Why artificial gravity is not possible?

[dkotschessaa]

Of course whatever means we come up (rather than the rotational solution) is going to have an effect on nearby bodies, i.e. earth, if we are talking about putting this thing in orbit. What crazy tidal effects might we expect? Surfs up?

-DaveKA

 

[cjameshuff]

you could place the space station in one of the gravity neutrals. therefore you wouldn't need fuel to spin the station it would all be done by repulsing gravity and ceterfugal force! Could scarifice gravity for supplies by using thruster engines to move you to supplies that were launched into space...then you would have to find the neutral zone again...Maybe 90% of t he supplies would be fuel?

pardon my spelling but its very possible! Gravity as a force has to exist between all large objects and the math of the middle is key. Put an object in the neutral zone and it will spin at the rate to create gravity

...where did you get this idea?
The only "gravity neutral" I can think of in Earth's neighborhood is the point where Earth's and the moon's gravity is equal, just a bit on the far side of the Earth-Moon L1 point. Gravity doesn't repel and an object placed at this location (or the nearby L1 point, where you can actually have a closed orbit, albeit an unstable one) won't start spinning on its own...not due to being at any sort of neutral point, anyway.

And aside from that "neutral zone" stuff not working at all as described, it sounds like you're suggesting saving the small amount of fuel needed to spin up the station by using massive amounts of fuel to chase supplies around this "neutral zone"...

 

[DaveC426913]

you could place the space station in one of the gravity neutrals. therefore you wouldn't need fuel to spin the station it would all be done by repulsing gravity and ceterfugal force! Could scarifice gravity for supplies by using thruster engines to move you to supplies that were launched into space...then you would have to find the neutral zone again...Maybe 90% of t he supplies would be fuel?

pardon my spelling but its very possible! Gravity as a force has to exist between all large objects and the math of the middle is key. Put an object in the neutral zone and it will spin at the rate to create gravity

Yeah, I don't know what you're getting at. This describes nothing in physics that I know of.

There are Lagrange points, but they don't cause any spinning.

 

[thedeester1]

...where did you get this idea?
The only "gravity neutral" I can think of in Earth's neighborhood is the point where Earth's and the moon's gravity is equal, just a bit on the far side of the Earth-Moon L1 point. Gravity doesn't repel and an object placed at this location (or the nearby L1 point, where you can actually have a closed orbit, albeit an unstable one) won't start spinning on its own...not due to being at any sort of neutral point, anyway.

And aside from that "neutral zone" stuff not working at all as described, it sounds like you're suggesting saving the small amount of fuel needed to spin up the station by using massive amounts of fuel to chase supplies around this "neutral zone"...

I got this off of Wikki...not the most reliable source I know...But its kinda what i was getting at...Im not a student of astro physics its kinda a hobby for a geek.

http://en.wikipedia.org/wiki/Lagrangian_point

other neutral gravity points must exist between all mass in the solar system and the universe...otherwise fast colapse would be occurring NOW.

 

[nismaratwork]

I got this off of Wikki...not the most reliable source I know...But its kinda what i was getting at...Im not a student of astro physics its kinda a hobby for a geek.

http://en.wikipedia.org/wiki/Lagrangian_point

You've utterly misunderstood everything I can imagine in regards to what Langrangian points are, based on what seems to be a complete lack of understanding of gravity. I would recommend some reading on those subjects.

 

[russ_watters]

I got this off of Wikki...

Could you quote the passage in the wiki that says putting an object at a Lagrange point will make it spin?

 

[nismaratwork]

I got this off of Wikki...not the most reliable source I know...But its kinda what i was getting at...Im not a student of astro physics its kinda a hobby for a geek.

http://en.wikipedia.org/wiki/Lagrangian_point

other neutral gravity points must exist between all mass in the solar system and the universe...otherwise fast colapse would be occurring NOW.

re the bolded portion: OK, you added this... why? Lagrangian points are not 'gravity neutral' in the way you're portraying them. Your conclusion that somehow these points are producing a repulsive force that keeps universal expansion from being overwhelmed by mass... then WHAT THE **** are you talking about?!

 

[thedeester1]

Could you quote the passage in the wiki that says putting an object at a Lagrange point will make it spin?

no i cant...sorry...But i think that it will spin. this is my thinking as a novice.. You could try it out place 2 metal ojects on a table then rotate the outer object. given our gravity your going to have to spin the object very quickly.. In space however i don't think that's the case. The passing centrifugal force will spin the said space station...i think

 

[cjameshuff]

no i cant...sorry...But i think that it will spin. this is my thinking as a novice.. You could try it out place 2 metal ojects on a table then rotate the outer object. given our gravity your going to have to spin the object very quickly.. In space however i don't think that's the case. The passing centrifugal force will spin the said space station...i think

I'm sorry, but...I don't think any of what you've posted can clearly be said to be correct. A full explanation of what you got wrong would be a physics primer that starts from a clean slate. I'm not even sure what you're trying to illustrate with your metal objects on a table. Aside from air currents, vibrations, etc, spinning one won't do anything to the other...regardless of spin or amount of gravity. (lets not bring frame dragging into this, let the guy get a grip on Newtonian mechanics first...)

The Wikipedia article you linked is fine, but your interpretation of it is totally off the mark. Some better starting points:
http://en.wikipedia.org/wiki/Newton's_laws_of_motion
http://en.wikipedia.org/wiki/Newton's_law_of_universal_gravitation

But given how badly confused the L-point article got you, I'm not sure how much help this will be. You might be better off checking out an introductory physics testbook from a library.

