Today I Learned

[Ibix]

Is your theory not parity invariant?

Yes it is. The same happens if you say Lagrange-Euler three times in a mirror.

 

[Ahmed1029]

Yes it is. The same happens if you say Lagrange-Euler three times in a mirror.

But it isn't clear whether your theory conserves angular momentum.

 

[Ibix]

Yes it is. The same happens if you say Lagrange-Euler three times in a mirror.

You have to summon Noether to establish that...

 

[Orodruin]

You have to summon Noether to establish that...

If only we had a tool to commune with the dead …

 

[BWV]

If only we had a tool to commune with the dead …

Have to settle for an operator that commutes with the dead

 

[Orodruin]

Have to settle for an operator that commutes with the dead

If the dead Poisson commute with the Hamiltonian they are not likely to change.

 

[berkeman]

TIL that microwave oven turntables can start in either direction (random direction at each start). I've only looked in the oven window a couple of times when starting a cooking cycle, and have been confused by how the rotation direction did not seem consistent. I guess simple AC electrical motors do not have a preferred starting direction...

 

[collinsmark]

TIL that microwave oven turntables can start in either direction (random direction at each start). I've only looked in the oven window a couple of times when starting a cooking cycle, and have been confused by how the rotation direction did not seem consistent. I guess simple AC electrical motors do not have a preferred starting direction...

Yes, not having a preferred direction is a limitation of simple, single phase, AC motors.

This can be overcome by adding additional windings -- "starting windings" -- specifically to bias the starting direction. But this adds complexity and cost, and maybe even efficiency depending on how they're implemented. Household fans/airblowers are a common example of such systems.

3-phase, AC motors don't have such limitations.

 

[BWV]

Yes, not having a preferred direction is a limitation of simple, single phase, AC motors.

This can be overcome by adding additional windings -- "starting windings" -- specifically to bias the starting direction. But this adds complexity and cost, and maybe even efficiency depending on how they're implemented. Household fans/airblowers are a common example of such systems.

3-phase, AC motors don't have such limitations.

Did you check to see if it was manufactured in Australia? Think microwaves rotate clockwise in the Northern Hemisphere and counter in the South

 

[Tom.G]

Yup.
And it saves the manufacturer one turn of 12Ga. wire for the 'Shading Coil,' which can be completely eliminated.

https://en.wikipedia.org/wiki/Shading_coil
(Although I think the article got it wrong about the use in fans! Someone must have gotten confused about the 'stirrer' used in the early ovens to avoid standing waves and dead spots in the oven cavity, they looked a lot like fans with no pitch to the blades.)

 

[nsaspook]

John Cleese's Classic 'Silly Walk' Burns More Calories Than a Normal Gait, Study Finds
BMJ Christmas-week issue

 

[DaveC426913]

John Cleese's Classic 'Silly Walk' Burns More Calories Than a Normal Gait, Study Finds

In the immortal words of Stephen Colbert:

"Hey there, Science. Remember that cure for cancer? How's that comin' along?"

 

[kyphysics]

"Expected?" Sez who?

I tip when someone brings the food to me.

I worry the lack of a tip for take-out results in weird stuff happening to my food.

 

[DaveC426913]

I worry the lack of a tip for take-out results in weird stuff happening to my food.

How? When I go for take-out, I pay when they're handing me my food. It's too late to do anything at that point.

In what circumstance would one ever add a tip before one has actually been served their food?

 

[Hornbein]

How? When I go for take-out, I pay when they're handing me my food. It's too late to do anything at that point.

In what circumstance would one ever add a tip before one has actually been served their food?

Real nice gazpacho we got here buddy. Be a shame if anything were to happen to it.

In his autobiography a gangster revealed that he had to learn a Brooklyn accent in order to be taken seriously.

 

[pinball1970]

TIL Men are rubbish at Xmas?

A rant from two female colleagues complaining that their husbands contributed zero in terms of buying cards and presents for the family.
I was within striking distance and eventually they asked me.
Three relationships of note, I had to admit that my partners did it all.

Like my female colleague's husbands I admitted that I gave money to the partner and they did the choosing and buying.
I signed the cards without reading them and I remember practically begging one partner to take care of it as it stressed me out that much. I really hated it. I don't know when it kicked in, it is like drinking Guinness for the first time and wretching then some time later you are on your 4th pint trying to recall when hate turned to joy.
It just seem to happen.
I did slightly better than one of the husbands who did not even sign the cards.
I feel guilty if they truly despise the exercise as much as we (royal) yet they put up with it.
Noted that this is a FIRST world issue.

