The Science Thread

Quote: Nareed

Speaking of free fall, I've two questions that have been nagging me:

1) I'll ask it if you've read Larry Niven's "The Integral Trees."

2) Suppose the Earth was a perfect sphere with its mass evenly distributed. Now suppose it has a hollow center, say 10 meters in diameter. If you were at the exact center, would you experience weight? Wouldn't you be pulled equally in all directions?

Thanks.

(1) I have never read that book.

(2) My understanding is that the gravitational field inside a uniform hollow shell is zero, which supports your suggestion. I think this topic was discussed in another thread a few months back, and someone disagreed with me. I am not sure who it was (weaselman?) or what their claim was. Whoever they were, they were heretics to my Gravity religion, but I ignored them rather than burning them at the stake.

Quote: Nareed

Yeah, no one's ever been burned at the stake, or marched into a gas chamber, because his definition of mass differed from that of the majority. Also no one tries to force others into accepting their moral code because they think they're definition of weight is the only one acceptable.

Get out of here! No seriously, get this garbage onto the rag on religion thread. You do have a point, unlike deluded Christians, science has not burned anyone at the stake or like racisit atheists put people into a gas chamber, but it is my contention that some in the science field still ostracize some of their collegues who do certain types of research. It is part of the human condition that we don't like it when others disagree with us or prick our conscience about something. The negative reaction is not only found in religious history but in modern science. One example may be hiding our continued understanding that life does indeed begin at conception or trying to limit the funding to the amazing reasearch done into the capabilities of adult stem cells.

Force of Gravity = G m1 m2 / r2. You would indeed be weightless inside the earth because m2 (the mass of the earth) is uniformly distributed aroudn you. You would feel no gravity as it is pulling you equally in all directions. At which point, which way is up?

I guess you would feel a slight gravitional force from the moon and the sun.

Quote: Doc

(1) I have never read that book.

Why not? :)

Seriously, here's as brief as I can set up the situation. The novel, and its sequel, are set in a place called the Smoke Ring. This is the thickest portion of a gas torus in orbit around a neutron star. There's a second, yellow star orbiting the neutron star. Ok? The thick part of the gas torus holds enough oxygen at a pressure around that of a mountain top on Earth, so life thrives in many forms. A kind of fallen human civilization lives there (no spoilers!)

Ok, one of the life-forms is a kind of tree about 100 kilometers long from tip to tip, with tufts at each end bending in the direction of the wind (thus looking like integral signs, thus the integral trees).

Now, everywhere on the smoke ring things and people exist in free fall, but on the integral trees there's "gravity" and "weight" (I trust you understand the quotation marks). It grows stronger at the ends and weaker, almost to "zero-g" at the mid-point. Niven explains this as "tides," but he doesn't explain why the tidal effects from the Neutron star should produce "weight."

Help please?

I do highly recommend both books. They're called "The Integral Trees," and "The Smoke Ring." It's Niven's ultimate weird setting, and the man specializes in weird settings.

Thanks for the answer to the other question. I do recall the thread about pouring an ocean through the center of the Earth and out the other side.

Nareed,

I may have to back off my earlier comment about a zero gravitational field inside a hollow shell. My fuzzy memory is that this applies to a "thin" shell, where the thickness of the shell is insignificant compared to the distance you are away from the inner surface (while inside the shell). If the earth were a "thick" shell, say 10 miles thick and you were just barely away from the inner surface, the 10 miles of mass very close to you may exert more gravitational attraction than all of those many tons of mass 8,000 miles away. I'm not sure. I don't (yet) want to reverse my previous position, but I do need to back off it after thinking for a few minutes.

If this thick shell effect is correct, then I'm not sure how to interpret your scenario of a small cavity at the center of the earth. It might still be a zero gravity field, since you would be almost equally close to all of the inner surfaces. Same result but for a slightly different reason, perhaps.

Quote: FrGamble

Get out of here!

But in every "Law and Order" episode I've ever seen, this would be the time when the defense objects and the ADA claims the witness opened the door...

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No seriously, get this garbage onto the rag on religion thread. You do have a point,

Either it's garbage or I have a point. But if you mean for the argument to end, you shouldn't continue it.

Quote:

One example may be hiding our continued understanding that life does indeed begin at conception

Oh, no. life begins long before conception. every mature ovum is alive, as is every mature sperm cell, even those deformed well past the point where they will never get within a centimeter of an ovum. All those cells are alive and can potentially develop, if certain conditions are met, into an independent being, be it a fly, a cat or a human being.

You have to wonder how an omnipotent creator came up with such a shoddy, wasteful design.

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or trying to limit the funding to the amazing reasearch done into the capabilities of adult stem cells.

No one's trying to limit funding for research on adult stem cells. Plenty of people are trying to limit research on fetal ones. Just because one line of research may hold some promise is not a good reason to close off other lines.

Quote: Nareed

Oh, no. life begins long before conception. every mature ovum is alive, as is every mature sperm cell, even those deformed well past the point where they will never get within a centimeter of an ovum. All those cells are alive and can potentially develop, if certain conditions are met, into an independent being, be it a fly, a cat or a human being.

Oh Lord have mercy, why do I keep responding. Contrary to what Monty Python or St. Thomas might say every sperm is NOT sacred. It is only when conception occurs does the human zygote become a unique individual different than the mom or the dad. At conception the developing human embryo is human and given time will become someone like you or me, who are in reality "overgrown embryos".

Quote: Nareed

No one's trying to limit funding for research on adult stem cells. Plenty of people are trying to limit research on fetal ones. Just because one line of research may hold some promise is not a good reason to close off other lines.

Again you are usually right about part of your arguement - just because adult stem cells are so amazing does not neccesarily mean we should not pursue embroynic stem cells. The real reason we should not do research on embryos is because they are human embryos for goodness sake (see above)! We should not kill embryos, or anyone for that matter, in order to do unneccesary and unethical reasearch.

Quote: Nareed

if you mean for the argument to end, you shouldn't continue it.

This time I will give Nareed a pass and maintain Fr. Gamble is the more contentious one. Come on you two, you are hijacking the thread.

Quote: Doc

(1) What does "zero-G" mean?

I will add to the other replies that to be in orbit means to be in this state. So satellites of Earth are such, but also all of us vis a vis the Sun as we orbit it. I think even the solar system vis a vis the galaxy, and so on, but don't quote me on that.

Quote: Nareed

Suppose the Earth was a perfect sphere with its mass evenly distributed. Now suppose it has a hollow center, say 10 meters in diameter. If you were at the exact center, would you experience weight? Wouldn't you be pulled equally in all directions?

In the exact center, the pull is equalized and you have no weight, regardless of thick shell, thin shell, in the thought experiment this generates for me.

Quote: Doc

(2) My understanding is that the gravitational field inside a uniform hollow shell is zero, which supports your suggestion. I think this topic was discussed in another thread a few months back, and someone disagreed with me. I am not sure who it was (weaselman?) or what their claim was. Whoever they were, they were heretics to my Gravity religion, but I ignored them rather than burning them at the stake.

