unperturbed ^229^Th nucleus to pass a fixed point in space."

 

A link to the preprint. I'll do the actual math on how many transitions/second it works out to later and edit.

I've had an eye on this for like a decade, so I'm hyped.

Edit:

So, because of the structure of the crystal the atoms are in, it actually has 5 resonances. These were expected, although a couple other weak ones showed up as well. They give a what I understand to be a projected undisturbed value of 2,020,407,384,335.(2) KHz.

Then a possible redefinition of the second could be "The time taken for 2,020,407,384,335,200 peaks of the radiation produced by the first nuclear isomerism of an unperturbed ^229^Th nucleus to pass a fixed point in space."

 

Per the rules, this is the original headline. However, the interesting part is that he's preparing a Gaza offer that he says will be "final".

They've hewn very close to the whole "unconditional support" thing, so I'm curious what that means exactly.

 

Just watched this and thought it was dope. I especially liked the Roman buffets and Foreman grills.

 

I've been playing with an idea that would involve running a machine over a delay-tolerant mesh network. The thing is, each packet is precious and needs to be pretty much self contained in that situation, while modern systems assume SSH-like continuous interaction with the user.

Has anyone heard of anything pre-existing that would work here? I figured if anyone would know about situations where each character is expensive, it would be you folks.

 

This is about exactly how I remember it, although the lanthanides and actinides got shortchanged.

 

Unfortunately not the best headline. No, quantum supremacy has not been proven, exactly. What this is is another kind of candidate problem, but one that's universal, in the sense that a classical algorithm for it could be used to solve all other BQP problems (so BQP=P). That would include Shor's algorithm, and would make Q-day figuratively yesterday, so let's hope this is an actual example.

Weirdly enough, they kind of skip that detail in the body of the article. Maybe they're planning to do one of their deep dives on it. Still, this is big news.

 

Reposting because it looks like federation failed.

I was just reading about it, it sounds like a pretty cool OS and package manager. Has anyone actually used it?

view more: next ›