5 ms·

Thanks for editing out your suggestion for me to "read a high-school physics textbook." The earth is the frame of reference when considering free body diagrams

by bronz 11y ago

Thanks for editing out your suggestion for me to "read a high-school physics textbook." The earth is the frame of reference when considering free body diagrams of objects moving around on its surface for all practical purposes. Neither the treadmill nor the person using the treadmill moves with respect to the earth and therefore no bodily acceleration is experienced by the user. In the virtual world, however, the user does move and bodily acceleration is expected. Therefore, a treadmill cannot alleviate the problems caused by acceleration mismatching.

shamino 11y ago
Thanks for taking the time to reply to my comment - I still don't understand your point. It's as if you're saying, "because the treadmill (or you) don't move with respect to the ground, you don't experience movement." If this were the case, you wouldn't be able to exercise on a treadmill since no energy would be spent (Energy = Force * distance), where distance would be 0 in your argument. I think the difference here is that the treadmill moves you, vs you moving yourself. Even still, there are machines that can move using the friction between your feet and the treadmill surface - and they are starting to make their way into some of the local 24-hour gyms. I'm not arguing with your point that "VR will flounder", but I just want to keep everything honest. And honestly, your physics doesn't check out.
- bronz 11y ago
  Yes, this is only about physics for me too. My physics does check out though. If you are in a car and it accelerates from 0 to 30 mph you will experience the symptoms of acceleration. For example, an object that is hanging from a string in your frame of reference, such as a fuzzy dice hanging from the mirror, will appear to move backwards on its own. Try holding the fuzzy dice while running on a treadmill. I guarantee you won't see anything like that happen. Because you are not accelerating.
  - shamino 11y ago
    In your argument, your string and fuzzy die are not measured with respect to the surface of the treadmill, which is the frame-of-reference you should be considering. If you think of it this way, then yes, your fuzzy die will "lean forward". You absolutely do experience acceleration when you're on the treadmill, how do you think you go from 0 mph to 5 mph ? With respect to the ground of the earth, then there is no acceleration horizontally. With respect to the surface of the treadmill (which is what you must now consider), then yes. Just think of exercise. I challenge you to run 100 miles on the treadmill and not get tired.
    - ADSSDA 11y ago
      I don't think you understand the arguments people are making. Your inner ear does not experience any acceleration in your example, which is what is required to avoid sickness. What's happening relative to the surface of the treadmill doesn't matter, the acceleration of your inner ear does, and that's not changing.
      - shamino 11y ago
        How does my inner ear know I'm accelerating on the treadmill or the ground ? What if I blindfolded myself ? The treadmill is just like the ground, for all intents and purposes.
        ADSSDA 11y ago
        Is your head accelerating while you're on the treadmill? I've never seen a treadmill where that happens, the whole idea of a treadmill is running in-place. The most common VR treadmill-ish device I'm aware of is the Virtuix Omni: http://www.virtuix.com/ http://www.virtuix.com/, where your head is clearly not accelerating. What are you picturing when you claim your head (and hence inner ear) is accelerating on a treadmill?
        shamino 11y ago
        I'm starting to understand yours and everyone replies. I think what I had in mind is that I'm accelerating relative to a point on the treadmill, and therefore my entire body is accelerating. I can't wrap my head around the fact that we're still considering the ground as the frame of reference. I know that the treadmill moves on its own, but what if I push the surface of the treadmill to make me move forward. Wouldn't I not know the difference between a sidewalk and the treadmill ?
- deleted 11y ago
  [deleted]
- phinnaeus 11y ago
  1) Start running on a treadmill 2) Jump directly sideways off of the treadmill 3) Experience 0 acceleration because your velocity parallel to the treadmill is basically 0. Note, I think treadmills can work for VR, I'm just here for the physics. Also, for my third edit, upon re-reading all the comments in this chain, it really seems like we're all agreeing. Just talking about different effects.
  - shamino 11y ago
    This is the same misunderstanding that many people are having. Your frame of reference while on the treadmill should be the surface of the treadmill. Once you jumped off, you switched your frame of reference to the ground of the earth. Keep your reference on the surface of the treadmill, and you'll see you've experienced negative acceleration. This is why you always get an "extra boost" when you come off the escalator.
    - Jack000 11y ago
      you can only do this if the surface of the treadmill is an inertial reference frame. ie. a person running at constant speed vs a person on a treadmill at constant speed is functionally equivalent. However, the moment you want to stop or change speed this no longer works - in the real world your body needs to accelerate, while on the treadmill the treadmill accelerates and your body does not. This is because the ground remains an inertial reference frame during the acceleration, while the treadmill surface does not.
    - deleted 11y ago
      [deleted]
- modoc 11y ago
  The point is that for your inner ear, there is no acceleration when running, or not, on a treadmill. Your body isn't moving relatives to where it started, so your inner ear doesn't detect the same equilibrium changes that would align with your visual perception - https://en.wikipedia.org/wiki/Inner_ear#Equilibrium https://en.wikipedia.org/wiki/Inner_ear#Equilibrium
  - shamino 11y ago
    See my replies to the rest of the comments. The point is, you have to use the surface of the treadmill as your frame of reference. Then, it's obvious that your body has moved relative to where it started.
  - shamino 11y ago
    Sorry, you're right. After reviewing your comments and debating long with my best friend (what are best friends for, anyways), I finally see my flaw. I didn't consider the inner ear not accelerating whether or not the treadmill below you does. everyone who has tried to set me straight.