 

[nismaratwork]

no i cant...sorry...But i think that it will spin. this is my thinking as a novice.. You could try it out place 2 metal ojects on a table then rotate the outer object. given our gravity your going to have to spin the object very quickly.. In space however i don't think that's the case. The passing centrifugal force will spin the said space station...i think

This isn't your thinking as a novice, this is just some random thinking based on concepts you seem to only just have learned. You clearly don't understand the most basic models of gravity, never mind Relativity's view. cjameshuff is right, you just need to start from square one... carefully.

 

[tggokulesh]

you are wrong . it is easy to create an artificial gravity.this is what einstein's(actually its mach's) equivalence principle states.if you accelerate upwards it would produce a natural gravity which is induced.to know more read general relativity basics

 

[nismaratwork]

you are wrong . it is easy to create an artificial gravity.this is what einstein's(actually its mach's) equivalence principle states.if you accelerate upwards it would produce a natural gravity which is induced.to know more read general relativity basics

Really? Can you cite a single reference to support that?

 

[DaveC426913]

Really? Can you cite a single reference to support that?

Well, he's simply saying a ship under constant acceleration (say, 1g) will give its occupants the same effect as gravity. And he's quite right.

Problem is:
1] It's a huge fuel cost, accelerating all the way.
2] The occupants would go floating away every time the ship wanted to stop.

 

[dkotschessaa]

Does the inverse square law apply to the the forces created in this way (acceleration or rotation?)

-DaveKA

 

[DaveC426913]

Does the inverse square law apply to the the forces created in this way (acceleration or rotation?)

-DaveKA

No.

In the case of rotational AG, you won't experience it unless you are in contact with the deck.

In the case of accelerative AG, you will experience the acceleration of the deck toward you, but it will be independent of your distance from the deck.

 

[nismaratwork]

Well, he's simply saying a ship under constant acceleration (say, 1g) will give its occupants the same effect as gravity. And he's quite right.

Problem is:
1] It's a huge fuel cost, accelerating all the way.
2] The occupants would go floating away every time the ship wanted to stop.

Yes, but that's not gravity, but a totally different pseudo-force. Obviously we're long past spinning up stations, magnets, and the like. It isn't a "natural gravity" as he said, nor (and this is crucial as you've already pointed out the issues) is it "easy". I'm not arguing against centrifugal force or 1g constant acceleration... which STILL doesn't solve the problem. Even if you have massive amounts of fuel and don't want to stop, you eventually start getting close to c, and are no longer able to sustain 1g.

[STRIKE]dkotschessaa: Well, it applies to Gravity, which by the equivalence principle means that any related pseudo-force should too. I'm not sure that it's that simple, but that's my guess.[/STRIKE]
edit: The above is clearly wrong (having read Dave's post). My bad!

 

[DaveC426913]

Yes, but that's not gravity, but a totally different pseudo-force.

tggokulesh actually says "artifical gravity":

"...it is easy to create an artificial gravity..."

Granted he then says that "...it would produce a natural gravity..." but I think he's means natural-feeling gravity - as in "indistinguishable from real gravity", which is true (contrarily, rotational AG is experientially quite unlike real gravity.)

Even if you have massive amounts of fuel and don't want to stop, you eventually start getting close to c, and are no longer able to sustain 1g.

What makes you think this??

You can continue to accelerate, experiencing 1g in your spacecraft , for your entire natural life, your children's lives and the rest of eternity.


Care to retract that comment?

 

[DrGreg]

Yes, but that's not gravity, but a totally different pseudo-force.

Not totally different; according to the equivalence principle, in a small enough region there's virtually no difference.

Even if you have massive amounts of fuel and don't want to stop, you eventually start getting close to c, and are no longer able to sustain 1g.

As I recently said in another thread...

In relativity, acceleration is relative too. Although all inertial observers agree whether an object is accelerating or not, they disagree over the value of a non-zero acceleration. An inertial observer who is momentarily at rest relative to an accelerating object ("comoving inertial observer") will measure a larger acceleration than observers who have non-zero relative velocity, and the acceleration tends to zero as the relative velocity approaches the speed of light.

The acceleration measured by a comoving inertial observer is called "proper acceleration". It the "g-force" that the object experiences and what is measured by an accelerometer attached to the object.

If your rocket was accelerating with a constant proper acceleration of 1 g, the acceleration measured by an inertial observer would gradually decrease [STRIKE]to[/STRIKE] towards* zero. So you can continue at 1 g as long as you like, fuel permitting.

EDIT *corrected in view of DaveC's comment in #119

 

[DaveC426913]

If your rocket was accelerating with a constant proper acceleration of 1 g, the acceleration measured by an inertial observer would gradually decrease to zero. So you can continue at 1 g as long as you like, fuel permitting.

Just in case Dr Greg's explanation is ambiguous: an observer external to the spaceship would see its acceleration approach zero (though, DrGreg, it would never actually reach zero as you imply) - but the spaceship occupant would happily experience 1g for a long as he wishes.

 

[DrGreg]

In the case of accelerative AG, you will experience the acceleration of the deck toward you, but it will be independent of your distance from the deck.

Actually if you were supported at a constant height of h above the deck, you'd experience a proper acceleration of

a = \frac{g}{1 + \frac{gh}{c^2}}​

so it's not an inverse square law, just an inverse law.

(This is a consequence of Rindler coordinates.)

 

[nismaratwork]

Oooh... gah. OK, well I was quite wrong. Thanks to both of you, DaveC, DrGreg, for the corrections and help.

 

[cjameshuff]

Granted he then says that "...it would produce a natural gravity..." but I think he's means natural-feeling gravity - as in "indistinguishable from real gravity", which is true (contrarily, rotational AG is experientially quite unlike real gravity.)

