What's the most surprising fact you've learned in the last couple of weeks?
-
@johncarlosbaez It's kind of 'obvious in hindsight', but I didn't know it until considering a hypothetical in a murder mystery.
Are twins the worst plot device in some stories, after time travel? (And I *like* some stories featuring twins or time travel
)@foldworks - special relativity manages to make good use of a story involving *both* twins and something akin to time travel. The Twin (Non)Paradox.
-
The last couple of weeks? Learning is what drives me, a week is quite a long time!
There are two things I learned from your posts: Donella Meadows' nine leverage points were quite engaging. Didn't talk about it much on-line, because there's so much to say! I found it to be a hopeful perspective, well worth any dread caused by talking about big problems. People I told about it mostly liked it!
The other is that I now have a picture of the 600-cell! I always felt, nah, that's too complicated, let's stick to the smaller ones. And then your explanation of @jasonhise's happened, and @henryseg showed off his models. That's so cool, now what do I do with it?
It's sort of on-topic for me, because I have been eyeing little facts about rendering hyperbolic spaces for a while. Since @Number_Cruncher reignited my interest in Coxeter-Dynkin diagrams, and all that comes with it. I think I owe them a shader for hyperbolic Coxeter groups. Sorry, been busy...
For one, I have now practical experience optimizing compressed data size by rewriting the uncompressed source. That's quite an odd thing to do, but I learned a ton about what my code actually needs to do. Oh and if you ever want to submit a shader you wrote to a demo competition, I might have something for you.
The other obsession that got lots of time was to write an ocaml module for conformal geometric algebra. That alone is a very beautiful subject! I want it to output math kernels for shaders. In the end I learned that typed-tagless-final is the name for the concise style to represent syntax trees I didn't dare to use, thanks @JacquesC2 for writing about it years ago!
You see, @johncarlosbaez, you're still important to me, and I miss our conversations!
@RefurioAnachro - Why don't we have so many conversations anymore? I figured you either got bored of what I'm talking about or got too busy with other things.
I'm glad you have a better picture of the 600-cell now. One thing *I* want to do now is better understand all the fancy stuff about the geometry of the 600-cell that's on Wikipedia. That article has grown a lot since I last saw it:
A lot is written in ways that I have trouble quickly understanding. But some gems stand out, e.g.:
"The 600-cell can also be partitioned into 20 cell-disjoint intertwining rings of 30 cells, each ten edges long, forming a discrete Hopf fibration which fills the entire 600-cell."
and others seem like they could be great if I understood them. As a hobby I may try to understand this stuff and fit together the mental pictures.
-
@johncarlosbaez
Our worm-like ancestors were cyclops. When they decided to start swimming, the central eye squeezed out two side eyes and was itself reduced to the pineal gland that to this day regulates our circadian cycle.
Our modern vision evolved from an ancient one-eyed worm creature
The now extinct worm-like animal first lost paired eyes, then re-evolved them.
The Conversation (theconversation.com)
@BartoszMilewski - wow, yikes! I didn't know that.
The eye, or should I say "a kind of eye", has evolved many times independently. You're making me want to understand not just the history of *our* eyes but *all* these eyes.
I'll have to read this:
β’ Bhattacharya, Stagg, Donlon and Hardy, Evolution and development of complex eyes: a celebration of diversity, https://pmc.ncbi.nlm.nih.gov/articles/PMC7578360/
-
@johncarlosbaez a historical bit, for a change: I was very shocked to learn that the few italian places that have "Romano" in their name, derive that not from "Roma" and "romano" as one might expect, but from quite the opposite: during the long war between the (Roman) Empire and the Langobards, those places took name from the upper class of the Langobards, i.e. the arimanni; "Romano", in the names of these places, comes from arimanni, not from "Roma" and "Romano".
@rioDa - surprising indeed! I bet even the modern residents of some of these places would be surprised.
-
@Heterokromia - wow, I didn't even know I had methanogenic archaea in my gut! I take statins. Is it bad to kill ones methanogenic archaea?
-
@BartoszMilewski - wow, yikes! I didn't know that.
The eye, or should I say "a kind of eye", has evolved many times independently. You're making me want to understand not just the history of *our* eyes but *all* these eyes.
I'll have to read this:
β’ Bhattacharya, Stagg, Donlon and Hardy, Evolution and development of complex eyes: a celebration of diversity, https://pmc.ncbi.nlm.nih.gov/articles/PMC7578360/
@johncarlosbaez @BartoszMilewski
A few years ago I read that eyes evolved independently 7 times, but the current factoid seems to be more like 40 times, which is quite a difference.I'm also puzzled: there are books from the 1950s that refer to the pineal glad as a mystical "third eye" -- obvious nonsense, but where did they get that from, if the origin of the pineal gland as a kind of eye is a much more modern discovery?
-
What's the most surprising fact you've learned in the last couple of weeks? I don't mind if it's quite technical. I just want to hear what you folks are being surprised by!
