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Unrelated question - would you feel acceleration in space from a sudden impulse of gravity ?

Discussion in 'General' started by Digi, Mar 24, 2014.

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  1. Digi Senior Engineer

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    I'm just curious about something in reality, not game related.

    I know that humans (and not only) can feel acceleration and it can be harmful if it's too severe.

    Let's say you're in space somewhere where there's no gravity anywhere near you and you're completly still... and then a sudden gravity field of serval hundred Gs suddenly pulls you in a direction... would you feel that or it would be so spread out throught your body that you'll feel nothing ?

    Might be a stupid question, but if so, I'd like to be enlightened.
     
  2. Shiliski Apprentice Engineer

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    100 Gs, sudden or not, would put a terrible strain on the body.

    We can barely handle 7 Gs without losing consciousness. Women have it slightly better in that regard than males do, but with too many Gs we'd just flat out die. This comes up IRL when people fly jet fighters that are capable of some enormous G-strain.

    Astronauts actually have to take tests that measure how many Gs they can physically take. You may have seen the little merry-go-round pod thing in movies before. This is what that does.

    100 Gs... the real question here wouldn't be "would you feel it at all". The real question here would be "would you feel that before you died".
     
  3. RazersEdge Apprentice Engineer

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    Well considering that many Gs wouldn't happen all of a sudden it doesn't matter. A level of gravity that high would cause a differential shear more than likely which would tear you apart and kill you.
     
  4. Digi Senior Engineer

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    I see, thanks for your replies :p
     
  5. piddlefoot Senior Engineer

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    Humans can tolerate localized g-forces in the 100s of g's for a split second, such as a slap to the face. Sustained forces above about 10 g can be deadly or lead to permanent injury, however, although there is considerable variation among individuals when it comes to their tolerance. Race car drivers have survived instantaneous accelerations of up to 214 g during accidents. In rocket sled experiments designed to test the effects of high acceleration on the human body, Colonel John Stapp in 1954 experienced 46.2 g for several seconds. Usually, accelerations beyond 100 g, even if momentary, are fatal.
     
  6. Azan Trainee Engineer

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    You wouldn't feel anything if the gravitational field is uniform enough as all parts of your body would be accelerated at the same rate and as such have no stresses between them. You would only feel something if the gravitational field had significant drop off so that different parts of your body were experiencing different amounts of acceleration.
     
  7. tomxp411 Apprentice Engineer

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    I'm going to back Azan's answer: If you were in open space, and the field was uniform, you would not feel a thing.

    You would feel the effects if the gravitational gradient was extreme enough that the difference in g-force between your head and toes was noticeable (probably something like .1g), and you would definitely feel it if you collided with an object that was not being accelerated - like the ground.
     
  8. extraammo Senior Engineer

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    Exactly! This is how I theorize internal inertial dampeners would work. The same technology for artificial gravity would be used to cause a uniform pull on the contents of a ship so that nothing is damage during maneuvers. Basically a seatbelt for every atom in the field.
     
  9. iron_dinges Apprentice Engineer

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    Brilliantly said.

    Adding to this; the reason astronauts and jet pilots feel these harsh effects is because they are being pushed against their seats.
     
  10. NutterChap Apprentice Engineer

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    Not only. Consider the blood in your vessels. If you make a tight high-speed looping, all blood will rush out of your brain into your toes. That is why fighter pilots wear inflatable trousers.

    As long as you are not being supported by something that goes out of the direction of the G-force, you will notice a whole lot of nothing. Drop tests on the moon showed that a feather drops as fast as a lead ball: acceleration by gravity is the same for everything, when there are no more external factors left in the equation. As soon as you make contact with something that isn't at your current speed or direction (has to decelerate or accelerate) you will notice it. In a gravity field of 100G, as soon as you make contact with a support (the deck of your ship for example) you are going to be the new pancake look-a-like champion.

    Another nice quote in this context: "It is not the falling that kills you, it is the sudden stop at the end.". Having a lack of support, such as during falling or being suspended between the earth and the moon, you have the exact same feeling: weightlessness. Try bungee jumping or even better: a parabolic flight!
     
