THX-1138

Perhaps not the right forum, but.. I want to make a glass-tubing helix, which will fit inside another glass cylinder. The intent is to use it for cooling some exhaust fumes and gas, but also to learn how to do it. The only idea I have in my head so far is to put a wooden dowel of the correct inside diameter in my lathe, and spin it very slowly as I heat the tubing to malleability and wind it onto the rotating dowel. I'm thinking wood because I've seen it used by glassblowers, and I don't want to use something like steel that's so heat-conductive that the glass will cool too quickly before it's finished being bent. Any thoughts? Thanks! Merged post follows: Consecutive posts mergedRe/cross posted to Chemistry > Applied Chemistry.

(Reposted from Amateur Science > Equipment) Perhaps not the right forum, but.. I want to make a glass-tubing helix, which will fit inside another glass cylinder. The intent is to use it for cooling some exhaust fumes and gas, but also to learn how to do it. The only idea I have in my head so far is to put a wooden dowel of the correct inside diameter in my lathe, and spin it very slowly as I heat the tubing to malleability and wind it onto the rotating dowel. I'm thinking wood because I've seen it used by glassblowers, and I don't want to use something like steel that's so heat-conductive that the glass will cool too quickly before it's finished being bent. Any thoughts? Thanks!

Suppose I want to run a normal low-voltage transformer in reverse -- i.e., running the line voltage through the secondary winding of a filament transformer. The load will generally be negligible, but maybe not. How can I determine whether the transformer can handle this? From the gauge and secondary rating I can make a guess how much current the winding is intended to handle, but I don't know if Ohm's law applies here. Example: For a 120VAC transformer with a secondary winding rated at 28VAC/2.8A, is the winding's impedance 10[math]\Omega[/math]? Thanks!

But the annihilation results in the release of the equivalent amount of energy. A concentration of energy can result in a black hole just as a concentration of mass can. If mass quantity [math]m[/math] is sufficient to form a black hole, then (I believe) that the equivalent energy ([math]mc^2[/math]) can also. (See kugelblitz.) So if the matter is turned into energy, it shouldn't matter -- the mass-energy in the black hole remains the same, so it remains a black hole. Nothing's being lost; it's just changing from one form to another. Mass-energy is conserved.

I meant Sun-Earth. Oh, well, it was just a thought. Thanks for the critical analysis of it.

Come, come! The laws of physics as we now understand them.

Not in Earth orbit, no. How about at L1 and L2, though? That should be far enough away for comfort, close enough for control, and far enough to be manoeuvred for timely interception. We're not ready to put them at L3-L5, which would be even better.

Well, at least if we blast into little itty bits we won't have to worry about people claiming global warming isn't a man-made effect..

Precisely what I was trying to find out! Thanks!

I have some 'safety glasses' that I picked up a while ago. The lenses are supposedly polycarbonate. Each lens has the notation "PV Z87+" etched on it, as does the frame, and I'm guessing it has something to do with the limitations of the poly. However, I haven't been able to find any explanatory reference for such notation. On the other hand, it might just be the manufacturer's part number. ("Made in China") Does anyone have a clew what "PV Z87+" might mean on safety glasses? Thanks!

Umph. I remember the cognitive dissonance I experienced upon first learning that a clock in orbit would not keep the same time as an Earthbound one. (Although in retrospect that's obvious, so maybe it was two clocks under different gravitational stresses rather than traveling at different velocities.)

Not exactly -- I was wondering if our eyes move in response to a replayed memory as they did when the memory was recorded. Or is imagined. If I watch something with my focus of interest moving left to right (as my example of a horse race), as I'm replaying it on the inside of my forehead would my eyes possibly track left to right as they did when I watched the original event? Dunno if that's any clearer, but it sounds as though the answer is 'almost certainly not.' I think I ended up here from pondering a segment in What the Bleep Do We Know? which suggested that the cognitive centres can't actually tell whether their input is from external sources or from memory. (Or something like that. I can replay the vid and get the exact remark if desired.)

This may not be the appropriate forum, but.. When someone's thinking, you often see their eyes darting around, but not really registering the external environment. Has anyone ever discovered a correlation between the directions the eyes look and what's being seen internally? As a gross example, if someone were remembering a horse race, might her eyes track from left to right (or vice versa) matching the visual memory being experienced?

