What's the most surprising fact you've learned in the last couple of weeks?

[dougmerritt@mathstodon.xyz]

@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?

[drdrowland@fediscience.org]

@johncarlosbaez

At 50km altitude on Venus the temperature and pressure is similar to Earth

[johncarlosbaez@mathstodon.xyz]

@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.

Third eye - Wikipedia

(en.wikipedia.org)

[johncarlosbaez@mathstodon.xyz]

@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.

[ghasshee@mathstodon.xyz]

@johncarlosbaez

"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."

X (formerly Twitter) (x.com)

[johncarlosbaez@mathstodon.xyz]

@ghasshee - wow, I didn't know the planes I ride rely on handcrafted (or more precisely, individually machine-crafted) parts!

[johncarlosbaez@mathstodon.xyz]

@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.

[isaackuo@spacey.space]

@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@mathstodon.xyz]

@isaackuo @drdrowland - I see, so colonizing it via air-filled balloon-like floating structures?

[otacke@chaos.social]

@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. ‍️

[otacke@chaos.social]

@johncarlosbaez Now I wonder what type of deer Bambi is.

[pschwahn@mathstodon.xyz]

@johncarlosbaez That distilled water is completely safe to drink (contrary to what I learned in school)!

[aspiringluddite@medievalist.masto.host]

@johncarlosbaez

One of the stars of Hacks is Laraine Newman's daughter.

[saltywizard@beige.party]

@magnus @johncarlosbaez

@futurebird

[johncarlosbaez@mathstodon.xyz]

@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!

[saltywizard@beige.party]

@johncarlosbaez

@Lambo got here first with my top fact, so i'll go with this one:

transit operators in the u.s. are not authorized to question the pedigree of your 'service animal.'

as long as you identify the animal as such, you are permitted to bring it on the bus.

*any* animal.

[maxpool@mathstodon.xyz]

@johncarlosbaez @buo

In phase locked loop output signal phase tracks input signal's phase. It's like automatic tuning, Frequencies synchronize through feedback.

Think tidal locking, or two pendelums in the same beam. I'm not sure 100% sure but I think Josephson effect is also like this.

[johncarlosbaez@mathstodon.xyz]

@saltywizard - what are the most crazy examples of service animals that have been recorded?

@Lambo

[saltywizard@beige.party]

@johncarlosbaez @Lambo

i've heard local anecdotes about a pony on the bus, but i haven't researched national trends.

[johncarlosbaez@mathstodon.xyz]

@saltywizard - I feel there should be YouTube videos about this....

@Lambo