  11. Digi Senior Engineer

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    So gravity can't accelerate you faster no matter the condtions ? In which case you can't possibly feel it.
     
  12. extraammo Senior Engineer

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    Nah, the point is that you can't feel free fall in space. Normally, forces act on the outside of your body, causing your different densities and fluids to move around. Extreme external forces can be lethal. Gravity, on the other hand, acts on every single atom in your body equally. So if gravity is the only force, meaning free fall without atmosphere, you won't feel it.
     
  13. killerdude Apprentice Engineer

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    Long story short, Yes, You would, Acceleration is Acceleration, Regardless of what is causing it.

    If something, Anything, Cause you to move in a certain direction really fast suddenly, You'd feel it, Depending on how strong the force is, It might also kill you near instantly.
     
  14. plaYer2k Master Engineer

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    Well it is very important to know about the "sudden gravity effect".

    Firstly we could go down to how you percept force and motion, mostly using http://en.wikipedia.org/wiki/Vestibular_system where most of the informations come from but also from other systems like liquid pressure when suddenly you are accelerated (through a push/pull) into one direction and liquids like blood, digestive juice of even your nicely "floating brain". Sure the later ones commonly arent percepted consciously but still affect your overall perception.
    So the effect usually is based on relative movements due to inerta like the already mentioned liquids aswell as Stereocilia. So once an external force is applied to you, your body physically reactos to it by getting pushed/pulled accordingly, however Stereocilia and liquids stay in motion as they have been before (inertia) because the force is not directly applied to them. That generates the perception of acceleration/motion. (Sure there are other ways of perception like visual or acoustic but that is irrelevant in an enclosed ship)

    So, the question is how such a gravity field gets applied to you now. Will you move into it with a very hard border from 0G to 100G? That would be like hitting a hard wall. Parts of your body would be affected by the gravity and either pulling of pushing it for or against the rest of the body which is in motion. Iam not a doctor but that could be fatal, like if it were applying to your head/neck, it would most likely break it *snap*. So the same effect as in a jet where you get pushed around from an external body, just that the "external body" here is the part of your body that is affected by the gravity already.
    Since your sensory organs are within your body and not at the outside (luckily) you would feel such a change for sure.

    However if the gravity effect suddenly applies to your whole body - think like you are completely within the Gravity Generators volumina as it triggers - you would feel absolutely nothing. Every atom of your body would be accelerated so that you can not notice any difference at all. All liquids and Stereocilia are accelerated equally.


    So yeah, it boilds down to how you apply the gravity ... i daresay :3
     
  15. NutterChap Apprentice Engineer

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    That, and whether you make contact with anything else that has a different speed or direction.

    Luckily, all gravity in nature is gradual: it is a bit like sound, in that its intensity is the highest at around the source, and gets weaker the further away you are from the source. Gravity generators in SE do seem to have a hard line of the generated gravity field, which may indeed cause some discomforts. entering such a field is never 'all of a sudden', as one part of your body always enters first. This will result in shear forces in the subject: a bit like cutting paper. Being in the gravity field completely when it is turned on, and you experience nothing in particular as stated by Player2k.

    TL;DR:
    You do not notice the gravity field unless:
    -you enter it AND the gravity field has a sudden 'border'
    -you make contact with something that does not have the same speed or direction of travel that you have

    Black holes are said to have such a fierce gravity around them that they actually 'suck up' light. Some scientists believe that this event horizon, past no light can return, will have effects on the human body. The person unlucky enough to get in there is believed to get stretched thin like a piece of spaghetti, due to the extreme ramp-up of gravity. So on a side note: would a black hole be a funny addition to SE? :p
     
  16. Cronos988 Junior Engineer

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    Funnily enough, apparently one major problem of current physics is the fact that, according to general relativity, you should not notice anything when you pass the "event horizon" (the point after which nothing, not even light, can escape the black hole) - just free fall. That is, I assume, as long as you are packed together tight enough to not experience shearing forces. However, a different approach (may have been quantum physics) states that there is a "firewall" at the event horizon, consisting of high energy particles, which scrambles any information passing through. In case of an astronaut, being scrambled means, well, about the same thing it means for eggs, really. Completely off topic, but yeah, gravity.
     
