Gravity on the Ships from Sci-Fi Movies/Shows

[morrismike]

Bravo! Way to disprove his argument! I am overawed by your in-depth analysis of K^2's position and by your point-by-point refutation of his issues. [/sarcasm]

In all seriousness though, your "argument" is ad hominem straw-man nonsense. I say "straw-man," because K^2 didn't say that artificial gravity existed, he said that any discussion of it would be over your head. Regardless of how rude that was, the point remains that he never actually asserted that artificial gravity existed.

Of course, there is the carousel-style artificial gravity, so it is quite obvious that there is at least one type of artificial gravity in the real world.

It's fairly obvious within the stargate universe we'd be talking about gravity plates. Anti gravity with respect to this kind of technology is over all of our heads which makes mine an observation (vs. straw man) and his "rudeness" as you put it a straw man attack.

[K^2]

The ball will move toward the axle and wind up on it because it will have to rotate faster (angularly) than the axle to conserve angular momentum.

When I said "describe motion", I meant write down the equation of motion like an Engineer, not wave hands like an English major. Radius of station is 5m. Radius of axle is insignificant, at least for the first few revolutions. Drag will also be insignificant on this time scale. Angular frequency of the station is such that at 5m the centripetal acceleration of the floor is 9.8m/s². Take the initial position to be a variable r. Derive idealized trajectory as function of time, which as I said above will be followed fairly closely at least for a few revolutions.

The station is far too small to produce a noticeable coriolis effect. Our own planet is barely large enough to cause toilet whirlpools to be affected by there position relative to the equator. The ships velocity (assuming it is constant) shouldn't matter.

Coriolis Effect is proportional to the angular velocity, which will be much higher in the small station than in the large one. A 1kg object traveling up at 1m/s in the aforementioned station will experience about 2.8N of force. That is far more serious than any aerodynamic effects.

Oh, and toilet whirlpools have nothing to do with Coriolis Effect. Have you been taking physics from Urban Legends Community College?

[morrismike]

When I said "describe motion", I meant write down the equation of motion like an Engineer, not wave hands like an English major. Radius of station is 5m. Radius of axle is insignificant, at least for the first few revolutions. Drag will also be insignificant on this time scale. Angular frequency of the station is such that at 5m the centripetal acceleration of the floor is 9.8m/s². Take the initial position to be a variable r. Derive idealized trajectory as function of time, which as I said above will be followed fairly closely at least for a few revolutions.


Coriolis Effect is proportional to the angular velocity, which will be much higher in the small station than in the large one. A 1kg object traveling up at 1m/s in the aforementioned station will experience about 2.8N of force. That is far more serious than any aerodynamic effects.

Oh, and toilet whirlpools have nothing to do with Coriolis Effect. Have you been taking physics from Urban Legends Community College?

The direction of the ball and rotation are the same (corolis effect doesn't play). You got punked just get over it already.

[Colonel Sharp]

Centrifugal Force doesnot= Centripetal Force

Wikipedia win.


Gravity exists.
Electricity exists.
We don't know everything about how the universe works. (get over it)

[K^2]

The direction of the ball and rotation are the same (corolis effect doesn't play). You got punked just get over it already.

And the spring that pulls the ball up doesn't contribute to Coriolis Effect? Uhu. Right.

Look, are you going to solve the problem, or are you just going to keep talking nonsense?

Centrifugal Force doesnot= Centripetal Force

Wikipedia win.

And Centripetal Force is not the same as Centrifugal Force. They are ENTIRELY different forces.

[Quadhelix]

But if you want something to look at, look at the failed attempts to detect gravitational waves. I believe it's been a decade since the first detector went into operation and they've gotten nothing but ten years of static.

From what I've read, that seems to be more of an issue of sensitivity. Additionally, while gravitational waves have not been detected directly, observation of other star systems provides indirect evidence of their existence.

Now, if the theory of relativity was treated as a theory, I wouldn't have a problem with it.

Theory:

5. scientific principle to explain phenomena: a set of facts, propositions, or principles analyzed in their relation to one another and used, especially in science, to explain phenomena

So, it would seem that Relativity is treated as theory, just the "scientific" kind rather than "wild drunken revelry" kind.

if there were scientific answers to the points I an others have made, it would just be a simple process of explaining them logically

We tried that: you ignored us.

If you want refutation of specific points, just name those points and I will track down my post.

