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re: Astronaut who spent 197 days on the ISS shows how hard it is to walk again
Posted on 3/22/19 at 10:40 pm to DavidTheGnome
Posted on 3/22/19 at 10:40 pm to DavidTheGnome
Einstein’s Equivalence Principle
In effect, the equivalence principle is more a great analogy than it is a scientific fact. For it to be singularly true, all of the factors for both gravity and acceleration would have to be the same. They’re not.
quote:
So the original equivalence principle, as described by Einstein, concluded that free-fall and inertial motion were physically equivalent. This form of the equivalence principle can be stated as follows. 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. The room, therefore, should be small enough that tidal effects can be neglected.
In effect, the equivalence principle is more a great analogy than it is a scientific fact. For it to be singularly true, all of the factors for both gravity and acceleration would have to be the same. They’re not.
0
Posted on 3/22/19 at 10:51 pm to liz18lsu
quote:
Looks like a drunk OT’er
Hum... has anyone ever gotten drunk in space?
Posted on 3/22/19 at 11:23 pm to Kentucker
I’m not mistaking anything actually 
I learned what the difference between centrifugal and centripetal force was freshman year of college, but appreciate the lecture and stand by what I said. The claim is that you can generate artificial gravity from the perspective that the human body isn’t going to differentiate between a constant force imparted to it, be it by the force of gravity or by centripetal forces. The claim is not that we can generate a gravitational field via a symmetrical rotating object. It seems that’s where you might be getting held up.
I also understand the difference between Newtonian models of gravity as a force and Einstein’s models where it is curvature of spacetime pretty well as part of my education combined with a general love of science, so while I do understand where you are coming from, I have to reiterate you are wrong about not being able to simulate gravitational acceleration with a rotating reference frame.
I learned what the difference between centrifugal and centripetal force was freshman year of college, but appreciate the lecture and stand by what I said. The claim is that you can generate artificial gravity from the perspective that the human body isn’t going to differentiate between a constant force imparted to it, be it by the force of gravity or by centripetal forces. The claim is not that we can generate a gravitational field via a symmetrical rotating object. It seems that’s where you might be getting held up.
I also understand the difference between Newtonian models of gravity as a force and Einstein’s models where it is curvature of spacetime pretty well as part of my education combined with a general love of science, so while I do understand where you are coming from, I have to reiterate you are wrong about not being able to simulate gravitational acceleration with a rotating reference frame.
This post was edited on 3/22/19 at 11:47 pm
Posted on 3/22/19 at 11:35 pm to Ross
You are debating a guy who thinks that we have a responsibility or an obligation to insure that artificial intelligence is reality when the biological human species is extinct. Not sure why it matters why that has to happen and for what reason , but apparently, we are responsible for making that happen. I would like to hear what the implications are if that doesn’t happen, and again, why it is relevant to our present reality.
Posted on 3/22/19 at 11:41 pm to DavidTheGnome
This is why a mission to Mars and back is a long long long ways away. They will have the bone density of an 120 year old women with osteoporosis.
Posted on 3/22/19 at 11:56 pm to Langland
2030s is still the goal. SLS is running behind but still might get there.
Posted on 3/23/19 at 12:00 am to DavidTheGnome
Should've asked for an attorney and submitted to field sobriety tests.
Posted on 3/23/19 at 12:13 am to Tortious
Are we seriously letting cripples be astronauts now
Posted on 3/23/19 at 8:02 am to DavidTheGnome
I bet that dude was thinking about beer and pussy the whole time he was up there.
This post was edited on 3/23/19 at 8:14 am
Posted on 3/23/19 at 8:10 am to DavidTheGnome
I bet he could walk a little better after a few beers in him
Posted on 3/23/19 at 10:15 am to Ross
quote:
I’m not mistaking anything actually
Sorry, I’m not trying to trigger you. If any of my responses seem brusque, it’s not intentional. I love discussing science and respect you and anyone who participates. I’m a devoted reductionist so I look for the base components of everything.
Thanks for engaging me in this most interesting topic.
quote:LINK
Centripetal force is defined as, “The component of force acting on a body in curvilinear motion that is directed toward the center of curvature or axis of rotation,” while centrifugal force is defined as, “The apparent force, equal and opposite to the centripetal force, drawing a rotating body away from the center of rotation, caused by the inertia of the body,” according to the American Heritage Dictionary.
To me, centrifugal “force” is an obvious illusion. It’s not a force at all, just energy applied to a stationary object in an environment having gravity.
Now, the definitions above say that centripetal force is equal and opposite to the cenrifugal force. Aren’t they both apparent forces, despite the article’s statement to the contrary about the centripetal force? And aren’t they both dependent upon gravity?
quote:
I learned what the difference between centrifugal and centripetal force was freshman year of college, but appreciate the lecture and stand by what I said.
Again, my apologies for brusqueness. I’ll try to soften some of my language.
quote:
The claim is that you can generate artificial gravity from the perspective that the human body isn’t going to differentiate between a constant force imparted to it, be it by the force of gravity or by centripetal forces.