Nope, not me. I agree, that in the center of such sphere the gravity (induced by that sphere) is zero.

Quote: Doc

I may have to back off my earlier comment about a zero gravitational field inside a hollow shell. My fuzzy memory is that this applies to a "thin" shell, where the thickness of the shell is insignificant compared to the distance you are away from the inner surface (while inside the shell).

No, this does not matter. In a hollow sphere, the gravity at any point inside it would be zero. But as long as you are talking about gravity at the center, it does not matter how thick it is, as long as it is spherically symmetric distribution of mass.

Quote: Doc

Yep, from my perspective, my weight is precisely the force that gravity imposes on my mass – nothing to distinguish.

Like I said, that's my problem with it. If nothing else, I think, it is simply inconvenient and confusing to give two names to one thing, while leaving some other thing entirely unnamed.

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I think I agree with this definition but disagree with your interpretation, so let's try another one:

Choose a frame of reference fixed with respect to the surface of the earth, and consider only local problems. In particular, consider the example the Wizard mentioned of travel in an elevator.

Ah, that's why I said I did not like that definition. Reference frames.
When I am talking about weight in this definition, I always assume the reference frame co-moving with the body whose weight is being defined. I think, it is the only reference frame that makes sense to be considered. Granted, you can sensibly define a "weight in another reference frame", but that seems like a completely useless quantity (kinda like a "relativistic mass", albeit somewhat better, because, at least, it is a vector). I can't think of any application of it.

Also, note that the term "local" in that definition is used in differential sense. If you are in an elevator falling down, however close to Earth, your local reference frame is very different from that, fixed at the surface of the Earth.

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The elevator operator hits the button, they start the trip toward the top, and the young lady glances at the display on the scale. It reads 120 lbf. I suspect you are going to say that she then weighs 120 lbf, right? At what rate are she, the elevator, and all of the other occupants accelerating? By my perspective, they are accelerating at 0.2 g upward. Do we agree?

In a reference frame where Earth surface is stationary, yes, 0.2g upward.
In the girl's own reference frame (co-moving with the elevator), there is no acceleration.

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Now suppose the Stratosphere had a super elevator and that the young lady is impressively strong. As the super elevator zooms them upward, she looks down at the scale and sees the display reading 200 lbf. What does she now weigh? (200 lbf from your perspective, right?) At what rate are they accelerating? By my view, they are accelerating at 1 g upward. Do we agree?

With the provisions I mentioned above, yes.

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What force is the scale imposing on the girl's feet? I think we would both agree on 200 lbf upward as the answer to this question, right?

Yes, I agree with that.

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Is gravity still imposing a force on her body? How much? I think it is still 100 lbf downward, do we agree on that?

The gravity is always imposing force on everything (except in the center of a sphere :)). The Earth gravity, yes, about 100lbf.

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If so, what is the net of all forces acting on her body? I think there is a 200 lbf upward force delivered by the scale to her feet and a 100 lbf downward force delivered by the gravitational field for a net force of 100 lbf upward. Do we agree?

Yes, ignoring, the Moon, and the Sun, and Crab nebula, and centrifugal force from Earth rotation, and air buoyancy of course :)

Quote:

OK, now look at the ISO definition. Her weight is defined as the force that gives her body an acceleration equal to the local acceleration in free fall; i.e., an acceleration of 1 g.
We have changed the direction from fall to climb, but I believe that there is a net upward force of 100 lbf giving her an acceleration equal to 1 g upward. By the definition, doesn't that mean that her weight is 100 lbf rather than the 200 lbf that the scale reads?

Ah, no ... They are talking about local acceleration (remember, "local" in differential sense).
In her own reference frame, the free-fall acceleration is 2g, not 1g. If she held a "test body" (an ice cube or a grain of salt) in her hand, and let go off it, it would accelerate towards the elevator floor at the rate of 2g. That is the local free fall acceleration.

Quote: Nareed

Now, everywhere on the smoke ring things and people exist in free fall, but on the integral trees there's "gravity" and "weight" (I trust you understand the quotation marks). It grows stronger at the ends and weaker, almost to "zero-g" at the mid-point. Niven explains this as "tides," but he doesn't explain why the tidal effects from the Neutron star should produce "weight."

I can't think of anything that could relate the trees specifically to the star.
Perhaps, the gravity that book refers to is induced by the trees themselves, not the star. That would also explain why it is stronger at the ends, and zero in the middle (same effect as center of the sphere).

Note, that in order to produce significant gravitational force, those trees would have to be extremely dense. Given that high density, and the irregular (non-spherical) shape, one would indeed expect some extreme tidal effects in its vicinity (in particular, standing in the middle of the "tree", you would not exactly feel "zero gravity", but rather a pull on both sides of your body in each direction).

Quote: Doc

My perspective: I view "weight" to be the force which a mass experiences due to the local gravitational field; weight may be calculated by multiplying mass times the acceleration of gravity. This force may or may not be counterbalanced. If not, then the body will accelerate, perhaps in totally free fall. Even in that case, the body has the same weight, provided its mass and the gravitational field have not changed. If the gravitational force on the mass is completely counterbalanced by an upward force, then there will be no acceleration (Newton's first law).

weaselman's perspective (I think): Weight is the force that a mass imposes on its support structure when the mass is acted upon by a gravitational field and there is no acceleration. If the object is in free fall, it has no weight.

In a different thread, we came danged close to getting into an argument over this before I realized that we just use the term "weight" to describe different forces. If there were a problem with gravitational attraction, masses, and maybe even some acceleration, I suspect that weaselman and I would calculate the same answer, provided we were careful not to use the term "weight" along the way and get back into a dispute about language rather than science. Conclusion: weaselman, I think you have your act together on this stuff, even if I disagree about how to use this one term.

If you are referring to my comical post about how much the sun weighs, I'll step out of the character that started that thread to say that the choice of "weigh" over "mass of" was intentional, to make the question sound silly to the science minded.

Quote: weaselman

I can't think of anything that could relate the trees specifically to the star.

That's what's been driving me up a wall ever since I read the novels. I know what tides are, more or less, and I know tidal action gets extreme with a sharp gravitational gradient, especially one that's as strong as a neutron's star. Of course it doens't matter when reading the novels. I just accept "tide = gravity" and keep on reading.

Quote:

Perhaps, the gravity that book refers to is induced by the trees themselves, not the star. That would also explain why it is stronger at the ends, and zero in the middle (same effect as center of the sphere).

Note, that in order to produce significant gravitational force, those trees would have to be extremely dense.

I thought of that. But 1) the trees are made of regular wood. Near the beginning one of them gets eaten apart by bugs, for example. And throughout the novels people make use of the bark and the wood. 2) Niven tends to be very precise in his terms. If he said "tide," and he did, then he means "tide = gravity."

What galls me is the lack of explanation. In antoher of his novels, Ringworld, he goes to great lengths to explain the mechanics of that peculiar construct.

Quote: FrGamble

Oh Lord have mercy, why do I keep responding.