  17. NutterChap Apprentice Engineer

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    Indeed, the 'not noticing anything at all' idea and the 'scrambling firewall of death' idea. In either case, sending something out there to find out what's what will never yield any results. The gravity well of the black hole sucks in the electromagnetic waves carrying the communication from the probe, it sucks in the probe and, it sucks in all hope to ever finding out. :(
     
  18. Savage117 Trainee Engineer

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    [SIZE= 10pt]I'm not a physicist nor am I a scientist so correct me if I'm wrong here. But wouldn't a sufficiently powerful gravitation force of any type produce shearing forces? Due to the fact (I think) that all gravitational forces have a point they come from, and at that point they are at their most powerful. For example at the Earth’s core you would experience an increase in gravitational pull, from what you would experience on the surface, assuming you could survive such an environment. I don't think there is such a thing as a bordered gravity field in nature, I believe the pull gets gradually stronger as you near the point of origin, so that would mean the part of an object closer to the origin is experiencing more force than the part most distant from it. [/SIZE]So wouldn't that mean we would feel it whether we were inside it when it was turned on or outside it and passing into it while it was on? [SIZE= 10pt]

    Also, since objects accelerate dependent on their mass, a more massive object would accelerate slower than a less massive one when exposed to this hypothetical gravity field. So if you were standing on a very massive object, a ship for instance, and the field was turned on around you, would you not be squished into the deck of that ship, even though the gravity field is also affecting the ship? This is all assuming you, and the ship, are completely immobile in relation to the gravity field generator.[/SIZE]
     
  19. MotoRider42HC Apprentice Engineer

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    Gravity on earth is 9.8m/s/s, which by definition, is acceleration.

    Acceleration is distance/time/time

    All gravity forces are acceleration forces
     
  20. MotoRider42HC Apprentice Engineer

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    thats not true at all. gravity is acceleration. you would "feel" the acceleration no matter what.
     
  21. plaYer2k Master Engineer

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    Well, to "back" what i already said, you do not feel the gravity unless it is a "hard border" or any other physical body is blocking your path and you are no longer in free fall. Which is how i understood the OP. If you had a spaceship, it would be in sudden free fall aswell.

    http://physics.stackexchange.com/questions/46020/do-you-feel-gravity

    On the matter how well we could withstand other forces (getting pushed around with a spaceship/plane/car, high gravity on a celestial bodies surface) this might be an interesting read for some http://www.pbs.org/wgbh/nova/space/gravity-forces.html

    is that how you "american english" people write those formulas? i would go for m/s² which looks less messy.

    I wonder how you read there that gravity is not acceleration and how you can make such a claim..
    Anyway, read above. He gave a pretty short and accurate answer.

    In addition, i dont see why it is needed to make all these doubleposts or even quadrupleposts.
     
  22. extraammo Senior Engineer

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    The only way you feel something is if different parts of your body move at different speeds. If your entire body is being accelerated at the same rate, you will not feel it since it is every atom in your whole body changing speed the same amount exactly.
     
  23. xwhitemousex Apprentice Engineer

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  24. mastpayne Senior Engineer

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    Actually....if you could survive it, of course, at the Earth's core you would basically be in free-fall...no gravity in a sense, because all around you (equally) would be the mass creating the gravity.

    You would be in the center - experiencing a gravitational pull equally from all directions.

    You would float.
     
  25. Bad_Idea Apprentice Engineer

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    And then be crushed as well as incinerated by extreme pressure/heat...
     
  26. plaYer2k Master Engineer

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    If the pressure is high enough ... sure. However the OPs question didnt suggest that you were close to the gravities origin.
     
  27. Bad_Idea Apprentice Engineer

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    In this case i am not referring to the original post, as you might see i have quoted another poster.
     
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