Yes, that’s the claim and my contention is that neither centripetal or centrifugal forces can occur outside of gravity. Einstein said that gravity is constant acceleration, and I see how he related the two. For us to exist, that constant acceleration is countered by the electromagnetic force, the strong nuclear force and the two weak nuclear forces. They hold everything together.
He used the analogy of a constantly accelerating body to illustrate gravity. A person who is in a spaceship that is constantly accelerating at 1g cannot distinguish between earth’s gravity and the acceleration.
So, for “artifcial gravity” to be achieved, doesn’t the rotating container in a centripetal machine have to be experiencing constant acceleration? How else can a person inside it perceive the effect? If only a constant speed is maintained, won’t the person merely achieve the same speed and float free in the container?
This post was edited on 3/23/19 at 10:48 am
Posted on 3/23/19 at 10:45 am to Dick Leverage
quote:
You are debating a guy who thinks that we have a responsibility or an obligation to insure that artificial intelligence is reality when the biological human species is extinct.
I did not say extinct. You made that assumption. Also, we’re not debating. This is a discussion board only. Discussion is fun. Debating is serious business. I never get that serious about life.
quote:
Not sure why it matters why that has to happen and for what reason , but apparently, we are responsible for making that happen.
I meant we have the responsibility in the context of being something that we should do, rather than being something that we might do without intending to do so. I think we are wise enough to recognize our limitations as biological meatbags and that if we are to continue the spread of life into the Universe, we must create a successor species of non-biological life that can physically withstand the rigors of space travel.
quote:
I would like to hear what the implications are if that doesn’t happen, and again, why it is relevant to our present reality.
Look at the history of our evolution and then project our species forward into the future. What do you see? Have we not “conquered” most, if not all, of the evolutionary factors that exposed us to “survival of the fittest?”
We have, with our great brains, blasted away all of those constraints. For example, we don’t have to adapt to our environments on earth anymore. Rather, we adapt our environments to our needs.
We have not evolved to regulate our numbers dependent upon our resources, however. Our use of the earth and its resources to create more of our species is in runaway mode. There can be only one outcome as a consequence of this evolutionary defect, a near-future collapse of our species. I don’t mean extinction. Just a catastrophic fallback to a population size that the earth can carry.
Fortunately, we have tme to create a successor species that won’t be dependent upon the same resources that we need. We are in a golden age of technology and scientific discovery. I think it’s incumbent upon us to create A.I. and to send it out into the Universe as an ambassador of earth intelligence.
Posted on 3/23/19 at 10:47 am to Kentucker
quote:
To me, centrifugal “force” is an obvious illusion. It’s not a force at all, just energy applied to a stationary object in an environment having gravity.
Now, the definitions above say that centripetal force is equal and opposite to the cenrifugal force. Aren’t they both apparent forces, despite the article’s statement to the contrary about the centripetal force? And aren’t they both dependent upon gravity?
Centrifugal force is a "fictitious force", an artifact of human perception. It is in this way similar to the Corliolis force, which is likewise fictitious and a consequence of existing in a rotating reference frame. Neither of these forces exist in the traditional sense that can be derived from an interaction (otherwise stated it doesn't result from an energy exchange). However, both of these phenomena exist in perception as a result of forces that can be stated in terms of physical interactions that ascribe to Newton's Laws.
The illusory centrifugal force is, as you stated, "opposite" to the centripetal force. The centripetal force exists as a reaction between either walls (a normal force) or tension of some sort and is quantifiable as the force required to impart the necessary acceleration of an object to allow it to turn in a rotating trajectory. In a non-relativistic reference frame, this is extremely simple to derive and as you probably already know you can show that
Fc = m*(v_T^2 / R), where
Fc is centripetal force
m is mass
v_T is tangential velocity
R is radius of curvature
So, as I see it, no, the centripetal force is not dependent upon gravity. It is the force imparted to an object with some inertia that caused it to turn and rotate around an axis. This force can be achieved in a number of ways, but the most trivial examples are a ball on a string, where it is the tension on the string pulling the ball inwards, or in our space travel example, a station rotating such that the normal force between the human and the outer wall continuously rotates the human around. The centripetal force always acts radially inwards, and because of that if you tune the radius of curvature and the RPM in which the station spins, you can get to 9.81 m/s^2 and achieve artificial gravity.
The reason it is important to limit RPM and make the radius of curvature longer is because you don't want noticeably differences in your centripetal force between your head and your feet (note that the centripetal force is inversely proportional to the radius, so you want to make the length scale of six feet (or whatever the average human is) negligible compared to the radius of curvature.
quote:
Yes, that’s the claim and my contention is that neither centripetal or centrifugal forces can occur outside of gravity.
I disagree, and wholeheartedly so if we stay within the realm of Newtonian mechanics in which gravity and centripetal force are two isolated concepts.
quote:
He used the analogy of a constantly accelerating body to illustrate gravity. A person who is in a spaceship that is constantly accelerating at 1g cannot distinguish between earth’s gravity and the acceleration.