Because you can no more passively sanction any of my arguments than I can passively sanction yours? Just a guess.

I will let it go, for now, because we are dragging the thread way off topic (though abortion and the limits of life are fields for science).

Except:

Quote:

We should not kill embryos, or anyone for that matter, in order to do unneccesary and unethical reasearch.

Nice package deal.

I agree we should not kill embryos for research. That is, we should not conceive human embryos, either naturally or in-vitro, for the sole purpose of producing experimental stocks. But we should also not waste such embryos as are 1) already dead or 2) destined to be destroyed.

If a woman has an abortion or a miscarriage and wants to donate the embryo to science, she should ahve that right. if a couple, or a woman, has excess embryos in a fertility clinic and can't make use of them, they should ahve the right to donate them, or sell them, for research.

And there's nothing unethical or unnecessary about that.

Tide is caused by the force of gravity pulling on a fluid. You see tides on earth because there is a different force of gravity on water on different points of the earth. This can be measured. The two primary forces of tide are the moon and earth.

The mass of the earth is 5.9742 x 10^24kg = M1
The mass of the moon is 7.36 x 10^22 kg = M2
The mass of the sun is 1.98892 x 10^30kg = M3
The radius of the earth is 6378100 meters = r
The gravitational constant is 6.673 x 10^11 m^3 kg^-1 s^-2
The distance from the moon to the earth varies between 362,570,000 m and 405,410,000 m with a semi major axis of 384,399,000 m = D
The distance from the sun to the earth averages 149,597,870,700 m which varies by approximately 1.3% in either direction. = S

The force of gravity of the moon on the earth at the closest point to the moon can be expressed as F = (G M1 M2) / ((D-r)^2)
The force of gravity of the moon on the earth at the furthest point to the moon and can be expressed as F = (G M1 M2( / ((D+r)^2)

The difference in pull from one side of the earth to the other by the moon is approximately 1.319 x 10^19 Newtons.

The difference in pull from one side of the earth to the opposite side by the sun is approximately 6.042 x 10^18 Newtons (about 46% of the moon's influence).

Tides are caused by the gradient in gravitation from one side of the planet to the other. The greatest high tides are when the moon is new and the force of gravity are all on the same side. You would think the opposite would be true for a full moon, but that isn't the case. Why?

Quote: boymimbo

Tide is caused by the force of gravity pulling on a fluid.

Pulling on everything. It's just more easily noticeable in large fluid bodies like oceans.

That, by the way, is gall on my side, since I can't explain tides very well at all, and I understood only a little of what you said later on. I'm like that sometimes ;)

Quote: boymimbo

Tides are caused by the gradient in gravitation from one side of the planet to the other. The greatest high tides are when the moon is new and the force of gravity are all on the same side. You would think the opposite would be true for a full moon, but that isn't the case. Why?

Because of the symmetry. The tidal force from the Sun (or the moon) is (almost) the same on the side of the Earth facing the Sun, as it is on the opposite (antipodal) side. Full moon occurs when the Sun is on the opposite side of Earth from the Sun, so, Sun's tidal force is strongest, just like during the new moon phase.
This condition (conjunction or opposition of the moon) is also (not quite correctly) sometimes called syzygy.

Nareed is correct, it is not just water that is affected. Earth's core actually displaces several centimetres between highest and lowest tides, while the contours of atmospheric surface moves kilometers up and down.

Gravitational forces act on everything. They're just more pronounced in oceans and in fluids.

Well, we seem to have three or four "science" conversations going on at once in this thread, with one looking a lot more like a religion conversation. This post is intended as a continuation of the discussion that weaselman and I have been having on the meaning of "weight."

I think just maybe I have come up with a relevant thought about the source of our disagreement. I think that we always agree on the weight of an object (at least numerically, if not in the definition) so long as there is no acceleration. Every time that there is acceleration, we have a different answer. With your latest (I think) post, I see that this difference may be due to your using a reference frame that moves with the mass and therefore is accelerating itself.

Some people like to perform analyses using a reference system that is "fixed with respect to distant stars"; i.e., a non-accelerating system in almost any sense. In most any problem I deal with, it is reasonably acceptable to use a system fixed with respect to the surface of the earth. I stated this when I started the example of the elevator, along with a restriction that I would only consider "local" problems. By that I meant problems in which the motion of the earth (rotational, orbital, galactic drift, etc.) and variations in the gravitational field do not have a significant affect on the analysis.

Some months ago, maybe even a year ago, there was a thread around here discussing the Coriolis effect, and we talked about such things as two people riding a carousel and trying to toss a ball to one another. One way of looking at such a problem is to use a frame of reference that rotates with the carousel. Such a frame of reference is accelerating due to its rotation. In solving problems in that frame of reference, Newton's laws of motion take on much more complex expressions. Yes, I suppose the second law is still "F=ma", but "a" gets much more complex and includes such terms as the Coriolis acceleration.

Suppose that we wanted to analyze motion of the people on the carousel or the ball being tossed between them using a frame of reference that not only rotated but rotated with a varying angular velocity (well known and described by some mathematical expression). Suppose that we also let this frame of reference move at varying velocities with respect to the Cartesian axes. Then, just for jollies, suppose we let the frame of reference rotate at varying rates about each of the Cartesian axes. I still assume that each of these translations and rotations are well described by mathematical expressions.

With that frame of reference, we could analyze the motion of the people and the ball, but Newton's laws of motion would be incredibly complex. Yes, it would still be "F=ma", but "a" would be mind-warpingly complex. Suppose with that frame of reference we wanted to analyze a boulder near the carousel and stationary with respect to the surface of the earth. The boulder's motion in this on-the-move reference system would be very complex to describe, but Newton's laws of motion would have to be written to show that the net force acting on the boulder is zero. Not really the easiest way to analyze it.

Now once you start analyzing FrGamble's friend (you remember her, the teenage girl with the burned hand who likes to ride the elevator at the Stratosphere?) and you let the frame of reference accelerate with her up the shaft, then you really need to re-write Newton's laws so that they work in that frame of reference. It's not as complex a set of equations as are required for the absurd frame of reference I described above, but a different set of equations is still necessary, and the second law would have "surprising" terms somewhat analogous to the Coriolis acceleration.

For example, suppose you wanted to use that frame of reference accelerating up with the Stratosphere elevator to analyze the wino who is passed out on the sidewalk behind the strip club on the next street. He would be seen as accelerating downward in that frame of reference. Newton's laws of motion would have to be written in a manner that assured that the net forces on the wino compute to zero, in spite of his apparent acceleration.

While I think our "disagreement" could have been resolved by just saying that we have different definitions for the term "weight", once you introduced the ISO definition with which I agree, I felt a need to find some other explanation. I think that explanation is that, in the case of masses that are accelerating, you are using an accelerating frame of reference but have not altered your expressions for Newton's laws of motion. If that is the case, then maybe we do disagree on a point of science rather than on language. What do you think?

