Magnets! How do they work?

[Piotrsko]

Take a CO2 cartridge and poke a hole in it, let the gas out really fast and they frost up. My theory is rusty but I think some dude named Pascal had things to say about pressure vessels. Now it might be that the CO2 stream isn't colder, but something is radiant to get the frost.

Otoh, perhaps you mean to say that compression could occur without a major heat rise. No practical expertise there, I have no reason to compress CO2

[freebeard]

"At ?t=313 it's claimed that a property of CO2 is..."

[redpoint5]

While brushing up on the tyranny of the rocket equitation, I was wandered into mass drivers, which led me down the Youtube rabbit hole, and this video is where I landed last night.

Rockets are 90% fuel, 8% rocket, and 2% payload.
Boeing 737 is 25% fuel, 50% plane, 25% payload
Toyota Camry is 3% fuel, 66% car, 30% payload

Obviously building any sort of colony anywhere else, or mining other objects in our solar system is going to require getting materials into space more efficiently than a rocket can deliver.

https://www.youtube.com/watch?v=8B2iqiKehyM

While watching the video I was assuming the entire structure would have to be built in space, which would totally defeat the purpose of building such a structure. It would actually levitate from the ground as the internal mass was accelerated beyond orbital velocity.

Originally Posted by Piotrsko

Take a CO2 cartridge and poke a hole in it, let the gas out really fast and they frost up. My theory is rusty but I think some dude named Pascal had things to say about pressure vessels. Now it might be that the CO2 stream isn't colder, but something is radiant to get the frost.

Otoh, perhaps you mean to say that compression could occur without a major heat rise. No practical expertise there, I have no reason to compress CO2

Temperature is a measure of the concentration of heat energy, not the total quantity of energy. Sparklers emit sparks up to 3,000 F, but it's such a small amount of energy that you hand can hardly feel it.

Compressing a volume of gas concentrates the heat energy into a smaller space, raising the temperature. Once a temperature differential exists between the compressed gas and the surrounding environment, entropy tries to equalize equalize the temperature differential, and energy from the hot gas is lost to the environment until they reach equilibrium.

A compressed gas that is allowed to expand distributes the heat energy over a larger volume, absorbing heat around it and causing the vessel to become cold and frosty.

Losses can be minimized with insulation. I expect losses are minimized if the compressed gas is immediately released too, but then that defeats the point of compressing it in the first place.

The thing that fascinates me is endothermic chemical reactions. Usually chemical reactions produce heat (it's impossible to produce cold, because it isn't a thing), but endothermic reactions absorb heat to facilitate the reaction, and that's why cold packs work.

[freebeard]

Nobody wants to talk about an underground NASCAR running on methanol?

[freebeard]

Further to permalink #5, I've been looking at others of GenGaz - Lagunov's videos. Very thorough.

https://www.youtube.com/channel/UC7D...UBWHRog/videos

There is a three-part series about using electrostatic filters for the wood gas that don't clog up immediately.

Electric filters for wood-powered cars: designs overview. Part 1

I'll have to watch the second and third parts to confirm that's a Chevrolet in the thumbnail. This could enable my dream of living in a school bus that runs on firewood, and roaming BLM land by parking next to slash piles.

[freebeard]

On a side note, as CR would say,

justacarguy.blogspot.com... Rubber, airplane tires, and an obscure southwestern plant grown in the USA that doesn't require farmers till after each season

Tire manufacturer Bridgestone has operated a demonstration-scale processing facility in central Arizona for the past decade in an effort to show that guayule can eventually be harvested for natural rubber at a commercial scale.

The market is currently dominated by rubber sourced from Hevea brasiliensis trees in Southeast Asia....
But fungal infestations of monocultured Hevea trees have caused steep drops in global natural rubber supplies in recent years, and the Southwest’s drought has reduced the water available to farmers, making it harder to grow alfalfa, cotton and other crops.
....Bridgestone launched its guayule research initiative in 2012, when it broke ground on a guayule processing and research center in Mesa, Arizona. Today, the company says it operates the research center in Mesa, as well as a 281-acre guayule farm in Eloy, Arizona. Bridgestone says it has invested more than $100 million in its efforts to commercialize guayule.

Guayule is part of the Bridgestone plan to achieve carbon neutrality and make tires from 100% renewable materials by 2050, according to the company. It is actively researching a range of solutions to support the recycling of materials from end-of-life tires and promote the replacement of non-renewable materials such as oil, silica and virgin carbon black in new tires.

[freebeard]

Self-threadjack.

I worked in one career in close support to computer programmers. I grew to appreciate the depth of the rabbitholes programming takes you down. One example I found was the complexity of creating a field where people can enter their name. The set of possible names is large (character count, captialization, names that start with punctuation, etc.)

Via Hacker News, here's a discussion of Unix time: https://www.netmeister.org/blog/epoch.html

Time is an illusion, Unix time doubly so... October 23rd, 2022
As you well know, on Unix systems we measure time as the number of seconds since "the epoch": 00:00:00 UTC on January 1st, 1970. This has made a lot of people very angry and been widely regarded as a bad move.

For starters, this definition is not based on something sensical such as, say, the objective frequency of vibration of a Cesium-133 atom, but on a convenient fraction of the time it takes a particular large rock to complete a full rotation around its own axis.

You see, in Unix time each day is guaranteed to have exactly 86400 seconds, and we pretend that this number monotonically increases. When it turns out that because our reference rock actually took a bit longer than what was convenient for us to complete its rotation and we need to add a leap second, we simply pretend that didn't happen, and our timestamp mechanism ceases to identify a unique point in time.

The other thing that continues to cause problems here is that as we try to count seconds, we run into data storage and representation issues, because honestly, computers aren't really all that good at numbers, it turns out. Talk about "epoch fail".

Conclusion:

As I said, time is an illusion, and Unix time doubly so. And while the Year 2038 Problem may not concern you (unless you happen to use OmniOS, I suppose), perhaps I was able to show you that there are plenty of other surprises lurking. And we haven't even touched upon the insanity that is timezones and Daylight Saving Time...

I love the phrase "this number monotonically increases." When you count 60ths of a second base on line frequency you're at the mercy of the local utility company.

[redpoint5]

I recently learned Oregon is going to stop mucking around with time changes. Thought I'd never live to see the day.

Now I'm going to dream big and expect to live to see federal income tax either die, or shed all the exceptions that cause the need to "do taxes". The only thing I hate more than paying taxes is doing taxes.

...so Unix has a Y2k+38 bug. I expect this affects Linux, and if so does it affect Android?

Xist might have to upgrade his Samsung Galaxy 6 next decade if that's the case.

freebeard gets vindication that smartphones are for dumb people.

[freebeard]

Thanks for bringing this up in a thread I own. The most inspiring thing I've seen today, even more than Quietwarm radiant floor panels, is seeing Tulsi Gabbard and Ron Paul bonding over home schooling.

Tulsi Gabbard Live | Donald Trump News Live | Tulsi says 'Democrats Believe They Are Gods' | News18

This appears to be live, but it's an endless loop.

I was in the trenches for Y2K, and we knew that it was a wakeup call to 2038. It turns out with a signed integer, Unix threw away half the potential dates. Maybe the negative half is where the solution lies.

[Xist]

I bought a Samsung Galaxy S20 FE for black Friday 2020.

Tulsi Gabbard is insane.