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

[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...

 

[ergospherical]

Nice, yes. The question is what exactly results in the instability of the air-water interface...

 

[collinsmark]

Nice, yes. The question is what exactly results in the instability of the air-water interface...

There's some math for that! (Actually, it's physics, but Brady Haran put this in the Numberphile series rather than the Sixty Symbols.)

 

[ergospherical]

How long can chicken be left unrefrigerated? I've cooked a little chicken/rice thing and need it to survive in a tupperware for about 14 or so hours in my bag... is that unreasonably long?

 

[Haborix]

How long can chicken be left unrefrigerated? I've cooked a little chicken/rice thing and need it to survive in a tupperware for about 14 or so hours in my bag... is that unreasonably long?

That sounds like a long time. I think general advice is no more than 1-2 hours. Personally, I wouldn't try your scenario.

 

[ergospherical]

Yeah this sucks, I'll just make a sandwich or something.

 

[fresh_42]

How long can chicken be left unrefrigerated? I've cooked a little chicken/rice thing and need it to survive in a tupperware for about 14 or so hours in my bag... is that unreasonably long?

Once it has been heated the usual suspects (salmonella) are destroyed. If you wrap it in or simply add a paper towel for the moisture, then I see no problem. I would eat it. However, the only chapter I remember from my English book at school was: "I have the stomach of an ox."

Maybe the window ledge is a good alternative to a refridgerator. Should be could enough in the UK at the moment.

 

[WWGD]

Yeah this sucks, I'll just make a sandwich or something.

How about using a Thermos?

 

[ergospherical]

How about using a Thermos?

Please elaborate...

 

[BillTre]

Please elaborate...

 

[fresh_42]

I ate (and eat) a day-old raw ground beef and never had problems. And a cooked meal will remain eatable within a day.

 

[DaveE]

Freeze it first?

 

[ergospherical]

View attachment 292724

Oh alright, I thought he was talking about the flasks you fill with hot chocolate and other warm beverages. Couldn't quite figure out how I was going to force the chicken through the nozzle.

 

[Frabjous]

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.

I like that they are tactile.

 

[WWGD]

Oh alright, I thought he was talking about the flasks you fill with hot chocolate and other warm beverages. Couldn't quite figure out how I was going to force the chicken through the nozzle.

Many have a removable cap that you unscrew by moving it counterclockwise.

 

[jedishrfu]

A freezer bag with one or two freezer packs (flat plastic bottle with water inside placed in a freezer beforehand to freeze) should refrigerate your food for several hours.

 

[ergospherical]

I thought this was funny; a 3D printed, meat-free steak endorsed by (legendary) chef Marco Pierre White
https://www.veganfoodandliving.com/news/marco-pierre-white-to-sell-3d-printed-vegan-steak/

Has anybody ever considered a vegetarian/vegan diet, either temporarily or more long term? Do the sustainability/health (?)/animal-welfare aspects outweigh the lack of variety (i.e. more difficult to obtain required nutrients, protein, etc.) and/or enjoyment of eating meat?

Surely it isn't long now until meat-alternatives become indistinguishable from real meat (for all practical purposes). Will be interesting to observe how diets shift in the next 50-100 years; maybe we will all be eating insects by then. Food for thought!

 

[WWGD]

I thought this was funny; a 3D printed, meat-free steak endorsed by (legendary) chef Marco Pierre White
https://www.veganfoodandliving.com/news/marco-pierre-white-to-sell-3d-printed-vegan-steak/

Has anybody ever considered a vegetarian/vegan diet, either temporarily or more long term? Do the sustainability/health (?)/animal-welfare aspects outweigh the lack of variety (i.e. more difficult to obtain required nutrients, protein, etc.) and/or enjoyment of eating meat?

Surely it isn't long now until meat-alternatives become indistinguishable from real meat (for all practical purposes). Will be interesting to observe how diets shift in the next 50-100 years; maybe we will all be eating insects by then. Food for thought!

As I understand it, vegan diets are not necessarily any more sustainable nor cruelty-free. Cutting down forests to grow crops destroys habitats for some animals. Pesticides and fertilizers ; tractors and combines kill animals as well. Cattle is ( ideally) fed in lands that do not serve agricultural nor other purposes. But my research on this is cursory so I cannot stand bt it 100%. As with just about everything else, issue has become politicized and it's difficult to tell what's what at times.

 

[ergospherical]

Although I’m most definitely not a vegetarian, it’s hard to deny that meat consumption is vastly more unsustainable both in terms of land requirements, deforestation (e.g. cattle ranching), resource/energy requirements and emissions. Although you do have a point about pesticides!

Personally I don’t think I’d be prepared to switch to a vegetarian diet, but meat alternatives might make that more attractive in years to come. And these sorts of innovations will be all the more important with projected future population growth / rising global standard of living.

 

[WWGD]

As I understand it, vegan diets are not necessarily any more sustainable nor cruelty-free. Cutting down forests to grow crops destroys habitats for some animals. Pesticides and fertilizers ; tractors and combines kill animals as well. Cattle is ( ideally) fed in lands that do not serve agricultural nor other purposes. But my research on this is cursory so I cannot stand bt it 100%. As with just about everything else, issue has become politicized and it's difficult to tell what's what at times.

I welcome rebuttals with specifics.

 

[BillTre]

I lived in a house with vegetarians for a couple of years.
While I found the diet different, if you are doing it with someone who knows vegetarian cuisine, it doesn't have to be boring or taste bad. Another reason to do this with a knowledgeable person is to avoid nutritional problems due to some foods lacking certain nutrients. Everything will easier if you doing it with someone experienced.

Although I like beef, cattle are not a good use of land and resources for the amount of food produced.

I doubt that 3D printed food or vegie meats will be cheaper than the real thing very soon. IIts pretty easy to grow and slaughter an animal. The animal does most of the work.