Cheapest way to make artificial gravity?
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You are completely wrong! Einstein's principle is partly where the math for working out the gravity from black holes works.
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You are completely wrong! Einstein's principle is partly where the math for working out the gravity from black holes works.
Read up on relativity, Jimmy_C.
Tiberius is correct.
You can distinguish between gravity and accelaration due to the fact that, in an accelerating spaceship, the acceleration is uniform everywhere while in a gravitational field, the gravitational pull is weaker the further away from the mass you are.
That's why, these days, it's said the equivalence principle holds only in small physical systems, where one can't measure the difference in gravitational pull between two points.
Solar sail thing wrong. But those suits that require you to use your muscle's more, sounds good. Astronauts have claimed that not only is it hard to work up the motivation to exercise, but the fact that showers aren't common doesn't help. Maybe they can put some kind of oder block on the suits as well.
Maybe we should put that one to a test. And since we had black holes as an example, we'll use something nearly as exaggerated... really tall people (averaging 186,000 miles tall).
We load these people onto a spaceship, feet on the deck (towards the engines), and then fire the engines. Is acceleration uniform everywhere in the spaceship? Are these people feeling the same acceleration for both their heads and feet?
The problem that most people seem to forget is that the force we associate with gravity is the ground pushing up on us. Without the ground (and air) we would be weightless. We'd be following a path towards the center of the earth, but we wouldn't notice any forces on us.
We are only in an accelerated reference frame because we are pressed up against the earth. Similarly, in a spaceship we would only be in an accelerated reference frame by being pressed up against the deck. In both cases, the real force has to move through the floor, to your feet, through your body to your head for your head to feel the acceleration.
Now, how can the spaceship scenario be similar to the black hole scenario?
Lets return to our above average height people in their spaceship. And let say that they were accelerating at relativistic velocities (with out getting squashed)... and then they cut the engines. Their feet want to reach a constant velocity (now that the force from the deck is gone), but their heads don't know this yet. They would be stretched by the same types of forces that would stretch someone falling into a black hole.
The thing is (as Jimmy_C said), these are all covered by the exact same theory... the General Theory of Relativity. And all using the same math (tensor analysis on manifolds, Riemannian geometry).
More importantly, Einstein spent years trying to wrap his head around what it meant to be accelerating. And one of the first things he noticed was that in an accelerating elevator out in space, acceleration is not uniform everywhere because it has to be physically transferred to everything. Once physical contact is broken (an occupant of the elevator letting go of a ball for example), the object would no longer be accelerating (until it reestablished contact).
On the small scale (in the direction of travel) you can not tell these types of forces apart. On the large scale, a room that is very very wide, the forced pushing up from the floor on a planet would diverge while in a spaceship they would remain parallel.
General Relativity has been proven over and over again for the last 90 years.
Not only was Einstein not wrong, neither was Christopher.
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Shaw
http://en.wikipedia.org/wiki/Equivalence_principle
"An observer in a windowless room cannot distinguish between being on the surface of the Earth, and being in a spaceship in deep space accelerating at 1g. This is not strictly true, because massive bodies give rise to tidal effects (caused by variations in the strength and direction of the gravitational field) which are absent from an accelerating spaceship in deep space."
Acceleration would only be equivalent to an uniform gravitational field - which does not exist.
As it is, acceleration and gravity are only equivalent in small physical systems - where one can't measure the tidal forces.
But the acceleration WILL have the same value in every part of the ship it reached.
The speed of two different parts of the ship will be different, yes, but the acceleration - the rate of change in speed - will be the same throughout the accelerating ship.
http://en.wikipedia.org/wiki/Equivalence_principle
"An observer in a windowless room cannot distinguish between being on the surface of the Earth, and being in a spaceship in deep space accelerating at 1g. This is not strictly true, because massive bodies give rise to tidal effects (caused by variations in the strength and direction of the gravitational field) which are absent from an accelerating spaceship in deep space."
Acceleration would only be equivalent to an uniform gravitational field - which does not exist.
As it is, acceleration and gravity are only equivalent in small physical systems - where one can't measure the tidal forces.
When the starship starts accelerating constantly, this acceleration will be transmitted through the ship at the speed of light. You will have the back part of the ship that is accelerating and the front part, where acceleration has not reached yet.
But the acceleration WILL have the same value in every part of the ship it reached.
The speed of two different parts of the ship will be different, yes, but the acceleration - the rate of change in speed - will be the same throughout the accelerating ship.
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Wikipedia is not a replacement or substitute for a solid education. If you don't know this subject well enough to discuss it without Wikipedia, then you don't know the subject well enough.
Sorry... no shortcuts allowed.
The statement of the Equivalence principle that you're referring to isn't the actual principle itself, more of an imperfect layperson's description. The proper form of the principle as actually formulated by Einstein does not contain the same error as the popular representation thereof. So no, Einstein was not wrong.
Besides, for the purposes of this discussion, the distinction you're pointing out is irrelevant. Because we're not talking about falling into a black hole, we're talking about artificial methods of creating weight and whether it's valid to describe the acceleration they produce as "artificial gravity." And in fact, if you're in a module that's being rotated to produce centrifugal "gravity," you will indeed feel a differential from head to foot, unless the radius of rotation is so large as to render your height trivial in comparison.
But magnetic sails could be accelerated far faster than solar sails.
lol, quite a can of worms I opened, wasn't it!