'S what I thought. Thanks!

This one has bugged me for a while. Does magnetism actually involve 'lines of force,' along which so many beginner experiment descriptions have iron filings aligning? Or is it an actual non-discrete field effect like gravity?

I really don't know from relativity at all, so I'm still speculating here. However, from Wikipedia: According to Einstein's general theory of relativity, once an event horizon has formed, the type of mass-energy that created it no longer matters. So from this I speculate that the event horizons will intersect, the singularities will be drawn together, and -- if there actually is a distinction between normal- and anti-matter in such a case -- the matter and anti-matter will annihilate each other, and the mass-energy quantity within the event horizon will be represented by energy rather than mass. But from the observer's point of view, the objects would merge into a single, somewhat larger object.

I don't think time dilation would enter into it. If by 'destroyed' you mean that after the collision there'd be zero instead of two black holes.. I don't think so. A black hole is a system from which radiant energy cannot escape, right? (Layman's terms.) Matter plus antimatter results in radiant energy, yes? The [math]m[/math] may have converted to [math]E[/math], but it still can't escape the event horizon. I'm assuming that the gravitational effect would be the same whether the entity were [math]m[/math] or [math]E[/math], which may not be a valid assumption. Merged post follows: Consecutive posts merged Hmm. What if the box in which Schrödinger's cat is ensconced is, in fact, a black hole's event horizon? If we can never open the box, what's the state of the cat? (Just noodling here, triggered by the text at the no-hair link. Ignore as appropriate.)

Speculating here.. I think they'd annihilate each other. With the radiation initially unable to escape the event horizon.. hmm. I think they would turn into a single kugelblitz. All issues of initial approach velocity and rotation aside, of course.

swansont, I didn't mean gravity per se, but (as DH correctly inferred) analogous forces/effects. DH, Excellent. Thanksvery much!

This may be a meaningless question; this level of physics is not my field. (It's also late at night.) However, this just occurred to me: Are there any equivalents at the atomic or elementary particle level for the tidal effects we see from gravity in the macrocosm? Thanks!

How about http://bit.ly/11vQ7a and http://bit.ly/vZJIG ?

I was wondering why ramjets hadn't been mentioned yet. One thing I don't like about lightsails is having to deal with the stellar wind. If the wind was solely composed of electrons, or protons and stripped nuclei, you could deal with it by putting a charge on the sail. (In fact, you might get a little boost from the repulsion.) But it's not -- it's composed of both positively and negatively charged particles, which will stick to the sail and cause all sorts of problems. Well away from the star the issue becomes less of a concern -- but the light pressure is lower out there, too.

I have a flask of ferric chloride which was used to etch some copper -- and, inadvertently, some hardened steel. At this point, I believe the solution contains [ce]FeCl3 + FeCl2 + CuCl2[/ce] I'd like to salvage as much etchant as I can. Is there any way to Remove the cupric chloride? Perhaps by converting it into something that isn't water-soluble and hence will precipitate out? Oxidise the iron(II) chloride back to iron(III) chloride? Thanks!

Well, I'm assuming that there's some sort of scale of reactivity. For instance, that as the NaOH concentration goes up, the ferrous and cupric chlorides won't give up their chlorines at equal rates..? So if everything is in perfect balance, and all of each compound will participate in the reaction, [ mumble ] I'm thinking the end result will be NaCl, iron and copper hydroxides -- and chlorine gas. Um. Merged post follows: Consecutive posts mergedOr maybe not [ce] 7NaOH + FeCl3 + FeCl2 + CuCl2 -> Fe(OH)3 + Fe(OH)2 + Cu(OH)2 + 7NaCl [/ce] Except that ferrous hydroxide isn't particularly persistent, right? So there'll be at least one more reaction before things stabilise. Too bad I can't readily remove the ferrous and cupric chlorides; I'd like to preserve as much of the etchant as possible. Oh well. Merged post follows: Consecutive posts mergedPerhaps this is best asked in the 'practical chemistry' forum.

{Sigh} What should I study in order to determine the probable course of reactions such as this? It's been a long time since my chemistry classes.. Thanks!