Doc, I understand why different frames of reference can be more or less useful under different conditions :)
There are two reasons I can name though that make the girl's frame of reference in your example "preferred" as compared to the Earth surface frame of reference:

1. As I said before, I don't see very much use of discussing "the weight of a body" in an abstract reference frame, not related to the body itself. It is generally considered a "taboo" in physics to consider quantities that cannot be measured. If a physics encyclopaedia was not readily available, and the girl in elevator needed to urgently determine her weight, she would have to either step on the scale or use a test body to determine free fall acceleration (provided that she already knew or had a way to determine her own mass). Either method would result in her measuring her weight in her own reference frame.

2. Unlike your example with the carousel, the co-moving reference frame actually simplifies calculations in this case because it allows to exclude gravity (or rather, to combine gravity with the "inertia" from the accelerating elevator into a single force).

Also, if the elevator was free falling, there would be a third reason - it's reference frame would be inertial, meaning, locally equivalent in every single respect to that of an elevator floating freely in intergalactic space, without any gravitational influence whatsoever. Now, since the two situations are totally and completely indistinguishable in any way, I fail to see any rational reason for considering the girl's weight to be the only thing different about those two cases.

weaselman, perhaps it would be useful for me to understand how you would analyze a system of masses that are are accelerating with respect to each other. Say one ball lying on the basketball court and another bouncing nearby. Or two balls involved in a collision. What would your frame of reference be for such systems? To analyze the system, you must consider all of the masses, and there must be only one frame of reference.

Well, that depends on how exactly the conditions are formulated, and what are the questions to be answered. Sometimes, it may be convenient to use a frame, associated with one of the bodies, and other times a fixed reference frame where both bodies are moving is better.

The bottom line is I cannot imagine a situation where it would be useful to operate a specific quantity of a body weight, calculated in a reference frame different from the one co-moving with that body. Can you think of a such an example?

Quote: weaselman

The bottom line is I cannot imagine a situation where it would be useful to operate a specific quantity of a body weight, calculated in a reference frame different from the one co-moving with that body. Can you think of a such an example?

Side note: I'm not sure what you mean by "to operate a specific quantity of a body weight", but assuming that doesn't get in our way, here is my answer:

Sure. I use a frame of reference fixed with the surface of the earth and find it convenient for almost every problem I encounter. This applies to static systems, systems moving at constant velocity, and systems that are accelerating. On some problems that involve something moving at a constant velocity, I choose a frame of reference moving at that velocity. An example would be a problem where I am traveling in a constant-speed car or train and want to consider primarily those things that are traveling with that vehicle, such as two children tossing a ball to each other in the back seat. I certainly wouldn't try to use a frame of reference moving with the ball from child to child.

Occasionally, there is a problem that practically demands that I use a rotating frame of reference, but that step in itself adds a lot of complications, so I only use it if I can't reasonably address the problem with a fixed frame of reference. Of course, this brings us back to the point that you and I may differ on what we mean by the term "weight." The possible language issue might arise again.

Here is one of the reasons why I have difficulty with your frame-always-moving-with-the-mass approach. Forces acting on masses should not be dependent upon the observer. If I observe the girl on the elevator from a stationary frame of reference, you observe her from a linearly-accelerating frame of reference moving with the elevator, the Wizard observes her from a frame of reference anchored to a rotating carousel in a nearby park, and Nareed observes her from a frame of reference moving wildly with the roller coaster at NYNY, we should all conclude the same things about her weight, the force of gravity on her body, the force of the scale against her feet, the force of the scale against the floor of the elevator, the tension in the cable pulling the elevator upward, etc. Fortunately for me, using the fixed frame of reference allows me to use very simple expressions for Newton's laws of motion, while you need to adjust the equations for the linear acceleration of your frame, the Wizard needs to make even more adjustments including centripetal and Coriolis accelerations, and Nareed needs to develop some outrageously complex expressions for Newton's laws because of the way his frame of reference is accelerating all over the place.

Another reason I have difficulty with the frame moving with the mass is the one I mentioned before: if there are multiple masses moving independently, you have to decide which one to tie your frame to. If your frame of reference is moving with the child in the back seat, can you readily figure both the weight of the child and the weight of the ball that he just tossed to his sister? If your frame were instead moving with the ball, would you still compute the same weights for the child and the ball? If not, then you must have some error, because the force is not dependent upon the observer. For my part, I find it quite convenient to find their weights by just multiplying the mass of each by the local acceleration of gravity.

Quote: Wizard

I am behind you 100% on this Doc.

Well then, aside from no one pointing out in any way where/how Doc didn't misconstrue that simple sentence of mine, i must say that one should be careful of whom one just gets "behind by 100%". What if that sentence at-question comes to be explained for even the lazy to make proper sense of. (Not that only two(?) posters in Doc's defence appear to be that great of a hurdle anyway.)

Quote: Wizard

It pains me to see the treatment Garnabby is giving you, which is rude and disrespectful.

How about after being quickly "called" just about "everything in the book" by Doc. How about an example in which i "called" him something? Like troll, JL, "pisser", et at?

One last time, i did compose and submit the following.

Quote: Garnabby

Salt quickly breaks down ice, so that heat which was gradually removed to produce ice is quickly re-introduced back into the water.

Let's parse that sentence a bit, shall we. The first part, "Salt quickly breaks down the ice (used by FrGamble's student)." Straight-forward enough? Not a matter of ice which was too-cold to react with the sort of salt applied, if some student did achieve that "burn". Next, "so that (sort of, degree/type of,) heat which was gradually removed (from water) to produce ice" doesn't mean "that heat" which is "salt quickly breaks down the ice"... that first phrase being not even a grammatical matter of heat per se. And there would have to be a comma before the "which" to even suggest this. Finally, "is quickly re-introduced back into the water" because it was "removed (from water)" beforehand, obviously to make the ice... and generally by some "gradual" process.

I most-certainly didn't write anything like the following.

Quote: Doc

It appears from your posts that you believe that adding salt to the ice in an attempt to melt it will result in heat being released into the water.

What am i missing? Otherwise actually, i think my reply neatly summed up the entire discussion which followed of "the topic".

P.S. Sorry if i didn't offend anyone.

Quote: Doc

An example would be a problem where I am traveling in a constant-speed car or train and want to consider primarily those things that are traveling with that vehicle, such as two children tossing a ball to each other in the back seat. I certainly wouldn't try to use a frame of reference moving with the ball from child to child.

That's not the kind of example I was asking for. I am looking for an example of a problem where the notion of weight in a different reference frame would be useful.
Like the girl in the elevator for instance ... what particular question does knowing that she weighs 100 lbf in the Earth reference frame help to answer?

If this was not an elevator, but, say, a spaceship taking off, knowing that a 200lbm pilot weighs 600lbf is an important piece of information - it tells you how the pilot actually feels. Knowing that he weighs 200lbf "in Earth reference frame" on the other hand is, completely redundant (we knew that as soon as we knew his mass), and entirely useless info.

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Here is one of the reasons why I have difficulty with your frame-always-moving-with-the-mass approach.

Not "always". Just when talking about weight.

