Starship Asterisk*

Thanks, Mark. I actually meant to post this Friday and it somehow got lost in the shuffle. When I saw your post I went looking for where I posted it, not to be found of course. I thought it was an interesting article. Here is the referenced paper: Asymmetric Dark Matter and the Sun Physical Review ...

I pasted the mysterious photo on the top of another one of the Belt of Venus – by the way, also taken from the South African Astronomical Observatory-... That image is not an APOD. It is found in a page linked from this APOD , but that isn't an allowable mystery image. I thought something was fishy...

Actually, I didn't mention acceleration, just velocity. So if I'm sitting here on my unaccelerated train connected by strings, it shouldn't matter that other trains pass me by with any velocity or acceleration -- my strings won't break. And the same goes for any constant velocity train that passes ...

What about friction and drag? Would friction not cause the track to heat up at these speeds (depending on the size of the track (but I'm thinking that if the trains are spaced equally then the friction would be constant enough to heat the track up sufficiently enough to make it fundamentally useles...

[....]Our fallacy was to attempt to extract a "spatial geometry" from the metric by ignoring the time coordinate, and nevertheless expect the spatial geometry to give sensible results about things that involve time (namely: the motion of sleepers under the train). I think I'm reading that...

It turns out that this problem is famous enough to be named; it is Ehrenfest's paradox , and the Wikipedia article even contains a diagram showing foreshortened railway cars on a circular track! (Predictably, the Wikipedia editors do not quite agree among themselves about the correct resolution, th...

This is entirely a "thought" experiment, so: "Train cars sit on a circular track connected by taut strings. The train cars all begin to circle the track at once, faster and faster, eventually reaching relativistic speed. What happens to the strings?" Do you mean that there is a ...

Related to it is the sealevel equipotential, a surface on which gravity is everywhere equal to its strength at mean sea level. However, when one travels by boat into the Indian Ocean one essential weighs the same because one is traveling on an sealevel equipotential surface. Very good point Art. By...

We should assume the reference frame at rest wrt the train track correct? I've answered my own question: Both reference frames are important in order to arrive at an acceptable answer.

This is my best contender so far.

If I have incorrectly interpreted the data, no problem, I just want to get it right.. but I still think you were right the first time :) ae OK...try this: The oblate spheroidal earth has a matching oblate spheroidal equipotential surface and hence is in overall equilibrium. However, if the earth we...

Not so fast Art, I'm quite sure you were right the first time :shock: That would shock :shock: no one more than me, alter-ego. Mountain ranges are clearly high points in the geopotential such that on either side of mountains there are horizontal geopotential gradients (i.e., horizontal gravitationa...

I believe one would weigh MORE in a red zone since that is where an open ocean would accumulate due to its higher gravity. Well, I've got to correct myself once again. :oops: The open ocean accumulates in the red zone due to its LOWER gravity allowing for the ocean to expand out (just as it expands...

So, is our fun meter pegged yet?

Sorry, but I disagree. Instead of scissors perhaps you can imagine two long lines of rocketships spaced out along what would have been the edges of the scissors, the rockets aimed directly at each other. Each rocket preprogrammed to start at the same time, only the distance between the lines of roc...

geckzilla wrote:Alright, I've played your game... now where's mah cookie?
http://apod.nasa.gov/apod/ap020522.html

Bingo! Nice job! Heck, I'd say you deserve at least two cookies!

I believe I may have found it, possibly? It maybe isn't but I have literally spent HOURS looking for it and this is the best and closest match I've found. I think you;ve been sneaky in flipping it. And I think its quite a close crop due to the grainy nature of the photo, so this one makes sense to ...

At first I thought the curved meteor trail was special, but I think it's the artifact of the near-matching image field curvature visible in the Milky Way. Comments?

swainy wrote:Hi alter-ego

looks very much like http://antwrp.gsfc.nasa.gov/apod/ap100617.html to me. But i think it is just very close and no match.

tc

I believe, without a doubt, that there won't be any question in your mind you've found it when you see this APOD.

swainy wrote:Hi alter-ego

looks very much like http://antwrp.gsfc.nasa.gov/apod/ap100617.html to me. But i think it is just very close and no match.

tc

Sorry, swainy, that's not it. I thought / hoped there would be several look-alikes to pick from.

Clearly, if we work the scissors exclusively from one end , we cannot make the vertex travel faster than light. (At least not unless the blades have some very weird elastic properties such that they won't meet close to us until our impulse has had time to travel down to points far from us, in which...

bystander wrote:No, save it for a hint. Maybe not even your first.

There is a diagonal from top left to bottom right. Is that of some significance in the picture as a whole?

It certainly is in my opinion. It wasn't the first thing I noticed, but it is directly related to the focus of the APOD.

alter-ego wrote:I think this one is fair -- cropped only. Sorry it's not exciting

There are a few hours left for me to edit the mystery picture. If there is a voice of consensus out there, I can re-crop the picture to show a teense more that might be more helpful in visual searching.

We need to clarify to what we are referring as the vertex. If we are talking about the point about which the blades pivot, the the answer is obviously no. That point is fixed with respect to the blades and does not move at all (unless the scissors move). However, if we are referring to the point wh...