Today I Learned

[pinball1970]

I came across this stat when looking up something (physics for psychics on another thread)

https://www.telegraph.co.uk/educati...929672/Why-dont-more-girls-study-physics.html

Everyone knows about Einstein are the women trail blazers not promoted enough to kids?

Marie Curie, Jocelyn Bell, Rosalind Franklin, Emmy Noether?

 

[kyphysics]

Currently reading Peter Lynch's, One Up on Wall St., and learned that the bear market of the early 1970's took 15 years for the Dow and other averages to regain the prices reached in the mid-60's.

Dang...15 years!

Talk about needing patience to hold onto stocks!

 

[jim hardy]

You never ever see the wooshing eye movement when you move your eyes from one area to another. Your brain just stops formulating and constructing the world for a few milliseconds and just cuts off perception until your eyes have stopped moving.

When driving at night i am bothered by modern luxury automobile taillights that are pwm LED's . When i move my eyes i see a series of dots and it's really disturbing.

Check it yourself next time you're behind a Cadillac or Lexus .

i'd say perception doesn't stop it's just dulled.

old jim

 

[gleem]

I think the retina also has what is called persistence. i.e, the response to light does not decrease instantaneously to zero when the stimulus is remove. so a moving bright light will appear as a streak in your vision. The brain has to process the changing signal as well as it can and sometimes it doesn't get it right. Witnesses to accidents often do not agree with one another.

 

[nitsuj]

When driving at night i am bothered by modern luxury automobile taillights that are pwm LED's . When i move my eyes i see a series of dots and it's really disturbing.

Check it yourself next time you're behind a Cadillac or Lexus .

i'd say perception doesn't stop it's just dulled.

old jim

I agree,

I was watching a stream of stones being flung from a conveyor and was "playing" with following the stones visually. It was fun to see the stream of stones go from a blur, to seeing individual stones if I followed them visually.

 

[fresh_42]

TIL that the rate of applications for naturalization increased by 1200% since Brexit. (Has been named as a cause for the increasing number of double citizenships.)

 

[mfb]

In which country from which country?

 

[fresh_42]

In which country from which country?

From UK to Germany. As they keep their passport, a second one simply enlarges their options. Would be interesting to know how the British tax laws are, because Americans wouldn't have this option if they don't want to get taxed twice, as the US taxes by citizenship and not by location.

 

[CWatters]

British and European taxes are generally similar with different rates and allowances/deductibles. Some tax on where you are 'ordinarily resident' which isn't always the same as where you are living. This can sometimes mean you are you are taxed twice but we have double taxation treaties. Not all EU countries have Capital Gains tax so it may pay to realize gains before/after emigrating. Should always take tax advice before emigrating or it can cost you big time.

 

[Drakkith]

Today I learned that, fully fueled and loaded, the Saturn V launch vehicle + Apollo spacecraft had a mass of nearly 3 MILLION kg! Each of the five F-1 engines on the 1st stage burned just over 2500 kg of fuel and oxidizer each second, pushing a combined total of 12,890 kg of mass out the back and propelling the vehicle with 35 MN of force! (that's MN for mega-Newtons. Yes, MEGA Newtons! Not your ordinary Isaac Newtons, but Isaac with his superhero pants on!) For those here in the states, that's 7.891 million pounds of thrust.

It sure beats the fins off of my 20 oz model rocket I had as a kid!

 

[mfb]

pushing a combined total of 12,890 kg of mass out the back and propelling the vehicle with 35 MN of force!

48 GW of power, about 10 GW per engine.

Each F-1 had a fuel pump with a power of 40 MW.

 

[jim hardy]

No chlorine in RP1.
Shuttle boosters had solid fuel, aluminum with polyvinyl chloride binder and ammonium perchlorate oxidizers -

and they complain about chlorine from car air conditioners ?

 

[Drakkith]

48 GW of power, about 10 GW per engine.

Each F-1 had a fuel pump with a power of 40 MW.

Speaking of power, I just launched my first Saturn V in Kerbal Space Program (with a realism mod added) and my S-IVB stage had exactly zero power. Because I forgot to add fuel to the fuel tank. (I blame the ground crew. The sign said "Full Service". At least it will once I get back!) Luckily it was an Apollo 8 style mission with no LM and I still had enough delta-v to get to the Moon and back.

Interestingly my orbital velocity around the Earth was only around 200 m/s after my TEI (trans-earth injection, the engine burn to get out of the Moon's orbit and back to Earth's), while my orbital velocity around the Moon was somewhere between 1k and 2k m/s. Nothing like trying to understand linear velocities along curved paths while transitioning between moving reference frames in three dimensions to get the brain juices flowing!

 

[Fewmet]

Today I learned how to identify the back locust tree. This came shortly after I learned that the black locust has thorns.

 

[phinds]

Today I learned how to identify the back locust tree. This came shortly after I learned that the black locust has thorns.

And did you learn that the hard way ?