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Forces acting on masses should not be dependent upon the observer.

This is actually exactly my point!

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If I observe the girl on the elevator from a stationary frame of reference, you observe her from a linearly-accelerating frame of reference moving with the elevator, the Wizard observes her from a frame of reference anchored to a rotating carousel in a nearby park, and Nareed observes her from a frame of reference moving wildly with the roller coaster at NYNY, we should all conclude the same things about her weight, the force of gravity on her body,

I totally agree with this statement (and that is exactly why I keep saying that introducing a notion of a reference frame into weight calculations is a very bad idea).
What I disagree with is the idea that weight and force of gravity are always the same. If that was the case, why in the world would we need two different terms for them?

Quote:

Another reason I have difficulty with the frame moving with the mass is the one I mentioned before: if there are multiple masses moving independently, you have to decide which one to tie your frame to.

Not for determining their weights. I would measure the weight of each in its own reference frame (because I believe that is the only reference frame in which "weight" actually means anything useful).
Or, better yet, I would use a better definition of weight, one that does not depend on the reference frame to do away with this problem once and for all. That is exactly why I said I did not like ISO's definition, if you remember - dependence on the reference frame is really confusing and really useless here.

Quote:

If your frame of reference is moving with the child in the back seat, can you readily figure both the weight of the child and the weight of the ball that he just tossed to his sister?

Actually, yeah, and fairly easily. The weight of the child is his mass times g, and the weight of the ball is zero.

Quote:

For my part, I find it quite convenient to find their weights by just multiplying the mass of each by the local acceleration of gravity.

Except, those are gravitational forces, not weights. I know, you insist that those are the same thing. But I in turn insist, that it does not make any sense to assign two specific different terms to mean exactly the same thing.

Quote: Garnabby

P.S. Sorry if i didn't offend anyone.

Oh, I suspect you were reasonably successful at that, so no need to apologize.

Just in case this is a typo and you really meant to apologize if you did offend anyone, let's start over and try to do this without the animosity.

Quote: Garnabby

Quote: Garnabby

Salt quickly breaks down ice, so that heat which was gradually removed to produce ice is quickly re-introduced back into the water.

Let's parse that sentence a bit, shall we. The first part, "Salt quickly breaks down the ice (used by FrGamble's student)." Straight-forward enough? Not a matter of ice which was too-cold to react with the sort of salt applied, if some student did achieve that "burn". Next, "so that (sort of, degree/type of,) heat which was gradually removed (from water) to produce ice" doesn't mean "that heat" which is "salt quickly breaks down the ice"... that first phrase being not even a grammatical matter of heat per se. And there would have to be a comma before the "which" to even suggest this. Finally, "is quickly re-introduced back into the water" because it was "removed (from water)" beforehand, obviously to make the ice... and generally by some "gradual" process.

Well, I confess I had a little trouble following that paragraph of parsing, but I think I followed enough of it to see a couple of places where a miscommunication may have occurred.

Lest we have more misunderstanding, I don't think that the salt reacts with the ice at all -- it is strictly a mechanical process of entering solution. Now perhaps some chemists consider the ionization of the salt and the affinity of the Cl^- and Na⁺ ions to the H⁺ and OH^- ions in the solution to be a "reaction", but I'm not a chemist, so I don't really know how that is viewed these days. In my chemistry naivety, I think of a reaction as something that creates a different set of chemical compounds.

The first possible miscommunication I see is contained in the words, "... so that heat ...." One possible interpretation, and the one I originally made, was that the words "so that" served as a two-word subordinate conjunction equivalent to "... with the result being ..." After reading Granabby's parsing, it seems he meant the single word "so" as a coordinating conjunction and the word "that" as a specifying adjective: that heat. Immediately following, there is the word "which", and in the parsing Granabby seems to indicate at least partial understanding that using "which" to introduce a non-restrictive clause should involve a preceding comma. Unfortunately, when introducing a restrictive clause (without the comma), the proper word is "that" not "which". I think I frequently make that error myself. Note: if we're going to get into parsing postings to this level, we really need pacomartin here to provide continuous grammar lessons, and I don't think most of us could handle it anyway. :-)

Even though there may have been some misunderstanding of the grammar there, I don't think there was any confusion about the intent: heat had previously been removed gradually in the formation of the ice.

The much more important miscommunication lies in where the heat was added/released/re-introduced/etc. when the ice is melted.

I think most of the posters who discussed the melting of the ice tried to be consistent in using "ice" to refer to the solid phase and "water" to refer to the liquid phase. When Granabby indicated that heat (previously removed to form ice), "is quickly re-introduced back into the water", it certainly appears that he is referring to adding/releasing/introducing heat to the liquid phase material. Combining his entire sentence made it appear that he intended to claim that the melting of the solid ice to form liquid water somehow added heat to that (liquid) water. That is the way I read it, and it is the way I still read the original wording, even though the statement was odd/false enough that I began my initial response with a confused, "Uh..., no." If the intent was to say that melting involved heat being introduced into the solid ice in order to melt it (a very correct statement), then confusion could have been avoided completely by maintaining consistency and referring to the solid as "ice" and the liquid as "water", rather than suggesting that heat is re-introduced to the water (?) to melt it.

From my initial comment, I tried to be clear that I was interpreting Granabby's post as saying that heat was introduced to the (liquid) water. It would have been a simple matter if anyone had replied to say that Granabby's intent was to say that heat was introduced to the solid phase of the water. I don't think such such a post ever appeared.

The result: Granabby took offense at my reply ("How stupid do you think I am?"), and I got the impression that he was trying to start an argument.

Less harm done here than in a lot of this forum's threads. I think I am glad that I never read any of the religion threads.

TOPIC: The "Infinite" Battery

Back in my hyper lazy days, I discovered that by rubbing a battery's terminals, you could get some extra use out of it. It typically only works in very low draw devices such as a TV remote, although just yesterday I was able to resurrect my cell phone for a few final texts by doing this.

My question is why? I suspect it's just a case of the oils of your skin providing better conductivity, but then again, aren't the metals used in these areas used for their superior conductivity? And isn't metal a prime conductor?

I have a remote in my man cave that's had "dead batteries" for years. I don't remember how many, but it's a dvd remote for the ORIGINAL Xbox so it's been quite a long time. Every time they die I always happen to be busy doing man cave stuff and can't be bothered to get up, so I pop em out, give em a rub, and I'm back in business. Go ahead and try it. Next time you're beer'd up flipping between 3 different football games and your batteries die, to hell with getting up. Stay in that recliner and just give 'em a rub =) Seems kind of queer that this works, so I bring it here for discussion. How can I get years of use out of a spent battery?

Quote: Face

TOPIC: The "Infinite" Battery

My question is why?

A battery is essentially a chemical reaction where the electrons pass from the negative to the positive through a conductor. This especially applies to a car battery too. If you discharge a battery quickly and fully, then you've exhausted the chemicals of their spare electrons that are closest to the conducting surface. It takes a little time for the unused part of the battery chemicals to even out with the used part. So after even a few minutes, a fully discharged battery will appear to come back to life, if only for a few fleeting moments.