That may give the wrong impression. It's really no different from the linear case, except for the addition of Coriolis forces and variations in acceleration at different heights. As the radius of rotation increases, these effects become weaker and weaker. Give a constantly-accelerating spacecraft a bit of constant rotation around an axis perpendicular to that of thrust, and it will travel a circular path and give exactly the same appearance of gravity as it would if it were swinging from a tether.

You could of course determine that you are rotating with instrumentation...simple gyroscopes and pendulums would be sufficient (http://en.wikipedia.org/wiki/Foucault_pendulum). If the radius of rotation is great enough, there is no difference so far as biology is concerned.

Actually if you were supported at a constant height of h above the deck, you'd experience a proper acceleration of

a = \frac{g}{1 + \frac{gh}{c^2}}​

so it's not an inverse square law, just an inverse law.

(This is a consequence of Rindler coordinates.)

You've got to keep the scale of the effect in mind, though. To reduce 9.8 m/s^2 to 9.7 m/s^2 requires a distance of about 300000 light seconds, or 600 AU.

 

[DaveC426913]

That may give the wrong impression. It's really no different from the linear case, except for the addition of Coriolis forces and variations in acceleration at different heights. As the radius of rotation increases, these effects become weaker and weaker. Give a constantly-accelerating spacecraft a bit of constant rotation around an axis perpendicular to that of thrust, and it will travel a circular path and give exactly the same appearance of gravity as it would if it were swinging from a tether.

Well, I can show some other rather pronounced differences with rotational AG. Notably, if you could quite easily, through only your own actions, cancel it entirely. Ignoring air friction, you could hover weightless above the surface indefinitely.

 

[cjameshuff]

Well, I can show some other rather pronounced differences with rotational AG. Notably, if you could quite easily, through only your own actions, cancel it entirely. Ignoring air friction, you could hover weightless above the surface indefinitely.

With the capsule-and-tether approach it's just impossible, you'd splat against the wall. In a fully enclosed 224 meter radius 2 rpm habitat, you would somehow have to change your speed by 47 m/s...that is, about 105 mph or 170 kph. I would not describe this as something a human could easily do through only their own actions...not actions they could reasonably expect to survive, anyway.

 

[DaveC426913]

With the capsule-and-tether approach it's just impossible, you'd splat against the wall. In a fully enclosed 224 meter radius 2 rpm habitat, you would somehow have to change your speed by 47 m/s...that is, about 105 mph or 170 kph. I would not describe this as something a human could easily do through only their own actions...not actions they could reasonably expect to survive, anyway.

Well, that's true if you put constraints on it. You're limiting my freedom to demonstrate how gravity works. If the station were toroidal, I could accelerate antispinward to the point where I could become weightless, at least until air friction spun me up again. If I could do this without having to worry about friction, I could float weightless indefinitely, or at least until a I encountered the first wall to antispinward.

 

[nismaratwork]

Well, that's true if you put constraints on it. You're limiting my freedom to demonstrate how gravity works. If the station were toroidal, I could accelerate antispinward to the point where I could become weightless, at least until air friction spun me up again. If I could do this without having to worry about friction, I could float weightless indefinitely, or at least until a I encountered the first wall to antispinward.

The experience of the air-friction spinning you up again would also be pretty gradual and gentle... could be fun!... unless you hit that wall at speed...

 

[dkotschessaa]

No.

In the case of rotational AG, you won't experience it unless you are in contact with the deck.

In the case of accelerative AG, you will experience the acceleration of the deck toward you, but it will be independent of your distance from the deck.

That's kind of what I thought. Thanks for clarifying. So such gravity isn't really quite "natural."

-DaveKA

 

[nismaratwork]

That's kind of what I thought. Thanks for clarifying. So such gravity isn't really quite "natural."

-DaveKA

It isn't a curvature in spacetime and thus isn't a 'type' of gravity... it's an effect which is equivalent in some ways, under specific circumstances.

 

[cjameshuff]

Well, that's true if you put constraints on it. You're limiting my freedom to demonstrate how gravity works. If the station were toroidal, I could accelerate antispinward to the point where I could become weightless, at least until air friction spun me up again. If I could do this without having to worry about friction, I could float weightless indefinitely, or at least until a I encountered the first wall to antispinward.

You put constraints on it, by saying "Notably, if you could quite easily, through only your own actions, cancel it entirely. Ignoring air friction, you could hover weightless above the surface indefinitely.". Humans can generally not accelerate themselves to more than a small fraction of the needed velocity in a minimum-sized structure (based on what's needed to achieve 1 g with a comfortable rotation rate). If you were in such a habitat, the most you could do is slightly reduce the apparent gravity.

Apart from the added tidal effects on the part of planets and Coriolis effects on the part of rotating structures, the constant upward acceleration exerted by a planet's surface on objects resting on it is indistinguishable from the constant acceleration in one direction of the spaceship or the constant acceleration toward a point of the rotating structure.

 

[DaveC426913]

You put constraints on it, by saying "Notably, if you could quite easily, through only your own actions, cancel it entirely.

Note that there are several ways of doing this. Another one is simply going up to the space station's attic - quite easy do to through only one's own actions.

Ignoring air friction, you could hover weightless above the surface indefinitely.". Humans can generally not accelerate themselves to more than a small fraction of the needed velocity in a minimum-sized structure (based on what's needed to achieve 1 g with a comfortable rotation rate). If you were in such a habitat, the most you could do is slightly reduce the apparent gravity.

Your stance boils down to: if you arrange a space station carefully enough, you can get it to simulate gravity with seemingly little difference from real gravity, if you don't stray too far in any of several directions.

But moving in one of several directions is enough to make a noticeable/dramatic change in gravity. Spinward, antispinward, but also vertically up or down, all change the effect of gravity - and these are very normal things one might do.

