posted 10-29-2001 19:53            

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Originally posted by Jimbo:
Who said we were?

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posted 10-29-2001 20:20            

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Originally posted by Jimbo:
If the human puts the null-grav pack on and turns it on without first taking special precautions, he or she is gonna die.

Why? Because contrary to what you might think, if you nullify gravity you won't float gently in place - you'll bob to the surface of the atmosphere like a cork in water.

Buoyant force on a volume is equal to the weight of an equivalent volume of the surrounding medium minus the weight currently contained within the volume - so let's assume a 1m by 1m by 2m rectangular solid for ease of calculation; that's 4 m³. If we assume a 15 degree (Celsius) day with the barometer at 100 kiloPascals (about normal), we're looking at about 1.2kg * 9.81 m/s² of buoyancy per m³, for a total of 47.088 kg-m/s² of buoyant force at sea level.

Great. Now let's further assume that it's me we're talking about, and that I mass 95 kilograms (I do) - by dividing my mass out of the earlier figure in kg-m/s², we can see that I'm going to be accelerated away from the earth at about half a meter per second squared. (This will of course taper off as air pressure and temperature decrease the further we go, but it'll remain relatively constant until well after I've realized how fucking dumb I was not to tie myself to a tether.)

If you do the math, this means I'll be traveling around 11MPH straight up after only ten seconds. Give me a full minute, and I'm doing better than 60MPH.

I'm not gonna bother attempting to calculate what my terminal velocity is, but obviously I'm going to have to figure out something clever regarding briefly blipping power to the null-field on and off if I wanna survive long enough to avoid doing something this stupid again.

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Physics is fun, but best left to professionals. I'm afraid this post rescinds your expert witness status.

First, I believe you'll find that a 1x1x2m solid, which is much more volume than even a large man, is 2 cubic meters, not 4. But that's just for laughs.

Second, bouyancy comes from the difference between the pressure on the bottom of a submerged object and the lesser pressure on the top. If your person is floating, then the pressure you've come up with is reasonable, if over by a factor of two. If they were, say, sitting on the ground, it would be far far smaller, there being little in the way of "underneath" surfaces for the air to exert pressure on.

Third, the reason air pressure exerts bouyant force upwards is because the air is being acted upon by gravity. If your gravity nullifier is like a shell, this doesn't matter, but if it is some sort of graviton-shield, then there are obviously air issues to be dealt with, since surrounding air will suddenly have no weight. I'd imagine that the nearby air in the column of the shield would be pushed upwards by surrounding air, forming an upwards breeze. But that's just a guess.

posted 10-29-2001 21:21            

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Originally posted by Jimbo: rotor position will not produce a change in potential energy.

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Look - the wheel's center of mass is at its axle, regardless of gravity. In a uniform gravitational field, the force associated with gravity points down, straight through the CoM - no torque. Introducing a nonuniform gravitational field shifts the force from the CoM to somewhere tangential to the CoM, resulting in torque, resulting in acceleration. I don't see what the fuss is about.

quote:

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Originally posted by Jimbo: Either the nullifier is a PMM by virtue of its ability to unfailingly inject energy all by itself - in which case it's the mystery with or without the rotor - or the nullifier is not a PMM by itself, in which case as soon as the nullifier breaks the whole thing quits moving

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In a similar vein, assuming that any device that can shield gravity must use energy proportional to the mass it shields reduces this to a trivial proof. Since we're not trivial people, we're not making that assumption. Perhaps the whole device thing is confusing - ignore the device and assume that, for some bizarre reason, the wheel (or rotor, you benighted fools) is in a region of space occupied by a non-uniform gravity well, such that gravity pulls strongly on the right side of the wheel and weakly on the left. By my reasoning, you've got yourself an engine with an efficiency greater than one, yet the (presumably more competent than me) physicist whose page I cited seems to say otherwise. That is the conundrum that made me start this thread. You're welcome to try to prove (without conservation laws, dammit) that such a nonuniform gravitational field cannot exist, or that if it can exist it must draw energy, but that's not exactly a trivial proof.

On the whole floating off into space issue, I came to the same conclusion as Fen (namely, that the biggest effect would be a breeze from the bottom of the field to the top). However, it seems to me that you would also tend to be flung tangentially into space by the Earth's rotation with a velocity that I'll figure out sometime when I'm not very, very hungry.

[edited to remove extraneous carriage returns - I've lost too many posts not to compose in notepad]

weis

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With proper thrust, pigs fly just fine.
--RFC 1925

posted 10-29-2001 22:17            

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Originally posted by fenomas:
Physics is fun, but best left to professionals. I'm afraid this post rescinds your expert witness status.

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When did I claim to be an "expert?"

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First, I believe you'll find that a 1x1x2m solid, which is much more volume than even a large man, is 2 cubic meters, not 4. But that's just for laughs.

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Argh. And well-deserved ones, no less.

quote:

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If they were, say, sitting on the ground, it would be far far smaller, there being little in the way of "underneath" surfaces for the air to exert pressure on.

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True enough, but in the real world it doesn't make a whole hell of a lot of difference in most cases - if you lie as flat as you possibly can on the bottom of a lake while wearing a life jacket, you'll still bob to the surface plenty quick.