I went looking for a link to the article where i read this but I can't find it.

Quote: s2dbaker

A battery is essentially a chemical reaction where the electrons pass from the negative to the positive through a conductor. This especially applies to a car battery too. If you discharge a battery quickly and fully, then you've exhausted the chemicals of their spare electrons that are closest to the conducting surface. It takes a little time for the unused part of the battery chemicals to even out with the used part. So after even a few minutes, a fully discharged battery will appear to come back to life, if only for a few fleeting moments.

I went looking for a link to the article where i read this but I can't find it.

I don't argue with the science, but I don't think that's it. We've probably all noticed the above if your car wouldn't start. You crank and crank and it gets slower and slower until the solenoid just ticks. You stop for a while, try it again, and it cranks again...a little bit. I think that's what you're describing.

But in my example, it's not a quick discharge, nor is time a factor. If I leave them alone for any amount of time, they'll be just as dead as when they died. Take em out and put em back in, still dead. Switch battery order, still dead (I've played with this idea some ;)) Only by rubbing both ends, just a quick, 2 stroke thumb rub, will they work, and they'll continue to work for some time after. Sometimes a few hours, the ones I just rubbed were rubbed 5 days ago and they're still working. (And to clarify, this is only in low draw devices, like a TV remote. I highly doubt it would work in a car battery, and I know it doesn't work for your typical "AA" powered childrens toy)

I just thought it was curious and worth discussing. Hopefully someone will try it and confirm. Even more hopefully someone will try it and fail, so I can continue thinking I have mystical thumbs made entirely of magic ;)

I think my only input on this topic is that I can frequently get more juice out of a battery (anything from AAA to one from a car) by cleaning the terminals a little. There is often a buildup on them that increases the electrical resistance of the circuit. Usually, I have to do a little scraping, with a pocket knife or something, but you may be experiencing a similar phenomenon where just a finger wipe does the trick.

So many ads at dubious internet sites say something like "learn this simple trick that THE XYZ's don't want you to know!". Face, I'll have to say this is one of them and I'll have to try it. I spend a lot of time in the Man-Cave too.

Quote: odiousgambit

So many ads at dubious internet sites say something like "learn this simple trick that THE XYZ's don't want you to know!". Face, I'll have to say this is one of them and I'll have to try it. I spend a lot of time in the Man-Cave too.

Rubbing terminals?

Electronic devices require a certain amount of current to operate and they draw that current from the battery. It's either an on or off thing. In the case of a TV remote, two things are happening. First, the current has to be able to operate your buttons and have enough current available to process that press of a button, and then, the remote has to send that signal to your TV or cable box. The sending of that signal is what draws the most power, and it's a direct draw on the battery, meaning that the battery will send up to the maximum power that the remote calls for.

Rubbing the terminals of your battery indeed reduces resistance which in turn maximimes the signal. It also warms the end of the battery which increases conductivity. I would also try shaking that battery. Anything that will make the chemical reaction more amenable will have an effect. Your battery stops working because there is no fuel available to complete the circuit.

I understand that the shelf life of alkaline cells is increased if they are put in the fridge or freezer, but if heat increases conductivity, why do "superconductors" have to be near absolute zero?

Are the batteries rechargeable? Perhaps static discharge from the dry air in the basement + friction is powering up the cells?

Quote: Doc

I think my only input on this topic is that I can frequently get more juice out of a battery (anything from AAA to one from a car) by cleaning the terminals a little. There is often a buildup on them that increases the electrical resistance of the circuit. Usually, I have to do a little scraping, with a pocket knife or something, but you may be experiencing a similar phenomenon where just a finger wipe does the trick.

In life I've had a number of little mysteries brighten a random day. As I've aged, little by little, they get explained and I must admit, I'm slightly saddened by the loss of the magic. This is one of the last. I will test your theory by wiping with something neutral next time they "die", like a clean cotton swab. I really hope it doesn't work ;)

Quote: Ayecarumba

I understand that the shelf life of alkaline cells is increased if they are put in the fridge or freezer, but if heat increases conductivity, why do "superconductors" have to be near absolute zero?

Are the batteries rechargeable? Perhaps static discharge from the dry air in the basement + friction is powering up the cells?

These are not rechargable (I save the recharges for high draw stuff like Xbox controllers or my boys firetrucks). They're just typical alkaline batteries of various quality (sometimes Duracell, sometimes just generic ones that come included with a childrens toy). I don't perform any tricks on them whatsoever other than a quick rub, which makes me uncertain of whether it's the heat that affects them. Like I said, I've tried simply taking them out and switching their order, which likewise causes them to contact my skin and heat up, with no effect. And the rubbing is neither vigorous nor lengthy. You know the hand sign for "money"? The quick rubbing back and forth of your index finger and thumb? Just like that, real short, real quick, with very little pressure.

Also, they keep working well after they would have cooled. I think some more testing is in order. I'll try the solutions offered above and report back.

This is one of those situations where taking a measurement radically affects the thing being measured. I would say hook up a volt meter pre and post rub, but the draw by the meter measuring it post-rub could use up any juice.

Okay, some more free time to properly respond to this matter again.

First, it's Garnabby; not "Granabby".

Quote: Doc

Well, I confess I had a little trouble following that paragraph of parsing, but I think I followed enough of it to see a couple of places where a miscommunication may have occurred.

Lest we have more misunderstanding, I don't think that the salt reacts with the ice at all -- it is strictly a mechanical process of entering solution. Now perhaps some chemists consider the ionization of the salt and the affinity of the Cl^- and Na⁺ ions to the H⁺ and OH^- ions in the solution to be a "reaction", but I'm not a chemist, so I don't really know how that is viewed these days. In my chemistry naivety, I think of a reaction as something that creates a different set of chemical compounds.

The first possible miscommunication I see is contained in the words, "... so that heat ...." One possible interpretation, and the one I originally made, was that the words "so that" served as a two-word subordinate conjunction equivalent to "... with the result being ..." After reading Granabby's parsing, it seems he meant the single word "so" as a coordinating conjunction and the word "that" as a specifying adjective: that heat. Immediately following, there is the word "which", and in the parsing Granabby seems to indicate at least partial understanding that using "which" to introduce a non-restrictive clause should involve a preceding comma. Unfortunately, when introducing a restrictive clause (without the comma), the proper word is "that" not "which". I think I frequently make that error myself. Note: if we're going to get into parsing postings to this level, we really need pacomartin here to provide continuous grammar lessons, and I don't think most of us could handle it anyway. :-)

Second, at least please allow me (and others) the possibly-intentional simple convenience of using the word "which" in each of the above-noted types of clause. I think that, as you pointed out, there're already enough versions of that 'that'. And suffice it to say, i had thought of posting up similar links, but, really, to which end. What else is there to add? It's the comma that "does the work" in such clauses; and, as you perhaps eventually concluded to anyway. Careful readers shouldn't, by definition, require the redundant "error checking" stuff.