It comes down to a subjective call as what one considers "similar" to real gravity. I see these things as quite different (possibly alarmingly so, people will surely get injured, or worse, until they get used to it); you do not see them is significant. Neither of us is wrong.

Apart from the added tidal effects on the part of planets and Coriolis effects on the part of rotating structures, the constant upward acceleration exerted by a planet's surface on objects resting on it is indistinguishable from the constant acceleration in one direction of the spaceship or the constant acceleration toward a point of the rotating structure.

cjameshuff's first law:
If one ignores all the ways two things are different, then those two things are indistinguishable.

I cannot escape that ironclad logic.

 

[cjameshuff]

Note that there are several ways of doing this. Another one is simply going up to the space station's attic - quite easy do to through only one's own actions.

And if you climb a giant space elevator on a planet, gravity drops off as you rise. And if you jump off an accelerating spacecraft , you get left behind in freefall. Neither of these actions affects the fact that the appearance of gravity itself is identical.

It comes down to a subjective call as what one considers "similar" to real gravity. I see these things as quite different (possibly alarmingly so, people will surely get injured, or worse, until they get used to it); you do not see them is significant. Neither of us is wrong.

cjameshuff's first law:
If one ignores all the ways two things are different, then those two things are indistinguishable.

I cannot escape that ironclad logic.

No...to be blunt, you are wrong. It is not subjective. The only difference between "centrifugal gravity" and "linear acceleration gravity" is the addition of Coriolis effects. These are not responsible in any way for the impression of gravity, they are simply an artifact of the rotating frame. The impression of gravity is caused in exactly the same way in both cases, and the equivalence of that effect with the effect experienced on the surface of a planet is a rather fundamental principle of relativity.

Coriolis effects and tidal forces are not differences in the nature of the acceleration, they are additional effects that are independent of the acceleration itself...the one resulting simply from being in a rotating reference frame, the other from being in a gravitational field from a spherical body. Both can be experienced in freefall, and both can be made arbitrarily small without affecting the apparent gravitational force, the one by decreasing the rate of rotation (approaching a straight-line acceleration as the radius of rotation approaches infinity), the other by decreasing the density of the sphere.

 

[DaveC426913]

And if you climb a giant space elevator on a planet, gravity drops off as you rise. And if you jump off an accelerating spacecraft , you get left behind in freefall. Neither of these actions affects the fact that the appearance of gravity itself is identical.




No...to be blunt, you are wrong. It is not subjective. The only difference between "centrifugal gravity" and "linear acceleration gravity" is the addition of Coriolis effects. These are not responsible in any way for the impression of gravity, they are simply an artifact of the rotating frame. The impression of gravity is caused in exactly the same way in both cases, and the equivalence of that effect with the effect experienced on the surface of a planet is a rather fundamental principle of relativity.

Coriolis effects and tidal forces are not differences in the nature of the acceleration, they are additional effects that are independent of the acceleration itself...the one resulting simply from being in a rotating reference frame, the other from being in a gravitational field from a spherical body. Both can be experienced in freefall, and both can be made arbitrarily small without affecting the apparent gravitational force, the one by decreasing the rate of rotation (approaching a straight-line acceleration as the radius of rotation approaches infinity), the other by decreasing the density of the sphere.

I don't know why you insist on dimissing these differences.

Let me try to reframe it. I think your argument is that, physics-wise, the forces in play are equivalent. If you look at a small enough subset of effects, then that subset is the same in all versions of gravity. (I've captured this, rather facetiously but accurately in cjamehuff's First Law.)

I grant the equivalence principle. But the EP applies academically - in a lab (where you isolate it).


But from a human point of view (which is what we've been talking about), the difference, whether you wish to dismiss them or not, are quite noticeable.

Massive gravity
- has a gradient, lessens as square of distance (not noticeable on any reasonable human scale)


Accelerative artificial gravity
- no gradient (on a hundred mile long ship, g is the same at all points ,also very small effect)
- g-force experiences are intimately tied to ship's motion

Rotational artificial gravity
- pronounced Coriolis forces
--- falling, jumping or any other ballistic motion imparts sideways motion
--- moving spinward increases weight, antispinward deceases weight, to the point of weightlessness
- AG is markedly different on different decks, some decks have micro-g, some have zero-g

 

[stonecoldgen]

In order to create artificial gravity you would need to have the space station constantly accelerating in one direction so that the people inside would experience a force equal to the rate of acceleration times their body mass. This would create the illusion of weight. This is impractical because the station can't just keep accelerating; it would run out of fuel at some point. Utilizing centripetal acceleration could work, but the space station would need to be orbiting very quickly for any significant effects.

you reminded me of 2001: a space odissey with the centripetal force ''gravity-generator''

 

[Chronos]

Get a good book on GR, a comfortable bed, and read cjames. You are clueless.

 

[nismaratwork]

Get a good book on GR, a comfortable bed, and read cjames. You are clueless.

Wow, usually I'm the guy who says that, then gets modded. This is damned refreshing (the first part, hopefully not the second).

 

[cjameshuff]

I don't know why you insist on dimissing these differences.

I don't know why you insist on focusing on extraneous effects, and not just ignoring but outright denying the fact that the resulting appearance of gravity is identical.

Let me try to reframe it. I think your argument is that, physics-wise, the forces in play are equivalent. If you look at a small enough subset of effects, then that subset is the same in all versions of gravity. (I've captured this, rather facetiously but accurately in cjamehuff's First Law.)

Stop this "First Law" nonsense. It's insulting and it reveals that you aren't paying attention to what I'm saying.

I grant the equivalence principle. But the EP applies academically - in a lab (where you isolate it).