 

[BillTre]

Today I realized that a guy, Shaun, who I deal with occasionally and who recovers tissues from deceased donors for transplanting, is...

Shaun of the Dead!

 

[Phys12]

Today...a few days ago, actually...I learned that the capital of Turkey is *not* Istanbul. I had been living a lie for the past 19-20 years.

 

[jim hardy]

Today I learned how to identify the back locust tree. This came shortly after I learned that the black locust has thorns.

Yep they'll go clear through a boot or tractor tire.

 

[jtbell]

Just now I learned that the melody for "God Save the King/Queen", which is used on this side of the pond for "My Country 'Tis of Thee", was used at George Washington's inauguration in 1789, 33 years before the latter song was written. On that occasion the words were:

Hail, thou auspicious day!
For let America
Thy praise resound.
Joy to our native land!
Let every heart expand,
For Washington's at hand,
With glory crowned.

I wonder if the choice of melody was politically deliberate.

Was God Save the Queen played at John McCain's funeral? (BBC News)

 

[fresh_42]

Wiki says the melody for God save the Queen has been first published in 1744 with similar even older melodies. So the winner are the British in this case. Surprisingly "The Jacobites also adopted the song with the introductory words "God save great James our king" ". Seems it served each side even before Washington.

 

[YoungPhysicist]

Today I learned about what exactly is a parabola

 

[Jonathan Scott]

Today I learned about gallstone problems. I had been thinking that my long-running acid digestion problems had produced some strangely severe spells of discomfort in the last few weeks, but yesterday's was really bad and I started Googling, and found that the symptoms matched a gallstone attack. I'm beginning to wonder whether other longer term symptoms could also be related to gallstones. I'll try to check it out with my doctor.

 

[YoungPhysicist]

Today I learned about gallstone problems. I had been thinking that my long-running acid digestion problems had produced some strangely severe spells of discomfort in the last few weeks, but yesterday's was really bad and I started Googling, and found that the symptoms matched a gallstone attack. I'm beginning to wonder whether other longer term symptoms could also be related to gallstones. I'll try to check it out with my doctor.

Hope getting better soon!

 

[YoungPhysicist]

Today I learned what is a circle equation on another thread!

 

[fresh_42]

Today I learned what is a circle equation on another thread!

Yesterday a parabola, today a circle. May I suggest to investigate cones?

 

[gleem]

Today I learned about gallstone problems. I had been thinking that my long-running acid digestion problems had produced some strangely severe spells of discomfort in the last few weeks, but yesterday's was really bad and I started Googling, and found that the symptoms matched a gallstone attack. I'm beginning to wonder whether other longer term symptoms could also be related to gallstones. I'll try to check it out with my doctor.

Twenty years ago so did I as I went to the ER. In previous years I had symptoms on occasion which I attributed to gas after eating turnips. Then one day the symptoms appeared but intensified to extreme nausea and abdominal pressure. I hand an extreme urge to belch but could not summon it. It was only after a naso-gastirc tube was inserted that relief occurred. Ultrasound exam revealed a blockage of the bile duct. Good Luck.

 

[YoungPhysicist]

Yesterday a parabola, today a circle. May I suggest to investigate cones?

On my list now
Just like @Greg Bernhardt says, random stuff that we learn everyday

 

[phinds]

On my list now
Just like @Greg Bernhardt says, random stuff that we learn everyday

The conics should not be "random stuff" they should be part of a course in mathematics. They are the basis for a huge amount of math.

 

[Spinnor]

Well it was a couple of days ago. If an electron is confined to a path that encloses magnetic flux then opposite moving eigenstates for a given value n have different energies. I knew about the Aharonov-Bohm effect but I did not know about this aspect of the effect, quite marvelous.

From (Google Chrome tells me this link is not secure, whatever that means), http://physics.gu.se/~tfkhj/TOPO/Aharonov-Bohm.pdf

 

[mfb]

Yesterday a parabola, today a circle. May I suggest to investigate cones?

Just don't mistake hyperbolas for hyperboles.

 

[phinds]

Just don't mistake hyperbolas for hyperboles.

Or ellipses from ellipsis

 

[DrGreg]

Just don't mistake hyperbolas for hyperboles.

Or ellipses from ellipsis

That's taking things too far...

 

[YoungPhysicist]

The conics should not be "random stuff" they should be part of a course in mathematics. They are the basis for a huge amount of math.

Yes, I know. I mean “random stuff that show up which are not in your plan) like bumping into circle equation on this forum which is not ,and will not be mentioned in my quadratic function courses.

 

[Ibix]

Just don't mistake hyperbolas for hyperboles.

One results from extremising the action; the other from extremising everything.

 

[fresh_42]

That's taking things too far...

Good that you mentioned it: Don't forget the Von Staudt conic!

 

[Drakkith]

Good that you mentioned it: Don't forget the Von Staudt conic!

I read that as the Von Staudt comic the first time...