Anyway, at http://www.getitwriteonline.com/archive/103103WhichThat.htm , we find out that, "Merriam-Webster's Collegiate Dictionary (10th edition), regarded by most writers as the authority on such matters, tells us that it is now common for which to be used with either kind of clause, while that must be used only for restrictive clauses. In fact, though, careful writers continue to make the distinction we describe above. Attorneys are taught to use which for nonrestrictive clauses and that for restrictive clauses so as not to cause a misreading in legal documents. It seems just as important that we work to avoid misreadings in all writing, not only in situations when a legal ruling might be at stake."

Third, from a rather-old science thread, at http://www.madsci.org/posts/archives/1997-08/867417023.Ch.r.html , Richard Oldroyd, Post-doc/Fellow Davy-Faraday Research Laboratory, concluded, "One thing that should also be remembered is that solids can react together, it is just that the reactions between them are very slow. This stems from the fact that only the surfaces in contact with each other can begin to react, and there is often a large "lattice energy" barrier to overcome, i.e. energy is required to break up the crystalline lattices of the reacting solids."

I, myself, am not a chemist by trade... but what else would you call it, in general, if not a reaction? I had not hoped for this (or other such bits) to continue to become new, off-topic "fodder". I'm not a lot of other things by trade either, so nor would i lightly "throw around" words like "paradoxically", eg. (That's a hard one to back up in our reality.)

Interestingly, he points out also, "There are several other factors involved, e.g. some heat is generated when the salt dissolves which also contributes to the melting of the ice."

Quote: Doc

Combining his entire sentence made it appear that he intended to claim that the melting of the solid ice to form liquid water somehow added heat to that (liquid) water.

Four, we're not discussing all of this "in a vacuum". If the ice in question was supposedly pressed against the skin, then the latter is the obvious and dominant source of that heat, in any event.

Quote: Doc

The result: Granabby took offense at my reply ("How stupid do you think I am?"), and I got the impression that he was trying to start an argument.

Hardly, because that was a simple question meant to cause you to re-think your position, given the normal iq, or some past posts of mine. Even those consistently grammatically-nuanced religious ones... in which some of us are confident enough in what we do to take our own slight literary liberties with the language. That's how it evolves, like every thing else.

Quote: Doc

Oh, I suspect you were reasonably successful at that, so no need to apologize.

I was kidding, right? Mostly in reference to that tacit-clique thing found on such message-boards, and directed at the less-frequent posters taking exception with the more-frequent ones.

And no matter how hard we want things to be otherwise, "Sometimes, a cigar is only a cigar." Cunning ain't required on an internet gambling message-board, to "stir things up".

Garnabby, four words for you: eschew obfuscation, espouse elucidation.

boymimbo,Ayecarambba Heating a conductor reduces conductivity (that's why super-conductors need to be super-cooled). The battery is a different beast though, heating it might indeed increase the electrical output by exciting the molecules, and thus speeding up the chemical reaction going inside. The effect is very slight though. I doubt you would notice any effect from simply holding it in your hand.

Face, like Doc says, yes, nickel, from which the terminals are usually made is a pretty good conductor, but as time goes, it tends to oxidize. Especially when being subjected to electrical current. Oxides forming on the surface reduce conductivity, so that at some point, there is not enough power left in the depleted battery to overcome the resistance and output enough voltage. By rubbing it with your finger, you destroy the oxide film thus restoring conductivity, and allowing the flow to resume. The oils on your skin help too, as they are very conductive. Rubbing with a plain cloth instead should work too, but the effect will be smaller.

Oh, let's try smething mnore important: i'm in need of some coherent, or plausible-sounding, technobabble :)

Here's the situation. I'm doing a story in which a character accidentally (of course) winds up in a parallel universe. Such stories are nothing new, going all the way back at least to "Sideways In Time" many decades ago, series like H. Beam Piper's "Paratime" stories, and made popular by Star Trek all the way back in the sixties.

Anyway, a feature in many such stories is the implication that there are an indefinite number of universes available (Larry Niven used this notion to do his "alternate timeline story to end all alternate timeline stories"). For the purposes of my story two universes are plenty, and bringing up more would only be a distraction. But I do want to acknowledge the fact (!) that other universes exist.

So I'm taking a page from Piper and having another character ask "Are we certain we're returning her to her original universe?" Naturally they are, but here I need something to explain how they're certain. In a Trek episode Geordi came up with a "quantum resonance frequency" that is unique for each universe. Not bad, but the fans nitpicked that like you wouldn't believe.

Any ideas? It doesn't have to be realistic, just seem or sound something other than utterly ridiculous.

Thanks!

A begrudging "thank you", weaselman. So ends the magic of my childhood =p. Just kidding of course, I asked and am appreciative of the answer. But I'm still going to tell people I have magic thumbs.

Quote: Nareed

Oh, let's try smething mnore important: i'm in need of some coherent, or plausible-sounding, technobabble :)

Here's the situation. I'm doing a story in which a character accidentally (of course) winds up in a parallel universe. Such stories are nothing new, going all the way back at least to "Sideways In Time" many decades ago, series like H. Beam Piper's "Paratime" stories, and made popular by Star Trek all the way back in the sixties.

Anyway, a feature in many such stories is the implication that there are an indefinite number of universes available (Larry Niven used this notion to do his "alternate timeline story to end all alternate timeline stories"). For the purposes of my story two universes are plenty, and bringing up more would only be a distraction. But I do want to acknowledge the fact (!) that other universes exist.

So I'm taking a page from Piper and having another character ask "Are we certain we're returning her to her original universe?" Naturally they are, but here I need something to explain how they're certain. In a Trek episode Geordi came up with a "quantum resonance frequency" that is unique for each universe. Not bad, but the fans nitpicked that like you wouldn't believe.

Any ideas? It doesn't have to be realistic, just seem or sound something other than utterly ridiculous.

Thanks!

"More important"? Pishaw! What is more important than keeping a football fan in reclination while observing all of his fantasy football team updates, as opposed to the maddening hunt for fresh AA's? ;)

Your question is beyond my capabilities, but something stood out. You say your story will only have two universes for simplicity. If the character is not in her own, and someone is going to send her back, there can't be a "wrong" one. There is only her original and the one she is in. By leaving the one she is in, there's nowhere to go but the original.

Perhaps I missed something in there, but that stood out to me immediately.

Quote: Nareed

some coherent, or plausible-sounding, technobabble

You sure this is needed? I stumbled across a science fiction movie the other day about colonizing Mars for the first time. I was in a rare mood for such a movie and at first it looked like they were trying to be realistic. Then they had the actors walking around that planet with helmets off, saying "turns out we don't need them there is enough oxygen." Of course there are only traces of oxygen and almost no atmospheric pressure either. I had to turn it off.

As for the certainty that character needs, I would just have someone respond that Dr. so-and-so's procedures were being followed. That help?