Nothing but anti-intellectual nonsense. It applies to everything, everywhere.

But from a human point of view (which is what we've been talking about), the difference, whether you wish to dismiss them or not, are quite noticeable.

Massive gravity
- has a gradient, lessens as square of distance (not noticeable on any reasonable human scale)


Accelerative artificial gravity
- no gradient (on a hundred mile long ship, g is the same at all points ,also very small effect)
- g-force experiences are intimately tied to ship's motion

Rotational artificial gravity
- pronounced Coriolis forces
--- falling, jumping or any other ballistic motion imparts sideways motion
--- moving spinward increases weight, antispinward deceases weight, to the point of weightlessness
- AG is markedly different on different decks, some decks have micro-g, some have zero-g

You for some reason seem to refuse to consider anything but small radius, high rotation systems. Coriolis effects diminish to nonexistence as rotation rate diminishes to zero...you can not say they are pronounced, only that they exist in rotating frames. They even exist on rotating planets. A space station with a rotation rate of one day, and Coriolis effects no stronger than those you're experiencing right now is entirely physically plausible.

On a structure with a radius of rotation large enough to have a comfortably low rotation rate, a human being simply can not move themselves fast enough to influence the apparent gravity to a notable degree. In human terms, gravity is constant. You make it sound like you'll go careening through the sky if you run in the wrong direction...this is simply false. As for climbing toward the center, if you can insist on decks at all levels of gravity in a rotating structure, I can insist on a giant tower with microgravity at the uppermost levels, or a tunnel to the center of the planet. It's irrelevant.

Once again, take your accelerating spacecraft . Give it a slight rotation perpendicular to the direction of thrust...say once every 24 hours. Your spacecraft is now traveling a circular path, but without special equipment, the occupants have no way of telling that this is the case. Cut the engines...is the rotation the cause of the apparent gravity? The occupants now rattling around in microgravity would not agree with you. Attach it to a counterweight by a long tether so it travels the same circular path it did before...the occupants wouldn't be able to tell the difference. In human terms, no matter how they jump, run, or climb, they wouldn't be able to tell they weren't accelerating in a straight line or resting on a planet's surface. Even with special equipment, they would have to measure other effects associated with rotating frames or gravity wells to determine their situation.

Get a good book on GR, a comfortable bed, and read cjames. You are clueless.

I think you got my posts mixed up with DaveC426913's.

 

[nismaratwork]

I don't know why you insist on focusing on extraneous effects, and not just ignoring but outright denying the fact that the resulting appearance of gravity is identical.




Stop this "First Law" nonsense. It's insulting and it reveals that you aren't paying attention to what I'm saying.




Nothing but anti-intellectual nonsense. It applies to everything, everywhere.




You for some reason seem to refuse to consider anything but small radius, high rotation systems. Coriolis effects diminish to nonexistence as rotation rate diminishes to zero...you can not say they are pronounced, only that they exist in rotating frames. They even exist on rotating planets. A space station with a rotation rate of one day, and Coriolis effects no stronger than those you're experiencing right now is entirely physically plausible.

On a structure with a radius of rotation large enough to have a comfortably low rotation rate, a human being simply can not move themselves fast enough to influence the apparent gravity to a notable degree. In human terms, gravity is constant. You make it sound like you'll go careening through the sky if you run in the wrong direction...this is simply false. As for climbing toward the center, if you can insist on decks at all levels of gravity in a rotating structure, I can insist on a giant tower with microgravity at the uppermost levels, or a tunnel to the center of the planet. It's irrelevant.

Once again, take your accelerating spacecraft . Give it a slight rotation perpendicular to the direction of thrust...say once every 24 hours. Your spacecraft is now traveling a circular path, but without special equipment, the occupants have no way of telling that this is the case. Cut the engines...is the rotation the cause of the apparent gravity? The occupants now rattling around in microgravity would not agree with you. Attach it to a counterweight by a long tether so it travels the same circular path it did before...the occupants wouldn't be able to tell the difference. In human terms, no matter how they jump, run, or climb, they wouldn't be able to tell they weren't accelerating in a straight line or resting on a planet's surface. Even with special equipment, they would have to measure other effects associated with rotating frames or gravity wells to determine their situation.




I think you got my posts mixed up with DaveC426913's.

re: bold: This is you... http://en.wikipedia.org/wiki/Illusory_superiority

cjameshuff, you're so far from reality I can't tell if you're ignorant of GR as Chronos posits. or a crackpot.


Your application of the EP in this distorted way is just wrong... I don't know another way to put it... you're wrong and if you'd read that book Chronos mentioned you'd know it.

 

[cjameshuff]

re: bold: This is you... http://en.wikipedia.org/wiki/Illusory_superiority

cjameshuff, you're so far from reality I can't tell if you're ignorant of GR as Chronos posits. or a crackpot.


Your application of the EP in this distorted way is just wrong... I don't know another way to put it... you're wrong and if you'd read that book Chronos mentioned you'd know it.

A couple people do seem to be suffering from illusory superiority. That you apparently don't even realize that I've barely even mentioned the equivalence principle of GR says something about who that might be. My explanations regarding centrifugal and linear acceleration, which seem to be the main source of DaveC426913's confusion, don't even require any reference to GR to understand. The equivalence principle of GR is more general, equating such accelerating frames with the frame of an object resting on a planetary surface, or otherwise "stationary" with respect to a gravitational field.

Here's another Wikipedia link: http://en.wikipedia.org/wiki/Equivalence_principle

Read it. And perhaps a good book on physics, too. And make sure your criticisms are on target in the future. Maybe give something resembling a counterargument, rather than a blanket "you're wrong!"?