If the field extends below surface level and is vertical or expanding horizontally, you're right... but if it makes imperfect contact at floor level, or if it's shrinking horizontally before it hits floor level you'd still get a lifting surface.

quote:

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then there are obviously air issues to be dealt with, since surrounding air will suddenly have no weight. I'd imagine that the nearby air in the column of the shield would be pushed upwards by surrounding air, forming an upwards breeze. But that's just a guess.

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Oooh, good point - you'd need a precisely-fitting field to get more than a breeze. Missed that.

posted 10-29-2001 22:37            

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Originally posted by weis:
[QUOTE]However, it seems to me that you would also tend to be flung tangentially into space by the Earth's rotation with a velocity that I'll figure out sometime when I'm not very, very hungry.

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Definitely. I'd think that would be a rather gradual sort of thing, though.

As for the whole wheel thing, I still don't see how a wheel centered on an axle can be made to rotate with a constant gravitational field, however irregular it might be - you're still not producing any change in potential with changes in position.

As far as I can tell, you'd bump the wheel once if you suddenly subjected it to a radical change in the gravitational field local to one side of it, but then it would stabilize.

Incidentally, upon rereading the page in question, it would seem that what the author had to say about the uniform wheel:

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This machine is uni-directional. Stevin's principle demolishes the version with a uniform wheel, for the initial and final states of system and environment are identical. Therefore it cannot move on its own. So why did we mistakenly think that it should turn by itself?

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... is a rather more brief version of the same thing I was saying about changes in potential energy, without all the ham-handed fumbling about calling segments chords and et cetera. The net result of the wheel rotating is no change in state in state of system or environment, so why would the wheel turn?

I think there's a conceptual error somewhere in your statement concerning shifting the vector arrow for gravitational force, but it's late, and I'm not man enough to figure it out.

posted 10-30-2001 05:50            

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Originally posted by fenomas:
Next lesson is that one about the three doors on the gameshow, and why you should switch.

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posted 10-30-2001 10:54            

Please fel free to critique the schematic of my HYPER DIMENSIONAL RESONATOR.

posted 10-30-2001 18:58            

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Originally posted by Jimbo:
Oooh, I hate that one. Mostly because the people who state it usually fail to disclose crucial information concerning the host's prior knowledge or lack thereof, and/or how he does or does not allow it to alter his behavior.

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Are you still crabbing on this? See, I know you mean me here, and I STILL say that the host reveals that he knows where the car is when he opens a door. He wouldn't guess!

ADMIT DEFEAT!

(if I'm misremembering this, and had this argument with someone other than you, please so inform me)

posted 10-30-2001 23:55         

You're not a traitor, are you?

The computer loves you.

posted 10-30-2001 23:59            

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Originally posted by hussain:
say it with me kids, hypothetical temporal mechanics bad. sitting and masturating good. physics bad. jerking good.

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posted 10-31-2001 22:55            

WHO LET THE DOGS OUT?????

Jesus, that is why Einstein was so much smarter than all of you!

But in a fight, Linus Pauling would win by a mile. He's all about protein, not elevators and rocket ships

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"Two things are infinite: the universe and human stupidity; and I'm not even sure about the universe."
-Albert Einstein-

posted 11-01-2001 14:00           

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Dumb ass students enslaved by ignorance of Time Cube.
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No student on Earth is allowed to know Time Cube - which disproves god scams.
That is criminal academia. Christianity based upon evil 1-corner self aggrandizing
which dooms 4-corner life. Challenge stupid teachers and their 'Obscurantism' (deliberately withheld knowledge).

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MIT, Massachusetts Institute of Technology has invited me as a guest lecturer to inform them about Nature's Time Cube, in January.

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Cube proves you are Stupid. Academic Word is Cubeless. Cubeless Word Dooms USA. Time Cube is Omnific Order. Cowards ignore Time Cube.

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There is no entity on Earth, for all of creation is Cubic - with a top and bottom with front and back and 2 sides.
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YOU KNOW WHAT!!!
You are educated stupid as teachers lack intelligence.

Truth is Cubic.
Time is Cubic...
Life is Cubic....
Form is Cubic..
Family is Cubic..
Village is Cubic..
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Evil is cubeless.
Self is cubeless.
God is cubeless.
Language is a human invention of an evil cubeless singularity.
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You only know what you know from your mental brainwashing and word indoctrination since
your birth. It is imperative that that you know what you don't know, but what you know, will not allow you to know what you don't know. The God words you know, will not allow you to know TIME CUBE's Highest Life Order.

posted 11-01-2001 17:20            

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... Analogy, a lightbulb, that gives off light, and a mechanism to draw the light (gravity field, controlled, and strong it would have to be, without black hole effects) (or hell some other light object to draw light waves back in) - now the light drawn back in would be converted to EE with an efficiency of 100%, would it be dark in the room?

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But that doesn't prove WHY it wouldn't work without using the "laws of conservation of energy" (which any perpetual motion machine is trying to disprove anyway).

Plus... if you used a gravity field to absorb light, wouldn't anyone in the room die? If you avoided the other effects of a black hole, wouldn't that violate conservation of energy?

Does a black hole give off heat? Can the heat escape the black hole?