So yeah that's true, but where I think you are going off topic is that is linear acceleration and we are talking about rotation. Which you do address and I'll get to in your next point:
quote:
So, for “artifcial gravity” to be achieved, doesn’t the rotating container in a centripetal machine have to be experiencing constant acceleration? How else can a person inside it perceive the effect? If only a constant speed is mainained, won’t the person merely achieve the same speed and float freein thefontainer?
No, because constant tangential speed around a circle does generate constant acceleration, it's just pointing radially inwards (because acceleration is simply change in velocity, which is speed and direction, not just speed). Your linear ship required a constant linear acceleration, which clearly isn't tenable. The beauty of the rotating design is it really only does require constant rotational speed in order to function.
You do need some sort of a motor to overcome losses due to friction or some other outside noise, but you do not need your rotating ship to constantly accelerate like you would a linear ship to impart a constant 1G load to its crew.
Hate referencing wikipedia, but give their article on artificial gravity a read. They talk almost exclusively about the merits of a centripetal force based design with the prototype concepts included.
This post was edited on 3/23/19 at 11:00 am
Posted on 3/23/19 at 10:57 am to DavidTheGnome
This was proven to be staged. FYI everybody.
Good lord Ross^ go get laid
Good lord Ross^ go get laid
This post was edited on 3/23/19 at 11:00 am
Posted on 3/23/19 at 11:01 am to ScaryClown
quote:
Good lord Ross^ go get laid
took 15 minutes to type and had one math equation in it
you can go get fricked
Posted on 3/23/19 at 11:15 am to Ross
quote:
The centripetal force always acts radially inwards, and because of that if you tune the radius of curvature and the RPM in which the station spins, you can get to 9.81 m/s^2 and achieve artificial gravity.
Well, we’ll just have to agree to disagree, I suppose. I will add, however, that there’s a reason artificial gravity experiments in space were largely abandoned after the Gemini 11 mission in 1966. I suspect the conclusion was that it’s not possible.
Posted on 3/23/19 at 11:21 am to Ross
quote:
Hate referencing wikipedia, but give their article on artificial gravity a read. They talk almost exclusively about the merits of a centripetal force based design with the prototype concepts included.
Wikipedia is fine as a quick reference quide. Its gold is located in the references section at the end of every article. I really don’t understand why some people look down their noses at Wikipedia. It’s a legit encyclopedia.
Posted on 3/23/19 at 11:25 am to Kentucker
I'm not sure where the disagreement stems from to be honest, but alright.
The reasons it was abandoned after Gemini II are numerous, I think. Experiments in microgravity became more of a focal point, to achieve artificial gravity is a costly effort, and there are other logistical challenges like even if you get the constant centripetal force, Corliolis effects of anything not restrained by the walls of the station will be a challenge (throwing a ball to a crewmate but the ball instead vears off to the side instead of following the trajectory you expect).
Gemini II revealed that it was possible though, they generated 0.0005 g with 0.15 revolutions per minute.
But I guess that's more of a question of its practicality, not if it is ultimately possible, which I believe it is and I also fall in the camp that thinks it is something we will need to develop for future large scale missions we will be looking at.
The reasons it was abandoned after Gemini II are numerous, I think. Experiments in microgravity became more of a focal point, to achieve artificial gravity is a costly effort, and there are other logistical challenges like even if you get the constant centripetal force, Corliolis effects of anything not restrained by the walls of the station will be a challenge (throwing a ball to a crewmate but the ball instead vears off to the side instead of following the trajectory you expect).
Gemini II revealed that it was possible though, they generated 0.0005 g with 0.15 revolutions per minute.
But I guess that's more of a question of its practicality, not if it is ultimately possible, which I believe it is and I also fall in the camp that thinks it is something we will need to develop for future large scale missions we will be looking at.
This post was edited on 3/23/19 at 11:35 am
Posted on 3/23/19 at 12:00 pm to Ross
quote:
I'm not sure where the disagreement stems from to be honest, but alright.
I think it stems from whether gravity causes the centripetal effect. I think you already acknowledged that it isn't a centripetal force. As I see it, an effect is dependent upon one of the natural forces or gravity, which is also just an effect of mass warping spacetime.
quote:
Gemini II revealed that it was possible though, they generated 0.0005 g with 0.15 revolutions per minute.
That was the measurement but I would contend that any margin for error in the measuring equipment would negate that as a firm conclusion.
quote:
But I guess that's more of a question of its practicality, not if it is ultimately possible, which I believe it is and I also fall in the camp that thinks it is something we will need to develop for future large scale missions we will be looking at.
And I'm firmly in the smaller camp that thinks we are forever bound to this planet because of evolutionary constraints. Even if artificial gravity is proven to be possible and practical, through experimentation, there are a host of other issues that will prevent us traversing the Universe in our biological forms.
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