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Forum » SpaceEngine » Off-topic Discussions » Totally off-topic thread (Talk about anything.)
Totally off-topic thread
WatsisnameDate: Tuesday, 05.01.2016, 20:24 | Message # 2911
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An interesting choice of words.





 
FastFourierTransformDate: Tuesday, 05.01.2016, 22:16 | Message # 2912
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Quote Watsisname ()
An interesting choice of words


Please I'm courius, Where this comes from? what is explaining? Potentials in electromagnetism? biggrin
 
WatsisnameDate: Wednesday, 06.01.2016, 01:04 | Message # 2913
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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. wacko

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.





 
FastFourierTransformDate: Wednesday, 06.01.2016, 02:26 | Message # 2914
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Wow!!! Thank you Watsisname smile Awesome response.
Thanks one more time
 
midtskogenDate: Thursday, 07.01.2016, 11:29 | Message # 2915
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Linguistic joke:

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?"

"Yes"
"Oui"
"Sí"
"Ja"





NIL DIFFICILE VOLENTI
 
HandbananaDate: Friday, 08.01.2016, 05:51 | Message # 2916
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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.




Tonight... you.
 
WatsisnameDate: Friday, 08.01.2016, 07:39 | Message # 2917
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Whelp, enjoy your journey to the Oort! biggrin




 
Antza2Date: Sunday, 10.01.2016, 16:06 | Message # 2918
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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.

Attachments: 6331756.jpg(546Kb)





Go to antza2.deviantart.com for cool photos!
 
DoctorOfSpaceDate: Sunday, 10.01.2016, 16:21 | Message # 2919
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Quote Antza2 ()
i'm slightly dreading what i might experience.


The taste of freedom





Intel Core i7-5820K 4.2GHz 6-Core Processor
G.Skill Ripjaws V Series 32GB (4 x 8GB) DDR4-2400 Memory
EVGA GTX 980 Ti SC 6GB
 
WatsisnameDate: Sunday, 10.01.2016, 20:46 | Message # 2920
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They can never take our freedom! Funyuns and mountain dew forever! *salute*




 
midtskogenDate: Monday, 11.01.2016, 18:41 | Message # 2921
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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.





NIL DIFFICILE VOLENTI
 
WatsisnameDate: Monday, 11.01.2016, 23:51 | Message # 2922
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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.




 
DoctorOfSpaceDate: Tuesday, 12.01.2016, 08:32 | Message # 2923
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Intel Core i7-5820K 4.2GHz 6-Core Processor
G.Skill Ripjaws V Series 32GB (4 x 8GB) DDR4-2400 Memory
EVGA GTX 980 Ti SC 6GB
 
midtskogenDate: Tuesday, 12.01.2016, 19:38 | Message # 2924
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I didn't notice it before I got home and looked at the pictures, but a troll watched us today. (Sorry for the crappy mobile phone picture quality)

Attachments: 7761783.jpg(174Kb)





NIL DIFFICILE VOLENTI
 
DoctorOfSpaceDate: Wednesday, 13.01.2016, 14:28 | Message # 2925
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Intel Core i7-5820K 4.2GHz 6-Core Processor
G.Skill Ripjaws V Series 32GB (4 x 8GB) DDR4-2400 Memory
EVGA GTX 980 Ti SC 6GB
 
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