 

[nismaratwork]

A couple people do seem to be suffering from illusory superiority. That you apparently don't even realize that I've barely even mentioned the equivalence principle of GR says something about who that might be. My explanations regarding centrifugal and linear acceleration, which seem to be the main source of DaveC426913's confusion, don't even require any reference to GR to understand. The equivalence principle of GR is more general, equating such accelerating frames with the frame of an object resting on a planetary surface, or otherwise "stationary" with respect to a gravitational field.

Here's another Wikipedia link: http://en.wikipedia.org/wiki/Equivalence_principle

Read it. And perhaps a good book on physics, too. And make sure your criticisms are on target in the future. Maybe give something resembling a counterargument, rather than a blanket "you're wrong!"?

Counterarguments, sweet reason, and evidence don't seem to phase you, so I figured that I'd give brutal honesty a try.

 

[DaveC426913]

Here's another Wikipedia link: http://en.wikipedia.org/wiki/Equivalence_principle

..
Maybe give something resembling a counterargument, rather than a blanket "you're wrong!"?

Actually, we have given multiple, carefully-crafted counter arguments. Whether you agree with them or not, to claim we have just said a blanket "you're wrong" is not helping your case.

It is unfortunate that various ad hominems flung your way have driven you to respond in-kind.


Now: We all understand the equivalence principle quite well. It would be folly of you to think otherwise. Did you read the part where it says

"local" has a very special meaning: not only must the experiment not look outside the laboratory, but it must also be small compared to variations in the gravitational field, tidal forces, so that the entire laboratory is freely falling.

This is key.

EP is applicable to an ideal scenario, where you couldn't look out the window, couldn't feel Coriolis Forces and couldn't measure gravitational gradients.

But living a space station we would dealing with practical experiences. And these different types of AG, regardless of what you might want to think, have practical implications. At the risk of predicting the future, I hazard to say newbies to space stations will get injured before they figure them out. That's a difference.

I don't know why you insist on focusing on extraneous effects, and not just ignoring but outright denying the fact that the resulting appearance of gravity is identical.

You have contradicted yourself.

You concede that there are effects. You continue to acknowledge them by claiming "them" to be extraneous.

Now you claim the result is identical. You contradict yourself.


Look, this is not a 'he said she said' argument; It is not equivalent. I can demonstrate that your stance is indefensible due to the fact that you are taking a strong stance, one that is easy to knock down. You cannot demonstrate that my stance is indefensible because I am not taking a strong stance.

You claim there are NO differences; I claim there are SOME differences.

I only have to demonstrate that there is ONE differnece of ANY size to show your stance is in error.
You on the other hand, have to demonstrate that, of all the possible differences there could be, they are ALL nonexistent before you could show I am in error.

I present one. In a spinning station of any practical size, the Coriolis Force will be present, and in fact, quite observable.

 

[dj cornbread]

Creating artificial gravity by rotational force, would make it hard to dock any external vehicle. Also the outward force would make outside repairs and first hand observations near impossible. Stopping and starting the rotation for these purposes would also become a fuel consumption issue.
If you had something resembling jacks (the toy) it would be near impossible to travel to other compartments.
If you were to use a tube... traveling fore and aft would be easy but if you were to have to walk port and starboard you'd be walking up hill (a bit tiring if your working) before anyone says it, i know a octagon would be better suited for this, but the principal is the same.
Even the act of moving around one compartment could throw off the balance of the station in a whole causing a wobble (not good)
I do not know if this would effect the body over time, but, with gravity your being pulled more at your feet than your head. with centrifugal force it is the opposite. I'm thinking this may cause issues with blood circulation.

Best bet, actual gravity. (as far as a stationary body is concerned) use an extremely high density material (much like a black hole is small and dense) this would only work on a stationary object in orbit not for a craft traveling out (as the added mass would make accelleration near impossible)
(benifits if this weren't near impossible)
no bone degeneration
less worry about flying off the body or loosing tools
100% gravity all the time without expending energy
possibility of an atmosphere in the event of a breach in the hull
heat...
(drawbacks)
more damage from space debris (rocks, manmade, and yes even sand)
possibly a feeling of being heavier at your feet than your head(feet would be quite near the center of the object while your head in comparison would be signifigantly further away) This occurs on Earth but is not noticiced as we are further from the center of mass.

Come to think of it, a saucer would be an appropriate shape for something like this (hooray for sci-fi giving visuals everyone can understand without the practical science included)

(major example: "stonehenge apocalypse" where they use a single device to try interrupting a signal across several spectrums to almost the point of emiting radiation...(radio,light,infared, ect)...it's total bs sometimes lol)

 

[dj cornbread]

I present one. In a spinning station of any practical size, the Coriolis Force will be present, and in fact, quite observable.

Would this force be what i described by feeling heavier at top than bottom?
Ive experienced this feeling first hand in a centrifuge... trying to stand sideways on an amusement park ride. (the one that the whole room spins and the floor drops away).
i also learned that gravity does not stop working with application of centrifugal force (and man did it hurt)

 

[dj cornbread]

I'm not sure that's necessarily true... consider VASIMIR for instance. I think my point about a black hole is that it can scale beyond our capacity to manage it by its very nature. Even antimatter would be devastating, but it would annihilate, killl everyone... the end! A black hole wouldn't explode... in fact it would persist and potentially GROW. I agree with you in general, but a black hole is a unique... object... and anything that has the capacity to scale between microscopic and galactic is fundamentally dangerous in ways no other technology I can think of is.

a black hole is not something that can be created (by other than natural methods)
it would be an impossibility to instantly create a "mini black hole"
a black hole is an area of mass that is dense enough that it's effect on gravity is so strong light cannot break orbit (tho this also allows for light to break the speed of light barrier)

without the available mass a true black hole would be feasibly impossible. there may be some mathematical trick to make it occur on paper, but, I'm thinking that equation making it possible does not account for the nearly unmeasurable amount of mass surrounding the "mathematical" anomaly... much like the $10 and 3 tennants trick.

