It comes from the solutions manual for a text on tensor calculus. I don't own the book (considering getting it for study), so I don't actually know what the problem statement is, but essentially it involves writing out the third order partial derivative of a function of two variables (mu and nu). The result is a mess -- a sum of three expressions which are shorthanded as I+J+K, and this page is only showing what I is.
The purpose of this exercise is probably not so much to gain insight to any physical problem (I sure as heck couldn't tell you anything meaningful from it), but instead to help show the student the motivation for introducing the tensor notation, wherein these expressions become far more elegant. And as practice for cranking through this kind of calculation.
What use are the calculations? If the concept of tensors is foreign, here's a short primer: Often we are faced with a mathematical or physical problem with a clear geometric meaning, and in our education we have been taught to solve it by applying a coordinate system to it and write algebraic expressions. This is great for very many kinds of problems, but it comes with a downside. Our solutions depend as much on our choice of coordinates as on the physical problem itself. How do we know if a feature of a solution represents a property of the coordinates or a property of the reality?
Tensor calculus is a method for overcoming this pitfall. Here we find solutions that are independent of coordinates, and tensors are the coordinate-independent geometric objects which help us to transform expressions from one coordinate system to another as we please. And this is important to getting a deeper understanding of reality. For example, distances in space and intervals in time are different for different observers, and thus are not actually properties of the underlying reality. But the way in which they transform between those observers is (this is a property of the space-time). This also shows up in things like engineering (stress tensor), electromagnetism (Faraday tensor), and so on, as well as in pure mathematics.
An Englishman, a Frenchman, an Italian and a German are all standing watching a street performer do some excellent juggling. The juggler notices that the four gentlemen have a poor view, so he stands up on a large wooden box and calls out: "Can you all see me now?"
I took a wrong turn while driving today. My GPS glitched up massively and told me something like 'continue 248 billion, 612 million, 892 thousand, 388 miles, then turn right'. It wasn't that exact number, but it was two-hundred something billion.
A few days ago i got a package from DoctorOfSpace. This is what i found within. I will be testing these products over the next few days and post my thoughts. I have never tried most of the stuff here and i'm slightly dreading what i might experience.
On Saturday I'll have a day off while in the San Jose area, CA. Is the Lick Observatory worth a visit? I've never gone there.
I've done short hikes in the forests N and S of SF several times when I've had time off during earlier visits to the bay area, so I was thinking to try something different this time.
Haven't been, but I would check it out. It looks like a really nice view from up there, and the observatory itself should be really interesting. They still have the 36-inch refractor from 1888, and I'd also like to see the adaptive optics system.
Tastes very close to beef jerky, but "darker". Very delicious and i am sad that i can't buy more when it runs out. The marinade is a bit too sweet imo, but it goes well with the meat, so i won't complain. Could have less salt though. 8/10, would totally eat again.
Pearson Ranch Hickory Smoked Buffalo Jerky:
Very spicy and much dryer than the Uncle Buck's jerky. The taste is probably closer to the taste of actual buffalo meat, while not having the sweet marinade of the other brand. 10/10, Best jerky i've had in my life by far.
Hershey's Cookies'n'Creme:
White chocolate with chocolate cookie chips mixed in. Pretty basic as white chocolate goes. Probably wouldn't buy if it didn't have the cookie bits, which make it taste decent. 4/10, I could probably get something locally that tastes better.
Cry Baby's Tears:
I've had candy that's more sour than this, but these actually taste good. Can't think of any local candy that tastes like this. I would give these 6/10. Good, but nothing amazing.
Doritos Dinamita:
Bright red. These things are bright red like nothing edible should be. They have a nice heat, but it feels very "technical". 7/10, They don't really have much taste outside the heat and basic doritos taste, but i do like anything spicy, so i'll happily eat these.
Mtn Dew White Out:
Unfortunately the cans were frozen on the way, since it's been around -28 celcius these last few days. The taste is citrusy and very mild, though that could be because of being frozen. Has that corn syrup taste all american soft drinks have. 4/10, would probably be much better with fizz.
Cheetos Cheddar Jalapeño:
Harder and crunchier than the cheese snacks we have. Good cheddar flavor with jalapeño heat. I like spicy snacks and cheddar flavor, so this is something i'd happily buy myself. 8/10, Could be a tad hotter.
AMP Energy Original
Bright green and very citrusy. Nothing like the energy drinks we have. Not really fan of the taste. It's kinda metallic and nasty. Also the color of these products is really worrying me. 4/10, Feels oily in the mouth and tastes nasty. Probably has more chemicals than any human should ingest.
