pzkpfw

People have had hearts replaced by machines; not just having machines pump their blood temporarily during an operation, but permanent replacement. It's still a new science, and the success has been varied. But still, it would have been very obvious very quickly if the ability of the recipient to think had changed significantly. And what about heart transplants? Has any recipient of another persons heart woken up from surgery and asked "what am I doing in this body?"? This stuff is garbage.

Strange is right, that there isn't enough information there; but since I can see what you're trying to do with that, I'll just go ahead and (simplify, and) say "no". The thing is, if you're going to reject the shell theorem because it's an approximation, you can't just substitute that with another approximation. If you're going to insist on ignoring the shell theorem, you need to do something like actually calculate the effects of the individual stars outside the orbit of S2, not just talk your way into a claim that supports your idea. Go ahead.

It's true the setup isn't very clear about whether the train is still accelerating or not at the time the flashes occur, but that's not really what I was commenting about in your post. You just seemed to be implying an observer outside the train as having a "special" or "absolute" rest frame. Since they were at rest with the train and clocks at the start, I can see that's why you'd see them as "having" the frame within which the clocks are "still synchronised" (and I can't say I disagree (so my post #14 may be backward)); but that wasn't clear in your post.

That's from the point of view of an outside observer, which is no better opinion than that of an observer on the train who (while it isn't accelerating) is entitled to consider themselves as at rest. The relativity of simulatenity doesn't say one special observer can consider events to be simultaneous and others can't, it says events simultaneous for one observer won't be simultaneous for an observer moving in relation to that observer. (Or vice versa).

David, imagine you are floating in space with a mass in front, and another five equal masses the same distances behind, left, right, above and below you. That is, you are exactly in the middle of these six equal masses. Clearly all their effects will cancel out. e.g. The mass in front "pulls you" forwards, but the mass behind "pulls you" equally backwards. Now, using rockets move yourself towards the front mass, and then reverse to stop. You might think that now you are closer to the front mass (and further from the rear mass), it's "force" would be stronger and you'd be pulled towards it - that you'd begin to drift forwards. But that doesn't happen; because the masses that were left, right, above and below you are now also a bit behind you. Their "force" in the rearwards direction adds to that of the "force" from the rear mass. Newton, who could do calculus, figured out (proved mathematically) that inside a shell of equal density, these "forces" all cancel each other out. e.g. if Earth was a thin shell of ultra dense material, so that it's surface gravity was exactly the same as it is now, but it was hollow - you could be anywhere inside that shell and you'd feel no "force" of gravity in any direction. That's the Shell Theorem. And it's why, as we can treat the Galaxy as homogenous (all the stars more or less evenly spread), S2 can pretty much ignore the stars further out than it. It's the masses (such as the black hole) inside its orbit that matter most.

I would expect (but am very happy to be shown wrong) that the end clocks would remain synchronised in the frame of the train, as they're both experiencing the same acceleration on that train. So they'd both fire at their pre arranged time, with the flashes reaching the centre clock at the same time, and that clock does stop as expected. The outside observer, considering themselves as at rest and the train moving, would also see that centre clock stop (it can't both stop and not stop). From their point of view that clock was moving towards the light from the front clock and away from the light from the rear clock, so for the flashes to have reached that clock at the same time, the rear clock must have (considered in the frame of the outside observer) flashed before the front clock. Well, that's the relativity of simultaneity, as Einstein showed, observers in relative motion can't agree on whether events happen at "the same time". The only paradox is if one demands that simultaneity must be the same for all observers, which creates a centre clock stops and doesn't stop situation. But that's getting it all upside down.

Can a sacrificial metal be used to protect the electrodes?

See: http://en.wikipedia.org/wiki/Lunar_meteorite (A form of communication, very slow (compared to light), telling us about our Moon).

