Today I Learned

[BillTre]

There are pizeo electric crystals in the bone.
It is though but not proven I guess that there is a control sequence that goes:
bone deformation from mechanical stress --> piezoelectric currents --> deposition of more bone material
In this way, more bone grows where it is needed most, where the mechanical stresses are greatest.

 

[DaveC426913]

TIL: why I pop and sizzle and feel shocks whenever I try to get up from bed. Or a chair.

 

[Hornbein]

TIL that the Chinese have had a space station for the past two years.

 

[pinball1970]

TIL that I am unsuitable for an asthma trial. Quite disappointed.

 

[DaveC426913]

TIL that I am unsuitable for an asthma trial. Quite disappointed.

Asthma sucks. Would not recommend.

 

[pinball1970]

Asthma sucks. Would not recommend.

Thanks Dave.

 

[Borg]

TIL (yesterday actually) that I had been doxxed and had false information posted about me online. The information was detailed enough that my HOA president knew that it was me even though the exact address wasn't posted. I had to create an account on the site just to report the post and ask it to be taken down. It took a day in which some pretty disturbing posts were made but they finally deleted it. I've since asked them to ban the user as well. Pretty scary incident.

 

[fresh_42]

TIL (yesterday actually) that I had been doxxed and had false information posted about me online. The information was detailed enough that my HOA president knew that it was me even though the exact address wasn't posted. I had to create an account on the site just to report the post and ask it to be taken down. It took a day in which some pretty disturbing posts were made but they finally deleted it. I've since asked them to ban the user as well. Pretty scary incident.

I found out that "your location" on my phone has a 360° picture right in front of the house I live in. This is a street where basically nothing happens at all. That was scary.

 

[topsquark]

I finally learned some basic Measure Theory and Lebesgue integration. I'm 52 and have an MS in QFT. Why didn't I learn this in my classes? It's easy, and it's awesome! I'll never look at integration the same way.

-Dan

 

[Borg]

I found out that "your location" on my phone has a 360° picture right in front of the house I live in. This is a street where basically nothing happens at all. That was scary.

Does it create online posts saying here's a bad person and here's where he lives?

 

[Ibix]

Does it create online posts saying here's a bad person and here's where he lives?

Wow, that's nasty. Any chance of finding out who posted it and asking the police to discuss the meaning of the word "incitement" with them?

 

[berkeman]

I found out that "your location" on my phone has a 360° picture right in front of the house I live in. This is a street where basically nothing happens at all. That was scary.

Nothing to be scared about. That's just the usual Google Maps Street View for your street. My house happens to be on a cul-de-sac off of a street, and the Google Maps car apparently didn't bother with our cul-de-sac so the closest I can get with Street View is a road behind my house. But most houses will have a Street View if you search for them by address or if you check your own location in Google Maps when you are home.

 

[Borg]

Wow, that's nasty. Any chance of finding out who posted it and asking the police to discuss the meaning of the word "incitement" with them?

Possibly. I don't want to get into too many details but I have contacted the police and filed a report. Since the post has been deleted, I'm hoping that it's the end of it but wanted the report created just in case. I also have screenshots of the thread before it was finally deleted by the forum. I'm keeping an eye on the forum for a while to make sure that it doesn't happen again. I also have the person who originally told me about it watching too.

 

[Algr]

I think all plants are perennial, and it is only climate that kills nonnatives each season.

I always wondered about this. How would an annual plant survive in nature?

 

[DaveC426913]

I found out that "your location" on my phone has a 360° picture right in front of the house I live in. This is a street where basically nothing happens at all. That was scary.

I'm not sure if you're kidding. Google Maps will show you a 360° view of practically any street in the developed world. And your location is where you are.

 

[BillTre]

I always wondered about this. How would an annual plant survive in nature?

It would produce seeds that survive inertly until the seeds germinate for the next growing season.
Many plants do this.
That is why seeds are popular with people who grow plants.

 

[fresh_42]

I'm not sure if you're kidding. Google Maps will show you a 360° view of practically any street in the developed world. And your location is where you are.

I forgot about Street View. I only thought of Earth. Anyway, I was surprised that it was directly in front of the house, not, say the near crossing. And I was surprised that the phone connected to Street View and not just Maps.

 

[jack action]

I always wondered about this. How would an annual plant survive in nature?

By spreading their seeds:

​

 

[Algr]

It would produce seeds that survive inertly until the seeds germinate for the next growing season.
Many plants do this.

By spreading their seeds:

But that doesn't seem to work for people who buy plants from shops. Everyone has to keep buying new plants every year. Maybe the process of seeding is really hard? Maybe it is a botanical conspiracy?

 

[jack action]

But that doesn't seem to work for people who buy plants from shops. Everyone has to keep buying new plants every year. Maybe the process of seeding is really hard? Maybe it is a botanical conspiracy?

Sure it's possible. I personally do it with Zinnias:

​

And with Marigold:

​

With these flowers, one flower can be transformed into dozens the next year. And there are so easy to grow, you cannot miss your shot. I highly recommend them for beginners. Bees and butterflies love them (especially Zinnias). My mother used to plant Marigolds in her garden to repel devasting insects (I don't remember which one).

 

[BillTre]

Paper airplane record from Boeing engineers.