As for the experiments...they're fake because they don't actually test the theory, despite claims to the contrary. True tests of the theory of relativity must take place in space and cannot be accomplished on the ground or in the air.

Except that, again, particles in particle colliders behave exactly as Special Relativity predicts and nothing like Newton's laws predict. Therefore, either Special Relativity is right and Newton's laws are wrong, or both Special Relativity and Newton's Laws are wrong.

Also, they point to Mercury's orbit as proof of the theory of relativity...until you see the real numbers and notice that the discrepancy between projected orbit and observed orbit is a tiny percentage difference...easily accounted for by slight variations in planetary mass...

If you believe Newton's law of gravitation, then the planet's mass would not effect its orbit. Therefore, your "explanation" does not explain anything.

but in the mean time kids are being taught that we can't travel between stars because of a limit of light speed

The speed-of-light limit does not keep us from traveling between the stars, it only limits how quickly we can do so.

they're being taught that time isn't a constant and that you can age less than your peers if you spend some time going faster

Which, again, muons demonstrate in laboratory conditions: muons moving near the speed of light (relative to the lab) have been seen to have a longer half-life than muons "at rest."

and they're being taught that basic logic doesn't apply, most pointedly that a relative measurement can have an absolute limit...which it can't.

Experiment trumps logic.

Big bang theory and internal structure of black holes are the obvious two.

Except that the very existence of black holes was predicted using General Relativity.

Technology research here on Earth is another matter entirely. I don't believe Einstein was a wacko, I think his theories make some MATHEMATICAL sense, and there is a lightspeed limit for accelerating a BALLISTIC particle(as far as we know) because you can't push something faster than the speed of your push, and magnetism seems to peak out at lightspeed.

Except that there is far, far, far more to Special Relativity than the light-speed limit. For example, mass dilation: objects moving relative to an observer seem heavier in that observer's frame of reference. This effect, as I have mentioned, has been observed in particle accelerators. Circular particle colliders, such as the new Large Hadron Collider or the retired Large Electron-Positron Collider, use magnetic fields to exert a force on the particles pushing them toward the center of the collider. If the magnetic field were just a few percent too strong, the particles would be slammed against the inner wall of the collider.

In the Large Electron-Positron Collider, for example, the particles were accelerated to energies of roughly 45 GeV (if you believe Special Relativity), or 45,000 MeV. The particles in question, electrons and positrons, have a mass of 0.511 MeV/c^2 (even if you don't believe Special Relativity, this is the same as 9.11*10^-31 kg). However, because the particle accelerator was calibrated under the assumption that Special Relativity was correct, the field was set at the appropriate strength for a particle with a mass of 8.2*10^-26 kg; in other words, particles with a mass 90,000 times that of an electron. If Special Relativity were wrong, the particles in the accelerator would have been hi with a force 90,000 times too strong, and thus would have slammed into the inner wall of the collider.


Another effect predicted by Special Relativity is time dilation. This effect can be seen with particles that decay, such as muons - when they are moving near light-speed relative to the laboratory, their half-life increases significantly. If Special Relativity is wrong, why does this occur?

[morrismike]

And the spring that pulls the ball up doesn't contribute to Coriolis Effect? Uhu. Right.

Look, are you going to solve the problem, or are you just going to keep talking nonsense?


And Centripetal Force is not the same as Centrifugal Force. They are ENTIRELY different forces.

Going to need a lot more information to solve your problem
1. Diameter of ball
2. Mass of ball
3. diameter and K for the elastic cord plus initial tension - what is the relaxed length of the tether
4. density of air
5. velocity gradient of the air between the axle and outer part of the drum
6.is the tether attached to the axle or is it on a ring to prevent winding up of cord on the axle

Your college textbook probably ignores all of these real world considerations. You would call them meaningless I would argue they are essential to obtain the proper answer. Anxiously waiting for your reply.

[K^2]

First, I suggest solving idealization.

a) Mass = m. Diameter = 0. (point mass)
b) Spring coefficient = k. Diameter = 0. Mass = 0. Relaxed length = 0.
c) Station is evacuated, and spring is allowed to rotate freely around the axle.
d) Mass starts distance r from center rotating with the station, then released.

Then, you can see if any of the realistic parameters would cause significant deviation from idealization. IF you can show that any of these approximations would produce forces significant compared to force of the spring, centrifugal force, and Coriolis Effect, we can discuss the more realistic trajectory. Following realistic parameters apply.

