# Challenge Solution #1

I've posted the solution for the First Challenge Question in the comments section to that post.  St. Jack Spell's comment here is the winner, and my answer key is here, along with some secret knowledge which I promised to "Andrew2" (St. Andrew II?)

Congratulations to Jack---As a prize, he may suggest the topic for a post.  (But no promises about when I would do that post.)

I am a Lecturer in Theoretical Physics at the University of Cambridge. Before that, I read Great Books at St. John's College (Santa Fe), got my physics Ph.D. from U Maryland, and did my postdocs at UC Santa Barbara, the Institute for Advanced Study in Princeton, and Stanford. The views expressed on this blog are my own, and should not be attributed to any of these fine institutions.
This entry was posted in Challenge Questions. Bookmark the permalink.

### 8 Responses to Challenge Solution #1

1. Andrew says:

Well done Jack

2. Jack Spell says:

Thanks, guys.

3. TY says:

Jack.
Good work!

Jack & Aron
Is there any connection between Nonrelativistic Metric and theology. I'm always on the prowl for connectivity. Does the physics -- time, spacetime, relativistic vs nonrelativistic -- reinforce or debunk received scriptural teachings, if any?

I like Jack's pick. May I add: The general notion of time. Which view of time is consistent with the notion of God's omnipresence, for example. The unidirectional "time arrow" through past, present, and future: or the relativistic notion that these 3 "tenses" are equal? In what special relativity sense is the future (yet to come) as real as the past (already gone)? Which is the "correct" view and why?

I have my notebook open and pencil sharpened?

4. Aron Wall says:

Jack,
Aren't there already a million* articles on the web explaining the Twin Paradox? For example, here's the Usenet Physics FAQ article.

*although I found only 152,000 results searching for "twin paradox" on Google...

5. Scott Church says:

There's more than one way to get a Twins Paradox. What about a question along those lines?

6. Jack Spell says:

It's not that I don't understand it and therfore it needs explaining, Aron. I just thought it might produce a cool potential problem to solve. But it was the first idea that popped in my head so feel free to go with another topic if you like.

7. Scott Church says:

Hmmm... It seems that articles about my other Twins Paradox ideas are all over the Internet too. Oh well...

8. willie says:

A possible topic for a post?
A spinning/rotating frame poses fascinating, even mysterious aspects.
The literature has a lot to say about simultaneity, contraction, observers on the disk etc. but is not clear about a stationary observer at the rotation axis.
In an article http://arxiv.org/abs/gr-qc/0103076 Robert D Klauber mention the remarkable property that “the local speed of a beam of light tangent to the disk circumference is not invariant, and not isotropic (as seen from the disk.)” and “Applying traditional relativistic concepts directly to the rotating disk leads to another striking difficulty. It predicts a discontinuity in time on the surface of the disk, and in addition, the location of that discontinuity is arbitrary, being merely a function of the particular predilections
of the observer.” The author contends that postulates of i) invariance of the speed of light, and ii) ”reference frame democracy”simply do not hold for rotating frames.

I wonder if it would be valid to make a connection between above and a cosmology model where the shape of the universe is toroidal and rotating. How would a observer in the rotation center of such a donut model experience the universe?