Today I Learned

[BillTre]

Today I learned that in Detroit the 1967 riots remain to this day a popular topic of conversation. I guess for people who lived through it it was by far the most exciting thing that ever happened to them.

My granddad had stories about this, but he's dead now.
My dad knew these stories and could related them well, but he's dead too.
I don't care much about it myself. I would have been 14 and living in the DC area at the time.

 

[DeBangis21]

My granddad had stories about this, but he's dead now.
My dad knew these stories and could related them well, but he's dead too.
I don't care much about it myself. I would have been 14 and living in the DC area at the time.

Oh sorry!

 

[BillTre]

Oh sorry!

Not a big deal. Time has passed.

 

[Hornbein]

TIL that "if two wheels are spun on a common axis, the mutual gravitational attraction between the two wheels will be greater if they spin in opposite directions than in the same direction"

https://en.wikipedia.org/wiki/Gravitoelectromagnetism

 

[Hornbein]

When I was fourteen I was in a rank beginner blues band with Peter Saulson, who played the harmonica. Today I learned he is one of the bigshots administering the LIGO gravitational wave observatory.

 

[Hornbein]

Today I learned that Hideki Tojo had Remember Pearl Harbor engraved on his dentures in Morse code.

After the surrender American dentists removed all but seven of his bad teeth. One engraved the message on the subsequent dentures.

Mallory recommended complete upper and lower dentures, but Tojo refused because he thought it would be a waste of effort to make both dentures for someone about to be executed. Instead, he asked for only an upper set of dentures so he could speak well at his trial.

The word got out. Their commanding officer said he appreciated the joke but foresaw trouble. The dentists retrieved the dentures, ground off the message, then under investigation successfully denied all hankypanky.

https://www.wearethemighty.com/mighty-history/tojo-denture-prank/

 

[Swamp Thing]

TIL that sea levels would have been tens of meters higher if water had been perfectly incompressible.

 

[DeBangis21]

I learned that the more the arc length, the more the p.d b/w the electrode and the weld pool during stick welding.

Question: why is the transformer not shocking?

 

[DaveE]

p.d b/w

What?

why is the transformer not shocking?

What? I suppose it is shocking the arc it created.
What do you mean by "shocking"?

 

[phinds]

What?

p.d. b/w = Potential Difference BetWeen

 

[DeBangis21]

p.d. b/w = Potential Difference BetWeen

Yes

 

[DeBangis21]

What? I suppose it is shocking the arc it created.
What do you mean by "shocking"?

Electrocution! When one touches the transformer or connect the earth/welding lead (cable) to the machine with bare hands, there is little or no jolt most atimes.

 

[berkeman]

Electrocution! When one touches the transformer or connect the earth/welding lead (cable) to the machine with bare hands, there is little or no jolt most atimes.

Please do not touch energized conductors with your bare hands. We strongly discourage our members from competing for the annual Darwin awards, and punish them severely after they win one.

 

[DeBangis21]

Haha!

 

[phinds]

Electrocution! When one touches the transformer or connect the earth/welding lead (cable) to the machine with bare hands, there is little or no jolt most atimes.

And what is the voltage?

 

[DaveE]

The greatest hazard, in terms of accessible voltage, is when there is no arc. You should assume that the arc may extinguish at any time. For example, what if you suddenly have to sneeze, there's an earthquake, whatever...

So, you should assume that it is always dangerous. ALWAYS. If you aren't scared of the voltage, you are at risk. If you are assuming "I just wouldn't do that", you are probably wrong.

 

[Swamp Thing]

Please do not touch energized conductors with your bare hands. We strongly discourage our members from competing for the annual Darwin awards, and punish them severely after they win one.

Do you hang them in a gibbet?

Spoiler

 

[Tom.G]

Question: why is the welding transformer not shocking?

A quick search shows open-circuit AC voltages around 40V to 75V, often half of those values with an arc established.

WIth dry, calloused hands and a light touch, I would not expect much current flow at 40V -- the other extreme and I would expect at least the inability to let go!

