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Greetings I learned some time ago from a source I now do not recall the astronauts aboard the Space Station do not experience micro-gravity or zero g in the expected sense In fact it was explained the force of Earth's gravity at that altitude is in fact just under .9 of the surface They are merely falling along w/ the station So it is no different than the "Vomit Comet" It would be nice if the popular press would explain it so Kind Regards - Cheerio
My sympathies to the SPAM moderator
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PaltryProgrammer wrote: It would be nice if the popular press would explain it so
You think the "journalists" working for the popular press are in a position to explain anything? That's cute.
I can't find the obligatory XKCD comic on that very topic...
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Relatively, the 'experienced' gravity is 'zero' - so your point is kinda silly. Yes, they are in Earth's gravity well, but 'zero gravity' is a good description of the perceived effect.
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I think “free fall” is the better term.
You need to make it to the lunar LaGrange points for a closer approximation of zero G. (You are still probably free falling around the earth, the moon, and the sun all at the same time, though. Orbits are tricky.)
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No you don't.
Any object in a ballistic trajectory. - a shell, a missile after it finishes its acceleration phase, a satellite (artificial or natural) is in "zero gravity" (neglecting atmospheric effects for the shell).
Having mass, they of course generate their own "gravitational" field, but that's another, much hairier story. In fact even the generalised TWO-body problem does not have an analytical solution in General Relativity; all solutions are calculated using numerical approaches.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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“Side fall” then?
If they weren’t moving that fast, they would start falling. The kind of “free fall” that ends in a splat. (Or for earth, burn up in the atmosphere)
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You are asking the wrong question. From the POV of General Relativity, the question isn't "why things fall", but "what makes them stop when they hit the ground?"
A less facetious answer would be that an massive object "warps space-time" around it. The objects in orbit are moving along a path (I.e. both position and velocity) in that "warped space-time" that avoids intersection with the massive object.
(If you want a more quantative answer, study Physics to reach the level of confusion enjoyed by most physicists...  )
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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space station travels roughly 17,150 miles per hour. Orbiting earth once every 92 minutes. The astronauts float in "air" at that speed.
people in this thread can debate the gravity sh*t all they want, I think what I just posted is freaking cool AF.
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Yes, if the earth rotated at that speed people on the equator would be able to float above the ground.
“That which can be asserted without evidence, can be dismissed without evidence.”
― Christopher Hitchens
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How would "real" zero gravity be different from what the Space Station guys experience?
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Greetings According to Newton's law - Cheerio
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It isn't.
According to General Relativity's Principle of Equivalence, a local acceleration may be treated as a "gravitational" field, and vice versa.
No acceleration == no "gravitational" field.
(For those that claim that they are not being accelerated while sitting in a chair here on Earth, that is because powerful non-"gravitational" forces are acting in the opposite direction. In General Relavivity, it is not "why things fall" that requires explaining, but why they stop when they hit the ground...)
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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The old “elevator” thought experiment.
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Exactly.
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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You've said this twice
In General Relavivity, it is not "why things fall" that requires explaining, but why they stop when they hit the ground
I agree with you that "gravitation" is just one of many forces and the balancing of forces is what makes the magic of "zero gravity" (no effective forces in a singular direction), but isn't that because F = ma and not because E = mcc?
We stop when we hit the ground because the ground has reciprocating force (known as Normal force) against that which strikes - it has momentum which is conserved. Relativity comes into play in the conversion of kinetic energy into heat at the impact, but is it a factor in the fall?
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Were spacetime around mass-bearing objects not warped, all movement would be at constant velocity (speed + direction). It is only the warping of spacetime around mass-bearing objects that causes movement to appear accelerated to us.
Note that any object moving freely in warped spacetime does not feel any acceleration effects. This is true whether we perceive it as "falling" (and about to splatter on the ground), whether we perceive it as "in orbit", or whether we perceive it as moving at above "escape velocity".
What happens when an object hits the ground is that non-gravitational forces (electrostatic repulsion between atoms) start acting. It is then that the object will perceive acceleration, and part of its energy may be turned into other forms (usually heat).
Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.
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> What happens when an object hits the ground is that non-gravitational forces (electrostatic repulsion between atoms) start acting. It is then that the object will perceive acceleration
Yes.
And since all mechanical and chemical interactions are ultimately due to the Electromagnetic Interaction, that's the only interaction the body can sense. The presence or absence of a Gravitational Field is irrelevant to the sensation of weight. "Weightiness" is entirely due to an unbalanced electrostatic repulsion.
(An equal-and-opposite vice-like compression doesn't provide any sense of self-weight or any up-down reference; it doesn't orient the vestibular system.)
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Depending on your frame of reference...? 
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According to Hitch Hikers Guide to the Galaxy: There is an art to flying, or rather a knack. The knack lies in learning how to throw yourself at the ground and miss. ... Clearly, it is this second part, the missing, that presents the difficulties.”
—The Guide[src]
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AFAIK, a body is considedered to be in a micro-G situation when the sum of all forces acting on it, except gravitational forces, result in something lower than a certain limit, let's say, 9.8x10-6 m/s2.