 

[phinds]

I read that as the Von Staudt comic the first time...

A good indication of the level of your intellectual abilities.

 

[Drakkith]

A good indication of the level of your intellectual abilities.

It's true. My cone has been truncated.

 

[YoungPhysicist]

Yesterday a parabola, today a circle. May I suggest to investigate cones?

Finish investigating cones!(Not very deep though), but still a great thing to know beside ordinary courses.

 

[jim hardy]

https://en.wikipedia.org/wiki/Coneheads_(film)

one of the better movies i can think of

 

[CWatters]

Today I learned in the newspaper that when there is a leak in the ISS the air 'rushes out slowly'.

 

[Stavros Kiri]

Today I learned that this thread exists ...

 

[Phylosopher]

https://en.wikipedia.org/wiki/Coneheads_(film)

one of the better movies i can think of

Oh My God, what a weird poster. It is scratched in my head. I can't get it out!

 

[jim hardy]

The movie is a delightful sci-fi comedy about an alien family sent as a 'fifth column' for conquest of earth.
But they come to like the place.

If you've raised teenagers you'll love it. It's light hearted and well done.

old jim

 

[OmCheeto]

TIL that tiltmeters can measure tilt to a nanoradian.
Then I learned that a nanoradian is the equivalent of a nickel's thickness difference when viewed from a distance of New York City to San Francisco.

 

[Tom.G]

TIL that tiltmeters can measure tilt to a nanoradian.
Then I learned that a nanoradian is the equivalent of a nickel's thickness difference when viewed from a distance of New York City to San Francisco.

...And they can be purchased where?

On second thought, the price tag probably has too many digits. How about: ...And the plans are available where?

 

[OmCheeto]

...And they can be purchased where?

On second thought, the price tag probably has too many digits. How about: ...And the plans are available where?

As far as I can tell, they are strictly DIY.
You can contact Rex Flake of Central Washington University for the plans.

Btw, the ones he built were about a kilometer long, and I'm wildly guessing that they cost $50,000+ each.
Kind of a niche market for these things.

-------
ref:
discussion about the tiltmeters starts @ ≈21:00

further reading:

Slow Earthquakes in the Pacific Northwest

Michelson Tiltmeters​

 

[jim hardy]

Hmmm. Do they work by gravity, like this one ?

Great. Now i'll be worrying about effect on them from planetary alignment and barycenters... please tell me there is none...

 

[mfb]

Superconducting gravimeters levitate a sphere in vacuum and measure the electric current necessary for that. They achieve 10^-12 g precision for the local gravitational attraction. They should be able to measure sidewards forces in a similar way. A pendulum interferometer is great if you don't have local seismic noise.

Sub-nanorad tiltmeter with a pendulum

10 picorad resolution for angle measurements (relative to a given reference)

 

[OmCheeto]

Hmmm. Do they work by gravity, like this one ?
View attachment 230230

I'm not really sure.
Interestingly, the device was designed 99 years ago by A.A. Michelson, of "the Michelson–Morley experiment" fame, but one wasn't built until a couple of decades ago.

As far as I can tell, they just measure the difference in the height of water at the two ends, based on the change from when the devices are originally installed.

The data in the info-graphic doesn't quite match what the interviewee was describing, so I would ignore that.

Great. Now i'll be worrying about effect on them from planetary alignment and barycenters... please tell me there is none...

Good point! I hadn't even thought about that. Might be something to calculate.

The interviewee did discuss "earth tides" @ 09:00, something I just recently learned about.

Earth tide [wiki]

Earth tide (also known as solid Earth tide, crustal tide, body tide, bodily tide or land tide) is the displacement of the solid Earth's surface caused by the gravity of the Moon and Sun. Its main component has meter-level amplitude at periods of about 12 hours and longer.
...
The development of a systematic theory of Earth tides was started by George H. Darwin in 1879, and was then furthered by numerous authors, most notably by William Kaula in 1964.​

hmmmm... Sometime in the past, I think I mentioned that if I were to post here everything I learned every day, it would become the "What did Om learn today" thread.

So I'll close this out with;

Did you know that starfish don't have blood? They use seawater to transport their nutrients around their bodies.
Imagine how cool that would be.

Nurse; "Doctor! OmCheeto's leg has been cut off! He's lost huge amounts of blood! The blood bank says they're all out of O, A, and whatever blood types! What do we do??"
Doctor; "No problem. Om is a starfish. Just go out to the bay and collect some seawater. He'll be fine."​

ps. Ok, I'll close this again with:

Superconducting gravimeters levitate a sphere in vacuum and measure the electric current necessary for that. They achieve 10-12 g precision for the local gravitational attraction. They should be able to measure sidewards forces in a similar way. A pendulum interferometer is great if you don't have local seismic noise.

Sub-nanorad tiltmeter with a pendulum

10 picorad resolution for angle measurements (relative to a given reference)

I don't even want to know how expensive those suckers are.