What is the newest installment of 'Random Thoughts' on Physics Forums?

[fresh_42]

Now that know the name, I guess I can find the video or something similar.

Don't. Flipping a pot of dough isn't worth it.

 

[WWGD]

You'd think the CD drive in a Windows HP could be opened manually. Not quite.

 

[gmax137]

Windows HP

what's a "HP" ??

 

[fresh_42]

what's a "HP" ??

Guess Hewlett Packard.

 

[gmax137]

My CD drives had a small pinhole that I could poke a paperclip into, to force an eject. Also in Windows explorer, select the drive and "eject"

Are those not working, @WWGD ?

 

[WWGD]

My CD drives had a small pinhole that I could poke a paperclip into, to force an eject. Also in Windows explorer, select the drive and "eject"

Are those not working, @WWGD ?

It was for a gig.
I could determine there was a CD Drive from the File Explorer, but did not see an option to eject. Will check Windows Explorer next time. It seems you can eject the drive by going to ' Options'. I was not even aware ' Options' was an option ;).
And, yes, HP stands for Hewlett Packard.

 

[kyphysics]

Every new thing introduced to the market goes through a period of being better than everything else and consumers deciding if it’s better enough. The VHS and Betamax wars for dominance bear out how one technology gets adopted over another..

For me, it was a price/quality thing.

I just didn't find Blu-rays worth it over DVDs for the price/quality difference.

I'm curious, though, why some people still buy and collect records. Is there a unique sound they like from them? Are they like collectible "antiques" that may have future rare art-like value? etc.

 

[jedishrfu]

REcord collecting is somewhat of a retro thing. I always felt they were to easy to ruin just by bumping the record player and having the needle skitter across the record zippppp.

 

[WWGD]

I still can't tell the difference between a Latin Square and a Sudoku ( of same size, of course)

 

[Mayhem]

this is my learning curve. Basically I'm super stupid for 2 months, then something clicks and I have a quasi-exponential growth in understanding. Anyone else feel this way?

 

[Borg]

Yes but the slope isn't usually that large.

 

[valenumr]

View attachment 292115
this is my learning curve. Basically I'm super stupid for 2 months, then something clicks and I have a quasi-exponential growth in understanding. Anyone else feel this way?

That's me for sure.i struggles with diff eq, for example, until my roommate (pretty smart smart physicist working on his doctorate), clearly explained the integrating factor method to me. About a month worth of head scratching all came together in an instant.

 

[valenumr]

I was thrown off by a question while tutoring, around an hour ago. Sharp kid, while doing the standard proof of the infinitude of primes, the student asked me: if we did not consider 2 to be a prime, how would we change the proof, since the product $p_1p_2...p_k +1$ will always be even? I will just tell him that I leave it as an exercise for him. EDIT: I just suggested that we may just add 2 to the product , instead of one, but I am feeling too lazy to make this into a through argument.

Hmmm. Interesting thought, but why does it matter? The product of any number of primes is by definition not prime. Two is interesting as a prime by the fact that it is the only even prime, but it's also not that interesting.

 

[Keith_McClary]

learning curve

Sometimes I got to that point and thought "Oh, I get it. I'll work out the details later."

 

[WWGD]

Hmmm. Interesting thought, but why does it matter? The product of any number of primes is by definition not prime. Two is interesting as a prime by the fact that it is the only even prime, but it's also not that interesting.

But notice I am adding 1 after the product: #p_1p_2...p_k +1#

 

[valenumr]

But notice I am adding 1 after the product: #p_1p_2...p_k +1#

Ah, I missed that. Interesting question then, maybe. I mean, if you multiply a bunch of odd primes and add 1, the answer will be even, obviously, so perhaps I misunderstood the point.

 

[nsaspook]

If you think 2020 to 2021 was bad.
https://en.wikipedia.org/wiki/Soylent_Green
"By the year 2022, the cumulative effects of overpopulation, pollution and an apparent climate catastrophe have caused severe worldwide shortages of food, water and housing."

 

[WWGD]

Ah, I missed that. Interesting question then, maybe. I mean, if you multiply a bunch of odd primes and add 1, the answer will be even, obviously, so perhaps I misunderstood the point.

Ah, I missed that. Interesting question then, maybe. I mean, if you multiply a bunch of odd primes and add 1, the answer will be even, obviously, so perhaps I misunderstood the point.

That was the whole issue: The "Standard Proof" of the infinitude of primes would not go through

Standard proof:
For any k, consider the first (ordered by magnitude ) primes $p_1,p_2,...,p_k$. This includes
$p_1 =2$
Then $p_1p_2...p_k +1$ is either a prime, or if it's not, it's divisible by some prime $p_j$, which must be larger than$p_k$, supposedly the largest prime. If the expression is a prime, then it is a prime larger than the (alleged) largest prime.

So, as you said, if we did not consider 2 a prime, the "Standard" proof assuming 2 is prime, would not go through.

 

[nuuskur]

Heroes do not have to wear capes.

Spoiler

 

[Astronuc]

It is a serious matter to miss such a defect in a critical structure. There are signs of corrosion, and one has to wonder what else has been missed. An inspection should be based on the most highly stressed areas of the bridge, since that is where corrosion and fatigue are mostly likely. It is clear that the inspection program was deficient.