 

[Drakkith]

@pinball1970 Yes, I thought it was a pretty well known fact that women often take care of the 'social' aspects of the family. Buying gifts, planning events, etc. I admit that I too often let my fiance do more than her fair share.

 

[Jarvis323]

There is a single cell phytoplanktonic algae that encases itself in a dodecahedron shell.
https://en.m.wikipedia.org/wiki/Braarudosphaera_bigelowii

 

[Hornbein]

There is a single cell phytoplanktonic algae that encases itself in a dodecahedron shell.
https://en.m.wikipedia.org/wiki/Braarudosphaera_bigelowii

As far as I know the icosahedron does not occur in nature.

 

[Borg]

World's smallest D&D die.

 

[jack action]

TIL

Because of the phenomenal success of the book on which this film [The Other Side of Midnight (1977)] was based, 20th Century Fox was sure the film was going to be a huge hit at the box office. At the same time there were such low expectations surrounding Star Wars (1977) that many theaters refused to book it. 20th Century Fox came up with the idea of a package deal, telling theater chains that if they wanted this movie they had to book "Star Wars" first (that practice was actually illegal, and the studio had to pay a $25,000 fine for it). This movie went on to become a box-office dud while "Star Wars" went on to become one of the most successful films of all time.

 

[mikalluna501]

Today I picked up some new information on the official Wilbur Soot. As a researcher at my institution, this is one of my assignments. The countless guises and incarnations that Wilbur Soot has had throughout the years are generally referred to as "Bursonas."

 

[BillTre]

Here a nice little table from the NY Times for distinguishing among illnesses:

In the Times, it has a bit of interactivity.

 

[berkeman]

Hmm, they omitted "loss of taste or smell", although I think that happens less with the Omicron variant of Covid compared to Delta. But still... Oops, based on Dave's skeptical emoji, I read the list again and see it now. Thanks Dave.

 

[pinball1970]

Here a nice little table from the NY Times for distinguishing among illnesses:

View attachment 319592
In the Times, it has a bit of interactivity.

That is interesting and I am sure I am not the only one who has tried to work out what they have/had last week/last month!

 

[BillTre]

 

[Borg]

That looks more like a large piece of orbital debris.

 

[Drakkith]

That looks more like a large piece of orbital debris.

It is. It is a Falcon 9 second stage:

 

[pinball1970]

That looks more like a large piece of orbital debris.

It did remind me of the way Columbia re-entered and broke up.

 

[gmax137]

It did remind me of the way Columbia re-entered and broke up.

I was living in New Orleans at the time; on the news they said we would be able to see the planned Columbia re-entry at (I recall) 7 or 8 AM. I stood out in the apartment parking lot for 20 minutes, waiting and waiting. Finally I went back inside, and of course the disaster was all over the news... So sad.

 

[pinball1970]

TIL about The Monty Hall problem.

I came across this before without knowing the name, it was featured in a film or something.
By the time I was trying to work it they had moved on.
Came across it again so searched pf and there are several threads with great explanations.
It hurt my head to get there though.
Pretty sure I have it now.

 

[mfb]

It is. It is a Falcon 9 second stage:

From March 2021.

Multiple pieces slowly moving through the sky with big trails: Orbital debris.
A single piece (or pieces too close to distinguish) moving quickly: Meteors

 

[epenguin]

As far as I know the icosahedron does not occur in nature.

The capsids (shells) of so called "spherical" viruses all have icosahedral symmetry, and some of them have an icosahedral form.

 

[DaveC426913]

TIL about The Monty Hall problem.

I came across this before without knowing the name, it was featured in a film or something.
By the time I was trying to work it they had moved on.
Came across it again so searched pf and there are several threads with great explanations.
It hurt my head to get there though.
Pretty sure I have it now.

Be sure you have the latest. There was a "scandal" a while back where one of the smartest math savants in the world weighed in and passed judgement, but it turned out she'd gotten it wrong.

Apparently, the modern answer is that you **should** switch.

 

[gmax137]

Please, please do not continue discussing Monty Hall in this thread! Do a search (example below) and post your hopes and doubts in any one of the many existing threads!