by bronz 11y ago

shamino 11y ago

Thanks for taking the time to reply to my comment - I still don't understand your point. It's as if you're saying, "because the treadmill (or you) don't move with respect to the ground, you don't experience movement." If this were the case, you wouldn't be able to exercise on a treadmill since no energy would be spent (Energy = Force * distance), where distance would be 0 in your argument. I think the difference here is that the treadmill moves you, vs you moving yourself. Even still, there are machines that can move using the friction between your feet and the treadmill surface - and they are starting to make their way into some of the local 24-hour gyms. I'm not arguing with your point that "VR will flounder", but I just want to keep everything honest. And honestly, your physics doesn't check out.

bronz 11y ago
Yes, this is only about physics for me too. My physics does check out though. If you are in a car and it accelerates from 0 to 30 mph you will experience the symptoms of acceleration. For example, an object that is hanging from a string in your frame of reference, such as a fuzzy dice hanging from the mirror, will appear to move backwards on its own. Try holding the fuzzy dice while running on a treadmill. I guarantee you won't see anything like that happen. Because you are not accelerating.
- shamino 11y ago
  In your argument, your string and fuzzy die are not measured with respect to the surface of the treadmill, which is the frame-of-reference you should be considering. If you think of it this way, then yes, your fuzzy die will "lean forward". You absolutely do experience acceleration when you're on the treadmill, how do you think you go from 0 mph to 5 mph ? With respect to the ground of the earth, then there is no acceleration horizontally. With respect to the surface of the treadmill (which is what you must now consider), then yes. Just think of exercise. I challenge you to run 100 miles on the treadmill and not get tired.
  - ADSSDA 11y ago
    I don't think you understand the arguments people are making. Your inner ear does not experience any acceleration in your example, which is what is required to avoid sickness. What's happening relative to the surface of the treadmill doesn't matter, the acceleration of your inner ear does, and that's not changing.
    - shamino 11y ago
      How does my inner ear know I'm accelerating on the treadmill or the ground ? What if I blindfolded myself ? The treadmill is just like the ground, for all intents and purposes.
      - ADSSDA 11y ago
        Is your head accelerating while you're on the treadmill? I've never seen a treadmill where that happens, the whole idea of a treadmill is running in-place. The most common VR treadmill-ish device I'm aware of is the Virtuix Omni: http://www.virtuix.com/ http://www.virtuix.com/, where your head is clearly not accelerating. What are you picturing when you claim your head (and hence inner ear) is accelerating on a treadmill?
        shamino 11y ago
        I'm starting to understand yours and everyone replies. I think what I had in mind is that I'm accelerating relative to a point on the treadmill, and therefore my entire body is accelerating. I can't wrap my head around the fact that we're still considering the ground as the frame of reference. I know that the treadmill moves on its own, but what if I push the surface of the treadmill to make me move forward. Wouldn't I not know the difference between a sidewalk and the treadmill ?
deleted 11y ago
[deleted]
phinnaeus 11y ago
1) Start running on a treadmill 2) Jump directly sideways off of the treadmill 3) Experience 0 acceleration because your velocity parallel to the treadmill is basically 0. Note, I think treadmills can work for VR, I'm just here for the physics. Also, for my third edit, upon re-reading all the comments in this chain, it really seems like we're all agreeing. Just talking about different effects.
- shamino 11y ago
  This is the same misunderstanding that many people are having. Your frame of reference while on the treadmill should be the surface of the treadmill. Once you jumped off, you switched your frame of reference to the ground of the earth. Keep your reference on the surface of the treadmill, and you'll see you've experienced negative acceleration. This is why you always get an "extra boost" when you come off the escalator.
  - Jack000 11y ago
    you can only do this if the surface of the treadmill is an inertial reference frame. ie. a person running at constant speed vs a person on a treadmill at constant speed is functionally equivalent. However, the moment you want to stop or change speed this no longer works - in the real world your body needs to accelerate, while on the treadmill the treadmill accelerates and your body does not. This is because the ground remains an inertial reference frame during the acceleration, while the treadmill surface does not.
  - deleted 11y ago
    [deleted]
modoc 11y ago
The point is that for your inner ear, there is no acceleration when running, or not, on a treadmill. Your body isn't moving relatives to where it started, so your inner ear doesn't detect the same equilibrium changes that would align with your visual perception - https://en.wikipedia.org/wiki/Inner_ear#Equilibrium https://en.wikipedia.org/wiki/Inner_ear#Equilibrium
- shamino 11y ago
  See my replies to the rest of the comments. The point is, you have to use the surface of the treadmill as your frame of reference. Then, it's obvious that your body has moved relative to where it started.
- shamino 11y ago
  Sorry, you're right. After reviewing your comments and debating long with my best friend (what are best friends for, anyways), I finally see my flaw. I didn't consider the inner ear not accelerating whether or not the treadmill below you does. everyone who has tried to set me straight.