Recent content by geordief

So I take your (and,presumably eveyone else's) word that the tangent planes of a sphere (and presumably of any "uneven sphere" ) can be formulated solely from measurements on the sphere. That being so what relation do those tangent planes have to the sphere itself? They are not "on" the...

@A.T. Without recourse to parallel transport?

The intrinsic curvature of a 2d sphere is measured (as far as I can tell) by the means of its tangent planes that lie in the 3d dimensions it is embedded in.(I think parallel transport relies on these tangent planes) So "intrinsic seems to still rely on the embedding dimensions as far as I...

Very pleased if that is the case as I have been trying to understand this concept for the last 10 years. I wonder if I can now try to get my head around the Levi -Civita(sp?) connection (which may hopefully be connected to non orthogonal bases. that I was inquiring after in a separate and...

If the turret of the tank is attached to the body by a mount that uses 100% non friction ball bearings ** and we send the tank around on a path that does not follow a great circle on the sphere does the inertia of the mass of the turret cause it to point in a different direction to the...

In this video I can see a person walking around lines of curvature on a sphere with an arrow strapped to his waist. His task is to keep the arrow pointed in the same direction How does he do this ? Does he use a reference point like the stars? (that only move very slowly) If that is how he...

Thanks very much for those answers So a tool it is but non orthogonal axes do occur in real applications.(the crystals seem obvious now that it has been pointed out) Yes I am interested in relativistic physics but lack any expertise. Very much a talentless amateur 😀

Suppose ,instead of the usual x,y coordinate system with an I basis vector along the x -axis and a corresponding j basis vector along the y-axis we instead have a different pair of basis vectors ,call them e and f along their respective axes. I have seen that this is an important...

But Paul Brady is with few peers and that is one of his best. Here is a cover that really imo "misses the mark" ( BD really is the closest to an (artistic) "Human God" that I have known in my limited existence ) (I think Dylan is a fan of Brady)

https://www.bbc.com/news/articles/c728ven2v9eo and the other main news websites. Does anyone have any idea what mechanisms could be involved?

Not repellent enough. Navalny deserves a standing ovation but sadly will never see it now.

There used to be a scam back in the days (some 50 years ago,I'd say) when a shoplifter /scam artist would go into a store and pretend to hide an item on his or her person. (presumably they would be aware that they were being watched by cameras or otherwise) Afterwards ,they would secretly...

Is it a sophisticated form of "playing possum"? https://eu.citizen-times.com/story/life/2016/04/11/nature-journal-good-number-animals-play-possum/82806258/

Great thread and Hugh Dennis' quote was worth the entrance fee. Could you reply "Thanks for that apology" -and leave the ball in their court?

I think I saw the expiry date had been updated to 2024. I assume there is a new owner and hope that whoever it is will restart the site. The old owner never answered the phone and let the membership dwindle (unless that was going to happen anyway) It has been a couple of weeks since the...