That's the standard idea. There's one cat (in my back yard). It changes position, e.g. BBQ table to birdbath. It also changes time, e.g. it was somewhere at 1 p.m. and it was somewhere at 2 p.m. If it was very lazy, it might stay in the same position, but be there at those two times. Who says that? We all change coordinates in time. I woke up at 6:30 a.m. this morning, now here I am at my PC at 7:23 a.m. My position in time and space has changed. I do note your earlier comment on the size of the cat (30 cm). Position (and physical extent) is measured in 3 dimensions, so the cat (an assembly of atoms, and what they're made of) has extent in height, width and depth. But time has a single dimension, so there's no equivalent "time extent" for the cat. It's somewhere at some time. A nanosecond later, that one cat may be in the "same" place (depending on what measured against) or it might have moved. Its space and time coordinates can have changed. But it's still one cat.

If I look out my window at 1 p.m. and see my cat on the BBQ table, then I look out again at 2 p.m. and see it on the bird bath, that simply means it's location (time and space has changed). It doesn't imply there's a bunch of other cats outside that I just haven't seen. (And any cat so far away that light from it hasn't reached me "yet", will have had no other effect on me.)

That page doesn't list magic. Nothing known will change the speed of light and the distance to your alien. Was this really a question or a sneaky speculation?

An airliner built like this could give its passengers a free lunch.

Drop observers on random Earth locations. One reports "its a desert" another reports "it's all water". Why should it all be the same? This line (about the cmb) seems like the " significance" some people put on the apparent size of the Moon re the Sun and eclipses. The Earth-Moon distance changes - that we now see a different thing than others did or will do is nothing amazing.

Go outside and face West. Jump 1 metre forward. Turn around (to the East). Jump 1 metre forward (back to where you came from). Was there any difference in your two jumps? Are you Superman, and was one of your jumps 1,000 miles per hour (as you measure it) "faster" than the other?

Please define "creates energy".

I do wonder. On a similar site he's been posting with the name "trollery" (and recently got suspended for a bit). (What happens on other forums is their business, so I'm not suggesting anything for here.) I see him as someone who has learned that 1 + 1 = 2, and then skips right to telling people how the Pythagoras Theorem is supposed to work. Unless it's deliberate ...

Moves, not makes.

Just for reference:http://www.thescienceforum.com/physics/46849-darkness.html

Two cars, both doing 50 miles per hour. One is going around and around an oval. One driving from Paris to Berlin. So what? Different paths: both are travelling at the same speed relative to the road. One seems to "get somewhere", the other doesn't. Yes, a tunnel from Paris to Berlin might allow an even straighter path (avoiding curve of Earth surface) but 50 mph is still 50 mph.

There's a lot to know. I sure as heck wouldn't have come up with calculus by myself, let alone many of the other things I learned in school. Now, maybe that has somehow held me back from coming up with some unique new mathematical insight - but I doubt it. I'm quite happy with the whole standing-on-the-shoulders-of-giants thing. Having said that: I very much agree with the sentiments in post #8.

Personally, I welcome our new squiggle-blob overlords. All hail the squiggle-blobs.

In the distant future, I can almost accept it'd be possible to scan the current physical content of a persons brain (synapses, connections between them ...), and "upload" into a computer. "Download" would be a whole other ballgame, as that'd require re-wiring the content of the destination brain, and there wouldn't be a 1-to-1 match of bits to re-wire; even if a mechanism were found (magic nanotechnology).

It takes two to tango. That is, Denmark and which other country?

I am utterly mystified as to why, after multiple explanations, you cannot understand the meaning of the words I've underlined for you. ... He continues that paragraph with "Observers who take the railway train as their reference-body ...". Section 9 also has near the start: "People travelling in this train will with a vantage view the train as a rigid reference-body (co-ordinate system); they regard all events in reference to the train.". Clearly there is no absolute motion involved. Both observers may consider themselves as at rest, and the other as in motion. That's a cornerstone of relativity. You seem to have the same problem (selective reading) with ... You've twisted that in several ways, also.

We've been over that. This is where I give up. You are determined to keep your odd interpretation, and this is all just going to go around in circles.