Paper plane physics​

The team had decided their best chance at beating the world record would be with an airplane design that focused on speed and minimized drag, so that the plane could fly a far distance in a short amount of time.
Gathering inspiration from various hypersonic aircrafts, vehicles that can fly faster than five times the speed of sound (Mach 5), specifically the NASA X-43A, the team had come up with the winning paper aircraft design — later named “Mach 5.”
“Full-scale and paper airplanes have vast differences in their complexity, but both operate on the same fundamental principles,” said Ruble, via email. “Some of the same design methodologies can be applied to both. One of these methods was our trial-and-error design process. For instance, we would theorize about a fold we could change on our plane, fold it, throw it, and compare the distance to previous iterations to determine if the change was beneficial.”
To find the best technique when it came to throwing the paper airplane, the team ran various simulations and analyzed slow-motion videos of their previous throws.
“We found the optimal angle is about 40 degrees off the ground. Once you’re aiming that high, you throw as hard as possible. That gives us our best distance,” Jensen said in the statement. “It took simulations to figure that out. I didn’t think we could get useful data from a simulation on a paper airplane. Turns out, we could.”
Even down to the paper, which the team had decided that A4 (slightly longer than typical letter sized paper) was the best for manipulating and folding into the winning airplane. With these meticulously thought-out design choices, and careful attention to the numerous rules and guidelines set forth by the Guinness World Record Team, the three were set to break a record.
On its record-breaking distance flight the plane was in the air for roughly six seconds. The Guinness paper plane record for duration of flight is currently 29.2 seconds.
“The design objectives for an air-time record would be vastly different from the low-drag version we built for the longest-distance record,” Ruble said via email. “Increasing the wingspan and decreasing the aspect ratio would be the first steps in producing this type of plane.”
Paper airplane aside, Ruble added that this tedious method of back-and-forth trials served as a testament to the importance of rigorous prototyping in the real world.

 

[berkeman]

Yeah, I saw that article, but they didn't show a picture of the actual paper airplane. Did you see any pics of the plane?

 

[BillTre]

Yeah, I saw that article, but they didn't show a picture of the actual paper airplane. Did you see any pics of the plane?

Nope.

 

[pinball1970]

This is the previous record.

 

[Tom.G]

Here is an article link that includes a video. They seemed very careful not to reveal any shape details. One piece of additional info in the article is they used the heaviest weight paper they could get, for high inertia after launch.

https://onfirstup.com/boeing/BNN/ar...s-world-records-status-1?bypass_deeplink=true

Cheers,
Tom

 

[pinball1970]

Here is an article link that includes a video. They seemed very careful not to reveal any shape details. One piece of additional info in the article is they used the heaviest weight paper they could get, for high inertia after launch.

https://onfirstup.com/boeing/BNN/ar...s-world-records-status-1?bypass_deeplink=true

Cheers,
Tom

From what I saw of the other plane they seem to favour stubby wings, F22 Raptor shape. You can hardly see the plane in the record breaking flight. Trade secret!

 

[pinball1970]

TIL,more black hole news. That is the third big story in a matter of weeks. This latest is worth a thread I think because there is an AI part to it.
A more refined image of the EHT black hole.
Previous to this an intergalactic black hole detected and a black hole the size of a galaxy.
Perhaps stick on one thread?
The astro/cosmo guys will have seen this? @Ibix @Drakkith and Phinds maybe?

 

[Drakkith]

The astro/cosmo guys will have seen this? @Ibix @Drakkith and Phinds maybe?

I cant say I've seen it.

 

[pinball1970]

I cant say I've seen it.

Ok I'll stick a thread in Astro.

 

[Borg]

Yeah, I saw that article, but they didn't show a picture of the actual paper airplane. Did you see any pics of the plane?

Several searches returned this image but it could be sites aggregating the same image. The videos that I looked at talked about achieving maximum momentum and the heavy nose in the picture tends to corroborate that.

https://indianexpress.com/article/t...ane-world-record-for-farthest-flight-8462704/

 

[OmCheeto]

TIL that Graneledone boreopacifica, an octopus, has the longest egg-brooding in the animal kingdom at 53 months.
It is also the longest living octopus.
The female that broods the eggs does not eat the entire time, nearly 4 1/2 years!

I also learned that the incubation time for octopus eggs is temperature dependent, with colder temperatures yielding longer brood times: ref

examples:
3°C = 1600 days, the aforementioned
7°C = 420 days
22°C = 60 days
28°C = 19 days

 

[haushofer]

TIL that if you place two small marbles of 1 kg in interstellar space at 1 meter apart, they will collide after roughly one day due to their gravitational interaction. And that this collision time is another striking example of how a derivation based on units and some thought (2 body problem) can save you from doing a nasty integral.

A resemblance of gravity's weakness, I suppose. You only need to put 10^-10 Coulomb of charge on each marble to get the same collision time due to the electric force (shielding off gravity).

 

[Swamp Thing]

TIL that if you place two small marbles of 1 kg in interstellar space at 1 meter apart, they will colllide after roughly one day...

Just off the top of my head, not actually calculating anything, I would have guessed a time scale of years.

 

[haushofer]

Just off the top of my head, not actually calculating anything, I would have guessed a time scale of years.

I had a similar intuition. I guess a PhD in classical/quantum gravity doesn't guarantee a solid intuition about the subject :P

 

[jtbell]

Today I learned about the city of Peculiar, Missouri: Where the 'odds' are with you.

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