 

[DaveC426913]

Creating artificial gravity by rotational force, would make it hard to dock any external vehicle.

This is elementary. You dock at the hub. Never seen 2001?

Also the outward force would make outside repairs and first hand observations near impossible.

No, it would only make it as difficult as it would be to repair the underside of a highway overpass (without touching the ground.).

If you had something resembling jacks (the toy) it would be near impossible to travel to other compartments.

Why? It would be no more difficult than doing the same thing here on Earth.

If you were to use a tube... traveling fore and aft would be easy but if you were to have to walk port and starboard you'd be walking up hill (a bit tiring if your working) before anyone says it, i know a octagon would be better suited for this, but the principal is the same.

Why would you have to walk up any hill?

Even the act of moving around one compartment could throw off the balance of the station in a whole causing a wobble (not good)

Well, this is the first thing you've said that makes sense. Yes, a space station would want to be large enough that people walking around in it didn't adversly affect its rotation.

I do not know if this would effect the body over time, but, with gravity your being pulled more at your feet than your head.

The magnitude is zero for all but the best instruments.

with centrifugal force it is the opposite. I'm thinking this may cause issues with blood circulation.

Nah.

Best bet, actual gravity. (as far as a stationary body is concerned) use an extremely high density material (much like a black hole is small and dense)

This does not work. You'd have monstrous gradients between head and foot.

less worry about flying off the body or loosing tools

No, big risk of both, because the gradient is so high. For gravity to be only 100% at your feet, it might be orders of magnitude smaker at your head. i.e. Pick up a 1/2lb wrench from the floor - by the time you lift it to your eye level, it weighs 1/100th of a pound and goes flying out of your hand.

100% gravity all the time without expending energy

No. 100% gravity at a single altitude, high degree of variance in gravity everywhere else.

(major example: "stonehenge apocalypse" where they use a single device to try interrupting a signal across several spectrums to almost the point of emiting radiation...(radio,light,infared, ect)...it's total bs sometimes lol)

This string of words makes no sense at all. I can't tell what you're saying, let alone what it has to do with artificial gravity.

 

[nismaratwork]

Google... it teaches us, but it makes us so sad too...

http://en.wikipedia.org/wiki/Stonehenge_Apocalypse

...The conclusion is a race for possession of the device which controls both the pyramid in Maine and the electromagnetic terraforming machine at Stonehenge.

*shooting pain through head*

dj cornbread: You're wrong when you make sense, or at least applying scales oddly. I certainly haven't been advocating the notion of black holes as useable, and it may be that humans never create one. I'll give you one example of how you could make a stellar-mass black hole however:

Find a neutron (or whatever level of degeneracy) star VERY close to its Chandrasekhar Limit... then add mass through whatever means you can. This assumes that I'm right, and DaveC isn't (Not a great bet), and in fact we're not able to use some manner of technology to crush a soda-pop can past its Chandrasekhar Limit.

You clearly didn't read the thread, and you seem to be inventing things out of whole cloth.

 

[dj cornbread]

This is elementary. You dock at the hub. Never seen 2001?
I have, but the expense of energy would be too much to keep one part stable with another rotating, not to mention the transfer from stable to centrifuge (eigther a harsh transition, or an energy waste "gradual transition"

No, it would only make it as difficult as it would be to repair the underside of a highway overpass (without touching the ground.).
Is the underside of an overpass the darkness of space, and an almost never ending trip death? i would prefer the thought of splat=dead over suffocation, and your tools don't stop at the ground so you can retrieve them, nor can you ride to the store if you loose one to a car windshield.


Why? It would be no more difficult than doing the same thing here on Earth.
up would become down and you'd get quite disoriented between transition from one side to the next

Why would you have to walk up any hill?
look at a hampster wheel, the hapster running the circle is moving up an incline, now also take into account nourishment is usually (not plentifull) you'd get a bit tired a bit quicker, so the small inclines would make a large impact.


Well, this is the first thing you've said that makes sense. Yes, a space station would want to be large enough that people walking around in it didn't adversly affect its rotation.
small solution, computer controlled water ballasting

The magnitude is zero for all but the best instruments.
tho it is sill present none-the-less


Nah.
our bodies are wired for a specific planet(pull of gravity, atmospheric pressure ,average temperature, o2 mix) if you throw the slightest kink in that there are big consequences (ABC's most fragile systems and first checked by ANY "med") since the astronaut is not choking, and I am pretty sure pressure and o2 are fine, this would leave circulatory as the best option for something to go awry (specially in the brain or bones).

This does not work. You'd have monstrous gradients between head and foot.
I think i mentioned this

No, big risk of both, because the gradient is so high. For gravity to be only 100% at your feet, it might be orders of magnitude smaker at your head. i.e. Pick up a 1/2lb wrench from the floor - by the time you lift it to your eye level, it weighs 1/100th of a pound and goes flying out of your hand.
OK so i had a dense moment(pun intended) that would put a great kink in any plan... litterally light headed


No. 100% gravity at a single altitude, high degree of variance in gravity everywhere else.
kinda like standing on a pulsar (providing it was not moving so damn fast)


This string of words makes no sense at all. I can't tell what you're saying, let alone what it has to do with artificial gravity.
It was stating the type of physics people are learning nowadays, "hollywood physics" (tho i agree i do not state things well, I am more of a thinking in pictures kinda person, not words)

Quick question tho... since we are on the topic of artificial gravity... how can we even begin to discuss it? we do not know how gravity works yet, only what it does. like a crazy ex girlfriend... (you know what will happen but not why or how)... lol, i had to...

nismaratwork: this thread... most of it appeared a bit argumentitive, so, i did skim. and the wiki for that movie should say "ha, ha, you spent one,some-odd hours watching this..."
I was replying to whomever was using it for (i think) open ended acceleration or for use as a source of gravity... honestly I am on a 24 hour php/javascript/sql scripting binge (probably noticable in my use of these $rarr; () ← so i know I am leaving it up to whatever comes first in this no-sleep head of mine.)