2. Mass of the ball m. If you'll need it for aerodynamic effect estimates, assume it to be on the order of 100g.
1. Diameter - feel free to use typical density of steel and spherical shape.
3. Coefficient is k. It's a parameter. If you need it for something, assume that sqrt(k/m) is on the order of a few hertz. (Lets say between 1 and 5 Hz) Diameter of the spring coil is about 1cm. If you need thickness of wire from which coil is made, compute it from your parameter k. Relaxed length is less than 10cm.
4. Air is at 1atm, so about 1.3 kg/m³. Take temperature to be 20°C if you'll need viscosity or speed of sound for anything.
5. No gradient. Entire station is rotating at the same rate, including axle, so the entire air content rotates at the same angular frequency.
6. Free to rotate. Lets keep it simple.

Again, you need to show that these coefficients would cause significant deviation from idealized situation, once you solve that idealization, of course.

I have a feeling that aerodynamic effects will not be significant enough, and I can tell you right away that sphere doesn't pass close enough to the equilibrium point to cause problems, but see if you can come up with anything different. I'll leave it as an exercise for you, since you insist on realism.

[morrismike]

First, I suggest solving idealization.

a) Mass = m. Diameter = 0. (point mass)
b) Spring coefficient = k. Diameter = 0. Mass = 0. Relaxed length = 0.
c) Station is evacuated, and spring is allowed to rotate freely around the axle.
d) Mass starts distance r from center rotating with the station, then released.

Then, you can see if any of the realistic parameters would cause significant deviation from idealization. IF you can show that any of these approximations would produce forces significant compared to force of the spring, centrifugal force, and Coriolis Effect, we can discuss the more realistic trajectory. Following realistic parameters apply.

2. Mass of the ball m. If you'll need it for aerodynamic effect estimates, assume it to be on the order of 100g.
1. Diameter - feel free to use typical density of steel and spherical shape.
3. Coefficient is k. It's a parameter. If you need it for something, assume that sqrt(k/m) is on the order of a few hertz. (Lets say between 1 and 5 Hz) Diameter of the spring coil is about 1cm. If you need thickness of wire from which coil is made, compute it from your parameter k. Relaxed length is less than 10cm.
4. Air is at 1atm, so about 1.3 kg/m³. Take temperature to be 20°C if you'll need viscosity or speed of sound for anything.
5. No gradient. Entire station is rotating at the same rate, including axle, so the entire air content rotates at the same angular frequency.
6. Free to rotate. Lets keep it simple.

Again, you need to show that these coefficients would cause significant deviation from idealized situation, once you solve that idealization, of course.

I have a feeling that aerodynamic effects will not be significant enough, and I can tell you right away that sphere doesn't pass close enough to the equilibrium point to cause problems, but see if you can come up with anything different. I'll leave it as an exercise for you, since you insist on realism.

I don't deal with idealism in my profession. You're going to have to start filling in the blanks. Imperical units if you don't mind. btw grams aren't a unit of force to deal with aerodynamic drag.

[K^2]

Unless you can show me that you can solve the idealized problem, I am inclined to believe that you are not even in a profession. You learn to solve idealized cases before you learn to solve real world problems, because you NEVER account for all parameters, it is ALWAYS at least somewhat simplified. And to know how much it can be simplified, you have to start with simplest case.

Oh, and anyone who does any real engineering knows that in situations dealing with accelerated motion, what you really care about is ratio of drag to mass, which for a spherical object of fixed density is a function of mass. Therefore, me telling you that object is spherical, made of steel, and ball-park estimate for the mass gives you everything you need. You can figure out things like its Reynolds Number, terminal velocity at fixed pressure and gravity, etc. If you don't know how to do that, you probably shouldn't complain that I am asking you to solve a simpler problem first.

Now, if you simply can't solve the simple problem of a point-mass in an R² potential in a rotating frame of reference, just tell me so, and stop wasting time. I will show you how such problem is solved, why it is difficult with your rudimentary understanding of centrifugal force, and I'll even go as far as showing a first-order correction that accounts for drag, demonstrating that it really is not that significant in this problem.

[Ben 'Teal'c would WIN!!' Noble]

I can safely say as layman I have not foggest idea what your going on about
All I know is the ships in stargate use some kind of 'gravity generator'.

[South east pier]

How does it work? any Sci-Fi show or movie explained it?

Gravity on the Ships.

or we just have to assume, there is some device that's doing it.

I've always thought that the ship was accelerating until it had reached halfway. There it turned and decreased it's speed until it was where it should be.