(Russian Roulette anyone?)

[edit] Those welding gloves also keep the intense UV light off your hands, you can lose skin without them. [/edit]

 

[Rive]

Question: why is the transformer not shocking?

As far as I know none of the output terminals are grounded: it's kind of an isolation transformer setup, with extras (rectifiers and most likely other electronics these days). This will protect you somewhat under normal circumstances unless you touch (connected to) both terminals. What you most definitely should not do.

The usually recommended gear for welding (rubber soled boots and thick gloves) also has the function of isolation.

Just to keep the topic in the right direction (and also about those gloves):

TIL that what is the real point behind those thick and inconveniently oversized (!) leather gloves old style blacksmiths preferred to have.
... it's that convenient one handed swing to get rid of an overheated glove
Try that with a tight fitting modern glove... Not workin'

 

[Ivan Seeking]

I don't know if it will save farming but the technology looks very cool. I wonder about the energy cost per acre.

 

[KingGambit]

Today I learn (after watching all of Lucifer series episodes),
All angels' name end in el
Mikael,
Gabriel,
Raphael,
Remiel,
Jophiel,
etc...

 

[Ibix]

It's the word for God in Hebrew, and their names are all phrases that refer to God somehow.

Edit: or at least, the christian canonical angels' names are so. Whether a TV series stuck to that or just decided that anything ending in -el sounded angel-y is, of course, another question.

 

[jack action]

I don't know if it will save farming but the technology looks very cool. I wonder about the energy cost per acre.

You have to give it to marketing when it's time to come up with shocking images: "Save farming".

Like that industry could die. "Sorry guys, we can build cars, smartphones, and A/C units, but eating is now a thing of the past. We can't provide anymore."

Farming is the last activity people will stop doing.

 

[Ivan Seeking]

You have to give it to marketing when it's time to come up with shocking images: "Save farming".

Like that industry could die. "Sorry guys, we can build cars, smartphones, and A/C units, but eating is now a thing of the past. We can't provide anymore."

Farming is the last activity people will stop doing.

Yes, the title was unfortunate which is why I mentioned it in the first place. They may mean the economic viability of domestic farming in the US.
https://www.migrationpolicy.org/new...gly-have-compete-shrinking-agricultural-labor

But if it works as claimed it could be revolutionary.

 

[pinball1970]

It's the word for God in Hebrew, and their names are all phrases that refer to God somehow.

Edit: or at least, the christian canonical angels' names are so. Whether a TV series stuck to that or just decided that anything ending in -el sounded angel-y is, of course, another question.

Yes, Elohim - Gods

Isra-el - wrestle/struggle with god

 

[DeBangis21]

TIL, just a moment ago, from sir Zz 2010 thread, that Accelerator Physics is an inter-disciplinary field between Physics and EEE/ME.

That catapult my interest, afterall ME was my first choice, then PHY.

 

[Janus]

TIL, while doing my lessons on Duolingo, what appears to be two Finnish idioms:
Svengaa kuin hirrvi - "swings like a moose"
Used as in: " This music really swings like a moose".
The other is "Täysi susi" - "full wolf"
which means "a complete failure"
I can see where täysi(full) can also mean "complete", and at first I thought maybe susi just could have more than one meaning, such as kuusi meaning both a spruce tree and 6 (or in some odd circumstance, "your moon".) But so far, no Finnish to English translator returns anything but "wolf".

 

[Ivan Seeking]

Recently I've been learning about molten chloride fast nuclear reactors.

Unfortunately, like most of the cool stuff I do, I can't talk about it.

 

[Tom.G]

Ahh... but now the "Other Side" is 'Coming to Take You Away, Away'!!

 

[kyphysics]

This Monday, 3 July 2023, was the hottest day ever recorded globally, according to data from the US National Centers for Environmental Prediction.

The average global temperature reached 17.01C (62.62F), surpassing the August 2016 record of 16.92C (62.46F), as heatwaves sizzled around the world.

https://www.theguardian.com/world/2...temperature-on-record-as-climate-crisis-bites