As far as the "mini Black hole" goes, i think there is a distinct difference between the real thing and the "mini" compressing matter to a certain point happens in both, one is capable of continuing to grow by gravity the other is a temporary cesation (or 99.9% cessation, i forget) of all movement in a few atoms (the dark part meaning not that light is trapped by gravity but that for that moment they cannot expel any further energy, no electro magnetic field, to push away from other atoms, tho in a millionth of a second they are "released" from one another as unlike a true black hole there is not enough gravity to overcome this separation) oh, and the antimatter counterpart ditching town then being replaced, yadda, yadda... all I'm saying is there not one in the same, tho there are some similarities... (about the same as human/monkey similarities. tho, one can shape its surroundings, the other is (near) controlled by them, but, you get my drift. mini != gravity or potential energy)

ok time to sleep...whiew

cannot wait to come back and see this dissected like the last *sarcasm*

 

[DaveC426913]

Wait. you're got yourself in your quotes...

I have, but the expense of energy would be too much to keep one part stable with another rotating, not to mention the transfer from stable to centrifuge (eigther a harsh transition, or an energy waste "gradual transition"

No. It's quite easy and natural. It's even easier than how they do it in 2001.

1] Point your spaceship at the axial "garage" door. Station (and door) is rotating, spaceship is not.
2] Fly in (attitude jets) and stop (attitude jets), hovering with the station still rotating around you.
3] Turn your spaceship 90 degrees to the right. (attitude jets)
4] Extend your landing gear (wheels). You are now floating weightless above a runway that is moving slowly underneath you.
5] Lower your spaceship (attitude jets) until your wheels touch the runway.
6] Apply your brakes. You will spin up to speed, gaining artifical gravity as you go.

This has taken exactly 4 micro bursts from your attitude jets. The bursts that can be of arbitrarily small impulse (and fuel consumption). Larger impulses simply make your landing faster. At no time does the spacecraft have to use any fuel to compensate for any opposing forces.

our bodies are wired for a specific planet(pull of gravity, atmospheric pressure ,average temperature, o2 mix) if you throw the slightest kink in that there are big consequences (ABC's most fragile systems and first checked by ANY "med") since the astronaut is not choking, and I am pretty sure pressure and o2 are fine, this would leave circulatory as the best option for something to go awry (specially in the brain or bones).

if you throw the slightest kink in that there are big consequences

This is far too general a claim to be relevant.

this would leave circulatory as the best option for something to go awry

What does "best option" mean? Why must something go awry?

"If something were to go awry" is not at all the same as "something will go awry".

Quick question tho... since we are on the topic of artificial gravity... how can we even begin to discuss it? we do not know how gravity works yet, only what it does.

For the purposes of living on a space station who cares how it works - we only care about simulating it.

It was stating the type of physics people are learning nowadays, "hollywood physics"

Who is learning this? Do you know anyone? What does it have to do with the topic?

This is rhetorical; it has nothing to do with the topic. No need to elaborate.

 

[nismaratwork]

Quick question tho... since we are on the topic of artificial gravity... how can we even begin to discuss it? we do not know how gravity works yet, only what it does. like a crazy ex girlfriend... (you know what will happen but not why or how)... lol, i had to...

nismaratwork: this thread... most of it appeared a bit argumentitive, so, i did skim. and the wiki for that movie should say "ha, ha, you spent one,some-odd hours watching this..."
I was replying to whomever was using it for (i think) open ended acceleration or for use as a source of gravity... honestly I am on a 24 hour php/javascript/sql scripting binge (probably noticable in my use of these $rarr; () ← so i know I am leaving it up to whatever comes first in this no-sleep head of mine.)

As far as the "mini Black hole" goes, i think there is a distinct difference between the real thing and the "mini" compressing matter to a certain point happens in both, one is capable of continuing to grow by gravity the other is a temporary cesation (or 99.9% cessation, i forget) of all movement in a few atoms (the dark part meaning not that light is trapped by gravity but that for that moment they cannot expel any further energy, no electro magnetic field, to push away from other atoms, tho in a millionth of a second they are "released" from one another as unlike a true black hole there is not enough gravity to overcome this separation) oh, and the antimatter counterpart ditching town then being replaced, yadda, yadda... all I'm saying is there not one in the same, tho there are some similarities... (about the same as human/monkey similarities. tho, one can shape its surroundings, the other is (near) controlled by them, but, you get my drift. mini != gravity or potential energy)

ok time to sleep...whiew

cannot wait to come back and see this dissected like the last *sarcasm*

You need to read a lot, stay in school, and stop posting for the sake of posting.

 

[jaiii]

Hi,

in march of 2006 publish ESA tim experiments about gravitomagnetick London moment who
can increasse decreasse mas.

Knew enybody somtime about it?

Thank and PF 2011

 

[nismaratwork]

Hi,

in march of 2006 publish ESA tim experiments about gravitomagnetick London moment who
can increasse decreasse mas.

Knew enybody somtime about it?

Thank and PF 2011

Can you post this... thing? From what I can decipher of what you've asked, the answer is that the kind of decrease in mass is... no.