At 50km altitude on Venus the temperature and pressure is similar to Earth
-
@johncarlosbaez @BartoszMilewski
A few years ago I read that eyes evolved independently 7 times, but the current factoid seems to be more like 40 times, which is quite a difference.I'm also puzzled: there are books from the 1950s that refer to the pineal glad as a mystical "third eye" -- obvious nonsense, but where did they get that from, if the origin of the pineal gland as a kind of eye is a much more modern discovery?
@dougmerritt @BartoszMilewski - The Hindus have a tradition about a mystical "third eye", and Shiva is sometimes called the three-eyed lord. Later Descartes located the soul in the pineal gland. Maybe someone merged these ideas??? Worth checking out.
-
At 50km altitude on Venus the temperature and pressure is similar to Earth
@drdrowland - neat! But the air is... nitrogen, I guess? I don't see a good way for human life to take advantage of the nice pressure and temperature, but I never was good at inventions.
-
What's the most surprising fact you've learned in the last couple of weeks? I don't mind if it's quite technical. I just want to hear what you folks are being surprised by!
"Inside a jet engine, turbine blades are not just identical parts. Each one is uniquely measured, weighed and assigned a specific position. At speeds up to 18000rpm, the rotor experiences extreme centrifugal forces that multiply even the smallest weight difference."
-
"Inside a jet engine, turbine blades are not just identical parts. Each one is uniquely measured, weighed and assigned a specific position. At speeds up to 18000rpm, the rotor experiences extreme centrifugal forces that multiply even the smallest weight difference."
@ghasshee - wow, I didn't know the planes I ride rely on handcrafted (or more precisely, individually machine-crafted) parts!
-
@buo - I should learn what this *means*. I once almost knew what a Kalman filter is, and I know it's extremely important. But I don't know what a phase-locked loop is.
I love ODE, so this is embarassing! There's always room for progress.
-
@drdrowland - neat! But the air is... nitrogen, I guess? I don't see a good way for human life to take advantage of the nice pressure and temperature, but I never was good at inventions.
@johncarlosbaez @drdrowland Geoffrey Landis has used this observation to propose both manned missions to Venus and colonization in Venus's atmosphere.
Breathable air is a decent lifting gas, as the atmosphere is mostly CO2 (quite a bit heavier than both N2 and O2).
-
@johncarlosbaez @drdrowland Geoffrey Landis has used this observation to propose both manned missions to Venus and colonization in Venus's atmosphere.
Breathable air is a decent lifting gas, as the atmosphere is mostly CO2 (quite a bit heavier than both N2 and O2).
@isaackuo @drdrowland - I see, so colonizing it via air-filled balloon-like floating structures?
-
@otacke - I don't know enough about these deer to be surprised! They sound like European or British deer to me. Do they have overlapping ranges?
@johncarlosbaez I don't know any specifics.
Until yesterday, I believed that a "Reh" (roe, https://en.wikipedia.org/wiki/Roe_deer) was a female "Hirsch" (stag, https://en.wikipedia.org/wiki/Red_deer). But apparently they are both deer, yet different species - and not to be confused with fallow deers. Took me only shy over 40 years to learn that. 
β
οΈ -
@johncarlosbaez I don't know any specifics.
Until yesterday, I believed that a "Reh" (roe, https://en.wikipedia.org/wiki/Roe_deer) was a female "Hirsch" (stag, https://en.wikipedia.org/wiki/Red_deer). But apparently they are both deer, yet different species - and not to be confused with fallow deers. Took me only shy over 40 years to learn that. βοΈ@johncarlosbaez Now I wonder what type of deer Bambi is.
-
What's the most surprising fact you've learned in the last couple of weeks? I don't mind if it's quite technical. I just want to hear what you folks are being surprised by!
@johncarlosbaez That distilled water is completely safe to drink (contrary to what I learned in school)!
-
What's the most surprising fact you've learned in the last couple of weeks? I don't mind if it's quite technical. I just want to hear what you folks are being surprised by!
One of the stars of Hacks is Laraine Newman's daughter.
-
I was surprised to learn that there are small cleaner ants that clean bigger ants of a different species.
If one insect wants help with cleaning, why choose another smaller insect of the same family? One could imagine so many other willing arthropods.
Magnus (@magnus@mastodon.world)
Attached: 1 image Did ants learn this from cleaner fish? There are small ants that clean big ants without meeting any agression, just like small cleaner fish can clean sharks. https://onlinelibrary.wiley.com/doi/10.1002/ece3.73308
Mastodon (mastodon.world)
-
Ancient Rome consumed lots of oil and they didn't reuse the large Dressel 20 amphora barrels. Monte Testaccio in Rome is a 'trash mountain' made of 53 million broken olive oil amphorae.
@maxpool - "53 milllion" is where I got surprised.
I wondered how long they dumped those amphorae there, so I looked it up on the Wikipedia article:
"Deposits found by excavators have been dated to a period between approximately AD 140 to 250, but it is possible that dumping could have begun on the site as early as the 1st century BC."
So, at least 110 years, but maybe over 250!