Damnit, Nareed. I've work to do but my brain is now stuck in sci-fi plausibilities ><

I first assume that my original offering was incorrect and that there's many universes but you're just focusing on the two. I'll also assume the technology in your story is perfect and it's a matter of knowing which universe to send her to, not the case of knowing the universe but having sketchy tech.

To take inspiration from Geordi, could you not use chemical compostion as opposed to some frequency? Imagine there really is two universes, both containing exact copies of our solar system that came to be in the same fashion. Upon the creation of life, I'd reckon things would happen differently. If we were to visit the two and compare, I'd doubt they'd be a mirror image. Perhaps bizarro Earth would have different tech, maybe they'd have the same but used in different quantities.

Say bizarro Earthlings managed to figure out industrial use solar energy (or Mr Fusion type clean garabage burning) in bizarro 1800's, whereas we did what we did. The process of using what we used put chemicals into the soil and air, chemicals which we intake into our bodies. The bizarro people with their clean tech wouldn't have the same amounts present in their environment, so would not have the same amount present in their bodies. Testing Nareed may find X/ppb of benzene due to your use of petroleum products, where bizarro Nareed in her clean fueled world may have little to none.

Something like that maybe? It's hard to help without knowing anything about the story, but if your people know anything about the "original" universe's makeup, perhaps they could compare it to markers found on your person and identify her/it that way. That make sense?

Quote: Nareed

Here's the situation. I'm doing a story in which a character accidentally (of course) winds up in a parallel universe.

Anyway, a feature in many such stories is the implication that there are an indefinite number of universes available (Larry Niven used this notion to do his "alternate timeline story to end all alternate timeline stories"). For the purposes of my story two universes are plenty, and bringing up more would only be a distraction. But I do want to acknowledge the fact (!) that other universes exist.

"Are we certain we're returning her to her original universe?" Naturally they are, but here I need something to explain how they're certain.

Any ideas? It doesn't have to be realistic, just seem or sound something other than utterly ridiculous.

Thanks!

Perhaps I'm missing something here but it seems that according to the set-up you've described, she has been taken from "her" universe and has found herself in another one (of perhaps many). Would it not stand to reason that as she is no longer in "her" original universe all they have to do is find the universe where she can no longer be found? If there are multiple universes where she cannot be found (because presumably she never existed in that universe), simply look for the one that provides evidence of her existence (birth records, etc...) where she can no longer be found.

It's a simple, obvious and inelegant solution but science fiction stories that create convoluted and irrational theories simply for the sake of being original or twisting a plot never much appealed to me. It sounds like there's not a lot of originality in this premise anyway so I'd say go with simplicity.

Quote: Face

Damnit, Nareed. I've work to do but my brain is now stuck in sci-fi plausibilities ><

Hopefully that speaks well of my meager story-telling abilities ;)

Quote:

I first assume that my original offering was incorrect and that there's many universes but you're just focusing on the two.

Right. Trek could get away with having just the Mirror Universe (Mirror Universe is a registered trademark of the Borg Collective), becasue such stories weren't popular then. But now, to quote Asimov in his multiple universes jaunt, "The number two is ridiculous and can't exist."

Quote:

I'll also assume the technology in your story is perfect and it's a matter of knowing which universe to send her to, not the case of knowing the universe but having sketchy tech.

Yes and no. the technology doens't matter, really. Call it semi-soft SF. But having been reaised in hard SF, I ahve to pay lip service to such thigns. So, the stereotypical genius physicist-engineer hybrid is going to test his technology by sending first inanimete objects, then experimental animals. Then our heroine trapped in a Universe not her own.

Quote:

To take inspiration from Geordi, could you not use chemical compostion as opposed to some frequency?

Hey, that's good! They know where her uniform's manufactured, so the difference in, say, Carbon 14 isotopes would be subtle but definitive. Why dind't I think of that?

You're brilliant! Thank you.

Quote:

It's hard to help without knowing anything about the story,

My apologies about that. I've found that if I talk too much about a story, I lose all desire to actually write it. with any luck i should get it done within what's left of the year.

Thanks again.

Quote: Nareed

Hey, that's good! They know where her uniform's manufactured, so the difference in, say, Carbon 14 isotopes would be subtle but definitive. Why dind't I think of that?

You're brilliant! Thank you.

I'm not brilliant. I'm Toto, saving the day by pure random luck. =) Now if you'll excuse me, I'm due to FUBAR something right proper and should probably get to it ;) You're welcome, though.

Quote: Nareed

My apologies about that. I've found that if I talk too much about a story, I lose all desire to actually write it. with any luck i should get it done within what's left of the year.

Thanks again.

No apologies needed. I too found that getting to into a story without being in the process of making the story burned me out on it. Writing it was like just letting something happen. Thinking about it, though, kind of scared me out of it, too many holes to fill, ends to tie up. It's kind of like a river. If you're in it, you have no choice but to go with it and make your way out of it. If you're out of it and start thinking about it, you might not get the gumption to get in in the first place. Good luck =)

Quote: Face

I'm not brilliant.

You and the Wizard need to learn to take compliments.

Quote:

If you're in it, you have no choice but to go with it and make your way out of it. If you're out of it and start thinking about it, you might not get the gumption to get in in the first place. Good luck =)

Uh, thanks?

Quote: Nareed

Uh, thanks?

Sorry, that wasn't meant as a psyche out or discouragement. That analogy is how I have felt, I hoped to convey that I empathize with the struggle to create through writing. The wishing of luck was genuine.

I'll stop talking now. Tis better to be thought of as brilliant, than to open ones mouth and prove such thoughts as false ;)

Quote: odiousgambit

You sure this is needed?

Yes. it's a throw-away line near the end. Just to show I do consider the possibility of an infinity of alternate universes. But, really, parallel universes are fantasy anyway, strictly speaking. Travel between them, well... The point is that the idea raises interesting possibilities.

Quote: Face

Sorry, that wasn't meant as a psyche out or discouragement.

I didn't take it as anything. I simply did not understand what you said :)

Forgive me for backtracking, but it's just been chewing at the back of my mind to the point I could not tolerate it anymore. I just could not believe the facts presented here. (/gasp!) So yesterday, I did it...

I obtained an ice cube, approximately 1" x 3/4" x 3/4" in size. I placed it on the back of my hand, behind my ring and pinky finger where the skin is very thin and very sensitive. And I waited. =)

Five seconds in and I got that irritating prickly feeling. 10 seconds in and it was already numb. 20 seconds in I felt a weird ache. 40 seconds in and I had a severe ache in the bones in my hand that seemed to run up my arm. At 60 seconds I lost the ability to describe it; it wasn't beyond tolerance (close, aye, close indeed), but it was beyond my abilities to describe it. Sort of like a few days after hitting your hand with a hammer. A short time after that, the cube had melted to the point that it didn't seem to be having an effect.

Visual inspection revealed nothing, or at least nothing significant. I pressed my lips to the area and it was definately cold, not quite "ice cold", but colder than I've ever felt my skin. Within a minute or two, all pain had subsided and my hand was as good as it ever was.

Give me a few days to forget how terrible that bone ache felt and I'll try the salt =/