Cheetos Flamin' Hot:
Cheetos with that bright red chili spice that the funyuns had. The cheese taste is good, but the chili spice looks and tastes very artificial. I liked the jalapeño flavored cheetos more, even though they weren't this spicy. 6/10, tastes like cheese and is full of chemicals. America in a nutshell.
Cheetos Flamin' Hot Limon:
These taste almost exactly like the previous stuff, with a hint of lemon. The lemon taste is very artificial, but all in all i think these are better than the previous cheetos. 7/10
Sweet Tarts Chewy Sours:
"No artificial Flavors" Ahahahahaaahahaha. Joke of the millennium. 5/10, Kinda like mentos, but with more chemicals and more chewy structure.
Cape Cod Waffle Cut Buffalo Cheddar:
These are one of the best chips I’ve had. I would prefer normal chips over the waffle cut ones, but in this case i don't mind it. Tastes like buffalo seasoning and cheddar, surprise surprise. 10/10, probably best thing in the box.
Funyuns:
Onion flavor held together with corn starch. Pretty basic as snacks go. Not bad, but i wouldn't buy any myself. 4/10, meh
Funyuns Flamin' Hot:
Same as above with the same seasoning as in the flamin' hot cheetos. I prefer these to the regular Funyns because these actually taste of something. Even though it's that frighteningly bright red seasoning. 5/10, I would buy these, unlike regular Funyuns.
Full Throttle:
Is this supposed to be drunk by humans? It is the same color as my shower gel and tastes the same as my shower gel smells. I feel like if I finish this, I might die of chemical overdose. 11/10 a true american product.
Venom Energy:
Tastes like the energy drinks here, although somehow it manages to taste even more artificial than those. It is amazingly toxic tasting and i will not drink more than a few sips. 0/10, i don't want to die.
Doritos Sweet Chili:
Really good doritos. Best kind i've had so far. Tastes like doritos and sweet chili, oddly enough. 8/10 I ate all of them before i finished writing this.
Sour Patch Watermelon:
Little balls of poison that taste like what companies think watermelon tastes like. They are a bit sour and dangerously addictive. Probably because of copious amounts chemicals. 6/10, it's candy allright.
Doritos Spicy Nacho:
Fairly basic nacho flavor with paprika and a bit of heat. I swear i have tasted this before, even though i have never eaten Doritos... 7/10, at least these aren't bright red.
Mtn Dew Game Fuel:
Frighteningly bright orange. Tastes like cherry, corn syrup, headshots, 360 no-scoping montages and Microsoft brand entertainment systems. 9.5/10 -IGN
Lay's Salt And Vinegar:
I think you could fly to the dark side of Mars and still buy a bag of Lay's salt and vinegar chips, and that place doesn't even exist. 7/10, Basic Lay's chips with salt and vinegar taste. I really like salt and vinegar, but Lay's chips are more fragile than anything on Earth, which means i got to enjoy a bag of dust. Sad thing is they were probably like that even before shipping.
Swedish Fish:
Don't know about the US, but at least here in Finland most candy sold in stores is made of the same stuff as this candy. Therefore this is the most generic thing in this bag. To those who don't know, these are basically chewy candy that tastes like fake strawberry. 5/10, i did like these, but i have been eating candy like this since i was a child.
Sour Punch Rainbow Straws:
Different colored candy straws that taste like sour fake fruit. Most of the colors taste like fake apple and the yellow tastes like fake citrus. I think the other colors are supposed to taste different, but i couldn't tell them apart. Just tasted like a load of chemicals and sugar. 2/10, made my fingers sticky and didn't taste that great. My girlfriend seemed to like them better though.
Now And Later Chews:
Very hard as chewy candy goes. All taste like fake fruit and are not too bad, except for the banana tasting ones. The banana ones taste so strongly of fake banana that I had to spit out the one I tried. 6/10, most flavors are good, even though they are just horrible chemicals.
Hot Sausage in Vinegar Solution:
This thing terrifies me. It is bright red (like many things so far) and apparently can stay fresh in room temperature to late 2016. As i cooked it, it started to blister and ended up looking like something from a horror movie. -9000/10, I only took a single bite and disposed of the rest. It only tasted of vinegar and nothing else.
Cooking photos. Not for the faint of heart. You have been warned.
ENG
New site
United States 
Spain 
Awesome response.
Norway 
Finland 
Pirate 
