Recent content by jackiefrost

Shamir uses some interesting algorithms for detecting spiral galaxy rotation direction. Given the various caveats listed in the Conclusion section, it'll be interesting to see how results from the Large Synoptic Sky Survey compares to these more local results. I suppose that even though the...

I bought Ciufolini and Wheeler to get some insights into GR handling of inertia and Lense-Thirring frame dragging. Unfortunately I can't seem to find it and MTW doesn't seem get into it quite as well. I also was looking for some good background stuff on Gravity Probe B (the experiment was still...

I've read a good bit on Mach's principal as related to GR - esp. as portrayed in "Gravitation and Inertia" - Ciufolini and Wheeler, etc. I'll check out that paper. When someone calls a paper "beautiul, how can I resist? :-)

How can we tell whether the universe is rotating or not? Have we made a definitive determination yet? How does the notion of a rotating universe even have any meaning? What would a rotating universe be rotating in reference to? And lastly, if the universe were somehow rotating, would it...

Wow - 7 years later! How time flies when you're playing with this textbook and mathematical physics :-) I was intimidated by tensors before this book (continuum mechanics, too). So thanks to the author and thanks to Astronuc for the link. I still have a zillion questions but that's always the...

Sorry for the long delay. Both your explanations and the analysis makes good sense. Thank you both very much.

An April 18 newscientist.com article, http://www.newscientist.com/article/dn18775-mysterious-radio-waves-emitted-from-nearby-galaxy.html" reports recent observations of a radio source in M82 with an apparent horizontal motion of 4x speed of light. Could someone comment on what particular...

These stem from the separate derivations of W for electric field and magnetic fields. W for electric field results from integrating the product of electric potential and charge density over all space and W for magnetic field from integrating the scalar product of magnetic vector potential and...

Here's an interesting article on just this subject: http://math.ucr.edu/home/baez/entropy.html"

Wouldn't the best fit line for just two data points points, regardless of the uncertainties in the two points' y values, be a line through the two points themselves since their y values would necessarily be centered in the y error range? Therefore, wouldn't the gradient just be the slope of the...

I've often wondered if String Theorists consider spacetime as an ether of sorts. I guess it's a pretty irrelevant point regardless.

Good one!

Sal Kahn (Kahn Academy) has an impressive collection of mathematics and other tutorial videos. Mathematically, these range from basic arithmetic to differential equations. He's extremely good at providing essential background material while working out well chosen examples. He provides superb...

I always thought that "least" (or stationary) action type concepts or principles were kind of intuitively friendly when we consider that generally, we usually expect things to "move" or progress from one state to another with a natural economy. It makes sense that a physical system would tend to...

I know the black background problem with IE6 is an old, stale, issue but... my place of employment won't upgrade and Firefox doesn't work correctly on the network (ours) BUT - I found to my delight that Google Chrome doesn't get me in trouble with the IT ppl and displays Latex beautifully...