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The main difference between "being in a 0 gravity field" and "orbiting in a station around earth" is that in the 2nd case, you are spinning at the same rotational speed as the station so Coriolis force applies and if you throw an object to a friend in the station, it will not follow a straight line (as the object would do in the first case) but a curve.
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i was one of the first customers [^].
Something went wrong with their face-recognition entry, but, it only took me an hour to reset my password and security questions. It was like so cool they played my favorite music, Samuel Barber's Adagio (Hauser on the cello), while i waited, to help me keep my chill. And, when my favorite brew, hazelnut spiked latte, popped out of a little orifice i hadn't noticed ... wow !
The greeter-droid apologized profusely for the delay, and told me i had a US $5 discount on whatever i purchased today. Then it asked me what i was shopping for.
i said: "A sequined spandex tank-top like Gary Glitter used to wear."
Droid: "What size, what color ?"
Me: "US XL, black, multi-color sequins."
The Droid took 15 seconds to respond: "Please look at the images on the display wall panel ... eye-tracking will show the image you are looking at on the SuperScreen underneath the wall panel; you can tell Alexa to freeze the current image, to move the items on the wall panel right, or left ... we see you have already earned "Expert" status for using Alexa ... any questions, just ask,"
Me: "Is there a Gary Glitter official groupie tank-top available ?"
Droid: "The pictures on the wall panel are arranged from left-to-right, prioritized in terms of similarity to your specification. In this case, there is no 100% match in stock."
Me: "Is that Bowie in the first picture ?"
Droid: "Yes, we can have that here for you to try on in five minutes."
Me: "Okay."
Me: "Wait ... is that tank-top, by any chance, made by Uighur Muslims in Xinjiang who are now being 're-educated' ?"
Droid: [after 15 seconds] "We are sorry Sir, but, per our agreement with China, goods are supplied through wholesalers who are prevented from disclosing factory locations in China."
Me: "Okay ... can you show me models made outside China, Rwanda, and the Congo ?"
Droid: [wall panel display updates] These are what we have."
Me: "i'd like to try on the first one."
Droid: "We are pleased to tell you that model can be here in fifteen minutes, and, because you have to wait more than ten minutes, you will receive a complimentary beverage."
[fifteen minutes later, re-caffeinated by another latte with a shot of Red Bull, i am escorted to a dressing room ... i notice the absence of mirrors.]
Alexa: "Welcome ! Your body-scanning level permission status is set to 'Full Monte' ... Please confirm that."
Me: "Confirmed."
[i take my shirt off, and put on the tank-top]
Alexa: "That's very tight around your sides ... you've added more fat than in our last scan: would you want an XXL ? While custom tailoring is possible, there is a 50% surcharge, and a waiting period of up to sixty days."
Me: "what would JSOP say about this shirt ?"
Alexa: "JSOP on CodeProject ?"
Me: "Yes, the one, and only."
Alexa; "Our personality inference engine suggests JSOP would say: 'that's for pussies !'"
Me: "That makes me sure i want it ! Confirm order."
Alexa: "Order confirmed, your AmazoninianBitCoin account has been billed."
Alexa: "Before you go, may we bring a possible health issue to your attention ?"
Me: "Sure."
Alexa: "Your slightly slurred speech, and somewhat irregular slow heartbeat, as well as intermittent movements suggesting loss of balance, and unusually low body temperature ... all point to extreme stress, and a possibility pf hypothyroidism. Your medical records show you have not had a thyroid test for three years ... can we help schedule an appointment with one of our certified family physician partners, given your previous one is dead ?"
Me: "No, thanks: all this physical stuff is just stress related ... the divorce; a son busted for drugs; trying to upgrade to Windows 11 ..."
Alexa: "We understand; could we offer you a free consultation with one of our board-certified psychotherapist partners ... one who lives within 22 minutes average driving-time from your current place of residence ?"
Me: "No, thanks: i'll stick with acupuncture, and binge watching tv series i hate ..."
Alexa: "We understand; however, we note your current attorney's billing fees are 30% higher than the average of our Amazon certified divorce lawyers, and, your attorney has one of the lowest consumer satisfaction ratings we ever calculated."
Me: " ... mmmm ... i'll think about that one."
Alexa: "We understand; however, we note your son's bail bondsman has quoted you fees more than 50% higher than our Amazon certified bondsmen partners would charge."
Me: "i'm letting the kid rot in jail for a while ... teach him a lesson !"
Alexa: "We understand."
Me: "i'm surprised you're not offering me new PC's with Win 11 !"
Alexa: "Sir, We do not carry Windows OS PC's: they are unreliable, over-priced, have significant security issues."
Me: "Wow ... are you channeling Bezos ?"
Alexa: "We can say with confidence that every human employee here, and every sentient AI, like the one you, and two million other people, are talking to now ... share this opinion !"
Me: "Alexa: logout"
Alexa: "When you exit the store, you will be logged-out. Please pick-up your AR-15 semi-automatic weapon, and Kevlar vest, at the secure storage room first; the magazine (and the bullets removed from the magazine, in a protective pouch) will be delivered to you through the same portal you received your first latte from."
«The mind is not a vessel to be filled but a fire to be kindled» Plutarch
modified 23-Sep-21 9:04am.
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