I am well aware that the idea of acceleration being the same as gravity is true, and the the problem lies with the analogy. If you have a two dimensional creature, like a really thin pizza, on the floor of the accelerrating rocket, he wouldn't be able to tell, because he would be entirely perpendicular to the direction of acceleration.
For the analogy to be really true, we'd need little tiny rockets attached to each cell in our bodies, each firing at a slightly different rate.
I am well aware that the idea of acceleration being the same as gravity is true, and the the problem lies with the analogy. If you have a two dimensional creature, like a really thin pizza, on the floor of the accelerrating rocket, he wouldn't be able to tell, because he would be entirely perpendicular to the direction of acceleration.
For the analogy to be really true, we'd need little tiny rockets attached to each cell in our bodies, each firing at a slightly different rate.
lol, quite a can of worms I opened, wasn't it!
I am well aware that the idea of acceleration being the same as gravity is true, and the the problem lies with the analogy. If you have a two dimensional creature, like a really thin pizza, on the floor of the accelerrating rocket, he wouldn't be able to tell, because he would be entirely perpendicular to the direction of acceleration.
For the analogy to be really true, we'd need little tiny rockets attached to each cell in our bodies, each firing at a slightly different rate.
I am well aware that the idea of acceleration being the same as gravity is true, and the the problem lies with the analogy. If you have a two dimensional creature, like a really thin pizza, on the floor of the accelerrating rocket, he wouldn't be able to tell, because he would be entirely perpendicular to the direction of acceleration.
For the analogy to be really true, we'd need little tiny rockets attached to each cell in our bodies, each firing at a slightly different rate.
ProtoAvatar
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Wikipedia is not a replacement or substitute for a solid education. If you don't know this subject well enough to discuss it without Wikipedia, then you don't know the subject well enough.
Sorry... no shortcuts allowed.
Shaw, you're welcome to read the peer-reviewed papers linked from that Wikipedia page - or other papers treating relativity - and confirm what I just told you in my previous post.
Your condescending "no shortcuts allowed" comment does not change in the least the fact that the information I wrote in my post is accurate, while your assertions - written without Wikipedia, of course - are NOT.
Wikipedia is not a replacement or substitute for a solid education. If you don't know this subject well enough to discuss it without Wikipedia, then you don't know the subject well enough.
Sorry... no shortcuts allowed.
There was no reason to read your post beyond the Wikipedia link... and I didn't.
I'll state it again... Wikipedia is not a replacement or substitute for a solid education. If you don't know this subject well enough to discuss it without Wikipedia, then you don't know the subject well enough.
After you have taken the time to learn this material, I'd be happy to discuss it further. And that means getting a good foundation first (if you haven't taken it yet, a classical differential geometry course is a good starting point... followed by calculus on manifolds, differentiable manifolds and Riemannian geometry, before taking a general course on General Relativity... assuming, of course, that you've taken courses on mechanics and electromagnetism).
As for taking a condescending position... if you can't take it, don't dish it out. Your "Read up on relativity" comment to Jimmy_C was just as condescending... with the notable difference being that I've earned the right to be condescending and you have not (yet).
If you follow my advice (including staying away from Wikipedia), I promise that really learning General Relativity will be well worth the effort.
And that is honest advice. You showed promise in our previous discussion (Dimensions of Time...?), and if it had been anyone else I wouldn't have even wasted time with this reply.
But there are no shortcuts.
There is nothing to win. As I said, Wikipedia is not a replacement or substitute for a solid education (or good research).
But I'd point out that I know of at least two Wikipedia articles that use me as a reference and a third that quoted me verbatim (without attribution).
So if I'm a good enough reference for Wikipedia, I'm most likely not missing anything avoiding using it. Specially considering that I've seen some really bad information on Wikipedia that stayed there for more than a year. Wikipedia has (with me) a bad reputation for re-enforcing erroneous information.
If I know something, I don't need Wikipedia. If I don't know something, I'm better off avoiding Wikipedia. And if I think that someone's knowledge on a topic seems based on Wikipedia, then the discussion isn't worth my time.
You are joking of course. This is a public messageboard where anyone can express an opinion about anything. It's just like, well y'know it's just like real life.
Besides, everyone knows science is decided by popular opinion. Gravity only exists because we believe it does, man.
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Fleet Captain
There is a big difference between my comment about Jimmy_C and your comment about me, Shaw.
You see, Jimmy_C was wrong in its statements - and you, curiously, supported his erroneous asertions.
I wasn't wrong.
You 'earn' the right to 'dish' condescendence out ONLY when you are right and your opponent is wrong.
Not the other way around, Shaw.
The difference here is that you're an 18 year old kid with only a high school education. Wikipedia is a good starting place for you to pickup information on a subject and then has references for you to learn more detailed information from. Shaw on the other hand IS one of the references used on wikipedia and already has a better grasp on the subject of conversation here (and the mathematics behind it) than a large portion of the contributors to Wiki.
Magnetic sails, I honestly don't know enough about to answer if they would be useful for crewed ships on inner solar system missions. My gut feeling is they wouldn't be. I am not sure what your comment about bypassing the moon is about???
And so? No reason to be an arrogant ******* about it. He didn't even try to discuss it and correct things that the article might be wrong about. Instead he just went like "oh, you cite wikipedia, you're not worth my time"
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