In fact, the Inspector who failed to catch interstate bridge crack fired, according to the AP.
https://apnews.com/article/business-205afe66ae13ef7cd945db9c48947da1Edit/update: ARDOT Confirms Failure in Inspection Process and Vows to Increase Redundancies to Avoid Repeat Event
https://www.ardot.gov/news/21-134/

It appears from the last paragraph that there was evidence of 'the crack' from May 2019. It's not clear to me at present, if they are saying the crack was partial or fully through the beam. If it was clear that there was a crack, then there was a complete failure in the inspection process that allowed continued operation of the bridge in that condition.

I-40 bridge report: Fracture in Memphis bridge may date back decades​

https://www.msn.com/en-us/money/oth...mphis-bridge-may-date-back-decades/vi-AAQDGrT

https://www.tn.gov/tdot/projects/region-4/i-40-hernando-desoto-bridge.html

https://www.ardot.gov/divisions/public-information/40-ms-river-bridge/

After the discovery of the fracture on May 11, 2021, the initial internal investigation verified that the crack was visible in 2019 and 2020. This resulted in the May 17, 2021 termination of the inspector responsible for inspecting this portion of the structure for at least the past 2 years.

Findings:

• It was verified that the crack was visible at least as early as 2016.
• The terminated inspector was directly responsible for inspecting that portion of the Bridge in 2016, 2017, 2019 and 2020.
• Management’s failure to adequately act on reports by employees concerned with the terminated inspector’s job performance perpetuated a culture where team members did not feel they had the authority or support to question a lead inspector’s procedures or thoroughness.
• The bridge inspector responsible for this portion of the Bridge in 2018 had never inspected this portion of the bridge before. There was a lack of adequate management and organization by administration. The inspector has been verbally counseled and will receive additional training.

There is something to be said for 'fresh set of eyes', but the eyes need to be experienced and qualified.

The fracture discovered on May 11th by Michael Baker International, occurred in a welded splice between two plates in the tie girder of the bridge. Upon closer examination of the specimen it was discovered that the initial fracture formed in an area of the weld where two weld repairs had been performed during fabrication. The weld repairs were more susceptible to cracking because of the type of steel and the welding method used in the fabrication of this bridge in the 1970s [probably sensitized and no post-weld heat treatment (PWHT). Inspection (NDT) methods/equipment were not as robust in the 1970s as they are now]. In all likelihood the cracking in the weld occurred within hours of its completion but was not detected by any post-weld repair fabrication testing and remained unchanged for a number of years.

In the 1980s, the potential for cracking in welds was identified at a national level because of defects found in other similar bridges, and in 1982 an ultrasonic testing inspection of the Hernando de Soto tie girder welds was performed. The defects at this weld location went undetected.

The fracture report described how the crack propagated in three phases from the cracking of the weld repairs to the eventual fracture that was discovered in May of 2021. The initial fracture occurred on the interior face of the box where it was not visible by conventional inspection. The second phase of crack propagation fractured through the remaining thickness and was later identified in the 2019 drone video. The third fracture event propagated up the remaining web, across the top flange, and arrested in the flange to web weld of the tie girder. It is likely the existing weld cracks became unstable as a result of a unique combination of low temperatures, increasing tie girder stress, and the effects of live loads (aperiodic medium to high stress with low frequency) to which the bridge had not been previously subjected.

Given the 48-year service life of this structure, the fact that the subject fracture occurred in three separate phases over several years, the recent inspection efforts to identify welding defects, and no evidence of observed fatigue crack growth during this study, it is highly unlikely that a similar fracture will occur. However, it is prudent to continue arms-length fracture critical inspections with a focus on identifying any new visible cracks at these welds. Given that all other anomalies investigated originated on the inside surface of the tie girder, ultrasonic testing should be performed on a periodic basis.

 

[Astronuc]

Interesting perspective - Humans Have Broken One of The Natural Power Laws Governing Earth's Oceans
https://www.msn.com/en-us/news/tech...ower-laws-governing-Earth's-oceans/ar-AAQBKBt

The global ocean size spectrum from bacteria to whales​

https://www.science.org/doi/10.1126/sciadv.abh3732

 

[WWGD]

Just met someone , the type of " Glass in 99.9% empty". Wants to talk to me each time he sees me. I need a long nap afterwards.

 

[fresh_42]

Just met someone , the type of " Glass in 99.9% empty". Wants to talk to me each time he sees me. I need a long nap afterwards.

Save time and take it during.

I would quote Douglas Adams by what he said about how he invented Marvin the paranoid android but you haven't read him.

 

[fresh_42]

Interesting game. Whenever the ball is in the end zone, it is an interception. End of 3rd quarter: 0-3. And they say soccer is boring for its lack of goals.

 

[WWGD]

Strange. Microwave functions , swivel rotates, but food does not get warmed up. Just charged my phone in the same outlet. Edit: Someone seriously suggested I test the diodes. But I first need to move the spectrometer out if the way. Do they think I have a lab at home?

 

[fresh_42]

For all lunatics: have a view in the sky tomorrow night!

https://phys.org/news/2021-11-longest-lunar-eclipse-centuries-week.html

 

[WWGD]

I can imagine someone who's doing their math thesis issuing all math challenges to get free research towards their degree.

 

[ergospherical]

A fun thing to think about is, why does water fall out of an upside-down bucket, given that atmospheric pressure ($\times$ interface area) pushing up on it from below is much, much larger than the weight of the water...

 

[WWGD]

Or if people use refrigerators in Siberia in Winter. Do they use them to warm up food?

 

[collinsmark]

A fun thing to think about is, why does water fall out of an upside-down bucket, given that atmospheric pressure ($\times$ interface area) pushing up on it from below is much, much larger than the weight of the water...